High Resolution HPGe Detector Research Articles

Evaluation of gamma-ray and neutron attenuation properties of some polymers

Abstract In the present work, we determined the gamma-ray attenuation characteristics of eight different polymers(Polyamide (Nylon 6) (PA-6), polyacrylonitrile (PAN), polyvinylidenechloride (PVDC), polyaniline (PANI), polyethyleneterephthalate (PET), polyphenylenesulfide (PPS), polypyrrole (PPy) and polytetrafluoroethylene (PTFE)) using transmission geometry utilizing the high resolution HPGe detector and different radioactive sources in the energy range 81–1333 keV. The experimental linear attenuation coefficient values are compared with theoretical data (WinXCOM data). The linear attenuation coefficient of all polymers reduced quickly with the increase in energy, at the beginning, while decrease more slowly in the region from 267 keV to 835 keV. The effective atomic number of PVDC and PTFE are comparatively higher than the Zeff of the remaining polymers, while PA-6 possesses the lowest effective atomic number. The half value layer results showed that PTFE (C2F4, highest density) is more effective to attenuate the gamma photons. Also, the theoretical results of macroscopic effective removal cross section for fast neutrons (∑R) were computed to investigate the neutron attenuation characteristics. It is found that the ∑R values of the eight investigated polymers are close and ranged from 0.07058 cm−1 for PVDC to 0.11510 cm−1 for PA-6.

Investigation of radiation shielding properties for some ceramics

Abstract In this work, the radiation shielding parameters like mass and linear attenuation coefficient, half value layer, tenth value layer, mean free path, effective atomic number, effective electron density, exposure buildup factor and fast neutron removal cross section were examined for the peridot, aluminum nitride, ruby, yttrium oxide, magnesium silicate, and silicon nitride ceramic samples. Furthermore, the dependence of the effective conductivity on the energy was investigated. The experimental studies were carried out in the photon energy range of 81 keV–1333 keV using a high resolution HPGe detector and six different radioactive sources. The experimental results were validated with the theoretical results and a good agreement was observed for all samples. The yttrium oxide has more shielding effectiveness for γ radiation, while magnesium silicate, aluminum nitride and silicon nitride possess least γ-ray shielding. However, the optimum neutron shielding material is ruby.

Measurement of the cross sections for 238U(n, γ)239U reaction in the energy range of 14.1–14.8 MeV using neutron activation method

The neutron capture reaction cross sections of 238U were measured at the neutron energies of 14.1, 14.5 and 14.8 MeV using the activation method and off-line γ-ray spectrometric technique. The induced gamma-ray activities were measured using a low background gamma ray spectrometer equipped with a high resolution HPGe detector. The excitation functions of the 238U(n,γ)239U reaction were also calculated theoretically using the TALYS-1.8 program and are in general agreement with experimental data. The experimentally determined cross sections were compared with the data in the literature, and the evaluated data of ENDF/B-VIII.0, JENDL-4.0, and CENDL-3.1, as well as calculated results from TALYS-1.8.

Isomer ratios and cross sections for the isomeric pair 122mSb and 122gSb in the 123Sb(n,2n) reaction

Cross-sections and their isomeric ratios σm/σg in the energy range of 13–15 MeV for isomeric pair 122mSb and 122gSb produced by the 123Sb(n,2n) reaction have been measured by activation and off-line γ-ray spectrometric technique using the K-400 Neutron Generator at the Chinese Academy of Engineering Physics (CAEP). Specifically, the versatile stacked foil irradiation technique and a high resolution HPGe detector were employed. The 3H(d,n)4He reaction was used to produce the neutron beam. Partial cross sections σm and σg were derived from the absolute cross section of the metastable state and residual nuclear decay analysis. The 123Sb(n,2 n)122m,gSb reaction excitation functions and their isomeric cross section ratios were numerically calculated with TALYS-1.8 code with different level density options. Results are discussed and compared with corresponding literature data.

Determination of Natural Radioactivity Concentration in Consumed Nuts and Seeds and Their Implications in Human Body

The concentrations of natural radioactivity of 226 Ra, 232 Th and 40 K were measured in nuts and seeds samples consumed in Saudi Arabia. A high-resolution HPGe detector was used for the natural radionuclides measurement. The results indicate that 40 K was detected in all samples, whereas 226 R and 232 Th were found only in Brazil nut sample. The average concentration of 40 K in the investigated samples was 363.82 Bq kg -1 . The estimated annual effective dose due to ingestion of nuts and seeds was 0.068 mSvy -1 lower than the annual dose limit of 1 mSv y -1 for public exposure. This indicates that no risk is expected by the intake of the studied nuts and seeds samples. The radionuclide concentrations were compared with those reported from different countries.

