Comments on the threshold porosity for fission gas release in high burn-up fuels

This letter challenges two recent papers in this journal, suggesting that the high burn-up structure of LWR-fuels would evolve towards an open pore system, facilitating gas release. In contrast, recent experimental results and supporting calculations reviewed here as well as new evidence from a 3D pore-reconstruction strongly suggest that the materials in question would show closed porosity conditions and hence reduced probability of gas release, at least up to porosity fractions of about 25%. This value is most likely conservative.