DISSOLVED GASES, SUSPENDED SOLIDS, AND pH CONTROL
Principles of Water Treatment
The CH Cl (chloromethane) will be released to the coolant and will decompose in the
radiation field of the reactor core, producing Cl ions. Similarly, the sodium form of the
cation resin will release Na ions by the following reactions.
A number of changes are probable if overheating of resin occurs. Reactor coolant Cl-
levels would probably increase as a result of thermal breakdown and subsequent release.
Ion exchanger effectiveness would be greatly reduced for similar reasons. Radioactivity
levels of the reactor coolant would increase because of the release of impurities collected
and later released from the resin. pH would likely decrease because of the release of H+
ions from the cation resin complex and may cause acidic conditions of the reactor
coolant if the temperature were sufficient (>250 F). Because the anion resin
decomposes at lower temperatures, pH may increase as a result of the release of TMA
and be accompanied by a dead fish odor. Because of the consequences of overheated
resin, stringent temperature limitations are necessary. If overheating occurs, the ion
exchanger should be taken out of service immediately and the cause rectified. The resin
must be replaced prior to placing the ion exchanger back in service after overheating.
The important information in this chapter is summarized below.
Dissolved Gases, Suspended Solids
And pH Control Summary
Because of the presence of impurities, raw water sources undergo treatment prior
to use as makeup water in reactor facility systems. These systems normally utilize
several distinct processes that remove solids, ionic impurities, and gases.
Pretreatment of makeup water is necessary to reduce corrosion, minimize
radiation, and limit fouling of heat transfer surfaces.
If the hydrogen and hydroxyl forms of resin are used, the result is pure, neutral
water. Other forms may be used to remove unwanted impurities from solution
and substitute another substance, such as a base, to help control pH. Resins also
filter solids suspended in a solution, but the efficiency for this is usually less than
the efficiency for removal by ion exchange.