Research on code coupling method in severe accident simulator development

Abstract After Fukushima nuclear accident, the newly published nuclear regulation featured requests for the development of severe accident (SA) simulators in operator training. In response to such requests, this research deals with a code coupling method, the coupling of thermal-hydraulic system analysis code with integral SA code. Based on the existing full-scope simulator (FSS), the architecture of SA simulator was designed through the method. The crucial technical route is that the RELAP5/MOD3.2 code is utilized for early response, when the coupling condition is met, it switches to MAAP4.0.3 code to calculate middle-late accident. To ensure smooth transition, their major differences were analyzed and some coupling parameters were selected. A test case of SBLOCA was performed via RELAP5-couple-MAAP4, and some specific quantitative assessments were defined to justify the method. The results show a smooth transition between RELAP5 and MAAP4 is achieved and is expected to extend FSS function to SA field.