LPCS System

Water lost from the reactor vessel collects in the drywell to the level of the weir wall and then flows into the suppression chamber. This establishes a closed loop allowing the spray system to continue to operate until the operator manually stops it. 

A bypass line to the suppression pool capable of rated core spray flow permits testing while the power plant is in service. A motor-operated valve controls bypass flow and is operated by a key locked switch in the control room. The position of the valve (as is true for all air- or motor-operated valves) is indicated in the control room. The valve receives a signal to close, which pre-empts all others, in the event that operation of the LPCS system is required. 

To allow for system testing during plant shutdown, reactor water, via a temporary connection (removable spool piece) to the RHR system, is discharged into the reactor vessel through the core spray sparger. The spool piece is removed prior to plant startup and the open pipe capped. 

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Starch In sheep, in rats Improved bioavailability with microsphere/enhancer (LPC) system 59... 

Steam condensing Containment spray Suppression pool cooling High-pressure core spray (HPCS) system Low-pressure core spray (LPCS) system Automatic depressurization... 

Selected safety/relief valves are associated with the automatic depressurization of the primary system under assumed LOCA conditions. These valves have two independent logic channels powered from different power sources, either of which can initiate depressurization. Valves open automatically and remain open imtil the pressiue falls to a preset closure pressure. These valves open automatically upon signals of high drywell pressure and low reactor water level and confirmation of one LPCI function of the RHR system or LPCS system running. Initiation signals need not be simultaneous. The valves remain open until the primary system pressure is reduced to a point where the LPCI function of the RHR system and/or the LPCS system can adequately cool the core. The initiation of automatic depressurization is delayed from 90 to 120 s to allow the operator to terminate the initiation should the HPCS system initiation and acceptable reactor vessel level have been confirmed. 

In the unlikely event that the RHR shutdown suction line is unavailable during reactor shutdown to cool reactor water and during the period when the LPCI function of the RHR system and/or the LPCS system pumps are injecting water into the reactor vessel, safety/relief valves used for automatic depressurization can be used to pass water from the reactor vessel to the suppression pool via valve discharge lines. For this to occur, the reactor vessel floods to a level above the vessel main steam line nozzles, selected safety/relief valves are opened from the control room to pass reactor water to the suppression pool. 

The ECCS comprises the LPCl function of the RHR system, HPCS and LPCS systems, and automatic depressurization of the primary system. The ECCS is designed to perform the following functions ... 

The operation of the automatic depressurization function, the HPCS system, the LPCS system, and one LPCI loop of the RHR system (failure of division 2)... 

A combination of the HPCS system or the LPCS system plus any two other ECCS pumps provides two phenomenological cooling methods (flooding and spraying). 

Either the HPCS system or the LPCS system, one LPCl loop of the RHR system with one heat exchanger, and 100% service water flow... 

The LPCl function in conjunction with the LPCS system, the HPCS system, and/or automatic depressurization of the nuclear boiler system (depending upon operability of the HPCS system or level of depletion of reactor vessel water) will restore and maintain the desired water level in the reactor vessel required for cooling after a LOCA. 

The engineered safety features include the ECCS (HPCS system, LPCS system, LPCl function of the RHR system, and the automatic depressurization function of the nuclear boiler system) and the RCIC systems. 

Low water level in the reactor vessel A low water level in the reactor vessel trips the reactor, causes nuclear system isolahon, activates the automatic depressurization function, initiates the HPCS and LPCS systems, and initiates the RCIC system. 

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