Low-background Gamma-ray Spectrometer Research Articles

Determination of natural radionuclides in phosphogypsum samples from phosphoric acid production industry in Senegal

In this study, the activity concentration of natural radionuclides (238U, 226Ra, 210Pb, 232Th, and 40K) in phosphogypsum were measured using a low-background digital gamma-ray spectrometer equipped with Broad Energy Germanium (BEGe) detector. The mean activity concentrations of 238U, 226Ra, 210Pb, and 232Th were found to be 88.5 ± 19.5 Bq kg−1, 879.6 ± 20.3 Bq kg−1, 755.4 ± 17.1 Bq kg−1, 4.5 ± 0.3 Bq kg−1, and below the detection limit respectively. The estimated radium equivalent activity was found to be higher than the world recommended value of 370 Bq kg−1 but is within the recommended limit of 2220 Bq kg−1 for the use of phosphogypsum in the construction of roads, bridges, and foundations of non-residential buildings. The total annual effective doses received by workers and members of the public were found to be lower than the annual limit of 1 mSv y−1, except for the scenario of a person living in a house built with building material containing phosphogypsum.

Study of cosmogenic activation in copper for rare event search experiments

Rare event search experiments using germanium detectors are performed in underground laboratories to minimize the background induced by cosmic rays. However, the cosmogenic activation of cupreous detector components on the ground generates long half-life radioisotopes and contributes to the background level. We measured cosmogenic activation with 142.50 kg of copper bricks after 504 days of exposure at an altitude of 2469.4 m outside the China Jinping Underground Laboratory (CJPL). The specific activities of the cosmogenic nuclides produced in the copper bricks were measured using a low-background germanium gamma-ray spectrometer at CJPL. The production rates at sea level, in units of nuclei/kg/day, were {18.6 pm 2.0} for {^{54}}Mn, {9.9 pm 1.3} for {^{56}}Co, {48.3 pm 5.5} for {^{57}}Co, {51.8 pm 2.5} for {^{58}}Co, and {39.7 pm 5.7} for {^{60}}Co. The measurement will help to constrain cosmogenic background estimation for rare event searches using copper as a detector structure and shielding material. Based on the measured production rates, the impact of the cosmogenic background in cupreous components of germanium detectors on the next generation CDEX-100 experiment was assessed with the expected exposure history above ground.

A low background gamma-ray spectrometer with a large well HPGe detector

A low background gamma-ray spectrometer was established in a ground-based laboratory. It consists of a large well (diameter: 28 mm, depth: 40 mm) HPGe detector and an anti-cosmic shielding system. The photon background of the present system was measured with and without the anti-cosmic mode, and compared with each other, and the detection capability with the detection efficiency calibration was estimated. The background with passive and active shields for the energy region between 40 keV and 3000 keV was reduced by 78% compared to one with just passive shield. The full energy peak efficiency for cylindrical samples with three different heights and the minimum detectable activity of the present system were tabulated for main radionuclides to be measured in environmental monitoring.

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.

Study on the large area MCP-PMT glass radioactivity reduction

The Jiangmen Underground Neutrino Observatory (JUNO) will install approximately 18,000 20-inch Photomultiplier Tubes (PMTs) in the central detector. From the full detector Monte Carlo (MC) simulation, the PMT glass has one of the largest contribution to the natural radioactive background due to its large mass. Various techniques have been developed to reduce radioactivities introduced in the raw material and during the production process. Efforts such as low background raw material selection, dust and dirty water isolation and continuous production monitoring were taken to reduce the glass background. The radioactivity in the glass sample was measured using a low background gamma ray spectrometer equipped with a high-purity germanium (HPGe) detector. The average level of 238U, 232Th and 40K in total MCP-PMT glass now reach 2.5 Bq/kg for 238U, 0.5 Bq/kg for 232Th and 0.5 Bq/kg for 40K, at least a factor of 2.5 lower than other type of 20-inch PMTs.

