Modifications for Better Control of the First Radial Mode During Load-Cycling of the ACR-1000

Abstract

A load-cycling capability of the ACR-1000 is an attractive feature of the new reactor. Changing the reactor power from 100% FP to a lower value and then returning back to full power on a daily cycle is challenging, from a control point of view, because of the xenon transient induced and the flux perturbations that occur due to control rod movements. New control logic, was developed to facilitate the load-cycling transient. It is based on a newly introduced Radial Overpower Tilt Parameter (ROTP) as a measure of how much the first radial mode is excited due to transient reactivity disturbances in the core. The control algorithm is designed to reduce bundle and channel overpowers, (i.e., flattening the neutron flux) during load following operations by holding the ROTP close to unity as much as possible. This new algorithm and its impact on reactor control during load-cycling will be discussed in the paper.