High-level waste of time22 July 2004
Germany’s nuclear purge will create a flow of decommissioning waste in the next decade. By Holger Bröskamp, Klaus-Jürgen Brammer and Reinhold Graf
Germany started using nuclear energy in the 1950s. The first nuclear reactors were operated for research purposes only; generating power started in 1962 with a pilot nuclear reactor. In the 1960s and in the beginning of the 1970s political forces demanded a massive expansion of nuclear energy in response to a strong expected increase in the power demand and a concurrent dramatic shortage of raw materials. Utilities were required to turn political considerations into practice and build nuclear power stations. As a result, a total of 21 nuclear power stations were put into operation between 1968 and 1989.
In 1963, the predecessor of the Federal Institute for Geosciences and Natural Resources (Bundesanstalt für Geowissenschaften und Rohstoffe, BGR) issued a recommendation to permanently store the resulting radioactive waste in rock salt formations. In 1973 and 1974 the government started to plan the construction of a national centre for reprocessing, conditioning and disposal of radioactive waste. The final disposal of radioactive waste as an obligation of the state was embodied in law in 1976 by amending the German Atomic Energy Act (Atomgesetz, AtG).
The situation changed when the Social Democratic Party and the Greens came into power in 1998, and declared an intention to withdraw from the use of nuclear energy. The legal basis was created by amending the Atomic Energy Act in 2002 as follows:
• Link the operational lifetime of a plant to a fixed quantity of electricity. From this it can be calculated that the last nuclear power station would be shut down in 2021.
• Outlaw the construction of new nuclear power stations.
Apart from the outline conditions for the operation of plants, the regulations for disposing of waste and fuel assemblies were also changed:
• As of 30 June 2005 the delivery of fuel assemblies for reprocessing will be prohibited.
• Spent fuel assemblies are required to be stored in interim storage facilities to be newly erected at the plant sites instead of storing them in the central interim storage facilities at Ahaus and Gorleben as had been done before.
• The operation of the pilot conditioning plant (Pilotkonditionierungsanlage, PKA) at Gorleben to condition fuel assemblies and make them suitable for final storage, was restricted to the repair of damaged casks.
• Exploration work at the Gorleben final repository project, intended for heat-generating waste, was suspended until conceptual and safety-relevant technical questions will have been clarified but no later than 2010.
• An operating licence has been granted for the Konrad final repository. Legal proceedings have been instituted against this licence.
• Despite the licence for the Konrad final repository (planned for waste with negligible heat generation), the government officially pursues the concept of disposing of all kinds of radioactive waste in a single final repository. The government does not consider it necessary to open the final repository before 2030.
The operators of nuclear power stations are responsible for residual matters resulting from the use of nuclear energy for power generation; to this end, they are required either to reuse materials in a non-polluting manner or dispose of them as specified categories of waste. The waste remains the property of the waste generator until it is received by a final federal repository.
The government is responsible for the final storage as specified by the AtG. The government has delegated this obligation to its subordinate authority, the Bundesamt für Strahlenschutz (BfS), which has pursued the Gorleben and Konrad final repository projects for more than 20 years. Any expenses incurred in this connection are to be borne by the waste producers under the obligation to deliver as per the AtG.
To fulfil its obligations, BfS signed a cooperation contract with the German service company for the construction and operation of waste repositories (Deutsche Gesellschaft zum Bau und Betrieb von Endlagern für Abfallstoffe mbH, DBE) and entrusted DBE with the planning, erection and operation of final federal repositories.
In the area of geoscientific and geo- technical questions regarding the final storage of waste, BfS cooperates with BGR which is affiliated with the Federal Ministry of Economics and Labour (Bundesministerium für Wirtschaft und Arbeit, BMWA).
Licensing of a final repository is the responsibility of the highest competent state authority, which again is subjected to the supervision of the Federal Ministry of the Environment (BMU). Hence the BMU is both the technical and legal supervisor of the BfS as the applicant and the federal supervisor of the competent authority in the area of final waste storage.
