Isotopic dilution model for ³⁶Cl in the French landscape

¹ ECOMatters, 24 Aberdeen Avenue, Box 430, Pinawa, Manitoba, R0E 1L0, Canada
² École Nationale Supérieure d'Agronomie et des Industries Alimentaires, Institut National Polytechnique de Lorraine, Nancy Brabois, 2 avenue de la Forêt-de-Haye, BP. 3, 54501 Vandœuvre cedex, France
³ ANDRA, National Radioactive Waste Management Agency, Parc de la Croix Blanche, 1-7 rue Jean Monnet, 92298 Châtenay-Malabry cedex, France

Abstract

Chlorine-36 is one of the most critical radionuclides to consider in intermediate- and high-level nuclear waste management. Special attributes are long half-life, high mobility, biologically essential element, and massive isotopic dilution in the geosphere and biosphere. A model was developed to predict the radiological consequences of ³⁶Cl to human dose receptors. The approach had three parts, a literature and benchmarking review of other ³⁶Cl models and programs, the development of a ³⁶Cl model suitable for ANDRA applications within Aquabios, and the measurement of stable Cl concentrations and parameter values in the relevant landscape. A major issue was to resolve the degree to which specific activity relationships were useful. Soil-to-plant and aquatic food pathways were modeled using specific activity relationships. For subsequent transfers, the model used more traditional transfer factors. The use of the partial specific activity model simplified the problem and made the model and parameters more general. This is especially relevant for transfers of ³⁶Cl because the concentrations of stable Cl in the environment can vary substantially as a result of oceanic effects and local mineralizations. The preliminary field study confirmed some of the key parameters to add confidence to the chosen parameter values and their ranges.