Performances of different efficiency calibration methods of high-purity-germanium gamma-ray spectrometry in an inter-comparison exercise

This study reports the performances of efficiency calibrations for high-purity-germanium gamma-ray spectrometry using the source-, Laboratory Sourceless Object Calibration Software(LabSOCS)-and ANGLE-based methods in an inter-comparison exercise. Although the results of LabSOCS and ANGLE for ^(241)Am emitting lowenergy gamma rays were not very satisfactory, all of the three efficiency calibration methods passed acceptance criteria. The results confirmed the reliability of the calculation codes ANGLE and LabSOCS as alternative efficiency calibration methods in high-purity-germanium gamma spectrometry. This study is likely to promote the further application of the ANGLE and LabSOCS calculation codes in radioactivity measurements.

The Maastrichtian-Danian in the SW Zagros Fold-Thrust Belt(S. Iran):An Integration of Planktonic Foraminiferal Biostratigraphy and Gamma-Ray Spectrometry

In this study, the Maastrichtian-Danian boundary was measured and sampled in two stratigraphic sections, the north and south flanks of the Dehnow anticline in Coastal Fars, Southern Iran. This boundary was also investigated in the drilled exploratory well-1 in the same region. The lithology of the Maastrichtian-Danian deposits consists of glauconitic, phosphatic argillaceous limestones and marlstones. 30 genera and 77 species of planktonic foraminifera have been determined. The recognized biozones are the Gansserina gansseri Interval Zone, and the Contusotruncana contusa Interval Zone, which indicates latest Campanian to middle Maastrichtian age for the upper part of the Gurpi Formation. In addition, the Eoglobigerina edita(P1) Partial Range Zone, Praemurica uncinata(P2) Lowest Occurrence Zone, Morozovella angulata(P3) Lowest Occurrence Zone and Globanomalina psudomenardii(P4) Taxon Range Zone represent a Danian to Thanetian age for the lower part of the Pabdeh Formation. From the absence of the Abathomphalus mayaroensis Interval Zone, Pseudoguembelina hariaensis Interval Zone, Pseudotextularia elegans Interval Zone, Plummerita hantkeninoides Interval Zone, Guembelitria cretacea(P0) Partial Range Zone and Parvularugoglobigerina eugubina(Pα) Total Range Zone, it can be deduced that there is a paraconformity across the Maastrichtian–Danian boundary in the studied area, this hiatus encompassing the late Maastrichtian and the earliest Danian. Danian deposits from the study area contain reworked glauconitized macrofossils, planktonic and benthic foraminifera of the Cretaceous. The obtained surface gamma-ray spectrometry logs resemble the exploratory well-1 gamma-ray wireline log.

Investigating the minimum detectable activity concentration and contributing factors in airborne gamma-ray spectrometry

In this study,the theory of minimum detectable activity concentration(MDAC)for airborne gamma-ray spectrometry(AGS)was derived,and the relationship between the MDAC and the intrinsic effi-ciency of a scintillation counter,volume,and energy res-olution of scintillation crystals,and flight altitude of an aircraft was investigated.To verify this theory,experi-mental devices based on NaI and CeBr 3 scintillation counters were prepared,and the potassium,uranium,and thorium contents in calibration pads obtained via the stripping ratio method and theory were compared.The MDACs of AGS under different conditions were calculated and analyzed using the proposed theory and the Monte Carlo method.The relative errors found via a comparison of the experimental and theoretical results were less than 4%.The theory of MDAC can guide the work of AGS in probing areas with low radioactivity.

