High Purity Germanium Gamma-ray Detector Research Articles

Evaluation of Environmental Radioactivity and Estimation of Radiation Exposure in the Niankhene Agricultural Field in Senegal

The presence of radioactivity, originating from both natural and human-induced sources, is widespread in varying degrees throughout the Earth's crust. Soil, as a fundamental component of the Earth's crust, serves as an ongoing source of exposure to humans. The level of radioactivity in soil is influenced by factors such as soil composition and land usage. It is expected that barren soil exhibits distinct radioactivity levels compared to cultivated soil. To investigate the radioactivity levels within barren soil, a study was conducted on approximately 11 hectares of soil samples located in Niankhene. Utilizing gamma ray spectrometry methodology with a high purity germanium gamma-ray detector, activity concentration levels of radionuclides including <sup>40</sup>K, <sup>137</sup>Cs, <sup>226</sup>Ra, and <sup>232</sup>Th were evaluated. A total of 16 soil samples were collected at depths ranging from 0 to 40 cm with 20 cm intervals. The activity concentrations of the radionuclides were observed as follows: <sup>40</sup>K ranged from below the limit of detection to 34.7 Bq.kg<sup>-1</sup>; <sup>137</sup>Cs varied from 0.06 to 0.80 Bq.kg<sup>-1</sup>; <sup>226</sup>Ra measured was between 7.49 and 101.56 kg<sup>-1</sup>; and <sup>232</sup>Th ranged 0.33 and 12.68 Bq.kg<sup>-1</sup>. The total dose radiation exposure were 27 nGy/h in this study. Before conducting radiometric measurements, chemical analyses were performed to determine the concentrations of Na, Ca, and Mg, along with measurements of electrical conductivity and pH levels of the soil samples.

Radiological Hazard Assessment of High-Level Natural Radionuclides in Surface Sediments Along Red River, Vietnam.

The Red River is one of the largest rivers that plays an important role in the economic development of North Vietnam. There are many radionuclides bearing rare earth, uranium ore mines, mining industrial zones and magma intrusive formations along this river. The contamination and accumulation of radionuclides could exist at high concentration in surface sediments of this river. Thus, the present investigation aims to study the activity concentrations of 226Ra, 232Th (228Ra), 40K, and 137Cs in Red River surface sediments. Thirty sediment samples were collected, and their activity concentration was calculated using high-purity germanium gamma-ray detector. The observed results ranged from 51.0 ± 2.1 to 73.6 ± 3.7 for 226Ra, 71.4 ± 3.6 to 103 ± 5.2 for 232Th, 507 ± 24.0 to 846 ± 42.3 for 40K, and ND (not detected) to 1.33 ± 0.06Bq/kg for 137Cs, respectively. In general, the natural radionuclides concentration of 226Ra, 232Th (228Ra), and 40K is higher than the average world average values. This indicated that the natural radionuclides could contribute from similar and principal sources surrounding the upstream of Lao Cai where distributed uranium ore mines, radionuclide bearing rare earth mines, mining industrial zones and intrusive formations. Regarding the radiological hazard assessment, results of the indices computed such as absorbed gamma dose rate (D), the excess lifetime cancer risk (ELCR), and the annual effective dose equivalent (AEDE) were nearly two times higher than world average values.

Natural radioactivity and radiological risks of common building materials used in Semnan Province dwellings, Iran

