High Purity Germanium Semiconductor Detector Research Articles

Evaluation of radionuclide impurities in several radiopharmaceuticals

Revisions to German radiation protection laws have resulted in updated limit values, which could affect the unrestricted release of waste produced by nuclear medicine therapy. In addition, signs of long-lived concomitant nuclides in 153Sm and 223Ra radiopharmaceuticals have been seen in the past. Therefore, the goal of this article was to analyze the radionuclidic purity of selected radiopharmaceuticals. 48 samples from 12 different radiopharmaceuticals were examined. A high purity germanium semiconductor detector (HPGe detector) was used for the qualitative and quantitative evaluation of concomitant nuclides. Various europium isotopes were identified in 90Y-citrate, 153Sm-Quadramet, 166Ho-QuiremSpheres, and 169Er-erbium citrate, with the greatest amount being found in 153Sm (7.0 ppm (152Eu), 8.4 ppm (154Eu), and 2.1 ppm (155Eu)). 169Yb was the most significant impurity in 169Er (513 ppm). In the case of 177Lu radiopharmaceuticals, there was a significant difference in the 177mLu content (0.8 ppm vs. 0.0024 ppm) between two different manufacturers. No concomitant nuclides could be found within the detection limits in the case of 90Y spheres, 223Ra, and 225Ac. The limit values for unrestricted release are exceeded manyfold in the case of the identified concomitant nuclides. As a result, alternative release procedures (extension of the decay time, specific release, release in the individual case) or transfer to collection facilities must be considered. Technical methods for reducing or preventing impurities could also be a possible solution. Consequences for patient radiation exposure were able to be ruled out.

Rare-earth elements distribution in Algerian soil samples using neutron activation analysis: Monte Carlo analytical method approach

ABSTRACT Rare-Earth Elements (REEs) are good tracers to study the process of watersheds’erosion and soil redistribution. Neutron Activation Analysis (NAA) is one of the best methods for the low detection limit analysis of REE such as La, Nd, Eu, Tb, Yb and Hf. In the present work, a combination of an experimental approach and a Monte Carlo calculation in order to establish in one hand the irradiation parameter and on the other hand high precision measurement of REEs’contents in soils was implemented. The HPGe detector’s parameters were optimised by comparing the measured efficiencies with those obtained by Monte Carlo simulations. A good agreement was found between Monte Carlo simulations and the experimental results. The irradiation parameters were measured experimentally; the thermal flux (φth) and the epithermal flux (φepi) were corrected by means of the flux monitor. For the determination of REEs’ interfering elements, the capture reaction (n, γ) was corrected by the contribution of the uranium (n, fission) reaction. In order to apply this model in the soil redistribution, the samples were irradiated for 4 h at the NUR nuclear research reactor under a neutron flux of 2.36 × 1013 n cm−2 s−1. The irradiated samples were measured by gamma spectrometry, using a HighPurity Germanium semi-conductor detector (HPGe) which resolution is 1.8 keV at 1332.5 keV of 60Co. The obtained spectra were analysed using Genie 2000 software which is well indicated in the processing of gamma-ray spectra. The determination of the REEs’ concentrations was achieved with good precision. These results allowed us to identify the areas of the studied watershed where erosion and/or accumulation take place.

Basic consideration of a nuclear power monitoring system using neutron-induced prompt gamma rays

ABSTRACTMonitoring only neutron flux in a nuclear reactor core has an advantage of offering reactor power monitoring accuracy. We started the development of a new nuclear instrumentation based on the measurement of prompt gamma rays emitted from metals placed at the neutron flux monitoring positions. The thermal neutron flux at the position of each placed metal piece can be monitored by measuring the prompt gamma rays as the count rate of each energy. The gamma-ray energy range was limited from 6 to 10 MeV to mitigate the interference of environmental gamma rays. Four metals, Ti, V, Ni, and Cu, were chosen as candidates in consideration of their neutron emission rates and self-absorption. In an experiment with a high-purity germanium semiconductor detector, we considered the identification of individual peak energies in an assumed situation where prompt gamma rays were emitted from the four different metals at the same time. Energy resolutions of the peak with the largest energy gap from the nearest energy peak of the other candidate metals were smaller than the gap. Thus, we confirmed that at least one peak for each candidate metal was able to be separated from the peaks derived from other candidate metals.

