Field Notes Deep Geological Repository at Olkiluoto, Finland

As the global nuclear fuel cycle becomes increasingly a back-end fuel cycle, an entirely new nuclear facility is being developed to handle the permanent disposal of spent nuclear fuel. Built deep underground, taking decades to plan and many more to construct, the deep geological repository (DGR) is widely considered to be the best, safest option for long-term isolation and containment of radioactive waste minimizing the need for future maintenance. In 2015, Finland became the first country to issue a construction license for a DGR.

Stimson expert Cindy Vestergaard led a group of experts in October 2018 to visit the deep geological repository under construction in Olkiluoto, Finland. These are her field notes:

Olkiluoto is an island in south-western Finland in the municipality of Eurajoki. Population 9,400.

Two nuclear reactors are operating on the island with a third under construction. There is also an interim storage facility for spent nuclear fuel, a repository for low and medium-level waste and a deep geological repository under construction. It is anticipated that the world’s first disposal for spent fuel will begin operations on the island around 2025.

Finland’s two other operating nuclear reactors are located near the town of Loviisa, in southern Finland. Coupled with the two reactors at Olkiluoto, nuclear power generates 30% of Finland’s total electricity.

Fennovoima, Finland’s newest nuclear power company (established in 2007) is in licensing phase for construction of a sixth reactor, at Pyhäjoki, in western Finland.

In Finland, power companies are wholly responsible for the treatment, storage and disposal of their nuclear waste. Underground repositories for low- and intermediate-level waste have been in operation at Olkiluoto (since 1992) and Loviisa (since 1997). For spent nuclear fuel, an amendment to the Nuclear Energy Act in 1994 prohibited the export (and import) of nuclear waste, requiring utilities to focus on domestic solutions for permanent disposal.

In 1995, the two companies owning reactors at Olkiluoto and Loviisa formed, Posiva Oy, a joint venture company to prepare and implement the geological disposal of their spent fuel in Finland.

The Nuclear Energy Act provides for a high level of transparency and public participation from the local to the national level in the decision-making process for any new nuclear facility. Starting with community engagement during an Environmental Impact Assessment, operators have to obtain a ‘Decision in Principle’ from the government (which must be ratified by Parliament) that affirms the project benefits society as a whole before they can apply for a construction license. Prior to the government making its decision, the project must first be endorsed by the Finnish Radiation and Nuclear Safety Authority (STUK) and the municipality at the proposed site.

In January 2000, the Municipality Council of Eurajoki voted 20 for, 7 against, the construction of a final disposal facility at Olkiluoto. A favorable Decision by the government was issued in December 2000 to dispose of a maximum of 4,000 metric tons of uranium in spent fuel from the four operating nuclear power plants in the country at the time. The Parliament ratified the decision in May 2001 by 159 votes to 3.

Two more Decisions were made since: one in January 2002 to expand the disposal facility to include spent fuel (another 2,500 tU) from the third power plant under construction at Olkiluoto, and again in April 2010 to include spent fuel from a fourth reactor planned for the site. Parliament ratified the decision on 1 July 2010 by 159 votes to 35.

In 2004, Posiva began construction of ONKALO, an underground research facility at Olkiluoto. comprising of an access tunnel with a depth of 455 meters, a personnel shaft and two ventilation shafts. ONKALO has been regulated by STUK as a nuclear facility under construction.

Data from ONKALO on the bedrock and testing of installation methods and operational systems was used in preparation for an application for a construction license to build the final disposal facility. Posiva submitted the application in 2012 which was approved in November 2015.

Once the repository and its above-ground encapsulation plant are built, the spent nuclear fuel will be transported in casks, 2 km from Olkiluoto and 350 km from Loviisa, to Posiva. The assemblies will then be verified before encapsulation where they will be packed into a cast-iron insert that is protected by a copper overpack and then placed in the rock for final disposal 420 meters down. A buffer of bentonite clay will be installed around the canisters. Once all canisters have been disposed of, tunnels will be backfilled and access routes from the surface will be permanently sealed.

The operational lifetime of the repository will be around 100 years before permanent closure.

The International Atomic Energy Agency (IAEA) considers spent fuel inherently retrievable in geological disposal – even after enclosure – and therefore its safeguards system will apply in perpetuity (as long as the safeguards agreement remains in place).

Finland and Euratom have been actively engaged in longstanding IAEA discussions on developing generic safeguards approaches for geological repositories. With construction at Olkiluoto, the focus has shifted to identifying national requirements and how international safeguards can be appropriately developed and implemented at the site.

Some of the biggest challenges for safeguards implementation at the repository involve its multigenerational lifespan, constant changes to design and quantities of material, and the determination of what and when information should be provided to the IAEA (and Euratom).

Regulators and operators also need to keep pace with, and adapt to, safeguards-relevant technology. This is particularly applicable when the facility is permanently sealed, and physical verification is no longer possible. Current research shows how technology for laser scanning, geological mapping and monitoring seismic events and changes in groundwater pressure can detect potential safety hazards as well as any undeclared excavations at the site.

Site visits are important for understanding how national, regional and global non-proliferation commitments are integrated into the construction, and eventual operation, of a DGR. The Finnish example underscores how a holistic approach that addresses the technical, political and societal elements of nuclear disposal is an intensive process, but one that operators and communities can navigate. It serves as case study for both newcomers and long-time consumers of nuclear power as they develop nationally-appropriate approaches to the disposal of spent nuclear fuel.

Photo credit: Posiva

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