Hendrik A. Selling
Ministry of Housing
Spatial Planning and the Environment
The Hague, The Netherlands

The paper describes the development of a national radioactive waste management policy in interaction with principles derived from general waste policies and with criteria related to sustainable development.

The radioactive waste policy in the Netherlands, developed in the early eighties, called for a relatively long interim storage of conditioned radioactive waste in an engineered surface storage facility, followed by disposal in an underground repository in salt formations. Extensive research programmes aiming to demonstrate the suitability of different designs of underground repository in salt were expected to pave the way to the the construction of a disposal facility. However, no formal decision by the government on the disposal stage has been taken yet.

Although in 1993 after completion of the first phase of the research programme it was concluded that disposal of radioactive waste in salt formations could, in principle, be performed safely, the acceptability from an ethical point of view was questioned. This inevitably led to the additional requirement for a disposal facility for radioactive waste, i.e. that it should be designed in such a way that the waste can always be retrieved.

Research programmes now focus on the development of different designs of retrievable repositories. Also host rock materials other than salt are being considered (e.g. clay). Preliminary results have demonstrated the feasibility of retrievable repositories, but on the other hand also the existence of several constraints. Both the requirements concerning retrievability and the associated constraints are discussed in the paper against the background of recent fundamental waste management principles, as developed by international organizations such as the IAEA and OECD/NEA.

In conclusion, the radioactive waste management policy in the Netherlands embraces the concept of retrievability, mainly derived from considerations of sustainable development. Retrieval is possible from the existing surface storage facility and technically feasible from an underground repository during a limited period of time, depending on the host rock material. Thereafter it is not realistic to consider retrieval as a strategic option.

A national policy on radioactive waste management was laid down in a position document¹ presented by the Netherlands' government to parliament in 1984. It envisaged the institution of a single organization responsible for the removal, processing and the storage of all radioactive wastes. As a result in the same year COVRA, the Central Organization for Radioactive Waste, was founded. A decision on the final disposal of the radioactive waste was deferred until it could be reasonably ensured that the safety case for an underground repository would be sufficiently robust. In order to meet the most urgent needs it was also decided that an engineered surface storage facility be constructed with sufficient capacity to accommodate all radioactive wastes being generated in a period of 50 - 100 years. The interim storage facility is now in operation for the low - and medium level radioactive wastes at the COVRA site in the south-west of the country in Borsele.

A procedure to adjust the license amongst others for the construction of a storage building which caters for the accommodation of the high level waste from the power stations and the spent fuel from the research reactors is in its final stage. The compartment for the storage of heat producing high level waste is of a vault type design, in which the waste canisters are placed in a closed system filled with an inert gas to prevent corrosion. The sealed enclosure for the canisters is envisaged to be cooled in its entirety by natural convection of air (see Fig. 1).

Although comprehensive studies have unequivocally demonstrated the suitability of salt domes in the deep underground for the disposal of radioactive waste from a safety point of view, no formal decisions regarding the construction of such a repository have been made.

Research on the permanent underground disposal of radioactive waste has been carried out under the OPLA programme. This programme focused on the examination of the possibility of long-term disposal of radioactive waste in salt formations. Although it is envisaged that an underground disposal facility would accommodate both the high and the low/intermediate level radioactive waste, the safety studies focussed on the integrity of the high level waste galleries. After completion of the phases 1 and 1a of the OPLA programme in 1993 it was concluded that from a safety point of view there are no prohibitive factors which would prevent the deep underground disposal of radioactive waste in salt.

The basic principles of the Netherlands' environmental policy are set out in the National Environmental Protection Plans 1 and 2^2,3. The main focus of this policy is the application of the concept of sustainable development, put forward by the World Commission on Environment and Development, "the Brundtland Commission" in 1987⁴. This basically ethical concept was defined as: satisfying the needs of the present, without compromising the ability of future generations to meet their own needs.