Validation of ²²⁶Ra and ²²⁸Ra Measurements in Water Samples Using Gamma Spectrometric Analysis

Radium isotopes can be analyzed by different analytical methods based on gamma spectrometric measurements or alpha spectrometry. An improved method was developed to determine radium isotopes from water using gamma spectrometry after radiochemical separation. The Radium was selectively extracted from acidified samples using co-precipitation procedure with iron hydroxide and followed by precipitation of radium as radium sulphate Ba(Ra)SO4. The precipitate Ba(Ra)SO4 was filtered through the Millipore filter paper, dried and weighed to calculate chemical yield. 226Ra and 228Ra activities were measured using low-background gamma spectrometry in water samples. Radium was pre-concentrated from environmental samples by co-precipitation with BaSO4. The amounts of 226Ra and 228Ra on the sample were obtained by gamma-ray spectrometry for the 351 keVγ-ray from 214Pb and for the 911 keV γ-ray from 228Ac, both in radioactive equilibrium with precursors, respectively. The accuracy, selectivity, traceability, applicability and Minimum Detectable Activity (MDA) of the technique were discussed. Also, the effect of physical and chemical characteristics of the water samples such as TDS, pH, soluble species, sulphate and bicarbonate that effect on the radium determination were taking into consideration. The method has been validated with a certified reference material supplied by the International Atomic Energy Agency and reliable results were obtained. The radiochemical yields for radium were 70% - 90% and recovery was 97% and 80% for 226Ra and 228Ra, respectively.

Calibration of the High Purity Germanium Gamma-Ray Spectrometer in CERT, ABU Zaria, Nigeria

Gamma-ray spectrometry is a very powerful tool for radioactivity measurements. The gamma-ray spectrometer laboratory in Centre for Energy Research and Training (CERT), Ahmadu Bello University, Zaria, Nigeria is accredited to perform measurements of radioactive content of samples collected from the environment, food chain or industrial products with the aid of a high resolution HPGe detector. For accurate gamma-ray spectrometry, certain measurements were considered;the efficiency of the detector was performed experimentally against energies within the range of 59.50 keV (241Am) to 2204.50 keV (226Ra) for the respective geometries of 1 - 6 cm. The sustained solid angle relations with respect to the inverse square of sample geometries from 1 - 6 cm were evaluated. Another main point of this work was focused on the efficiency at geometry of 5 cm with respect to the three selected energies: 661.60 keV (137Cs), 1173.2 keV (60Co) and 1332 keV (60Co) for the main axis, ten degree off main axis, forty five degree off main axis and ninety degree off the detector main axis. In order to verify optimum geometries in our laboratory for both short lived and long lived radionuclides analyses, the evaluation of efficiencies for the respective energies: 1173.2 keV (60Co), 1332.5 keV (60Co), 1764 keV (226Ra) and 2294 keV (226Ra) were plotted against geometries of 1 to 6 cm from the detector end cap along the main axis.

航空数字γ能谱测量系统的研制

航空数字化γ能谱测量系统以NaI(Tl)晶体(10 mm×10 mm×40 mm)和光电倍增管构成的闪烁计数器为γ射线探测器,采用4条下测晶体和1条上测晶体组合成航空γ能谱测量系统的探头,设计了温度传感器、电流反馈型前置放大器和低纹波高压供电电路,实现了γ光子与核信号的转换;采用Y/U双通道数控增益放大器、双回路自动稳谱电路和算法实现了谱漂的精细调节和自动稳谱,通过高速ADC与CPLD实现模拟核信号的数字化。该系统可接入NaI(Tl)闪烁计数器γ探测器数20条,可探测能量范围0.02–10.0 MeV,采样周期0.5–1 s,最大计数通过率>100 k/s,1024道谱漂<±1道。

小波阈Wiener滤波器在航空伽玛能谱降噪中的应用

在传统的小波降噪基础上,根据Wiener滤波器和小波变换的特点,采用小波域Wiene滤波器对航空γ能谱谱线数据进行了降噪处理,取得了良好效果。采用该方法对内蒙某地区的航空γ能谱数据进行了处理,结果显示,该方法能有效降低原始能谱数据中统计涨落带来的影响,其降噪效果优于传统的降噪方法。

基于小波变换的航空γ能谱异常信息线单元校正方法

针对航空γ能谱测量工作时矿致异常信息在时域批次性干扰下难以有效提取的问题,结合小波变换理论与测线标准差变异系数理论,提出一种新的线单元校正方法。该方法利用小波变换擅长处理非稳态采样数据信号的特性,采用小波变换对线单元数据进行多尺度分解,通过软阈值滤除近似信号,有效去除含有时域批次性干扰的非地质背景信息,并对表征异常的细节信息进行重构,实现对时域批次性干扰的线单元校正。通过对实测数据的校正处理验证,结合航空伽马能谱地面异常查证结果及矿区地质简图,表明该方法削弱时域批次性效果明显,缩小了异常范围,提高了矿致异常点识别准确性,且异常形态与地面查证结果一致,客观还原测区的放射性核素分布情况。

