Gamma ray spectrometry

In this study a geological, lithological or pedogenesis
analysis is used to explain the values and distribution
of the primordial specific gamma activities in the
Jamaican soil environment. A random systematic sampling
method resulted in Jamaica being divided into 50 square
grids with a maximum sampling density of 225 square
meters per sample. The resulting sixty-eight (68) samples
were measured on a Canberra HPGe detector for 24 h and
the photopeaks for the primordial gammas of 238U, 232Th
and 40K analyzed. Spearman’s correlation was used to
investigate the relationships between the primordial specific
activities and the geological features of the soil
samples collected and the geographic information system,
ArcGIS v10.1 used to graphically depict the gamma profile
of the primordials across the island. The Kruskal–Wallis
test indicated that in general the variations of the primordial
gamma specific activities over the underlying soil
geologies were statistically significant. However, the pairwise
Post-Hoc test results did not suggest a significant
variation in mean specific for any of the primordial with all
the underlying geology even when the unadjusted p value
was used. This result along with the Spearman’s coefficient
correlation values suggested a moderate to weak relationship
between the gamma profile of the top soil and its
underlying geology. With the exception of a weak correlation
with 232Th (-0.295) no other primordial radionuclide
correlated with the UNESCO/FAO soil categories for
the island. The most significant correlations for soil characteristics and gamma activities were organic matter
which were positive for 232Th (0.518), 238U (0.481) but
negative for 40K (-0.284).

Hard X-ray spectrometry Tokamak Diagnostics of runaway electrons Physics of plasma Hard X-ray spectrum deconvolution a b s t r a c t A gamma-ray spectrometer based on LaBr 3 (Ce) scintillator has been used for measurements of hard X-ray emission generated by runaway electrons in the FT-2 tokamak plasmas. Using of the fast LaBr 3 (Ce) has allowed extending count rate range of the spectrometer by a factor of 10. A developed digital processing algorithm of the detector signal recorded with a digitizer sampling rate of 250 MHz has provided a pulse height analysis at count rates up to 10 7 s À 1. A spectrum deconvolution code DeGaSum has been applied for inferring the energy distribution of runaway electrons escaping from the plasma and interacting with materials of the FT-2 limiter in the vacuum chamber. The developed digital signal processing technique for LaBr 3 (Ce) spectrometer has allowed studying the evolution of runaways energy distribution in the FT-2 plasma discharges with time resolution of 1–5 ms.

Gamma-ray spectrometry on ITER can provide information both on confined fusion alpha particles for optimization of plasma heating and runaway electrons, which is important for safe reactor operations. For the purpose of deconvolution of gamma-ray spectra recorded in fusion plasma experiments the DeGaSum code has been developed. The code can be applied for processing of both spectra of monoenergetic gamma rays, which are born in nuclear reactions produced by alpha particles and other fast ions, and continuous bremsstrahlung spectra generated by runaway electrons in the MeV range in the plasma and reactor structure materials. Gamma-ray spectrometer response functions and bremsstrahlung spectra generated by electrons in the MeV energy range are calculated and used in the DeGaSum code. The deconvolution of the discrete spectra allows the identification of nuclear reactions, which give rise to gamma rays, and the calculation of their intensities. By applying the code for continuous hard x-ray spectra, the runaway electron energy distribution can be inferred. It can provide the maximal energy of runaway electrons with accuracy, which satisfies the ITER project requirements. The code has been used for processing of spectra recorded in JET experiments. An application of the deconvolution technique for gamma-ray emission measurements on ITER is discussed. (Some figures may appear in colour only in the online journal)

The paper focuses on high-resolutionmultidisciplinary research on three Devonian–Carboniferous boundary sections
in shallow-water carbonate rocks in the Namur–Dinant Basin (Belgium, France). The aim of the study is to
provide palaeo-environmental reconstructions and correlations supported by several independent quantitative
proxies. We describe several correlative horizons and provide their sequence-stratigraphic interpretation
based on facies analysis, spectral gamma-ray data, element concentrations (XRF) and δ13Ccarb, with
foraminifer-biostratigraphy age control. The most prominent surface is a basal surface of forced regression,
which is indicated by a sharp basinwards facies shift and a drop in clay-gamma-ray values and Al concentrations
at the base of the Hastière and Avesnelles formations in more distal settings. In proximal settings, this surface
merges with a hiatus at the Devonian–Carboniferous boundary inferred fromforaminifer biostratigraphy. This hiatus
can be correlated with the global Hangenberg sandstone event,which indicates a glacioeustatic sea-level fall.
Increasing values of Zr/Al, K/Al, Sr/Al and Mn/Al coincide with the proximal facies of the falling stage system tract
and lowstand system tract in the Hastière and Avesnelles formations as a consequence of the enhanced input of
siliciclastics and nutrients during low sea levels. The top of the middle Hastière member is interpreted as the
maximum regression surface, which is overlain by transgressive system tract of the upper Hastière member.
The patterns of gamma-ray, δ13Ccarb, Th/K, Al and Zr/Al curves are well correlated between the studied sections.
The δ13Ccarb excursions are correlated with the unnamed excursion in the Upper expansa conodont zone (Carnic
Alps) and with the global Hangenberg event s.l. excursion in the kockeli conodont zone. This sequencestratigraphic
framework is used for correlations with deltaic successions from the Tafilalt Basin, Morocco.
The basal surface of the forced regression equivalent to the Hangenberg sandstone event, which is typical for
deeper-water settings, is easily recognisable and correlatablewith gaps inmore-shallow water settings.Wesuggest
that it should be taken into account as a possible candidate for the “natural solution” of theDevonian–Carboniferous
boundary in discussions concerning its redefinition.

