Biosphere modelling of radioactive waste disposal system in a safety assessment framework

Abstract

Radioactive waste is a major concern, not only in South Africa, but worldwide. South Africa produces radioactive waste through the full nuclear fuel cycle and the application of radioactive materials in industry, research and medicine. TE-NORM waste, due to a wide variety of mining and mineral processing facilities, is characterise by large volumes but low activity concentrations. The overall objective of radioactive waste management is to deal with radioactive waste in such a manner that human heahh and the environment are protected, now and in the future, without imposing an undue burden on future generations. Radioactive waste does not have any economical value and must finally be disposed. According to the overall objective of radioactive waste management, the impact that the disposed radioactive waste will have on future generations needs to be assessed in such a manner that the safety of the public will be ensured. At present, the only tool available to do so is a safety assessment. The goal of safety assessment as a decision tool is to determine the conditions for which reasonable assurance of compliance with safety objectives can be provided. The implementation of a safety assessment, defined as a multi-disciplinary, iterative process focussed on regulatory compliance, is a highly technical exercise, but also contains vital social and political elements. A radioactive waste disposal system can conveniently be divided into a near-field, geosphere and biosphere (internal components), and some external components that could influence the performance of the disposal system. The biosphere is defined, as that portion of the environment normally inhabited by humans and other living organisms. The transport of radionuclides through the near-field, geosphere and biosphere result in a certain dose to man. In this dissertation, the different pathways through which radioactivity can reach a critical group are explained and demonstrated in a structured framework of a safety assessment, and in particular, the role that the biosphere plays in this assessment. This structured framework was used to illustrate the biosphere part of a disposal system and all the factors that could have an influence on the biosphere. The application, A radiological public hazard assessment at Foskor (Pty) Ltd. was used to demonstrate that the associated activities do not pose a health hazard to humans. The objective was to conduct an integrated radiological public hazard assessment of doses to members of the public via the atmospheric, aquatic and secondary pathways as a result of the mining and mineral processing facilities at Foskor.