Steam Generator Secondary pH During a Steam Generator Tube Rupture

The iodine concentration in the steam generator secondary vapor must be determined in order to estimate the environmental consequences (i.e., iodine source term to the environment) due to a steam generator tube rupture (SGTR). Experimental evidence indicates that this concentration is sensitive to the liquid-phase pH. A thermodynamic-based calculational approach was used to model the pH during a design-basis SGTR. The EQUILIBRIUM code within the Facility for Analysis of Chemical Thermodynamics was assessed for calculation of pH by comparison with measured pH’s in operating pressurized water reactors (PWRs). The pH was calculated for ten generic PWR designs (one Babcock & Wilcox, three Combustion Engineering, and six Westinghouse). The calculated pH was shown to be relatively insensitive to PWR design. The pH for all designs equilibrated to a value of ∼6.5.