A multidisciplinary correlation of the Devonian–Carboniferous (D–C) boundary sections
from the Moravian Karst (Czech Republic) and the Carnic Alps (Austria), based on conodont
and foraminifer biostratigraphy, microfacies analysis, field gamma-ray spectroscopy (GRS), carbon
isotopes and element geochemistry, is presented in this paper. The study is focused on the interval from
theMiddle Palmatolepis gracilis expansa Zone (Late Famennian) to the Siphonodella sandbergi Zone
(Early Tournaisian). In Lesní lom (Moravian Karst), a positive δ13C excursion in the Bisphatodus
costatus – Protognathodus kockeli Interregnum from a distinct laminated carbonate horizon is
correlated with a carbon isotope excursion from the Grüne Schneid section of the Carnic Alps and
is interpreted as the equivalent of the Hangenberg black shales and a local expression of the global
Hangenberg Event sensu stricto. Higher up at both sections, a significant increase in the terrigenous
input, which is inferred from the GRS signal and elevated concentrations of terrigenous elements
(Si, Ti, Zr, Rb, Al, etc.), provides another correlation tieline and is interpreted as the equivalent of
the Hangenberg sandstone. Both horizons are discussed in terms of relative sea-level fluctuations
and palaeoceanographic changes. Recent studies show that conodont biostratigraphy is facing serious
problems associated with the taxonomy of the first siphonodellids, their dependence on facies and
discontinuous occurrences of protognathodids at theD–C boundary. Therefore, the correlative potential
of geochemical and petrophysical signatures is high and offers an alternative for the refining of the
problematic biostratigraphic division of the D–C boundary.

This study assesses the level of natural radioactivity due to radionuclides, 238U, 232Th and 40K, in 16 soil samples collected from 16 locations in Akure township, Ondo State, Nigeria. The activity concentrations of 238U, 232Th and 40K varied from 0.15 to 4.41 Bq kg−1, 4.21 to 9.92 Bq kg−1, and 167.79 to 419.52 Bq kg−1, respectively, with mean values of 1.29±1.39 Bq kg−1, 6.98±1.82 Bq kg−1 and 278.16±69.40 Bq kg−1 respectively, measured from all the soil samples studied. The mean total absorbed dose rate was obtained and the value is 16.89 nGy.h-1 . This average calculated absorbed dose rate in air was found to be much lower than the world average of 57 nGy h−1. The outdoor annual effective dose equivalent ranged from 12.82 to 30.25 μSv.y-1 with mean of 20.71 μSv y-1. This is considered to be low when compared to natural external radiation of about 2000 μSvy-1 to which no harmful effect is expected directly.

Phosphates, naturally containing trace amounts of uranium, were examined using direct γ-ray spectrometry. Both normal and Compton-suppressed counting modes were utilized. The 1001 keV photo peak of the second daughter of 238U was chosen because of its isolation from other, potentially
interfering peaks. The findings suggest that with the aid of Compton suppression, it is possible to quantify low uranium levels in phosphates using samples sizes of order 10 grams within an accuracy of 5%. The uranium content was determined in several sample types and was found to range
from 60±4 to 70±8 μg/g, depending on the sample composition. This investigation also considered the effects of sample size, counting time, and
counting technique as sources of precision maximization. This work has shown that only a small amount of phosphate is needed to determine the constituent concentration, instead of the standard several hundred grams of material.

