Performance testing of the upgraded uranium isotopics multi-group analysis code MGAU

The paper describes recent developments of the MGAU (Multi-Group Analysis for Uranium) method, which resulted in the creation of an upgraded version 4.0 of the MGAU code. The major improvements concerned the procedure of the intrinsic efficiency calibration, particularly in the 120–205 keV region. The results of the tests carried out with the use of certified reference uranium isotopic materials SRM 969 and CRM 146 showed a significantly improved performance of the upgraded MGAU code for the accurate characterization of 235U and 234U abundances. The relative systematic biases of the abundances measured were evaluated not to exceed 1% and 3% over the concentration intervals 0.32–93.2 and 0.002–0.98 mass% for 235U and 234U, respectively. The influence of an up to 4–5 mm steel equivalent absorber and sample thickness on the measurement results was found to be much smaller than in previous versions of the code.