Electron probe microanalysis of irradiated and 1600°C safety-tested AGR-1 TRISO fuel particles with low and high retained ^110mAg

Advanced Gas Reactor (AGR)-1 fuel Compact 4-3-3 achieved 18.63% FIMA and was exposed to a safety test at 1600°C. Two particles, AGR1-433-003 and AGR1-433-007, with measured-to-calculated ^110mAg inventories of <22% and 100%, respectively, were selected for electron microprobe analysis to determine whether the distribution or abundance of fission products differed proximally and distally from the deformed kernel in AGR1-433-003 and how this compared to fission product distribution in AGR1-433-007. On the deformed side of AGR1-433-003, xenon, cesium, iodine, europium, strontium, and tellurium concentrations in the kernel buffer interface near the protruded kernel were up to six times higher than on the opposite, non-deformed side. At the silicon carbide (SiC)-inner pyrolytic carbon (IPyC) interface proximal to the deformed kernel, palladium and silver concentrations were 1.2 and 0.04 wt% respectively. On the SiC-IPyC interface distal from the kernel deformation, those elements measured 0.4 and 0.01 wt%, respectively. Palladium and silver concentrations at the SiC-IPyC interface of AGR1-433-007 were 2.05 and 0.05 wt.%, respectively. Rare earth element concentrations at the SiC-IPyC interface of AGR1-433-007 were ten times higher than at the SiC-IPyC interfaces measured in AGR1-433-003. Palladium permeated the SiC layer of AGR1-433-007 and the SiC layer of the non-deformed side of AGR1-433-003.