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.