Two mathematical models have been derived for chemical decontamination of nuclear reactor films, starting from mass transfer and kinetic fundamentals. The first model predicts a linear field decrease with time, while the second model implies an exponential decrease. Both models are compared to Westinghouse experimental data. The exponential model agrees very well with the boiling water reactor decontamination data, generating gross rate constants of 0.875 to 1.105 h−1 at 121°C. Neither model correlates well with the pressurized water reactor data. This modeling exercise indicates that field decrease versus time is a better approach than the raw “decontamination factor” normally presented in the literature. It also suggests that specimen effective surface area and related properties should be measured. Both avenues should be pursued in future decontamination programs.