Comparison of beta (LSC) and gamma (HPGe) spectrometric methods for lead-210 in chronological study

AbstractThe sediments of two lakes located in the Baltic Uplands, the western part of the East European Plain (East Lithuania and North East Poland), were studied. Activity concentration of210Pb was determined using two nuclear analytical techniques: determination of210Pb in equilibrium with its beta emitting daughter210Bi using liquid scintillation counter (LSC), and direct determination of210Pb (and other radionuclides) by low-background gamma-ray spectrometer with a well type HPGe detector. For the210Pb determination by LSC the methodology of lead separation based on the anion exchange resin in Cl–form (Eichrom) was used. Several steps of radiochemical procedures and respective parameters were investigated additionally. The optimized procedures for LSC method were used for case study with two lake cores. The activity concentration of210Pb in lake sediment samples based on both nuclear analytical techniques (LSC and HPGe) were compared.210Pb dating of cores was performed according to Constant Rate of210Pb Supply (CRS) model with some modifications. Both techniques in the range of uncertainties gave similar results. From two considered lakes, the more eutrophic one exhibited higher sediment mass accumulation rate (MAR) values.

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.

Low-background gamma-ray spectrometry for the international monitoring system

PNNL has developed two low-background gamma-ray spectrometers in a new shallow underground laboratory, thereby significantly improving its ability to detect low levels of gamma-ray emitting fission or activation products in airborne particulate in samples from the IMS (International Monitoring System). The combination of cosmic veto panels, dry nitrogen gas to reduce radon and low background shielding results in a reduction of the background count rate by about a factor of 100 compared to detectors operating above ground at our laboratory.

A second-generation low-background gamma-ray spectrometer

For the ultimate sensitivity in trace radiochemical analysis, the radiation detector must have high efficiency and low background. A low-background gamma-ray spectrometer in regular use at NIST for over twenty years is being supplemented by a new system, improved in several ways. The new detector is much larger, a shield of iron reduces cosmic neutron background compared with lead, large plastic scintillators reduce the muon continuum background, and a digital data acquisition system gives new opportunities for optimization.

A shallow underground laboratory for low-background radiation measurements and materials development

Pacific Northwest National Laboratory recently commissioned a new shallow underground laboratory, located at a depth of approximately 30 meters-water-equivalent. This new addition to the small class of radiation measurement laboratories located at modest underground depths houses the latest generation of custom-made, high-efficiency, low-background gamma-ray spectrometers and gas proportional counters. This paper describes the unique capabilities present in the shallow underground laboratory; these include large-scale ultra-pure materials production and a suite of radiation detection systems. Reported data characterize the degree of background reduction achieved through a combination of underground location, graded shielding, and rejection of cosmic-ray events. We conclude by presenting measurement targets and future opportunities.

Activity determination and nuclear decay data of 113mCd

The radionuclide (113m)Cd was extracted from a Cd component, which has been irradiated in a research reactor during its routine operation. A validated separation procedure was then used to obtain a (113m)Cd solution of high radiochemical purity. The solution was measured by means of liquid scintillation counting for activity determination. To this end, the CIEMAT/NIST efficiency tracing method as well as the triple-to-double coincidence (TDCR) counting technique were used. Measurements in a low-background gamma-ray spectrometer were applied to identify any potential photon-emitting impurities and to measure the 263.7 keV photons from the isomer transition. A gamma emission probability of 0.01839(29)% was determined for this line. The liquid scintillation measurements were also used to evaluate the half-life of (113m)Cd. The decay was followed for about 11 months and a half-life T(1/2)=13.97(13) years was obtained.

Radioactivity and elemental analysis in the Ruseifa municipal landfill, Jordan

In this study, a low background gamma-ray spectrometer based on a Hyper Pure Germanium detector was used to determine the activity concentrations of natural radionuclides in soil samples from various locations within the Ruseifa municipal landfill in Jordan. The chemical composition of the samples was also determined using a Wavelength Dispersive X-Ray Fluorescence Spectrometer. The maximum and minimum annual outdoor effective doses were found to be 103 and 36 μSv a −1 in the old landfill and Abu-Sayaah village, respectively. The annual outdoor effective dose at the recent landfill site was found to be 91 μSv a −1. The annual effective dose equivalents from outdoor terrestrial gamma radiation at the old landfill and the recent landfill were higher than the typical worldwide value of 70 μSv a −1. Thus, some remediation of the soils on both old and recent landfills should be considered before any development for public activities. This could be achieved by mixing with clean soil from areas which are known to have lower radiation background. The concentration of heavy metals Zn, Cr, and Ba in the three sites included in this study were found to be higher than the background levels in the soil samples of the control area (Abu-Sayaah village). The enrichment factors for the above three elements were calculated and found to be: complex building site: Zn = 2.52 and Ba = 1.33; old landfill site: Cr = 1.88, Zn = 3.64, and Ba = 1.26; and recent landfill site: Cr = 1.57, Zn = 2.19, and Ba = 1.28. There was a strong negative correlation between the concentrations of the metallic elements (Mg, Al, Mn, Fe and Rb) and the concentrations of Zn, Ba, and Cr. Moreover, a strong positive correlation was found between Zn, Ba, and Cr. Thus these elements were enriched in the solid waste.

