Laboratory Gamma Spectrometry Research Articles

Effects of mine water discharge on river sediments: metal fate and behaviour, Upper Silesian Coal Basin

The study aims to characterise the changes in elemental composition in the river sediments of streams influenced by mine waters enriched with radionuclides. The study took place in the vicinity of Ostrava, a city located in a coal mining region in the Czech Republic, namely the Upper Silesian Coal Basin. River sediments and waters of the Karvinský potok and Stružka streams were investigated. Field measurements were made for ambient dose equivalent rate (ADER). Laboratory gamma spectrometry and X-ray fluorescence were used to determine the content of radionuclides and elemental composition in river sediments. Water samples were analysed for the content of major ions and radionuclides. The field ADER measurement proved elevated content of radionuclides with values exceeding 1,000 nSv/h in both streams. The discharged mine waters were Na–Cl type, containing an 226Ra (0.68–0.70 Bq/l) as a dominant radionuclide. Laboratory measurements of radionuclides in bottom sediments proved that the prevailing source of radiation are 226Ra and 232Th in both streams. The calculated enrichment factors showed extreme values for Sr, Cr, Pb, Zn, Cu, and Mo. The precipitation reactions forming Ca-minerals (calcite and aragonite), Fe-bearing minerals (hematite, goethite and amorphous Fe(OH)3) and hausmannite were found to be the primary geochemical process underway in the studied riverine systems. The correlation between elements and radionuclides demonstrated the significant role of geochemical barriers that lead to the precipitation of radionuclides from solution. The results show that the precipitation takes place preferentially in places where other waters enter the stream, or where recent organic matter is present.

Correlation between Ground 222Rn and 226Ra and Long-Term Risk Assessment at the at the Bauxite Bearing Area of Fongo-Tongo, Western Cameroon

The aim of the current work was to study natural radioactivity in soil and the correlation between 222Rn and 226Ra in the ground and to assess the onsite and indoor long-term excess cancer risk at the bauxite bearing area of Fongo-Tongo in Western Cameroon. 222Rn was measured in the ground at a depth of one meter, using Markus 10 detector. 226Ra, 232Th, and 40K activity concentrations were measured in soil by two techniques, in situ and laboratory gamma spectrometry. The mean values of 222Rn concentrations in the ground were 69 ± 18 kBqm−3 for Fongo-Tongo and 82 ± 34 kBq m−3 for the locality of Dschang, respectively. The mean values of 226Ra, 232Th, and 40K activity concentrations obtained with in situ gamma spectrometry were 129 ± 22, 205 ± 61, and 224 ± 39 Bq kg−1 for 226Ra, 232Th, and 40K, respectively, and those obtained by laboratory gamma spectrometry were 129 ± 23, 184 ± 54, and 237 ± 44 Bq kg−1, respectively. A strong correlation between 222Rn and 226Ra activity concentrations determined by in situ and laboratory measurements (R2 = 0.86 and 0.88, respectively) was found. In addition, it is shown that the total excess cancer risk has a maximum value of 8.6 × 10−3 at T = 0 year and decreases progressively in the long term. It is also shown that 226Ra makes a major contribution, i.e., above 70%, to the total excess cancer risk.

The anthropogenic fallout radionuclides in soils of Mount Khuko (the Western Caucasus) and their application for determination of sediment redistribution

The purposes of this study are to determine the content and origin of anthropogenic fallout radionuclides (FRN) in soils of Mount Khuko, located in the western sector of the Caucasus Mountains and to assess the possibility to use them for evaluation of sediment redistribution for the alpine grasslands,.The field study was carried out in August 2019 near the top of Mount Khuko, located in the western part of the main Caucasus Mountain Ridge. Integral and incremental soil samples were collected from the different morphological units of the studied area. The content of 137Cs and 241Am in soil samples was evaluated using laboratory gamma-spectrometry. A part of samples was selected for Pu isotopes extraction and then alpha-spectrometric analysis.It was established that the 137Cs contamination of soils in the studied area has at least two sources of origin. The first source is the 137Cs bomb-derived fallout after the bomb tests in 1950–60th, which is widespread across the globe. The second source is 137Cs Chernobyl-derived fallout High random variability (Cv = 25–42%) was found within reference sites, located at the undisturbed areas on the local flat interfluves due to high variability of soil characteristics (grain size, density, organic matter content etc.). However minimum spatial variability (range 12,2–14,3 kBq/m2) was identified for the mean value of 137Cs inventories for all 5 reference sites located in the different parts of the studied area. It is difficult to separate individual peaks of the bomb-derived and Chernobyl-derived 137Cs falloutin sediment sinks with low sedimentation rates.Application 239,240Pu as an additional chronological marker allows to identify the origin of above mention peaks in the soils of alpine grasslands and of dry lake bottom.

