Permanent disposal: the core issue
High-level radioactive waste (HLW) will remain dangerous for time spans beyond human comprehension. Depending on the half-life and quantity, it can take hundreds of thousands or even millions of years for a radioactive element to decay to the point where its radiation load no longer poses an unacceptable threat to human health and the environment. No building, facility, technology or social institution created by human communities can realistically guarantee that the storage of this type of waste will remain safe for such long time spans. Even a few hundred years would count as a major success.
That being the case, there is no effective long-term alternative to permanent disposal in deep geological formations, in the Oeko-Institut’s view. Radioactive waste should be entrusted to repositories far underground, in deep geological formations which will remain stable over very long periods of time. These formations exist in Germany. Their geological history has remained largely unchanged for a very long period of time, and they are highly unlikely to be affected by any anticipated future developments, partly because they are sufficiently thick and solid and are located at adequate depth. It seems feasible that radioactive waste stored in these formations would remain isolated from the biosphere for extended periods of time. Using geoscientific techniques, it is possible, in principle, to predict a safe storage period of around one million years for a well-suited site.
So there is no effective long-term alternative to permanent disposal in deep geological formations, in the Oeko-Institut’s view. Radioactive waste should be entrusted to deep geological repositories which will remain stable over very long periods of time. The scientific community has faith in its ability to make a well-founded prediction, based on extensive studies, that the waste can be disposed securely and safely in these formations for at least one million years.
As yet, no site has been selected in Germany for a deep geological repository for high-level radioactive waste from the country’s nuclear power plants. However, with the Repository Site Selection Act (Standortauswahlgesetz), which came into effect in July 2013, Germany’s politicians have addressed the challenge. A comparative scientific analysis will now be carried out to identify a site which offers suitable conditions for final disposal and protects people and the environment from the dangerous effects of high-level radioactive waste.
Oeko-Institut has been working on various aspects of final disposal for many years and has built up extensive expertise in this area. The following text provides an introduction to the topic of final disposal, and looks at the technical requirements and social challenges associated with this issue. Links to selected research projects and further information are provided at the end of the text.
Low-, intermediate- and high-level radioactive waste: what type of repository is appropriate?
Radioactive waste varies in terms of its composition, half-life and activity. It is always a mixture of various radioactive substances (radionuclides). The half-life – in other words, the time required for half of the amount of a radioactive substance to decay into other substances, some of which may also be radioactive – is the metric used to determine a radioactive substance’s longevity. Activity is the number of decays per unit time. The thermal energy released as a result of radioactive decay is known as decay heat. Radioactive waste is classified on the basis of these properties, and the various types of waste require different management approaches.
In Germany, decay heat is the key determinant of the type of final disposal used. Radioactive waste with negligible decay heat is produced during the operation, maintenance and repair of nuclear power plants and other nuclear facilities, and during decommissioning. It is also generated through the use of radionuclides in research, medicine and industry.
For radioactive waste with negligible decay heat, a repository is now being built at Schacht Konrad (Konrad pit) near Salzgitter. The facility at this former iron ore mine is due to come into operation after 2019. Germany also has a permanent disposal site at Morsleben, a former salt mine dating back to the GDR era. Nuclear waste storage in Morsleben continued until 1998 but its closure has been applied for. There is also the failed Asse II nuclear waste storage facility. This too is housed in a former salt mine and is used to store radioactive waste in the 1960s and 1970s, although the waste is to be removed from the site so that it can be decommissioned.
Some types of low-level radioactive waste with high longevity, such as uranium tailings (consisting of depleted uranium, a waste product from uranium enrichment) or waste containing graphite, are not suitable for permanent disposal at Konrad so the issue of their permanent disposal is currently unresolved.
Heat-generating radioactive waste, such as spent fuel elements from nuclear power plants and vitrified fission products resulting from reprocessing of fuel elements, are highly radioactive and generally have very high longevity. Their permanent disposal poses particular challenges, for it is essential to find solutions which offer long-term safety and security. A deep geological repository for these types of nuclear waste does not exist at present in Germany. The search for a suitable site has acquired fresh momentum with the adoption of the Repository Site Selection Act (Standortauswahlgesetz).
