Abstract Three different accident consequence assessment codes have been applied to assess the dose to the most exposed individual for unit releases of tritium and activated AISI-316 steel into the atmosphere and the aquatic environment. Co-60 has been identified, within both release scenarios, to be the most hazardous of the investigated radionuclides. Whereas no prevailing exposure pathway could be identified for the airborne releases, the ingestion pathways dominate the dose for the releases into rivers. Doses from 1 gram unit releases of activated steel and tritium in HTO form give higher individual and collective doses (about one order of magnitude) for tritium. Doses from the aquatic releases are lower than those from the atmospheric releases by about two orders of magnitude. But simplifications in the water release scenario indicate that the calculated values have a preliminary character. Probabilistic assessments, taking into account for the differing environmental conditions pertaining at the time of an accident, estimate the variability of the dose values.