Siting investigations and, at a later stage, the construction and operation of geological repositories will be supervised by the Swiss Federal Nuclear Safety Inspectorate (ENSI). ENSI is an organ of the Federal Government established under public law (Federal Act of 22nd June 2007); it assumed its activities as successor to HSK on 1st January 2009.
The Federal Council and the licensing authorities can also call on the following expert groups and commissions: the Federal Interagency Working Group on Nuclear Waste Management (AGNEB), the Commission for Nuclear Waste Management (KNE) and the Commission for Nuclear Safety (KNS). These bodies advise the Federal Council and its authorities on issues relating to safety.
Key reports and concepts are also reviewed by foreign experts appointed by international organisations.
Nagra’s work prior to the Act was based on a long-term waste management programme formulated by the waste producers, which was updated periodically. The Nuclear Energy Act that entered into force on 1st February 2005 now calls for the waste management programme to be reviewed by the federal authorities and approved by the Federal Council. The Nuclear Energy Ordinance, which implements the terms of the Act, defines the content of the waste management programme as follows:
– origin, type and volumes of radioactive waste
– required geological repositories and design concepts for the facilities
– allocation of the waste to the geological repositories
– implementation plan
– duration and required capacity of centralised and decentralised interim storage facilities
– financing plan
– information concept.
Nagra submitted the required waste management programme to the federal authorities in autumn 2008.
The Federal Act on Spatial Planning states in Article 13 that the Federal Government has to establish the background that will allow it to fulfil its responsibilities that impact on spatial planning. It has to prepare the required sectoral strategies and sectoral plans and coordinate these with one another. The Nuclear Energy Ordinance calls for the objectives and requirements relating to deep geological disposal to be set out in a federal sectoral plan.
The aim of the sectoral plan for deep geological repositories is to identify sites for repositories in Switzerland as part of an open and transparent process. It defines the procedural steps and criteria for site selection and regulates the regional participation of the public. Safety has the highest priority when selecting sites, but socio-economic and spatial planning aspects also play an important role.
The conceptual part of the sectoral plan was approved by the Federal Council on 2nd April 2008. This signalled the start of the site selection process that will lead to identification of repository sites in a three-stage process extending over around 10 years.
The law requires the waste producers to demonstrate in a feasibility study that all radioactive waste can be disposed of safely on the long term in deep geological repositories. They also have to show that potential sites can be found in Switzerland where repositories can be constructed and operated in a way that fulfils the requirements of the authorities relating to long-term safety. A demonstration of disposal feasibility (Entsorgungsnachweis) is a prerequisite to the granting of general licences for nuclear power plants.
For spent fuel (SF), vitrified high-level waste (HLW) and long-lived intermediate-level waste (ILW), Nagra based its feasibility demonstration on the example of the Opalinus Clay in the Zürcher Weinland region. The reports documenting the project were submitted to the federal authorities in 2002 and, in June 2006, the Federal Council came to the overall conclusion that the feasibility of disposal had been successfully demonstrated for these wastes. This does not represent a siting decision - only a demonstration of the fundamental feasibility of constructing a geological repository in Switzerland, as required by the Nuclear Energy Act. It serves as a basis for the Federal Council in deciding on future procedure in the waste management programme.
The legally required feasibility demonstration for low- and intermediate-level waste was approved by the Federal Council in 1988.
The Nuclear Energy Act calls for radioactive waste to be disposed of in deep geological repositories. A repository is a facility constructed at a depth of several hundred metres in a suitable rock formation. Depending on the type of waste to be emplaced, it consists of disposal tunnels or caverns, a pilot facility for monitoring a representative volume of the waste, a rock laboratory, infrastructure installations and an access tunnel or shafts. A system of multiple safety barriers isolates the waste; the barriers include, for example, suitable packaging of the waste and backfilling of the disposal tunnels. During the construction and operation of the repository, additional structures are required at the surface, where the waste is delivered and prepared for disposal.