Isolated “for eternity”: the final storage challenge
There are no safe and ethically defensible long-term alternatives to the final disposal of high-level radioactive waste in deep geological formations. The extremely long time periods over which radioactive waste must be stored mean that various difficult questions arise: is it indeed feasible, from a technical safety perspective, to make firm predictions for such a long timeframe? Can today’s technology provide adequate protection for future generations? How much scope should future generations have to manage the waste, without facing undue burdens?
As the example of Asse shows, the path towards a permanent disposal solution can be fraught with error. Nonetheless, experts agree that only the underground disposal of high-level radioactive waste can afford the requisite degree of protection over long time spans. In this scenario, geological barriers prevent dangerous radiation from reaching the Earth’s surface, and additional engineered barriers are put in place to close any gaps in protection if the final storage solution itself interrupts the geological barrier. Depending on the scheme’s design, these technological solutions would only last until the rock itself closed the gap.
The selection of a site for a deep geological repository must satisfy carefully defined criteria. For example, the repository must be located in a stable geological zone. It must withstand climatic changes, such as possible ice ages or periods of extreme heat, and offer security from attacks or misuse. It must also provide the maximum possible level of passive safety. In other words, continued safe disposal should not depend on the adoption of active safeguard measures by successive generations.
As individuals and as a society, we cannot guarantee that the waste will be safely stored and monitored for a one-million-year time span. A deep repository takes this into account: when the decision is taken to seal the facility once and for all, long-term controls are deliberately dispensed with. The most important prerequisite is confidence in the functionality of the facility. A monitoring phase, when the waste could still be removed from the facility, could provide additional information of relevance to the decision on sealing, but cannot be an end in itself or a substitute for final disposal.
The search for a site: requirements and legislation
After numerous false starts since the 1970s, negotiations between the German Government, the federal states (Länder) and the political parties on the establishment of a repository for heat-generating nuclear waste culminated in the adoption of the Repository Site Selection Act (Standortauswahlgesetz) by the German Bundestag and the Bundesrat in July 2013. Adopted on the basis of a cross-party political consensus, it draws on the information and expertise built up over many years, and also makes use of experience gained in other countries, notably Finland, Sweden, France and Switzerland.
The Act maps out a step-by-step process based on scientific criteria. In each phase of the process, the options are narrowed down in order to identify the best possible site. Each decision is a matter for federal legislation and therefore has a high degree of binding force.
From a technical perspective, various minimum geoscientific and spatial planning requirements need to be identified. Potential sites must comply with them in order to ensure safe storage. The mountain region where the waste is to be stored in future must be selected and assessed very carefully. To that end, all the options available in Germany, with all their various types of host rock (rock salt, clay shale, possibly granite), should be considered. Each type of host rock has specific merits and disadvantages, and the storage scheme must be designed accordingly. And each potential site has its own specific conditions, all of which must be weighed up on a comparative basis against the defined criteria. In this way, step by step, the best possible solution can be identified.
Indispensable: transparency and public participation
The procedure for the comparison and selection of potential sites must be based on clear criteria and rules. Comprehensive public information and consultation processes have a key role to play. Clear structures, well-defined selection criteria and a frame of reference are indispensable in ensuring that the public understands and can participate in the process.
A dialogue on equal terms is also essential. People must have access to detailed and transparent information about the final storage selection process and the associated developments. This is the only way to ensure that they have a fair chance of being able to form an opinion and make their voices heard. They must also have the opportunity to follow and scrutinise the decisions taken during the process, so that if necessary, they can draw attention to shortcomings and demand compliance with the criteria. This is a prerequisite for public acceptance and recognition of the decisions as democratically legitimate.
The Repository Site Selection Act (Standortauswahlgesetz) envisages a process of public consultation. This should be designed as a learning process which – rather than being based on a pre-set formula – offers flexibility and the scope to incorporate new approaches and developments. In any event, the public should have the opportunity to state its opinion at the outset. Such opinions will be analysed and taken into consideration as the process continues.
The next step is to fill these principles with life!