This rather broad principle has been translated for the purposes of (radioactive) waste management into the objective of closing the life cycles of raw materials. This involves the control of substance flows produced by economic activity and to prevent as far as possible, the arisings of (radioactive) waste. Wastes that can not be prevented should be recycled or processed in such a way that it can be used as a secondary raw material in a different process, provided that a sustainable application can be found for it and if dispersal can be prevented throughout its life-cycle. In the cases where recycling or reuse of the waste proves to be impossible its feasibility for the production of energy should be considered. If also that option must be rejected for reasons of sustainability, a safe method of disposal must be sought. The shortage of land in the Netherlands has certainly been instrumental to a policy in which a landfill option for disposal of waste is considered only as a last resort. For underground disposal it is envisaged that the criteria for sustainable development fully apply, i.e. not only should the waste be kept in an environmentally responsible manner, in accordance with the so-called ICM criteria (Isolation, Control, Monitoring) but the entire process of storage and disposal should in principle be reversible. Particularly the latter requirement leads to the inevitable conclusion that non-retrievable storage and disposal methods for highly toxic wastes, including radioactive waste, are not in accordance with the criteria for sustainable development and should, consequently, be rejected. Since 1993, the year in which the suitability of deep underground salt formations for disposal of radioactive waste was discussed in Parliament, the concept of retrievability for radioactive waste and other highly toxic wastes has been the cornerstone in waste management policy in the Netherlands.

Although some countries have in specific situations implemented regulatory requirements with a bearing on certain aspects of waste retrieval from underground facilities, no broad international consensus exists on retrievability of radioactive waste as a policy issue. It is obvious that various countries aim to achieve different objectives with retrieval of radioactive waste. The most prominent objectives formulated so far are outlined below:

1. To enable extraction of valuable constituents from the waste material for future use.
2. To postpone the final decision of closure of the repository until the public and the politicians would have obtained reasonable assurance about the safety performance of such a repository, both at relatively short time frames and at the very long term.
3. To enable access to the waste in abeyance of the availability of improved waste processing technologies or to allow for a possible recycling or reuse of the waste in accordance with the ultimate objective of closing the life cycles of raw materials.
4. To enable removal of the waste from the repository in case of emergencies.
5. To enable the verification of the postulated safety case and to monitor in an early stage any uncontrolled release of radioactive material from the repository.
6. To prolong the experimental stage by setting up an underground laboratory under realistic conditions, with the aim to collect more accurate data on the behaviour of the host rock as a result of the emplacement of the radioactive waste. If necessary the relevant parameters in the model underlying the safety performance assessment of the repository could be adjusted so as to further limit the uncertainties.

In the Netherlands the objectives 2, 3 and 5 seem to represent the predominant reasons for the requirement of retrievability for radioactive and highly toxic wastes.

It is obvious that retrieval of radioactive waste from an underground repository, although conceptually very simple, is from a technical viewpoint a complicated operation which has an impact on the design of the repository. Retrieval is not an objective in itself, but an instrument for decision-makers to ensure that decisions made aim to divide the detriment expressed in potential risks and burdens between generations and within temporary generations on a basis of equity (OECD⁵⁾. In order to be effective, the exact definition of retrievability and the limitations for its application need to be considered. Consequently, it is necessary to clearly establish the constraints for the application of this concept. Below a non-exhaustive list of such constraints is given.

