We demonstrate effects of Cs ions on the melting transition and molecular structure of molten FLi... more We demonstrate effects of Cs ions on the melting transition and molecular structure of molten FLiNaK (a eutectic mixture of LiF-NaF-KF). FLiNaK is a commonly studied multi-component model system, which represents the physical and chemical behavior of fluoride salts for nuclear energy applications. Dissolution of nuclear fuels leads to the formation of fission products directly in the molten salt. Cs is one of the most important fission products, due to its relative abundance, long half life, and potential environmental and health effects. Here, we determine the molecular structure and phase equilibria of dissolved Cs in FLiNaK by a combination of X-ray diffraction, X-ray total scattering, ab initio molecular dynamics calculations, and computational thermodynamics. Although Cs ions have a relatively large size, we did not find significant evidence that they disrupt the existing molecular structure of the liquid. We found good agreement between our simulated and measured structure fac...
Abstract Molten salt reactors (MSRs) are being investigated as a possible source of 99Mo for medi... more Abstract Molten salt reactors (MSRs) are being investigated as a possible source of 99Mo for medical uses. This paper describes computational modeling being performed to determine the feasibility for use of several MSR concepts in 99Mo production: the Molten Salt Breeder Reactor (MSBR), the Molten Salt Demonstration Reactor (MSDR), and the Molten Salt Reactor Experiment (MSRE). This modeling is accomplished with SCALE/TRITON using a three-mixture system and estimated removal terms. Results showed that the MSBR, MSDR and MSRE were capable of supplying an estimated 35,800,000, 13,700,000, and 132,000 six-day Ci/week of 99Mo, respectively, which is far more than the global demand. A range of operating parameters has been determined in which each reactor type is expected to have sufficient production capability to meet global demand.
Bioenergy with carbon capture and storage (BECCS) can sequester atmospheric CO2, while producing ... more Bioenergy with carbon capture and storage (BECCS) can sequester atmospheric CO2, while producing electricity. The CO2 avoidance cost (CAC) is used to calculate the marginal cost of avoided CO2 emissions for BECCS as compared to other established energy technologies. A comparative analysis using four different reference-case power plants for CAC calculations is performed here to evaluate the CO2 avoidance cost of BECCS implementation. Results from this work demonstrate that BECCS can generate electricity at costs competitive with other neutral emissions technologies, while simultaneously removing CO2 from the atmosphere. Approximately 73% of current coal power plants are approaching retirement by the year 2035 in the U.S. After considering CO2 sequestered from the atmosphere and coal power plant CO2 emissions displaced by BECCS, CO2 emissions can be reduced by 1.4 billion tonnes per year in the U.S. alone at a cost of $88 to $116 per tonne of CO2 removed from the atmosphere, for 10% ...
The resurgence of the Molten-Salt Nuclear Reactors (MSR) creates interesting problems in molten-s... more The resurgence of the Molten-Salt Nuclear Reactors (MSR) creates interesting problems in molten-salt chemistry. As MSRs operate, the composition and physical properties of salts change because of fission and corrosion. Since Cr is the principal corrosion product and NaCl is a common constituent, we studied the atomic structure of molten NaCl-CrCl3. We found networks of CrCl3− 6 octahedra and an intermediate-range order with nonmonotonic temperature behavior in a remarkable agreement between measurements and ab initio simulations. Even though the corrosion results in minute quantities of dissolved Cr, the speciation of Cr could lead to changes in molten-salt properties in nuclear and solar salts. In particular, we found a much lower than expected melting temperature and a broad metastable liquid-solid coexistence phase. The availability of Cr isotopes with very different neutron-scattering properties makes Cr an ideal model multi-valent ion for experimental validation of new atomisti...
Bioenergy with carbon capture and sequestration (BECCS) is one strategy to remove CO2 from the at... more Bioenergy with carbon capture and sequestration (BECCS) is one strategy to remove CO2 from the atmosphere. To assess the potential scale and cost of CO2 sequestration from BECCS in the US, this analysis models carbon efficiencies and costs of biomass production, delivery, power generation, and CO2 capture and sequestration in saline formations. The analysis includes two biomass supply scenarios (near-term and long-term), two biomass logistics scenarios (conventional and pelletized), two generation technologies (pulverized combustion and integrated gasification combined cycle), and three cost accounting scenarios (gross cost, net cost after electricity revenues, and net cost after electricity revenues with avoided emissions from conventional power generation). Results show cost Mg-1 CO2 as a function of CO2 sequestered (simulating capture up to 90% of total CO2 sequestration potential) and associated spatial distribution of resources and generation locations for the array of scenario...
