Analysis of the MSLB M/E Release for Framatome NPPs using RELAP5/MOD3.3

KHNP is planning to refurbish Framatome nuclear power plants (NPPs) with replacement of steam generator (RSG) and power uprating (PU). The environmental qualification (EQ) envelop curve in current Framatome NPPs FSAR should be modified according to the refurbishment. An analysis of the mass and energy (M/E) release following a main steam line break (MSLB) outside containment was done using LOFTRAN-COMPARE code. However, the analysis results for the steam bunker with LOFTRANCOMPARE code showed too high temperature of 209.05 .deg. C as the generic limit of EQ temperature is 182.2 .deg. C. To address this issue, we have used RELAP5- COMPARE code, and took account recommendations of the standard review plan in this study. There is a significant difference between two codes in simulating the superheating by the heat transfer to steam from the uncovered portion of the SG tubes. The calculation results of M/E release following a MSLB using RELAP5/MOD3.3 are presented, and compared with those of the LOFTRAN