Reactor Vessel Fluence Reduction Approach Through Low-Leakage Fuel Management at Kori Unit 1

Abstract

An analytical approach to evaluate the relative degree of reactor vessel fluence was performed to support the Kori Unit 1 plant lifetime extension program which has been carried out by Korea Electric Power Corporation (KEPCO) since 1993. In order to reduce reactor vessel fluence, neutron economy requirements regarding lower-leakage of neutron in the core has been considered in determining a loading pattern. The radial peaking factor limit affecting neutron leakage in the core is appropriately relaxed with extra thermal margin ensured from both new steam generators to be installed in 1998 and an advanced thermal design procedure. Using the relaxed peaking factor limit established appropriately, several lower-leakage loading patterns are modeled and analyzed to see a relative effect of each loading pattern on the reactor vessel fluence. It is found that the lower-leakage fuel management, with the relaxed peaking factor limit, can not only reduce the reactor vessel fluence enough to extend the Kori Unit 1 reactor vessel lifetime to 32 EFPY , but also increase the plant availability by improving fuel efficiency. Therefore, it is concluded that the lower-leakage fuel management strategy in Kori Unit 1 is the most economical way to extend its reactor vessel lifetime.