Γ-spectrometry Measurement Research Articles

Stellar s-process neutron capture cross sections on ASe and ACe

We report on experiments at the Soreq Applied Research Accelerator Facility Liquid-Lithium Target (SARAF-LiLiT) laboratory dedicated to the study of s-process neutron capture reactions. The kW-power proton beam at 1.92 MeV (1-2 mA) from SARAF Phase I yields high-intensity 30 keV quasi-Maxwellian neutrons (3-5 1010 n/s). The high neutron intensity enables Maxwellian averaged cross sections (MACS) measurements of samples with short-lived decay products. Neutron capture reactions on natSe and natCe were investigated by activation in the LiLiT neutron beam and γ-spectrometry measurements of their decay products.

Bayesian spatial modelling of terrestrial radiation in Switzerland

The geographic variation of terrestrial radiation can be exploited in epidemiological studies of the health effects of protracted low-dose exposure. Various methods have been applied to derive maps of this variation. We aimed to construct a map of terrestrial radiation for Switzerland. We used airborne γ-spectrometry measurements to model the ambient dose rates from terrestrial radiation through a Bayesian mixed-effects model and conducted inference using Integrated Nested Laplace Approximation (INLA). We predicted higher levels of ambient dose rates in the alpine regions and Ticino compared with the western and northern parts of Switzerland. We provide a map that can be used for exposure assessment in epidemiological studies and as a baseline map for assessing potential contamination.

Optimization of γ-Spectrometry Measurements of Radionuclides of Natural Thorium-232 and Uranium-238 Series

The nuclear-physical properties of radionuclides of natural 232Th and 238U series differ significantly; therefore, the problem of selecting particular γ-lines for calculations arises in direct γ-spectrometry measurements in assessing the absolute activities of the parent radionuclides of these series. In the present study, we develop an approach yielding a reliable value of the specific activity of 232Th and 238U by a single measurement of a sample with the smallest deviation from the true value. We used a bottom sediment sample, taken during the 66th cruise of the Akademik Mstislav Keldysh research vessel in the Kara Sea (station coordinates: 72°30.4' N, 80°20.4' E; depth 14 m), as a model sample. When processing the results, only those lines were selected from the entire set of lines belonging to the 232Th natural series, the quantum yield of which exceeded 2% (taking into account branching). When analyzing the natural 238U series, we selected lines that were free from interference with nuclides of the 232Th series and with the quantum yield above 3%.

Activation experiment at the H4IRRAD facility: A comparison between experimental data, FLUKA and ActiWiz predictions after 15 days of cooling time

An experiment was carried out in June 2011 at the H4IRRAD facility, which allows to reproduce the radiation fields commonly encountered in the CERN Large Hadron Collider. The purpose of this study was to create a set of experimental activation data that can be used to benchmark Monte Carlo codes and now the analytical ActiWiz software package, both extensively used by CERN’s Radiation Protection Group. The choice of actual specimens that have been used for the construction of the Large Hadron Collider (LHC) and the LHC experiments has been made specifically in view of future upgrades or dismantling of CERN’s accelerators and experimental areas. Six samples of materials commonly used at CERN were irradiated by the secondary particles generated from the impact of a 280 GeV/c hadron beam on a 100 cm long copper target with the samples having been placed few centimetres below. This paper discusses first the experimental results obtained by γ-spectrometry measurements after 15 days of cooling time. Then, it discusses the FLUKA simulations performed in order to obtain the radionuclide inventories as well as the mixed particle fluence spectra in the samples. Third, it discusses the predictions by the ActiWiz software and compares them with the FLUKA results for the sake of a code comparison. Finally, the experimental and computational results are compared and discussed altogether.

New production cross sections for the theranostic radionuclide 67Cu

Abstract The cross sections of the 68Zn(p,2p)67Cu, 68Zn(p,2n)67Ga and 68Zn(p,3n)66Ga reactions were measured at the ARRONAX facility by using the 70 MeV cyclotron, with particular attention to the production of the theranostic radionuclide 67Cu. Enriched 68Zn material was electroplated on silver backing and exposed to a low-intensity proton beam by using the stacked-foils target method. Since 67Cu and 67Ga radionuclides have similar half-lives and same γ-lines (they both decay to 67Zn), a radiochemical process aimed at Cu/Ga separation was mandatory to avoid interferences in γ-spectrometry measurements. A simple chemical procedure having a high separation efficiency (>99%) was developed and monitored during each foil processing, thanks to the tracer isotopes 61Cu and 66Ga. Nuclear cross sections were measured in the energy range 35–70 MeV by using reference reactions recommended by the International Atomic Energy Agency (IAEA) to monitor beam flux. In comparison with literature data a general good agreement on the trend of the nuclear reactions was noted, especially with latest measurements, but slightly lower values were obtained in case of 67Cu. Experimental results of the 68Zn(p,2p)67Cu, 68Zn(p,2n)67Ga and 68Zn(p,3n)66Ga reactions were also compared with the theoretical values estimated by using the software TALYS. The production yield of the theranostic radionuclide 67Cu was estimated considering the results obtained in this work.

