Development of a method for identifying severe status requiring early entrance of SAMG considering human action time

Abstract

The margin of human action time from severe accident management guideline (SAMG) entrance to reactor vessel (RV) failure was analyzed to compare the required human action time and available human action time based on a severe accident DB developed using MAAP 5.02 code. In order to analyze the margin of human action time, dominant initiating accidents are selected, such as small break loss of coolant accident (SBLOCA), medium break (MBLOCA), large break (LBLOCA), and station blackout (SBO) which account for about 80 percent of core damage frequency (CDF), and the worst scenario was selected in each initiating accident. In the analysis of the worst scenarios, it was confirmed that a human might be fail to prevent RV failure due to insufficient action time. Therefore, in this study, a method that can determine the SAMG entry condition in advance was developed by applying the concept of component state to function recovery procedure (FRP). To verify the developed method, a case study was performed based on the scenarios that feed & bleed (F&B) and aggressive cool down (ACD) operations are not successful within limited time after entering the FRP. As a result, the developed strategy flow chart can identify the SAMG entry condition in advance, and provide a human with sufficient action time to mitigate severe accidents. It is expected that the results of this paper can provide some insights for revising the SAMG, or for developing an integrated accident management procedures (IAMPs).