LOFT Reflood as a Function of Accumulator Initial Gas Volume

摘要

The effect of the initial gas volume in the LOFT accumulators on the time to start of core reflood, after a LOCA, has been studied. The bases of the calculations are the data used and results presented in the Safety Analysis Report, Rev.1, August 1977, and the data in the RELAP and TOODEE2 program input and output listings. The results of this study show that an initial nitrogen volume of 12 cu ft, or more (at 600 psig initial pressure), would cause start of core reflood in time to prevent the cladding temperature from reaching 2200 exp 0 F. The 12 cu ft initial volume will expand from 600 psig, initial pressure, to about 10 psig (containment pressure shortly after start of LOCA is approximately 8 psig) when all ECC liquid has been expelled from the accumulator. This pressure margin is considered too small; the ECC flowrate will be zero before the accumulator is empty. (ERA citation 03:057039)