A system of staged engineered safety barriers isolates the waste. This includes, for example, suitable packaging of the waste and backfilling of the disposal tunnels. The repository and its accesses have to be capable of being backfilled and sealed after the end of operation. After this, the long-term protection of man and the environment has to be assured by the safety barrier system. Closure of the repository can be a stepwise process, interrupted by monitoring phases.
Safety, i.e. the long-term protection of man and the environment, has highest priority in the disposal of radioactive waste. Containment of the waste has to be assured until such time as the radioactivity has decayed to levels that are not harmful.
It is recognised worldwide that, for high-level and long-lived intermediate-level waste, disposal in geologically stable formations provides safety over the required long time periods. This principle is anchored in the Nuclear Energy Act and also applies in Switzerland to low- and intermediate-level waste. The repositories are underground engineered facilities, typically at a depth of several hundred metres. The host rock has to be stable on the long term, protected from erosion and sufficiently dimensioned to accommodate the foreseen volumes of waste. To ensure long-term isolation of the waste, the rock also has to be water-tight.
Criteria that are secondary to safety are aspects of land use planning, ecology, economics and politics. These will be addressed together with the concerned regions as part of the sectoral plan process.
In a deep repository, the waste is isolated by an impermeable rock layer and a series of staged engineered measures (so-called engineered safety barriers).
For example, high-level waste is mixed with molten glass and the solidified glass blocks are packaged into thick-walled steel disposal containers. These containers are emplaced in tunnels backfilled with bentonite (a natural clay material). The task of these engineered barriers is to contain the waste until such time as most of it has decayed to an acceptable level. Added to this is the geological barrier represented by the host rock that also retains radioactive substances. The host rock also protects the engineered barriers from environmental influences such as erosion and water influx.
In some countries (e.g. Sweden and Finland), geological repositories for low- and intermediate-level waste have already been in operation for some time. In other cases, low-level waste has also been disposed of in near-surface facilities (e.g. in the USA, Spain, France, Japan and England).
As yet, there is no working geological repository for high-level waste. The waste has to be left to cool for several decades before it can be placed in a repository. In Finland, work on a geological repository is already underway, with construction of a rock laboratory; construction of the actual repository will begin in several years. In other countries, planning of facilities is already fairly advanced (e.g. in Sweden and France). In the USA, a geological repository for military long-lived intermediate-level waste (so-called transuranic waste) is already in operation.
Site selection will be conducted within the framework of a sectoral plan for deep geological repositories, as specified by the Nuclear Energy Ordinance and the Spatial Planning Act. The process, which is led by the Federal Government, aims to identify sites for geological repositories using a broadly based, transparent approach. Safety has highest priority, but socio-economic and spatial planning aspects also play an important role.
The search is for sites that fulfil all the protection objectives specified by the regulatory authorities and for which implementation would be reasonable from a spatial planning perspective. The sectoral plan approach allows all the spatial planning implications of constructing repositories to be fully coordinated and ensures early involvement of the cantons, local communities and authorities of neighbouring countries, as well as the public and interested organisations.
The most important aspect of deep geological disposal is the long-term safety of man and the environment and this takes the foreground in all discussions. Risks to health must be ruled out. However, economic and social aspects are also important factors for a potential siting region. Information has to be provided on all possible impacts before, during and after the operation of the repository. Economic and social aspects will be investigated in the second stage of the sectoral plan process.
The Federal Office of Energy and the Opalinus Working Group (representatives of the Zürcher Weinland communities Benken, Marthalen and Trüllikon) commissioned studies on the socio-economic impacts of repositories. The study carried out for the Opalinus Working Group, which was completed in September 2005, showed that there would be a clear financial benefit for the siting region (construction sector, trade, hotel and restaurant industry, workplaces, compensation), but that the image of the region could suffer in terms of the attractiveness of its agricultural products. Systematic surveys at sites with interim storage facilities and repositories both in Switzerland and abroad do not, however, confirm this feared loss of image.
