The computer program TriStat (Tritium dose assessment for stationary release) was used to estimate the human dose under stationary release and to obtain a conservative estimate of the dose after an accidental release as well. The atmospheric behavior of tritium is described by a Gaussian dispersion model. The tritium concentration in the atmosphere, soil, vegetables and cereals were estimated on the basis of tritium inventory of the facility and the release rate of tritium. In the model description, the specific tritium concentrations for the free water component and the organic component are essential. The food chain for humans was modeled by assuming a forage compartment, a plant compartment and an animal compartment. In the model, a virtual plant and a virtual animal were defined.

The calculation revealed that the exchange of HTO between atmosphere and plant leaves has a critical role for increasing the human dose both for stationary and accidental release of tritium.