Investigation of a LOCA in a typical MTR by a novel best-estimate code

•A New CFD-based code is introduced that is time-dependent and three-dimensional.•The code is devised for combining with neutronic codes for nuclear reactor analysis.•Point-Kinetics equations with six groups of precursors are selected for this study.•The accident involves reactivity insertion, flow reversal and natural convection.•All required models are developed and implemented into the combined-code.

In this study, a new CFD-based thermo-hydraulic code is introduced and tested on some standard verification problems. This is a time-dependent and three-dimensional code that has no restriction with regard to the details of geometry of solution domain. The CFD-code is also capable of modeling both single-phase and two-phase flow. This code is specifically devised for combining with neutronic codes by a novel scheme. For this study, the Point-Kinetics equations with six groups of precursors are chosen as neutronic part. Methods of solving this set of equations are surveyed with the criterion of best compatibility with the CFD code. The resulting combined code is applied to investigate a loss of coolant accident in a typical MTR. This accident involves reactivity insertion, flow reversal and natural convection simulation. All models required for these phenomena are also developed and implemented into the combined code. The results show considerable improvements in comparison with the conventional conservative approach.