Development of the Penetration Tube Failure Analysis Program in the Lower Head of the Reactor Vessel During a Severe Accident

摘要

For analysis of an ex-vessel severe accident, the corium melt conditions inside the reactor vessel are important at the time of the reactor vessel failure together with the reactor vessel failure mode. To determine penetration tube failure in the lower head of the reactor vessel during a severe accident, the Korea Atomic Energy Research Institute developed the PENetration Tube Analysis Program 2.0 (PENTAP 2.0) and carried out validation work based on experimental data that can simulate penetration tube heatup, rupture, penetration weld failure, and penetration tube ejection failure. A numerical simulation was undertaken to investigate the effect of the presence of melt in a tube, the expansion direction of the reactor vessel hole, and wall ablation on tube failure using PENTAP 2.0. The simulation results showed that the presence of melt inside the tube helps prevent tube ejection. When melt is not in the penetration tube, tube ejection is strongly dependent on the expansion direction of the reactor vessel hole.