Finland's Olkiluoto Spent Nuclear Fuel Final Disposal Facility Passes Regulatory Safety Assessment

The Radiation and Nuclear Safety Authority of Finland (STUK) released a safety assessment report on August 4, concluding that Posiva's spent nuclear fuel encapsulation plant and final disposal facility at Olkiluoto, Finland, meets the safety requirements for an operating license. This conclusion brings the project, regarded as the world's first industrial-scale geological final disposal facility for spent nuclear fuel, one step closer to obtaining government approval for operation.

The facility is located on Olkiluoto Island in the municipality of Eurajoki, southwestern Finland, and is designed to dispose of spent nuclear fuel generated by the Olkiluoto nuclear power plant units of Teollisuuden Voima Oyj (TVO) and the Loviisa nuclear power plant units of Fortum. Posiva submitted its operating license application to the Finnish Ministry of Economic Affairs and Employment in December 2021, with a requested license period from March 2024 to the end of 2070. The Finnish government will make its final decision based on the application materials and the regulatory authority's opinion, with the relevant decision proposal expected to be submitted for government consideration this autumn.

In its assessment, STUK reviewed the safety of the encapsulation plant and final disposal facility during the operational phase, as well as the long-term safety of the disposal system. The assessment covered the evolution of the disposal system and its surrounding environment over extremely long timescales, along with measures to prevent and mitigate the release and spread of radioactive materials into the environment. STUK concluded that there are no obstacles to granting an operating license for the facility from a radiation and nuclear safety perspective.

The final disposal approach employs the multi-barrier principle. After prolonged cooling, spent nuclear fuel will be encapsulated in iron-copper canisters, surrounded by a bentonite buffer layer, and isolated through multiple engineered and natural barriers including tunnel backfill material, sealing structures, and host rock. The encapsulated spent fuel will be placed in the ONKALO disposal facility at a depth of approximately 430 meters underground.

STUK also imposed additional conditions on the operating license, requiring continued safety assessments and improvement efforts during facility operation, including conducting periodic safety reviews in advance, updating the long-term safety case, and supplementing certain plans related to the final disposal approach. STUK stated that before the facility is formally commissioned, it will conduct inspections under Finland's Nuclear Energy Act to confirm that all conditions for safe operation are satisfied. Even if the government approves the operating license, Posiva must complete the relevant STUK inspections before commencing operations.

Posiva's President and CEO Ilkka Poikolainen stated that STUK's safety assessment is an important and positive milestone in the operating license approval process. The company will continue to advance facility commissioning preparations and the work required by regulatory procedures, with the goal of achieving operational readiness for final disposal by the end of 2026.