HPGe Gamma-ray Spectrometer Research Articles

A highly efficient HPGE gamma-ray spectrometer for investigating ββ decay to excited states

A new low-background spectrometer based on a HPGe detector with a sensitive volume of 600 cm3 is developed to investigate rare nuclear processes such as resonance neutrinoless double electron capture and two-neutrino double beta decay to excited states of daughter nuclei. The spectrometer is installed at the Modane underground laboratory (France) at a depth of 4800 m w.e. The spectrometer background is measured and the spectrometer sensitivity is determined for measuring sources of double beta decay.

Analytical study of radionuclide concentration and radon exhalation rate in market available building materials of Ramsar

Samples of structural and covering market available building materials from Ramsar, a northern city of Iran, were analyzed for their radon exhalation rate using an active radon gas analyzer with an emanation container. The radon exhalation rate varied from below the minimum detection limit of 0.01 to 0.31 Bq·m−2·h−1 with an average of 0.08 Bq·m−2·h−1. The 226Ra, 232Th, and 40K contents were also measured using a high resolution HPGe gamma-ray spectrometer system. The radionuclides contents varied from below the minimum detectable activity up to 73.5, 169, and 1,350 Bq.kg−1, with the average value of 16 ± 6, 25 ± 11, and 280 ± 101 Bq.kg−1, respectively. It was concluded from the results that some granite samples along with the block sample were the main source of radon exhalation rate, and the mean values of 226Ra, 232Th, and 40K in building material samples are below the world average values. Therefore, the use of these market available building materials in construction of Ramsar dwellings is considered to be safe for human habitation.

The Radioactivity Levels and Safety Assessment of Building Materials in Nanjing, Jiangsu Province, China

In order to invetigate the natural radioactivity levels of typical building materials in Nanjing, Jiangsu Province,China, the specific activities of natural radionuclides (226Ra,232Th and40K) in samples of building materials were measured by ORTEC HPGe gamma ray spectrometer. And the radium equivalent activity, the internal and external exposure index, and relative annual effective dose equivalents were also claculated. The average concentrations of all the samples ranged from 64 to 318.79 Bq·kg-1, 11.35 to 144.83 Bq·kg-1and 92.57 to 951.68 Bq·kg-1for226Ra,232Th and40K, respectively. Their average values were in the ranges: 0.33-1.50 for the internal exposure index (Ira); 0.29-1.51 for the external exposure index (Ir); 0.34-1.74 mSv·a-1 for HEextand 0.36-1.76 mSv·a-1for HEint. The average radium equivalent activity varied from 106.49 to 541.77 Bq·kg-1. According to the standard, most samples were in a lower radioactivity level expect a few of artificial tiles. But, we must perfect detection and management system of many materials to ensure radiation safety and physical health.

Cross equator transport of 137Cs from North Pacific Ocean to South Pacific Ocean ( BEAGLE2003 cruises)

The anthropogenic radionuclides such as 137Cs, 90Sr, 99Tc, 129I and some transuranics are important tracers of transport and biogeochemical processes in the ocean. 137Cs, with a half-life of 30 years, a major fission product present in a dissolved form in seawater, is a good tracer of oceanic circulation at a time scale of several decades. At WOCE P6 line along 30°S during the BEAGLE cruise in 2003, surface seawater (around 80 L) was collected a few meters below the ocean surface by a pumping system. Water column samples (from 5 to 20 L) were collected using a Rosette multisampling system and Niskin bottles. 137Cs was separated from seawater samples using ammonium phosphomolybdate (AMP) and analysed for 137Cs in low-level HPGe gamma-ray spectrometers. Results allowed to draw a detailed picture of the distribution of 137Cs in the South Pacific Ocean along P6 line. A 137Cs depth section was depicted from about 160 samples. 137Cs concentrations in the subsurface layers ranged from 0.07 ± 0.04 Bq m −3 to 1.85 ± 0.145 Bq m −3, high in the Tasman Sea and very low in the eastern region where upwelling occurs. Water column inventories of 137Cs from surface to 1000 dbar depth ranged from 270 ± 104 to 1048 ± 127 Bq m −2. It was concluded that the source of higher 137Cs concentration and inventories in the Tasman Sea was 137Cs deposited in the mid latitude of the North Pacific Ocean and transported across the equator during four decades.

