Modifications of water chemistry for pressurized water reactors

For commercial pressurized water reactors, the evolution of the water chemistry for both the reactor coolant systems (RCS) and the balance of plant (BOP) systems has been in concert with or responsive to the changes in specified materials and operating experience. Much of the early reactor coolant chemistry was identified within a program to develop the use of boric acid as a water soluble neutron absorber for chemical shim. Boric acid was selected as the absorber. The BOP steam and feedwater cycle chemistry was largely a translation from conventional low-pressure boiler water chemistry with specific changes to account for new materials in major components. Today's chemistry for the reactor and BOP systems has undergone significant changes since circa 1950. With advances in the design duty of the plant components and with a much better understanding of the mechanisms of corrosion of component materials, the water chemistry practices and methods of control are more successfully aimed at plant reliability than ever before. This paper presents a review of several important advances in water chemistry, as applied to both the RCS and the BOP and the basis for their adoption