Development of Technology for Fukushima Issue Adaptation and Inherent Safety Enhancement in PHWR

This research has two goals such as enhancing inherent safety and supporting SA (Severe Accident) issue resolution. First, one of key elements determining the PHWRs' inherent safety are the power coefficient (reactor physics assessment) and the critical channel power (Regional Overpower Protection assessment). Particularly the uncertainty in the reactor power coefficient was addressed both in the domestic CANSAS roadmap and CNSC's (Canadian regulatory body) Generic Action Items(GAI). Thus the research is performed to develop an elemental technology for domestic PHWR physics model and optimal PHWR fuel concept. Second, when compared with PWR, PHWR plants have about two times of zircaloy mass in the core, from which doubled amount of hydrogen is generated. Also, PHWR plants have about twice the coolant inventory mass while the design pressure of containment is less than a half. These threaten the reactor building integrity in the long run under SA in PHWR. Thus key safety issues (such as hydrogen and overpressurization) that would be raised under SA like Fukushima accidents are evaluated and an improvement of the SA analysis code (ISAAC) is performed. Lastly, current SAMG is lack of information on the accident diagnostic and progression prediction, which makes the TSC staffs difficult in real accident conditions. Thus the prototype technologies (such as accident inferring engine and simulator) is developed as key elements to SAM supporting tools called SAMEX-CANDU.