Failure and its mechanism of LWR and research reactor fuels

Yanagisawa, Kazuaki

Proceedings of 3rd International Symposium on Symbiotic Nuclear Power Systems for 21st Century (ISSNP 2010) (CD-ROM), 10 Pages, 2010/08

A LWR fuel consisted of UO pellet with zircaloy cladding and a research reactor fuel consisted of UAlx or USi fuel cores with Al Mg alloy. (1) LWR fuels were irradiated at the HBWR up to burnup of 20 MWd/kgU and power ramped to have the PCI failure. The failure threshold of LWR was lower than that of HBWR. The incore data was used for obtaining the hoop stress and FGR run by the computer code FEMAXI. (2) Fresh or preirradiated LWR fuels were pulse irradiated at the NSRR. For the fresh fuel, a failure occurred at 260 cal/g fuel with cladding melt brittle mechanism. For the preirradiated PWR fuel, a cladding split along one generatrix occurred at 118 cal/g fuel. The failure mechanism is the strong PCMI combined with the transient FGR. (3) Research reactor fuels failed by the through plate cracking or cladding melt. A failure mechanism for the former was a tensile stress caused by a local uneven temperature profile during a quench.