The law requires that the possibility of retrieval must exist. If a decision is made to retrieve waste during emplacement operations or during the monitoring phase prior to closure of the repository, this will be possible with relatively little effort. At a later stage, the effort required will be correspondingly greater as the access to the emplacement tunnels will have to be re-opened. However, retrieval still remains possible.
Retrieval at a later stage may be of interest particularly for spent fuel elements as they contain uranium and plutonium that can be used in energy production.
High-level waste has to be isolated from the human environment for around 200,000 years. After this, the radioactivity will have decayed to a sufficiently low level.
World history has shown that social structures cannot be relied on to remain stable over long timescales. Even just the last hundred years of European history show this clearly. On the other hand, the history of the earth shows us that – in contrast to social structures – rock formations can remain stable over many millions of years and their properties do not change. It could be said that, underground, time stands still, irrespective of what is happening at the surface. If the rock strata are also impermeable, they are capable of containing substances over geological timescales that are far beyond human experience. Compared to such geological timescales, the required containment time for high-level waste of around 200,000 years is relatively short.
Facilities at the surface that rely on maintenance and supervision to ensure their safety are only for interim storage. The Nuclear Energy Act calls for deep geological disposal for the long-term management of all categories of waste. This ensures passively safe, long-term isolation of the waste without any human intervention. It is agreed internationally that a sealed geological repository offers optimum long-term safety.
Containment for around 200,000 years can be assured by emplacing the waste in a repository at a depth of several hundred metres in a very low permeability host rock – for example the Opalinus Clay. The Opalinus Clay, which is around 180 million years old, was formed from clay particles that were deposited on the sea floor. The shells of ammonites living in the sea at that time were embedded in the clay and have been preserved as fossils from the time when the rock was formed until today. The required containment time for radioactive waste is only around 1/1000 of the age of the Opalinus Clay. The clay has a very low permeability and the porewater is practically immobile. The water in the fine pores still contains a component of seawater that was confined when the clay was formed some 180 million years ago.
A deep repository has to be constructed in such a way that the long-term safety of the human environment can be assured, even if the existence of the repository is forgotten.
The question nevertheless arises as to what measures can be used to protect a repository from unintentional intrusion. Locating the facility at a depth of several hundred metres is one approach; the repository would be reachable only with considerable effort and highly sophisticated drilling or tunnelling technology. If, in the distant future, our descendants are in the position to drill to depths of several hundred metres, they should also be capable of detecting the presence of radioactivity and taking the necessary precautionary measures. This is particularly true as radiation is extremely easy to detect.
Measures are nevertheless taken to make such a situation unlikely. The most important one is to avoid areas with potentially exploitable deposits of raw materials (e.g. coal, ore, geothermal) wherever possible in the siting process. After the repository has been closed, the Federal Government will provide for long-term archiving of all key data on the facility. As long as this archive remains intact, the knowledge will be available. There will also be some kind of permanent marking of a deep repository and suitable concepts have long been the subject of discussion in international forums.
Earthquakes are evidence of current movements of the earth's crust. The analysis of earthquakes provides information on active fault zones in underground rock formations, including their spatial extent and direction of movement. For the last 20 years, the network of stations operated by the Swiss Seismological Service and Nagra in Northern Switzerland has been measuring even very weak earthquakes which cannot be sensed by humans or animals.
An understanding of the earthquake situation in a region is important for evaluating the long-term safety of a repository. An analysis of seismic activity allows active fault zones to be located; these are to be avoided when siting the repository.
Worldwide investigations of shafts, tunnels and caverns in earthquake regions show that damage to underground structures is rare and decreases rapidly with depth. Geological repositories at a depth of several hundred metres located at a safe distance from fault zones will therefore not be at risk even from strong quakes.
Fuel elements have to be exchanged after four to five years in the reactor of a nuclear power plant because the content of fissile uranium becomes too low.
Spent nuclear fuel is a mixture of around 4 percent highly active fission products, 95 percent uranium (with around 1 percent fissile uranium-235) and 1 percent plutonium.
