Continuous guidance procedure for xenon oscillation control

Abstract

A new concept for the control of axial xenon oscillations in large PWRs has been proved to be effective. The concept 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. This method can give the optimum timing for control rod operations and the target AOp. However this method cannot give continuous guidance to the operator for xenon oscillation control such as the direction and the amount of control rod movement. In order to overcome this disadvantage, we have developed a new control procedure which can provided information on the xenon oscillation at a glance by displaying the relation of the three AOs as a trajectory of (AOp-AOx, AOi-AOx) in the X-Y plane. This trajectory shows a very simple characteristic behavior. This trajectory can give continuous and clear guidance to the operator for xenon oscillation control. The behavior of the trajectory has been proved by both theoretical analysis and by numerical simulations.