Characterisation for <i>Radioelements</i>over an Escarpment Feature(S): A Case Study of the Duku-Tarasa Gwandu Ridge Area of Birnin Kebbi NW Nigeria

The paper presents results of radiometric investigations of an area (Duku-Tarasa) near the capital city of the State of Birnin Kebbi, NW Nigeria. The area of study is about 440 m × 420 m and encloses an Escarpment Feature/Structure on a sedimentary rock generally referred to as the Gwandu Formation. The Gwandu Formation (though not described in the paper) consists of continental lacustrine sediments and is the youngest Palaeogene Formation present in the Sokoto sector of the larger Iullemmeden Basin. The study measured, along some selected profiles across this escarpment feature, radiometric signatures using a Sim-Max G411 portable field gamma-ray spectrometer (giving counts for U, Th and K relative to the background values over the area), the ground total-field magnetic data (using the proton precession magnetometer) along those profiles and collected some (5) rock samples for flame photometry and AAS analyses towards the target proposition. Activity concentration levels due to potassium (K), uranium (U) and thorium (Th) were measured in the area along the five established profiles spaced at 50 metres. The results from these measurements and analyses were displayed (in Tables/histograms and gray level maps/images of concentrations of Uranium, Thorium and Potassium prospects) and interpreted (dismissing the magnetic data as seemingly passive as no filter was applied to the mapped data).

Natural Radioactivity Assessment and Radiological Hazards in Soils from Qarun Lake and Wadi El Rayan in Faiyum, Egypt

The activity concentrations of naturally occurring 238U, 232Th and 40K in surface soils along Qarun Lake and Wadi El Rayan located in Faiyum, Egypt were determined. The measurements were carried out through gamma-ray spectrometry using a coaxial HPGe detector. The results were compared with those reported in the literature. The radiological hazard radium-equivalent activity index, external and internal indices, radioactivity level index, absorbed dose rate, annual effective dose rate and total absorbed dose rate associated with radioactivity in all samples were evaluated and compared with recommended values. Correlation studies between pairs of radionuclides were performed and discussed.

Assessment of Natural Radioactivity in Rivers Sediment and Soil from the Copper Belt Artisanal Mining Region, Democratic Republic of the Congo

The concentrations and distribution of naturally occurring radionuclides (238U, 235U, 234U, 230Th, 226Ra, 210Pb, 232Th, 228Ra, and 40K) were determined by alpha and gamma spectrometry in soil and sediments collected from Luilu and Dilala rivers located in the mining district of Kolwezi (Lualaba Province) of the Democratic Republic of the Congo. The average concentrations of 238U and 226Ra in the analyzed samples were 5 - 10 times higher than the world average values for soil provided by the United Nations Scientific Committee on the Effects of Atomic Radiation. However, the average concentrations of 232Th were found similar to the world average. In both river basins, artisanal mining activities and mineral washing sites displayed the higher concentration values of radionuclides. The mean values of health risk indices calculated for those sites were found significantly higher compared to world average levels. Radiation protection measures seem needed to ensure the radiation safety of local populations. Graphical Abstract

Radiological Impact Assessment of Mining on Soil, Water and Plant Samples from Okobo Coal Field, Nigeria

