Reactor Water ChemistryDOE-HDBK-1015/2-93CHEMISTRY PARAMETERSRev. 0CH-03Page 25SolubilityHydrogen gas (including tritium gas) dissolves to some extent in most materials. Tritiumand deuterium behave like protium, except for small isotopic effects. Hydrogen atomsor diatomic hydrogen molecules and some larger hydrogen-bearing molecules dissolveinterstitially; that is, they diffuse into a structure and locate between atoms or molecularframeworks. As it dissolves, the hydrogen slightly disrupts the structural networks of thematerial and causes expansion. The extent of the disruption, along with the extent ofchemical attractive/repulsive forces between the hydrogen and the material, determinesthe ultimate equilibrium state.SolubilityinPolymers,Glasses,andCeramicsHydrogen gas dissolves as the molecular hydrogen species in many materials. For thesesystems, solubility is generally endothermic and is directly proportional to gaseousoverpressure. The materials in which hydrogen dissolves as the molecular species includeorganic polymers and glasses at less than 150 C. Organic polymers generally haveatomic-scale voids in the twisted polymer chain, and the hydrogen molecules seek thesesites. Hydrogen dissolution in glasses is assumed to be similar.AbnormalChemistryConditionsAs indicated earlier in this module, there are times when actions taken regarding one specificchemistry parameter may affect more than that parameter (such as feed and bleed operations).This may also be the case during many abnormal conditions that the reactor coolant system maybe subjected to.In this section, we will consider the conditions resulting from injection of air, fuel elementfailure, and overheating of resin and discuss the probable changes to other chemistry parametersthat may occur.InjectionofAirInjection of small and large amounts of air into the reactor coolant system was previouslyanalyzed. When sufficient oxygen is added to deplete the hydrogen inventory, acidic pH resultsin those facilities where high (basic) pH is maintained. This reduction in pH is accompanied bysecondary effects to the coolant. The reduced pH causes a change in solubility of the corrosionfilm on facility materials and results in part of this film being released for transport throughoutthe coolant system. This release, or crud burst, is detected by an increase in radiation levels ofthe coolant, increased conductivity, and lowering of the ion exchanger efficiency. Radiationlevels increase because corrosion products that had been attached to core surfaces and werehighly activated by the neutron flux are transported to other parts of the system.
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