Behaviour of three chemical forms of tritium in the environment after release from inertial fusion reactors

Abstract

The increasing demand of results on the environmental effects of the tritium emission is due to the closer construction of experimental fusion facilities arriving to ignition and gain, and experimental reactor (ITER). In the current design studies, it is indicated that the elementary tritium (HT) overcomes in some cases in one order of magnitude the effects of potential releases of tritiated water vapour (HTO). To fully simulate the behaviour of these chemical forms, diffusion and deposition processes in the soil and vegetables need to be considered. In addition, this work also incorporates the penetration in the underground, re-emission and later conversion to organic tritium (OBT). he whole study drives to the conclusion that the behaviour of the tritium should be simulated using two well-differentiated studies: deterministic and probabilistic. Deterministic calculations are based on fixed meteorological data given a priori. The probabilistic study is based on measured real meteorological analysis every hour, and the probability that individuals can present dose for internal irradiation is considered. Both options have been considered for an specific environment of Mediterranean location of the system. Then the elementary tritium has been deposited in the soil, it can be oxidized by microbial action of the enzymes of the soil, and the resulting tritium form (in its oxidize form) goes back to the atmosphere. This process of re-emission is shown to be very important in this work since it has been typically considered that the inhaled tritium is only, HTO, when, in fact part of that account is due to the HT converted to HTO and re-emitted to the atmosphere. All our calculations have parallel also been performed for HTO, and they demonstrate that the HT contributes very significantly to the dose for inhalation through the re-emission processes. A final aspect of this work is the dosimetric analysis of the contamination through all ways: inhalation, re-emission and ingestion. Early and chronic doses have been evaluated.