Onkalo SNF repository passes safety assessment

The "world's first industrial-scale final disposal facility for spent nuclear fuel," planned for the Finnish island of Olkiluoto, has received a favorable safety assessment from the Radiation and Nuclear Safety Authority of Finland (STUK). Ilkka Poikolainen, the president and CEO of Posiva, the waste management company that has been developing the Onkalo facility for decades, characterized the assessment as "a highly significant and positive milestone in the operating license process."

Posiva, which is owned by the energy producers Fortum and Teollisuuden Voima Oyj, hopes to be granted an operating license for Onkalo through 2070. The deep geologic facility is to be used for spent nuclear fuel from Fortum's Loviisa power plant and TVO's Olkiluoto power plant.

Posiva plans to emplace the spent fuel at Onkalo using a system of multiple "complementary engineered and natural barriers," including a tightly sealed iron-copper canister, a bentonite buffer enclosing the canister, and backfilling material made of swellable clay for the system's tunnels.

Long-term evaluation: STUK's assessment, which previously had been delayed, included evaluation of the long-term safety of Onkalo for the surrounding environment, considering a time period of at least 100,000 years and as long as 1 million years. The regulators examined how the repository would prevent radioactivity release and transmission into the environment in addition to how well Posiva is prepared to begin operation of the facility. STUK concluded that "there is no obstacle to granting the facility an operating licence with regard to radiation and nuclear safety" and "the safety requirements for granting the operating permit are met."

Finland's Ministry of Economic Affairs and Employment responded to STUK's positive assessment, saying that "a proposal for the decision on the operating license could be prepared and submitted to the government in the autumn." Poikolainen said, "Our ambitious goal is to achieve operational readiness for the start of final disposal by the end of 2026."

Additional testing and commissioning-related activities must be completed at the disposal site before operations at Onkalo begin. These activities include inspections by STUK to ensure that all conditions for safe operation are met.