Preliminary Safety Analysis of the Gorleben Salt Dome
BGE TECHNOLOGY GmbH's key activities focus... more Preliminary Safety Analysis of the Gorleben Salt Dome
BGE TECHNOLOGY GmbH's key activities focused on the following issues:
● design of 3 repository variants for the emplacement of HLW and spent fuel. All versions take into account the requirement of retrievability. As a further option, combined emplacement with LLW/ILW was analysed. ● Development of closure concepts for all variants and optimisation of the concepts based on the results of consequence analyses ● development of geotechnical barrier concepts and demonstration of the barrier's integrities ● development of a FEP cataloque ● development of reference and alternative scenarios for the different repository variants analysis of human intrusion scenarios
Technical Support for Conducting Studies in the Field of Radioactive Waste Management – Conceptual Design for Backfil Removal Equipment allowing Retrieval of Waste Packages
One of the problems currently investigated by ONDRAF/NIRAS in regard to waste disposal is the potential need to retrieve waste packages from the disposal galleries after these have already been backfilled. The objective of this study was to identify and conceptually design suitable technical equipment for the removal of the backfill material.
The study describes the necessary equipment with special regard to the expected boundary conditions: ● type of backfill material ● confined spaces and limited working area inside the disposal galleries ● irregular cross sections and backfill dimensions around the waste packages ● working conditions next to the waste packages (radiation, heat)
The study further covers a preliminary cost assessment for buying/developing the equipment and addresses the potential impact of the selected backfill removal equipment on the required minimum diameter of the disposal galleries.
Optimisation of the Direct Disposal Concept by Emplacing Spent Fuel Canisters in Boreholes (R&D Project DENKMAL)
Feasibility Study, Basic Design and Engineering Design of a Radioactive Waste Disposal Facility in Iraq
Technical Design and ISAR Preparation for National Disposal Facility in Bulgaria
Site-specific Evaluation of Safety Issues for High-level Waste Disposal in Crystalline Rock (R&D Project URSEL)
Development of Technical Concepts for the Retrieval of Waste Packages with Heat-generating Radioactive Waste and Spent Fuel from Repositories in Salt and Clay Formations – R&D Project ERNESTA
Long-term isolation of radioactive waste in deep geological repositories mainly relies on the ret... more Long-term isolation of radioactive waste in deep geological repositories mainly relies on the retention properties of the host rock. Therefore, the impairment of the host rock must be minimized and existing pathways must be sealed. For sealing of rock fractures, sodium silicate solutions (water or liquid glass) are a commonly used grout. The applicability and efficiency of fracture sealing using water glass was investigated in the course of an R&D project. Field experiences have shown that the permeability of damaged rock salt can be reduced by water glass injection. The sealing effect is a result of the formation of insoluble amorphous silica and other long-term stable minerals due to the chemical reactions with the soluble salts of the host rock as well as salt solutions.
The precipitation of dissolved trace elements in water glass is relevant with regard to the migration of toxic or radioactive elements as trace constituents. This process was analyzed by laboratory tests using brine with barium (Ba), cobalt (Co), iron (Fe), nickel (Ni), and strontium (Sr). The visual observations are comparable to those obtained from well-known crystal or chemical garden experiments, where chemical gardens result from the precipitation reactions generated by adding crystals of a soluble heavy metal salt to aqueous solutions of sodium or potassium silicate. In particular, chemical analyses demonstrate a removal of small divalent ions (Co, Ni) as well as a significant decrease in the UO2 concentration. The precipitates can comprise insoluble salts, as well as hydroxides and silicate phases. Another well-known and in water treatment frequently used property of amorphous silicates is their high sorption capacity.
The Belgian radioactive waste management agency ONDRAF-NIRAS plans to dispose of long-lived and h... more The Belgian radioactive waste management agency ONDRAF-NIRAS plans to dispose of long-lived and high-level radioactive waste in galleries of an underground repository constructed in clay. For stabilization purposes the disposal concept provides a concrete backfilling of the disposal galleries. Plans call for mixing the concrete in above ground facilities and pumping it through the shaft and drifts into the galleries. Upon hardening the backfill will guarantee a corrosion-retarding environment and reduce the mobilization of radionuclide complexes. To avoid an impairment of the gallery walls swelling of concrete must be limited. In addition, the backfill should contribute to the dissipation of the decay heat of the radioactive waste and – according to appropriate legal requirements – its strength must be low enough to enable the retrieval of the waste packages. DBE TECHNOLOGY GmbH was contracted to develop a suitable backfill material and to demonstrate the feasibility of the backfill process. Laboratory tests were carried out including investigations on the pumpability and the flow or spreading behavior of the mixture. Examinations of pore solutions were performed to evaluate the chemical environment with regard to corrosion limitation. Thermal parameters of the backfill material were determined, which will be used as input parameters for future numerical thermal calculations. Mock-up tests were performed to investigate the flow behavior of the grout in 2 m long Plexiglas tubes, which were designed to simulate a section of the disposal galleries. The pump pressure and the pressure in the pipeline were registered in order to develop the design of the backfill system.
ONDRAF/NIRAS, the Belgian Agency for Radioactive Waste and Enriched Fissile Material, proposed ge... more ONDRAF/NIRAS, the Belgian Agency for Radioactive Waste and Enriched Fissile Material, proposed geological disposal in poorly indurated clay as the reference solution for the long-term management of high-level and/or long-lived radioactive waste in Belgium. ONDRAF/NIRAS is currently preparing a safety and feasibility case (SFC), which will describe, substantiate and, as far as possible, quantify the safety and feasibility of the proposed disposal system.
DBE TECHNOLOGY GmbH was commissioned to support ONDRAF/NIRAS by carrying out feasibility studies in regard to the future operation of such a repository. The studies focus on essential parts of the conceptual repository design that need further development and confirmation of technical feasibility, on the demonstration of compliance with safety requirements, and on a cost evaluation. The feasibility studies for a hoisting system for payloads of up to 80 tons, for underground transport and waste emplacement systems, and for repository ventilation have been completed. All systems for transport and ventilation are based on state-of-the-art equipment. The shaft transport system is based on components that have been built and tested at full scale during R&D work carried out by DBE in connection with the German repository projects at Gorleben and Konrad. As a result of the analyses conducted as part of the feasibility studies, several recommendations for optimizations of the original design basis were formulated. In all cases, systems with proven technical feasibility could be designed, which also complied with the requirement for safe and cost effective technical implementation.
According to the Belgian disposal concept, low- and intermediate-level waste will be conditioned ... more According to the Belgian disposal concept, low- and intermediate-level waste will be conditioned in concrete monoliths and high-level waste in so-called supercontainers. In the disposal galleries of the Belgian disposal facility, a trench as roadway and lateral surfaces for laying down the waste packages are provided. The system allows the reversal of the process and the safe return transport of emplaced monoliths and supercontainers until the voids will be backfilled. Thereafter, a sickle-shaped backfill body exists around the upper part of the waste packages and the filled trench of the gallery floor.
Retrieval requires the establishment of safe work conditions and the removal of the narrow backfill bodies over a range of about 3 m (monoliths) to more than 6 m (supercontainers). Thus, a study was carried out to identify a suitable state-of-the- art technology. Initially, techniques commonly used in the building and mining industry were compiled and grouped according to their kind of impact on the backfill. Within the scope of a benefit analysis, a catalogue of evaluation criteria was used to develop a ranking of the techniques. For example, criteria related to the space requirements of the machines and their tools, their potential to damage the waste packages and the surrounding structures, and the removability and amount of the residues. For reasons of workers’ safety, cable-and remote-control-systems are favoured. Milling is a preferred option. Based on these findings, a basic concept for waste package retrieval was developed. Using the specified technologies and procedures, the operational safety and the technical realization of waste retrieval can be assured.
Methods for conditioning liquid and dry radioactive waste can be its immobilization, solidificati... more Methods for conditioning liquid and dry radioactive waste can be its immobilization, solidification or encapsulation by means of cement mixtures. Considering the availability and quality of the raw materials, the requirements of the regulatory framework, and the specific conditions of the waste disposal cycle, a range of mixtures of cements, reactive additives, and fillers can be used. In the last decades, the percentage of products containing latent hydraulic, pozzolanic or limestone filler has steadily increased. Moreover, innovative products have been developed, such as super-plasticisers, to allow the largescale application of ultrahigh performance and self-compacting concrete. This progress influenced the revision and the definition of standards. NDA contracted DBE TECHNOLOGY GmbH as part of a consortium led by EDEN Nuclear and Environment, UK, with a multiphase study to analyze the development in the building sector and the availability of suitable cement compositions for encapsulation purposes. The aim of the first phase of the study is to gain an overview of the practice. Then, the requirements on the cement compositions are to be summarized, taking into account the different disposal strategies in the European countries. The scope and characteristics of the quality assurance programs and the approaches in case of an occurrence of non-conformities are reviewed as well. The aim is to make it possible to identify the need of material optimization and to guarantee a future availability of adequate high-quality cement compositions.
To optimize or restore the barrier function of different host rocks or backfill materials, BGE TE... more To optimize or restore the barrier function of different host rocks or backfill materials, BGE TECHNOLOGY GmbH developed injection materials and grouting techniques to seal any cavities in rocks or backfill materials. In order to stabilize the rock and backfill bodies and to seal cracks, fractures, or pores, suspensions and particle-free injection materials are applied. In saline environments, the particle-containing grouts are based on magnesium oxide. In non-saline areas, mixtures with classic cements as well as reactive and nonreactive fillers are used. Beyond a certain size, particles cannot penetrate into small fractures or pores, which are potential pathways for fluids. As a result, the range of use of these grouts is limited, and water glass is used to seal finer flow paths. However, experience has shown that the penetration of particles can be improved if water glass is injected first and the grouts are injected immediately afterwards. This effect can be explained by a lubrication of solid surfaces and the effect that water glass dissolves salts before gelation and hardening can start. This finding suggests combining water glass, as carrier fluid, with reactive additives. The development work led to novel grout families that also have many other benefits. At elevated injection pressures, the water glass and non-inert solutions are squeezed out of the mixtures, which themselves act as an independent injection agent. This way, it is possible to fill or seal fractures and pore systems of very different sizes in one injection step for the very first time.
Wassergläser sind alkalische Lösungen eines Alkalioxids und von Siliciumdioxid. Aufgrund ihres Wa... more Wassergläser sind alkalische Lösungen eines Alkalioxids und von Siliciumdioxid. Aufgrund ihres Wassergehaltes lösen sie Salze. Die Folge ist das Gelieren der Wassergläser. Es bilden sich Silikate sowie Minerale, deren Zusammensetzung vom Typ des Alkalioxids (Na2O, K2O, Li2O) und dem Stoff¬bestand der Salze abhängig ist. Die Fällungsprodukte verstopfen Risse und Poren und verbinden Rissflanken. Aufgrund der abdichtenden und verfestigenden Wirkung werden Salzgesteine sowie salzhaltige Baustoffe und Versatzstoffe mit Wassergläsern, insbesondere Natron-Wassergläsern injiziert.
Das Lösen der Salze erweitert zunächst geringfügig die Hohlräume. Zudem hat das Wasserglas eine Schmierwirkung. Hierdurch können dem Wasserglas nachströ¬mende Suspensionen in Risse und Poren eindringen, die ohne den Einsatz des Wasserglases nicht für die Suspensionspartikel zugänglich wären. In diesem Fall würden bei üblichen partikelgestützen Injektionsmitteln die Riss- oder Poreneingänge verstopfen und Wasser oder allgemein Baustofflösung in die feineren Wegsamkeiten eindringen. Da die Lösungen dieser Baustoffe, im Gegensatz zu den Wassergläsern keine Eigenerhärtung aufweisen, wird keine abdichtende Wirkung erzielt. Zudem kann die Füllung der feinen Wegsamkeiten mit Baustofflösung problematisch im Hinblick auf den Erfolg weiterer Injektionen sein.
Die vorteilhaften Eigenschaften des Wasserglases wurden genutzt, um partikelgestützte Injektionsmittel ohne die aufgeführten Nachteile herkömmlicher Baustoffe zu entwickeln. Geopolymere belegen, dass Puzzolane und hydraulisch-erhärtende Stoffe, wie die Aluminosilikate Metakaolin und Flugasche in Wasserglas suspendierbar sind und mit diesen zu Festkörpern reagieren. Es zeigte sich, dass auch ma¬gnesiumhaltige Stoffe, wie Magnesiumoxid und Magnesiumhydroxid sowie der extrem feine Silikastaub zur Herstellung von Wasserglas-Suspensionen geeignet sind. Zahlreiche dieser Stoffe sind mit unterschiedlicher Korngröße erhältlich. Da zudem Wassergläser über eine weite Spanne der Fließfähigkeit angeboten werden und ebenso inerte Zusatzstoffe eingesetzt werden können, bietet sich die Möglichkeit die entwickelten Baustoffe an eine Vielzahl von Aufgabenstellungen anzupassen. Die Suspensionen erlauben es größere und feine Wegsamkeiten in einem Zuge zu injizieren und sind bei Bedarf mit klassischen Injektionsmitteln auf Zementbasis, Magnesiabindern und reinen Wasserglaslösungen kombinierbar.
Zementhaltige Baustoffe enthalten alkalische Lösungen. Werden diese Lösungen verdrängt und/oder d... more Zementhaltige Baustoffe enthalten alkalische Lösungen. Werden diese Lösungen verdrängt und/oder diffundieren die Hydroxid-Ionen, können sie mit angrenzenden Materialien reagieren. Die Prozesse sind im Endlagerbergbau relevant, da sie die Permeabilität von Tonen erhöhen, deren Sorptionsvermögen senken und die Funktion von Tonbarrieren beeinträchtigen. Metallen können dagegen passivieren. Die Schutzschichten reduzieren oder verhindern die Korrosion der Metalle und Endlagerbehälter und begrenzen die entstehende Gasmenge, die zu einem Druckaufbau und Phasenfluss führen könnte. Für einen zielgerichteten Einsatz sind daher Baustoffe unterschiedlichen pH-Milieus zu entwickeln und einzusetzen.
Standardbaustoffe haben einen hohen pH-Wert, da Portlandzementklinker Hydroxide bilden. Der pH-Wert kann in Folge von Reaktionen mit Baustoffbestandteilen oder extern zugeführten Stoffen sinken. Hoch-pH-Baustoffe haben ein hohes Widerstandspotential gegen diese pH-Wert-Abnahme. Sie enthalten vor allem Portlandzemente und feste Hydroxide, wie Calciumhydroxid. Die Endfes¬tigkeit wird meist zügig erreicht und eindeutig vom Wasser-Zement-Wert beeinflusst. Wasserglas und Natronlauge wird allgemein eine beschleunigende Wirkung zugeschrieben. Untersuchungen ergaben, dass begrenzte Mengen dem Baustoff zugegeben werden können ohne die hydraulische Förderbarkeit und damit die Eignung als Verfüllmaterial einzuschränken.
Da Zemente stets Portlandzementklinker enthalten, muss zur Gewährleistung niedriger pH-Werte der Klinkeranteil gesenkt werden. Zudem müssen entstehende Hydroxide gebunden werden, beispielsweise durch Reaktionen mit Puzzolanen und latent-hydraulische Stoffen. Die re¬aktiven Stoffe können bereits ein Bestandteil des Zements sein (z. B. Sonder- oder VLH-Zemente nach EN 14216) oder separat zugegeben werden. Reaktive Stoffe haben spezifische Kapazitäten den pH-Wert zu senken, so dass der pH-Wert des Baustoffs eingestellt werden kann. Untersuchungen ergaben, dass silikastaubhaltige Mischungen im Vergleich zu Standardbaustoffen deutlich länger erhärten. Es bildeten sich trotz äußerst hoher Wasser-Zement-Werte homogene Festkörper. Die Be¬funde sind darauf zurückzuführen, dass Silikastaub maßgeblich am Aufbau des Bin¬demittelgerüsts und am Festigkeitsgewinn beteiligt ist. Der Reaktionsumsatz war höher als nach dem k-Wert-Konzept der zementäquivalenten Wirksamkeit (DIN EN 206) zu erwarten ist. Der pH-Werte der Porenlösung konnte auf etwa 9,3 gesenkt werden.
