10.2172/1079302

Abstract

This is the fourth in a series of reports on the response of a BWR/5 boiling water reactor to anticipated transients without reactor scram (ATWS) when operating in the expanded operating domain MELLLA+. In this report ATWS events initiated by closure of main steam isolation valves are analyzed at beginning-of-cycle, and end-of-full-power-life, conditions. The objective is to understand the sensitivity of ATWS-ED events to the intial operating core flow and to the spectrally corrected moderator density history (void history). Different water level control strategies are considered. The ATWS events are simulated for a sufficiently long time (2500 s) to understand the response of key components and the potential for fuel damage or damage to the wetwell (suppression pool). These events lead to the automatic trip of recirculation pumps; and operator actions to activate the emergency depressurization system when the wetwell has reached the heat capacity temperature limit, and to control power through water level control and the injection of soluble boron. The simulations were carried out using the TRACE/PARCS code system and models developed for a previous study with all relevant BWR/5 systems.