Verification test on high burnup fuel

A step wise burnup extension programme has been progressing by utilities and vendors in Japan. Objective of burnup extension is to reduce the LWR fuel cycle cost and the amount of spent fuel assemblies. The present maximum burnup limit approved for PWR fuel assemblies is 48 GWd/t, and irradiation testing on a limited number of fuel assemblies with extended burnup of up to 55 GWd/t was licensed last year. These fuel assemblies are now under the irradiation. In order to develop advanced design (high burnup) LWR fuel, there are several important technical matter to be resolved. These are the change of characteristics of UO2 pellets under high burnup irradiation such as swelling, fission gas release and formation of RIM, and corrosion of cladding tube. The interaction between pellet and cladding, PCI, is also given attention. Under the sponsorship of Ministry of International Trade and Industry (MITI), NUPEC has been carrying out irradiation test programs for Japanese LWR fuels to verify their satisfactory performance. In order to obtain systematic and high quality data, well pre-characterized fuel assemblies are monitored during irradiation and are subjected to detailed post irradiation examinations (PIEs) in a hot laboratory. As one of these programs is 'The verification test programme on PWR high burnup fuel.' 5 refs., 1 tab., 9 figs