Post-LOCA control room dose analysis for Maanshan NPP using the AST methodology

Abstract To address the issue identified in USNRC’s Generic Letter (GL) 2003-01 that the unfiltered air in-leakage rate through plant’s control room envelope during design basis accident may exceed that assumed in the licensing analysis and thus threat the control room habitability, the control room envelope unfiltered in-leakage Tracer Gas Test (TGT) for Maanshan nuclear power plant (NPP) has been performed in 2020. For future applications, an improved control room dose analysis approach using Alternative Source Terms (AST) has been developed in present study to check whether the TGT results meet regulatory limits and have sufficient safety margins. The AST method follows Regulatory Guide 1.183 (RG 1.183) and the TGT results must be fulfilled the total effective dose criteria set forth in 10 CFR 50.67. Based on the AST approach and the TGT results, the control room personnel dose for Maanshan NPP during Loss of Coolant Accident (LOCA) is 14.35 mSv, and the safety margin is 71.3%. It is sufficient to cover the effects of structural ageing and changes in meteorological data during the control room habitability reassessment and the analysis uncertainty.