1. Design constraints: if emplacement of the high level, heat-producing radioactive waste is carried out in robust transport/storage casks, convergence of the formation is not expected to cause any damage to the contained waste for several centuries which enables, although at a cost, retrieval by re-mining if future generations would choose to do so. However, the concept of retrieval should not be construed to mean re-mining the disposed waste from a closed and sealed repository. A retrievable repository is to be understood as a repository which is accessible during a certain period after waste emplacement and from which the waste can be easily removed.
2. Time constraints: it is not possible to guarantee the retrievability for the time period usually taken in safety assessments of repositories as necessary to keep the waste isolated from the environment, or the time period after which a gradual release of radionuclides is assumed to occur in such low concentrations as to meet the allowed exposure criteria. In practice the feasibility to keep a geological repository accessible for retrieval purposes is restricted to a maximum of a couple of hundred years, dependent on the type of host rock. While borehole convergence due to plastic deformation of the host rock is rather limited for granite, repositories in salt and clay tend to close around the emplaced waste without any supportive measures of the galleries. Basically in safety studies this plastic behaviour of salt and clay has been advocated as a safety asset because of an enhancement of the containment function of the repository and a facilitation of the heat dissipation to the rock formation. Consequently, the retrieval period should be limited to a realistic length of time. In the Netherlands only salt and clay are available as possible host rock for an underground disposal facility.
3. Safety constraints: the requirement for retrieval of the waste will necessitate some structural adjustments to the design of the repository. However, these adjustments are not allowed to compromise its safety in a sense that the probability of short-term catastrophic events increases. Also retrievability implies that the repository is, in principle, accessible. This may attract the interest of persons and/or organizations which aim to divert fissile materials for non-peaceful purposes. Therefore it should be ensured that full scope safeguards procedures continue to be exercised to the waste repository as long as access is possible.
4. Financial constraints: modifications in the design of a geological repository with the aim to keep the facility open for the period for which retrieval of the waste is being considered, will increase the construction cost of such facility. A preliminary study to the feasibility of creating a retrievable geological repository in rock salt has demonstrated that it is technically possible and financially affordable⁶. Obviously the cost of building a retrievable disposal facility increases progressively with the length of the period of retrieval for which it is designed. After a period of about 50 years the break even point is reached where the cost for the construction of a retrievable repository is estimated to equal the cost of re-mining the waste⁷. This calculation applies for a repository in rock salt or clay, assumes a real return rate of 4 percent and does not take into account the additional expenses for special casks to ensure the long-term integrity of the waste containers under the pressure of the host rock.
5. Waste type constraints: the feasibility studies conducted so far have focussed on designs for retrievable repositories for high level radioactive waste i.e. the vitrified waste from reprocessing or the spent fuel assemblies directly without reprocessing. It is yet to be determined whether the retrieval requirement should also apply to different types of radioactive waste. However, it is highly questionable on rational grounds whether the characteristics of low - and intermediate level waste (for the major part consisting of radionuclides with relatively short half-lifes) would qualify it as a material for which the objectives for retrievability have any significance. In any case, during the public debate to which disposal of radioactive waste will be subjected it should be made transparent that the benefits of retrieval of low - and intermediate level wastes are low while the expenses are outrageously high.

The two international organizations with major programmes in radioactive waste management, the NEA/OECD and the IAEA, have both recently published an interesting document. The NEA has issued a "Collective Opinion" in which its Radioactive Waste Management Committee (RWMC) expresses a consensus position on ethical aspects of the geological disposal of radioactive waste⁵. The main conclusions are:

The IAEA has issued "The Principles of Radioactive Waste Management⁸" which also reflects a consensus among Member States on fundamental rules that should observed in all activities in the subject area. Much emphasis is placed on the protection of the health of the individual, both in the present generations and in future generations, based on the equity principle as outlined earlier. Further the protection of the environment is advocated, where the Member States have the responsibility to apply the same protection standards for the own population as for the population in adjacent countries. Finally it is pointed out that the burdens passed to future generations should be limited. However, retrieval of waste from a repository is specifically mentioned as an activity that should not be denied to future generations if they decide to do so.

No final decisions have been made yet with regard to the disposal of radioactive waste in a geological repository. Currently there is insufficient confidence by the public and consequently by politicians in safety assessments demonstrating the capability of underground repositories in stable formations to isolate radioactive waste and other highly toxic wastes during geological periods of time. In addition the debate is still continuing whether the underground may be used for the disposal of waste, thereby precluding future generations to use the underground primarily for purposes that serve their needs. While further studies are ongoing with the aim to find answers to the outstanding questions and to explore exhaustively possible alternatives for disposal, such as recycling, the construction of an interim storage facility for all radioactive waste is thought to cover the most immediate needs and to provide for a sufficient lengthy period of time to thoroughly consider all available options and prepare a decision.

Conceptually the radioactive waste repository is expected to develop according to the following pattern.