Gamma-ray analysis of the sediments overlying the Helez and Kochav oil fields, Israel

A very sensitive, low-background gamma-ray spectrometer was used to show that a negative total gamma-ray intensity anomaly over the Helez and Kochav oil fields is due to the depletion in all three radionuclides ( 40K, 232Th, and 238U). The location of the radiometric anomalies at the surface above petroleum reservoirs at depth, suggests a genetic connection. It is proposed that the soil radioactivity is not the result of vertical radionuclide transport from the reservoir, rather that migrating hydrocarbons interact and degrade clays and other soil minerals which then release these large cations that substitute for each other diadochously.

Low-background shielding of Ge detectors for the measurement of residual 152Eu radioactivity induced by neutrons from the Hiroshima atomic bomb

Low-background gamma-ray spectrometers were constructed for the measurement of residual 152 Eu activity induced by the atomic-bomb neutrons. Optimum thickness of lead shielding, inner linings and background characteristics were investigated for an ordinary coaxial- and a well-type Ge detector. In addition, an anticoincidence shielding was installed for the well-type detector. As a result, the background counting rate due to cosmic rays was greatly reduced. It was also shown that a sample preparation to enrich the objective activity and eliminate background activities was important in the case of the 152 Eu measurement.

Observation of fallout in Hiroshima caused by the reactor accident at Chernobyl.

Fallout from the reactor accident at Chernobyl has been surveyed at Hiroshima. gamma-rays from samples of aerosol, rain water and tap water were measured using low-background gamma-ray spectrometers and concentrations of activities were followed. Almost all of the nuclides detected in Europe were observed in Hiroshima. In addition to dominant volatile fission products of 131I, 132Te-132I and 103Ru, long-lived fission products 137Cs, 106Ru-106Rh, 125Sb and activities produced through the (n, gamma) process in the reactor such as 134Cs, 136Cs and 110mAg were observed in relatively high concentrations.

An ultralow background germanium gamma-ray spectrometer

An ultralow background 135 cm 3 intrinsic Ge detector has been developed providing a new benchmark in low background gamma-ray spectroscopy. The radioactive background from construction materials has been reduced by more than two orders of magnitude over conventional low background gamma-ray spectrometers. The sources of background in standard commercial cryostats have been identified and eliminated. Data taken with this prototype after elimination of most cosmic ray induced background are presented. The first application of the prototype as well as a large, second generation, multicrystal (∼ 1440 cm 3) germanium detector will be an ultrasensitive search for neutrinoless and two-neutrino double beta decay of 76Ge.

Non-destructive determination of radionuclides in lunar samples using a large low-background gamma-ray spectrometer and a novel application of least-squares fitting

Dual-parameter γ-ray spectrometer systems with large-volume NaI(Tl) crystals and ultra-low backgrounds have been used for the non-destructive determination of K, Th, U, and cosmic-ray produced radionuclides in 60 lunar samples. The total mass of samples measured with these systems is ∼28 kg, and the individual sample masses varied from 2 to 2300 g. Samples from Apollo 11, 12, 14, 15, and 16 missions have been measured. Operation of the spectrometers in a coincidence mode and analyzing singles- and coincidence-spectra permits the simultaneous determination of 8–10 radionuclides in each lunar sample.

The Hanford whole-body counter program.

The Hanford whole-body counter is a low-background gamma-ray spectrometer operated by the Hanford Laboratories. The shielded counting chamber approximates a 3-meter cube with shielding walls consisting of 10-inch thick steel plates. The gamma-ray detector is a large thallium-activated sodium-iodide crystal, 9 3/8 inches in diameter and 4 1/2 inches thick, viewed by four selected photomultiplier tubes of three-inch diameter. The assembly provides 8.3 per cent resolution of the 0.66 Mev gamma rays of cesium 137. The signals from the detector are transmitted to a multichannel pulse height analyzer provided with accessory electronic systems for data presentation and processing. The data accumulated in the pulse height analyzer memory are available as a visual presentation on an oscilloscope, a digital print-out of the counts per channel, a penned plot on Cartesian co-ordinates, and a punched paper tape prepared for electronic data processing. The radionuclides principally found in individuals examined in the ...