According to the classic approach, fissure or pore systems in solid rock or backfill are to be in... more According to the classic approach, fissure or pore systems in solid rock or backfill are to be injected with particle-laden, and thereafter particle-free material when a high level of impermeability is required. The suspensions used in the salt and potash mining industries are usually in the form of magnesia binders. Waterglass is also frequently employed as a particle-free injection medium because of its capacity to react with salts and saline solutions to form a solid. Waterglass reacts with magnesium oxide (MgO) and many other substances containing magnesium. This served as a basis for developing a new type of injection medium. Unlike magnesia binders these mixtures move out along their flow paths and force waterglass, rather than an inert solution, into the adjoining areas. The lubricating effect of the waterglass improves the capacity of the particles to penetrate the cavities. This increases the degree to which the voids are filled with reactive material and the number of injections can potentially be reduced as a result. The mixtures can be combined with magnesia binders and pure waterglass and this serves to enhance the available range of injection media.
Nach der klassischen Vorgehensweise sind Riss- oder Porensysteme eines Gesteins oder Versatzes mit partikel-haltigen und danach partikelfreien Baustoffen zu injizieren, wenn eine hohe Dichtigkeit gefordert wird. Im Kali- und Steinsalzbergbau sind die Suspensionen meist Magnesia¬binder. Aufgrund der Fähigkeit mit Salzen und Salzlösungen zu Feststoffe zu reagieren, werden häufig als partikelfreie Injektionsmittel Wassergläser eingesetzt. Wassergläser reagieren auch mit Magnesiumoxid (MgO) und vielen weiteren magnesiumhaltigen Stoffen. Dies war die Grundlage einen neuen Typ von Injektionsmitteln zu entwickeln. Bei diesen Mischungen wird im Gegensatz zu Magnesiabindern ausgehend von ihren Strömungswegen keine inerte Lösung, sondern Wasserglas in die angrenzenden Bereiche abgepresst. Eine Schmierwirkung des Wasserglases verbessert das Eindring-vermögen der Partikel in Hohlräume. Durch diese Effekte steigt das Ausmaß der Hohlraumauffüllung mit reaktivem Material und es ergibt sich die Möglichkeit die Anzahl der Injektionen zu reduzieren. Die Mischungen sind mit Magnesiabindern und reinen Wassergläsern kombinierbar und bereichern damit die Palette an Injektionsmitteln.
Der Einsatz von Focus-Stacking bei der Untersuchung von Flüssigkeitseinschlüssen im Steinsalz
Mik... more Der Einsatz von Focus-Stacking bei der Untersuchung von Flüssigkeitseinschlüssen im Steinsalz Mikroskopisch kleine Flüssigkeitseinschlüsse erlauben Rück¬schlüsse zur Entste¬hung und Geschichte eines Gesteins. Um Aussagen über ihre Entstehung treffen zu können, sind zuerst die Anordnung der Einschlüsse, ihre Form, die Art und Menge von Mi¬neralbestandteilen und die Größe von Gasblasen auszuwerten. Hohe Vergrößerun¬gen reduzieren die Schärfentiefe des Abbildes, so dass Details der Einschlüsse nur in einer Schnittebene erkennbar sind und die Un¬tersuchungen erschwert werden. Das Verfahren des Focus-Stackings kann in diesen Fällen hilfreich sein, da es digi¬tale Daten von Fotos, deren Schärfe¬tiefebereiche sich über¬schneiden, miteinander verrechnet. Praxistests, die an Dünnschliffen von Steinsal¬zen durchge¬führt wurden, zeigen, dass das Verfahren Bilder hoher Qualität erzeugt. Die ge¬wünschten Proben¬bereiche werden scharf dargestellt. Ein Nachteil des Ver¬fahren könnte jedoch die Zeitdauer der Rechen¬operationen sein. Zur Minimierung des Zeitaufwan¬des sollten daher Erfahrun¬gen zur Auswahl des Fotomaterials und zum Einfluss der auswähl¬baren Rechenme¬thoden auf das Stackresultat vorliegen. Für Präsenta¬tionen kann zu¬dem mit einer speziellen Software eine Bildnachbear¬beitung erfor¬derlich sein, um Artefakte der Stack-¬Berechnung und Bildfehler, die aus dem opti¬schen System resultieren, zu entfernen.
The application of the focus-stacking-technique for the examination of fluid inclusions in rocksalt It is possible to draw conclusions from microcopically small fluid inclusions about the genesis and history of a rock. For an assessment, it is necessary to gather information about the arrangement of the inclusi¬ons, their shapes, the types and amounts of mineral components, and the size of gas bubbles. High magnifications reduce the depth of field of an image so that details of the inclusions are limited to a plane cutting through the inclusi¬ons, which mades the investigations diffi¬cult. In this case, focus stacking, also known as focal plane merging, can be a helpful technique. It proces¬ses the digital data of images with overlapping depths of fields. Practical tests, carried out on thin section of rock salt show that this technique generates high-quality-images. The desired areas of the samples are displayed in sharp focus. One drawback of this technique could be the long processing periods. Experience concerning the selection of the photographic material and the influence of the processing methods on the stack results helps to minimize the time needed. If the images are to be used for presentation pur¬poses, it can be ne¬cessary to erase artifacts of the stack-processing and to corrigate image errors, which result from the optical system, by means of a special photo finishing software.
Schlüsselwörter: Berechnungsartefakte, Bildbearbeitung, Bildqualität, Mikroskopie, Schärfentiefe, Stapeltechnik, Zeitaufwand Keywords: Artifacts, computing time, depth of field, digital image processing, focal plane merging, focal point, focus blending, image quality, microscopy, sharpness
In Belgium, it is planned to dispose of long-lived and high-level waste in an underground facilit... more In Belgium, it is planned to dispose of long-lived and high-level waste in an underground facility. After disposal of the waste, the galleries will be back¬filled to provide stability to the galleries and to limit the amount of voids in the repository. To achieve those goals, the backfill material has to have a good flowability, a negligible bleeding, and a limited shrinkage. A limited grain size is also required to allow the injection of the backfill material. Despite the fact that the backfill supports the gallery lining, its strength must be low enough to enable the retrieval of the waste packages. The backfill material has to be chemically compatible with the Boom Clay and the waste packages. This means that it should not unduly perturb the clay or disposal packages. The thermal conductivity of the backfill material in the galleries containing high-level and thus heat-generating waste must be high enough to allow sufficient dissipation of the decay heat into the surrounding clay.
Based on these objectives, material requirements were specified and the development of a backfill mixture was carried out. Initially, the mix composition was optimized in the laboratory. Thereafter, the backfill process of a gallery section was simulated. The investigations illustrate that this mixture can be transported via pipelines through the shaft and drifts and would fill completely the backfill sections in the galleries. Measurements of the porosity, the pore solution composition, the thermal material properties, and the strength illustrate the compliances with the requirements and the feasibility of backfilling the disposal galleries. ---- The Belgian National Agency for Radioactive Waste and enriched Fissile Material ONDRAF/NIRAS is studying the disposal of low and medium activity level, long-lived waste (category B) and high activity, heat-generating waste (category C) in an underground facility. The repository is built at a reference depth of approximately 230 m in the Boom Clay host rock. Two shafts are built for personnel and material transfer and to provide ventilation during the construction and operation of the repository. A third shaft will be constructed for the waste transport. The shafts are connected via horizontal access galleries. The disposal galleries are constructed perpendicular to the access galleries. They are blind or dead-end galleries with a diameter of approx. 3.0 m and a length of 1,000 m. Fig. 1 shows an overview of the repository layout. The galleries in the clay will be lined with concrete wedge blocks. In the order to transport and to support the waste packages after disposal, the galleries are outfitted with a concrete floor. It is planned to backfill the galleries section by section with a cement-based material, because grout injection is assumed to offer better opportunities for achieving the industrial performance that is required to backfill such volumes in a relatively short period of time. The current planning assumes a volume of the sections of approximately 85 m³, which will be backfilled in three and a half hours. Seals will be placed at the front-end of the disposal galleries.
The main functions of the backfill mortar are (1) isolating the waste by forming an extra barrier to the waste, (2) providing the galleries with stability and thus avoiding a gallery collapse and (3) reducing the voids in the repository which is a regulatory requirement.
As the backfill needs to realize a high filling degree, it has to show good flowability, negligible bleeding, and limited shrinkage. The grain size is limited to allow the injection of the backfill material. Another important requirement for the backfill follows from the potential requirement for waste retrievability. This means that the strength of the backfill has to be sufficient low so that the backfill can be removed at a later stage. In addition, a high porous backfill might be envisaged as it can provide a storage volume for gas generated in the repository and consequently limit the gas pressure build-up. This is in particular important for the category B waste for which the gas generation is expected to be more significant than for the category C waste. The backfill material has to be chemically compatible with the Boom Clay host formation and any other component of the disposal system like the gallery lining and the waste disposal packages. This means that it should not unduly perturb the clay or disposal packages. Finally, the thermal conductivity of the backfill material in the category C waste disposal galleries must be high enough to allow sufficient dissipation of the heat from the category C waste into the surrounding clay. Furthermore, it has to be thermally stable under the maximum temperature that will occur in the backfill material.
Within the preliminary safety analysis for the Gorleben site (VSG), a closure system was designed... more Within the preliminary safety analysis for the Gorleben site (VSG), a closure system was designed in order to complement the containment providing rock zone (CRZ) by sealing and backfilling measures. The design procedure as well as the technical proof of function was mainly performed according to standard procedures in civil engineering. In the context of VSG, rough individual technical proofs of several measures were carried out. Meanwhile, this gap has been closed by subsequent investigations. Altogether the results of all the individual technical proofs of function indicate that safe containment of radioactive waste is a realistic possibility at the Gorleben site. --- In summer 2010, the German Federal Government launched a preliminary safety analysis to assess whether the salt dome at Gorleben is suitable to host all heat-generating radioactive waste generated by German NPPs. A repository concept was developed that also included a closure system.
In the course of seawater evaporation, calcite, gypsum, halite and eventually potassium and magne... more In the course of seawater evaporation, calcite, gypsum, halite and eventually potassium and magnesium salts crystallize in accordance with solubility with water. This correlation can be used to separate the "white gold" halite from the other salts and to harvest the solar seasalt in ponds, if enough water evaporates due to dry winds. In the arid climate of Lanzarote, the Salinas de Janubio produced in there heyday about 10000 tons of table and pickling salt on an area of 45 hectares. In the ponds and in particular on the ramparts of the basaltic rock pebbles, which show honeycomb- or tafone-like weathering features, lawns of gypsum crystals grew. Most remarkable are crystals that embedded foreign particles along crystal planes during growth and that extended across several layers of crystal lawns. Obviously, the different crystal shapes, which are unusual for gypsum, and lawn structures result from changes of the weather and variations of the operating conditions of the ponds.
Bei der Evaporation von Meerwasser bilden sich entsprechend der Abfolge ihrer Löslichkeit Carbonat, Gips, Halit sowie kalium- und magnesiumhaltige Salze. Diese Gesetzmäßigkeit erlaubt es Halit als weißes Gold von den weiteren Salzen zu trennen und auf Salzfeldern zu "ernten", wenn durch trockene Winde ausreichende Mengen an Wasser verdunsten.
Die Verwendung von Referenzprobern ist im Bereich der Analytik ein wichtiges Kriterium zur Beurte... more Die Verwendung von Referenzprobern ist im Bereich der Analytik ein wichtiges Kriterium zur Beurteilung der Qualität quantitativer Analysen. Um den Verbrauch zertifizierter und teurer Referenzproben einzuschränken, werden in zunehmendem Maße von Laboratorien sogenannte "in-house standards" hergestellt. Hierbei kommt der Probebearbeitung eine besondere Bedeutung zu. So muss die Homogenität und Reinheit des Probematerials weitestgehend gewährleistet sein.
Die Durchführung quantitativer Analysen erfordert die Verwendung von Referenzmaterialien. Denn auch bei einer sehr guten Reproduzierbarkeit der Messdaten kann nicht auf deren Richtigkeit geschlossen werden. Der Stoffbestand von Referenzproben ist jedoch hinsichtlich der Richtigkeit bekannt und kann zur Überprüfung der Messresultate herangezogen werden. Da zertifizierte Referenzproben nur eine begrenzte Zeit und häufig in kleinen Mengen zur Verfügung stehen, ist es vorteilhaft interne Referenzproben, sogenannten "in-house standards" zu benutzen. Sie sollten aus dem gleichen Material wie die zu untersuchenden Proben bestehen und können ebenso zur Erarbeitung von Analysenverfahren eingesetzt werden.
In the course of seawater evaporation, calcite,
gypsum, halite and eventually potassium and
magne... more In the course of seawater evaporation, calcite, gypsum, halite and eventually potassium and magnesium salts crystallize in accordance with their solubility in water. This correlation can be used to separate the “white gold” halite from the other salts and to harvest the solar seasalt in ponds, if enough water evaporates due to dry winds. In the arid climate of Lanzarote, the Salinas de Janubio produced in their heyday about 10.000 tons of table and pickling salt on an area of 45 hectares. In the ponds and in particular on the ramparts made of basaltic rock pebbles, which show honeycomb- or tafone- like weathering features, lawns of gypsum crystals grew. Most remarkable are crystals that embedded foreign particles along crystal planes during growth and that extend across several layers of crystal lawns. Obviously, the different crystal shapes, which are unusual for gypsum, and lawn structures result from changes of the weather and variations of the operating conditions of the ponds.
Bei der Evaporation von Meerwasser bilden sich entsprechend der Abfolge ihrer Löslichkeit Carbonat, Gips, Halit sowie kalium- und magnesiumhaltige Salze. Diese Gesetzmäßigkeit erlaubt es Halit als weißes Gold von den weiteren Salzen zu trennen und auf Salzfeldern zu „ernten“, wenn durch trockene Winde ausreichende Mengen an Wasser verdunsten. Im Klima Lanzarotes wurden zu ihrer Blütezeit in der Salinas de Janubio auf einer Fläche von rund 44 Hektar jährlich etwa 10.000 Tonnen Speise- und Pökelsalz gewonnen. In den Becken und vor allem an ihren Wällen aus basaltischen Gesteinen, die tafoneartig verwittern, entstehen Kristallrasen von Gips. Auffallend sind vor allem Kristalle, die während ihres Wachstums Fremdpartikel einschlossen und über mehrere Lagen reichen. Die unterschiedlichen, für Gips auch ungewöhnlichen Kristallformen und Verwachsungen beruhen offensichtlich auf Änderungen der Witterung und der Betriebsweise der Salzbecken.
The investigation of transport processes of clays in the aquatic environment is important as many... more The investigation of transport processes of clays in the aquatic environment is important as many pollutants are adsorbed on the surface of fine-grained particles or clay-organic complexes. Suppliers are rivers draining industrial centers. The material is mixed with lithogenic grains characterized by geogenic background compositions. In the Wadden Sea tidal flats large amounts of fine size sediments are accumulated. Sources which must be taken into consideration are rivers (Elbe, Ems, Weser) and pleistocene deposits, eroded from the coast and seafloor. This study used mineral specific properties to determine the portion of the potential source materials on Wadden Sea tidal flat deposits and suspensions. The following features were measured (= 0.16), the samples of the tidal flats vary from 0.11 to 0.15, and the glacial sediments have the worst crystallinity (le0.11). K/Rb-ratios show a dominance of the fluviatile detritus (tidal flats ˜145, glacial deposits ˜170, fluviatile bedload ...
Preliminary Safety Analysis of the Gorleben Salt Dome
BGE TECHNOLOGY GmbH's key activities focus... more Preliminary Safety Analysis of the Gorleben Salt Dome
BGE TECHNOLOGY GmbH's key activities focused on the following issues:
● design of 3 repository variants for the emplacement of HLW and spent fuel. All versions take into account the requirement of retrievability. As a further option, combined emplacement with LLW/ILW was analysed. ● Development of closure concepts for all variants and optimisation of the concepts based on the results of consequence analyses ● development of geotechnical barrier concepts and demonstration of the barrier's integrities ● development of a FEP cataloque ● development of reference and alternative scenarios for the different repository variants analysis of human intrusion scenarios
Technical Support for Conducting Studies in the Field of Radioactive Waste Management – Conceptual Design for Backfil Removal Equipment allowing Retrieval of Waste Packages
One of the problems currently investigated by ONDRAF/NIRAS in regard to waste disposal is the potential need to retrieve waste packages from the disposal galleries after these have already been backfilled. The objective of this study was to identify and conceptually design suitable technical equipment for the removal of the backfill material.
The study describes the necessary equipment with special regard to the expected boundary conditions: ● type of backfill material ● confined spaces and limited working area inside the disposal galleries ● irregular cross sections and backfill dimensions around the waste packages ● working conditions next to the waste packages (radiation, heat)
The study further covers a preliminary cost assessment for buying/developing the equipment and addresses the potential impact of the selected backfill removal equipment on the required minimum diameter of the disposal galleries.
