Verification of a Continuous Guidance Procedure of Xenon Oscillation Control

Abstract

A new method for controlling axial spatial xenon oscillations in large PWRs has been proved to be effective. The method is based on two additional newly defined axial offsets, AOi and AOX together with the conventional axial offset of power distribution AOp. AOi and AOx are the axial offsets of power distributions which would give the current iodine and xenon distributions under equilibrium conditions, respectively. Further efforts have been continued to establish a new control concept which can give continuous and clear guidance on a display to the operator for xenon oscillation control. The new concept uses information from AOi, AOx and AOp to display the trajectory of (AOp-AOx, AOi-AOx) in the X-Y plane. The trajectory shows a very characteristic behavior. With these simple characteristics in mind the xenon oscillation can be controlled quite easily. In other words, to eliminate the xenon oscillation, we watch the trajectory and use the control rods to lead the plot to the origin where three AOs are identical. Verification of the concept was carried out based on the full record of the axial offset during a xenon oscillation in an actual reactor and good results were obtained.