radiation3H2N22NH3(ammonia)NH3H2ONH4OHradiation2N25O22H2O4HNO3Reactor Water ChemistryDOE-HDBK-1015/2-93EFFECTS OF RADIATIONON WATER CHEMISTRY (SYNTHESIS)Rev. 0CH-03Page 7After essentially all of the oxygen has been consumed by reaction with hydrogen, the nitrogencontained in air will remain. For small air additions, some hydrogen will also remain; thus, thereactor coolant will contain both dissolved hydrogen and dissolved nitrogen. These two gasesdo not react in an unirradiated solution at low temperature and pressure. When exposed toradiation, however, the gases do react by the following reaction.(3-14)Again, this is an equilibrium reaction, and radiation induces the reaction in both directions.Ammonia (NH ) produced by this reaction combines with water to form ammonium hydroxide3(NH OH).4(3-15)Under the operating conditions of reactor coolant, Reaction (3-14) is far from complete. Inmost cases, less than about 10 percent of the nitrogen will be converted to ammonia. If noadditional base were added to reactor coolant, Reaction (3-14) would be sufficient to cause thecoolant to be mildly basic, pH 9. In the presence of added base, however, the reaction has onlya very slight and negligible effect on pH.If the base NH were used to control reactor coolant pH, the reverse of Reaction (3-14) would3be more important. The reverse step of this reaction requires that some of the ammonia addedto the coolant decompose into N and H . Because operating conditions favor this step of the22equilibrium, rather than formation of NH , it would be expected that most of the ammonia added3would decompose. However, the rate of the ammonia decomposition reaction is slow, and thepH of reactor coolant can be maintained in the required range. It should also be noted that thedecomposition of NH would produce hydrogen gas in significant concentrations in reactor3coolant (sufficient to satisfy normal H requirements).2In the event that a large quantity of air is injected into the reactor coolant system, the inventoryof dissolved hydrogen would be rapidly depleted by Reaction (3-13). If the amount of airinjected is sufficiently large, there could be oxygen remaining in the coolant after depletion ofthe hydrogen. In this case, another reaction is available to the oxygen and nitrogen in the air.(3-16)Nitric acid (HNO ) produced by this reaction will neutralize any base contained in the coolant,3and if sufficient acid is produced, the coolant will acquire an acidic pH.
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