Optimisation of the Direct Disposal Concept by Emplacing Spent Fuel Canisters in Boreholes (R&D Project DENKMAL)
Feasibility Study, Basic Design and Engineering Design of a Radioactive Waste Disposal Facility in Iraq
Technical Design and ISAR Preparation for National Disposal Facility in Bulgaria
Site-specific Evaluation of Safety Issues for High-level Waste Disposal in Crystalline Rock (R&D Project URSEL)
Development of Technical Concepts for the Retrieval of Waste Packages with Heat-generating Radioactive Waste and Spent Fuel from Repositories in Salt and Clay Formations – R&D Project ERNESTA
Long-term isolation of radioactive waste in deep geological repositories mainly relies on the ret... more Long-term isolation of radioactive waste in deep geological repositories mainly relies on the retention properties of the host rock. Therefore, the impairment of the host rock must be minimized and existing pathways must be sealed. For sealing of rock fractures, sodium silicate solutions (water or liquid glass) are a commonly used grout. The applicability and efficiency of fracture sealing using water glass was investigated in the course of an R&D project. Field experiences have shown that the permeability of damaged rock salt can be reduced by water glass injection. The sealing effect is a result of the formation of insoluble amorphous silica and other long-term stable minerals due to the chemical reactions with the soluble salts of the host rock as well as salt solutions.
The precipitation of dissolved trace elements in water glass is relevant with regard to the migration of toxic or radioactive elements as trace constituents. This process was analyzed by laboratory tests using brine with barium (Ba), cobalt (Co), iron (Fe), nickel (Ni), and strontium (Sr). The visual observations are comparable to those obtained from well-known crystal or chemical garden experiments, where chemical gardens result from the precipitation reactions generated by adding crystals of a soluble heavy metal salt to aqueous solutions of sodium or potassium silicate. In particular, chemical analyses demonstrate a removal of small divalent ions (Co, Ni) as well as a significant decrease in the UO2 concentration. The precipitates can comprise insoluble salts, as well as hydroxides and silicate phases. Another well-known and in water treatment frequently used property of amorphous silicates is their high sorption capacity.
The Belgian radioactive waste management agency ONDRAF-NIRAS plans to dispose of long-lived and h... more The Belgian radioactive waste management agency ONDRAF-NIRAS plans to dispose of long-lived and high-level radioactive waste in galleries of an underground repository constructed in clay. For stabilization purposes the disposal concept provides a concrete backfilling of the disposal galleries. Plans call for mixing the concrete in above ground facilities and pumping it through the shaft and drifts into the galleries. Upon hardening the backfill will guarantee a corrosion-retarding environment and reduce the mobilization of radionuclide complexes. To avoid an impairment of the gallery walls swelling of concrete must be limited. In addition, the backfill should contribute to the dissipation of the decay heat of the radioactive waste and – according to appropriate legal requirements – its strength must be low enough to enable the retrieval of the waste packages. DBE TECHNOLOGY GmbH was contracted to develop a suitable backfill material and to demonstrate the feasibility of the backfill process. Laboratory tests were carried out including investigations on the pumpability and the flow or spreading behavior of the mixture. Examinations of pore solutions were performed to evaluate the chemical environment with regard to corrosion limitation. Thermal parameters of the backfill material were determined, which will be used as input parameters for future numerical thermal calculations. Mock-up tests were performed to investigate the flow behavior of the grout in 2 m long Plexiglas tubes, which were designed to simulate a section of the disposal galleries. The pump pressure and the pressure in the pipeline were registered in order to develop the design of the backfill system.
ONDRAF/NIRAS, the Belgian Agency for Radioactive Waste and Enriched Fissile Material, proposed ge... more ONDRAF/NIRAS, the Belgian Agency for Radioactive Waste and Enriched Fissile Material, proposed geological disposal in poorly indurated clay as the reference solution for the long-term management of high-level and/or long-lived radioactive waste in Belgium. ONDRAF/NIRAS is currently preparing a safety and feasibility case (SFC), which will describe, substantiate and, as far as possible, quantify the safety and feasibility of the proposed disposal system.
DBE TECHNOLOGY GmbH was commissioned to support ONDRAF/NIRAS by carrying out feasibility studies in regard to the future operation of such a repository. The studies focus on essential parts of the conceptual repository design that need further development and confirmation of technical feasibility, on the demonstration of compliance with safety requirements, and on a cost evaluation. The feasibility studies for a hoisting system for payloads of up to 80 tons, for underground transport and waste emplacement systems, and for repository ventilation have been completed. All systems for transport and ventilation are based on state-of-the-art equipment. The shaft transport system is based on components that have been built and tested at full scale during R&D work carried out by DBE in connection with the German repository projects at Gorleben and Konrad. As a result of the analyses conducted as part of the feasibility studies, several recommendations for optimizations of the original design basis were formulated. In all cases, systems with proven technical feasibility could be designed, which also complied with the requirement for safe and cost effective technical implementation.
According to the Belgian disposal concept, low- and intermediate-level waste will be conditioned ... more According to the Belgian disposal concept, low- and intermediate-level waste will be conditioned in concrete monoliths and high-level waste in so-called supercontainers. In the disposal galleries of the Belgian disposal facility, a trench as roadway and lateral surfaces for laying down the waste packages are provided. The system allows the reversal of the process and the safe return transport of emplaced monoliths and supercontainers until the voids will be backfilled. Thereafter, a sickle-shaped backfill body exists around the upper part of the waste packages and the filled trench of the gallery floor.
Retrieval requires the establishment of safe work conditions and the removal of the narrow backfill bodies over a range of about 3 m (monoliths) to more than 6 m (supercontainers). Thus, a study was carried out to identify a suitable state-of-the- art technology. Initially, techniques commonly used in the building and mining industry were compiled and grouped according to their kind of impact on the backfill. Within the scope of a benefit analysis, a catalogue of evaluation criteria was used to develop a ranking of the techniques. For example, criteria related to the space requirements of the machines and their tools, their potential to damage the waste packages and the surrounding structures, and the removability and amount of the residues. For reasons of workers’ safety, cable-and remote-control-systems are favoured. Milling is a preferred option. Based on these findings, a basic concept for waste package retrieval was developed. Using the specified technologies and procedures, the operational safety and the technical realization of waste retrieval can be assured.
Methods for conditioning liquid and dry radioactive waste can be its immobilization, solidificati... more Methods for conditioning liquid and dry radioactive waste can be its immobilization, solidification or encapsulation by means of cement mixtures. Considering the availability and quality of the raw materials, the requirements of the regulatory framework, and the specific conditions of the waste disposal cycle, a range of mixtures of cements, reactive additives, and fillers can be used. In the last decades, the percentage of products containing latent hydraulic, pozzolanic or limestone filler has steadily increased. Moreover, innovative products have been developed, such as super-plasticisers, to allow the largescale application of ultrahigh performance and self-compacting concrete. This progress influenced the revision and the definition of standards. NDA contracted DBE TECHNOLOGY GmbH as part of a consortium led by EDEN Nuclear and Environment, UK, with a multiphase study to analyze the development in the building sector and the availability of suitable cement compositions for encapsulation purposes. The aim of the first phase of the study is to gain an overview of the practice. Then, the requirements on the cement compositions are to be summarized, taking into account the different disposal strategies in the European countries. The scope and characteristics of the quality assurance programs and the approaches in case of an occurrence of non-conformities are reviewed as well. The aim is to make it possible to identify the need of material optimization and to guarantee a future availability of adequate high-quality cement compositions.
To optimize or restore the barrier function of different host rocks or backfill materials, BGE TE... more To optimize or restore the barrier function of different host rocks or backfill materials, BGE TECHNOLOGY GmbH developed injection materials and grouting techniques to seal any cavities in rocks or backfill materials. In order to stabilize the rock and backfill bodies and to seal cracks, fractures, or pores, suspensions and particle-free injection materials are applied. In saline environments, the particle-containing grouts are based on magnesium oxide. In non-saline areas, mixtures with classic cements as well as reactive and nonreactive fillers are used. Beyond a certain size, particles cannot penetrate into small fractures or pores, which are potential pathways for fluids. As a result, the range of use of these grouts is limited, and water glass is used to seal finer flow paths. However, experience has shown that the penetration of particles can be improved if water glass is injected first and the grouts are injected immediately afterwards. This effect can be explained by a lubrication of solid surfaces and the effect that water glass dissolves salts before gelation and hardening can start. This finding suggests combining water glass, as carrier fluid, with reactive additives. The development work led to novel grout families that also have many other benefits. At elevated injection pressures, the water glass and non-inert solutions are squeezed out of the mixtures, which themselves act as an independent injection agent. This way, it is possible to fill or seal fractures and pore systems of very different sizes in one injection step for the very first time.
Wassergläser sind alkalische Lösungen eines Alkalioxids und von Siliciumdioxid. Aufgrund ihres Wa... more Wassergläser sind alkalische Lösungen eines Alkalioxids und von Siliciumdioxid. Aufgrund ihres Wassergehaltes lösen sie Salze. Die Folge ist das Gelieren der Wassergläser. Es bilden sich Silikate sowie Minerale, deren Zusammensetzung vom Typ des Alkalioxids (Na2O, K2O, Li2O) und dem Stoff¬bestand der Salze abhängig ist. Die Fällungsprodukte verstopfen Risse und Poren und verbinden Rissflanken. Aufgrund der abdichtenden und verfestigenden Wirkung werden Salzgesteine sowie salzhaltige Baustoffe und Versatzstoffe mit Wassergläsern, insbesondere Natron-Wassergläsern injiziert.
Das Lösen der Salze erweitert zunächst geringfügig die Hohlräume. Zudem hat das Wasserglas eine Schmierwirkung. Hierdurch können dem Wasserglas nachströ¬mende Suspensionen in Risse und Poren eindringen, die ohne den Einsatz des Wasserglases nicht für die Suspensionspartikel zugänglich wären. In diesem Fall würden bei üblichen partikelgestützen Injektionsmitteln die Riss- oder Poreneingänge verstopfen und Wasser oder allgemein Baustofflösung in die feineren Wegsamkeiten eindringen. Da die Lösungen dieser Baustoffe, im Gegensatz zu den Wassergläsern keine Eigenerhärtung aufweisen, wird keine abdichtende Wirkung erzielt. Zudem kann die Füllung der feinen Wegsamkeiten mit Baustofflösung problematisch im Hinblick auf den Erfolg weiterer Injektionen sein.
Die vorteilhaften Eigenschaften des Wasserglases wurden genutzt, um partikelgestützte Injektionsmittel ohne die aufgeführten Nachteile herkömmlicher Baustoffe zu entwickeln. Geopolymere belegen, dass Puzzolane und hydraulisch-erhärtende Stoffe, wie die Aluminosilikate Metakaolin und Flugasche in Wasserglas suspendierbar sind und mit diesen zu Festkörpern reagieren. Es zeigte sich, dass auch ma¬gnesiumhaltige Stoffe, wie Magnesiumoxid und Magnesiumhydroxid sowie der extrem feine Silikastaub zur Herstellung von Wasserglas-Suspensionen geeignet sind. Zahlreiche dieser Stoffe sind mit unterschiedlicher Korngröße erhältlich. Da zudem Wassergläser über eine weite Spanne der Fließfähigkeit angeboten werden und ebenso inerte Zusatzstoffe eingesetzt werden können, bietet sich die Möglichkeit die entwickelten Baustoffe an eine Vielzahl von Aufgabenstellungen anzupassen. Die Suspensionen erlauben es größere und feine Wegsamkeiten in einem Zuge zu injizieren und sind bei Bedarf mit klassischen Injektionsmitteln auf Zementbasis, Magnesiabindern und reinen Wasserglaslösungen kombinierbar.
Zementhaltige Baustoffe enthalten alkalische Lösungen. Werden diese Lösungen verdrängt und/oder d... more Zementhaltige Baustoffe enthalten alkalische Lösungen. Werden diese Lösungen verdrängt und/oder diffundieren die Hydroxid-Ionen, können sie mit angrenzenden Materialien reagieren. Die Prozesse sind im Endlagerbergbau relevant, da sie die Permeabilität von Tonen erhöhen, deren Sorptionsvermögen senken und die Funktion von Tonbarrieren beeinträchtigen. Metallen können dagegen passivieren. Die Schutzschichten reduzieren oder verhindern die Korrosion der Metalle und Endlagerbehälter und begrenzen die entstehende Gasmenge, die zu einem Druckaufbau und Phasenfluss führen könnte. Für einen zielgerichteten Einsatz sind daher Baustoffe unterschiedlichen pH-Milieus zu entwickeln und einzusetzen.
Standardbaustoffe haben einen hohen pH-Wert, da Portlandzementklinker Hydroxide bilden. Der pH-Wert kann in Folge von Reaktionen mit Baustoffbestandteilen oder extern zugeführten Stoffen sinken. Hoch-pH-Baustoffe haben ein hohes Widerstandspotential gegen diese pH-Wert-Abnahme. Sie enthalten vor allem Portlandzemente und feste Hydroxide, wie Calciumhydroxid. Die Endfes¬tigkeit wird meist zügig erreicht und eindeutig vom Wasser-Zement-Wert beeinflusst. Wasserglas und Natronlauge wird allgemein eine beschleunigende Wirkung zugeschrieben. Untersuchungen ergaben, dass begrenzte Mengen dem Baustoff zugegeben werden können ohne die hydraulische Förderbarkeit und damit die Eignung als Verfüllmaterial einzuschränken.
Da Zemente stets Portlandzementklinker enthalten, muss zur Gewährleistung niedriger pH-Werte der Klinkeranteil gesenkt werden. Zudem müssen entstehende Hydroxide gebunden werden, beispielsweise durch Reaktionen mit Puzzolanen und latent-hydraulische Stoffen. Die re¬aktiven Stoffe können bereits ein Bestandteil des Zements sein (z. B. Sonder- oder VLH-Zemente nach EN 14216) oder separat zugegeben werden. Reaktive Stoffe haben spezifische Kapazitäten den pH-Wert zu senken, so dass der pH-Wert des Baustoffs eingestellt werden kann. Untersuchungen ergaben, dass silikastaubhaltige Mischungen im Vergleich zu Standardbaustoffen deutlich länger erhärten. Es bildeten sich trotz äußerst hoher Wasser-Zement-Werte homogene Festkörper. Die Be¬funde sind darauf zurückzuführen, dass Silikastaub maßgeblich am Aufbau des Bin¬demittelgerüsts und am Festigkeitsgewinn beteiligt ist. Der Reaktionsumsatz war höher als nach dem k-Wert-Konzept der zementäquivalenten Wirksamkeit (DIN EN 206) zu erwarten ist. Der pH-Werte der Porenlösung konnte auf etwa 9,3 gesenkt werden.
According to the classic approach, fissure or pore systems in solid rock or backfill are to be in... more According to the classic approach, fissure or pore systems in solid rock or backfill are to be injected with particle-laden, and thereafter particle-free material when a high level of impermeability is required. The suspensions used in the salt and potash mining industries are usually in the form of magnesia binders. Waterglass is also frequently employed as a particle-free injection medium because of its capacity to react with salts and saline solutions to form a solid. Waterglass reacts with magnesium oxide (MgO) and many other substances containing magnesium. This served as a basis for developing a new type of injection medium. Unlike magnesia binders these mixtures move out along their flow paths and force waterglass, rather than an inert solution, into the adjoining areas. The lubricating effect of the waterglass improves the capacity of the particles to penetrate the cavities. This increases the degree to which the voids are filled with reactive material and the number of injections can potentially be reduced as a result. The mixtures can be combined with magnesia binders and pure waterglass and this serves to enhance the available range of injection media.
Nach der klassischen Vorgehensweise sind Riss- oder Porensysteme eines Gesteins oder Versatzes mit partikel-haltigen und danach partikelfreien Baustoffen zu injizieren, wenn eine hohe Dichtigkeit gefordert wird. Im Kali- und Steinsalzbergbau sind die Suspensionen meist Magnesia¬binder. Aufgrund der Fähigkeit mit Salzen und Salzlösungen zu Feststoffe zu reagieren, werden häufig als partikelfreie Injektionsmittel Wassergläser eingesetzt. Wassergläser reagieren auch mit Magnesiumoxid (MgO) und vielen weiteren magnesiumhaltigen Stoffen. Dies war die Grundlage einen neuen Typ von Injektionsmitteln zu entwickeln. Bei diesen Mischungen wird im Gegensatz zu Magnesiabindern ausgehend von ihren Strömungswegen keine inerte Lösung, sondern Wasserglas in die angrenzenden Bereiche abgepresst. Eine Schmierwirkung des Wasserglases verbessert das Eindring-vermögen der Partikel in Hohlräume. Durch diese Effekte steigt das Ausmaß der Hohlraumauffüllung mit reaktivem Material und es ergibt sich die Möglichkeit die Anzahl der Injektionen zu reduzieren. Die Mischungen sind mit Magnesiabindern und reinen Wassergläsern kombinierbar und bereichern damit die Palette an Injektionsmitteln.
