235U isotopic characterization of natural and enriched uranium materials by using multigroup analysis (MGA) method at a defined geometry using different absorbers and collimators

Characterization of nuclear materials is an important topic within the context of nuclear safeguards, homeland security and nuclear forensics. This paper deals with the performance of multigroup gamma-ray analysis (MGA) method using the X- and γ-rays in the 80–130 keV region and enrichment meter principle (EMP) based on the analysis of 185.7 keV peak for a certain geometry using different absorbers and collimators. The results from MGA and those of EMP are compared. In particular, the effect of aluminum/lead absorbers and lead collimator on the enrichment determination of 235U in natural and low enriched samples is investigated in a given source- -detector geometry. The optimum diameter/height ratio for the Pb-collimator is found to be Dc/Hc = 1.4–1.6 in the chosen geometry. In order to simulate the container walls, ten different thicknesses of Al-absorbers of 141 to 840 mg·cm–2 and six different thicknesses of Pb-absorbers of 1120–7367 mg·cm–2 are interposed between sample and detector. The calibration coefficients (% enrichment/cps) are calculated for each geometry. The comparison of the MGA and EMP methods shows that the enrichment meter principle provides more accurate and precise results for 235U abundance than those of MGA method at the chosen geometrical conditions. The present results suggest that a two-step procedure should be used in analyses of uranium enrichment. Firstly MGA method can be applied in situ and then EMP method can be used at a defined geometry in laboratory

Quantification of uranium-238 in environmental samples using gamma-ray spectrometry

A large number of environmental samples are routinely measured world-wide using gamma-ray spectrometry some of its assets being easy sample preparation and comprehensive data for many radionu-clides in one analysis. Although other techniques can be considered more suitable for analysing 238U in environmental samples, it is also routinely done by gamma-ray spectrometry. One mainly uses γ-ray emissions following the decay of the first daughter, 234Th, for determining the 238U activity. However, the low-energy gamma-rays at 63 keV and 92.5 keV are very difficult to quantify in a robust way due to high attenuation and interferences. This paper quantifies parameters affecting the possibility of making robust quantification of 238U via 234Th using gamma-ray spectrometry. It addresses the use of correct decay data, suitable detectors, optimised sample size, enhanced spectral amplification, correction for peak interferences and control of background

Quantification of uranium-238 in environmental samples using gamma-ray spectrometry

A large number of environmental samples are routinely measured world-wide using gamma-ray spectrometry some of its assets being easy sample preparation and comprehensive data for many radionu-clides in one analysis. Although other techniques can be considered more suitable for analysing 238U in environmental samples, it is also routinely done by gamma-ray spectrometry. One mainly uses γ-ray emissions following the decay of the first daughter, 234Th, for determining the 238U activity. However, the low-energy gamma-rays at 63 keV and 92.5 keV are very difficult to quantify in a robust way due to high attenuation and interferences. This paper quantifies parameters affecting the possibility of making robust quantification of 238U via 234Th using gamma-ray spectrometry. It addresses the use of correct decay data, suitable detectors, optimised sample size, enhanced spectral amplification, correction for peak interferences and control of background

Results of an international comparison of activity measurements of 68 Ge

Proceedings of the 21st International Conference on Radionuclide Metrology and its Applications (ICRM), May 15-19, 2017, Buenos Aires, Argentina. Organizer: Argentinian National Atomic Energy CommissionInternational audienceAn international key comparison, identifier CCRI(II)-K2.Ge-68, has been performed. The National Institute of Standards and Technology (NIST) served as the pilot laboratory, distributing aliquots of a 68Ge/68Ga solution. Results for the activity concentration, CA, of 68Ge at a reference date of 12h00 UTC 14 November 2014 were submitted by 17 laboratories, encompassing many variants of coincidence methods and liquid-scintillation counting methods. The first use of 4π(Cherenkov)β-γ coincidence and anticoincidence methods in an international comparison is reported. One participant reported results by secondary methods only. Two results, both utilizing pure liquid-scintillation methods, were identified as outliers. Evaluation using the Power-Moderated Mean method results in a proposed Comparison Reference Value (CRV) of 621.7(11) kBq g−1, based on 14 results. The degrees of equivalence and their associated uncertainties are evaluated for each participant. Several participants submitted 3.6 mL ampoules to the BIPM to link the comparison to the International Reference System (SIR) which may lead to the evaluation of a Key Comparison Reference Value and associated degrees of equivalence