THE CONTENT OF NATURAL RADIONUCLIDES IN TECHNOLOGICAL RESIDUES OF UKRAINIAN INDUSTRIES.

to assess the naturally occurring radioactive materials (NORM) content in industrial waste in Ukraine and assess which industries should be a subject for the regulatory oversight. Sampling and analysis followed the same procedure in all cases. 250 samples were taken in total. High- resolution gamma spectrometry system ORTEK (US) with the high-purity germanium semiconductor detector (HPGe) were used for sample measurements. AMERSHAM (Germany) standard source was used for calibration of the gamma spectrometer. The estimated minimum detected activity for the measurement time of 3600 s was 0.5 Bq/kg for Thorium-232, and Radium-226 and 1.5 Bq/kg for Potassium-40. Industries with the potential NORM content in their waste were approached in this research. 32 enterpris- es were the subject for investigation. It has been established average content of NORM in waste iron ore enterpris- es varies from 210 to 100 Bq/kg, 226Ra - from 14 to 45 Bq/kg, 40K - from 21 to 350 Bq/kg, 232Th - from 5 to 26 Bq/kg and 238U - from 19 to 48 Bq/kg. It was determined the content of NORM in waste is lower than the exemption lev- els. The average concentration of individual radionuclides does not exceed 10-20 Bq/kg. The assessment of the NORM average activity concentration in sludge and waste samples from different spots of the industrial site esti- mated that values may differ as much as 3 times, with average activity of 8,440 Bq/kg for 226Ra, 28,600 Bq/kg for 232Th, 11,000 Bq/kg for 210Pb. The NORM level in pipe sediments and silts of oil exceed the established exemption lev- els and range as follows: 210Pb 3-11 kBq/kg, 226Ra 2.9-8.4 kBq/kg, 232Th 0.8-2.8 kBq/kg, 226U 0.18-6.9 kBq/kg. Monitoring of the NORM levels in wastes has identified the need to establish regulatory control and oversight of the oil industry in the country.

Albedo factor determination of rare-earth oxides

ABSTRACTGamma-ray albedo factors of rare-earth oxides were determined experimentally. The detection of albedo factors for selected materials includes albedo number, albedo energy and albedo dose calculations. 59.54 keV gamma rays of 5 Ci annular 241Am were used as a gamma source. Gamma rays were scattered by selected samples and collected by High Purity Germanium semiconductor detector. The albedo factors were plotted as a function of atomic number of target materials.

An experimental study on the angular dependence of coherent to Compton scattering differential cross-section ratios of calcium

The coherent to Compton scattering cross-section ratio of calcium was measured experimentally for several polar scattering angles (90°, 100°, 110°, 120°, and 130°) and azimuthal scattering angles (30°, 20°, 10°, 0°, -10°, and -20°). A high purity germanium semiconductor detector with a resolution of 199.6 eV at 5.9 keV was used. The theoretical values of the coherent to Compton scattering differential cross-section of calcium were calculated on the basis of nonrelativistic form factors, relativistic form factors, and S-matrix theories. It was observed that the experimental results were most compatible with the nonrelativistic form factor theory.

Contents of macro-, microelements and long-lived radionuclides in the medicinal plants belonging to the wetland community of Siberian region, Russia

Studied contents of macro-, microelements and long-lived radionuclides in the following medicinal plants belonging to the wetland community of Siberian region, Russia: Sphagnum fuscum (Schimp.) Klinggr., Sphagnum balticum (Russ.) Russ. ex С. Jens., Polytrichum strictum Brid., Pinus sylvestris L., Pinus sibirica Du Tour, Betula pubescens Ehrh., Andromeda polifolia L., Ledum palustre L., Oxycoccus palustris Pers., Rubus chamaemorus L., Vaccinium uliginosum L., Comarum palustre L., Chamaedaphne calyculata (L.) Moench. Samples were collected in the sphagnum wetlands of Tomsk region and Khanty-Mansi Autonomous Okrug. For the purpose of research, we used roots, shoots and bark of the plants in the Pinophyta and Magnoliophyta species and turf of the Bryophyta species. The content of macro-, microelements in the plants was determined by an atomic emission spectrometer with inductively coupled plasma “iCAP 6300 Duo” of the “Thermo Scientific” company. The specific activities of the long-lived radionuclides Th-232, K-40, Ra-226, Cs-137 were measured by a gamma-ray spectrometric complex with a high purity germanium semiconductor detector by “ORTEC” (AMETEK) and a digital analyser “ORTEC DSPEC LF”. The obtained results of the element content are useful when selecting a medicinal plant species (or part thereof) which may be used in preparation of new medicinal drugs.