Der Einsatz von Focus-Stacking bei der Untersuchung von Flüssigkeitseinschlüssen im Steinsalz
Mik... more Der Einsatz von Focus-Stacking bei der Untersuchung von Flüssigkeitseinschlüssen im Steinsalz Mikroskopisch kleine Flüssigkeitseinschlüsse erlauben Rück¬schlüsse zur Entste¬hung und Geschichte eines Gesteins. Um Aussagen über ihre Entstehung treffen zu können, sind zuerst die Anordnung der Einschlüsse, ihre Form, die Art und Menge von Mi¬neralbestandteilen und die Größe von Gasblasen auszuwerten. Hohe Vergrößerun¬gen reduzieren die Schärfentiefe des Abbildes, so dass Details der Einschlüsse nur in einer Schnittebene erkennbar sind und die Un¬tersuchungen erschwert werden. Das Verfahren des Focus-Stackings kann in diesen Fällen hilfreich sein, da es digi¬tale Daten von Fotos, deren Schärfe¬tiefebereiche sich über¬schneiden, miteinander verrechnet. Praxistests, die an Dünnschliffen von Steinsal¬zen durchge¬führt wurden, zeigen, dass das Verfahren Bilder hoher Qualität erzeugt. Die ge¬wünschten Proben¬bereiche werden scharf dargestellt. Ein Nachteil des Ver¬fahren könnte jedoch die Zeitdauer der Rechen¬operationen sein. Zur Minimierung des Zeitaufwan¬des sollten daher Erfahrun¬gen zur Auswahl des Fotomaterials und zum Einfluss der auswähl¬baren Rechenme¬thoden auf das Stackresultat vorliegen. Für Präsenta¬tionen kann zu¬dem mit einer speziellen Software eine Bildnachbear¬beitung erfor¬derlich sein, um Artefakte der Stack-¬Berechnung und Bildfehler, die aus dem opti¬schen System resultieren, zu entfernen.
The application of the focus-stacking-technique for the examination of fluid inclusions in rocksalt It is possible to draw conclusions from microcopically small fluid inclusions about the genesis and history of a rock. For an assessment, it is necessary to gather information about the arrangement of the inclusi¬ons, their shapes, the types and amounts of mineral components, and the size of gas bubbles. High magnifications reduce the depth of field of an image so that details of the inclusions are limited to a plane cutting through the inclusi¬ons, which mades the investigations diffi¬cult. In this case, focus stacking, also known as focal plane merging, can be a helpful technique. It proces¬ses the digital data of images with overlapping depths of fields. Practical tests, carried out on thin section of rock salt show that this technique generates high-quality-images. The desired areas of the samples are displayed in sharp focus. One drawback of this technique could be the long processing periods. Experience concerning the selection of the photographic material and the influence of the processing methods on the stack results helps to minimize the time needed. If the images are to be used for presentation pur¬poses, it can be ne¬cessary to erase artifacts of the stack-processing and to corrigate image errors, which result from the optical system, by means of a special photo finishing software.
Schlüsselwörter: Berechnungsartefakte, Bildbearbeitung, Bildqualität, Mikroskopie, Schärfentiefe, Stapeltechnik, Zeitaufwand Keywords: Artifacts, computing time, depth of field, digital image processing, focal plane merging, focal point, focus blending, image quality, microscopy, sharpness
In Belgium, it is planned to dispose of long-lived and high-level waste in an underground facilit... more In Belgium, it is planned to dispose of long-lived and high-level waste in an underground facility. After disposal of the waste, the galleries will be back¬filled to provide stability to the galleries and to limit the amount of voids in the repository. To achieve those goals, the backfill material has to have a good flowability, a negligible bleeding, and a limited shrinkage. A limited grain size is also required to allow the injection of the backfill material. Despite the fact that the backfill supports the gallery lining, its strength must be low enough to enable the retrieval of the waste packages. The backfill material has to be chemically compatible with the Boom Clay and the waste packages. This means that it should not unduly perturb the clay or disposal packages. The thermal conductivity of the backfill material in the galleries containing high-level and thus heat-generating waste must be high enough to allow sufficient dissipation of the decay heat into the surrounding clay.
Based on these objectives, material requirements were specified and the development of a backfill mixture was carried out. Initially, the mix composition was optimized in the laboratory. Thereafter, the backfill process of a gallery section was simulated. The investigations illustrate that this mixture can be transported via pipelines through the shaft and drifts and would fill completely the backfill sections in the galleries. Measurements of the porosity, the pore solution composition, the thermal material properties, and the strength illustrate the compliances with the requirements and the feasibility of backfilling the disposal galleries. ---- The Belgian National Agency for Radioactive Waste and enriched Fissile Material ONDRAF/NIRAS is studying the disposal of low and medium activity level, long-lived waste (category B) and high activity, heat-generating waste (category C) in an underground facility. The repository is built at a reference depth of approximately 230 m in the Boom Clay host rock. Two shafts are built for personnel and material transfer and to provide ventilation during the construction and operation of the repository. A third shaft will be constructed for the waste transport. The shafts are connected via horizontal access galleries. The disposal galleries are constructed perpendicular to the access galleries. They are blind or dead-end galleries with a diameter of approx. 3.0 m and a length of 1,000 m. Fig. 1 shows an overview of the repository layout. The galleries in the clay will be lined with concrete wedge blocks. In the order to transport and to support the waste packages after disposal, the galleries are outfitted with a concrete floor. It is planned to backfill the galleries section by section with a cement-based material, because grout injection is assumed to offer better opportunities for achieving the industrial performance that is required to backfill such volumes in a relatively short period of time. The current planning assumes a volume of the sections of approximately 85 m³, which will be backfilled in three and a half hours. Seals will be placed at the front-end of the disposal galleries.
The main functions of the backfill mortar are (1) isolating the waste by forming an extra barrier to the waste, (2) providing the galleries with stability and thus avoiding a gallery collapse and (3) reducing the voids in the repository which is a regulatory requirement.
As the backfill needs to realize a high filling degree, it has to show good flowability, negligible bleeding, and limited shrinkage. The grain size is limited to allow the injection of the backfill material. Another important requirement for the backfill follows from the potential requirement for waste retrievability. This means that the strength of the backfill has to be sufficient low so that the backfill can be removed at a later stage. In addition, a high porous backfill might be envisaged as it can provide a storage volume for gas generated in the repository and consequently limit the gas pressure build-up. This is in particular important for the category B waste for which the gas generation is expected to be more significant than for the category C waste. The backfill material has to be chemically compatible with the Boom Clay host formation and any other component of the disposal system like the gallery lining and the waste disposal packages. This means that it should not unduly perturb the clay or disposal packages. Finally, the thermal conductivity of the backfill material in the category C waste disposal galleries must be high enough to allow sufficient dissipation of the heat from the category C waste into the surrounding clay. Furthermore, it has to be thermally stable under the maximum temperature that will occur in the backfill material.
Within the preliminary safety analysis for the Gorleben site (VSG), a closure system was designed... more Within the preliminary safety analysis for the Gorleben site (VSG), a closure system was designed in order to complement the containment providing rock zone (CRZ) by sealing and backfilling measures. The design procedure as well as the technical proof of function was mainly performed according to standard procedures in civil engineering. In the context of VSG, rough individual technical proofs of several measures were carried out. Meanwhile, this gap has been closed by subsequent investigations. Altogether the results of all the individual technical proofs of function indicate that safe containment of radioactive waste is a realistic possibility at the Gorleben site. --- In summer 2010, the German Federal Government launched a preliminary safety analysis to assess whether the salt dome at Gorleben is suitable to host all heat-generating radioactive waste generated by German NPPs. A repository concept was developed that also included a closure system.
In the course of seawater evaporation, calcite, gypsum, halite and eventually potassium and magne... more In the course of seawater evaporation, calcite, gypsum, halite and eventually potassium and magnesium salts crystallize in accordance with solubility with water. This correlation can be used to separate the "white gold" halite from the other salts and to harvest the solar seasalt in ponds, if enough water evaporates due to dry winds. In the arid climate of Lanzarote, the Salinas de Janubio produced in there heyday about 10000 tons of table and pickling salt on an area of 45 hectares. In the ponds and in particular on the ramparts of the basaltic rock pebbles, which show honeycomb- or tafone-like weathering features, lawns of gypsum crystals grew. Most remarkable are crystals that embedded foreign particles along crystal planes during growth and that extended across several layers of crystal lawns. Obviously, the different crystal shapes, which are unusual for gypsum, and lawn structures result from changes of the weather and variations of the operating conditions of the ponds.
Bei der Evaporation von Meerwasser bilden sich entsprechend der Abfolge ihrer Löslichkeit Carbonat, Gips, Halit sowie kalium- und magnesiumhaltige Salze. Diese Gesetzmäßigkeit erlaubt es Halit als weißes Gold von den weiteren Salzen zu trennen und auf Salzfeldern zu "ernten", wenn durch trockene Winde ausreichende Mengen an Wasser verdunsten.
Die Verwendung von Referenzprobern ist im Bereich der Analytik ein wichtiges Kriterium zur Beurte... more Die Verwendung von Referenzprobern ist im Bereich der Analytik ein wichtiges Kriterium zur Beurteilung der Qualität quantitativer Analysen. Um den Verbrauch zertifizierter und teurer Referenzproben einzuschränken, werden in zunehmendem Maße von Laboratorien sogenannte "in-house standards" hergestellt. Hierbei kommt der Probebearbeitung eine besondere Bedeutung zu. So muss die Homogenität und Reinheit des Probematerials weitestgehend gewährleistet sein.
Die Durchführung quantitativer Analysen erfordert die Verwendung von Referenzmaterialien. Denn auch bei einer sehr guten Reproduzierbarkeit der Messdaten kann nicht auf deren Richtigkeit geschlossen werden. Der Stoffbestand von Referenzproben ist jedoch hinsichtlich der Richtigkeit bekannt und kann zur Überprüfung der Messresultate herangezogen werden. Da zertifizierte Referenzproben nur eine begrenzte Zeit und häufig in kleinen Mengen zur Verfügung stehen, ist es vorteilhaft interne Referenzproben, sogenannten "in-house standards" zu benutzen. Sie sollten aus dem gleichen Material wie die zu untersuchenden Proben bestehen und können ebenso zur Erarbeitung von Analysenverfahren eingesetzt werden.
In the course of seawater evaporation, calcite,
gypsum, halite and eventually potassium and
magne... more In the course of seawater evaporation, calcite, gypsum, halite and eventually potassium and magnesium salts crystallize in accordance with their solubility in water. This correlation can be used to separate the “white gold” halite from the other salts and to harvest the solar seasalt in ponds, if enough water evaporates due to dry winds. In the arid climate of Lanzarote, the Salinas de Janubio produced in their heyday about 10.000 tons of table and pickling salt on an area of 45 hectares. In the ponds and in particular on the ramparts made of basaltic rock pebbles, which show honeycomb- or tafone- like weathering features, lawns of gypsum crystals grew. Most remarkable are crystals that embedded foreign particles along crystal planes during growth and that extend across several layers of crystal lawns. Obviously, the different crystal shapes, which are unusual for gypsum, and lawn structures result from changes of the weather and variations of the operating conditions of the ponds.
Bei der Evaporation von Meerwasser bilden sich entsprechend der Abfolge ihrer Löslichkeit Carbonat, Gips, Halit sowie kalium- und magnesiumhaltige Salze. Diese Gesetzmäßigkeit erlaubt es Halit als weißes Gold von den weiteren Salzen zu trennen und auf Salzfeldern zu „ernten“, wenn durch trockene Winde ausreichende Mengen an Wasser verdunsten. Im Klima Lanzarotes wurden zu ihrer Blütezeit in der Salinas de Janubio auf einer Fläche von rund 44 Hektar jährlich etwa 10.000 Tonnen Speise- und Pökelsalz gewonnen. In den Becken und vor allem an ihren Wällen aus basaltischen Gesteinen, die tafoneartig verwittern, entstehen Kristallrasen von Gips. Auffallend sind vor allem Kristalle, die während ihres Wachstums Fremdpartikel einschlossen und über mehrere Lagen reichen. Die unterschiedlichen, für Gips auch ungewöhnlichen Kristallformen und Verwachsungen beruhen offensichtlich auf Änderungen der Witterung und der Betriebsweise der Salzbecken.
The investigation of transport processes of clays in the aquatic environment is important as many... more The investigation of transport processes of clays in the aquatic environment is important as many pollutants are adsorbed on the surface of fine-grained particles or clay-organic complexes. Suppliers are rivers draining industrial centers. The material is mixed with lithogenic grains characterized by geogenic background compositions. In the Wadden Sea tidal flats large amounts of fine size sediments are accumulated. Sources which must be taken into consideration are rivers (Elbe, Ems, Weser) and pleistocene deposits, eroded from the coast and seafloor. This study used mineral specific properties to determine the portion of the potential source materials on Wadden Sea tidal flat deposits and suspensions. The following features were measured (= 0.16), the samples of the tidal flats vary from 0.11 to 0.15, and the glacial sediments have the worst crystallinity (le0.11). K/Rb-ratios show a dominance of the fluviatile detritus (tidal flats ˜145, glacial deposits ˜170, fluviatile bedload ...
Graduation towers are frameworks stuffed with blackthorn bundels. Pumps transport brines to the t... more Graduation towers are frameworks stuffed with blackthorn bundels. Pumps transport brines to the top of the towers. Afterwards, the brine flows down on these bundels and drops are formed by the impact with the twigs and branches. Due to the enormous surface of the drops, the water evaporation increases, and so-called thornstone precipitates. It consists of gypsum crystals, which mostly radiate out from the twigs of the blackthorn bundles. The surface of the thorn¬stone is compa¬rable with sandroses. Occasionally, a rounding of the crystals can be observed, which is caused by dissolution processes. Samples of the graduation tower in Bad Kösen, Germany, show that the thornstone contains layers of foreign particles, fine-grained carbonates, and sometimes traces of halite. Moreover, high strontium contents illustrate that the brine could be evaporated until halite satura¬tion. Due to its high efficiency, the technique made it possible to produce table and pickling salt during the 18th and 19th century, even from low-concentrated brines and under the climatic conditions in Austria, Germany, Poland, and in Switzerland.
Nowadays, graduation towers are centres of recreation in spa towns. The particle inclusions of the thornstone demonstrate the cleaning of the air. Wa¬ter evapora¬tion cools the air and the microclimate with fresh, salty aerosols is used for therapeutic inhalations. The trickling of brine creates a relaxing atmosphere and the brines can be used for bath therapies. In addition, the towers are technical monuments, tourist attractions, and event locations. Visitors have the opportunity to learn principles of solution mining and salt processing.
Backfilling and sealing are integral parts of the multi barrier concept of a geological disposal ... more Backfilling and sealing are integral parts of the multi barrier concept of a geological disposal facility (GDF). General tasks of the backfill are to stabilize openings, to minimize the void volume that can be filled with water or brines, and to ensure a favorable chemical milieu with regard to the overall disposal system. Depending on these functions and the conditions provided by the GDF design and the safety concepts, backfilling materials have to comply with a wide scope of requirements.
ONDRAF/NIRAS the competent Belgian organization for radioactive waste management proposes to build a GDF in a poorly indurated clay host rock. Low- and intermediate-level radioactive waste (B-waste) will be conditioned in concrete monoliths B and high-level, heat-generating waste (C-waste) in so-called Supercontainers (SC). The SCs consist of overpacks embedded in concrete and a steel envelope. The two types of waste packages will be disposed of in separate fields of the future GDF.
In the framework of a technical support project with ONDRAF/NIRAS, DBE TECHNOLOGY GmbH has developed reference backfilling materials. It is planned to backfill the remaining voids inside the disposal galleries stepwise after the emplacement of a specified number of waste packages. As the space underground is restricted and to generally minimize operational activities underground, the preferred concept is to mix the backfill above ground and to pump the mixture via a piping system into the backfill segments. Consequently the backfill material has to remain in a flowable condition for the time needed for the transport process. After filling the segments, the backfilling material shall harden without swelling or significant shrinkage to homogenous bodies. Additionally, according to the current ONDRAF/NIRAS retrievability concept, the strength of the backfilling bodies has to be low enough to allow a later excavation of waste packages should that be required.