Estimation of coastal residence time of submarine groundwater discharge using radium progenies

A methodology based on γ-spectrometry measurements of untreated coastal water samples is proposed for the direct estimation of coastal residence time of submarine discharged groundwater. The method was applied to a submarine spring at Stoupa Bay covering all seasons. The estimated residence time exhibited an annual mean of 4.6±1.7 d. An additional measurement using the in situ underwater γ-spectrometry technique was performed, in the same site. The in situ method yielded a value of 2.8±0.2 d that was found consistent with the corresponding value derived using the developed lab-based method (3.4±2.0 d) for the same period.

Intercomparison of γ-spectrometry analysis of radionuclides between China and Japan in 2012–2013

An intercomparison of γ-spectrometry measurement and analysis was organized by the Japan Chemical Analysis Center (JCAC), the National Institute for Radiological Protection, Chinese Center for Disease Control and Prevention (NIRP, China CDC), and the Radiation Monitoring Technical Center of Ministry of Environmental Protection, Chinese (RMTC). The main objective of this study was to assess the γ-spectrometry measurement and analysis technology. The JCAC completed the collection and preparation of soil and powdered rice samples. Three laboratories compared the measurement of seven radionuclides that included two samples of 214Pb, 214Bi, 208Tl, 228Ac, 40K, 137Cs, and 134Cs with γ-spectrometry. During the studies conducted at the laboratory, the calculated value En was found to be the total uncertainty data of the reported activity. Except 134Cs in powdered rice sample, the calculated En between each of the two laboratories was <1. The measurement results are acceptable except 134Cs; therefore, measurement results in the three laboratories were consistent within a certain range except in the case of 134Cs. Although there is a need to improve the accuracy of measurements and analysis of 134Cs, an intercomparison was conducted of the tested levels on radionuclide analyzed in the three laboratories.

The gabbro and serpentinized peridotite of Bonassola (Bracco-Levanto ophiolite, Italy) – An extremely low natural radiation area to improve in situ gamma spectrometry

Outcrops of dunite, serpentinized peridotite and clinopyroxene-rich coarse gabbro around Bonassola (Bracco-Levanto ophiolite, NW Italy) have been analyzed for natural radionuclides using γ-spectrometry. The very low activity concentrations of natural radionuclides in the dunite outcrop (< 9.0 Bq kg -1 226 Ra; < 3.5 Bq kg -1 228 Ac and < 25 Bq kg -1 40 K) indicate that this site is characterised by a very low natural radiation for both cosmic (being at sea level) and terrestrial contributions. Before starting a field radiometric survey it is important to assess the local background, i.e. the g radiation that does not originate from rock, in order to correct the measurements for the local background. Contrary to the general practice regarding the background radiation in γ-spectrometry measurements, the investigated mafic-ultramafic outcrops has been used to estimate the detection limits for in situ measurement of 238 U, 232 Th and 40 K using sodium iodine (NaI) scintillator detectors. These results have proved useful to quantify the minimum detectable amount of activity (MDA) of 238 U, 232 Th and 40 K for the NaI detector; the MDA points at sub ppm levels for 238 U and 232 Th and 0.01 wt% K 2 O. This study also permits to assess the radiological risk of dimension stones that are petrographically similar to the serpentinized ultramafics occurring in the Bracco-Levanto ofiolite. The comparison of the activity concentration index I, defined by the EU Basic Safety Standards Directive and depending on the activity concentrations of 226 Ra, 232 Th and 40 K, with other stones used as building material, indicates that the Bonassola mafic-ultramafic rocks provide a negligible contribution to the indoor gamma radiation dose.