Spent fuel has to be managed as high-level waste but there is the possibility for recycling. The fissile material (uranium, plutonium) still contained in the fuel elements can be separated from the fission products in a reprocessing plant and used to manufacture new fuel elements. The fission products are treated as high-level waste.
Up to 2005, around 1000 tonnes or thirty percent of the total amount of spent fuel expected to arise from the five existing Swiss power plants had been sent abroad for reprocessing. The separated waste has to be accepted back by Switzerland. The Nuclear Energy Act, which came into force in February 2005, prohibits the export of spent fuel for reprocessing up to 2016 (moratorium).
After removal from the reactor, the spent fuel elements are stored in pools at the power plant sites for five to ten years to allow cooling. They are then packaged in transport and storage containers and transferred, for example, to the ZWILAG centralised interim storage facility in Würenlingen. Previously the spent fuel was sent abroad for reprocessing. Some of the waste arising from this process is still located abroad and will be transported back to Switzerland.
Low- and intermediate-level waste from the nuclear power plants is processed into a form suitable for disposal, packaged in suitable and then stored either at the power plant sites or at ZWILAG in Würenlingen. Raw waste from medicine, industry and research is packaged into a form suitable for disposal at the Paul Scherrer Institute or at ZWILAG and then stored in the Federal Government's interim storage facility in Würenlingen.
Nagra maintains a centralised inventory of all radioactive waste. There is sufficient interim storage capacity for all waste arising from the operation and decommissioning of the five nuclear power plants until such time as the geological repositories become available. At the end of 2007, the volume of packaged (conditioned) radioactive waste was 5760 cubic metres, including vitrified high-level waste from reprocessing that is stored at ZWILAG. Added to this are spent fuel elements that are stored either at the nuclear power plants or in special containers at ZWILAG. At the end of 2007, 8 containers with high-level waste from reprocessing and 22 containers with spent fuel elements were stored at ZWILAG. A container is around 6 metres high and has a diameter of around 2.5 metres.
For an operating lifetime of 50 years for all the Swiss power plants, the operators expect around 3600 tonnes of spent fuel. Packaged in disposal containers, and taking into account partial reprocessing, this would amount to 7325 cubic metres. This corresponds to the volume of around seven family homes.
For a 50-year operating lifetime of the power plants, Nagra expects a total of around 60,000 cubic metres of low- and intermediate-level waste (including disposal containers). Around half of this is waste arising from the dismantling of the power plants. An additional 33,000 cubic metres of low- and intermediate-level waste will arise from applications in medicine, industry and research.
The total volume of radioactive waste for disposal thus amounts to around 100,000 cubic metres (including disposal containers).
In Switzerland, around 5000 tonnes of radioactive waste (including packaging) arise every year. The waste from decommissioning of the nuclear power plants, which will arise later, has already been factored into this amount. The waste has to be isolated from our living environment for as long as it remains toxic. Toxicity decreases with time due to radioactive decay.
By way of comparison, more than 1,100,000 tonnes of special wastes are produced annually. This includes, for example, acids and leachates, solvents, oils, fly-ash and filter dust, lead batteries, road collection slurries and soil contaminated with mineral oil products or other substances (legacy wastes). A large component of these special wastes can be reduced in terms of weight (e.g. incinerated) or decontaminated (e.g. neutralisation of acids). Somewhat more than one quarter (i.e. around 250,000 tonnes) has to be isolated from the environment for all time. This is carried out in around 50 surface dumping sites in Switzerland and in underground facilities abroad (e.g. decommissioned salt mines).
Financing the management of radioactive waste and spent fuel elements from the nuclear power plants is regulated by the Nuclear Energy Act. The waste producers are obliged by the polluter pays principle to dispose of the waste safely at their own cost. The waste management costs arising today (e.g. for reprocessing, Nagra's investigations, construction of interim storage facilities) are met on an ongoing basis. Decommissioning costs and waste management costs arising after the shutdown of the power plants have to be covered at the time of shutdown and, for this reason, there is a charge of around one Rappen (100 Rappen = 1 Swiss Franc) per kilowatt hour on nuclear electricity today. This money is paid into two funds that are controlled by the authorities; no tax monies are used for this purpose.
