(CUW:reacior waler cleanup system)

primary containment vessel

filter demineralizer

cuw regenerative heat exchanger

Figure 2.8.7 Outline of CUW system

reactor pressure vessel

primary loop recirculation pump

from

~ feed waler pump

to radioactive waste treatment system

to condenser

non-regcneralive heat exchanger

reactor water cleanup system recirculation pump

reactor building cooling water system

non-regenerative heat exchanger

reactor building cooling waler system

impurities by the filter demineralizer and reheating by the regenerative heat exchanger, the water is returned to the reactor through the feed water system. During the reactor shutdown process in the ABWR, the full system flow can be sprayed over the reactor through the RPV head spray. The heat removed by the non-regenerative heat exchanger is released to the sea through the reactor building cooling water system. A water discharge line downstream from the filter demineralizer to the radioactive waste treatment system is also installed.

2. Key components and features

Table 2.8.3 shows key specifications of the key components.

1. Circulation pumps

During normal operations, the pumps are at a high pressure suction condition of about 7 MPa (gauge), and hence severe requirements are imposed for the shaft seal. Earlier mechanical seal type pumps were used; however, the non­seal canned motor type has recently been adopted as the standard type in order to enhance the seal reliabilities. Figure 2.8.8 shows an outline of the CUWpump (canned motor type).

2. Heat exchangers

This system has one regenerative and one (or two) non-regenerative heat exchangers. In order to absorb heat expansions due to the high temperature flow, the U- tube type heat exchangers are used. The regenerative heat exchanger has three shells per unit, and the non- regenerative heat exchangers have two shells per unit

3. Filter demineralizers

Two filter demineralizers of a 50% capacity each are installed in parallel and both are operated during plant normal operations. Filter demineralizers are the pre-coat type in which the powdered ion exchange resin is coated onto the element tubes. Since the spent resin cannot be regenerated, it is transferred to the radioactive waste disposal system through the resin collection tank and stored.

2. Fuel Pool Cooling and Cleanup (fpc) System

1. System functions and configuration

The FPC system maintains water qualities of the spent fuel pool water and cools the water used

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( canned motor type )

Figure 2.8.8 cuw pump (canned motor type)

for decay heat removal from spent fuel. It has the following functions.

1. The FPC system removes decay heat of spent fuel, temporarily stored in the power station. In recent plants, the FPC is often designed to have two heat exchangers capable of removing the decay heat generated on the 21st day after reactor shutdown, taking into consideration a time margin for the plant periodic inspection schedules.

2. The FPC system keeps the spent fuel pool temperature at about 50 °C during

normal operations or below about 65 °C even in an abnormal event

3. The FPC system removes corrosion products, fission products and soluble inorganic materials, which are carried in by spent fuel.

Figure 2.8.9 has an outline of the FPC system. In the FPC, the overflow from the water pool is provisionally received in the skimmer surge tank, pressurized by the circulation pump, purified by the filter demineralizers, cooled by the heat exchangers and returned to the spent fuel pool. The heat removed by the heat exchangers is discharged to

NSRA, Japan

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