Quantitative Assessment of 131I in Soil Originating from the Fukushima Daiichi Nuclear Power Plant Disaster Using a Germanium Semiconductor Detector

Abstract In the accident at the Fukushima Daiichi Nuclear Power Plant (NPP) that accompanied the Great East Japan Earthquake on the 11th of March, 2011, large amounts of radionuclides were released into the atmosphere. Among these released radionuclides, there was an especially large amount of 131 I and 137 Cs. Two years have passed since the accident, and the decontamination of the deposited radionuclides has become a significant task. In the present study, a quantitative evaluation of the depth distribution of 131 I and 137 Cs in the soil using a high-purity germanium semiconductor detector was performed with soil samples collected at Adatara, Fukushima on April 30, 2011. Along with 131 I and 137 Cs, the concentration of radionuclides showed a maximum at a depth of 1 cm under the soil surface, and this attenuated to approximately 1/6 the concentration at the surface layer at a depth of 3 cm. In other words, the deposition of radionuclides was in a comparatively shallow portion of the soil. Additionally, soil surface samples were obtained from various observation sites, and a quantitative evaluation of the concentrations of radionuclides such as 131 I was carried out. The results confirm a high concentration, more than 7000 Bq/kg, of 131 I in samples collected at Nihonmatsu City on April 17, 2011 and samples collected on May 2, 2011 at Iwaki City. The concentration became higher as the distance from the NPP became smaller. However, the measurement values were variable also depending on the diameter of soil particle.

Measurement of effective atomic number and Rayleigh-to-Compton cross-section ratio for 145 keV gamma photons

The effective atomic numbers of composites and Rayleigh-to-Compton cross-section ratio of elements, in the range 6 ≤ Z ≤ 82 for 145 keV gamma photons, are determined experimentally. An HPGe (high purity germanium) semiconductor detector is placed, at scattering angle of 90°, to record the spectra originating from interactions of incident gamma photons with the target under investigations. The intensity ratio of Rayleigh-to-Compton scattered peaks, corrected for photo-peak efficiency of gamma detector and absorption of photons in the target and air column, is plotted as a function of atomic number and a best fit-curve is constituted. From this fit-curve, the respective effective atomic numbers of the scientific samples are determined. The measured values of cross-section ratio increases non-linearly with increase in atomic number and are found to agree with theoretical predictions based upon non-relativistic form factor, relativistic form factor, modified form factor and S-matrix theory.

An experimental study on cross-section ratio of coherent to incoherent scattering for 145 keV incident gamma photons

The coherent (Rayleigh) to incoherent (Compton) scattering cross-section ratio of elements, in the range 6 ≤ Z ≤ 82, are determined experimentally for 145 keV incident gamma photons. An HPGe (High purity germanium) semiconductor detector is employed, at scattering angle of 50°, 70° and 90°, to record the spectra originating from interactions of incident gamma photons with the target under investigation. The intensity ratio of Rayleigh to Compton scattered peaks observed in the recorded spectra, and corrected for photo-peak efficiency of gamma detector and absorption of photons in the target and air, along with the other required parameters provides the differential cross-section ratio. The measured values of cross-section ratio are found to agree with theoretical predictions (corresponding to 4.939, 6.704 and 8.264 Å−1 photon momentum transfer) based upon non-relativistic form factor, relativistic form factor, modified form factor and S-matrix theory.

名古屋市における食品の放射性物質検査

Following the Fukushima nuclear plant accident in Mar. 2011, the examination of radioactive contamination in foods is being carried out in Nagoya. During the period between 30 Mar. 2011 and 31 Oct. 2012, a total of 300 food samples were collected and the concentrations of radioactive nuclides were determined by means of γ-ray spectrometry using a high-purity germanium semiconductor detector. The results of analysis indicate that the concentrations of radioactive iodine (I) and cesium (Cs) were below the regulatory limits. Radioactive I ((131)I) was detected in 7 samples which belonged to the categories of green and yellow vegetables and other vegetables. Radioactive Cs ((134)Cs and (137)Cs) was detected in 60 samples which belonged to the categories of rice and its processed products, potatoes and its processed products, nuts and seeds, green and yellow vegetables, other vegetables, fruits, mushrooms, fishes and shellfishes, processed sea foods, meat, milk and dairy products and other beverages.

