Dealing with nuclear waste has long been a challenging and even contentious issue. From it’s inception in the 1950s the sector has been grappling with the safest and most secure disposal method. Penny Hitchin looks at the current thinking and considers how the world is finally moving towards a consensus.
Every nuclear nation faces the challenge of finding a permanent home for its hazardous nuclear waste – a particular issue for those with a full nuclear power programme. Currently interim storage is used to house spent nuclear fuel and other higher activity nuclear waste, but technical, safety, and security issues mean this is not satisfactory beyond the medium term. Argentina, Belgium, Czech Republic, Finland, Japan, Netherlands, Republic of Korea, Russia, Spain, Sweden, Switzerland and the US are among the countries committed to the principle of deep disposal in suitable geological formations in the long term.
This has been the policy for decades and yet no country has started building a geological repository. Why the delays?
A geological repository must be designed and built to provide secure storage for hundreds of thousands of years into the future. It is a major infrastructure project unlike any other. In many countries the complexity and variety of the issues involved in agreeing a site and public nervousness or outright opposition have made it expedient to kick the can up the road, delaying difficult decisions about where to build. Inter- generational ethics demand that a solution is found, but there are no votes in taking unpopular decisions and many communities fiercely resist becoming the site of a nuclear repository that must endure into eternity.
Constructing a repository means identifying a site with suitable geology and ensuring it has local agreement (not necessarily in this order). This can be a huge hurdle, as has been demonstrated in both the US and the UK where finding a match between appropriate geology and a community prepared to accept the repository has so far proved intractable. However, experience from Scandinavia demonstrates that adopting an unhurried, informative and consultative approach can lead to a community volunteering to host such a facility.
Scandinavia leads the way
Finland is poised to start constructing the world’s first subterranean repository for spent fuel. Building work on the final home for spent nuclear fuel from its existing reactors is expected to start this year.
The process of finding a site started over 30 years ago when, in 1983, the nuclear power operator drew up a list of 101 potential sites for hosting a geological deep repository (geological disposal facility, or GDF). After four years of consultation with the relevant communities five potential sites emerged. Detailed investigations followed which narrowed the field down to three sites. Finland requires a positive decision by the local municipality and a supporting statement from the regulator before government can give the go-ahead to build a repository. Throughout the process the councils of the volunteer sites had the right of veto and to decide whether to support the development of the repository.
By 2001 the Eurajoki Council area, which already hosts two nuclear reactors at Olkiluoto, had decided it would be prepared to host the facility. Parliament subsequently ratified this. The community receives no incentives or compensation directly from the developer for hosting the GDF, but it benefits from a local property tax on nuclear facilities, which is paid at a higher rate than average. Construction is set to start this year and final disposal is scheduled to begin in 2020.
Neighbouring Sweden has also identified a site for its repository. Like Finland, most of its crystalline bedrock provides a suitable environment for a facility. In 1992 SKB, the Swedish Nuclear Fuel and Waste Management Company, contacted 286 local councils explaining the proposition and asking for volunteers. Although a couple of councils were interested, when communities were polled they all opposed any such development. SKB then changed its strategy to focus on communities near existing nuclear sites.
Councils were approached to see if they objected to feasibility studies. This proved fruitful and three areas were prioritised for site investigations. One opted out of the process while two agreed to further investigations. In 2009 Forsmark, in the municipality of Östhammar, was chosen as the preferred site. This is also the site of SKB’s repository for short lived radioactive waste, which is in tunnels 50m below the Baltic Sea where it has been in operation since 1988.
In 2011 applications were submitted to build the spent fuel repository there. As a result construction of the disposal facility for higher activity waste is expected to begin in 2019.
A feat of engineering
The geological repository scenario involves isolation of the nuclear materials in a stable geological formation deep underground. Engineered barriers will be used alongside the already present natural barriers. Repositories will be designed so that no obligation to actively maintain the facility is passed on to future generations. The assumption is that once a repository is filled, it will be permanently sealed – which removes any future option to retrieve the radioactive materials and use them.