Initially, these general tasks suggest the development of a universally usable material for the backfilling of all galleries. Nonetheless, the different characteristics of the B- and C-waste packages and differences in the designs of the emplacement fields require the specification of individual catalogues with many common, but also several different material requirements for the development of backfilling material for B- and C-waste disposal galleries.
The requirement of chemical compatibility makes it necessary to use a cement-based backfill and all potential mixtures must meet the criteria for hydraulic backfilling. However, particularly high demands have to be specified for the time of workability and flowability of the backfill of the C-waste field due to its large extension resulting in pipeline lengths of up to 4000 m.
Other deviating requirements for material properties of the two backfill types originate from the long-term behavior of the two waste types. For instance, the pore volume of the B-waste backfill must be large enough to allow gas flow and thereby minimize a possible gas pressure built-up, due to the degradation of organics. In contrast, a lower porosity is favored to achieve a higher thermal conductivity for a better dissipation and removal of the C-waste decay heat. Moreover, for the C-waste backfill a minimum pH value was prescribed with the objective to guarantee a long-term passivation and corrosion resistance of the SC steel surface.
After defining the requirement catalogues, the next step was dedicated to the selection of suitable raw materials based on the knowledge of technological properties of available high-quality materials. For instance, Portland limestone cement was selected as the binder of the B-waste backfill and a Portland cement for the C-waste backfill to achieve the required high pH value in this waste field. Another example is the use of sand aggregate, which is allowed in the B-waste field, while only limestone powder and aggregate were considered for the development of the C-waste backfill to safely prevent alkali-silica reactions at elevated temperatures.
Usually, the time span of workability of low-porosity Portland cement mixtures is limited, whereas the backfilling of the voids in the C-waste field require an exceptional long potlife. This example demonstrates that different requirements often have contrary consequences for the material selection and vice versa. Consequently, one focus of the backfill development was to identify compositional ranges that guarantee the respective material property. Finally, a combination of the individual „conformity fields“ results in the optimal solution for the standard operating conditions as well as a compositional range that guarantees compliance with the required material specifications. These interrelations and the general strategy used to reach the optimal solution will be demonstrated for the two development lines of the B- and C-waste backfill. The principle strategy can be adapted to many underground repositories and conventional mines.
The Belgian radioactive waste management program has focused on the disposal of long-lived radioa... more The Belgian radioactive waste management program has focused on the disposal of long-lived radioactive waste in a clay formation. The current repository layout foresees two shafts located in a central service area. One shaft serves the transport of waste packages and the second one is designed for staff and material transport. The two emplacement fields, one for low- and intermediate-level waste (B-waste according to the Belgian nomenclature) and the other for high-level, heat-generating waste (C-waste) are located at two opposite sides of the central area. Two parallel access galleries run through the middle of each emplacement area and connect the disposal galleries that are constructed perpendicular to the access galleries with the central service area of the repository. The disposal galleries are 400 m long, blind or dead-end galleries. The total repository footprint is 4.3 km in length and 0.9 km in width. During the first construction phase only the central service area and the galleries of the B-waste emplacement field will be excavated. After the end of disposal, backfilling and closure operations in the B-waste part, the C-waste part will be excavated and disposal and backfilling operations will be carried out. According to the Belgian reference concept, B-waste will be conditioned in concrete monoliths and C-waste in so-called supercontainers (SCs). The waste packages (WPs) will be transported on trolleys of a hybrid rail-wheel configuration using battery driven locomotives. Backfilling of the disposal galleries after WP emplacement is supposed to be carried out in segments of approximately 50 m length. To increase the level of operational safety in the repository, it is planned to strictly separate disposal and backfilling operations. Considering the framework conditions at the site, it was necessary to develop a specific backfill material, taking into account the particular material requirements resulting from the characteristics of a clay host rock formation and a suitable backfilling technique. The current reference solution is to mix the backfill at the surface and then to pump the mixture through a pipeline distribution system installed inside the access shaft and the galleries. Based on the boundary conditions derived from the waste transport system, the backfill production and distribution system, the WP production, and certain strategic decisions by the Belgian Waste Management Organization, ONDRAF/NIRAS, a numerical model has been developed to simulate the operational activities during emplacement and backfilling. Results of the simulation demonstrate the influence of certain parameters like working time, dimensions and number of disposal galleries in operation, size of buffer storage for WPs, etc. on the WP emplacement rates. The outcome of the simulation will be used to optimize the emplacement and backfilling concept in a way that the WP emplacement rate does not fall behind the WP production rate, which would prolong the minimum operational period of the repository. At the same time the results will help to prevent significant over capacities in regard to emplacement and backfilling or buffer storage to economically optimize the operation of the repository.
The Belgian Agency for Radioactive Waste and En-riched Fissile Materials, ONDRAF/NIRAS, proposes ... more The Belgian Agency for Radioactive Waste and En-riched Fissile Materials, ONDRAF/NIRAS, proposes to develop a geological disposal facility for the long term management of category B waste and category C waste. Without any preconceived opinion regarding the site location, ONDRAF/NIRAS developed a reference design of a geological disposal facility in a clay formation. The facility consists of two shafts and underground galleries that can be allocated to the shaft and support zones and two wings with connecting access galleries, and branching disposal galleries. The facility for waste disposal package (DWP) production and a buffer/interim storage facility will be erected near to the waste transport shaft at the surface. Long-lived, low- and intermediate level waste (B waste) will be conditioned in concrete monoliths and high-level waste (C waste) in so-called supercontainers (SC). The DWPs will be transported on trolleys of a hybrid rail-wheel configuration using battery driven locomotives. After the emplacement of a specified number of DWPs a formwork will be installed and voids will be backfilled. It is foreseen to mix the backfill at the surface and to pump the material through a pipeline distribution system. An insufficient performance of backfill processes and/or emplacement rates that are significantly smaller than the production rate of the DWPs would cause inter-ruptions in DWP production. The total operational phase of the facilities would be extended and associated costs increased. The relation between DWP production rate and emplacement rate is therefore of great importance. To investigate the general feasibility of the planned operation and to identify bottlenecks, areas for optimization etc., DBE TECHNOLOGY GmbH carried out simulations of the future operation. The simulation model considers all relevant boundary conditions, e.g. the disposal facility design, the planned transport and backfill techniques, and strategic decisions of ONDRAF/NIRAS relating to the operation of the facilities. For example, one scenario considered to start the emplacement of the DWPs in the rearmost parts of the emplacement fields, and to carry out the construction of the plugs at the entrance of the disposal galleries, and the backfilling of the access galleries after backfilling of all disposal galleries. According to the results of the simulations, at the be-ginning of the disposal operation the production rate will marginally exceed the rate of emplacement due to the longer transport routes. Consequently, the buffer is filled up with monoliths, however, this does not lead to a reduction of DWP production. Before the capacity of the buffer storage is exceeded, the decrease of transport distances and times with disposal operations advancing towards the shaft leads to an increased emplacement rate. The buffer stock is reduced and all new monoliths can be emplaced according to the DWP production rate. Failures of the emplacement and backfilling tech-nique do not have significant effects for emplacement, because the buffer facility has a sufficient capacity. In addition, a variety of operational measures can be real-ized to raise the speed of emplacement and backfilling after resumption of the works, e.g. a temporary change from single shift to two shift operation. Consequently, there seems to be little risk that the average emplacement rate will fall back behind the DWP production rates and cause an extension of the total disposal operation period. According to the simulations, the emplacement of the monoliths will last slightly less than 13 years. The construction of the plugs and a final seal is still at the planning stage and no safe statements can be made to the time period of their implementation. However, a little more than 400 work days (~1.6 calendar years) can be estimated for the backfilling of the access galleries and their connecting galleries of the B waste field, if the works in the access galleries can be carried out simultaneously. After closure of the B waste field, the second wing of the disposal facility will be constructed and the supercontainers will be emplaced in analogy to the B waste monoliths. Further simulation studies will examine the effects of the major differences between the planned operation of the B waste part of the disposal facility and its C waste part.
The Belgian radioactive waste management program has focused on the disposal of long-lived radioa... more The Belgian radioactive waste management program has focused on the disposal of long-lived radioactive waste in a clay formation. The current repository layout foresees two shafts located in a central service area. One shaft serves the transport of waste packages and the second one is designed for staff and material transport. The two emplacement fields, one for low- and intermediate-level waste (B-waste according to the Belgian nomenclature) and the other for high-level, heat-generating waste (C-waste) are located at two opposite sides of the central area. Two parallel access galleries run through the middle of each emplacement area and connect the disposal galleries that are constructed perpendicular to the access galleries with the central service area of the repository. The disposal galleries are 400 m long, blind or dead-end galleries. The total repository footprint is 4.3 km in length and 0.9 km in width.
During the first construction phase only the central service area and the galleries of the B-waste emplacement field will be excavated. After the end of disposal, backfilling and closure operations in the B-waste part, the C-waste part will be excavated and disposal and backfilling operations will be carried out.
According to the Belgian reference concept, B-waste will be conditioned in concrete monoliths and C-waste in so-called supercontainers (SCs). The waste packages (WPs) will be transported on trolleys of a hybrid rail-wheel configuration using battery driven locomotives. Backfilling of the disposal galleries after WP emplacement is supposed to be carried out in segments of approximately 50 m length. To increase the level of operational safety in the repository, it is planned to strictly separate disposal and backfilling operations.
Considering the framework conditions at the site, it was necessary to develop a specific backfill material, taking into account the particular material requirements resulting from the characteristics of a clay host rock formation and a suitable backfilling technique. The current reference solution is to mix the backfill at the surface and then to pump the mixture through a pipeline distribution system installed inside the access shaft and the galleries.
Based on the boundary conditions derived from the waste transport system, the backfill production and distribution system, the WP production, and certain strategic decisions by the Belgian Waste Management Organization, ONDRAF/NIRAS, a numerical model has been developed to simulate the operational activities during emplacement and backfilling. Results of the simulation demonstrate the influence of certain parameters like working time, dimensions and number of disposal galleries in operation, size of buffer storage for WPs, etc. on the WP emplacement rates. The outcome of the simulation will be used to optimize the emplacement and backfilling concept in a way that the WP emplacement rate does not fall behind the WP production rate, which would prolong the minimum operational period of the repository. At the same time the results will help to prevent significant over capacities in regard to emplacement and backfilling or buffer storage to economically optimize the operation of the repository.
Suspension- and deposit-feeding organisms assimilate with their food clay minerals. The particles... more Suspension- and deposit-feeding organisms assimilate with their food clay minerals. The particles are exposed in the digestive system to different Eh-pH conditions, enzymes, intestinal bacteria, and mechanical destruction. Therefore a biodegradation of the minerals should occur.
To improve the knowledge about biodegradation, this process was investigated by laboratory experiments and in the Wadden Sea tidal flats of Northern Germany.
Untersuchungen an wasserunlöslichen Rückständen von Evaporitformationen belegen infolge des Konta... more Untersuchungen an wasserunlöslichen Rückständen von Evaporitformationen belegen infolge des Kontaktes mit hochsalinaren Lösungen signifikante Veränderungen des mineralogischen Stoffbestandes. Festzustellen ist vor allem eine Bildung von Corrensit, Mg-Chlorit, Talk sowie Koenenit neben geringen Anteilen von Sepiolith und Serpentin. In marinen Salzseesedimenten sind im Vergleich hierzu Neubildungen von Tonen mit Faserstruktur, z. B. Palygorskit (Attapulgit) und Sepiolith sowie von Talk, neben trioktaedrischen Smektiten (Stevensit, Saponit) und Corrensit nachzuweisen. Trotz der bestehenden Unterschiede der mineralogischen Befunde, ist der Trend der Entwicklung des geochemischen Stoffbestandes in marinen Evaporiten und Salzseesedimenten identisch. Ausfällig ist insbesondere ein Anstieg der Mg-Konzentration, der auf die erhöhten Gehalte trioktaedrischer Minerale zurückzuführen ist.
Zur Bestimmung der Reaktionskinetik von Schichtsilikaten mit hochsalinaren Lösungen begannen 1996 Versuchsreihen mit einer Vielzahl von monomineralischen Tonen und Tonmineralgruppen, die derzeit noch andauern. ....
Evaporitformationen enthalten in unterschiedlichem Umfang Lösungen und Gase, die infolge bergmänn... more Evaporitformationen enthalten in unterschiedlichem Umfang Lösungen und Gase, die infolge bergmännischer Arbeiten, z. B. beim Niederbringen von Bohrungen, aufgeschlossen werden können. Aufgrund der mechanischen Eigenschaften, d. h. der Neidung zur Bildung von Brüchen, sind die flüssigen und gasförmigen Phasen insbesondere in mächtigeren Einheiten gespeichert, die hauptsächlich aus Anhydrit bestehen. ....
Nach BVOT wurde der Bohrlochkopf mit Absperrvorrichtungen versehen (vgl. API RP53). Die Druckstufen der Preventer müssen den höchsten zu erwartenden Kopfdrücken genügen. .... Da der Druck von Lösungs- und Gasreservoiren identisch dem auflagernden Gebirgsdruck ist, wurde eine Ausrüstung entsprechend der Nenndruckstufe 3M eingesetzt. Dies entspricht 3000 psi bw. etwa 210 bar (21 MPa). Zur Trennung der Gas- und Flüssigkeitsvolumina diente ein Separator, der über eine Choke-Line und ein Choke-Manifold an den Bohrlochkopf angeschlossen war. Die Quantifizierung des Gases erfolgte mit einem handelsüblichen Zähler für Feuchtgas, während die Salzlösung in einem Tank gesammelt ...
... Um die geologischen Lagerungsverhältnisse des Gebirges zu bestimmen, wurden unterschiedliche ... more ... Um die geologischen Lagerungsverhältnisse des Gebirges zu bestimmen, wurden unterschiedliche Kernorientierungssysteme eingesetzt. Neben den Orientierungen dienten die Systeme der exakten Bestimmung des Bohrlochverlaufs. Insgesamt fanden Untersuchungen mit zwei, einem mechanischen sowie einem elektronischen Multishot-System statt. ... Zur Klärung der geologischen Lagerungsverhältnisse und der Bohrrichtung war es erforderlich, die Gesteinskerne regelmäßig zu orientieren. Anfänglich wurde das in den 70er Jahren entwickelte Verfahren des mechanischen Single- und Multishot-Systems (MMS) eingesetzt. Hierzu wird das Kompass-Pendelteil mit kardanisch aufgehängtem Kompass und integrierter Kamera, auf das obere Innenkernrohr geschraubt und der Winkel der Messsonde zum sogenannten Hauptmesser, das innerhalb der Kernritzhülse im unteren Innenkernrohr sitzt, bestimmt. Während des Bohrfortschritts wandert der Bohrkern in das untere Innenkernrohr und wird durch drei in unterschiedlichen Winkeln zueinander stehenden Ritzmessern oberflächlich angeritzt. Die Bohrung wird nach definierten Abständen angehalten und der Kompass mit Angaben über Neigung und Azimut der Bohrung sowie dem momentanen Winkel der Messsonde zum Hauptmesser fotografisch festgehalten. ....
Concrete barriers are an important component of many repository designs. Proofs of barrier tightn... more Concrete barriers are an important component of many repository designs. Proofs of barrier tightness necessitate numerical calculations of thermal stresses. A requirement to perform such calculations is the knowledge of the heat evolution during the hardening of the building material. Data of isothermal and adiabatic calorimetry are usually preferred when quantitative results are needed. Isothermal techniques are applied in particular to fine-grained pastes, and are more useful in cases, when the influence of hydration heat on the temperature of the building material is negligible. Thus, data registered under adiabatic conditions were used for the development of so-called hydration models, coupling the heat evolution of mass concrete with the increase of mechanical properties. Most of these methods require an equipment, which making them unsuitable for field application. As a consequence, for quality control measures, a semi-adiabatic test procedure was developed and evaluated to monitor the heat evolution of concretes and magnesia binders under the conditions of an underground mine.
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Papers by Hans-Joachim Engelhardt
BGE TECHNOLOGY GmbH's key activities focused on the following issues:
● design of 3 repository variants for the emplacement of HLW and spent fuel. All versions take into account the requirement of retrievability. As a further option, combined emplacement with LLW/ILW was analysed.
● Development of closure concepts for all variants and optimisation of the concepts based on the results of consequence analyses
● development of geotechnical barrier concepts and demonstration of the barrier's integrities
● development of a FEP cataloque
● development of reference and alternative scenarios for the different repository variants
analysis of human intrusion scenarios
Technical Support for Conducting Studies in the Field of Radioactive Waste Management – Conceptual Design for Backfil Removal Equipment allowing Retrieval of Waste Packages
One of the problems currently investigated by ONDRAF/NIRAS in regard to waste disposal is the potential need to retrieve waste packages from the disposal galleries after these have already been backfilled. The objective of this study was to identify and conceptually design suitable technical equipment for the removal of the backfill material.
