RWCU system

The purpose of the RWCU system is to maintain high reactor water quality by removing fission products, corrosion products, and other soluble and insoluble impurities. In addition, the system provides a means for water removal from the primary system during periods of increasing water volume. 

The operation of the RWCS is controlled from the main control room. Filter resin back-washing and precoating operations are controlled from a local panel. The cleanup system 

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If a freeze seal fails, it can result In an immediate loss of primary coolant. Of particular concern would be a failure of a freeze seal in a system connecting to the vessel s lower plenum region, such as the reactor water cleanup (RWCU) system at boiling water reactor (BWR) facilities. The stafFhas estimated that the reactor core could be uncovered in less than 1 hour if the freeze seal failed completely in the RWCU system. Freeze seal failures in secondary systems can also be significant because of the potential for consequential failures, such as the loss of decay heat removal. The thermal stresses on the pressure boundary resulting from the freeze seal may affect the pipe metal integrity. 

In BWR/1 plants, the cleanup return sparger distributes the water from the RWCU system in the vessel. The sparger is connected to the RPV nozzle, to which the RWCU system return line joins. Water from the system enters below the steam separator and mixes with reactor recirculating water. The sparger is fabricated from stainless steel pipe and has holes in the front. 

Fig. 6. Impurity flow paths of BWR radioactive contamination (24). RWCU = reactor water cleanup system.

The PWR.ECP code begins by employing a chemical speciation model to calculate the composition of the coolant and the pH at closely spaced points around the primary coolant circuit, including the pressurizer, RWCU, and RHRS loops (Fig. 39). Note that the purpose of the RHRS is to remove decay heat from the core upon shutdown of the reactor. Accordingly, this system is isolated from the primary coolant circuit during normal... 

Fig. 39 Schematic of the primary coolant circuit of a PWR, showing the three principal loops (1) the main loop (SI -SI 2), (2) the reactor heat removal system (RHRS, SI 7-SI 9), (3) the reactor water cleanup unit (RWCU,...

C. CHEMICAL AND VOLUME CONTROL SYSTEM (CVCS) [REACTOR WATER CLEANUP SYSTEM (RWCU) IN BWRsI... 

Shutdown heat removal Two-division RHR Three-division RHR Nonsafety system combined with RWCU... 

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