Application of the RETRAN Safety Analysis Model to Increase the Safety Margin during Overpressure Transients

The safety of a nuclear plant is mainly assessed using an Evaluation Model code (EM code). The EM code is a plant-specific code developed by the reactor vendor to consider the specific plant. Thus, it is difficult to apply an EM code to plant design changes or to other types of reactors. As there have been plant design changes since the 90's, attempts have been made to substitute EM code with RETRAN for Non- LOCA safety analyses. RETRAN is a very flexible code for changes to the nodal configuration that is applicable to every reactor type. However, differences in the analysis results between RETRAN and EM code have not been verified due to complex code algorithms. Nevertheless, the analysis results should have good agreement irrespective of the analysis code under the same analysis assumptions. In this study, a RETRAN analysis is performed under the same assumptions used with the EM code model, and a method to increase the safety margin during overpressure transients is discussed