ANALYSIS OF ACCIDENT MANAGEMENT IN STEAM-GENERATOR TUBE RUPTURE EVENT

As a part of the preparation of the database of calculated results on severe accident sequences for emergency preparedness at nuclear power plants, steam generator tube rupture initiated severe accident sequences at a reference two-loop PWR plant have been analyzed using the THALES/ART computer code. Estimation were made of the times of key events such as core uncovery, core melt and reactor vessel melt-through, and an amount of fission products released to the environment. The effects of recovery action on core integrity and the amount of environmental fission products released were studied with regard to the discussion on mitigation of or recovery from the accident by the feed and/or bleed operation in the primary and/or the secondary system. The analysis showed that (1) the ECCS has adequate capability of maintaining core integrity, and (2) the bleed operation in the primary system is effective to suppress the environmental fission products released even if the ECCS did not function.