Whereas waste is classified by using the categories of low-level, medium-level and high-level radioactive waste on an international scale, Germany differentiates between heat-generating and non-heat-generating waste with regard to the two final repository projects, Konrad and Gorleben (see Figure 1). Non-heat-generating waste is defined as waste causing only a slight increase in temperature (not more than 3˚C) in the surrounding host rock formations. The Konrad mine is intended to be used for the final storage of such waste. In contrast, heat-generating waste causes a markedly higher heat increase in the final repository. Such waste will be finally stored in the salt dome of Gorleben, if the suitability of this repository is established upon completion of the exploration process.
Low-level waste results from the operation, repair and maintenance as well as from the decommissioning of nuclear power stations. Minor quantities are generated when irradiated fuel assemblies are reprocessed and conditioned. As long as a final repository is not yet available, such waste needs to be stored. To this end, the utilities have built central interim storage facilities and capacities at the sites of nuclear power stations.
As of 31 December 2000, BfS reported a volume of conditioned waste amounting to about 67,000m3, of which about 16,000m3 falls to the utilities, whereas 48,000m3 results from other producers of waste, such as large research institutions, medical and industrial facilities. About 3000m3 is collected at regional depots. Whereas the volume of conditioned waste amounts to about 16,000m3, the storage capacities of the utilities in the central interim storage facilities of Gorleben and Mitterteich as well as at the sites of the nuclear power stations amount to about 67,000m3. However, not all waste producers have equal access to the storage capacities.
The annual volume of operating waste generated has continuously decreased as a result of waste minimisation measures. Whereas a volume of about 75m3 was expected from each plant per year in the 1980s, the actual figure today is no higher than 60m3. This tendency continues. As a result of the remaining periods of life agreed between the utilities and the government, the operation of nuclear power stations (including the post-operational phase) will still yield a total operating waste volume of about 20,000m3.
On 11 June 2001 the utilities and the government agreed on the basis of calculations to shut down all currently operated nuclear power stations by about 2021. Hence, the volume of decommissioning waste will clearly increase over the next few years. A waste volume per nuclear power station amounting to about 5000-7000m3 is expected. As the specific procedures for the decommissioning of individual nuclear power stations are not yet clear, the annual volume could be only determined by way of calculations on the basis of simplified model assumptions, leading to an estimated volume of about 4000m3 per year. The total volume of decommissioning waste for all nuclear power stations is assumed to amount to about 115,000m3. Another 10,000m3 must be added, resulting from those nuclear power stations that are already in the process of being dismantled.
Reprocessing waste and other waste
Assuming that the non-HLW from the reprocessing of German fuel assemblies at BNFL is replaced by a mainly activity-equivalent volume of glass canisters, only about 3000m3 of low-level radioactive waste is generated during reprocessing operations at Cogema. About 2000m3 of other low-level radioactive waste must be added, resulting, for instance, from the conditioning of irradiated fuel assemblies in the future for direct final storage.
The volume of current waste and the waste volumes expected to be generated till about 2030 by operating and decommissioning the current nuclear power stations in Germany, will amount to about 170,000m3. The development of these waste volumes as a function of time is depicted in Figure 2. The cumulative waste volume mainly depends on the decommissioning waste. Assuming an annual decommissioning waste volume of about 4000m3, the available interim storage capacities would be exhausted by 2013.
High-level or heat-generating waste
This category mainly includes vitrified fission product solutions, compacted hulls and end pieces as well as structural components from the reprocessing of irradiated fuel assemblies as well as irradiated fuel assemblies intended for direct final storage.
Waste volumes resulting from reprocessing
As provided by the AtG, reprocessing of spent fuel assemblies was the main way for the German utilities to dispose of irradiated fuel assemblies until 1994. To this end, the German utilities signed reprocessing contracts with Cogema and BNFL for a total of about 6900
metric tons of heavy metal (tHM). For these contracts, the obligation was set out to take back any waste generated by reprocessing. Although fuel assembly transports for reprocessing purposes will no longer be permissible after the middle of 2005 as agreed between the utilities and the government on 11 June 2001, it is expected that the return of all reprocessing waste will continue until about 2022.
As expected, the numbers of casks of glass canisters from Cogema and BNFL will amount to about 127 and 39, respectively – a total of 166 casks – of which 39 have already been put into storage. These will be stored in the intermediate cask store at Gorleben. The interim storage duration will depend on the availability of and the acceptance conditions for the final repository. Based on the current conceptual planning for a final repository in Gorleben, storage of about 30 to 40 years will be required for HLW waste from the time of unloading of the fuel assemblies from the reactor until the vitrified waste has been transferred to the final repository.