Levels and effects of natural radionuclides in sediment banks of Rhumel River (Northeast Algeria)

Activity concentrations of natural radionuclides in Boumerzoug River sediment (the main tributary of Rhumel river) have been measured using high resolution HPGe detector. The activity concentrations of the samples were range from 16.66±2.32 Bq/kg to 43.48±4.03 Bq/kg with mean value of 26.64±1.33 Bq/kg for 226Ra, 20.01±1.98 Bq/kg to 32.71±3.85 Bq/kg with the mean value 25.95±1.46 Bq/kg for 232Th and 81.70±33.59 Bq/kg to 259.20±38.80 Bq/kg with the mean value 164.50±11.30 Bq/kg for 40K. These values were used to estimate the radiation hazard indices. The absorbed dose and annual effective dose were evaluated to assess the radiation risk due to the use of these sediments.

Au197(n,2n) reaction cross section in the 15–21 MeV energy range

The cross section of the $^{197}\mathrm{Au}(n,2n)^{196}\mathrm{Au}$ reaction has been determined at six energies ranging from 15.3--20.9 MeV by means of the activation technique, relative to the $^{27}\mathrm{Al}(n,\ensuremath{\alpha})^{24}\mathrm{Na}$ reaction. Quasimonoenergetic neutron beams were produced via the $^{3}\mathrm{H}(d,n)^{4}\mathrm{He}$ reaction at the 5.5 MV Tandem T11/25 accelerator laboratory of NCSR ``Demokritos''. After the irradiations, the induced $\ensuremath{\gamma}$-ray activity of the target and reference foils was measured with high-resolution HPGe detectors. The cross section for the high spin isomeric state (${12}^{\ensuremath{-}}$) was determined along with the sum of the ground (${2}^{\ensuremath{-}}$), the first (${5}^{+}$), and second (${12}^{\ensuremath{-}}$) isomeric states. Theoretical calculations were carried out with the codes empire 3.2.2 and talys 1.8. Optimum input parameters were chosen in such a way as to simultaneously reproduce several experimental reaction channel cross sections in a satisfactory way, namely the ($n,\mathrm{elastic}$), ($n,2n$), ($n,3n$), ($n,p$), ($n,\ensuremath{\alpha}$), and ($n$,total) ones.

Determination of uranium and thorium using gamma spectrometry: a pilot study

This paper presents the results of a pilot experiment aimed at standardizing procedures for the CPqCTR/UESC Gamma Spectrometry Laboratory (LEG) for the quantification of natural radioactive elements in solid environmental samples. The concentrations of 238U, 232Th and 40K in two sediment matrix belonging to the Caetité region were determined, by using the absolute method with uncertainties about 5%. The results were obtained using gamma spectrometry with a high-resolution p-type HPGe detector. As a closure, the absorbed dose, radium equivalent activity and the annual effective dose were calculated.

Natural radioactivity levels and evaluation of radiological hazards from Beni Haroun dam sediment samples, northeast Algeria

Levels of naturally occurring radioactivity in sediment samples of Beni Haroun dam have been investigated. The activity concentrations of 238U and 232Th decay chains and 40K primordial radionuclide have been measured using high-resolution HPGe detector. Activity concentrations of 226Ra, 232Th, and 40K radionuclides were found in the ranges 9–66, 14–37, and 177–288 Bq/kg with the mean values 24.67, 25.98, and 208.10 Bq/kg, respectively. Radiological hazard parameters were estimated based on the activity concentrations for 226Ra, 232Th, and 40K to find out any radiation hazard associated with the sediments. Correlation studies between pairs of radionuclides were performed and discussed, and the obtained results are compared with international recommended values.

Thermal neutron cross-section and resonance integral of the 152Sm(n,γ)153Sm reaction induced by pulsed neutrons

We measured the thermal neutron cross-section (σ0) and resonance integral (I0) of the 152Sm(n,γ)153Sm reaction relative to that of the 197Au(n,γ)198Au reaction. Sm and Au foils with and without a cadmium cover of 0.5mm were irradiated with moderated pulsed neutrons produced from the electron linac. The induced activities of the reaction products were determined via high energy resolution HPGe detector. The present results: σ0,Sm =212±8 b and I0,Sm =3.02±0.19kb are consistent with most of the existing reference data.

