Control of xenon oscillations in large PWRs result of control in Mihama Unit No.3 Reactor

Recently, constant axial offset control method for power distribution control is applied to PWRs (of Westinghouse type). In this mode of operation, Xe induced spatial oscillations which could cause the problem from the power distribution point of view hardly break out. Under special conditions such as tests, however, Xe oscillations can break out. It is required that power distribution can be controlled without any special operational actions. Several control methods for Xe oscillations have been reported through many theoretical studies and operational experiences. Among them is First Overtone Control Method. This requires quite a simple control action but can effectively control Xe oscillations. The authors have shown the effectiveness of First Overtone Control Method in Mihama Unit No. 3 Reactor. In this report the detailed procedures are described. The outline of Constant Axial Offset Control Method is described in Appendix. (auth.)