Impact assessment of building materials is a focused topic in the field of radioecology. A radiological survey has conducted to monitor radioactivity of most common building materials in Semnan Province, Iran, and assess the radiation risk. Activity concentrations of 226Ra, 232Th, and 40K were measured in 29 samples including nine commonly used building materials that were collected from local suppliers and manufacturers, using a high purity germanium gamma-ray detector. The activity concentrations of 226Ra, 232Th, and 40K varied from 6.7±1 to 43.6±9, 5.9±1 to 60±11, and 28.5±3 to 1085±113 Bq kg−1 with averages of 26.8±5, 22.7±4, and 322.4±4 Bq kg−1, respectively. By applying multivariate statistical approach (Pearson correlation, cluster, and principal component analyses (PCA)), the radiological health hazard parameters were analyzed to obtain similarities and correlations between the various samples. The Pearson correlation showed that the 226Ra distribution in the samples is controlled by changing the 232Th concentration. The variance of 95.58% obtained from PCA resulted that the main radiological health hazard parameters exist due to the concentration of 226Ra and 232Th. The resulting dendrogram of cluster analysis also shows a well coincidence with the correlation analysis.

Applications of HPGe-detected high energy gamma rays toward quantifying neutron emission rates and 234U enrichment in UF6 cylinders

This study presents a 234U enrichment meter that uses high energy gamma and neutron count rate as measured by a portable, high-purity germanium gamma ray detector. Twenty-one 30B cylinders containing UF6 of varying origin were analyzed with an HPGe detector for high-energy gamma ray and neutron counts. Excellent correlations (R2≥ 0.95) between various regions of ≥3.0 MeV gamma rays, neutron count rate, and uranium enrichment were found. These neutron and high-energy gamma data are used to create calibration-dependent enrichment meters for 234U. The 234U enrichment calculated from the neutron count rate and 4 – 6 MeV gamma count rate is more accurate than methods that rely on the 120.9 keV peak which is strongly attenuated inside commercial sized UF6 cylinders. These neutron and high-energy gamma enrichment calculators can also be used to determine a 235U enrichment, assuming mass-based enrichment from natural uranium, but the results are not as accurate as the traditional 185.7 keV peak enrichment meter.

Rapid separation of Po-210 from Pb-210 based on the usage of a commercial Sr-Specific chromatographic resin

The efficient extraction of small quantities of 210Po is necessary for preparing 210Po standard reference materials. Herein, a commercially available strontrium-specific chromatographic resin (Sr spec resin) was used to rapidly and selectively extract 210Po from a 210Pb–210Bi-210Po mixture, and the distribution ratios of Pb, Bi, and 210Po on Sr spec resin were probed using batch experiments. In contrast to 210Pb and 210Bi, 210Po was retained on the Sr spec cartridge in 8 M HCl and was then effectively eluted by 0.1 M HNO3. The contents of 210Pb and 210Bi in the thus obtained 210Po solution were checked using a high purity germanium gamma-ray detector and the corresponding decay curve, respectively, and were found not to exceed 2%. Moreover, the 210Pb and 210Bi eluates could be used to regenerate 210Po by the same method after a certain time period. Therefore, the extracted 210Po solution was suitable for the preparation of the 210Po standard area source and 210Po standard reference materials.

Production of Ga-68 with a General Electric PETtrace cyclotron by liquid target

PurposeIn recent years the use of 68Ga (t1/2 = 67.84 min, β+: 88.88%) for the labelling of different PET radiopharmaceuticals has significantly increased. This work aims to evaluate the feasibility of the production of 68Ga via the 68Zn(p,n)68Ga reaction by proton irradiation of an enriched zinc solution, using a biomedical cyclotron, in order to satisfy its increasing demand. MethodsIrradiations of 1.7 Msolution of 68Zn(NO3)2 in 0.2 N HNO3 were conducted with a GE PETtrace cyclotron using a slightly modified version of the liquid target used for the production of fluorine-18. The proton beam energy was degraded to 12 MeV, in order to minimize the production of 67Ga through the68Zn(p,2n)67Ga reaction. The product’s activity was measured using a calibrated activity meter and a High Purity Germanium gamma-ray detector. ResultsThe saturation yield of68Ga amounts to (330 ± 20) MBq/µA, corresponding to a produced activity of68Ga at the EOB of (4.3 ± 0.3) GBq in a typical production run at 46 µA for 32 min. The radionuclidic purity of the68Ga in the final product, after the separation, is within the limits of the European Pharmacopoeia (>99.9%) up to 3 h after the EOB. Radiochemical separation up to a yield not lower than 75% was obtained using an automated purification module. The enriched material recovery efficiency resulted higher than 80–90%. ConclusionsIn summary, this approach provides clinically relevant amounts of68Ga by cyclotron irradiation of a liquid target, as a competitive alternative to the current production through the68Ge/68Ga generators.

