A general based charcoal filter model was added to the thermal hydraulics code GOTHIC Version 8.2. The model can be used to simulate unsteady iodide transport and adsorption within a charcoal filter that is used to filter vapor exiting the containment of a nuclear plant. The code accepts user inputs for adjusting filtering efficiency and performs calculations for the time and space dependent concentration of iodides in the vapor phase as well as the adsorbed phase within a charcoal filter.

The model includes advective and diffusive transport for iodides coupled with a sorption kinetics model, including first-order reversible physisorption and second-order irreversible chemisorption. Multiple independent gaseous compounds can be modeled simultaneously. The iodide compounds within these gasses are coupled by a decay-chain model and the combined concentration of the gaseous compounds is coupled to the chemisorption capacity of the filter.

Validation of the model to predict iodide transport and sorption within impregnated, activated charcoal was performed through experimental benchmarking. The validation demonstrates that the numerical solution correctly predicts measured data.