Design and Analysis of Prevention and Mitigation Measures against Core Melting under High Pressure in RCS for CHASHMA NPP Unit 2

A motor operated valve（MOV） is added on the Pressurizer for CHASHMA NPP Unit 2,to implement the bleed function in Feed-Bleed cooling mode,and depressurize rapidly the RCS during high pressure core melt in severe accident.This paper analyzes the accident consequence of Station Blackout co-incident with the loss of Diesel Driven Feedwater Pumps using the computer code of SCDAP/RELAP5/MOD 3.1,and the analysis results justify that the added MOV is able to depressurize the RCS effectively to mitigate the accident consequence in severe accident.