Analysis on Thermal-Hydraulic Behaviour of a Reflector System (From PRDBE to SRBDBE)

Heavy water is used as a reflector in a Research Reactor (RR) for high neutron flux around the reflector. There are both issues for operational performance about cooling of the heavy water system (HWS) and for operational safety about transients related to the reactor power in the research reactor. Here the HWS was analyzed from the point of performance presenting the operational limits and conditions about operation of the HWS: operation of pumps, control of heavy water inventory, and loss of heavy water cooling. And the reactor was investigated about safety issues including the identification of causes, sequence of events and system operation, computational models, input parameters and initial conditions, results, radiological consequence including analysis of the Safety-Related Beyond Design Basis Event: loss of cooling heavy water, loss of heavy water, downgrading of reflector. The beyond design basis accident such as Common Cause Failure of a digital Reactor Protection System is also covered to the extent as in detail as necessary. The results from the analyses have shown that both the performance and the nuclear safety related to failures in the HWS can be assured even in the beyond design basis event. (author)