Deep geological repository

A deep geological repository is a way of storing toxic or radioactive waste within a stable geologic environment (typically 200–1000 m deep).[1] It entails a combination of waste form, waste package, engineered seals and geology that is suited to provide a high level of long-term isolation and containment without future maintenance. A number of mercury, cyanide and arsenic waste repositories are operating worldwide including Canada (Giant Mine) and Germany (potash mines in Herfa-Neurode and Zielitz).[2]

Technicians emplacing transuranic waste at the Waste Isolation Pilot Plant, near Carlsbad, New Mexico

Principles and background

Highly toxic waste that cannot be further recycled must be stored in isolation to avoid contamination of air, ground and underground water. Deep geological repository is a type of long-term storage that isolates waste in geological structures that are expected to be stable for millions of years, with a number of natural and engineered barriers. Natural barriers include a water-impermeable (e.g. clay) and gas-impermeable (e.g. salt) layers of rock above and surrounding the underground storage.[2] Engineered barriers include bentonite clay and cement.[1][3]

The International Panel on Fissile Materials has said:

It is widely accepted that spent nuclear fuel and high-level reprocessing and plutonium wastes require well-designed storage for periods ranging from tens of thousands to a million years, to minimize releases of the contained radioactivity into the environment. Safeguards are also required to ensure that neither plutonium nor highly enriched uranium is diverted to weapon use. There is general agreement that placing spent nuclear fuel in repositories hundreds of meters below the surface would be safer than indefinite storage of spent fuel on the surface.[4]

However, even a storage space hundreds of metres below the ground might not be able to withstand the pressures of one or more future glaciations with thick sheets of ice resting on top of the rock, deforming it and creating internal strains.[5][6] This is being taken into consideration by agencies preparing for long-term waste repositories in Sweden, Finland, Canada and some other countries that would have to expect a renewed ice age.[7] Natural uranium ore deposits serve as proof of concept for stability of radioactive elements in geological formations — Cigar Lake Mine for example is a natural deposit of highly concentrated uranium ore located under sandstone and quartz layer at depth of 450 m that is 1 billion years old with no radioactive leaks to the surface.[8]

Common elements of repositories include the radioactive waste, the containers enclosing the waste, other engineered barriers or seals around the containers, the tunnels housing the containers, and the geologic makeup of the surrounding area.[9]

Swedish KBS-3 capsule for nuclear waste.

The ability of natural geologic barriers to isolate radioactive waste is demonstrated by the natural nuclear fission reactors at Oklo, Gabon. During their long reaction period about 5.4 tonnes of fission products as well as 1.5 tonnes of plutonium together with other transuranic elements were generated in the uranium ore body. This plutonium and the other transuranics remained immobile until the present day, a span of almost 2 billion years.[10] This is quite remarkable in view of the fact that ground water had ready access to the deposits and they were not in a chemically inert form, such as glass.

Despite a long-standing agreement among many experts that geological disposal can be safe, technologically feasible and environmentally sound, a large part of the general public in many countries remains skeptical as result of anti-nuclear campaigns and lack of knowledge.[11] One of the challenges facing the supporters of these efforts is to demonstrate confidently that a repository will contain wastes for so long that any releases that might take place in the future will pose no significant health or environmental risk.

Nuclear reprocessing does not eliminate the need for a repository, but reduces the volume, the long-term radiation hazard, and long-term heat dissipation capacity needed. Reprocessing does not eliminate the political and community challenges to repository siting.[4]

See also: High-level radioactive waste management

Research
Pilot cave of Onkalo at final depth.

Deep geologic disposal has been studied for several decades, including laboratory tests, exploratory boreholes, and the construction and operation of underground research laboratories where large-scale in-situ tests are being conducted.[12] Major underground test facilities are listed below.

Country Facility name Location Geology Depth Status
Belgium HADES Underground Research Facility Mol plastic clay 223 m in operation 1982[12]
Canada AECL Underground Research Laboratory Pinawa granite 420 m 1990–2006[12]
Finland Onkalo Olkiluoto granite 400 m under construction[13]
France Meuse/Haute Marne Underground Research Laboratory Bure claystone 500 m in operation 1999[14]
Japan Horonobe Underground Research Lab Horonobe sedimentary rock 500 m under construction[15]
Japan Mizunami Underground Research Lab Mizunami granite 1000 m under construction[15][16]
South Korea Korea Underground Research Tunnel granite 80 m in operation 2006[17]
Sweden Äspö Hard Rock Laboratory Oskarshamn granite 450 m in operation 1995[12]
Switzerland Grimsel Test Site Grimsel Pass granite 450 m in operation 1984[12]
Switzerland Mont Terri Rock Laboratory Mont Terri claystone 300 m in operation 1996[18]
United States Yucca Mountain nuclear waste repository Nevada tuff, ignimbrite 50 m 1997–2008[12]