Determination of neutron capture cross sections of 232Th at 14.1 MeV and 14.8 MeV using the neutron activation method**Supported by Chinese TMSR Strategic Pioneer Science and Technology Project-The Th-U Fuel Physics Term (XDA02010100) and National Natural Science Foundation of China (11205076, 21327801)

The 232Th(n, γ)233Th neutron capture reaction cross sections were measured at average neutron energies of 14.1 MeV and 14.8 MeV using the activation method. The neutron flux was determined using the monitor reaction 27Al(n,α)24Na. The induced gamma-ray activities were measured using a low background gamma ray spectrometer equipped with a high resolution HPGe detector. The experimentally determined cross sections were compared with the data in the literature, and the evaluated data of ENDF/B-VII.1, JENDL-4.0u+, and CENDL-3.1. The excitation functions of the 232Th(n,γ)233Th reaction were also calculated theoretically using the TALYS1.6 computer code.

Measurements for Natural Radioactive Materials at the East & West banks of The River Nile

Soil samples were collected along the East and West banks of the River Nile region starting from Bait Al-mal in the West side and the second East bank of the River Nile Shambat. Gamma radiation measurements were performed using high resolution HPGe detector with low background PC multichannel spectrometer. The gamma measurements of the soil revealed the presence of the natural long-lived radioisotopes ²³⁸U, ²³²Th and ⁴⁰K. The ranges of their activity concentrations were 3.32±1.1~6.3±2.1 Bqkg^-1, 5.61±1.7~10.76±2.13 Bqkg^-1 and 180±7.77~291±11.6 Bqkg^-1 ‘respectively’. The other factors controlling the distribution of the detected natural radioisotopes have been discussed. Absorbed dose rates have been calculated for each location with range 15.27±0.82~21.07±1.53 nGyh^-1. Also, the estimated activity utilization indexes have been presented. The ratios between the detected radioisotopes have been calculated.

Natural radioactivity investigation in Dam sediments of northeast Algeria using gamma spectroscopy

Current research paper intends to estimate the natural radioactivity levels in sediments samples collected from Beni Haroun Dam in the northeast Algeria, using high resolution HPGe detector. The mean activity concentrations values measured for the radionuclides 232Th, 226Ra and 40K are 18.9 ± 1.9, 37.3 ± 2.7 and 149.9 ± 5.5 Bq/kg, respectively. The 137Cs anthropogenic radionuclide has been observed with maximum activity concentration value of 0.8 ± 0.4 Bq/kg, which is considered an insignificant amount. In order to assess the radiological threat of gamma radiations emitted by these radionuclides on the health of the population, absorbed dose rate, annual effective dose equivalent and radiation hazard indices were had been calculated. The obtained values are compared with the world wide average ones.

40K, 226Ra AND 228Ra SERIES IN BOVINE AND POULTRY FEED AND IN DICALCIUM PHOSPHATE (DCP) SAMPLES BY GAMMA-RAY SPECTROMETRY

The aim of this study is to determine the amounts of radionuclides' activity present in samples of feed for young and adult chicken and feed for dairy and beef cattle, as well as in dicalcium phosphate (DCP) (CaHPO4), used as a nutritional supplement for animal feed. Radioactivity in these samples is due to the presence of the 238U and 232Th radioactive series, as well as their daughter. In addition, as it is for environmental samples, the activity of 40K should be an important source of radioactivity in all analyzed samples. Gamma rays were measured using a standard spectroscopy system, with a high-resolution HPGe detector. Measured activities in feed samples ranged from 0.23 to 1.51 Bq.kg-1, 0.67 to 4.21 Bq.kg-1, 0.29 to 1.63 Bq.kg-1 and 236 to 402 Bq.kg-1 for 226Ra, 228 Ra, 228 Th and 40K, respectively. Measured activities in DCP samples were 46.6 Bq.kg-1, 83 Bq.kg-1, 4.20 Bq.kg-1 and 16.61 Bq.kg-1 for 40 K, 226 Ra, 228 Ra and 228 Th, respectively. Although 40K activity has reached hundreds of Becquerel in feed samples, it should not represent a risk to human health, not even to animals, since potassium is an essential mineral to living organisms.

