N(CH3)3H2ONH(CH3)3OHR SO3HH2OR H2HSO4heatR CH2N(CH3)3ClR CH2N(CH3)2CH3ClheatDOE-HDBK-1015/2-93Principles of Water TreatmentDISSOLVED GASES, SUSPENDED SOLIDS, AND pH CONTROLRev. 0CH-04Page 25Reaction (4-24) produces an alcohol form of the resin, which has no exchangecapability, and trimethylamine (TMA), N(CH ) . TMA is a weak base, similar to33ammonia, that reacts with water as follows.If large amounts of TMA are released to the coolant, the pH may increase noticeably.For example, 1 ppm of TMA in reactor coolant that uses lithium resin will cause anoticeable increase in pH. TMA may also interfere with the analysis for chloride ions(which is routinely performed on reactor coolant) by giving a false indication of highchloride concentration. Another significant property of TMA is its intense odor of deadfish. Although the presence of such an odor from reactor coolant is not definitive forTMA, it may give an indication of resin overheating.The methyl alcohol (CH OH) produced by Reaction (4-25) is not expected to have a3harmful effect on the reactor coolant system. The other product of this reaction[R - CH N(CH ) ] is an amine with exchange capabilities considerably less than the232original form of the resin. Thus, both reactions lead to partial (or complete) loss ofexchange capability. If the temperature is sufficiently high, or if a lower temperature(greater than 180 F) is sustained for a long enough period, the resin will be unfit for use.Cation exchange resin begins to undergo thermal decomposition at temperatures aboveabout 250 F by the following reaction.(4-26)This reaction destroys all exchange capacity of the cation resin and also produces anacid. The Reactions (4-24) through (4-26) are the initial reactions when resin isoverheated. If the temperature becomes very high (greater than about 450 F), thepolymeric base structure of the resin will decompose, forming a complex mixture oforganic tars and oils.The preceding discussion concerned the decomposition of resins in their original forms.It should be noted that if overheating occurs after the resin has been in operation forsome time, part of the resin will be in a different form due to the exchange process. Asa result, some of the previously-removed impurities will be released to the coolant ifdecomposition occurs. For example, the chloride form of the anion resin will formCH Cl by the reaction corresponding to Reaction (4-25).3
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