Cladding embrittlement under LOCA conditions, examined by two test methodologies

Nagase, Fumihisa ; Chuto, Toshinori; Fuketa, Toyoshi

Experiments simulating the whole LOCA sequences are performed in Japan, while ring-compression tests of oxidized cladding are performed for evaluating cladding embrittlement in a LOCA. In order to compare the two test methodologies and discuss about the safety limits appropriate to the high burn-up fuel, the ring compression test at 135C was performed with specimens sampled from the high burn-up fuel cladding which was tested in the LOCA-simulated experiments. Oxidation temperature in the LOCA-simulated experiments ranges about 1130 to 1210C, the oxidation ranges about 11 to 22% ECR and hydrogen concentrations ranges about 200 to 1400 ppm. Although the examined high burn-up cladding did not fracture on the quenching in the LOCA-simulated experiments, the specimens fractured without showing plastic deformation in the ring compression tests. Considering the severity to the fuel, up to the quench phase, the ring compression test could provide conservative results.