Standardisation of 223Ra by liquid scintillation counting techniques and comparison with secondary measurements

An aqueous solution of 223Ra chloride in equilibrium with its decay progeny was standardised by liquid scintillation counting techniques. Since secular equilibrium with the decay progeny of 223Ra had been established by the time of measurement, the apparent detection efficiency of 223Ra was approximately 6 and was determined by both the CIEMAT/NIST efficiency tracing technique and the 4π(LS)-γ digital coincidence counting techniques. The results obtained were compared with γ-spectrometry and ionisation chamber measurements. Whilst the γ-spectrometry measurements were in agreement (albeit exhibiting a large spread (18%) in the individual activity estimations using the main γ-emissions), a significant discrepancy of the order of 9% was identified between the liquid scintillation counting results and those obtained using published calibration factors for a variety of radionuclide calibrators.

Comprehensive software for the assessment of 222Rn and 220Rn decay products based on air sampling measurements

A computational tool dedicated to the measurement of 222Rn and 220Rn decay products by air sampling is presented. α- or γ-spectrometry measurements, gross α or β counting, as well as a combination of them are considered. Special attention is given to the evaluation of the uncertainty budget of the results. Besides typical applications in the analysis of experimental data, the software can be used for assessing the expected quality of a measurement protocol and for optimizing it, by generating and analyzing sets of realistic synthetic data.

Evaluation of technologically enhanced natural radiation near the coal-fired power plants in the Lodz region of Poland

Radionuclide releases together with escaping fly ashes (from 45×10 6 kg in previous decades to 8×10 6 kg annually in 1996) from the main local and several small coal-fired power plants resulted in a relatively small increase in natural radioactivity levels in the Lodz region. The natural gamma terrestrial radiation dose rates (1 m above ground level) were measured at 82 points including in the vicinity of power plants, in the center of the town and on edge of the town. The average dose rate value for the first area was 36±1.2 nGy h −1, whereas the same dose rate for the edge of town was slightly lower 30±0.9 nGy h −1, but this difference was statistically significant. Further confirmation of the technologically slightly enhanced exposure of the local population to natural radionuclides was achieved by γ-spectrometry measurement of the uranium and thorium decay series radionuclides in the surface soil profiles (up to 30 cm depth). The average increase of 226Ra and 232Th radionuclides in the top layer of soil (0–10 cm) according to the 20±30 cm depth layer was 21% and 17%, respectively. However, due to the relatively low levels of 232Th (14.3 Bq kg −1) and 238U (16.8 Bq kg −1) in this area, the annual average effective dose from the natural terrestrial radiation for the local population is also relatively low, 0.28 mSv only.

Accurate calculation of total efficiency of Ge well-type detectors suitable for efficiency calibration using common standard sources

A new method for the calculation of coincidence summing out corrections appropriate for γ-spectrometry measurements in the Ge well-type detector geometry is proposed. The method is based on a simple formula for the total efficiency of the detector, using an exact analytical relation for the mean detector thickness, combined with approximate formulas describing the interactions in the source and in the materials interposed between the source and the detector. The method can be easily applied for establishing the corrected, nuclide independent, efficiency calibration curves of Ge well-type detectors using experimental calibration data obtained with the common mixed γ-ray standard source containing 60Co and 88Y.

Determination of caesium and its isotopic composition in nuclear samples using isotope dilution-ion chromatography-inductively coupled plasma mass spectrometry

J. Maria Barrero Moreno, M. Betti and G. Nicolaou, J. Anal. At. Spectrom., 1999, 14, 875 DOI: 10.1039/A806467I

Natural radiactivity of fresh waters in Serbia

Statistical tests were performed on the γ-spectrometry measurement data obtained during the last decade for the natural radionuclides40K,226Ra and232Th, in water samples collected from the Danube River, the Sava River and its tributaries, ground waters and artificial lakes. The lognormal radiopotassium distribution indicates a single statistical population. The presence of break points in the frequency distribution plots indicates that data for226Ra and232Th do not come from a single statistical population. The annual iongestion of40K,226Ra and232Th was calculated and expressed in Bq y−1.

Determination of trace elements in iron by neutron-activation techniques

A systematic analytical procedure for the determination of some trace impurities in iron matrices was developed by employing both direct and destructive neutron-activation techniques. Irradiations in fast neutron fluxes, selective activation by epithermal neutrons and coincidence γ-spectrometry measurements were used in some cases, in order to improve the sensitivity for non-destructive analysis; for destructive methods, radiochemical separations based on ion exchange and solvent extraction were applied. Procedures are described, and some results of the determination of low concentrations of Al, Mn, Ti, V (non-destructive), P, S, Zn (destructive) and As, Co, Cr, Cu, Mo, Ni, Sc, W (both methods) in iron are reported and discussed.