Applying in-Situ and Laboratory-based Gamma Spectrometry to Determine Activity Concentration and Distribution of 40K, 226Ra and 232Th in Abeokuta, Southwest Nigeria

Abstract: The applications of radionuclides are potential sources of health risk and also a concern in the area of nuclear security. It is therefore imperative to determine the presence of the different radionuclides present in the environment at all times, because it is necessary to control and assess the risk level in the environment. The present study compares activity concentrations of the primordial radionuclides 40K, 226Ra and 232Th obtained from laboratory gamma spectrometry measurements with the activity concentrations of the radionuclides as obtained from in-situ measurements. Soil samples were randomly collected from nineteen different points within Abeokuta city ensuring good coverage of the city area. A mobile gamma spectrometry system was used to collect gamma spectra measurements in the field. The obtained values are presented. The ranges of activity concentrations for 40K, 226Ra and 232Th have been found to be 113 – 1975, 5 – 128 and 181 – 3284 Bqkg-1, respectively for laboratory gamma spectrometry and 104 – 1312, 31 – 121 and 104 – 2578 Bqkg-1, respectively for in-situ gamma spectrometry measurements. This study showed that the average activity concentrations of the primordial radionuclides in Abeokuta were much higher than worldwide averages of 400, 35 and 30 Bqkg-1 for 40K, 226Ra and 232Th, respectively. From both methods, 232Th is seen to be the major contributor to the environmental radioactivity of Abeokuta. Good correlations also were deduced between the activity concentration results obtained from laboratory and in-situ gamma spectrometry, which therefore implies a significant relationship between the two methods used in the study. Keywords: In-situ gamma, Gamma spectrometry, Activity concentration, Radionuclides.

Sources of uncertainty in field gamma-ray spectrometry: Implications for exploration in the Lower-Middle Jurassic sedimentary succession of the Lusitanian Basin (Portugal)

Uncertainties related to in situ gamma-ray spectrometry measurements have been widely acknowledged. Despite being commonly used in exploration, the evaluation of the uncertainty range of K, U and Th gamma spectrometry field measurements is generally limited due to the lack of corresponding laboratory measurements. Estimating uncertainty, however, is essential to ensure reliable and accurate results.In this paper, we establish a set of procedures to acquire gamma-ray spectrometry data while minimizing uncertainty, based on high-resolution lithostratigraphy and composite gamma-ray logging techniques. We compare the concentration of radionuclides measured in situ in 250 selected sites in outcrops of the Lower and Middle Jurassic sedimentary successions of the Lusitanian Basin to the concentration of radionuclides in representative samples collected from the same outcrops and analysed in the laboratory.The global radiometric dataset obtained for K, U and Th is similar between field and laboratory gamma spectrometry measurements, which are correlated. The root-mean-square deviation was determined for K, U and Th, and the error of the field measurements was estimated at 0.6%, 1.4 and 2.5 ppm, respectively. We calculated the relative error (RE) between laboratory and field data. If we use the interquartile range of the RE to distinguish outliers in each radionuclide dataset, approximately 8%, 6% and 10% of the K, U and Th field measurements correspond to outliers. Conversely, 92%, 94% and 90% of the samples offer reliable field data for K, U and Th, respectively. The RE is similar between K and U, with a mean of 0.73 and 0.69, respectively, and is higher for Th (with a mean of 1.29). Higher RE values are also observed in dolostones (D), dolomitic limestones (DL), limestones (L) and marly limestones (ML). Lower RE values are linked to sandstones (S) and fine-grained siliciclastic (F-g.S) lithologies, with a mean value of 0.19, 0.33 and 0.25 for K, U and Th, and 100% of reliable data.As the accuracy of field gamma-ray measurements varies with lithology, field procedures must be adjusted for lithological variability to reduce uncertainty. Given that the RE decreases with an increase in layer thickness, thicker sedimentary layers should be favoured when measuring K, U and Th concentration in field campaigns.

