The application of nuclear heat in chemical processes involves a novel safety problem caused by contamination of the product gas with tritium. For a 3000-MW(thermal) nuclear process heat installation, a study was made on tritium distribution. Based on conservative assumptions and a calculation model for source/sink balances, an upper limit for the tritium concentration in the product gas of ∼5900 Bq/m3 (STP) was derived. The critical pathway in the application of the product gas then leads to a radiation exposure being far below the German 0.3 mGy ( 30 mrem) annual whole-body dose concept. Improvements in the calculation model and additional data for modified design features may further reduce the tritium contamination.