The Olkiluoto and Fosmark repositories will use the multi-barrier system developed by SKB. The successive protective barriers consist of copper canisters, bentonite clay and crystalline bedrock. Nuclear fuel assemblies that have been in interim storage will be dried and packed into boron steel canisters and encapsulated in a copper capsule. Remote controls will be used to place each capsule in its own hole in the repository, which will then be backfilled with bentonite clay.
Surrounding waste packages with low permeable clay means that transmission of radioactivity via groundwater flows can be discounted. Other geological formations providing suitable conditions for a repository include clay and salt deposits.
Progress elsewhere in Europe
The first underground rock laboratory researching the suitability of deep clay as a site for geological disposal was established at Mol in Belgium 1984. Hades (High- activity disposal experimental site) is 225m deep in the Boom clay. Hades is a research facility and there are no plans to use the site as a final repository. No disposal site for HLW has been identified in Belgium, although a target date of 2035 has been set for the start of construction.
Andra, France’s radioactive waste disposal agency, is designing a deep geological repository in clays at Bure in eastern France. The Cigéo Project will accommodate vitrified HLW and long lived ILW. The preliminary design has been completed and detailed design work being carried out in 2016-17 will provide data for an application to use the site. If authorisation is granted, construction of the storage facility could start in 2020.
To get to this point, France first ran a site selection process in the 1980s. But this did not involve or consult with local communities and resulted in it being a failure. Following this experience the 1991 Bataille Act on nuclear waste research and development (R&D) established a clear political decision-making process with a 15-year R&D phase before any decision about long-term waste management could be taken. It also set out a process requiring local councils to vote in favour of preliminary surface investigations before being included in a list of volunteering départements.
In 1996 applications for underground rock laboratories (URLs) at three sites were filed. Public hearings followed before the government confirmed that two sites would be investigated: the Bure site and an unidentified granite site. In 2010, following extensive stakeholder engagement, the government approved the location for underground disposal facilities at Bure, which is now Andra’s underground research facility.
Switzerland’s early attempts to find sites for the disposal of LLW and ILW also foundered when the selected cantons rejected proposals. After this experience a new national site selection process was put in place to identify two repositories, one for LLW and ILW and one for HLW and spent fuel. The new process was based on consultation across the country and although it removed the cantons’ right of veto it included them in the decision-making process.
In January 2015, Nagra (the Swiss National Cooperative for the Disposal of Radioactive Waste) selected three geological regions for further investigation for ILW and HLW. The host rock in all three locations is Opalinus Clay. Nagra will make its provisional site selection around 2022. Definitive site selection and the decision of the Federal Council on the general licence is expected by 2029. The repository for low- and intermediate-level waste is expected to start operation around 2050 and the high-level waste repository ten years later.
In Germany, two former salt mines (Asse and Morsleben) have been used for LLW and ILW disposal. In 1977 an extensive national site selection process came up with the salt dome at Gorleben in Lower Saxony as the location for a German national centre for disposal of radioactive wastes.
It is also a possible site for disposal of high-level waste. One and a half billion euros was spent on researching the site between 1979 and to 2000. Government then halted the work, but resumption of excavation was approved following a change of government in 2009. A decision could be made in the next three years with the site potentially available as a final repository from 2025.
Stop-start in the US
Soon after the start of the power industry, in 1957, the US National Academy of Sciences convened a meeting of scientists and engineers to consider the permanent disposition of long lived highly radioactive wastes from commercial nuclear power reactors and nuclear weapons production. They concluded that disposal in mines in deep, ancient salt deposits was practical. The rationale was that as the salt deposits had survived without being dissolved by groundwater, they had been isolated from the near-surface environment for their entire history. Also, as salt is plastic it will slowly fill any voids, eventually encapsulating any waste that is deposited in a mined opening. However a search for suitable salt sites failed.