In this study the K, U and Th radionuclide concentrations were determined in a sugar cane plantation that received large quantities of fertilizer and gypsum. Geochemical data were obtained for the clay, iron and organic matter in the soil samples, taken from depths of 0-20 and 20-40 cm. The average radionuclide concentrations were 71 Bq Kg-1 for K; 5.97 Bq Kg-1 for U, and 11.26 Bq Kg-1 for Th, and the uranium was variable (56%). The radionuclide average concentrations for the different fertilizer compositions varied in the range of 603.5 - 8855.0 Bq Kg-1 for K; 27.3 - 684.4 Bq Kg-1 for U, and 58 - 788.5 Bq Kg-1 for Th, and it was most variable for K (53%). Gypsum average concentrations were 82.6 Bq Kg-1 for K, 641.5 Bq Kg-1 for U, and 201.7 Bq Kg-1 for Th, and it was most variable for K (46%). Average organic matter, clay and iron concentrations for both the depths were 0.71 and 0.68 %; 16.2 and 16.9 %, and 29.0 and 26.8 mg/l respectively.

A determination of cement brick and room's dimensions effect on public exposure dose has been carried out. Samples were collected from two cement brick factories in Port Said, Egypt. The samples were prepared and analyzed for activity concentration using HPGe detector with a specially designed shield. The public exposure dose was calculated by using stander room model calculation, then for three traditional room dimensions used in Egypt compared with the stander one. The results show that there is no major difference due to room size and the annual dose rates ranged from 100 to 170 Sv.yr-1 for inhabitants who are spending 80% of the indoor time. These values are low from the point of view of radiation protection (The average worldwide value is 2400 Sv.yr-1). The behavior of the specific effective dose rate (nGy.h-1 per Bq.kg-1) with wall width shows that the first 5 cm of the wall width is responsible of 75% of the exposure dose rate inside the room. The results show the major effect of the wall tiling materials.

This study relies on the measurement activity concentration of stream sediments from
the Băiţa-Plai brook, which is polluted by the spoil-banks of an abandoned uranium
mine. Geologically speaking, the area is mainly formed out of sedimentary rocks,
which are soluble in water, so they can travel large distances in this medium. We
measured several radionuclide activity concentrations along the river using an Ortec
GMX – type HpGe detector with relative efficiency of 34%. The investigated
radionuclides were 238U, 210Pb, 232Th, 226Ra, 137Cs, and 40K. The average activity
concentrations were 260±45 Bq/kg for 238U, 50±4 Bq/kg for 210Pb, 21±2 Bq/kg for 232Th, 80±4 Bq/kg for 226Ra, 2±0.2 Bq/kg for 137Cs, and 383±15 Bq/kg for 40K. We
observed that the values were much higher at the upper side of the river and at the
regions, where the settlements are and that they were lower at the estuary of the brook.
We also measured limit exceeding levels of 226Ra concentration in the area of the
settlements and the first sample had a much larger activity (546±20 Bq/kg)
concentration than the concentration of a normal soil sample.

The radiogeochemistry of granite gneisses in Akunu-Akoko (AK) and Ayere (AY) areas of the southwestern Basement Complex of Nigeria was studied using gamma-ray spectrometry and statistical analyses and modelling. This study was aimed at determining the radionuclides concentration in these rocks, as well as alteration scenarios, nature and rates of uranium migration (UM), levels of radiological hazards, and rate of radiogenic heat production (RHP). The interquartile () elemental concentrations for 40 K, 238 U and 232 Th were 0.23<3.75<4.06%; 1.00<4.20<5.40 ppm; and 4.10<16.10<30.20 ppm, respectively, within the minimum and maximum limits of BDL (below detection limit)-5.23%, BDL-9.70 ppm, and 0.40-60.20 ppm. The average activity concentrations of 40 K, 238 U and 232 Th with values of 629.28, 38.58, and 49.96 , respectively, were above their crustal averages in the order of AK3<AK2<AK3<AY3<AY1<AY2. Variability in K-eU-eTh content and alteration in the rocks were affirmed by radioelement ratios and F-parameter. The high radionuclide concentrations could be due to high levels of radioactive-bearing materials, as well as trace and rare earth elements. Low radionuclides concentration in the rocks may have resulted through weathering, metamorphism, and 12-86% outward UM. The absorbed dose rate (ADR) average of 75.09 was within the allowable range, with the Square R prediction rates of 25-92% from the radionuclides. The average radium activity was below the permissible limit of 370 , and the annual effective doses, hazard indices, gamma activity, and activity utilization index were all far below the safe limit of 1. However, gonad equivalent and excess lifetime cancer risk were above their permissible limits. RHP average of 1.89 above the crustal range of 0.8-1.2 may have considerably contributed to the heat flux in the areas. Square R analysis also predicted that 36-86% of RHP rates in the rocks are achievable from the radionuclides. Reduction in the usage of granite gneisses as a sole raw 2 material for constructions is advised due to the increase in radionuclides and some radiological indicators exceeding world allowed limits.

Results are presented from experimental studies of runaway electrons in the ohmic heating regime in the Globus-M tokamak. The periodical hard X-ray bursts observed with the help of two hard X-ray spectrometers with high time resolution are attributed to MHD oscillations in the plasma core and at the periphery.