Background radiation and individual dosimetry in the costal area of Tamil Nadu, India

South coast of India is known as the high-level background radiation area (HBRA) mainly due to beach sands that contain natural radionuclides as components of the mineral monazite. The rich deposit of monazite is unevenly distributed along the coastal belt of Tamil Nadu and Kerala. An HBRA site that laid in 2×7 m along the sea was found in the beach of Chinnavillai, Tamil Nadu, where the maximum ambient dose equivalent reached as high as 162.7 mSv y(-1). From the sands collected at the HBRA spot, the high-purity germanium semi-conductor detector identified six nuclides of thorium series, four nuclides of uranium series and two nuclides belonging to actinium series. The highest radioactivity observed was 43.7 Bq g(-1) of Th-228. The individual dose of five inhabitants in Chinnavillai, as measured by the radiophotoluminescence glass dosimetry system, demonstrated the average dose of 7.17 mSv y(-1) ranging from 2.79 to 14.17 mSv y(-1).

Measurement of the effective atomic number of composite materials using Rayleigh to Compton scattering of 279 keV gamma rays

In the present work, to determine the effective atomic number of composite materials of known composition such as brass, bronze, soldering material, perspex and bakelite, the scattering of 279 keV γ-rays is studied using a high-resolution HPGe (high purity germanium) semiconductor detector placed at 50° to the incident beam. The experiment is performed on various elements with atomic number satisfying, 13 ≤Z ≤ 79, for 279 keV incident photons. The intensity ratio of Rayleigh to Compton scattered peaks, corrected for photo-peak efficiency of the γ detector and absorption of photons in the target and air, is plotted as a function of atomic number and constitutes a fit curve. From this fit curve, the respective effective atomic numbers of the composite materials are determined. The agreement of measured values of the effective atomic number with the theoretical calculations is found to be quite satisfactory.

Temporal instabilities associated with a planar high purity germanium detector

Experiments have been performed which show that a grooved planar high purity germanium semiconductor detector may give rise to time variant counting rates in energy regions below prominent spectral peaks. It is postulated that this effect is due to prolonged or incomplete charge collection in the vicinity of the bottom of the groove, and is caused by distortions in the applied electric field in this region. Such effects may lead to changes in the minimum detectable count rate in X-ray fluorescence measurements; these can be reduced by collimating incident photons on the central region of the detector but the resulting reduction in efficiency lowers the overall sensitivity.

Cross sections for production of the 15.10-MeV and other astrophysically significant gamma-ray lines through excitation and spallation of 12C and 16O with protons.

The ratio of the flux of 15.10-MeV gamma rays to the flux of 4.438-MeV gamma rays resulting from excitation of the corresponding states in $^{12}\mathrm{C}$ is a sensitive measure of the spectrum of the exciting particles produced in solar flares and other cosmic sources. These gamma rays are produced predominantly by interactions with $^{12}\mathrm{C}$ and $^{16}\mathrm{O}$, both of which are relatively abundant in the solar photosphere. Gamma-ray production cross sections for proton interactions have been reported previously for all important channels except for the production of 15.10-MeV gamma rays from $^{16}\mathrm{O}$. The first reported measurement of the 15.10-MeV gamma-ray production cross section from p${+\mathrm{}}^{16}$O is presented here. A cyclotron was employed to produce 40-, 65-, and 85-MeV protons which interacted with ${\mathrm{CH}}_{2}$ and BeO targets. The resultant gamma-ray spectra were measured with a high-purity germanium semiconductor detector at 70, 90, 110, 125, and 140 deg relative to the direction of the incident beam for each proton energy. Other gamma-ray lines resulting from direct excitation and spallation reactions with $^{12}\mathrm{C}$ and $^{16}\mathrm{O}$ were observed as well, and their gamma-ray production cross sections, several of which have not been reported previously, are presented. The results are compared with previously reported measurements, as available.

A balloon-borne high-resolution spectrometer for observations of gamma-ray emission from solar flares

The design, development, and balloon-flight verification of a payload for observations of gamma-ray emission from solar flares are reported here. The payload incorporates a high-purity germanium semiconductor detector, standard NIM and CAMAC electronics modules, a thermally stabilized pressure housing, and regulated battery power supplies. The flight system is supported on the ground with interactive data-handling equipment comprised of similar electronics hardware. The modularity and flexibility of the payload, together with the resolution and stability obtained throughout a 30 h flight, make it readily adaptable for high-sensitivity, long-duration balloon flight applications.