Development and Application of a Methodology for the Design of Regional Overpower Protection Systems

Abstract

The Regional Overpower Protection (ROP) system consists essentially of a grid of incore detectors situated in vertical calandria penetrations for shutdown system number 1 (SDS-1) and horizontal penetrations (for most of the CANDU reactors) for shutdown system number 2 (SDS-2). The function of the ROP system is to provide overpower protection to the reactor core for probable normal and abnormal conditions. In particular, for Loss of Regulation (LOR) accidents, the function of the ROP system· is to provide protection against onset of fuel centreline melting under dryout conditions. The flux shape prior to the occurence of the LOR accident affects the performance of the ROP system. In the design of the ROP system, therefore, a design set basis of flux shapes has to be considered. This design set consists of the nominal flux distribution and the flux shapes of the perturbations which may occur in the reactor as a result of reactivity device maneuvering or unlikely, but conceivable, malfunctions of the Reactor Regulating System (RRS).