The funds are developing according to plan and the accumulated assets at the end of 2006 amounted to around 4.3 billion Swiss Francs. Detailed information on the funds can be found on the websites www.entsorgungsfonds.ch and www.stilllegungsfonds.ch (in German and French).
During the operating lifetime of the nuclear power plants, the arising costs of waste management are paid by the plant operators on an ongoing basis. By the year 2025, these are expected to amount to around 5.6 billion Swiss Francs. Cost studies have shown that the decommissioning and waste management costs of around 8.2 billion Swiss Francs expected in addition to this will be covered by the two funds.
The Federal Government is responsible for waste from medicine, industry and research, for which it operates an interim storage facility in Würenlingen. The Government also contributes around 3 percent to Nagra's costs.
Radioactivity is produced by the spontaneous transformation of an atomic nucleus, which causes small fragments to separate off. There are two main types of nuclear transformation – alpha and beta decay - which produce alpha, beta and gamma radiation. After transformation the nucleus is stable (no longer radioactive) or it decays in further steps until it reaches a stable form.
Natural radioactive substances are present everywhere. New naturally and artificially radioactive substances are produced on earth by high-energy radiation from space, in particle accelerators and in nuclear reactors. Each chemical element has different types of atoms (isotopes) that differ only in terms of the number of neutrons (neutral atomic particles). Most isotopes are radioactive. For example, the element caesium has 37 radioactive atom types and only one stable isotope. The time taken for half of the nuclei of a radioactive isotope to decay is called the half-life and varies from isotope to isotope. It can range from fractions of a second to billions of years.
Protection from radiation can be achieved by restricting the time of exposure, by increasing the distance from the radiation source and by suitable shielding. Reliable monitoring is possible because radiation is easy to measure.
Radioactive substances should not enter the body in unacceptable concentrations via inhalation or ingestion because the effect of radiation is much greater inside the body than it is externally. However, uptake can never be completely prevented as naturally radioactive substances are present in air, drinking water and foodstuffs.
No radiation will reach the earth's surface from a deep geological repository because it is completely absorbed by just a few metres of rock.
The purpose of a geological repository is to effectively isolate radioactive waste and prevent it from being released and contaminating the human environment. The engineered safety barriers prevent or delay the release and transport of radioactive substances into the surrounding rock. The welded steel disposal container foreseen for high-level waste ensures complete containment of the waste for at least 10,000 years in a clay disposal medium.
A deep repository has to ensure the permanent protection of man and the environment. The safety authorities have specified objectives that quantify the required level of protection. At no time shall the release of radionuclides from a sealed repository give rise to individual doses that exceed 0.1 millisieverts per year. Using safety analyses, Nagra has been able to show that these protection objectives can be met thanks to the planned multiple safety barrier system in the repository. All calculated dose values are orders of magnitude below the protection objective of 0.1 millisieverts per year.
Natural radiation, to which we are all exposed, varies regionally, with an average of around 3 millisieverts per year. As a result of medical applications, a person in Switzerland receives an average additional annual dose of 1 millisievert. The amount from medical applications varies widely; X-ray investigations or the use of radionuclides can result in effective doses from a few up to 30 millisieverts.
Radioactive waste contains a mixture of different types of radioactive atoms (isotopes). The composition of the waste is known and the decrease in radioactivity with time can be calculated for the different waste types. It is true for all waste types that toxicity decreases as a result of radioactive decay and, after a certain time, the waste will have an activity that is comparable with that of natural substances. However, the time required for this varies very widely.
In general, it can be said that low- and intermediate-level waste has a radiotoxicity equivalent to that of granite after around 30,000 years. The activity of spent uranium fuel reaches the radiotoxicity of the uranium ore once mined to produce it after around 200,000 years.
Transmutation is the conversion of radionuclides into other nuclides by irradiation. It is initiated by bombarding the material to be transformed with neutrons or protons, which triggers various nuclear physical processes and results in new atomic nuclei.
