Analysis of hypothetical channel flow blockage of a tubular fuel assembly in a 10 MWth nuclear research reactor

Abstract Heat removal from the core of nuclear reactors is a crucial safety requirement that needs much analysis and attention. Coolant channel flow blockage is one of the unintentional cases that may influence the required heat removal rate. As a result, unsustainable over heating of the fuel cladding could occur resulting eventually in affecting the fuel integrity. This paper deals with simulating the effect of total channel flow blockage in a single fuel assembly on its steady state thermal hydraulic parameters. Thermal hydraulic calculations are carried out for the much less studied IRT-4M ducted fuel assembly type in a 10 MWth WWR-S tank in pool research reactor. The simulated IRT-4M fuel assembly comprises six rounded rectangular fuel elements in which seven channels are used for cooling. A mathematical model is developed in which all steady state thermal hydraulic parameters and their distributions could be predicted for the blocked and unblocked flow channel cases. Calculations were performed for two separate hypothetical flow channel blockage cases in the innermost channel and the middle channel of the IRT-4M fuel assembly. The results showed that the maximum clad temperatures for the two-flow blockage cases are nearly 127.4 °C, and 132.2 °C, respectively. The temperature increases resulting from a single channel blockage are not high enough to cause fuel damage, although some local coolant boiling might occur. Model validation and results support the model outcomes and its applications in the safety of the research reactor during abnormal operation.