Characteristics and behaviour of 14C and 36Cl in the biosphere in the context of radioactive waste management

Evaluation of the safety of high-level radioactive waste repositories is a requisite included in radioactive waste management policy. Criteria for the safety of those facilities require protection of the population and the environment over a time scale appropriate to the characteristics of the radionuclides present in the disposed wastes. In order to demonstrate compliance with regulations, a quantitative analysis of the system must be carried on, including the transport of radionuclides from the facility to the biosphere and through, and the assessment of radiation doses from both external and internal exposure. Previous assessments, demonstrate that some radionuclides contribute more to the annual dose to humans. Among these, 14C and 36Cl must be considered. Realistic models to simulate transport of radionuclides in the environment are essential. A biosphere model should represent the transport and accumulation of radionuclides in the different media, and include characterization of the pathways through which the contaminants reach the population giving rise to the exposure to radiations. This paper shows general guidelines for the behaviour of 14C and 36Cl in the environment and the definition of a conceptual model of radionuclide transport in the biosphere.