Anthropogenic, including mining activities leaves the environment contaminated with potentially toxic substances and remote hazards if not properly checked. The quest in this study is the levels of naturally occurring radionuclides in Okobo coal, Nigeria and their possible distribution in coal mine vicinity soils, water and plants (cassava). Samples were characterized for levels of radionuclides and radiological detriments using high resolution gamma spectrometer, Gamma ray liquid scintillation and applicable radiological hazard indices. The range of mean activity concentrations (Bq·kg-1) for the environmental samples are as follows: 226Ra (8.39 ± 1.0 to 77.6 ± 4.0), 232Th (0.470 ± 0.4 and 77.8 ± 2), and 40K (29.1 ± 0.4 and 289 ± 6), with their respective mean values of 32.7 ± 2.1, 54.0 ± 1.5 and 158.8 ± 3.1 (Bq·kg-1). Radiological detriments including radium equivalent activity (Raeq), external hazard index (Hex), internal hazard index (Hin), radioactivity level index or gamma index (Iγ) and the ELCR for coal sample is 96.94 Bq·kg-1, 0.26, 0.30, 0.69, and 1.56 respectively. Reported values were below the safety limits stipulated by UNSCEAR and implied that the environment is relatively safe with low levels of natural radioactivity. Overall, this background study has demonstrated that Okobo coal mine is a less radio-hazard contributor to environmental samples. Exceptions to this generalization are representative gamma index (Iγr) and annual effective dose equivalent values for some cassava and soil samples, which may call for future impact monitoring.

Natural Radioactivity and Excess Lifetime Cancer Risk Associated with Soil in Kargi Area, Marsabit-Kenya

The main aim of investigating activity concentrations together with distribution of radionuclides naturally in soil from Kargi was to evaluate radiological health hazard together with environmental radioactivity. Research shows radionuclides as one source of exposure due to radiation with detrimental effects health wise for populations found in areas considered high background radiation. After collecting 117 soil samples from the area, analysis was done in order to measure their natural radioactivities due to 40K, 232Th and 226Ra radionuclides. Measurements method of gamma spectrometry employing a high purity germanium (HPGe) detector was employed basically to evaluate the radiological hazard of radioactivities. For 40K, 232Th and 226Ra, mean calculated activities were 353.19 ± 110.07, 7.98 ± 3.98 and 7.37 ± 2.60 Bq·kg -1 respectively. Mean values of absorbed and effective dose rates, external and internal hazard indices together with radium equivalent activity were 23.82 ± 6.59 nGy·h -1 and 0.14 ± 0.04 mSv·y -1, 0.12 ± 0.03 and 0.14 ± 0.04 and 45.90 ± 12.65 Bq·kg -1 respectively. Comparing with approved global values, the values were found to be below the given global limits. Evidence of involvement of metasomatic activity of the radioelements or fractionation during weathering is seen as calculations give a higher value Th/U. Excess cancer risk, calculated from the samples showed lower values as compared to global standard values hence minimal chance of getting cancer disease. The area is safe from cancer causing radionuclides.

Measurement of Radioactivity in Carbonated Soft Drinks and Annual Dose Assessment

A set of measurements have been conducted, using gamma spectrometry technique, in order to determine the activity-level in some carbonated soft drinks. The obtained activity is about 0.18 ± 0.07 Bq/l for 137Cs, whereas it is less than 0.13, 0.18 and 4.51 Bq/l respectively for 212Pb, 214Pb and 40K. The total average annual dose is about 3.49, 1.69 and 1.68 μSv/y respectively for 7 - 12, 12 - 17 and >17 years old person leading to a radiological risk about 0.142 for adolescent and adults. The obtained results show no significant radiation dose and radiation hazard on human health due to the consumption of these carbonated soft drinks.

Measurement of Natural Radioactivity in Sand Samples Collected from Ad-Dahna Desert in Saudi Arabia

Natural radioactivity is a source of continuous exposure to human beings. The natural radioactivity due to the presence of 226Ra, 232Th and 40K in sand samples collected from Ad-Dahna was measured by means of HPGe. The measured activity concentrations of radionuclides were compared with the worldwide reported data. Mean measured activity concentrations of 226Ra, 232Th and 40K varied between 16.2 - 30.6, 15.8 - 36.7 and 285.3 - 533.2 Bq·kg–1 respectively with a mean value of 23.4 ± 4.3 Bq·kg–1, 29.7 ± 5.9 Bq·kg–1 and 380 ± 65 Bq·kg–1 respectively. Mean values of radium equivalent activity, absorbed dose rate and external radiation hazard index were 106 ± 8 Bq·kg–1, 51.4 nGy·h–1 and 0.29 respectively. The annual effective radiation dose was calculated to be 0.32 mSv·y–1. The Raeq values of sand samples are lower than the limit of 370 Bq·kg–1, equivalent to a gamma dose of 1.5 mSv·yr–1.This study shows that the measured sand samples do not pose any significant source of radiation hazard and are safe for use in building materials.