Pulse tube refrigeration for detectors

High purity germanium (HPGe) gamma-ray detectors are used for nondestructive assay. Liquid nitrogen (LN2), a cryogen, is commonly used to cool these detectors. Cryogen use is associated with several health risks and operational problems. This has prompted the development of cryogen-free refrigeration. A new generation of commercial pulse tube refrigerator (PTR) has been developed during the last decade. A unique feature of the PTR is the absence of cold moving parts. This significantly reduces the generated noise and vibration. In the following report, LN2, a modified Joule–Thompson cooler, and a PTR unit are examined and their cooling effectiveness with HPGe gamma-ray detectors compared. Overall, PTR is an engineering equivalent to LN2 and modified Joule–Thompson cooler systems used in gamma spectroscopy and eliminate the health and physical hazards associated with LN2 systems without adding hazards.

Risk reduction benefits of cryogen-free refrigeration

High Purity Germanium (HPGe) gamma-ray detectors are used at Los Alamos National Laboratory's Plutonium Facility (TA-55) for nondestructive assay. Liquid nitrogen (LN2), a cryogen, is commonly used to cool these detectors. Cryogen use is associated with several health risks and operational problems. This has prompted the development of cryogen-free refrigeration. Although the efficacy of the coolers has been proven for use with HPGe detectors, the health and safety aspect implications have not been studied. Both LN2 and mechanical coolers were examined and their application effectiveness on health and safety aspects in HPGe gamma-ray detector use at TA-55 was compared. Overall, cryogen-free refrigeration is an engineering equivalent to LN2 systems used in gamma spectroscopy and eliminates the health and physical hazards associated with LN2 systems without adding hazards.

Natural radioactivity levels (K, Th and Ra) in some areas of Punjab, India

Radioactivity, natural and man-made, is omnipresent in the earth's crust in different amounts. Natural radioactive materials under certain conditions can reach hazardous radiological levels. So, it becomes necessary to study the natural radioactivity levels in soil to assess the dose for the population in order to know the health risks and to have a baseline for future changes in the environmental radioactivity due to human activities. 226Ra, 232Th and 40K analysis has been carried out in soil samples collected from some areas of Punjab, India using gamma-ray spectrometry. Phe technique of gamma ray spectrometry was applied using high purity germanium gamma-ray detector and a PC based MCA. Radium equivalent activities are calculated for the analyzed samples to assess radiation hazards arising due to the use of these soil samples in construction of dwellings. Phe measured activity in the soil ranges from 23.17 to 57.87 Bq kg−1, 59.03 to 160.40 Bq kg−1 and 228.06 to 501.03 Bq kg−1 for 226Ra, 232Ph and 40K with mean values of 37.93, 84.47 and 351.17Bqkg−1 respectively. It has been observed that on the average the outdoor terrestrial gamma air absorbed dose rate is about 84.65nGyh−1.

Assessment of radiological hazards of clay bricks fabricated in the Punjab province of Pakistan

