Modelling 36Cl in soil-plant system: A phenomenological approach and its application to the discharge of 36Cl in groundwater from radioactive waste deep storage site

Abstract

Chlorine 36 is considered as part of the group III of radioactive wastes composed of the moderate radiotoxic radionuclides such as Carbon 14. As such and along with its long half-life (3.01 × 10 5 years) and its chemical form (chloride anion), it is a very important radionuclide to be taken into account in the environment thereby making its modelling an important goal. We present in this paper the phenomenological approach developed at IRSN for modelling the behaviour of chloride 36 in the continental ecosystems. This model is a part of the SYMBIOSE programme (SYstemic approach for Modelling the fate of chemicals in the BIOSphere and the Ecological systems) whose main goal is to develop a modelling platform able to sustain an environmental chemical risk assessment. Such an approach has been found necessary for Chlorine 36 when the classic models (conventional transfer factor models and specific activity models) fail (for instance in case of acute release of radionuclides). Only the part of the model dealing with the agricultural soil-plant system is described here in detail: interaction matrices, components description, components equations, independent variables, and data. Then, we present an application of this model to investigate chlorine 36 behaviour in soils and uptake by plants after its discharge in groundwater from a radioactive waste deep storage site. Finally, we present results from an intercomparison study performed under the BIOPROTA international cooperation framework.