Development of an absolute method for efficiency calibration of a coaxial HPGe detector for large volume sources

In this work an absolute method for the determination of the full energy peak efficiency of a gamma spectroscopy system for voluminous sources is presented. The method was tested for a high-resolution coaxial HPGe detector and cylindrical homogeneous volume source. The volume source is represented by a set of point sources filling its volume. We found that the absolute efficiency of a volume source can be determined as the average over its volume of the absolute efficiency of each point source.Experimentally, we measure the intrinsic efficiency as a function upon source-detector position. Then, considering the solid angle and the attenuations of the gamma rays emitted to the detector by each point source, considered as embedded in the source matrix, the absolute efficiency for each point source inside of the volume was determined. The factor associate with the solid angle and the self-attenuation of photons in the sample was deduced from first principles without any mathematical approximation.The method was tested by determining the specific activity of 137Cs in cylindrical homogeneous sources, using IAEA reference materials with specific activities between 14.2Bq/kg and 9640Bq/kg at the moment of the experimentation. The results obtained shown a good agreement with the expected values. The relative difference was less than 7% in most of the cases.The main advantage of this method is that it does not require of the use of expensive and hard to produce standard materials. In addition it does not require of matrix effect corrections, which are the main cause of error in this type of measurements, and it is easy to implement in any nuclear physics laboratory.

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.

Compton back scatter imaging for mild steel rebar detection and depth characterization embedded in concrete

A novel non-destructive Compton scattering technique is described to ensure the feasibility, reliability and applicability of detecting the reinforcing steel bar in concrete. The indigenously developed prototype system presented in this paper is capable of detecting the reinforcement of varied diameters embedded in the concrete and as well as up to 60mm depth, with the aid of Caesium-137(137Cs) radioactive source and a high resolution HPGe detector. The technique could also detect the inhomogeneities present in the test specimen by interpreting the material density variation caused due to the count rate. The experimental results are correlated using established techniques such as radiography and rebar locators. The results obtained from its application to locate the rebars are quite promising and also been successfully used for reinforcement mapping. This method can be applied, especially when the intrusion is located underneath the cover of the concrete or considerably at larger depths and where two sided access is restricted.

Natural and anthropogenic radioactivity levels and the associated radiation hazard in the soil of Oodalia Tea Estate in the hilly region of Fatickchari in Chittagong, Bangladesh.

Radioactivity in the soil of a tea garden in the Fatickchari area in Chittagong, Bangladesh, was measured using a high-resolution HPGe detector. The soil samples were collected from depths of up to 20 cm beneath the soil surface. The activity concentrations of naturally occurring 238U and 232Th were observed to be in the range of 27 ± 7 to 53 ± 8 Bq kg−1 and 36 ± 11 to 72 ± 11 Bq kg−1, respectively. The activity concentration of 40K ranged from 201 ± 78 to 672 ± 81 Bq kg−1, and the highest activity of fallout 137Cs observed was 10 ± 1 Bq kg−1. The average activity concentration observed for 238U was 39 ± 8 Bq kg−1, for 232Th was 57 ± 11 Bq kg−1, for 40K was 384 ± 79 Bq kg−1 and for 137Cs was 5 ± 0.5 Bq kg−1. The radiological hazard parameters (representative level index, radium equivalent activity, outdoor and indoor dose rates, outdoor and indoor annual effective dose equivalents, and radiation hazard index) were calculated from the radioactivity in the soil.

Effect of chemical environment on K shell binding energy of Ag and Sn

The effect of chemical environment on K shell binding energy of Ag and Sn has been studied by using external bremsstrahlung (EB). The spectrum of transmitted EB, recorded with high resolution HPGe detector spectrometer, shows a sudden drop in intensity at K edge along with unwanted Kβ1′ and Kβ2′ characteristic X-ray photons of the target. A modified sigmoidal function has been used to determine the K edge of Ag, Sn and their compounds to understand the effect of crystal structure on K shell binding energy.

New Measurements of the 241Am(n,2n)240Am Cross Section

The 241Am(n,2n)240Am reaction cross section has been measured at 10.4 and 10.8 MeV, relative to the 27Al(n,α)24Na reference reaction, using the activation technique. The irradiations were carried out at the 5 MV Tandem T11/25 accelerator laboratory of NCSR “Demokritos” with monoenergetic neutron beams provided by means of the 2H(d,n)3He reaction. The high purity Am target has been provided by IRMM, Geel, Belgium. The induced γ-ray activity of 240Am was measured with high resolution HPGe detectors.