The study describes the necessary equipment with special regard to the expected boundary conditions:
● type of backfill material
● confined spaces and limited working area inside the disposal galleries
● irregular cross sections and backfill dimensions around the waste packages
● working conditions next to the waste packages (radiation, heat)
The study further covers a preliminary cost assessment for buying/developing the equipment and addresses the potential impact of the selected backfill removal equipment on the required minimum diameter of the disposal galleries.
Optimisation of the Direct Disposal Concept by Emplacing Spent Fuel Canisters in Boreholes (R&D Project DENKMAL)
Cigéo – Technical Planning Surface – Underground Connections and Underground Excavations
Feasibility Study, Basic Design and Engineering Design of a Radioactive Waste Disposal Facility in Iraq
Technical Design and ISAR Preparation for National Disposal Facility in Bulgaria
Site-specific Evaluation of Safety Issues for High-level Waste Disposal in Crystalline Rock (R&D Project URSEL)
Development of Technical Concepts for the Retrieval of Waste Packages with Heat-generating Radioactive Waste and Spent Fuel from Repositories in Salt and Clay Formations – R&D Project ERNESTA
The precipitation of dissolved trace elements in water glass is relevant with regard to the migration of toxic or radioactive elements as trace constituents. This process was analyzed by laboratory tests using brine with barium (Ba), cobalt (Co), iron (Fe), nickel (Ni), and strontium (Sr). The visual observations are comparable to those obtained from well-known crystal or chemical garden experiments, where chemical gardens result from the precipitation reactions generated by adding crystals of a soluble heavy metal salt to aqueous solutions of sodium or potassium silicate. In particular, chemical analyses demonstrate a removal of small divalent ions (Co, Ni) as well as a significant decrease in the UO2 concentration. The precipitates can comprise insoluble salts, as well as hydroxides and silicate phases. Another well-known and in water treatment frequently used property of amorphous silicates is their high sorption capacity.
DBE TECHNOLOGY GmbH was commissioned to support ONDRAF/NIRAS by carrying out feasibility studies in regard to the future operation of such a repository. The studies focus on essential parts of the conceptual repository design that need further development and confirmation of technical feasibility, on the demonstration of compliance with safety requirements, and on a cost evaluation. The feasibility studies for a hoisting system for payloads of up to 80 tons, for underground transport and waste emplacement systems, and for repository ventilation have been completed. All systems for transport and ventilation are based on state-of-the-art equipment. The shaft transport system is based on components that have been built and tested at full scale during R&D work carried out by DBE in connection with the German repository projects at Gorleben and Konrad. As a result of the analyses conducted as part of the feasibility studies, several recommendations for optimizations of the original design basis were formulated. In all cases, systems with proven technical feasibility could be designed, which also complied with the requirement for safe and cost effective technical implementation.
Retrieval requires the establishment of safe work conditions and the removal of the narrow backfill bodies over a range of about 3 m (monoliths) to more than 6 m (supercontainers). Thus, a study was carried out to identify a suitable state-of-the- art technology. Initially, techniques commonly used in the building and mining industry were compiled and grouped according to their kind of impact on the backfill. Within the scope of a benefit analysis, a catalogue of evaluation criteria was used to develop a ranking of the techniques. For example, criteria related to the space requirements of the machines and their tools, their potential to damage the waste packages and the surrounding structures, and the removability and amount of the residues. For reasons of workers’ safety, cable-and remote-control-systems are favoured. Milling is a preferred option. Based on these findings, a basic concept for waste package retrieval was developed. Using the specified technologies and procedures, the operational safety and the technical realization of waste retrieval can be assured.
of material optimization and to guarantee a future availability of adequate high-quality cement compositions.
Das Lösen der Salze erweitert zunächst geringfügig die Hohlräume. Zudem hat das Wasserglas eine Schmierwirkung. Hierdurch können dem Wasserglas nachströ¬mende Suspensionen in Risse und Poren eindringen, die ohne den Einsatz des Wasserglases nicht für die Suspensionspartikel zugänglich wären. In diesem Fall würden bei üblichen partikelgestützen Injektionsmitteln die Riss- oder Poreneingänge verstopfen und Wasser oder allgemein Baustofflösung in die feineren Wegsamkeiten eindringen. Da die Lösungen dieser Baustoffe, im Gegensatz zu den Wassergläsern keine Eigenerhärtung aufweisen, wird keine abdichtende Wirkung erzielt. Zudem kann die Füllung der feinen Wegsamkeiten mit Baustofflösung problematisch im Hinblick auf den Erfolg weiterer Injektionen sein.
Die vorteilhaften Eigenschaften des Wasserglases wurden genutzt, um partikelgestützte Injektionsmittel ohne die aufgeführten Nachteile herkömmlicher Baustoffe zu entwickeln. Geopolymere belegen, dass Puzzolane und hydraulisch-erhärtende Stoffe, wie die Aluminosilikate Metakaolin und Flugasche in Wasserglas suspendierbar sind und mit diesen zu Festkörpern reagieren. Es zeigte sich, dass auch ma¬gnesiumhaltige Stoffe, wie Magnesiumoxid und Magnesiumhydroxid sowie der extrem feine Silikastaub zur Herstellung von Wasserglas-Suspensionen geeignet sind. Zahlreiche dieser Stoffe sind mit unterschiedlicher Korngröße erhältlich. Da zudem Wassergläser über eine weite Spanne der Fließfähigkeit angeboten werden und ebenso inerte Zusatzstoffe eingesetzt werden können, bietet sich die Möglichkeit die entwickelten Baustoffe an eine Vielzahl von Aufgabenstellungen anzupassen. Die Suspensionen erlauben es größere und feine Wegsamkeiten in einem Zuge zu injizieren und sind bei Bedarf mit klassischen Injektionsmitteln auf Zementbasis, Magnesiabindern und reinen Wasserglaslösungen kombinierbar.
Standardbaustoffe haben einen hohen pH-Wert, da Portlandzementklinker Hydroxide bilden. Der pH-Wert kann in Folge von Reaktionen mit Baustoffbestandteilen oder extern zugeführten Stoffen sinken. Hoch-pH-Baustoffe haben ein hohes Widerstandspotential gegen diese pH-Wert-Abnahme. Sie enthalten vor allem Portlandzemente und feste Hydroxide, wie Calciumhydroxid. Die Endfes¬tigkeit wird meist zügig erreicht und eindeutig vom Wasser-Zement-Wert beeinflusst. Wasserglas und Natronlauge wird allgemein eine beschleunigende Wirkung zugeschrieben. Untersuchungen ergaben, dass begrenzte Mengen dem Baustoff zugegeben werden können ohne die hydraulische Förderbarkeit und damit die Eignung als Verfüllmaterial einzuschränken.
Da Zemente stets Portlandzementklinker enthalten, muss zur Gewährleistung niedriger pH-Werte der Klinkeranteil gesenkt werden. Zudem müssen entstehende Hydroxide gebunden werden, beispielsweise durch Reaktionen mit Puzzolanen und latent-hydraulische Stoffen. Die re¬aktiven Stoffe können bereits ein Bestandteil des Zements sein (z. B. Sonder- oder VLH-Zemente nach EN 14216) oder separat zugegeben werden. Reaktive Stoffe haben spezifische Kapazitäten den pH-Wert zu senken, so dass der pH-Wert des Baustoffs eingestellt werden kann. Untersuchungen ergaben, dass silikastaubhaltige Mischungen im Vergleich zu Standardbaustoffen deutlich länger erhärten. Es bildeten sich trotz äußerst hoher Wasser-Zement-Werte homogene Festkörper. Die Be¬funde sind darauf zurückzuführen, dass Silikastaub maßgeblich am Aufbau des Bin¬demittelgerüsts und am Festigkeitsgewinn beteiligt ist. Der Reaktionsumsatz war höher als nach dem k-Wert-Konzept der zementäquivalenten Wirksamkeit (DIN EN 206) zu erwarten ist. Der pH-Werte der Porenlösung konnte auf etwa 9,3 gesenkt werden.
Nach der klassischen Vorgehensweise sind Riss- oder Porensysteme eines Gesteins oder Versatzes mit partikel-haltigen und danach partikelfreien Baustoffen zu injizieren, wenn eine hohe Dichtigkeit gefordert wird. Im Kali- und Steinsalzbergbau sind die Suspensionen meist Magnesia¬binder. Aufgrund der Fähigkeit mit Salzen und Salzlösungen zu Feststoffe zu reagieren, werden häufig als partikelfreie Injektionsmittel Wassergläser eingesetzt. Wassergläser reagieren auch mit Magnesiumoxid (MgO) und vielen weiteren magnesiumhaltigen Stoffen. Dies war die Grundlage einen neuen Typ von Injektionsmitteln zu entwickeln. Bei diesen Mischungen wird im Gegensatz zu Magnesiabindern ausgehend von ihren Strömungswegen keine inerte Lösung, sondern Wasserglas in die angrenzenden Bereiche abgepresst. Eine Schmierwirkung des Wasserglases verbessert das Eindring-vermögen der Partikel in Hohlräume. Durch diese Effekte steigt das Ausmaß der Hohlraumauffüllung mit reaktivem Material und es ergibt sich die Möglichkeit die Anzahl der Injektionen zu reduzieren. Die Mischungen sind mit Magnesiabindern und reinen Wassergläsern kombinierbar und bereichern damit die Palette an Injektionsmitteln.
Mikroskopisch kleine Flüssigkeitseinschlüsse erlauben Rück¬schlüsse zur Entste¬hung und Geschichte eines Gesteins. Um Aussagen über ihre Entstehung treffen zu können, sind zuerst die Anordnung der Einschlüsse, ihre Form, die Art und Menge von Mi¬neralbestandteilen und die Größe von Gasblasen auszuwerten. Hohe Vergrößerun¬gen reduzieren die Schärfentiefe des Abbildes, so dass Details der Einschlüsse nur in einer Schnittebene erkennbar sind und die Un¬tersuchungen erschwert werden. Das Verfahren des Focus-Stackings kann in diesen Fällen hilfreich sein, da es digi¬tale Daten von Fotos, deren Schärfe¬tiefebereiche sich über¬schneiden, miteinander verrechnet. Praxistests, die an Dünnschliffen von Steinsal¬zen durchge¬führt wurden, zeigen, dass das Verfahren Bilder hoher Qualität erzeugt. Die ge¬wünschten Proben¬bereiche werden scharf dargestellt. Ein Nachteil des Ver¬fahren könnte jedoch die Zeitdauer der Rechen¬operationen sein. Zur Minimierung des Zeitaufwan¬des sollten daher Erfahrun¬gen zur Auswahl des Fotomaterials und zum Einfluss der auswähl¬baren Rechenme¬thoden auf das Stackresultat vorliegen. Für Präsenta¬tionen kann zu¬dem mit einer speziellen Software eine Bildnachbear¬beitung erfor¬derlich sein, um Artefakte der Stack-¬Berechnung und Bildfehler, die aus dem opti¬schen System resultieren, zu entfernen.
The application of the focus-stacking-technique for the examination of fluid inclusions in rocksalt
It is possible to draw conclusions from microcopically small fluid inclusions about the genesis and history of a rock. For an assessment, it is necessary to gather information about the arrangement of the inclusi¬ons, their shapes, the types and amounts of mineral components, and the size of gas bubbles. High magnifications reduce the depth of field of an image so that details of the inclusions are limited to a plane cutting through the inclusi¬ons, which mades the investigations diffi¬cult. In this case, focus stacking, also known as focal plane merging, can be a helpful technique. It proces¬ses the digital data of images with overlapping depths of fields. Practical tests, carried out on thin section of rock salt show that this technique generates high-quality-images. The desired areas of the samples are displayed in sharp focus. One drawback of this technique could be the long processing periods. Experience concerning the selection of the photographic material and the influence of the processing methods on the stack results helps to minimize the time needed. If the images are to be used for presentation pur¬poses, it can be ne¬cessary to erase artifacts of the stack-processing and to corrigate image errors, which result from the optical system, by means of a special photo finishing software.
Schlüsselwörter: Berechnungsartefakte, Bildbearbeitung, Bildqualität, Mikroskopie, Schärfentiefe, Stapeltechnik, Zeitaufwand
Keywords: Artifacts, computing time, depth of field, digital image processing, focal plane merging, focal point, focus blending, image quality, microscopy, sharpness
Based on these objectives, material requirements were specified and the development of a backfill mixture was carried out. Initially, the mix composition was optimized in the laboratory. Thereafter, the backfill process of a gallery section was simulated. The investigations illustrate that this mixture can be transported via pipelines through the shaft and drifts and would fill completely the backfill sections in the galleries. Measurements of the porosity, the pore solution composition, the thermal material properties, and the strength illustrate the compliances with the requirements and the feasibility of backfilling the disposal galleries.
----
The Belgian National Agency for Radioactive Waste and enriched Fissile Material ONDRAF/NIRAS is studying the disposal of low and medium activity level, long-lived waste (category B) and high activity, heat-generating waste (category C) in an underground facility. The repository is built at a reference depth of approximately 230 m in the Boom Clay host rock. Two shafts are built for personnel and material transfer and to provide ventilation during the construction and operation of the repository. A third shaft will be constructed for the waste transport. The shafts are connected via horizontal access galleries. The disposal galleries are constructed perpendicular to the access galleries. They are blind or dead-end galleries with a diameter of approx. 3.0 m and a length of 1,000 m. Fig. 1 shows an overview of the repository layout.
The galleries in the clay will be lined with concrete wedge blocks. In the order to transport and to support the waste packages after disposal, the galleries are outfitted with a concrete floor. It is planned to backfill the galleries section by section with a cement-based material, because grout injection is assumed to offer better opportunities for achieving the industrial performance that is required to backfill such volumes in a relatively short period of time. The current planning assumes a volume of the sections of approximately 85 m³, which will be backfilled in three and a half hours. Seals will be placed at the front-end of the disposal galleries.
The main functions of the backfill mortar are (1) isolating the waste by forming an extra barrier to the waste, (2) providing the galleries with stability and thus avoiding a gallery collapse and (3) reducing the voids in the repository which is a regulatory requirement.
As the backfill needs to realize a high filling degree, it has to show good flowability, negligible bleeding, and limited shrinkage. The grain size is limited to allow the injection of the backfill material. Another important requirement for the backfill follows from the potential requirement for waste retrievability. This means that the strength of the backfill has to be sufficient low so that the backfill can be removed at a later stage. In addition, a high porous backfill might be envisaged as it can provide a storage volume for gas generated in the repository and consequently limit the gas pressure build-up. This is in particular important for the category B waste for which the gas generation is expected to be more significant than for the category C waste.
The backfill material has to be chemically compatible with the Boom Clay host formation and any other component of the disposal system like the gallery lining and the waste disposal packages. This means that it should not unduly perturb the clay or disposal packages. Finally, the thermal conductivity of the backfill material in the category C waste disposal galleries must be high enough to allow sufficient dissipation of the heat from the category C waste into the surrounding clay. Furthermore, it has to be thermally stable under the maximum temperature that will occur in the backfill material.
---
In summer 2010, the German Federal Government launched a preliminary safety analysis to assess whether the salt dome at Gorleben is suitable to host all heat-generating radioactive waste generated by German NPPs. A repository concept was developed that also included a closure system.
Bei der Evaporation von Meerwasser bilden sich entsprechend der Abfolge ihrer Löslichkeit Carbonat, Gips, Halit sowie kalium- und magnesiumhaltige Salze. Diese Gesetzmäßigkeit erlaubt es Halit als weißes Gold von den weiteren Salzen zu trennen und auf Salzfeldern zu "ernten", wenn durch trockene Winde ausreichende Mengen an Wasser verdunsten.
