Analysis of Passive Residual Heat Removal Systems for the Canadian Supercritical Water-Cooled Reactor

Abstract

Passive Residual Heat Removal (PRHR) systems are being developed for the Canadian Super Critical Water Reactor (SCWR), a Generation IV nuclear reactor concept. The Canadian SCWR has two PRHR systems: a primary system that uses light water as the cooling fluid, and a secondary system that uses the heavy water moderator as the cooling fluid. Both PRHR systems use the Reserve Water Pool as their heat sink, and the heat is ultimately transferred to the environment. PRHR systems provide guaranteed decay heat removal via natural circulation under extreme accident scenarios for the Canadian SCWR, and can eliminate the costs associated with the installation, maintenance and operation of active systems that require multiple pumps with independent and redundant electric power supplies. However, considering the weak driving forces expected during natural circulation, careful design and analysis are needed to ensure that the systems perform their intended functions. This paper presents a description of the primary PRHR system for the Canadian SCWR, and an analysis of its performance using the system thermalhydraulics code CATHENA. The goal of the analysis is to demonstrate the heat removal capability of the primary PRHR system during a postulated total station blackout. The paper describes the CATHENA idealization of the Canadian SCWR and its PRHR systems, defines the initial conditions prior to, and the decay power during, the station blackout, and discusses the transient simulation results, including the calculated peak fuel sheath temperature and system pressure.