A pulse-irradiation test CN-1 on a high-burnupMOX fuel with M5TM cladding was conducted at theNuclear Safety Research Reactor (NSRR) of JapanAtomic Energy Agency (JAEA). Although the transientsignals obtained during the pulse-irradiation test did notshow any signs of the occurrence of PCMI failure, thefailure of the test fuel rod was confirmed from the visualinspection carried out after test CN-1. Analyses using fuelperformance codes FEMAXI-8 and RANNS were alsoperformed in order to investigate the fuel behavior duringnormal operation and pulse-irradiation regarding the testfuel rod of CN-1, and the results were consistent with thisobservation result. These experimental and calculationresults suggested that the failure of test fuel rod of CN-1was not caused by hydride-assisted PCMI but hightemperaturerupture following the increase in rod internalpressure. The occurrence of this failure mode might berelated to the ductility remained in the M5TM claddingowing to its low content of the hydrogen absorbed duringnormal operation.
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