Reactor Water Chemical Cleanup Systems are used in light and heavy water reactor designs. The function of this system is:
- Provide normal makeup to the reactor cooling (PWR) or reactor recirculation (BWR) system
- Provide seal water to the reactor cooling pumps (PWR) or reactor recirculation pumps (BWR)
The water passes through isolation valves, then through heat exchangers which cool the water, then to ion exchangers. There are 3 types of ion exchangers:
- Mixed bed which removes undesirable positive and negative ion species
- Cation which can be used to lower the pH in the reactor cooling system
- Deborating ion exchanger which is used during the last days of an operating cycle to reduce the boric acid concentration, since this method is more efficient at removing the boron when the concentration is low (less than 100 ppm boron).
The water then passes to a Volume Control Tank which acts as a reservoir for makeup as needed to the reactor cooling system. The return function would be considered as part of the (Normal) Reactor Makeup function. This is another function of the CVCS system. The hydrogen gas is added in the Volume Control Tank. Lithium Hydroxide is added to the suction of the pumps that return the water to the Reactor Cooling System.
The following diagram illustrates the general layout of a CVCS or RWCU system