International Journal of Analytical Chemistry, 2018
We describe a new approach for high sensitivity and real-time online measurements to monitor the ... more We describe a new approach for high sensitivity and real-time online measurements to monitor the kinetics in the processing of nuclear materials and other chemical reactions. Mid infrared (Mid-IR) quantum cascade laser (QCL) high-resolution spectroscopy was used for rapid and continuous sampling of nitrates in aqueous and organic reactive systems, using pattern recognition analysis and high sensitivity to detect and identify chemical species. In this standoff or off-set method, the collection of a sample for analysis is not required. To perform the analysis, a flow cell was used for in situ sampling of a liquid slipstream. A prototype was designed based on attenuated total reflection (ATR) coupled with the QCL beam to detect and identify chemical changes and be deployed in hostile environments, either radiological or chemical. The limit of detection (LOD) and the limit of quantification (LOQ) at 3σ for hydroxylamine nitrate ranged from 0.3 to 3 and from 3.5 to 10 g·L−1, respectively...
We demonstrate effects of Cs ions on the melting transition and molecular structure of molten FLi... more We demonstrate effects of Cs ions on the melting transition and molecular structure of molten FLiNaK (a eutectic mixture of LiF-NaF-KF). FLiNaK is a commonly studied multi-component model system, which represents the physical and chemical behavior of fluoride salts for nuclear energy applications. Dissolution of nuclear fuels leads to the formation of fission products directly in the molten salt. Cs is one of the most important fission products, due to its relative abundance, long half life, and potential environmental and health effects. Here, we determine the molecular structure and phase equilibria of dissolved Cs in FLiNaK by a combination of X-ray diffraction, X-ray total scattering, ab initio molecular dynamics calculations, and computational thermodynamics. Although Cs ions have a relatively large size, we did not find significant evidence that they disrupt the existing molecular structure of the liquid. We found good agreement between our simulated and measured structure fac...
Abstract Molten salt reactors (MSRs) are being investigated as a possible source of 99Mo for medi... more Abstract Molten salt reactors (MSRs) are being investigated as a possible source of 99Mo for medical uses. This paper describes computational modeling being performed to determine the feasibility for use of several MSR concepts in 99Mo production: the Molten Salt Breeder Reactor (MSBR), the Molten Salt Demonstration Reactor (MSDR), and the Molten Salt Reactor Experiment (MSRE). This modeling is accomplished with SCALE/TRITON using a three-mixture system and estimated removal terms. Results showed that the MSBR, MSDR and MSRE were capable of supplying an estimated 35,800,000, 13,700,000, and 132,000 six-day Ci/week of 99Mo, respectively, which is far more than the global demand. A range of operating parameters has been determined in which each reactor type is expected to have sufficient production capability to meet global demand.
Bioenergy with carbon capture and storage (BECCS) can sequester atmospheric CO2, while producing ... more Bioenergy with carbon capture and storage (BECCS) can sequester atmospheric CO2, while producing electricity. The CO2 avoidance cost (CAC) is used to calculate the marginal cost of avoided CO2 emissions for BECCS as compared to other established energy technologies. A comparative analysis using four different reference-case power plants for CAC calculations is performed here to evaluate the CO2 avoidance cost of BECCS implementation. Results from this work demonstrate that BECCS can generate electricity at costs competitive with other neutral emissions technologies, while simultaneously removing CO2 from the atmosphere. Approximately 73% of current coal power plants are approaching retirement by the year 2035 in the U.S. After considering CO2 sequestered from the atmosphere and coal power plant CO2 emissions displaced by BECCS, CO2 emissions can be reduced by 1.4 billion tonnes per year in the U.S. alone at a cost of $88 to $116 per tonne of CO2 removed from the atmosphere, for 10% ...
The resurgence of the Molten-Salt Nuclear Reactors (MSR) creates interesting problems in molten-s... more The resurgence of the Molten-Salt Nuclear Reactors (MSR) creates interesting problems in molten-salt chemistry. As MSRs operate, the composition and physical properties of salts change because of fission and corrosion. Since Cr is the principal corrosion product and NaCl is a common constituent, we studied the atomic structure of molten NaCl-CrCl3. We found networks of CrCl3− 6 octahedra and an intermediate-range order with nonmonotonic temperature behavior in a remarkable agreement between measurements and ab initio simulations. Even though the corrosion results in minute quantities of dissolved Cr, the speciation of Cr could lead to changes in molten-salt properties in nuclear and solar salts. In particular, we found a much lower than expected melting temperature and a broad metastable liquid-solid coexistence phase. The availability of Cr isotopes with very different neutron-scattering properties makes Cr an ideal model multi-valent ion for experimental validation of new atomisti...
