WATER CHEMISTRY OF LIGHTWATER REACTORS

As of 1994 there were 105 operating commercial nuclear power stations in the United States (1) (see Power generation). AH of these faciUties were light, ie, hydrogen—water reactors. Seventy-one were pressurized water reactors (PWRs) the remainder were boiling water reactors (BWRs). 

in the form of boric acid, is used in the PWR primary system water to compensate for fuel consumption and to control reactor power (3). The concentration is varied over the fuel cycle. Small amounts of the isotope lithium-7 are added in the form of lithium hydroxide to increase pH and to reduce corrosion rates of primary system materials (4). Primary-side corrosion problems are much less than those encountered on the secondary side of the steam generators. 

Kirk-Othmer Encyclopedia of Chemical Technology (4th Edition) 

The primary water specifications for a PWR are given in Table 1 (4). Rigid controls are appHed to the primary water makeup to minimise contaminant ingress into the system. In addition, a bypass stream of reactor coolant is processed continuously through a purification system to maintain primary coolant chemistry specifications. This system provides for removal of impurities plus fission and activated products from the primary coolant by a combination of filtration (qv) and ion exchange (qv). The bypass stream also is used both to reduce the primary coolant boron as fuel consumption progresses, and to control the Li concentrations. 

Values are for normal power operation. Conductivity, pH, and concentrations of lithium and boron are plant specific and vary over the fuel cycle according to the control scheme used. See Fig. 3. 

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A variety of nuclear reactor designs is possible using different combinations of components and process features for different purposes (see Nuclear REACTORS, reactor types). Two versions of the lightwater reactors were favored the pressurized water reactor (PWR) and the boiling water reactor (BWR). Each requites enrichment of uranium in U. To assure safety, careful control of coolant conditions is requited (see Nuclearreactors, water CHEMISTRY OF LIGHTWATER REACTORS NuCLEAR REACTORS, SAFETY IN NUCLEAR FACILITIES). 

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