Technischer Bericht NTB 92-02

In Switzerland, the producers of radioactive waste are responsible for its sore management and disposal; in terms of Swiss law this means permanent, safe disposal of the waste in engineered repositories. In order to perform and coordinate the work associated with this responsibility, the power supply utilities. which operate the nuclear power plants. and the Swiss Federal Government (which is responsible for waste from medicine. industry and research) set up the National Cooperative for the Disposal of Radioactive Waste (NAGRA) in 1972. Nagra is responsible for the sore disposal of all categories of radioactive waste and for the research and development work associated therewith. Other aspects of the waste management system, such as conditioning and interim storage of wastes. are carried out by the individual producers or by organisations set up by the producers specifically for these purposes.

A first concept for management or radioactive waste in Switzerland was formulated in 1978 [6]. With this concept, the electricity industry hoped to be in a position to present and justify, to the authorities, the politicians and the public its basic concepts and plans for realising disposal of radioactive waste in Switzerland before detailed legal provisions on the subject came into force. This initial concept was then refined and adapted to take account of technical developments and new information in the field and was first documented in this polished form in Nagra's so-called Interim Waste Management Report [7] of 1983. The concept was then presented in consider­able detail within the context of Project Gewähr 1985 ([2] ,[8]).

Several years have now elapsed since the publication of the Project Gewähr report series in 1985. During this period, namely in 1988, the Federal Government reached its decision on the Project. Since then, and partly based on the content of the governmental decision, some important concepts have been formulated and positive steps taken towards actual realisation of waste repositories. This provides a welcome opportunity to update the management concept for nuclear waste and to bring together the different aspects of the concept in a definitive form.

This report begins by discussing some basic principles of the nuclear waste management concept, the boundary conditions imposed by social considerartions, and technical economic and organisational parameters. The overall concept will then be presented as it applies to the two disposal strategies tor short-Iived wastes and for high-level and long-lived intermediate-Ievel wastes and spent fuel. The current status of project work is discussed and future plans, objectives and time schedules are presented.

In accordance with the views of the international scientific/technical community, the Swiss concept foresees the disposal or radioactive waste in geological formations. The waste will thus be isolated from the human environment by a series of natural and engineered safety barriers. The ultimate demand made of the waste disposal system is that it should ensure long-term safety following definitive closure of the facility. Any steps taken to fulfill additional requirements (e.g. waste monitoring) may not have any adverse effect on long-term safety.

In terms of the Swiss concept, spent fuel elements are reprocessed abroad and the resulting wastes are returned in due course to Switzerland. The option of direct disposal of non-reprocessed fuel elements is, however, being kept open and is taken into consideration in planning the repositories.

Two types of repository are foreseen:

• Repository for short-lived low- and intermediate-level waste, mainly from the operation and dismantling of Swiss nuclear power plants and from medicine, industry and research. The repository will consist of a mined system of horizontally accessible caverns and should be capable of providing the required degree of long-term safety without monitoring or supervision. However, control measures are foreseen and these will remain effective as long as the repository access tunnel is kept open.
• Repository for high-level and long­lived intermediate-Ievel waste from reprocessing of spent fuel abroad and for direct disposal of spent fuel without reprocessing. The repository will be located in a deep geological formation and will consist of a drift system with access via a shaft or ramp. The potential host formations presently being investigated are crystalline rocks and the sediments Opalinus Clay and Lower Freshwater Molasse. In addition to the plan to dispose of these wastes in Switzerland, the option of disposal within the framework of an international project is being kept open.

High-level waste and spent fuel elements will be held in interim storage for a period of approximately 40 years prior to final disposal, in order to allow heat production from the waste to decay away to an acceptable level. Completion or an appropriate centralised interim storage facility is therefore a matter of high priority. Because of this period of interim storage, the repository for these wastes will only be required from the year 2020 at the earliest. Short-Iived wastes, on the other hand, are already in a form suit­able for disposal and construction of a repository for these wastes is thus a matter of some urgency.

The following priorities and time schedules are specified in the concept and realisation plan for 1992:

• Top priority is assigned to construction of centralised interim storage capacity for both wastes from medicine, industry and research (Bundeszwischenlager BZL) and wastes from nuclear energy production (ZWILAG). In view of the fact that reprocessing waste from abroad will begin to return to Switzerland in the mid-1990s, the ZWILAG centralised interim storage facility should commence operations in 1997.
• Top priority is also assigned to constructing the repository for short-lived low- and intermediate-Ievel waste. Provided there is a positive outcome to the site investigations which are currently underway, the site selection and Iicensing procedures should evolve in such a way that the construction can begin before the year 2000.
• Identification of a site for the repository for high-level waste and long­Iived intermediate-Ievel waste and for spent fuel elements (an interim goal of the HLW repository programme) has secondary priority. The regional sediment studies, the comparison between crystalline and sediment options and, finally, the necessary local-scale investigations should be scheduled in such a way that identification of a site will be possible by the year 2000.

In the case of all three main tasks outlined above, achieving objectives and, in particular, keeping to working schedules, is dependent on an improvement in the political and legislative milieu. It is necessary once and for all to clarify the areas of competence of the Federal Government and the Cantons with respect to waste management. Tightening up of the legal licensing procedures is also necessary on all levels. However, what is particularly important is obtaining broadly-based popular support for the waste disposal programme which is, after all, an environmental protection exercise of national significance.