RCIC system

The RCIC system maintains sufficient water in the reactor pressure vessel to cool the core and then maintains the nuclear boiler in the standby condition in the event the vessel becomes isolated from fhe furbine steam condenser and from feedwater makeup flow. The system also allows for complete plant shutdown under conditions of loss of the normal feedwater system by maintaining the necessary reactor water inventory until the reactor vessel is depressurized, allowing the operation of the shutdown cooling function of the RHR system. The system delivers rated flow within 30 s after initiation. A water leg pump keeps the piping between the pump and the discharge shutoff valve full of water to ensure quick response and to eliminate potential hydraulic damage on system initiation. 

Following a reactor scram during normal plant operation, steam generation continues at a reduced rate due to the core fission producf decay heat. The turbine bypass system directs the steam to the main condenser, and the feedwater system provides makeup water required to maintain the reactor vessel inventory. 

The RCIC system operates independently of auxiliary AC power, plant service air, or external cooling water systems. System valves and auxiliary pumps are designed to operate by DC power from the station batteries. 

The turbine and pump automatically shut down upon  

The steam supply system to the turbine is automatically isolated upon  

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The steam driven RCIC system is provided for the loss of all AC power (i e station blackout) and is also effective for small break LOCAs The ADS and accumulators with emergency coolant at a low pressure of 0 5 1 MPa provide short term emergency core cooling... 

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. 

Since the drain piping is located at the bottom of the pressure vessel, this accident is the most severe one with respect to core flooding. The results show that the accumulator injection system can keep the water level above the top of the core for one day after initiation of the LOCA. Although the active component of the FLS is not activated in the present analysis to show the performance of the ACC, the FLS is supposed to be activated to maintain long-term core cooling by injecting water from the suppression pool, even one day after initiation of the LOCA. For isolation of the reactor, the passive isolation condenser (IC) is introduced for core cooling whereas the RCIC system driven by the steam turbine is eliminated. 

A potential problem in the Reactor Core Isolation Cooling (RCIC) system circuitry of a particular BWR was identified. Within this particular RCIC control system, because of the design of the RCIC steam leak detection circuit, it is possible for a sneak circuit to occur and cause an unintended, nonrecoverable isolation of the RCIC pump in conjunction with a station blackout. There are at least three subtle design aspects which lead to the occurrence of this failure mode (1) the RCIC system contains an isolation circuit, (2) the isolation circuitry is deenergized given a loss of offsite power (i.e., the circuitry is not fed by a nonintemiptible, battery-backed vital AC power supply), and (3) the isolation circuit contains a seal-in circuit. 

Control room fires are of considerable significance in the fire analysis of this plant. Fires in the control room were divided into two scenarios, one for fires initiating in the reactor core isolation cooling (RCIC) system cabinet and one for all others. Credit was given for automatic cycling of the RCIC system unless the fire initiated within its control panel. Because of the cabinet configuration within the control... 

The AFS delay after detecting one of the actuation conditions is taken from that of the turbine driven RCIC system of BWRs. Its influence on the peak temperature for the loss of offsite power event is checked. Due to the water source effect of the water rods, the core coolabihty is not influenced by the AFS delay. On the other hand, the net reactivity tends to increase with the shorter AFS delay because the AFS supplies cold coolant to the core. The peak temperature is higher with the shorter AFS delay. The increase in the cladding temperatiue is about 450°C for a delay time of 15 s and 330°C for 100 s. In spite of the wide variatiOTi of the AFS delay that would cover the actual design point, the degree of the temperature variation is well below that of the safety margin to the criterion. 

Some licensees have a switch to bypass RCIC high steam tunnel temperature trips. Some licensees are evaluating improvements to prevent seal LOCAs from loss of seal cooling which are most important for W plants, but B W licensees identified improvements related to alternate seal flow capability under loss of power conditions. The use of high temperature seals is noted for some W plants. Many PWR IPEs identify AFWS improvements. These include additional backup water supplies such as the firewater system and redundant pump cooling capability. Other reliability... 

Emergency Core Coohng System Division ILLPCI + LPCI RCIC + LPFL(RHR)... 

RCIC - Reactor Core Isolation Cooling System... 

The reactor core-isolation cooling system (RCICS) could have been made available by installing a special short piece of pipe that was stored nearby. 

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