Evaluation on the Effect of Steam Generator Model on Feedwater Line Break Accident in terms of RCS pressurization

A project to substitute CESEC-III, a licensing code for non-LOCA analysis of CE (Combustion Engineering) type nuclear plants, with the RETRAN-3D code has been proceeded since 2001. Implemented with realistic models, RETRAN-3D can be applied to the simulations of non-LOCA, ATWS, and small break LOCA in both PWRs and BWRs. This paper presents an evaluation on the effect of the Steam Generator (SG) models on the analysis of Feedwater Line Break (FLB) accident. Dominant thermal hydraulic phenomena influencing the primary system pressurization during the accident include heat transfer in the SG and critical flow through break. In addition, node configuration for the SG and code specific conservative assumptions also has significant impact on the predicted RCS pressure. The effect of different SG models in RETRAN-3D and CESEC-III on the FLB was assessed by comparing code predictions of major system parameters