Die Durchführung quantitativer Analysen erfordert die Verwendung von Referenzmaterialien. Denn auch bei einer sehr guten Reproduzierbarkeit der Messdaten kann nicht auf deren Richtigkeit geschlossen werden. Der Stoffbestand von Referenzproben ist jedoch hinsichtlich der Richtigkeit bekannt und kann zur Überprüfung der Messresultate herangezogen werden. Da zertifizierte Referenzproben nur eine begrenzte Zeit und häufig in kleinen Mengen zur Verfügung stehen, ist es vorteilhaft interne Referenzproben, sogenannten "in-house standards" zu benutzen. Sie sollten aus dem gleichen Material wie die zu untersuchenden Proben bestehen und können ebenso zur Erarbeitung von Analysenverfahren eingesetzt werden.
gypsum, halite and eventually potassium and
magnesium salts crystallize in accordance with
their solubility in water. This correlation can
be used to separate the “white gold” halite from
the other salts and to harvest the solar seasalt
in ponds, if enough water evaporates due to
dry winds. In the arid climate of Lanzarote,
the Salinas de Janubio produced in their heyday
about 10.000 tons of table and pickling salt
on an area of 45 hectares. In the ponds and
in particular on the ramparts made of basaltic
rock pebbles, which show honeycomb- or tafone-
like weathering features, lawns of gypsum
crystals grew. Most remarkable are crystals
that embedded foreign particles along crystal
planes during growth and that extend across
several layers of crystal lawns. Obviously, the
different crystal shapes, which are unusual for
gypsum, and lawn structures result from changes
of the weather and variations of the operating
conditions of the ponds.
Bei der Evaporation von Meerwasser bilden
sich entsprechend der Abfolge ihrer Löslichkeit
Carbonat, Gips, Halit sowie kalium- und magnesiumhaltige
Salze. Diese
Gesetzmäßigkeit
erlaubt es Halit als weißes Gold von den weiteren
Salzen zu trennen
und auf Salzfeldern zu
„ernten“, wenn durch trockene Winde ausreichende
Mengen an Wasser verdunsten. Im Klima
Lanzarotes wurden zu ihrer
Blütezeit in der
Salinas
de Janubio
auf einer Fläche von rund
44 Hektar jährlich etwa 10.000 Tonnen Speise-
und Pökelsalz gewonnen. In den Becken
und vor allem
an ihren Wällen aus basaltischen
Gesteinen, die tafoneartig verwittern, entstehen
Kristallrasen von Gips. Auffallend sind vor allem
Kristalle, die während ihres Wachstums
Fremdpartikel
einschlossen und über mehrere
Lagen reichen. Die unterschiedlichen, für
Gips auch ungewöhnlichen
Kristallformen und
Verwachsungen beruhen offensichtlich
auf
Änderungen
der Witterung und der Betriebsweise
der Salzbecken.
BGE TECHNOLOGY GmbH's key activities focused on the following issues:
● design of 3 repository variants for the emplacement of HLW and spent fuel. All versions take into account the requirement of retrievability. As a further option, combined emplacement with LLW/ILW was analysed.
● Development of closure concepts for all variants and optimisation of the concepts based on the results of consequence analyses
● development of geotechnical barrier concepts and demonstration of the barrier's integrities
● development of a FEP cataloque
● development of reference and alternative scenarios for the different repository variants
analysis of human intrusion scenarios
Technical Support for Conducting Studies in the Field of Radioactive Waste Management – Conceptual Design for Backfil Removal Equipment allowing Retrieval of Waste Packages
One of the problems currently investigated by ONDRAF/NIRAS in regard to waste disposal is the potential need to retrieve waste packages from the disposal galleries after these have already been backfilled. The objective of this study was to identify and conceptually design suitable technical equipment for the removal of the backfill material.
The study describes the necessary equipment with special regard to the expected boundary conditions:
● type of backfill material
● confined spaces and limited working area inside the disposal galleries
● irregular cross sections and backfill dimensions around the waste packages
● working conditions next to the waste packages (radiation, heat)
The study further covers a preliminary cost assessment for buying/developing the equipment and addresses the potential impact of the selected backfill removal equipment on the required minimum diameter of the disposal galleries.
Optimisation of the Direct Disposal Concept by Emplacing Spent Fuel Canisters in Boreholes (R&D Project DENKMAL)
Cigéo – Technical Planning Surface – Underground Connections and Underground Excavations
Feasibility Study, Basic Design and Engineering Design of a Radioactive Waste Disposal Facility in Iraq
Technical Design and ISAR Preparation for National Disposal Facility in Bulgaria
Site-specific Evaluation of Safety Issues for High-level Waste Disposal in Crystalline Rock (R&D Project URSEL)
Development of Technical Concepts for the Retrieval of Waste Packages with Heat-generating Radioactive Waste and Spent Fuel from Repositories in Salt and Clay Formations – R&D Project ERNESTA
The precipitation of dissolved trace elements in water glass is relevant with regard to the migration of toxic or radioactive elements as trace constituents. This process was analyzed by laboratory tests using brine with barium (Ba), cobalt (Co), iron (Fe), nickel (Ni), and strontium (Sr). The visual observations are comparable to those obtained from well-known crystal or chemical garden experiments, where chemical gardens result from the precipitation reactions generated by adding crystals of a soluble heavy metal salt to aqueous solutions of sodium or potassium silicate. In particular, chemical analyses demonstrate a removal of small divalent ions (Co, Ni) as well as a significant decrease in the UO2 concentration. The precipitates can comprise insoluble salts, as well as hydroxides and silicate phases. Another well-known and in water treatment frequently used property of amorphous silicates is their high sorption capacity.
DBE TECHNOLOGY GmbH was commissioned to support ONDRAF/NIRAS by carrying out feasibility studies in regard to the future operation of such a repository. The studies focus on essential parts of the conceptual repository design that need further development and confirmation of technical feasibility, on the demonstration of compliance with safety requirements, and on a cost evaluation. The feasibility studies for a hoisting system for payloads of up to 80 tons, for underground transport and waste emplacement systems, and for repository ventilation have been completed. All systems for transport and ventilation are based on state-of-the-art equipment. The shaft transport system is based on components that have been built and tested at full scale during R&D work carried out by DBE in connection with the German repository projects at Gorleben and Konrad. As a result of the analyses conducted as part of the feasibility studies, several recommendations for optimizations of the original design basis were formulated. In all cases, systems with proven technical feasibility could be designed, which also complied with the requirement for safe and cost effective technical implementation.
Retrieval requires the establishment of safe work conditions and the removal of the narrow backfill bodies over a range of about 3 m (monoliths) to more than 6 m (supercontainers). Thus, a study was carried out to identify a suitable state-of-the- art technology. Initially, techniques commonly used in the building and mining industry were compiled and grouped according to their kind of impact on the backfill. Within the scope of a benefit analysis, a catalogue of evaluation criteria was used to develop a ranking of the techniques. For example, criteria related to the space requirements of the machines and their tools, their potential to damage the waste packages and the surrounding structures, and the removability and amount of the residues. For reasons of workers’ safety, cable-and remote-control-systems are favoured. Milling is a preferred option. Based on these findings, a basic concept for waste package retrieval was developed. Using the specified technologies and procedures, the operational safety and the technical realization of waste retrieval can be assured.
of material optimization and to guarantee a future availability of adequate high-quality cement compositions.
Das Lösen der Salze erweitert zunächst geringfügig die Hohlräume. Zudem hat das Wasserglas eine Schmierwirkung. Hierdurch können dem Wasserglas nachströ¬mende Suspensionen in Risse und Poren eindringen, die ohne den Einsatz des Wasserglases nicht für die Suspensionspartikel zugänglich wären. In diesem Fall würden bei üblichen partikelgestützen Injektionsmitteln die Riss- oder Poreneingänge verstopfen und Wasser oder allgemein Baustofflösung in die feineren Wegsamkeiten eindringen. Da die Lösungen dieser Baustoffe, im Gegensatz zu den Wassergläsern keine Eigenerhärtung aufweisen, wird keine abdichtende Wirkung erzielt. Zudem kann die Füllung der feinen Wegsamkeiten mit Baustofflösung problematisch im Hinblick auf den Erfolg weiterer Injektionen sein.
Die vorteilhaften Eigenschaften des Wasserglases wurden genutzt, um partikelgestützte Injektionsmittel ohne die aufgeführten Nachteile herkömmlicher Baustoffe zu entwickeln. Geopolymere belegen, dass Puzzolane und hydraulisch-erhärtende Stoffe, wie die Aluminosilikate Metakaolin und Flugasche in Wasserglas suspendierbar sind und mit diesen zu Festkörpern reagieren. Es zeigte sich, dass auch ma¬gnesiumhaltige Stoffe, wie Magnesiumoxid und Magnesiumhydroxid sowie der extrem feine Silikastaub zur Herstellung von Wasserglas-Suspensionen geeignet sind. Zahlreiche dieser Stoffe sind mit unterschiedlicher Korngröße erhältlich. Da zudem Wassergläser über eine weite Spanne der Fließfähigkeit angeboten werden und ebenso inerte Zusatzstoffe eingesetzt werden können, bietet sich die Möglichkeit die entwickelten Baustoffe an eine Vielzahl von Aufgabenstellungen anzupassen. Die Suspensionen erlauben es größere und feine Wegsamkeiten in einem Zuge zu injizieren und sind bei Bedarf mit klassischen Injektionsmitteln auf Zementbasis, Magnesiabindern und reinen Wasserglaslösungen kombinierbar.
Standardbaustoffe haben einen hohen pH-Wert, da Portlandzementklinker Hydroxide bilden. Der pH-Wert kann in Folge von Reaktionen mit Baustoffbestandteilen oder extern zugeführten Stoffen sinken. Hoch-pH-Baustoffe haben ein hohes Widerstandspotential gegen diese pH-Wert-Abnahme. Sie enthalten vor allem Portlandzemente und feste Hydroxide, wie Calciumhydroxid. Die Endfes¬tigkeit wird meist zügig erreicht und eindeutig vom Wasser-Zement-Wert beeinflusst. Wasserglas und Natronlauge wird allgemein eine beschleunigende Wirkung zugeschrieben. Untersuchungen ergaben, dass begrenzte Mengen dem Baustoff zugegeben werden können ohne die hydraulische Förderbarkeit und damit die Eignung als Verfüllmaterial einzuschränken.
Da Zemente stets Portlandzementklinker enthalten, muss zur Gewährleistung niedriger pH-Werte der Klinkeranteil gesenkt werden. Zudem müssen entstehende Hydroxide gebunden werden, beispielsweise durch Reaktionen mit Puzzolanen und latent-hydraulische Stoffen. Die re¬aktiven Stoffe können bereits ein Bestandteil des Zements sein (z. B. Sonder- oder VLH-Zemente nach EN 14216) oder separat zugegeben werden. Reaktive Stoffe haben spezifische Kapazitäten den pH-Wert zu senken, so dass der pH-Wert des Baustoffs eingestellt werden kann. Untersuchungen ergaben, dass silikastaubhaltige Mischungen im Vergleich zu Standardbaustoffen deutlich länger erhärten. Es bildeten sich trotz äußerst hoher Wasser-Zement-Werte homogene Festkörper. Die Be¬funde sind darauf zurückzuführen, dass Silikastaub maßgeblich am Aufbau des Bin¬demittelgerüsts und am Festigkeitsgewinn beteiligt ist. Der Reaktionsumsatz war höher als nach dem k-Wert-Konzept der zementäquivalenten Wirksamkeit (DIN EN 206) zu erwarten ist. Der pH-Werte der Porenlösung konnte auf etwa 9,3 gesenkt werden.
Nach der klassischen Vorgehensweise sind Riss- oder Porensysteme eines Gesteins oder Versatzes mit partikel-haltigen und danach partikelfreien Baustoffen zu injizieren, wenn eine hohe Dichtigkeit gefordert wird. Im Kali- und Steinsalzbergbau sind die Suspensionen meist Magnesia¬binder. Aufgrund der Fähigkeit mit Salzen und Salzlösungen zu Feststoffe zu reagieren, werden häufig als partikelfreie Injektionsmittel Wassergläser eingesetzt. Wassergläser reagieren auch mit Magnesiumoxid (MgO) und vielen weiteren magnesiumhaltigen Stoffen. Dies war die Grundlage einen neuen Typ von Injektionsmitteln zu entwickeln. Bei diesen Mischungen wird im Gegensatz zu Magnesiabindern ausgehend von ihren Strömungswegen keine inerte Lösung, sondern Wasserglas in die angrenzenden Bereiche abgepresst. Eine Schmierwirkung des Wasserglases verbessert das Eindring-vermögen der Partikel in Hohlräume. Durch diese Effekte steigt das Ausmaß der Hohlraumauffüllung mit reaktivem Material und es ergibt sich die Möglichkeit die Anzahl der Injektionen zu reduzieren. Die Mischungen sind mit Magnesiabindern und reinen Wassergläsern kombinierbar und bereichern damit die Palette an Injektionsmitteln.
Mikroskopisch kleine Flüssigkeitseinschlüsse erlauben Rück¬schlüsse zur Entste¬hung und Geschichte eines Gesteins. Um Aussagen über ihre Entstehung treffen zu können, sind zuerst die Anordnung der Einschlüsse, ihre Form, die Art und Menge von Mi¬neralbestandteilen und die Größe von Gasblasen auszuwerten. Hohe Vergrößerun¬gen reduzieren die Schärfentiefe des Abbildes, so dass Details der Einschlüsse nur in einer Schnittebene erkennbar sind und die Un¬tersuchungen erschwert werden. Das Verfahren des Focus-Stackings kann in diesen Fällen hilfreich sein, da es digi¬tale Daten von Fotos, deren Schärfe¬tiefebereiche sich über¬schneiden, miteinander verrechnet. Praxistests, die an Dünnschliffen von Steinsal¬zen durchge¬führt wurden, zeigen, dass das Verfahren Bilder hoher Qualität erzeugt. Die ge¬wünschten Proben¬bereiche werden scharf dargestellt. Ein Nachteil des Ver¬fahren könnte jedoch die Zeitdauer der Rechen¬operationen sein. Zur Minimierung des Zeitaufwan¬des sollten daher Erfahrun¬gen zur Auswahl des Fotomaterials und zum Einfluss der auswähl¬baren Rechenme¬thoden auf das Stackresultat vorliegen. Für Präsenta¬tionen kann zu¬dem mit einer speziellen Software eine Bildnachbear¬beitung erfor¬derlich sein, um Artefakte der Stack-¬Berechnung und Bildfehler, die aus dem opti¬schen System resultieren, zu entfernen.
The application of the focus-stacking-technique for the examination of fluid inclusions in rocksalt
It is possible to draw conclusions from microcopically small fluid inclusions about the genesis and history of a rock. For an assessment, it is necessary to gather information about the arrangement of the inclusi¬ons, their shapes, the types and amounts of mineral components, and the size of gas bubbles. High magnifications reduce the depth of field of an image so that details of the inclusions are limited to a plane cutting through the inclusi¬ons, which mades the investigations diffi¬cult. In this case, focus stacking, also known as focal plane merging, can be a helpful technique. It proces¬ses the digital data of images with overlapping depths of fields. Practical tests, carried out on thin section of rock salt show that this technique generates high-quality-images. The desired areas of the samples are displayed in sharp focus. One drawback of this technique could be the long processing periods. Experience concerning the selection of the photographic material and the influence of the processing methods on the stack results helps to minimize the time needed. If the images are to be used for presentation pur¬poses, it can be ne¬cessary to erase artifacts of the stack-processing and to corrigate image errors, which result from the optical system, by means of a special photo finishing software.
Schlüsselwörter: Berechnungsartefakte, Bildbearbeitung, Bildqualität, Mikroskopie, Schärfentiefe, Stapeltechnik, Zeitaufwand
Keywords: Artifacts, computing time, depth of field, digital image processing, focal plane merging, focal point, focus blending, image quality, microscopy, sharpness
Based on these objectives, material requirements were specified and the development of a backfill mixture was carried out. Initially, the mix composition was optimized in the laboratory. Thereafter, the backfill process of a gallery section was simulated. The investigations illustrate that this mixture can be transported via pipelines through the shaft and drifts and would fill completely the backfill sections in the galleries. Measurements of the porosity, the pore solution composition, the thermal material properties, and the strength illustrate the compliances with the requirements and the feasibility of backfilling the disposal galleries.
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The Belgian National Agency for Radioactive Waste and enriched Fissile Material ONDRAF/NIRAS is studying the disposal of low and medium activity level, long-lived waste (category B) and high activity, heat-generating waste (category C) in an underground facility. The repository is built at a reference depth of approximately 230 m in the Boom Clay host rock. Two shafts are built for personnel and material transfer and to provide ventilation during the construction and operation of the repository. A third shaft will be constructed for the waste transport. The shafts are connected via horizontal access galleries. The disposal galleries are constructed perpendicular to the access galleries. They are blind or dead-end galleries with a diameter of approx. 3.0 m and a length of 1,000 m. Fig. 1 shows an overview of the repository layout.
The galleries in the clay will be lined with concrete wedge blocks. In the order to transport and to support the waste packages after disposal, the galleries are outfitted with a concrete floor. It is planned to backfill the galleries section by section with a cement-based material, because grout injection is assumed to offer better opportunities for achieving the industrial performance that is required to backfill such volumes in a relatively short period of time. The current planning assumes a volume of the sections of approximately 85 m³, which will be backfilled in three and a half hours. Seals will be placed at the front-end of the disposal galleries.
