Preliminary simulation of fuel dispersion in a Lead-Bismuth Eutectic (LBE)-cooled research reactor

In the severe accident analysis of liquid metal cooled reactors, it is important to understand the fuel dispersion behavior which may lead to re-criticality and influence on the heat removal under core damage conditions. For the safety investigation of a LBE-cooled research reactor developed by Institute of Nuclear Energy Safety Technology (INEST), six cases with different parameters which influence the dispersion phenomenon in the coolant were simulated with the Neutronics and Thermal-hydraulics Coupled simulation program (NTC). Fuel dispersion transient results in six cases showed that the fuel porosity, coolant velocity pattern, fuel particle diameter and release position have a significant influence on fuel accumulation and redistribution. In these postulated cases, fuel sweep-out and the dispersion effects were dominating processes rather than fuel compaction and no re-criticality took place in the short term (1000 s). These results confirm that the reactor has certain resistance against severe accidents with re-criticality.