Steam Generator Refill

For small-tube-rupture flows that simulated the flow from the single-ended rupture of up to 16 steam generator tubes in a PWR system initiated at the start of vessel refill, the core thermal response was strongly dependent on the magnitude... 

The trip throttle valve for No. 2 AFW pump was opened by the equipment operators at about 1 53 a.m. After the SFRCS was reset and tripped on low level by the shift supervisor, the AFWS aligned itself so that each AFW pump would feed only its associated steam generator, i.e., the No. 2 AFW pump would feed the No. 2 steam generator. Thus, the No. 2 AFW pump refilled the No. 2 steam generator and its pressure increased abruptly to the atmospheric vent valve relief set point. The turbine governor valve was fully open when the trip throttle valve was opened and the pump delivered full flow for about 30 seconds until the operator throttled the flow down. 

The suppression pool contains borated water to provide a diverse backup to the gravity-driven control rods. Core cooling and decay heat removal is assured, with water returned to the reactor vessel and steam produced by decay heat vented to the suppression pool. The containment overpressure relief periodically opens to vent steam from the suppression pool. There is a three-day supply of water available to accept decay heat. No operator action is required during this time. For longer periods the suppression pool is manually refilled. Emergency diesel generators and core cooling pumps are not required. 

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