Preliminary Evaluation of effectiveness of External Injection Strategy during TLOFW

An Emergency cooling water External Injection System (EEIS) cools the reactor coolant system (RCS) as an emergency means in case of a severe accident due to various combination of initial events that cause the long term unavailability of the emergency core cooling system (ECCS) and Steam Generator (SG) Main Feed Water System. The system is designed to ensure that the heat generated from the core is removed to maintain the integrity of the reactor vessel in the case of the primary side and to maintain water level above the upper end of the tube of the steam generator in order to control the release of fission products from Steam Generator. MAAP 5.03 computer code was used in this evaluation. For Total Loss of Feed Water (TLOFW) scenarios, which are high pressure incidents as with the SBO accidents, preliminary evaluation of the effectiveness of the EEIS strategies has been carried out. Through the evaluation results, various insights on a severe accident management strategies could be derived. The EEIS is designed to inject coolant into the RCS and the SG secondary side to ensure the integrity of the reactor vessel and restore and maintain the water level of the SGs. In this analysis, it was confirmed that emergency cooling water can be injected into the RCS and the SG secondary sides by analyzing various accident situations. In addition, if the external injection is successful, the core is cooled and the water level of the core is restored and the reactor vessel integrity is secured.