Dynamic calculations of the IAEA safety MTR research reactor Benchmark problem using RELAP5/3.2 code

Nowadays, increased attention to safety issues for nuclear research reactors has emerged as a consequence of their enlarged commercial exploitation. Almost all of the research reactors safety analyses were, so far, performed using conservative computational tools. Currently, the application of Best-Estimate methods constitutes a real necessity in order to get a more realistic vision of the system behavior, and overcome constraining limits related to conservative approaches. The aim of the current work is an attempt to apply this technique using the system thermal-hydraulic RELAP5/Mod3.2 code. For this purpose, the IAEA 10 MW MTR pool type research reactors Benchmark problem is considered. The exercise consists in performing some fast transients related to typical reactivity induced accidents, and relatively slow transients related to loss of flow accidents. The RELAP5 results were compared against previous data obtained by various conservative channel codes. Differences between the two modeling approaches are afterwards emphasized and discussed.