Bioenergy with carbon capture and sequestration (BECCS) is one strategy to remove CO2 from the at... more Bioenergy with carbon capture and sequestration (BECCS) is one strategy to remove CO2 from the atmosphere. To assess the potential scale and cost of CO2 sequestration from BECCS in the US, this analysis models carbon efficiencies and costs of biomass production, delivery, power generation, and CO2 capture and sequestration in saline formations. The analysis includes two biomass supply scenarios (near-term and long-term), two biomass logistics scenarios (conventional and pelletized), two generation technologies (pulverized combustion and integrated gasification combined cycle), and three cost accounting scenarios (gross cost, net cost after electricity revenues, and net cost after electricity revenues with avoided emissions from conventional power generation). Results show cost Mg-1 CO2 as a function of CO2 sequestered (simulating capture up to 90% of total CO2 sequestration potential) and associated spatial distribution of resources and generation locations for the array of scenario...
International Journal of Analytical Chemistry, 2018
We describe a new approach for high sensitivity and real-time online measurements to monitor the ... more We describe a new approach for high sensitivity and real-time online measurements to monitor the kinetics in the processing of nuclear materials and other chemical reactions. Mid infrared (Mid-IR) quantum cascade laser (QCL) high-resolution spectroscopy was used for rapid and continuous sampling of nitrates in aqueous and organic reactive systems, using pattern recognition analysis and high sensitivity to detect and identify chemical species. In this standoff or off-set method, the collection of a sample for analysis is not required. To perform the analysis, a flow cell was used for in situ sampling of a liquid slipstream. A prototype was designed based on attenuated total reflection (ATR) coupled with the QCL beam to detect and identify chemical changes and be deployed in hostile environments, either radiological or chemical. The limit of detection (LOD) and the limit of quantification (LOQ) at 3σ for hydroxylamine nitrate ranged from 0.3 to 3 and from 3.5 to 10 g·L−1, respectively...
To address problems such as greenhouse gas emissions and energy security, the US is considering r... more To address problems such as greenhouse gas emissions and energy security, the US is considering renewable resources, such as geothermal energy. Hydrothermal systems produce about 3000 MWe domestically; however, electricity may also come from engineered geothermal systems (EGS) with siting issues such as low-permeability rock, limited water, and deep wells. Water use can be reduced with a power cycle that works efficiently with air cooling, using refrigerant mixtures. Heat extraction from the subsurface represents another aspect of geothermal water use because complex fluid-rock interactions affect heat transport and lifetime performance. These factors all contribute to the viability of EGS. 1 Abstract To address problems such as greenhouse gas emissions and energy security, the US is considering large investments in renewable sources, such as geothermal energy. Hydrothermal systems that have the advantages of plentiful heat, water, and permeable rock already produce about 3000 MWe in the U.S. and more systems are in development. However, the potential for generating electricity from geothermal resources extends well beyond the traditional sources in the Western US. The US Department of Energy is actively supporting research on enhanced and engineered systems that may overcome issues such as low-permeability rock, limited water, and deep well drilling. One issue with engineered geothermal systems is siting. Engineered sites can be located in areas where surface water is limited or water use rights are an issue. One way of minimizing water use is to have a power cycle that can work efficiently with air cooling rather than water cooling. Oak Ridge National Laboratory is developing more efficient power cycles that take advantage of the physical properties of mixtures of refrigerants in Brayton or organic Rankine cycles. Experiments on an air-cooled test loop employing 8% isobutane in CO 2 have given a respectable 13% cycle efficiency versus a 14.5% theoretical value for pure super-critical CO 2. These experiments are complemented by thermodynamic calculations that have demonstrated the effects of sizing of components in supercritical versus transcritical cycles for mixtures of supercritical CO 2 and SF 6. In these calculations, air temperatures are varied between 10 and 40°C to account for seasonal variability. Extraction of heat from the subsurface represents another aspect of water use in geothermal power. Better understanding of how complex fluid-rock interactions affect heat transport to the surface should facilitate decisions on siting and options to maintain or improve performance during the lifetime of the power plant. These factors contribute to the viability of engineered geothermal technology, especially in arid regions of the country.
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