Application of the International Commission on Radiological Protection System to the Disposal of Long-Lived Solid Radioactive Waste
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T-18-1, P-5-334 Application of the International Commission on Radiological Protection System to the disposal of long-lived solid radioactive waste Annie SUGIER Institut de Protection et de Sûreté Nucléaire, BP n° 6, 92265 Fontenay-aux-Roses Cedex, France 1. INTRODUCTION The objective of waste disposal is to protect current and future generations. The International Commission on Radiological Protection is a reference in the field of radiological protection in the European Union, as ICRP recommendations constitute the basis for the regulatory provisions of the European Union in this domain. This is why, in the context of the conference on "radioactive waste management strategies and issues" it appeared important to describe the new ICRP policy concerning radioactive waste disposal. ICRP provides recommendations and guidance on specific topics ranging from the protection of workers to potential exposures, exposures in accident situations etc. However, the strength and coherence of the Commission’s System of Protection lies in its ability to cover a wide range of circumstances in a consistent way. The basic elements of ICRP policy are defined in its general recommendations published in 1990 (ICRP 60). As concerns the disposal of radioactive waste, the ICRP published a document entitled "Radiation Protection Principles for the Disposal of Solid Radioactive Waste" in 1985. Since then, in-depth consultations have been conducted in different national and international organisations on issues such as the ethical implications of the protection of future generations, the search for indicators of environmental protection, the principles of sustainable development, the precautionary principle and the review of assessment methods and ways of building confidence. It is in this context that in 1998 ICRP issued Publication 77 entitled "Radiological Protection Policy for the Disposal of Radioactive Waste". This report had been prepared by a Task Group of the Main Commission itself. The report reaffirms the Commission’s current policy of radiological protection, in particular its policy on public exposure, and aims to clarify the practical application of that policy to the disposal of radioactive waste. In September 1999, two reports were adopted by the Main Commission and should be published in 2000: • Protection of Public in Situations of Prolonged Radiation Exposure (Task Group chaired by Abel Gonzalez), • Radiation Protection Recommendations as Applied to the Disposal of Long-Lived Solid Radioactive Waste (Task Group chaired by Annie Sugier). This communication deals mainly with this second report. However, it emphasises, as a starting point, the conceptual framework of the Commission’s system of protection. 2. CONCEPTUAL FRAMEWORK The primary aim of ICRP policy is to provide an appropriate standard of protection for man without limiting the beneficial practices giving rise to radiation exposure. Two kinds of effect have to be taken into account: deterministic effects which can be avoided by restricting the doses to individuals below well-known thresholds, and stochastic effects which cannot be completely avoided because it has not been demonstrated that there are any thresholds for them. 1 T-18-1, P-5-334 ICRP considers that some residual risk is acceptable as long as it has been limited by all reasonable means. The system of Radiological Protection divides exposure situations into practices and interventions. Practices are human activities that are undertaken as a matter of choice despite the increase in exposure. This increase can be avoided by refraining from undertaking the practice or controlled by taking precautions. Sometimes, however, exposures result from situations that already exist. If any action is required to reduce exposures or to remove sources, the action is called intervention. It is clear that the principles of protection for practices apply to the disposal of radioactive waste, as long as it is a planned operation with the source under control. The conceptual framework for practices developed by ICRP is based on three principles, namely justification of a practice on the grounds that it produces sufficient benefit to offset the radiation detriment that it may cause; optimisation of the protection, in relation to any particular source within a practice, economic and social factors being taken into account; and finally limitation of the exposure to which an individual may be subjected from the combination of all the relevant practices. In Publication 60, the Commission distinguishes between "normal exposure" and "potential exposure". "Normal exposures" are those that are virtually certain to occur and which have a magnitude which is predictable, albeit with some uncertainty. The term "potential exposures" refers to situations where there is a potential for exposure but no certainty that it will occur, i.e. the type of situations of concern in the long term following closure of a solid radioactive waste disposal facility. The principles and objectives of the 1990 Recommendations, as they relate to potential exposures, are developed in Publication 64, "Protection from Potential Exposure: a Conceptual Framework" (ICRP, 1993), which is intended to provide a basis for the preparation of more detailed guidance relating to specific practices, including radioactive waste disposal. In Publication 60, the policy is set out in general terms, covering all sources of radiation. ICRP 77 deals more specifically with the specification and application of the Commission’s protection policy in the context of the disposal of radioactive waste. ICRP 77 is particularly important as it clarifies the terminology and existing strategies in the field of waste disposal. In the context of the Commission’s recommendations, waste is any material that will be or has been discarded as being of no further use. Waste includes liquid and gaseous effluents as well as solid materials such as process residues. Waste storage is the temporary retention of waste. Waste disposal is the discarding of waste with no intention of retrieval. The term disposal covers the discharge of effluents and solid waste disposal. Waste disposal strategies can be divided into two conceptual approaches: Dilute and Disperse or Concentrate and Retain (see Fig. 1). Early or deferred releases of radionuclides to the environment would inevitably result from either of these strategies and therefore an objective of no release in not feasible. Both strategies are in common use and are not mutually exclusive. Where there is a choice, the balance between the two strategies is a radiological protection issue involving, inter alia, consideration of the decay of radionuclides during the period of containment and of the associated risk of elevated exposures from disruptive events which is an inescapable consequence of the decision to concentrate waste in a disposal facility rather than diluting or dispersing it. The recommendations of the ICRP on long-lived solid waste disposal deal with the radiological protection of members of the public using the concentrate and retain strategy. It covers options including shallow land burial and deep geological disposal. The recommendations made in this report apply to new disposal facilities where there is the opportunity for their implementation during the site selection, design, construction and operation phases; they should also be taken into account in justification decisions involving practices generating waste. The clarifications provided by ICRP Publication 77 concerning the application of the radiological protection system consist in emphasising that the main issue is the exposure of members of the public. They 2 T-18-1, P-5-334 Publication also identifies the principles that are truly useful as well as the quantities that should preferably be used. The principle of justification applies to practices as a whole. It is wrong to regard disposal of waste as a free-standing practice, needing its own justification. Waste management and disposal operations should therefore be included in the assessment of the justification of the practice generating the waste. The Commission’s dose limit applies to the sum of doses from specified practices, but not to the sum of doses from all sources of exposure. Although the Commission continues to recommend dose limits, it recognises that dose Figure 1 IPSN WASTE PRODUCTION SYSTEM AND MANAGEMENT OPTIONS Environment NUCLEAR FUEL CYCLE IMMEDIATE Dilute/ te Disposal RELEASES Operations s Disperse a w Atmospheric al Liquid pos s i D Concentrate retain REPOSITORY Dilution/ DELAYED LLW/ILW surface Dispersion HLW underground RELEASES 99-IPSN/169201/GG limits for public exposure are rarely limiting in practice. Furthermore, it considers that the application of dose limits to waste disposal has intrinsic difficulties and that control of public exposure through a process of constrained optimisation will obviate the direct use of the public exposure dose limits in the control of radioactive waste disposal. Thus, the principal means of achieving protection of the public is through a process of constrained optimisation, taking account of the Commission’s recommended upper value for the dose constraint of 0.3 mSv per year or its risk equivalent. The dose constraint is an important component of the optimisation of protection. The term is used by the Commission to mean a source-related individual dose used exclusively in the optimisation of protection to exclude from further consideration any protection options that would cause