Assessment of contamination with trace elements and man-made radionuclides around Temelin Nuclear Power Plant in Czech Republic

Abstract The results of atmospheric deposition of heavy metals and trace elements, determined in moss Pleurozium schreberi collected around the Temelin Nuclear Power Station in the Czech Republic in 2011, are presented. The monitored area around NPP Temelin comprises 29 sampling sites located along 8 profile radii stretched as of 2, 5, 10, and 20 km from the NPP. Some pollution sources are located in the study area. A total of 42 elements (Na, Mg, Al, Cl, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, As, Se, Br, Rb, Sr, Zr, Mo, Ag, Cd, In, Sb, I, Cs, Ba, La, Ce, Sm, Eu, Tb, Hf, Ta, W, Au, Hg, Pb, Th, and U) were determined by epithermal instrumental neutron activation analysis with the neutron flux density Φ epi=3.6×10 11 n/(cm 2 s) at the pulsed fast reactor IBR-2, FLNP, JINR. To determine the presence of radionuclides and their measurable activity in samples, laboratory gamma spectrometry was found to be the best detection method. A coaxial HPGe detector with samples in the geometry of Marinelli containers in the laboratory of Faculty of Nuclear Sciences CTU in Prague was used. To assess the influence of NPP Temelin on the Biomass in 20 km radius, the mass activity of 137 Cs (Bq/kg) was determined. No other short-term radionuclides have ever been identified in any spectrum.

Validation of in situ and laboratory gamma spectrometry measurements for determination of 226Ra, 40K and 137Cs in soil

In situ and laboratory gamma spectrometry methods for determination of 226Ra, 40K and 137Cs in soil have been validated and compared. Minimum detectable activity, repeatability, and reproducibility were the main validation parameters. Results have shown that soil humidity lower the in situ measurement results in comparison to laboratory measurements. Measurement uncertainties were also estimated and compared for both techniques. Uncertainty due to soil humidity (55%) using the in situ measurement was the main contributor to the total uncertainty, while the uncertainty due to net counting (71%) using the laboratory measurements was the largest contributor to the total uncertainty value.

Effect of small potassium-rich dykes on regional gamma-spectrometry image of a potassium-poor volcanic complex: A case from the Doupovské hory Volcanic Complex, NW Czech Republic

Basaltic rocks with low K, U and Th contents dominate the entire Volcanic Complex of the Doupovské hory Mts. Significant potassium anomaly exceeding 1.5 atomic wt.% of potassium over an area of 4 × 8 km and 2 atomic wt.% of potassium over an area of 2 × 6 km was defined by airborne gamma-ray spectrometry above the central part of the Doupovské hory Volcanic Complex. The following detailed field study, supported by field and laboratory gamma-spectrometry measurements and geochemical analyses of rock samples, resulted in discovery of a swarm of potassium-rich trachytic dykes. The existence of such highly-differentiated rocks in the volcanic complex was unknown till present. These dykes are commonly less than 1 m wide, but their potassium content varies between 4 and 8 atomic wt.%. Owing to this high-K composition and relative abundance of dykes, the dyke rocks significantly modify the regional pattern of gamma-spectrometry data. The potassium anomaly cannot be explained by the presence of Flurbühl intrusive body dominated by ijolites and essexites, as all these rocks are poor in K, with potassium typically not exceeding 1.5 wt.%. On the other hand, much more extensive intermediate trachybasaltic lavas with K content varying within the range 1.8–3 wt.% cause only minor or undetectable anomalies.

Data analysis from monitoring of radionuclides in the nuclear power plant Temelin ecosystem area

Changes in the ecosystem occur naturally, however, can also be due to man's activity. The unique ecosystem monitoring based on studying contamination of the bioindicators by man-made radionuclides has been providing data from the area of nuclear power plant (NPP) Temelin (CR) using laboratory gamma spectrometry for past 8 years. The increase in radioactivity in the NPP ecosystem area resulting from its operation is evaluated through comparison with a zero level of 137Cs mass activities and by obtained data trend analysis.

Use of Gamma Spectrometry Method for Environmental Monitoring in the area of NPP

It is generally not possible to correctly determine the long and short term impact of human activity upon the environment, without thorough processing of data, obtained through monitoring. It was confirmed that such impact on the environment must be monitored over a long time period. The data obtained must be of high quality, an attribute assured by present state of scientific knowledge. One of the well established methods for monitoring atmospheric deposition of radionuclides in the environment is laboratory and in situ gamma spectrometry. With the aim to monitor an occurrence of a one-time escape or persistent release of fission products into the air, resulting from an operation of a nuclear plant, two types of monitoring are performed: i/ measurement of samples from the environment (Schreber moss, forest humus, pine bark, mushrooms and forest berries) using laboratory gamma spectrometry method in the range up to 3 MeV (those data are used for the trend analysis and for the construction of the contaminationmaps); ii/ in situ gama spectrometry for assessment dosimetry and spectrometry characteristic of photon-fields (those data are used for the dose rate calculation).