The Punjab is the most populous among the four provinces of Pakistan, which has around 72 million of people and 205 344 km(2) of land. The majority of the population of this province lives in houses made of clay bricks that contain variable amounts of naturally occurring radioactive material (NORM). The concentration level of NORM in clay bricks used to construct dwellings may pose health hazards to inhabitants if it exceeds the permissible limits. For radiological surveillance, activity concentrations of the primordial radionuclides (40)K, (226)Ra and (232)Th were measured in 140 brick samples collected from 35 districts of the Punjab province. A high-purity germanium gamma-ray detector coupled with a personal computer-based multichannel analyzer was employed for the measurement of activity concentrations of primordial radionuclides in the brick samples. The province-wide average activity concentrations and the range (given in parenthesis) of (40)K, (226)Ra and (232)Th were found to be 624 ± 133 (299-918), 35 ± 7 (21-47) and 42 ± 8 (22-58) Bq kg(-1), respectively. The values lie within the range of activity concentration values for clay bricks of some countries of Asia. Potential radiological constraint was checked in the form of hazard indices calculated from the measured activity concentrations; the indices were found to be less than their limiting values. Indoor external dose was calculated for a standard size room made of clay bricks, and the dose rate was 159 ± 30 (83-219) nGy h(-1). The average value of the dose rate is comparable to that of Asian countries and is about twice the worldwide average value. Annual effective dose E(ff) in the bricks-made room was calculated and the average value of the dose was 0.80 mSv y(-1), which is about twice the worldwide background value of 0.41 mSv y(-1).

Radiometric analysis of farmed fish (sea bass, gilthead bream, and rainbow trout) from Tenerife Island, Spain.

This study analyzed the content of gamma-emitting radionuclides in fish farmed on the island of Tenerife (Canary Islands, Spain). The fish species included in this study were sea bass, gilthead bream, and rainbow trout. The first two species are produced in offshore enclosures, while the third is produced in a freshwater fish farm. All measurements were performed using two high-purity germanium gamma-ray detectors. The content of gamma-emitting radionuclides in the fodder used to feed the different species of farmed fish studied was also determined. The following nuclides were often detected in the analyzed samples: 137Cs, 40K, 235U, 228Ac, 214Bi, 208Tl, 212Pb, and 214Pb. As a complement to this analysis, 210Po concentrations in two fish samples were determined by alpha spectrometry. The nuclide presenting the highest concentration was, as expected, the naturally occurring 40K, with an average concentration of 0.13 +/- 0.01 Bq/g (wet weight) (Bq/gww) in gilthead bream and sea bass and 0.12 +/- 0.01 Bq/gww in rainbow trout. The 235U concentrations determined in the same fish species were 0.6 +/- 0.5, 0.8 +/- 0.7, and 1.6 +/- 1.0 mBq/gww, respectively. This nuclide is seldom reported in fish samples. The concentrations of 137Cs (the only artificial nuclide determined in this study) in gilthead bream and sea bass were 0.026 +/- 0.006 and 0.044 +/- 0.01 mBq/gww, respectively. In addition to the radiometric analysis, the contribution of the analyzed nuclides to the effective dose from the mean daily intake of the fish was calculated. The calculated contribution, in terms of dose per person, produced by intake of the analyzed fish was 0.8 microSv/year. This value does not represent a significant risk to the local population.

RADIOACTIVE ROCK PHOSPHATE: THE FEED STOCK OF PHOSPHATE FERTILIZERS USED IN PAKISTAN

The existence of natural radioactivity in phosphate fertilizers originates from the rock phosphate that is used as a feed stock for the manufacturing of various types of phosphate fertilizers. Gamma ray activity mass concentrations have been determined in phosphate rock and fertilizer samples collected from different fertilizer manufacturing factories and suppliers in Pakistan. The technique of gamma ray spectrometry was applied using a HPGe (high purity germanium) gamma ray detector coupled with a personal computer (PC) based multichannel analyzer (MCA). The specific activity values of 40K, 226Ra, and 232Th were widely distributed in the rock and fertilizer samples. Activity mass concentrations of 238U (226Ra) in the rock phosphate from Jordan and Pakistan were 428 +/- 11 and 799 +/- 10 Bq kg(-1), respectively, and that in the triple-superphosphate fertilizer was 701 +/- 21 (-1), which was greater than the average values of 238U (226Ra) for other types of fertilizers under study. The concentrations of 40K and 232Th were of the order of background level on the Earth's crust. Chemical analysis for concentration of different constituents in rock phosphate was also carried out. The higher the concentrations of P2O5 and K2O were, the higher the specific activities of 226Ra and 40K were, respectively, in the rocks under study. The amount of radioactivity in the rock phosphate is a source of continuous exposure to radiation, which varies widely depending upon the origin and grade of rock; therefore, radiation dose rate has been estimated. The values of dose rate and other derived quantities were many folds larger than the limits specified for those quantities.

