Strategy and experience of PCI protection and load following operation in KWU LWR plants

The strategies of protecting the fuel against PCI failures during plant operation are described. The basic concept involves a sliding PCI limit for the local peak power, which accounts for conditioning effects of the previous power history. Plant specific features and the use of control rods are summarized for PWR and BWR plants. KWU PWRs are equipped with fully automatic control and limitation systems, which allow fast load following operation within the operating and PCI limits. Experience shows that the methods are 100% successful to prevent PCI failures, and that the plants can be operated without restrictions. In BWRs, administrative methods are used with either regional core surveillance by in-core detectors or local surveillance by a fast calculator. PCI related restrictions are presently removed or minimized by introducing new fuel designs (Zr barrier tubing, 9x9 fuel). An increasing number of plants operate successfully in daily or weekly load following modes or with remote control according to varying power demands. The relevant experience is summarized. (author). 10 refs, 8 figs