required to satisfy the single failure criterion, and to have features to ensure redundant components of the system are isolated from each other, when needed. The system consists of two sets of supply and discharge headers for plant safety components and one set of supply and discharge headers for auxiliary components, not essential for the plant safety. When necessary, the two critical cooling headers can be isolated from each other.

Radiation monitors downstream from the component cooling water heat exchangers monitor any leakages of the radioactive reactor coolant into the system.

The CCWS is vital for both the plant normal operations and post-accident operations. It serves as an intermediate cooling loop that removes residual and sensible heats from the reactor and cools auxiliary components of the reactor. The component cooling water system is cooled, in turn, by a sea water system, the ultimate heat sink of the plant.

ii) Functions

The component cooling water system has two functions.

The first is to cool auxiliary components needed for various operational conditions of the plant Components cooled by the system are the residual heat exchangers, the non-generative heat exchanger, the containment spray heat exchangers, the seal water heat exchanger, the excess letdown heat exchanger, and the reactor coolant pumps.

The second function is to serve as an intermediate cooling system between the reactor auxiliary component group carrying radioactive fluids such as the reactor coolant and the sea water system. With this design, radioactive materials are prevented from being released to the environment outside the plant, even if radioactive fluids including reactor coolant are leaked into the component cooling water system,

2. Components

i) Component cooling water pumps

The CCWS normally has four pumps, two of which are used during the plant normal operation. Under post-accident reactor cooling-

NSRA, Japan

3-100

Component cooling water surge tank

S - -

Component cooling water pump ootor k. B

Instrument air compressor a

Containment recirculation unit A, B

Residual heat removal pump t motor A

Charging pump A motor A(B)

Containment sprag cooler A

Residual heat removal cooler A

Spent fuel pit cooler A

Containment spray pump i motor A

High head injection pump 4 notor A

water

cooler

Radiation monitor

Component cooling water pimp ootor C.

Instrument air cos pressor b

Containment recirculation unit C. D

Residual heat removal punp J motor B

Charging pimp t motor CO)

Containment sprag cooler B

[m

Residual heat removal coolei

Containment sprag pump i motor B

High head injection pump 1 motor B

Secondary demineralized water

Primary makeup water tank

Refueling water tank

1

I

I

I

I

I

1

I

J

1

I

I

i

I

I

I

I

I

I

I .Aurillary components,

I [important for safetyj

1

I

I

I

I

I

I

I

I

I

I

I

I

I

tank

Figure 3.8.3 Component cooling water system flow diagram

RCP & motor cooling unit

3-101

NSRA, Japan