Nuclear repository sites
Country Facility Name Location Waste Geology Depth Status
Argentina Sierra del Medio Gastre granite Proposed 1976, stopped 1996[19]
Belgium Hades (High-activity disposal experimental site) high-level waste plastic clay ~225 m under discussion
Canada OPG DGR Ontario 200,000 m3 L&ILW argillaceous limestone 680 m license application 2011[20]
Canada NWMO DGR Ontario spent fuel siting
China under discussion
Finland VLJ Olkiluoto L&ILW tonalite 60–100 m in operation 1992[21]
Finland Loviisa L&ILW granite 120 m in operation 1998[21]
Finland Onkalo Olkiluoto spent fuel granite 400 m in operation[13]
France high-level waste mudstone ~500 m siting[14]
Germany Schacht Asse II Lower Saxony salt dome 750 m closed 1995
Germany Morsleben Saxony-Anhalt 40,000 m3 L&ILW salt dome 630 m closed 1998
Germany Gorleben Lower Saxony high-level waste salt dome proposed, on hold
Germany Schacht Konrad Lower Saxony 303,000 m3 L&ILW sedimentary rock 800 m under construction
Japan Vitrified high-level waste[22] >300 m[22] under discussion[23]
South Korea Wolseong Gyeongju L&ILW 80 m in operation 2015 [24]
South Korea high-level waste siting [25]
Sweden SFR Forsmark 63,000 m3 L&ILW granite 50 m in operation 1988[26]
Sweden Forsmark spent fuel granite 450 m license application 2011[27]
Switzerland high-level waste clay siting
United Kingdom high-level waste under discussion[28]
United States Waste Isolation Pilot Plant New Mexico transuranic waste salt bed 655 m in operation 1999
United States Yucca Mountain Project Nevada 70,000 ton HLW ignimbrite 200–300 m proposed, canceled 2010

The current situation at certain sites
Schematic of a geologic repository under construction at Olkiluoto Nuclear Power Plant site, Finland
Demonstration tunnel in Olkiluoto.
On Feb. 14, 2014, at the Waste Isolation Pilot Plant, radioactive materials leaked from a damaged storage drum (see photo). Analysis of several accidents, by DOE, have shown lack of a "safety culture".[29]

The process of selecting appropriate deep final repositories is now under way in several countries with the first expected to be commissioned some time after 2010.[30]

Australia

There was a proposal for an international high level waste repository in Australia[31] and Russia.[32] However, since the proposal for a global repository in Australia (which has never produced nuclear power, and has one research reactor) was raised, domestic political objections have been loud and sustained, making such a facility in Australia unlikely.

Canada

Giant Mine has been used as deep repository for storage of highly toxic arsenic waste in the form of powder. As of 2020 there is ongoing research to reprocess the waste into a frozen block form which is more chemically stable and prevents water contamination.[33]

Main article: Giant Mine

Finland

The Onkalo site in Finland is the furthest along the road to becoming operational, with waste burial currently scheduled to begin in 2020. Posiva started construction of the site in 2004. The Finnish government issued the company a licence for constructing the final disposal facility on 12 November 2015. As of June 2019 continuous delays mean that Posiva now expects operations to begin in 2023.

Germany

A number of repositories including potash mines in Herfa-Neurode and Zielitz have been already used for years for storage of highly toxic mercury, cyanide and arsenic waste.[2] There is little debate in Germany regarding toxic waste in spite of the fact that unlike nuclear waste it does not lose toxicity with time.

There is a debate about the search for a final repository for radioactive waste, accompanied by protests, especially in the Gorleben village in the Wendland area, which was seen ideal for the final repository until 1990 because of its location in a remote, economically depressed corner of West Germany, next to the closed border to the former East Germany. After reunification, the village is now close to the center of the country, and is currently used for temporary storage of nuclear waste. The pit Asse II is a former salt mine in the mountain range of Asse in Lower Saxony/Germany, that was allegedly used as a research mine since 1965. Between 1967 and 1978 radioactive waste was placed in storage. Research indicated that brine contaminated with radioactive caesium-137, plutonium and strontium was leaking from the mine since 1988 but was not reported until June 2008[34] The repository for radioactive waste Morsleben is a deep geological repository for radioactive waste in the rock salt mine Bartensleben in Morsleben, in Saxony-Anhalt/Germany that was used from 1972–1998. Since 2003 480,000 m3 (630,000 cu yd) of salt-concrete has been pumped into the pit to temporarily stabilize the upper levels.