Assessment of Radiation Dose Rates in the High Terrestrial Gamma Radiation Area of Selama District, Perak, Malaysia

Survey of terrestrial gamma radiation (TGR) dose rates have been conducted in Selama district, Perak, Malaysia. Themean value of TGR dose rate outdoor in Selama is (273 ± 133) nGy h-1. For the habited land, the mean TGR dose ratesoutdoor and indoor are (205 ± 59) nGy h-1 and (212± 64) nGy h-1 respectively. They contribute fatal cancer risk of 6.4 x10-5 per year to an individual in the area. The activity concentrations of 238U, 232Th, and 40K in the soil samples wereanalysed using a high resolution co-axial HPGe gamma ray spectrometer system. The values obtained range from 57 Bqkg-1 to 364 Bq kg-1 with the mean value of (178±95) Bq kg-1 for 238U; 207 Bq kg-1 to 625 Bq kg-1 with the mean value of(353±143) Bq kg-1 for 232Th, and 26 Bq kg-1 to 601 Bq kg-1 with the mean values of (273±133) Bq kg-1 for 40K.

Study on radionuclides in granite quarries of Bangalore rural district, Karnataka, India

Studies on natural radiation levels and radionuclides were carried out extensively in the environment of granite quarries of Kanakapura, Ramanagara Taluks and Bidadi Hobli in Bangalore rural District and Bangalore city. The indoor and outdoor gamma exposure rate in air was measured using an environmental dosemeter, and it is converted into absorbed dose using suitable conversion factor. The activity concentrations of natural radionuclides in rock samples and also in soil samples were measured using an HPGe gamma-ray spectrometer. The results reveal that the activity concentrations of (226)Ra, (232)Th and (40)K in rocks are found to be vary from 32.2 to 163.6, 128.3 to 548.6 and 757.4 to 1418.4 Bq kg(-1), respectively, with corresponding arithmetic mean values of 93.2, 306.2 and 1074.4 Bq kg(-1). Activity concentrations of (226)Ra, (232)Th and (40)K in soil samples were found to vary from 32.4 to 55.2, 39.9 to 214.3 and 485.4 to 1150.2 Bq kg(-1), respectively, with corresponding arithmetic mean values of 40.7, 93.1 and 750.4 Bq kg(-1). The average activity levels of all these radionuclides are above the global average. This is consistent with the geological and geo-chemical significance of the rocks of the area under investigation. The results of these systematic investigations are discussed in detail and compared with the literature values represented for other environments.

Determination of the elemental contents in stream sediments collected from Cheongju city by instrumental neutron activation analysis

Sediment samples were collected from seven locations of the MeeHo stream in Cheongju city, strained out by a sieve, dried by an oven and pulverized by an agate mortar. Instrumental neutron activation analysis (INAA) was applied for the determination of the elemental contents in the sediment samples by using the NAA #1 and #2 irradiation holes of the HANARO research reactor and HPGe gamma-ray spectrometers. Twenty-five elements were determined by a relative method with NIST SRM 2711-Montan Soil and the ranges of the elemental contents for the seven locations were identified. The contamination levels for elements such as As, Ba, Cr, Mn, Fe and Zn were compared with the guidelines of USEPA. The detection limits and combined uncertainties for the hazardous elements such as As, Ba, Cr, Mn, Sb, V and Zn were estimated under the given analytical conditions.

Assessment of natural radioactivity and the associated hazards in Iranian cement

This paper presents the finding of a study undertaken to determine natural radioactivity and associated hazards in local types of cement in Iran. A total of 42 samples were collected from various manufacturers and suppliers and analysed using a shielded HPGe gamma-ray spectrometer. The specific activities of 232Th, 226Ra and 40K were measured in samples and results ranged from minimum values of 8, 16, 101 Bq kg(-1) to maximum values of 17, 43 and 141 Bq kg(-1), respectively. On the basis of activity concentration index (I), it could be shown that, the radioactivity of local cement samples was not greater than the established standard values in other countries.

Determination of the elemental composition of the bottom ash of a municipal incinerator by instrumental neutron activation analysis

To enhance the applicability of the nuclear analytical technique in the field of industry and the environment, the inorganic elemental content of the bottom ash from a municipal solid waste incinerator was determined by instrumental neutron activation analysis. Bottom ash samples were monthly collected from an incinerator located at a metropolitan city in Korea, strained through a 5 mm sieve, dried by an oven and pulverized by an agate mortar. The samples were irradiated at the NAA #1 irradiation hole (thermal neutron flux: 2.92·1013 n·cm−2·s−1) in the HANARO research reactor of the Korea Atomic Energy Research Institute and the irradiated samples were measured by a HP Ge gamma-ray spectrometer. Thirty-three elements including As, Cr, Cu, Fe, Mn, Sb and Zn were analyzed by an absolute method. The quality control was conducted by a simultaneous analysis with NIST standard reference materials. The average concentrations of the major elements such as Ca, Fe, Al, Na, Mg, K and Ti measured in the sample were 19.9%, 4.85%, 3.79%, 2.11%, 1.84%, 1.22% and 1.02%, respectively. In addition, the concentrations of the hazardous metals like Zn, Cu, Cr, Sb and As were 0.77%, 0.31%, 729 mg·kg−1, 116 mg·kg−1 and 22.2 mg·kg−1, respectively.