As currently scheduled, the return of high-pressure compacted hulls and end pieces as well as structural components will commence in 2008. These parts are accommodated in stainless steel canisters with the same dimensions as glass canisters. The expected total number of large casks with compacted sleeves and structural components from the reprocessing contracts with Cogema will amount to 309. As no further decay storage is required, this waste could be immediately transferred to the final repository. If a final repository is not available, the casks will be intermediately stored in the Ahaus cask store.
A total of 840 cask positions are available at Ahaus and Gorleben for waste to be returned for interim storage purposes, of which 81 are presently used or reserved for third parties. As can be seen from Figure 2, these positions are sufficient to accommodate the reprocessing waste to be returned.
Fuel assemblies for direct storage
These fuel assemblies are irradiated assemblies which are not reprocessed. Following interim storage and conditioning (rod consolidation) they are directly transferred to the final repository. Considering the provisions of the agreement dated 11 June 2001, the total quantity for the period until about 2025 is expected to amount to between 9000tHM and 10,000tHM.
The uncompacted fuel assemblies are temporarily stored in casks. After the interim storage facilities at the various locations have been established as provided by the AtG, a sufficient number of interim storage spaces will be available. The operating licences for the interim storage facilities, as recently granted by the BfS, are limited to a period of 40 years.
AVAILABILITY OF FINAL REPOSITORIES
The Table on the opposite page depicts the project flows for the Konrad and Gorleben final repositories as scheduled in 1998 and today. Whereas project changes in the past were mainly influenced by practical considerations, the massive shiftings of target dates since 1998 are due to politics. The current situation of both final repositories has been defined by the agreement signed between the government and the utilities on 11 June 2001 as well as by the efforts of the BMU to implement a procedure for identifying a new site. From the utilities’ point of view this approach violates the word and the spirit of the above agreement, and is even unnecessary in material terms.
Under a post-operational usage scheme for the former iron ore mine, Konrad, the National Research Centre for Environment and Health (Gesellschaft für Strahlen und Umweltforschung mbH, GSF) on behalf of the government started first examinations in 1975 to establish the suitability of the mine as a final repository for low-level and medium-level radioactive waste. These suitability examinations completed, an application for initiating a plan approval procedure was filed in 1982.
The plan approval decision was made in May 2002. On 17 July 2002 the application for the immediate enforcement of the decision was withdrawn by the applicant BfS, with the intention of bringing the legal proceedings to an end before commencing revamping and conversion activities. The utilities expect that the construction of the final repository will be completed by the government as soon as all legal disputes are resolved and the required legal security is established. After a preparatory period lasting about two to three years, the conversion activities – the construction of the necessary buildings above ground as well as the drifting and lining of the storage spaces – will take about four to five years. Therefore, storage operations could commence between roughly 2010 and 2013, depending on the duration of the legal proceedings.
Following an intense site selection process by the government and the state of Lower Saxony, the state government of Lower Saxony declared Gorleben to be the location of a national centre for reprocessing, conditioning and disposal of radioactive waste in 1977. During the preceding three-stage selection procedure, more than 140 sites had been reviewed. Exploration of the site started in 1979 and was interrupted for a scheduled period of about three, but no longer than ten years, on 1 October 2000 to clarify conceptual and safety-relevant technical matters for the final storage of waste.
The present government is of the opinion that the geological findings made to date are not contradictory to the suitability of the salt dome of Gorleben. As declared in the statement of the government with regard to Gorleben, “the findings to date as to a tight rock formation and, hence, a barrier function of the salt could be positively confirmed.” The government agreed to secure the site, ie not permit third parties to use it, and announce an intention to resolve issues raised during the moratorium in an expeditious manner until the end of 2004 at the latest.
As the utilities do not expect that the clarification of such issues will question the suitability of Gorleben, exploration will probably be continued from 2005 in compliance with the agreement. Consequently, Gorleben could be available as a final repository from 2025.
