Faire avancer la sûreté nucléaire

La Recherchev2


Implementation of an experimental design to evaluate the codes used to determine the enrichment of uranium samples



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Titre du congrès :29th ESARDA ANNUAL MEETING Ville du congrès :AIX-EN-PROVENCE Date du congrès :22/05/2007


Gamma spectroscopy is commonly used in nuclear safeguards to measure the enrichment of uranium applying either the enrichment meter method, or analysis codes developed to analyse several  g-rays or X- and  g-rays in defined regions of a uranium spectrum. An experimental design has been carried out for the measurement of uranium enrichment using this technique with different software used in safeguards applications: MGA, MGA++, PCFRAM and IGA. The main goal is to estimate correctly the uncertainties of the measurement taking into account realistic in situ acquisition condition. To set up the experiment, uranium sources have been achieved. It is U308 reference material in powder form, with a wide enrichment range in sealed container. Regarding the acquisition systems, several gamma spectroscopic germanium detector (planar, coaxial) and multichannel analysers have been used. Five entry parameters have been considered for the experimental design: 235U enrichment, adjustment of the acquisition gain, source-detector distance, shielding, and matrix effect. With all this spectra, there is a direct comparison between the uncertainty announced by the different software and the difference between the computed enrichment value and the value of the reference material. The paper describes the methodology implemented to evaluate the results of such an experimental design, and exhibits the results obtained when applying the code MGAU, with the objective to confirm or to improve our current knowledge of uncertainties for these uranium enrichment measurements. The evaluation of the 3 other codes, which is currently in progress, will be subsequently published.