Natural environmental radioactivity and estimation of radiation exposure from saline soils

The study was conducted for the investigation of amount of radioactivity in the barren and cultivated soil of Bio saline Research Station in Pakka Anna, established by Nuclear Institute for Agriculture and Biology (NIAB) in 1990, 34 km. away from the city of Faisalabad, in the Punjab province of Pakistan. The studies were done on an area of about 100 hectares of two types of virgin and fertilized saline soils. The technique of gamma ray spectrometry was applied using HPGe (high purity germanium) gamma ray detector and a PC based MCA. Activity concentration levels due to 40 K, 137 Cs, 226 Ra and 232 Th were measured in 250 saline soil samples collected at a spacing of about 4 hectares at the depth level of 0–25 cm. with a step of 5 cm. depth. Activity concentrations ranges of the concerned radionuclides for both of the soils were as follows: 40 K, for virgin and cultivated saline soil was 500−610.2 and Bq/kg 560.2−635.6 respectively; 137 Cs, 3.57−3.63 and 1.98−5.15 Bq/kg 238 U, 26.3−31.6 and 30.3−38.7 Bq/kg, and 232 Th, 50.6−55.3 and 50.6−64.0 Bq/kg respectively. The absorbed dose rate in air lies in the region 63-73 nGyh -1 and 68-83 nGyh -1 for virgin and fertilized soils respectively. This indicates that this region lies in the area of higher radiation background, while comparing with the worlds’ average. The slightly higher value of dose in the fertilized farm may be due to the use of fertilizers for cultivation. Before the radiometric measurements, chemical analysis for concentration of Na, Ca and Mg was also carried out along with the measurement of electrical conductivity and pH of the soil samples.

Measurement of environmental radioactivity for estimation of radiation exposure from saline soil of Lahore, Pakistan

Radioactivity, natural and man made, is omnipresent in the earth's crust in different amounts. The soil on the earth's crust is a source of continuous exposure to human beings. The amount of radioactivity in soil depends upon the type of soil and its uses. The soil of barren area should show different amount of radioactivity when compared with that of the cultivated soil. For the investigation of amount of radioactivity in the barren soil, an area of about 60 h of saline soil was selected in Rakh Dera Chal near the city of Lahore in the Punjab province of Pakistan. The technique of gamma ray spectrometry was applied using high purity germanium gamma-ray detector and a PC based MCA. Activity concentration levels due to 40 K, 137 Cs, 226 Ra and 232 Th were measured in 125 saline soil samples collected at a spacing of about 4 ha at the depth level of 0– 25 cm with a step of 5 cm depth. Activity concentrations of the concerned radionuclides were as follows: 40 K , 524.84– 601.62 Bq kg −1 , 137 Cs , not detected (less than the lower detection limit), 226 Ra , 24.73– 28.17 Bq kg −1 , and 232 Th , 45.46– 52.61 Bq kg −1 . Before the radiometric measurements, chemical analysis for concentration of Na, Ca and Mg was also carried out along with the measurement of electrical conductivity and Ph of soil samples.

Hole traps in germanium crystals

Hole trapping in lithium-drifted and high-purity germanium gamma-ray detectors are found consistently in crystals that show a certain kind of etch pit. These pits are shallow and featureless, and appear to be associated with the presence of silicon and oxygen in the melt during growth. A crystal containing as few as 10 6 of these defect sites per cm 3 will exhibit unacceptable hole trapping. No other correlation between these shallow pits and detector performance has been observed.