2H2Oradiation2H2O2H2OH2OH3OOHeaqH3OHH2OeaqH2OHOHEFFECTS OF RADIATIONDOE-HDBK-1015/2-93Reactor Water ChemistryON WATER CHEMISTRY (SYNTHESIS)CH-03Rev. 0Page 2Both of these species are very reactive chemically, and there are several reaction pathwaysavailable to each. Some of these mechanisms are very complex and are usually of little practicalvalue to the reactor operator, who is more concerned with the overall, observable effects. Inthe case of water, the overall effect of irradiation is shown in the following reaction.(3-2)Because this result is not at all apparent from Reaction (3-1), the following section describesthe intermediate processes in some detail. This discussion is presented only to illustrate thetypes of reaction mechanisms that occur in irradiated solutions. Subsequent discussionsprimarily involve only the overall effects of these processes.Reaction (3-1) shows that irradiation of pure water produces an electron and a H O ion. As2+stated, both species are highly reactive. The H O ion rapidly reacts with a water molecule as2+follows.(3-3)The species OH is an uncharged hydroxyl group. Neutral groups such as this, in which allchemical bonding capacity is not satisfied, are common intermediate species in chemicalreactions and are called radicals or sometimes free radicals.The electron produced by Reaction (3-1) first forms a species called the hydrated electron,denoted by e. The hydrated electron may be thought of as resulting from the interaction ofaq-a negative electron with the positive end of a polar water molecule. This is analogous to theformation of hydronium ions by interaction of a positive proton (H ) with the negative end of+a water molecule. Because the water molecules associated with hydrated electrons do notparticipate in subsequent chemical reactions, they are not shown in chemical equations, and thehydrated electron (e) is used instead.aq-Hydrated electrons may interact with H O ions in solution or with water molecules. Both3+reactions produce another reactive species, atomic hydrogen.(3-4)or(3-5)Reaction (3-4) usually predominates.
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