Presently, the BMU is considering performing a new site selection, and subsequent exploration of several sites. As the plan approval procedure identified the Konrad site and the Gorleben salt dome as two promising sites for a final repository, any costs incurred during a new site selection procedure are not deemed necessary expenses under Endlager VlV (the environmental law concerning payment for final disposal). Therefore, the waste owners are not obliged to bear such costs. However, the implementation of a new site selection procedure would render the opening of a final repository by 2030 unrealistic. Most likely, the start-up of a final repository will be delayed until 2050; despite any statement to the contrary, this would mean a shift of the responsibility to future generations.
Non-heat-generating waste is already conditioned in a manner suitable for final storage in compliance with the specifications issued by the BfS and according to the preliminary acceptance conditions of the Konrad final repository.
Based on calculations and a generalised approach, the available interim storage capacities for operating and decommissioning waste will be sufficient until 2013, ie the time when the Konrad final repository is expected to be put into operation.
Starting the operation of the Konrad final repository in 2013 will render the construction of additional interim storage capacities unnecessary as all waste still generated and already existing, could be stored in that shaft until 2030.
On a case-by-case basis, the provision of additional interim storage capacities will become necessary much earlier. This holds true for the large volumes of decommissioning waste, in particular waste from dismantling projects commenced before a final repository is available.
In case that, as scheduled by the BMU, a single final repository will not be put into operation until after 2030, the total waste volume of about 170,000m3 will need to be safely stored in an interim facility. This scenario would require around 100,000m3 of additional interim storage capacity.
For heat-generating waste the BMU aims to make a final repository available by 2030. From a technical view, the opening of a final repository for heat-generating waste in Gorleben by 2025 is still realistic if the expeditious completion of exploration activities proves the suitability of the salt dome.
The compacted waste returned by 2022 from the reprocessing cycle should be suitable for final storage without any additional decay storage. It is intended to store this waste in boreholes. A combination of cold canisters with compacted waste and hot glass canisters would be advantageous.
The current reference concept for the final storage of irradiated fuel assemblies is the so-called Pollux concept. According to this concept, the time of transferring the waste to the repository depends on the thermal load of the fuel assemblies and the permissible thermal output in the final repository.
Presently, a new concept is being developed to optimise final storage. This concept will simplify handling processes in the final repository, and eventually facilitate earlier storage due to a lower thermal output per package.
Presently, the duration of storage and, hence, the necessary period for keeping the final repository open are assumed to be mainly determined by the capacity of the conditioning plant. The licensed throughput is 35tHM per year whereas the maximum technical throughput is about 450tHM per year. Therefore, conditioning operations facilitating the final storage should be started as early as possible to ensure a short operating period of the final repository. However, this requires the storage conditions be finalised as early as possible.
A period of about ten years is expected to be necessary for developing an optimum concept and performing the relevant tests to verify the concept. As the conceptual development depends on the local conditions of the final repository to a major extent, the final storage conditions must be finalised as soon as possible to facilitate optimisation of the final storage.
Another aspect involves the limitation of the operating licence for the interim storage facilities at the various locations to a period of 40 years. To be able to remove all fuel assemblies from the interim storage facilities at the various locations in due course as soon as the operating licences elapse, the transfer, conditioning and final storage would have to be started as early as in about 2020. Proceeding from the assumption that the development and testing of an optimum storage concept takes about ten years, the outline conditions (final repository requirements) would have to be finalised by 2013.
It is hardly possible even now to reach this deadline. Even if the exploration activities are resumed in 2005 and completed by 2010, the evaluation of the exploration findings would hardly be available before 2012 and a plan approval decision hardly be issued before 2020. In addition, the suitability of the Gorleben location would have to be confirmed and the project be continued without being delayed by performing exploration activities at other locations.
The Konrad and Gorleben final repository projects need to be implemented as soon as possible to avoid both long-term interim storage to the detriment of technical safety and the necessity to build new substantial interim storage capacities for low-level radioactive waste as well as to ensure also the expeditious disposal of high-level radioactive waste.
Holger Bröskamp, Klaus-Jürgen Brammer and Reinhold Graf, GNS, Gesellschaft für Nuklear-Service mbH, Hollestr. 7A, 45127 Essen, GermanyTablesFinal disposal sites availability dates