1. The disposal concept can be considered as a process consisting of a series of distinct, consecutive steps, each requiring data collection, consultations with relevant target groups from the society and political debate and endorsement. The process is envisaged to be implemented stepwise, as recommended in the NEA "Collective opinion". The creation of the interim storage facility, operated by COVRA, is the first stage in this process. During this first stage which is conceived to last about 100 years final solutions for waste disposal will be elaborated.
2. Research will be commissioned to encourage sustainable options for waste management. The development of new energy systems, including advanced nuclear power stations whose design is optimized for the prevention of waste will be supported. The possibilities for reducing the quantity of long-lived radionuclides in the waste by conversion techniques such as actinide partitioning and transmutation will be explored exhaustively. Burning of actinides in fast reactors may assist in making the problem of radioactive waste better manageable. Most of the fission products have relatively short half-lives so that the period required for full decay of the radioactivity and hence for isolation of the waste from the biosphere can be substantially reduced. Since it is not expected that waste preventing or recycling strategies will completely phase out any residual, unprocessable waste, geological disposal options in other host rock than salt will be considered. In particular, research will focus on the assessment of the suitability of clay layers for that purpose.
3. Retrieval of the radioactive waste from the interim storage facility is feasible during the whole active and passive operational phase of this facility. The search for the most sustainable options for disposal of the waste will continue and scientific progress may offer possibilities for more advanced waste management methods. However, it should be borne in mind that the vitrified radioactive waste from reprocessing is already conditioned in a form that further treatment is very onerous, if at all feasible. A strategy of retrieval does not seem to have much significance for the existing waste, but more for the waste from any future nuclear reactors.
4. At the end of the interim storage period a political decision has to be made on the final disposal of the generated radioactive waste. Without prejudice on future decisions, the international consensus between the experts from countries in which radioactive waste is being generated is that geological disposal is the most suitable disposal method for the long-lived radioactive waste, which provides the best assurance that the health of the public and the environment will be protected now and in the future. The site selection for an underground disposal facility will be subjected to public scrutiny. During all phases of consultation by the public it should be transparent which category of waste should be disposed of in a retrievable way and for what reason. Also the additional costs for the making a repository retrievable should be calculated and be made subject to public debate.
5. During the full operational phase of the underground repository, which is meant to be the period in which the waste emplacement takes place, the waste can be retrieved, should this be deemed necessary. After termination of the operational phase the repository could either be closed provisionally or definitively. In the former option it is implied that the period of retrievability is extended with a limited, preset term, because it is felt that additional assurance for the safety of future generations is required or for other reasons of substance and that it is expected that such information would become available during the period that access to the waste remains possible. Thereafter, it seems reasonable to close down the repository and to seal it, since a proper sealing is an engineered barrier which has been taken into account as an asset in the safety assessment. Further postponement of the decision to close the repository is generally not be justified, because in case of serious doubt it would have been better to extend the interim storage period in the surface storage facility.

Summarizing, the radioactive waste management policy in the Netherlands embraces the concept of retrievability of particularly the high level waste for reasons mainly derived from the principle of sustainability.

Retrieval is possible from the existing surface storage facility during a long interim storage period of about 100 years, from a future geological repository during the operational phase as well as during a fixed period after emplacement of the total quantity of radioactive waste.

Preliminary studies have shown that retrieval from a repository during a limited period of time is technically possible for the three host rock materials considered (granite, rock salt and clay). Varying adaptations to the design of a non-retrievable repository, dependent on the type of host rock, are necessary to maintain retrievability.

Thereafter it is not realistic to consider retrieval of the waste as a strategic option.

1. Second Chamber, session 1983-1984, 18343, no. 2
2. Second Chamber, session 1988-1989, 21137, nos 1-2.
3. Second Chamber, session 1993-1994, 23560, nos 1-2.
4. Our Common Future, World Commission on Environment and Development, New York, Oxford University Press, 1987.
5. The Environmental and Ethical Basis of Geological Disposal, Nuclear Energy Agency, OECD, Paris, 1995.
6. W.M.G.T. VAN DEN BROEK et al., Retrievability of Radioactive Waste, Delft University of Technology, 1993.
7. J.J. HEIJDRA et al., Retrievability of Radioactive Waste from a deep Underground Disposal Facility, Netherlands Energy Research Foundation, ECN, 1994.
8. The Principles of Radioactive Waste Management, Safety Series No. 111-F, International Atomic Energy Agency, Vienna, 1995

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