PLUS7TM Growth Performance after Three Cycle Irradiation

Four lead test assemblies (LTAs) for an advanced nuclear fuel, PLUS7TM, which has firstly been developed in Korea in 2002, was irradiated in cycle 5, 6 and 7 at Ulchin unit 3. The LTAs were reached to fuel assembly burnup of 53,214 MWD/MTU, the maximum fuel rod average burnup of 58,139 MWD/MTU, and the duration of irradiation of 1406 effective full power days (EFPD). Poolside fuel examinations such as visual inspection and accurate measurement were performed in spent fuel pool to confirm the irradiation performance of the advanced fuel after each cycle. Measurement items for the assembly performance due to irradiation were assembly growth, assembly bow, assembly twist, top nozzle-rod gap (for rod growth evaluation), rod-rod gap (for rod bow evaluation), grid width increase. As the effects of deformation, i.e., bow or twist due to irradiation were negligible, the irradiation growths of assembly, rod and grid width are described in this paper. As the result of evaluation related to irradiation growth, PLUS7TM was irradiated successfully without any abnormal phenomenon