Fission product distribution in irradiated safety-tested and non-safety-tested AGR-2 TRISO particles

Abstract

Two similarly-irradiated TRISO nuclear fuel particles, one safety-tested and one not-safety-tested, were examined by electron probe microanalysis (EPMA) as part of the advanced gas reactor (AGR) fuel development and qualification programme. The primary objective of this study was to determine the effect of high temperature safety testing on the fission product quantification and distribution. Concentration profiles for fission products were collected along two radii in each particle. Fission product mass balance distribution for both particles was determined by computing the material mass per traverse step-size and multiplying by the weight fraction analysis at that position. Results of these analyses suggest that the non-safety-tested particle contains more fission product mass in the centre 300 µm of the kernel than the safety-tested particle; however, for mobile fission products such as Cs, Xe, Te, Sr, Ba, and Pd, the mass moves out further from the particle centre in the safety-tested particle than the non-safety-tested particle. This mass balance approach to TRISO particle analysis is beneficial at elucidating fission product migration in irradiated and safety-tested particles and will be beneficial in applying to other particles to determine potential irradiation damage effects on the fission product distribution and mobility.