The natural radioactivity in the bricks used for the construction of the dwelling in Tehran areas of Iran

This paper presents the finding of a study undertaken to determine the natural radioactivity present in bricks in Tehran. A total of 45 samples of commonly used bricks were collected from various manufacturers and suppliers and analyzed using a shielded HPGe gamma ray spectrometer. The specific activities of (226) Ra, (232) Th, and (40) K were measured in all brick samples, and results ranged from minimum values of 26, 24, and 524 Bq kg(-1) to maximum values of 38, 36, and 820 Bq kg(-1) with mean values of 33, 30, and 700 Bq kg(-1) ,respectively. In general, these activities were comparable to the results of similar studies undertaken in another countries. These activities would suggest that the use of such bricks in construction of dwellings or work places in Tehran is unlikely to give rise to any significant radiation exposure to the occupants.

Implementation of the k0-NAA method in the NAA#3 irradiation hole of the HANARO research reactor

The NAA#3 irradiation hole in the 30 MW HANARO research reactor of the Korea Atomic Energy Research Institute (KAERI), with a thermal neutron flux of 1.26×10 14 cm −2 s −1, has been regarded as suitable for the application of k 0-based neutron activation analysis ( k 0-NAA). The objectives of the present work were: (a) to characterize the NAA#3 irradiation hole via the determination of the neutron spectrum parameters required for the method, (b) to calibrate the HPGe gamma-ray spectrometer system via establishing the detection efficiency curves and (c) to assess the quality of the k 0-NAA method by the analysis of six certified reference materials, three of which were of biological nature and three of environmental origin. The results obtained indicated that, by using the k 0-NAA method, approximately 25 or 35 elements could be quantitatively determined in the biological and environmental samples, respectively. The deviations between the experimental and the certified values for the determined elements were generally within 12% with u-scores mostly below 2. The results prove that the k 0-NAA method, implemented in the HANARO research reactor, is applicable for multi-element analysis in biological and environmental samples with a rather high analytical performance and that the method is available for further practical applications.

Computational investigation of on-line interrogation of pebble bed reactor fuel

Pebble bed reactors are characterized by multipass fuel systems in which spherical fuel pebbles are circulated through the core until they reach a proposed burnup limit (80000-100000 MWD/MTU). For such reactors, the fuel is assayed on-line to ensure that the burnup limit is not breached. We considered assaying the fuel using an HPGe detector to perform passive gamma-ray spectrometry of fission products. Since neither fresh nor irradiated fuel is readily available, computer simulations were utilized to identify the radionuclides that can be used as burnup indicators, and to visualize the gamma-ray spectra at various levels of burnup. Specifically, we used the ORIGEN-MONTEBURNS-MCNP code system. This allowed the establishment of the burnup dependent one-group gas reactor cross-sections for the radionuclides of interest. Subsequently, ORIGEN was used to simulate in-core pebble depletion to establish the irradiated pebble isotopics. Finally, the codes MCNP and SYNTH were used to simulate the response of the HPGe gamma-ray spectrometer. The results show that absolute and relative indicators can be used on-line to determine unambiguously the enrichment and burnup on a pebble-by-pebble basis. The activity of Cs-137 or the activity ratio of Co-60/Cs-134 can be combined with the activity ratio of Np-239/I-132 to yield the enrichment and burnup information. To use the relative indicators, a relative efficiency calibration of the gamma-ray spectrometer can be performed using the La-140 gamma lines that are emitted by the irradiated pebble. I-132, Cs-134, Cs-137, La-140, and Np-239 are produced upon the irradiation of the fuel. Co-60 is produced by doping the fuel with a small amount (/spl sim/100 ppm) of Co-59. Using this approach, the uncertainty in burnup determination due to factors such as power history variation, detector efficiency calibration, and counting statistics is expected to remain in the range of /spl plusmn/5% to /spl plusmn/10%.

Radiological significance of Pakistani marble used for construction of dwellings

Natural radioactivity in various types of marbles available in Rawalpindi/Islamabad industrial area have been assessed using HP(Ge) gamma-ray spectrometer. The concentration of 40K, 226Ra and 232Th ranges from 6.15 to 159.65 Bq.kg-1, 1.45 to 29.34 Bq.kg-1 and 1.16 to 6.28 Bq.kg-1, respectively. The radium equivalent activity lies between 5.56 to 33.42 Bq.kg-1. The average external and internal indices have been found to be 0.03 and 0.05, respectively. The average absorbed dose rate at 1 m was found to be 6.53 nGy.h-1. The estimated annual effective dose rate for whole body was found to be 0.04 mSv.y-1. These values are smaller than those predicted by UNSCEAR for normal background areas. The marbles analyzed pose less health hazard as compared to Pakistani baked bricks and other construction materials.

