5. Reactor Building Cooling Water (rcw) System and Reactor Building Cooling Seawater (rcws) System

1. System functions and configurations

The purposes of the RCW and RCWS systems are to cool components mainly located inside the reactor building during plant normal operations, and to remove the decay heat and to cool the emergency components in case of an emergency. The system functions are as follows.

1. They can cool components sufficiently during plant normal operations and their pumps and heat exchangers have spare units.

2. As for the decay heat removal in an emergency, one division of the RCW system or the RCWS system should have sufficient capacity to remove the required heat amount

The functions of components in these systems can be divided into the following two parts.

1. Cooling the plant auxiliary equipment

2. Cooling the emergency plant auxiliaries (including the residual heat removal)

The system configurations differ from plant to plant There are mainly two configuration types; the separated type and the mixed type. The separated type keeps the above two functions separate and the mixed type combines them.

In Japan, power plants are built on the seacoast and seawater is used as the heat sink. Some early plants have a cooling system which directly cools the components by seawater. But the standard design of recent plants has adopted an indirect cooling system which has an intermediate loop between the cooled side and the cooling side. Figure 2.8.10 shows an example of the mixed type system, which has both functions of plant auxiliary cooling and emergency plant auxiliary cooling.

The emergency plant auxiliary cooling system is divided into the same number of divisions as the ECCS, and each division runs independently.

2. Key components and features

i) Cooling water pumps

The cooling water pumps (intermediate loop circulating pumps) supply the necessary amount of cooling water in normal and emergency operating modes, and their capacity is determined as follows. For the normal operating mode,

Figure 2.8.10 Basic concept of rcw and rcws systems (example)

each pump has a spare unit but for emergency operating modes, it does not The standard pump type is the horizontal single stage type.

2. Seawater pumps

The total pump head of the seawater pumps is determined by considering the pressure loss of the RCWS and the change of the seawater level, which is changed by tidal modes, waves and tsunamis. The standard pump is the vertical turbo type.

2. Heat exchangers

The heat exchangers have a capacity to remove heat even when the seawater temperature is at the highest design condition. Seawater goes through the tube side of the heat exchanger and the cooling water goes through its shell side. The standard heat exchanger is the horizontal straight pipe type.

NSRA, Japan

2~ 100