Sweden

Sweden is working on plans for direct disposal of spent fuel using the KBS-3 technology. However the earliest approvals for construction can be given is 2021 and at the present time the earliest commercial operation could be scheduled to start is 2030.[35]

United Kingdom

The UK has been following the path towards geological disposal since the 2008 Defra White Paper, entitled "Managing Radioactive Waste Safely" (MRWS).[36] Unlike other developed countries the UK has placed the principle of voluntarism ahead of geological suitability. When seeking local council volunteers for stage 1 of the MRWS process, only Allerdale and Copeland in Cumbria were volunteered by their councils. The same area that was previously examined and rejected in the 1990s. Stage 2 which was an initial unsuitability screening process, was carried out by British Geological Survey (BGS) in 2010. This ruled out approximately 25% of the land area based on the presence of certain minerals and aquifers. There remains some controversy about this stage following accusations that the criteria were changed between the draft and final versions of this report, bringing the Solway Plain back into consideration, however the criteria were clearly published in the 2008 Defra White Paper, entitled Managing Radioactive Waste Safely (MRWS) 2 years prior to being applied.

In June 2012, the independent geologist advising the local West Cumbria MRWS Partnership group named three rock volumes that could be potentially suitable for geological disposal of nuclear waste. These are the Mercia Mudstone Group rocks between Silloth, Abbeytown and Westnewton in North Cumbria, and the Ennerdale and Eskdale granites further south which lie within the Lake District National Park.

The decision on whether to proceed to the next stage was due to be taken in January 2013 by a group of seven councillors, forming the Executive of Allerdale and another seven from Copeland. The ten member cabinet of Cumbria County Council had a veto which would prevent the search continuing.

In January 2013, Cumbria county council used its veto power and rejected UK central government proposals to start work on a production reactor nuclear waste repository near the Lake District National Park. "For any host community, there will be a substantial community benefits package and worth hundreds of millions of pounds" said Ed Davey, Energy Secretary, but nonetheless, the local elected administrative and governing body voted 7–3 against research continuing, after hearing evidence from independent geologists that "the fractured strata of the county was impossible to entrust with such dangerous material and a hazard lasting millennia."[37][38]

United States
Yucca Mountain nuclear waste repository and the locations across the U.S. where nuclear waste is stored

The Waste Isolation Pilot Plant (WIPP) in the United States went into service in 1999 by putting the first cubic metres of transuranic radioactive waste[39] in a deep layer of salt near Carlsbad, New Mexico.

In 1978 The U.S. Department of Energy began studying Yucca Mountain, within the secure boundaries of the Nevada Test Site in Nye County, Nevada, to determine whether it would be suitable for a long-term geologic repository for spent nuclear fuel and high-level radioactive waste. This project faced significant opposition and suffered delays due to litigation by The Agency for Nuclear Projects for the State of Nevada (Nuclear Waste Project Office) and others.[40] The Obama Administration rejected use of the site in the 2009 United States Federal Budget proposal, which eliminated all funding except that needed to answer inquiries from the Nuclear Regulatory Commission, "while the Administration devises a new strategy toward nuclear waste disposal."[41]

On March 5, 2009, Energy Secretary Steven Chu told a Senate hearing the Yucca Mountain site is no longer viewed as an option for storing reactor waste.[42]

In June 2018, the Trump administration and some members of Congress again began proposing using Yucca Mountain, with senators from Nevada raising opposition.[43]

On February 6, 2020, U.S. President Donald Trump tweeted about a potential change of policy on plans to use Yucca Mountain in Nevada as a repository for nuclear waste.[44] Trump's previous budgets have included funding for Yucca Mountain but, according to Nuclear Engineering International, two senior administration officials said that the latest spending blueprint will not include any money for licensing the project.[45] On February 7, Energy Secretary Dan Brouillette echoed Trumps sentiment and stated that the US administration may investigate other types of [nuclear] storage, such as interim or temporary sites in other parts of the country.[46]

Though no formal plan had solidified from the federal government, the private sector is moving forward with their own plans. Holtec International submitted a license application to the US Nuclear Regulatory Commission (NRC) for an autonomous consolidated interim storage facility in southeastern New Mexico in March 2017, which the NRC expects to issue its final environmental impact statement on by March 2021. Similarly, Interim Storage Partners is also planning to build and operate a consolidated interim storage facility in Andrews County, Texas, which the NRC plans to complete their review of in May 2021.[45] Meanwhile, other companies have indicated that they are prepared to bid on an anticipated procurement from the DOE to design a facility for interim storage of nuclear waste.[47]

Deep Isolation company proposed a solution involving horizontal storage of radioactive waste canisters in directional boreholes, using technology developed for oil and gas mining. An 18" borehole is directed vertically to the depth of several thousands feet in geologically stable formations, then horizontal waste disposal section is created of similar length where waste canisters are stored and then borehole is sealed.[48]

Main articles: Horizontal drillhole disposal and Deep borehole disposal

See also

References
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