Zsolt Révay: Analysis of U-containing samples by the PGAA method


Promt Gamma Activation Analysis (PGAA) is a recent, versatile method for determination of elemental and isotope compositions. Our facility is operated on one of the neutron beams provided by the Budapest Neutron Centre (BNC). Our previous studies were performed on the thermal neutron beam. Certain characteristic gamma-peaks originated from 235U (and its fission products) and from 238U were identified, their partial effective cross-sections were determined by a relative accuracy of 10 %. A calibration curve was constructed by using the area ratios of the two isotopes in the PGAA spectra. This curve allows the determination of the degree of the enrichment in the 0.1 – 50 % region.

Recently the BNC is furnished with a cold neutron source, providing a mean for more accurate determination of the effective cross-sections. In the case of uranium isotopes the new accuracies attain a few tenth per cent – improving the accuracy of the determination of the U content and enrichment by an order of magnitude. This procedure is based on detection of high-energy gamma rays of negligible absorption. Thus neither the shape, thickness nor even the presence of a container material affects the accurate determination. Hence, the cold PGAA provides a fast, accurate and non-destructive method for determination of contents of uranium isotopes (and the extent of enrichment) even in closed containers.