Transmutation is repeatedly advocated as a means of transforming long-lived radionuclides into shorter-lived nuclides. This is theoretically possible, but cannot be implemented in practice using current technology. The processes involved are presently the subject of extensive research, with the ultimate aim of being able to transform long-lived radioactive wastes into shorter-lived wastes in the future. Even if transmutation technology becomes practicable, geological repositories will still be required for the resulting shorter-lived wastes and for low- and intermediate-level waste that is not suitable for transmutation.
From a geological viewpoint, there are several different host rocks and areas in Switzerland which, together with an appropriate engineered barrier system, would allow construction of a safe geological repository. However, these differ in terms of geological complexity, the quality of the geological barrier and the risk of encountering unexpected difficulties during further investigations.
In the coming years, sites for geological repositories will be identified following the procedure laid down by the Federal Government in the Sectoral Plan for Deep Geological Repositories. At the beginning of the process, and based on safety criteria, Nagra's task was to propose geological siting regions to the Federal Office of Energy (SFOE). Starting with the whole of Switzerland, investigations were focused for geological reasons on the Swiss midlands and northern Switzerland and various rock types and areas were evaluated in these regions. The procedure was based on the following safety-oriented factors: geological-tectonic long-term stability and a suitable host rock with the required depth, thickness and extent.
Based on these considerations, Nagra proposed three siting regions with an Opalinus Clay host rock in 2008. In the following years, the safety authorities of the Federal Government reviewed and approved these siting proposals. In autumn 2011, the Federal Council also confirmed the proposals and incorporated them definitively into the Sectoral Plan process.
In the next stages, Nagra will concretise the details of the repository projects, investigate and compare the potential sites and finally propose those they consider to be most suitable. The public and the authorities in the siting regions can participate in the process. The work is monitored and supported by the safety authorities, the Federal Government and the Cantons. At the end of the process, the Federal Council, Parliament and, in the final instance, the Swiss voters (by optional referendum) will decide whether the selected sites can be licensed. The decision is expected around the year 2020.
In the Sectoral Plan process, Nagra has been able to rely on the results of extensive investigations carried out over the last decades. With a view to providing the legally required demonstration of disposal feasibility for high-level waste, Nagra investigated a wide spectrum of geological options as part of a selection process extending over many years. The stepwise narrowing-down process was supervised by the federal authorities. Based on additional investigations in the Zürcher Weinland region, Nagra submitted the required feasibility demonstration (Entsorgungsnachweis) to the federal authorities at the end of 2002. The demonstration of disposal feasibility was approved by the Federal Council in 2006. This was not a siting decision, only a demonstration of the feasibility in principle of constructing a deep geological repository in Switzerland.
Various operational buildings will be located at the earth's surface. These will be equivalent to an industrial facility with an area of around 200 by 400 metres and will be well integrated into the landscape. The surface facilities are connected to the underground repository by an access tunnel. The repository will also have a vertical shaft. The shaft-related infrastructure at the surface will occupy an area of around 100 by 200 metres.
The underground installations will include emplacement tunnels for high-level waste, disposal drifts for long-lived intermediate-level waste, associated infrastructure, a rock laboratory and a pilot facility. The latter will contain a small representative volume of the emplaced high-level waste and will be used to monitor or control the behaviour of the repository. An area of around 2 x 1 kilometres will be required for the disposal tunnels.
The high-level waste repository will also accommodate spent fuel and long-lived intermediate-level waste.
Various operational buildings will be located at the earth's surface. These will be equivalent to an industrial facility requiring an area of around 150 by 350 metres and will be well integrated into the landscape. The surface facilities are connected to the underground repository by an access tunnel. The repository will also have a vertical shaft. The shaft-related structures at the surface will occupy an area of around 100 by 100 metres.
The underground installations will include disposal caverns for the low- and intermediate-level waste, associated infrastructure, a rock laboratory and a pilot facility. The latter will contain a small representative volume of the emplaced waste and will be used to monitor or control the behaviour of the repository.