Modelling transfers of carbon 14 emitted by pressurised water reactors under normal operating conditions, in continental ecosystems

¹ Institute of Protection and Nuclear Safety, Department of Environmental Protection, Laboratory of Experimental Radioecology, BP. 1, 13108 Saint-Paul-lez-Durance cedex, France
² Institute of Protection and Nuclear Safety, Department of Environmental Protection, Laboratory of Environmental Modelling, BP. 1, 13108 Saint-Paul-lez-Durance cedex, France

Abstract

A model of transfers of ¹⁴C in the terrestrial and freshwater environment, emitted by atmospheric and liquid discharges from Pressurised Water Reactors under normal operating conditions, is proposed. Despite the complexity of the ecosystems involved, a simple assessment of the transfer pathways in the environment may be envisaged on the basis of the following assumptions : (a) ¹⁴C behaves like ¹²C with an isotopic ratio between the two isotopes that is unvarying during all considered transfers, and, (b) the ¹⁴C concentrations in the environment are constant over time, which is only valid for chronic discharges. This model takes into account the chemical form, mineral or organic, of the released ¹⁴C, and the input of ¹⁴C through the irrigation water in the case of terrestrial agricultural products. An example of human dose calculation is achieved on the basis of a standard diet, assumed to be entirely self-consumed and contaminated by a chronic discharge. In this case, the annual dose equivalent by ingestion is respectively 40 µSv year^-1 for a volumic air activity of 1 Bq m^-3, and near 0,1 µSv year^-1 for a volumic water activity of 1 Bq m^-3.