Customising a System Code for the Analysis of the Thermal-Hydraulic Behaviour of a Supercritical Pressure Light Water Small Modular Reactor

Abstract The paper reports about the work performed in customizing the RELAP/SCDAPSIM code features for an easier assessment of a conceptual design of a Small Modular Reactor (SMR) operating at supercritical pressure proposed by Schulenberg and Otic [13] in the frame of the EU ECC-SMART Project. First unsuccessful attempts to make use of an NRC version of the RELAP5 code in the analysis of the thermal-hydraulic behaviour of the SCW SMR revealed numerical difficulties at the transition from supercritical to subcritical pressures. This suggested to activate a cooperation for customising an already existing version of the RELAP/SCDAPSIM code, aiming to overcome similar numerical problems and to implement heat transfer correlations in principle more appropriate for supercritical pressure conditions. The improved version of the code, featuring a user defined generalised correlation for heat transfer encompassing several of the presently available literature proposals, was applied in predicting rod-bundle experiments performed by Razumovskiy et al. [16–17] and in analysing the behaviour of the seven core flow passage reactor proposed in [13]. In the paper, the present capabilities of the code are discussed in front of the obtained results and perspectives for future developments are suggested.