The search area was then widened to include any sites with atomic energy or defence facilities, regardless of the rock types. In 1987 the remote desert site of Yucca Mountain, adjacent to the Nevada test site, was designated as the US national repository for spent fuel and high-level waste from both civil and military nuclear programmes.
The planned repository would be sited in a layer of volcanic tuff rock lying 300m beneath ground level and 300m above the water table. Waste would be stored in double-shelled metal containers, the outer layer made of a highly corrosion-resistant metal alloy, with the structurally strong inner layer manufactured from stainless steel. The arid geological formation would not be backfilled but left open to some air circulation. Corrosion-resistant titanium drip would shield the waste containers to divert possible future water percolation and provide protection from falling rock or debris.
The project has experienced many delays in the 30 years since it was announced. In 2009 the newly elected Obama administration decided to cancel it altogether. A battle ensued when the regulator’s Atomic Safety and Licensing Board (ASLB) rejected the Department of Energy’s (DOE’s) attempt to withdraw the licence application. In 2013 the federal Appeals Court ordered the regulator to resume its review of the DOE’s application for a licence to construct and operate the Yucca Mountain repository. The future of the project is still unresolved.
Salt of the earth
In parallel, the Waste Isolation Pilot Plant (WIPP) in New Mexico has been operational since 1999, storing US defence transuranic wastes (long lived ILW). At this site natural rock salt is excavated from a salt layer several metres thick, sandwiched between other types of rock 650m below ground level. Steel drums of ILW are placed on pallets and stowed in excavated rooms or caverns. Containment of the radionuclides relies on the water table remaining 300m below the repository, the almost complete absence of water flow in the salt and the long term durability of the engineered barriers. The plastic clay will eventually seal the wastes and isolate them permanently.
Still seeking solutions
Other nuclear nations including Canada, Japan, Korea, Russia, Spain, Taiwan and the UK are committed to deep geological disposal for high level radioactive waste. Canada and the UK have both embarked on a site selection process.
The UK has an extremely varied geology in a small, densely populated island, and finding a suitable and acceptable site is challenging. Potential sites were selected under the ‘decide, announce, defend’ regime of the last century. The 21st century process involves community engagement in an attempt to secure a volunteer host. In the meantime its inventory of spent fuel and exotic legacy materials remain in interim storage, mostly at Sellafield in Cumbria.
In Canada high level waste and spent fuel is the responsibility of the Nuclear Waste Management Organisation (NWMO). It began its site selection process in 2010. The process has nine steps which start by providing information to local communities and allowing them to register their interest and be screened – the community has to take the initiative. Eight areas are being studied and the next steps foresee detailed site examination and selection, with acceptance of the proposal by the community. Regulatory and legal confirmation follows. The final two steps and construction and operation of an underground demonstration facility and then of the final repository.
Among other nuclear countries:
- Russia has a mixed inventory of HLW. It is building an underground laboratory in granite or gneiss in Krasnoyarsk region, which may evolve into repository. Sites on the Kola Peninsula are also under investigation for a final repository.
- China plans to develop an underground rock laboratory and select the site for a repository by 2020. It plans to start disposal in 2050.
- Taiwan envisages a geological repository in granite for HLW operating by 2055. It has specified parameters but no site has been identified.
- Japan established an underground laboratory at Mizunami in granite in 1996. Waste disposal organisation NUMO was set up 2000. Site selection is slated to take place by 2025, with operation commencing a decade later. The current plan is for waste to be retrievable.
There is a broad consensus among nuclear nations that burying high level nuclear waste deep underground is the solution to the problem. Such facilities pose engineering challenges but the main problem lies in getting agreement about where to put such a repository. May 2016 saw an interesting development when South Australia’s Nuclear Fuel Cycle Royal Commission recommended the state investigate an international storage site for ILW and spent fuel.
Hard won experience over the last decades shows engaging with communities in a "no obligation" process can lead to agreement to host a deep geological repository. It is necessarily a slow process but if progress is to be made, experience in Europe and the US shows that there is no alternative.