Comparative analysis of the in and ex situ determination of environmental radiation and dosimetry levels

A method is proposed to determine the activities of natural and artificial gamma-emitting radionuclides in soils using in situ spectrometry that is validated with conventional low-background laboratory gamma spectrometry. From the two sets of results, the dose-equivalent rate levels in the environment were reproduced and we are thus able to determine the principal components of those levels.

Luminescence dating of Holocene aeolian sand movement, Thy, Denmark

We report on the application of optically stimulated luminescence dating to an investigation of the frequency of periods of aeolian sand movement and dune formation. On the coast of Thy, Holocene aeolian sediments, interleaved with peaty palaeosols, form some of the most complete successions known in western Denmark. Samples were taken from a coastal exposure, and an inland archaeological site. Dosimetry was based on laboratory gamma spectrometry, and quartz luminescence measurements used the single-aliquot regenerative-dose protocol, and 470±30 nm stimulation. The sand samples cover an age ranging from about 100 years to 4500 years; the youngest dates give us confidence that the material was well bleached at deposition. Good agreement was obtained with the radiocarbon palaeosol ages. We identify three main periods of aeolian sand movement, starting at about 4200, 2700 and 900 years ago; at least during the latter two periods significant aeolian sand movement occurred. All three phases of aeolian activity were separated by long periods of stability and soil formation. A more recent episode of dune formation, restricted to the coast and beginning less than 200 years ago, may have been triggered by modern coastal erosion.

Optically stimulated luminescence dates for Late Pleistocene and Holocene sediments from Nørre Lyngby, Northern Jutland, Denmark

Quartz from late Pleistocene marine and freshwater deposits of known 14C age, and from a historically dated aeolian deposit, has been studied using multiple-aliquot and single-aliquot protocols. Comparisons are presented between equivalent doses derived using a multiple-aliquot additive-dose thermoluminescence approach, and three OSL protocols—Single aliquot regeneration and added dose (SARA; Mejdahl and Bøtter-Jensen, 1994), single-aliquot additive-dose (Murray et al., 1997) and single-aliquot regenerative-dose (Murray and Roberts, 1998). Dose rates, determined by laboratory gamma spectrometry, are compared with both field gamma scintillation measurements, and laboratory beta thermoluminescence dosimetry measurements. The agreement is satisfactory. The resulting dates are discussed in terms of absolute chronology and bleaching environment.

Equilibrium line and mean annual mass balance of Finsterwalderbreen, Spitsbergen, determined by in situ and laboratory gamma-ray measurements of nuclear test deposits

In order to determine the equilibrium line (EL) and the annual net mass balance over the accumulation area of Finsterwalderbreen, Spitsbergen, Svalbard (by detection of the 1962–63 radioactive peak from the 1961–62 atmospheric nuclear tests), we collected 14 ice cores, at elevations of 445–730 m, in the springs of 1994 and 1995. The corresponding samples were melted and filtered for laboratory gamma spectrometry. In the accumulation area, the 1962–63 radioactive layer is found well below the surface. The mean annual accumulation is not invariably related to altitude. The EL, averaged to 545 in a.s.l., leads to an accumulation area ratio of 0.3 and indicates a strong negative balance. The 584 Bq m−2 mean137 Cs deposition rate (1954–74 nuclear tests) for eight ice cores in the accumulation area is nearly twice the 340 Bq m−2 mean Svalbard value obtained from six other glaciers (at time of deposition). An in situ gamma-ray detector was lowered down each borehole, and137 Cs levels were recorded. The counting rate is proportional to the apparent deposition rate and the specific activity. The laboratory measurements perfectly match the in situ determinations. In the ablation area, a dust layer and the associated nuclear test deposits are concentrated close to the bare ice surface of the glacier, under the winter snow layer and present maximum 137 Cs and 210 Pb contents. The dust layer acts like a filter for radioactive materials removed from the glacier and its basin by melting and water flow. The original specific activities and deposition rates at a given location are enhanced by adsorption of additional radioactivity on the dust particles. A linear relationship exists between 137 Cs and 210 Pb deposition rates. This process is almost constant for all studied ice cores. The apparent 137 Cs deposition rate for seven ice cores in the ablation area is 465 Bq m−2 (at date of measurement: 1 July 1995).