The main functions of the backfill mortar are (1) isolating the waste by forming an extra barrier to the waste, (2) providing the galleries with stability and thus avoiding a gallery collapse and (3) reducing the voids in the repository which is a regulatory requirement.
As the backfill needs to realize a high filling degree, it has to show good flowability, negligible bleeding, and limited shrinkage. The grain size is limited to allow the injection of the backfill material. Another important requirement for the backfill follows from the potential requirement for waste retrievability. This means that the strength of the backfill has to be sufficient low so that the backfill can be removed at a later stage. In addition, a high porous backfill might be envisaged as it can provide a storage volume for gas generated in the repository and consequently limit the gas pressure build-up. This is in particular important for the category B waste for which the gas generation is expected to be more significant than for the category C waste.
The backfill material has to be chemically compatible with the Boom Clay host formation and any other component of the disposal system like the gallery lining and the waste disposal packages. This means that it should not unduly perturb the clay or disposal packages. Finally, the thermal conductivity of the backfill material in the category C waste disposal galleries must be high enough to allow sufficient dissipation of the heat from the category C waste into the surrounding clay. Furthermore, it has to be thermally stable under the maximum temperature that will occur in the backfill material.
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In summer 2010, the German Federal Government launched a preliminary safety analysis to assess whether the salt dome at Gorleben is suitable to host all heat-generating radioactive waste generated by German NPPs. A repository concept was developed that also included a closure system.
Bei der Evaporation von Meerwasser bilden sich entsprechend der Abfolge ihrer Löslichkeit Carbonat, Gips, Halit sowie kalium- und magnesiumhaltige Salze. Diese Gesetzmäßigkeit erlaubt es Halit als weißes Gold von den weiteren Salzen zu trennen und auf Salzfeldern zu "ernten", wenn durch trockene Winde ausreichende Mengen an Wasser verdunsten.
Die Durchführung quantitativer Analysen erfordert die Verwendung von Referenzmaterialien. Denn auch bei einer sehr guten Reproduzierbarkeit der Messdaten kann nicht auf deren Richtigkeit geschlossen werden. Der Stoffbestand von Referenzproben ist jedoch hinsichtlich der Richtigkeit bekannt und kann zur Überprüfung der Messresultate herangezogen werden. Da zertifizierte Referenzproben nur eine begrenzte Zeit und häufig in kleinen Mengen zur Verfügung stehen, ist es vorteilhaft interne Referenzproben, sogenannten "in-house standards" zu benutzen. Sie sollten aus dem gleichen Material wie die zu untersuchenden Proben bestehen und können ebenso zur Erarbeitung von Analysenverfahren eingesetzt werden.
gypsum, halite and eventually potassium and
magnesium salts crystallize in accordance with
their solubility in water. This correlation can
be used to separate the “white gold” halite from
the other salts and to harvest the solar seasalt
in ponds, if enough water evaporates due to
dry winds. In the arid climate of Lanzarote,
the Salinas de Janubio produced in their heyday
about 10.000 tons of table and pickling salt
on an area of 45 hectares. In the ponds and
in particular on the ramparts made of basaltic
rock pebbles, which show honeycomb- or tafone-
like weathering features, lawns of gypsum
crystals grew. Most remarkable are crystals
that embedded foreign particles along crystal
planes during growth and that extend across
several layers of crystal lawns. Obviously, the
different crystal shapes, which are unusual for
gypsum, and lawn structures result from changes
of the weather and variations of the operating
conditions of the ponds.
Bei der Evaporation von Meerwasser bilden
sich entsprechend der Abfolge ihrer Löslichkeit
Carbonat, Gips, Halit sowie kalium- und magnesiumhaltige
Salze. Diese
Gesetzmäßigkeit
erlaubt es Halit als weißes Gold von den weiteren
Salzen zu trennen
und auf Salzfeldern zu
„ernten“, wenn durch trockene Winde ausreichende
Mengen an Wasser verdunsten. Im Klima
Lanzarotes wurden zu ihrer
Blütezeit in der
Salinas
de Janubio
auf einer Fläche von rund
44 Hektar jährlich etwa 10.000 Tonnen Speise-
und Pökelsalz gewonnen. In den Becken
und vor allem
an ihren Wällen aus basaltischen
Gesteinen, die tafoneartig verwittern, entstehen
Kristallrasen von Gips. Auffallend sind vor allem
Kristalle, die während ihres Wachstums
Fremdpartikel
einschlossen und über mehrere
Lagen reichen. Die unterschiedlichen, für
Gips auch ungewöhnlichen
Kristallformen und
Verwachsungen beruhen offensichtlich
auf
Änderungen
der Witterung und der Betriebsweise
der Salzbecken.
Nowadays, graduation towers are centres of recreation in spa towns. The particle inclusions of the thornstone demonstrate the cleaning of the air. Wa¬ter evapora¬tion cools the air and the microclimate with fresh, salty aerosols is used for therapeutic inhalations. The trickling of brine creates a relaxing atmosphere and the brines can be used for bath therapies. In addition, the towers are technical monuments, tourist attractions, and event locations. Visitors have the opportunity to learn principles of solution mining and salt processing.
ONDRAF/NIRAS the competent Belgian organization for radioactive waste management proposes to build a GDF in a poorly indurated clay host rock. Low- and intermediate-level radioactive waste (B-waste) will be conditioned in concrete monoliths B and high-level, heat-generating waste (C-waste) in so-called Supercontainers (SC). The SCs consist of overpacks embedded in concrete and a steel envelope. The two types of waste packages will be disposed of in separate fields of the future GDF.
In the framework of a technical support project with ONDRAF/NIRAS, DBE TECHNOLOGY GmbH has developed reference backfilling materials. It is planned to backfill the remaining voids inside the disposal galleries stepwise after the emplacement of a specified number of waste packages. As the space underground is restricted and to generally minimize operational activities underground, the preferred concept is to mix the backfill above ground and to pump the mixture via a piping system into the backfill segments. Consequently the backfill material has to remain in a flowable condition for the time needed for the transport process. After filling the segments, the backfilling material shall harden without swelling or significant shrinkage to homogenous bodies. Additionally, according to the current ONDRAF/NIRAS retrievability concept, the strength of the backfilling bodies has to be low enough to allow a later excavation of waste packages should that be required.
Initially, these general tasks suggest the development of a universally usable material for the backfilling of all galleries. Nonetheless, the different characteristics of the B- and C-waste packages and differences in the designs of the emplacement fields require the specification of individual catalogues with many common, but also several different material requirements for the development of backfilling material for B- and C-waste disposal galleries.
The requirement of chemical compatibility makes it necessary to use a cement-based backfill and all potential mixtures must meet the criteria for hydraulic backfilling. However, particularly high demands have to be specified for the time of workability and flowability of the backfill of the C-waste field due to its large extension resulting in pipeline lengths of up to 4000 m.
Other deviating requirements for material properties of the two backfill types originate from the long-term behavior of the two waste types. For instance, the pore volume of the B-waste backfill must be large enough to allow gas flow and thereby minimize a possible gas pressure built-up, due to the degradation of organics. In contrast, a lower porosity is favored to achieve a higher thermal conductivity for a better dissipation and removal of the C-waste decay heat. Moreover, for the C-waste backfill a minimum pH value was prescribed with the objective to guarantee a long-term passivation and corrosion resistance of the SC steel surface.
After defining the requirement catalogues, the next step was dedicated to the selection of suitable raw materials based on the knowledge of technological properties of available high-quality materials. For instance, Portland limestone cement was selected as the binder of the B-waste backfill and a Portland cement for the C-waste backfill to achieve the required high pH value in this waste field. Another example is the use of sand aggregate, which is allowed in the B-waste field, while only limestone powder and aggregate were considered for the development of the C-waste backfill to safely prevent alkali-silica reactions at elevated temperatures.
Usually, the time span of workability of low-porosity Portland cement mixtures is limited, whereas the backfilling of the voids in the C-waste field require an exceptional long potlife. This example demonstrates that different requirements often have contrary consequences for the material selection and vice versa. Consequently, one focus of the backfill development was to identify compositional ranges that guarantee the respective material property. Finally, a combination of the individual „conformity fields“ results in the optimal solution for the standard operating conditions as well as a compositional range that guarantees compliance with the required material specifications. These interrelations and the general strategy used to reach the optimal solution will be demonstrated for the two development lines of the B- and C-waste backfill. The principle strategy can be adapted to many underground repositories and conventional mines.
During the first construction phase only the central service area and the galleries of the B-waste emplacement field will be excavated. After the end of disposal, backfilling and closure operations in the B-waste part, the C-waste part will be excavated and disposal and backfilling operations will be carried out.
According to the Belgian reference concept, B-waste will be conditioned in concrete monoliths and C-waste in so-called supercontainers (SCs). The waste packages (WPs) will be transported on trolleys of a hybrid rail-wheel configuration using battery driven locomotives. Backfilling of the disposal galleries after WP emplacement is supposed to be carried out in segments of approximately 50 m length. To increase the level of operational safety in the repository, it is planned to strictly separate disposal and backfilling operations.
Considering the framework conditions at the site, it was necessary to develop a specific backfill material, taking into account the particular material requirements resulting from the characteristics of a clay host rock formation and a suitable backfilling technique. The current reference solution is to mix the backfill at the surface and then to pump the mixture through a pipeline distribution system installed inside the access shaft and the galleries.
Based on the boundary conditions derived from the waste transport system, the backfill production and distribution system, the WP production, and certain strategic decisions by the Belgian Waste Management Organization, ONDRAF/NIRAS, a numerical model has been developed to simulate the operational activities during emplacement and backfilling. Results of the simulation demonstrate the influence of certain parameters like working time, dimensions and number of disposal galleries in operation, size of buffer storage for WPs, etc. on the WP emplacement rates. The outcome of the simulation will be used to optimize the emplacement and backfilling concept in a way that the WP emplacement rate does not fall behind the WP production rate, which would prolong the minimum operational period of the repository. At the same time the results will help to prevent significant over capacities in regard to emplacement and backfilling or buffer storage to economically optimize the operation of the repository.
The DWPs will be transported on trolleys of a hybrid rail-wheel configuration using battery driven locomotives. After the emplacement of a specified number of DWPs a formwork will be installed and voids will be backfilled. It is foreseen to mix the backfill at the surface and to pump the material through a pipeline distribution system.
An insufficient performance of backfill processes and/or emplacement rates that are significantly smaller than the production rate of the DWPs would cause inter-ruptions in DWP production. The total operational phase of the facilities would be extended and associated costs increased. The relation between DWP production rate and emplacement rate is therefore of great importance. To investigate the general feasibility of the planned operation and to identify bottlenecks, areas for optimization etc., DBE TECHNOLOGY GmbH carried out simulations of the future operation. The simulation model considers all relevant boundary conditions, e.g. the disposal facility design, the planned transport and backfill techniques, and strategic decisions of ONDRAF/NIRAS relating to the operation of the facilities. For example, one scenario considered to start the emplacement of the DWPs in the rearmost parts of the emplacement fields, and to carry out the construction of the plugs at the entrance of the disposal galleries, and the backfilling of the access galleries after backfilling of all disposal galleries.
According to the results of the simulations, at the be-ginning of the disposal operation the production rate will marginally exceed the rate of emplacement due to the longer transport routes. Consequently, the buffer is filled up with monoliths, however, this does not lead to a reduction of DWP production. Before the capacity of the buffer storage is exceeded, the decrease of transport distances and times with disposal operations advancing towards the shaft leads to an increased emplacement rate. The buffer stock is reduced and all new monoliths can be emplaced according to the DWP production rate.
Failures of the emplacement and backfilling tech-nique do not have significant effects for emplacement, because the buffer facility has a sufficient capacity. In addition, a variety of operational measures can be real-ized to raise the speed of emplacement and backfilling after resumption of the works, e.g. a temporary change from single shift to two shift operation. Consequently, there seems to be little risk that the average emplacement rate will fall back behind the DWP production rates and cause an extension of the total disposal operation period. According to the simulations, the emplacement of the monoliths will last slightly less than 13 years.
The construction of the plugs and a final seal is still at the planning stage and no safe statements can be made to the time period of their implementation. However, a little more than 400 work days (~1.6 calendar years) can be estimated for the backfilling of the access galleries and their connecting galleries of the B waste field, if the works in the access galleries can be carried out simultaneously.
After closure of the B waste field, the second wing of the disposal facility will be constructed and the supercontainers will be emplaced in analogy to the B waste monoliths. Further simulation studies will examine the effects of the major differences between the planned operation of the B waste part of the disposal facility and its C waste part.
During the first construction phase only the central service area and the galleries of the B-waste emplacement field will be excavated. After the end of disposal, backfilling and closure operations in the B-waste part, the C-waste part will be excavated and disposal and backfilling operations will be carried out.
According to the Belgian reference concept, B-waste will be conditioned in concrete monoliths and C-waste in so-called supercontainers (SCs). The waste packages (WPs) will be transported on trolleys of a hybrid rail-wheel configuration using battery driven locomotives. Backfilling of the disposal galleries after WP emplacement is supposed to be carried out in segments of approximately 50 m length. To increase the level of operational safety in the repository, it is planned to strictly separate disposal and backfilling operations.
Considering the framework conditions at the site, it was necessary to develop a specific backfill material, taking into account the particular material requirements resulting from the characteristics of a clay host rock formation and a suitable backfilling technique. The current reference solution is to mix the backfill at the surface and then to pump the mixture through a pipeline distribution system installed inside the access shaft and the galleries.
Based on the boundary conditions derived from the waste transport system, the backfill production and distribution system, the WP production, and certain strategic decisions by the Belgian Waste Management Organization, ONDRAF/NIRAS, a numerical model has been developed to simulate the operational activities during emplacement and backfilling. Results of the simulation demonstrate the influence of certain parameters like working time, dimensions and number of disposal galleries in operation, size of buffer storage for WPs, etc. on the WP emplacement rates. The outcome of the simulation will be used to optimize the emplacement and backfilling concept in a way that the WP emplacement rate does not fall behind the WP production rate, which would prolong the minimum operational period of the repository. At the same time the results will help to prevent significant over capacities in regard to emplacement and backfilling or buffer storage to economically optimize the operation of the repository.
To improve the knowledge about biodegradation, this process was investigated by laboratory experiments and in the Wadden Sea tidal flats of Northern Germany.
Zur Bestimmung der Reaktionskinetik von Schichtsilikaten mit hochsalinaren Lösungen begannen 1996 Versuchsreihen mit einer Vielzahl von monomineralischen Tonen und Tonmineralgruppen, die derzeit noch andauern. ....
Nach BVOT wurde der Bohrlochkopf mit Absperrvorrichtungen versehen (vgl. API RP53). Die Druckstufen der Preventer müssen den höchsten zu erwartenden Kopfdrücken genügen. .... Da der Druck von Lösungs- und Gasreservoiren identisch dem auflagernden Gebirgsdruck ist, wurde eine Ausrüstung entsprechend der Nenndruckstufe 3M eingesetzt. Dies entspricht 3000 psi bw. etwa 210 bar (21 MPa).
Zur Trennung der Gas- und Flüssigkeitsvolumina diente ein Separator, der über eine Choke-Line und ein Choke-Manifold an den Bohrlochkopf angeschlossen war. Die Quantifizierung des Gases erfolgte mit einem handelsüblichen Zähler für Feuchtgas, während die Salzlösung in einem Tank gesammelt ...
Zur Klärung der geologischen Lagerungsverhältnisse und der Bohrrichtung war es erforderlich, die Gesteinskerne regelmäßig zu orientieren. Anfänglich wurde das in den 70er Jahren entwickelte Verfahren des mechanischen Single- und Multishot-Systems (MMS) eingesetzt. Hierzu wird das Kompass-Pendelteil mit kardanisch aufgehängtem Kompass und integrierter Kamera, auf das obere Innenkernrohr geschraubt und der Winkel der Messsonde zum sogenannten Hauptmesser, das innerhalb der Kernritzhülse im unteren Innenkernrohr sitzt, bestimmt. Während des Bohrfortschritts wandert der Bohrkern in das untere Innenkernrohr und wird durch drei in unterschiedlichen Winkeln zueinander stehenden Ritzmessern oberflächlich angeritzt. Die Bohrung wird nach definierten Abständen angehalten und der Kompass mit Angaben über Neigung und Azimut der Bohrung sowie dem momentanen Winkel der Messsonde zum Hauptmesser fotografisch festgehalten. ....