Modelling Natural Radioactivity in Sand Beaches of Guarapari,Espírito Santo State,Brazil

Using gamma-ray spectrometry, the activity concentration of naturally occurring radionuclides 226Ra, 212Pb, 214Pb, 232Th, and 40K was determined in sand beaches samples from different areas in Guarapari, Espírito Santo state, from Brazil. The absorbed dose rates and annual effective dose were calculated and the results were compared with the internationally accepted values as well as others high background radiation areas (HBRAs). The activity concentration of the 232Th in Areia Preta as well as the absorbed dose rates and annual effective dose were higher than the others regions compared. The results show that Areia Preta in Guarapari has higher background found in beaches in world. This work is part of a research project for the natural background determination of the Brazilian coast.

Measurement of Natural Radioactivity in Lagoon Sands Used in Construction in the District of Abidjan, Côte d’Ivoire

Sand is an important natural material for the construction of houses, work buildings and other public spaces. This work, which is one of the first contributions to the environmental quality of construction materials, concerns the measurement of natural radioactivity in the lagoon sands collected in the district of Abidjan. Nineteen (19) samples of these sands are analyzed by gamma-ray spectrometry equipped with HPGe detector. The mean values obtained for 226Ra, 232Th and 40K are respectively 7.76 ± 1.84 Bq·kg-1, 5.21 ± 1.36 Bq·kg-1, and 217.31 ± 5.03 Bq·kg-1. The estimated average value of radium equivalent (Raeq) is 31.94 Bq·kg-1. The results show that the average values obtained are far lower than the global limits of 35, 30, and 400 Bq·kg-1 for the concentrations of 226Ra, 232Th and 40K, respectively, and 370 Bq·kg-1 for the equivalent radium established by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). Therefore, the use of the analyzed lagoon sand samples in the different construction sectors should not cause serious radiological effects on the populations living in the District of Abidjan. Our results provide new data on building materials radioactivity in Côte d’Ivoire and all over the World. They can also be used as a reference for future work.

New cross section measurements on tungsten isotopes around 14 MeV neutrons and their excitation functions

New cross sections of the^(183)W(n,α)^(180m)Hf,^(186)W(n,d*)^(185)Ta,^(182)W(n,p)^(182)Ta,^(184)W(n,p)^(184)Ta,^(182)W(n,2n)^(181)W,^(184)W(n,α)^(181)Hf,and^(186)W(n,α)^(183)Hf reactions were measured in the neutron energy range of 13.5-14.8 MeV via the activation technique to improve the database and resolve discrepancies.Monoenergetic neutrons in this energy range were produced via the T(d,n)^(4)He reaction on a solid Ti-T target.The activities of the irradiated monitor foils and samples were measured using a well-calibrated high-resolution HPGe detector.Theoretical calculations of the excitation functions of the seven nuclear reactions mentioned above in the neutron energies from the threshold to 20 MeV were performed using the nuclear theoretical model program TALYS-1.9 to aid new evaluations of cross sections on tungsten isotopes.The experimental data obtained were analyzed and compared with that of previous experiments conducted by other researchers,and with the evaluated data available in the five major evaluated nuclear data libraries of IAEA(namely ENDF/B-VIII.0 or ENDF/B-VII.0,JEFF-3.3,JENDL-4.0u+,CENDL-3.2,and BROND-3.1 or ROSFOND-2010),and the theoretical values acquired using TALYS-1.9 nuclear-reaction modeling tools.The new cross section measurements agree with those of some recent experiments and theoretical excitation curves at the corresponding energies.The consistency of the theoretical excitation curves based on TALYS-1.9 with these experimental data is better than that of the evaluated curves available in the five major nuclear data libraries of IAEA.