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Feedwater pumps are tripped at both sides. Normally PCTRAN splits the 4-loop plant into one loop as side “A” and 3 remainders lumped together as side “B”. For this case they are split into 2 by 2. A single input integer represents the left side number. The SG low-level reactor trip set point is set at 35%. The pressurizer post-trip set point is apparently still 60% rather than the Westinghouse’s typical value of 20%. MSRT is set at 1415 psia. Other assumptions and the sequence of events are according to the following table. Offsite power is available, thus the reactor coolant pumps, charging and pressurizer heater and spray are all functioning. EFW is assumed to feed only 2 of the 4 steam generators.
PCTRAN’s SG initial level 440” is normalized to 168,000 lbm water inventory in each steam generator. The dryout time for the 2 SG;s without EFW feeding is about 4,800 seconds. It is considerably longer than Areva’s result of about 1,800 seconds. The possible reason is owing to lowing of the water level in the affected SG’s, the heat transfer rate is reduced considerably. The other two SG’s take larger heat load for removing the core decay heat. This is confirmed by the heat transfer rates from the two sides in the following figure. The two side’s are about the same prior to the top of the inverted-U bend is exposed. Afterwards the fed side “B” takes a larger and larger share until the drying side “A” becomes completely empty.
