Mathematical Modeling of the Chemical Decontamination of Boiling Water Reactor Components

An analytical model has been derived for the chemical decontamination of boiling water reactor primary systems and components. The model results in a complex, hyperbolic function expression that simplifies to two limiting conditions: boundary layer mass transfer and oxide film reaction control. The latter produces an exponential activity decrease with time, in agreement with the presented data and a previous phenomenological model. Gross rate constants of 0.71 to 1.1 and 0.12 to 0.16 h⁻¹ are calculated for the dilute chemical decontamination process at 121 and 95°C, respectively, with an activation energy of 20 kcal/mol. The model indicates that flow effects are relatively unimportant. Other processes should follow this model, but have different rate constants. Future decontamination efforts should incorporate field/activity measurements with time and specimen surface area measurements into the experimental plan for model verification and a better elucidation of the decontamination phenomena.