Liquid Zone Control System Instability Test Program

Abstract

CANDU® operators have observed occasional reactor control instabilities that are clearly linked to the operation of the Liquid Zone Control System. AECL has undertaken a program to take a comprehensive look at system experience and focus on the root cause of the instabilities. A full-scale experimental program covering a range of representative flows, temperatures and gas densities was undertaken to define the nature of the instability and test design fixes. This work confirmed that support plate restrictions lead to instability and defined the range of conditions. It has led to an improved plate design that has sufficient open area to avoid water “separation”. It can be considered in new stations or refurbishment projects.