Equilibrium line and mean annual mass balance of Finsterwalderbreen, Spitsbergen, determined by in situ and laboratory gamma-ray measurements of nuclear test deposits

In order to determine the equilibrium line (EL) and the annual net mass balance over the accumulation area of Finsterwalderbreen, Spitsbergen, Svalbard (by detection of the 1962–63 radioactive peak from the 1961–62 atmospheric nuclear tests), we collected 14 ice cores, at elevations of 445–730 m, in the springs of 1994 and 1995. The corresponding samples were melted and filtered for laboratory gamma spectrometry. In the accumulation area, the 1962–63 radioactive layer is found well below the surface. The mean annual accumulation is not invariably related to altitude. The EL, averaged to 545 in a.s.l., leads to an accumulation area ratio of 0.3 and indicates a strong negative balance. The 584 Bq m−2 mean137 Cs deposition rate (1954–74 nuclear tests) for eight ice cores in the accumulation area is nearly twice the 340 Bq m−2 mean Svalbard value obtained from six other glaciers (at time of deposition).An in situ gamma-ray detector was lowered down each borehole, and137 Cs levels were recorded. The counting rate is proportional to the apparent deposition rate and the specific activity. The laboratory measurements perfectly match the in situ determinations. In the ablation area, a dust layer and the associated nuclear test deposits are concentrated close to the bare ice surface of the glacier, under the winter snow layer and present maximum 137 Cs and 210 Pb contents. The dust layer acts like a filter for radioactive materials removed from the glacier and its basin by melting and water flow. The original specific activities and deposition rates at a given location are enhanced by adsorption of additional radioactivity on the dust particles. A linear relationship exists between 137 Cs and 210 Pb deposition rates. This process is almost constant for all studied ice cores. The apparent 137 Cs deposition rate for seven ice cores in the ablation area is 465 Bq m−2 (at date of measurement: 1 July 1995).

Dose rate conversion factors, soil thickness and their influence on natural background dose rate in air above carbonate terrains

The natural background dose rate in air above ground surface is the sum of doses arising from cosmic radiation and radionuclides in air, soil and bedrock. The resulting dose rate arising from radionuclides in soil and bedrock (ground component) is the product of characteristic radionuclides specific activity in soil or bedrock with the accompanying dose rate conversion factors (DRCF). The sum of products between unit dose rates from each emitted photon energy and the emission intensity of all accompanying radionuclides is presented with DRCF for characteristic radionuclide. DRCF are calculated for unit 40K activity in soil and bedrock as well as for unit head radionuclides activity of 232Th decay series, 235U decay series, 238U- 230Th subseries and 226Ra- 210Pb subseries, in relation to soil thickness. Presented DRCF values are generally in good agreement with those published previously, and strongly depend on soil thickness. Recalculation of ground component of natural background dose rate data collected by airborne or carborne surveys above carbonate terrains into radionuclides concentration in the ground is possible in two cases. Recalculated values present radionuclide concentrations in bedrock in the case where soil has been completely missing. In the case of well-developed soil (thickness of 25 cm or more) it represents concentrations in soil relatively well. The laboratory gamma-spectrometry of 40K, 226Ra, 228Ac or 208Tl and 238U in samples collected during conventional geochemical sampling provides a good database of characteristic radionuclides. Such a database is applicable for assessment of ground components of natural background dose rate, as well as for geochemical map constructions.

Geochemical Studies of Columbia River Basalts

ABSTRACTWe report our findings for two studies of Columbia River basalts that are relevant to United States radwaste disposal programs. A rhyodacite intrudes the Wanapum basalt and is exposed in a quarry along the Hood River, Oregon. Since the rhyodacite is different geochemically from the basalt, and was intruded at a high temperature, then this site can be used to evaluate the effects of the intrusion on the basalt. In such a study we assume the intrusive rock is a high temperature heat engine, and that cooling may be by convection, conduction, or both. Contact effects of the intrusion are not pronounced in the basalt, and are restricted to minor recrystallization within one meter of the contact, and to possibly some minor fracture filling. Traverses were made from the rhyodacite into the basalt, and samples at closely spaced intervals analyzed for K, U, Th by field and laboratory gamma spectrometry, and by neutron activation analysis for some 35 elements. Separate aliquots were analyzed by isotope dilution to inspect Sr isotopic variations. The chemical studies do not indicate migration of any elements from the rhyodacite into the basalt, nor for any in-basalt or in-rhyodacite migration. Despite a pronounced chemical gradient between the rocks, each has remained a closed, isochemical system. The Sr isotopic studies indicate that the rhyodacite possesses Sr (87/86) = 0.70407 ± 0.00008 while the intruded basalts possess Sr (87/86) = 0.7052 ± 0.0002. Even in samples of the contact, with intermingled rhyodacite and basalt, each rock preserves its own characteristic Sr (87/86) signature, thus again attesting to the closed system conditions. We conclude for this natural experiment that the Wanapum basalt is not readily penetrated by elements from a high temperature, molten source.