Fission product palladium-silicon carbide interaction in htgr fuel particles

The role of Pd in the transport of Ag in SiC

“…Pd, as discussed previously, is a relatively high yield metallic fission product which has been shown in numerous studies to chemically react and corrode the SiC layer of TRISO particles during reactor operation [17,18] or during the annealing of irradiated particles. The reaction has been found to occur preferentially along grain boundaries.…”

“…It is known that Pd, after birth in the kernel, can migrate rapidly through the porous carbon and PyC layers to the PyC/SiC interface. It then proceeds to infiltrate the SiC along grain boundaries from where it corrodes the SiC by displacing the C leading to the formation a palladium silicide [17,18]. It is proposed that Ag penetrates the SiC along grains boundaries together with the palladium silicide in the form of a Pd-Ag-Si solution.…”

A review of TRISO fuel performance models

“…The interested reader is also directed to the many excellent reviews of TRISO performance results [9,14,19,[25][26][27][28][29][30][31][32][33][34]. To provide context for the review of the FPMs Sections 2 and 3 briefly summarize fuel behavior and failure mechanisms.…”

PARFUME Theory and Model basis Report

“…To date, all available in-reactor data for Pd penetration in SiC 35,36,37,38 have been fitted to an Arrhenius function. The resulting penetration depth correlation will be coupled with finite element stress analyses of corroded, or thinned, SiC to develop a failure algorithm.…”