Is loss-free counting under statistical control?

A new formula for the statistical uncertainty of "loss-free counting" (LFC) is presented. Its validity is demonstrated by comparing with experimental data obtained with a HPGe gamma-ray spectrometer. Also, computer simulation data of nuclear counting with different types of count loss (pileup rejection, extending and nonextending dead time) are in agreement with the predicted counting uncertainty. The proposed formula for LFC uncertainty is applicable to spectrometers with a classical semi-Gaussian pulse-shaping amplifier as well as with a gated-integrator amplifier. Hence, achieving statistical control seems to be a feasible goal.

External gamma radiation dose rates in coastal Karnataka

External gamma-ray dose rates in air have been measured using a sensitive plastic scintillometer in the environment of coastal Karnataka, on the south west coast of India, where intensive industrial activities including a nuclear power plant, a super thermal power station and a petrochemical complex are envisaged. The gamma dose rates in air range from 26 to 174 nGy h-1 with a geometric mean of 74 nGy h-1 and geometric standard deviation of 1.4. The activity of primordial radionuclides in soil samples of the region were measured using an HPGe gamma ray spectrometer and the resulting doses in air were calculated. The mean absorbed dose rate due to primordial radionuclides was 41.4 nGy h-1 with a geometric standard deviation of 1.4. A correlation was found between doses measured using scintillometer and doses estimated from the measured activity of primordial radionuclides when the cosmic ray component is taken into account. The concentration of primordial radionuclides in soil and sand show considerable variation in their vertical depth distribution in the high background area of the region.

Measurement of cosmogenic radionuclides in meteorites with a sensitive gamma-ray spectrometer

A large-volume HPGe gamma-ray spectrometer in a NaI(Tl) well has been set up underground at 70 m.w.e. depth for whole body counting of cosmogenic radionuclides in meteorites. The detectors are housed in a 20 cm thick lead shield with a lining of cadmium and OFHC copper. The scintillator is simultaneously operated in anticoincidence as well as in coincidence in selected energy channels to achieve low background levels (in the range of counts per day) and high specificity. In this way a large number of radionuclides such as26Al,44Ti,60Co,22Na,54Mn, and shorter-lived nuclides produced in extraterrestrial materials like meteorites and lunar rocks can be analysed. Results on Bouvante and Bereba achondrites and Dhajala and Torino chondrites are presented.

A determination of the Fano factor for germanium at 77.4 K from measurements of the energy resolution of a 113 cm 3 HPGe gamma-ray spectrometer taken over the energy range from 14 to 6129 keV

The Fano factor for germanium cooled to 77.4 K has been determined from a semiempirical analysis of the measured energy resolution of a HPGe γ-ray spectrometer of active volume 113.2 cm 3. Twenty nine γ-ray energies spanning the range from 14 to 6129 keV were used in this study. The dispersion due to incomplete charge collection was assessed experimentally by making measurements over a wide range of applied bias. Plots of the peak centroid shift and the peak width squared against the reciprocal of the voltage applied to the detector, were non-linear. Both exhibited plateaus for large applied voltages. Thus, by operating in the plateau region, the Fano factor could be extracted from the variation of the observed line width as a function of energy, while the detector was known to be functioning close to the position of perfect charge collection. A number of previous authors have relied on various extrapolations to infinite charge collecting field conditions, and this can result in an estimate of the Fano factor which is too small. It is suggested that this could be the reason why, in broad terms, the existing database supports two values of the Fano factor, one centring about 0.06 and the other about 0.13. The value of the Fano factor obtained in this work, averaged over the energy range 14–6129 keV, was 0.112±0.001. It is recommended that more, high quality, measurements be made.

Data-acquisition system for the [formula omitted] coincidence-counting equipment and the gamm-ray spectrometers at the laboratory of ionizing radiation metrology of ENEA

A data-acquisition system, developed at the Laboratory of Ionizing Radiation Metrology of the Italian Commission for Nuclear and Alternative Energy Sources (ENEA), for automatic computer-controlled acquisition of data from the 4πβ(PC)- ▪ coincidence-counting equipment and four HPGe gamma ray spectrometers, is described. This opportunity is also taken to describe briefly the present status of this system and assiociated equipments as well as actual measurements, including the participation in international comparisons.