Reactor Water ChemistryDOE-HDBK-1015/2-93EFFECTS OF RADIATIONON WATER CHEMISTRY (SYNTHESIS)Rev. 0CH-03Page 9In the preceding discussion, the reactions possible after the addition of air to reactor coolantcontaining hydrogen were described. These are Reactions (3-13), (3-14), and (3-16). Therelative rates of these reactions are of considerable importance. Briefly, Reaction (3-13) is muchmore rapid than either of the others, and Reaction (3-16) is faster than Reaction (3-14). Thus,the sequence of reactions is as described in the preceding sections. H and O react to form22water. If hydrogen remains, it undergoes an incomplete reaction with N to form small amounts2of NH . If O remains after all the H has been consumed, the O - N reaction produces nitric32222acid.The flux of neutrons and protons in a nuclear reactor core region leads to several importantnuclear reactions with the constituent atoms of water. Most of these reactions involve oxygenisotopes and fast neutrons or protons.In many cases, the absorption of a fast neutron by a nucleus is immediately followed by ejectionof a proton. These reactions are called neutron-proton or n-p reactions and are commonlywritten (using the O reaction to illustrate) in the following manner.16O (n, p) N (t= 7.13 seconds)(3-17)1616871/2In this notation, the original isotope that undergoes the reaction is written first, the productisotope is last, and the two are separated by, in order, the particle absorbed and the particleemitted. The isotope N decays to O with a 7.13-second half-life by emitting a beta particle161678() and a high-energy gamma ray (6 Mev predominantly).-N O + + 161678Oxygen-17 undergoes a similar reaction.O (n, p) N (t= 4.1 seconds)(3-18)1717871/2The isotope N decays by emission of a beta particle, a neutron, and a gamma ray.177N O + + n + 17161780Reactions (3-17) and (3-18) have no significant chemical effect on reactor coolant because ofthe relatively small number of atoms that undergo these reactions. They are of considerableimportance, however, because the radioactive species N and N are carried outside the core161777region by the flow of reactor coolant. The neutrons and high-energy gamma rays emitted bythese isotopes easily penetrate the piping and components that contain the coolant and areimportant considerations in the design of shielding for nuclear facilities. Because the half-livesof these isotopes are very short, they decay to low levels very rapidly after shutdown and are,therefore, of little concern during such periods.
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