Passive core cooling system

Passive Core Cooling System X Safety Injection, Depressurization and Passive Residual Heat Removal... 

Boron Injection (PSIS) Passive Passive core cooling system... 

Passive Core cooling system (CCS) X 2 water storage tanks, 2 air heat exchangers... 

Passive core cooling system X Natural circulation loop from pool, through core nser, to pool... 

The evaluation of containment flooding events addresses the impact of flooding on the SSCs. The APIOOO passive core cooling system, the internal containment compartments, and the equipment locations are designed for internal flooding to maintain post accident long-term cooling flow to the reactor core from the flooded volumes. 

After successful initial operation of the passive core cooling system, the core temperature will be maintained at an acceptably low value and decay heat will be removed for the extended period of time required by the long-lived radioactivity remaining in the core. 

The passive containment cooling system is shown in Figure 6.4-1, and the passive core cooling system is shown in Figure 6.4-2. 

Nitrogen supply in the passive core cooling system Normal residual heat removal system... 

The passive core cooling systems consists of the following subsystems and components ... 

The passive core cooling system is designed to operate without the use of active equipment such as pumps and ac power sourees. The passive core eooling system depends on reliable passive components and proeesses sueh as natural cireulation, gravity injection and expansion of compressed gases. The passive eore eooling system does require a one-time alignment of valves upon actuation of the speeilie eomponents. 

Manual and automatic actuation of the passive core cooling system components is achieved via the protection and safety monitoring system. This is described in Section 6.7. 

The passive core cooling system must provide pH adjustment of water flooding the containment. 

A single start-up feed water pump are capable of delivering sufficient flow to both steam generators in the period following a reactor trip from full power to remove the fission product heat and preclude the need for actuation of the passive core cooling system. 

S.4.2.4 Passive Core Cooling System Pipe Size Increases... 

The following advantages resulted from increasing the pipe sizes within the passive core cooling system to accommodate the increased duty required by the APIOOO ... 

This option results in slightly enhanced performance of the passive core cooling system, at a lower cost than any of the alternatives. It is thus the ALARP option. 

The core make-up tanks are part of the passive core cooling system. They hold cold borated water stored under system pressure for reactor coolant system make-up and boration, and for safety injection to the reactor coolant system in the event of a loss of coolant accident. The amount of water required for the latter duty on an APIOOO is more than that required by the AP600, suggesting the need for larger tanks. 

Alarms are provided in the main control room, to inform the operator of mispositioned isolation valves of the passive core cooling systems that have remote manual control capability. This reduces the probability of valve mispositioning. 

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