Analysis of a LOCA Generated by the Double-Ended Shear of the Lower Plenum ECCS Injection Line in the LOFT Reactor Plant

摘要

The LOFT reactor incorporates a 4-inch diameter Emergency Core Cooling System (ECCS) line which injects ECCS water directly into the lower plenum of the reactor vessel. Exterior to the vessel, the line contains a check valve within one foot of the vessel. The results are presented of an analysis performed using conservative evaluation model assumptions to determine the consequences of a LOCA generated by a double-ended shear of the 4-inch injection line between the check valve and the pressure vessel. The RELAP4/MOD3 and RELAP4-REFLOOD computer programs were used to perform the associated calculations. The Evaluation Model (EM) options were employed during blowdown and reflood. Specific hot channel calculations were not performed. The lower plenum injection line LOCA is considered to be an intermediate size break. Concurrent with the LOCA, a worst case electrical failure in the LOFT plant was assumed. This assumption limited the amount of ECC water available to that contained in Accumulator B and that delivered by the cold leg HPIS pump. The results from this analysis show that the available ECC water will not be sufficient to quench and cover the upper one-third of the LOFT core. (ERA citation 04:013390)