Finnish regulator gives positive decision on used fuel repository

Radioactive waste management company Posiva submitted its application, together with related information, to the Ministry of Economic Affairs and Employment on 30 December 2021 for an operating licence for the used fuel encapsulation plant and final disposal facility at Olkiluoto. Posiva is applying for an operating licence for a period from March 2024 to the end of 2070. The encapsulation plant and final disposal facility are intended for the used nuclear fuel generated by TVO's Olkiluoto and Fortum's Loviisa nuclear power plant units.

The government will make the final decision on Posiva's application, but a positive opinion by the Radiation and Nuclear Safety Authority (STUK) is required beforehand. The regulator began its review in May 2022 after concluding Posiva had provided sufficient material. The ministry had requested STUK's opinion on the application by the end of 2023 before extending it, in stages, until the end of June 2026. At the end of June, STUK said it was still finalising the safety assessment and statement.

STUK has now announced that it has published its safety assessment of Posiva's encapsulation and final disposal facility for used nuclear fuel. It says the facility meets the safety requirements set for it in the Nuclear Energy Act and Decree, and, "therefore, there is no obstacle to granting the facility an operating licence with regard to radiation and nuclear safety".

In the safety assessment, STUK has examined both the safety of the encapsulation and final disposal facility during the operation phase and the long-term safety of the final disposal. The long-term safety assessment examines the development of the final disposal system and its environment over very long periods of time - the facility aims for safe storage for at least 100,000, and as many as a million, years - and how the release and transmission of radioactive substances into the environment is prevented and slowed down. In addition, STUK has assessed the readiness of Posiva's organisation to start operation of the encapsulation and final disposal facility.

"This is a significant step in the final disposal of spent nuclear fuel that has been prepared for more than 40 years," said Petteri Tiippana, STUK's Director General. "STUK has been assessing and overseeing the safety of final disposal over several decades. Based on the overall assessment we have now made, we can conclude that the safety requirements for granting the operating permit are met."

STUK has proposed conditions for the operating licence to ensure the continuation of safety assessments and development during the facility's operation. It proposes bringing forward the periodic safety assessment, updating the safety case of long-term safety, and supplementing certain plans related to the final disposal solution.

"As the operation phase begins, we will gain the first experience of how the plans, methodological tests and systems of the world's first geological final disposal facility for spent nuclear fuel work in practice," said Antti Tynkkynen, STUK's Project Manager for the Posiva regulatory control project. "These experiences must be used to learn and further develop the operations and safety, as necessary."

_{A rendering of the underground used fuel repository at Olkiluoto (Image: Posiva)}

At the repository, used fuel will be placed in the bedrock, at a depth of about 430 metres. The disposal system consists of a tightly sealed iron-copper canister, a bentonite buffer enclosing the canister, a tunnel backfilling material made of swellable clay, the seal structures of the tunnels and premises, and the enclosing rock.

Posiva welcomes decision

Posiva President and CEO Ilkka Poikolainen said: "We consider STUK's safety assessment to be a highly significant and positive milestone in the operating license process."

"This is the world's first industrial-scale final disposal facility for spent nuclear fuel," the company noted. "The solution developed by Posiva has attracted worldwide interest. For this reason, the safety assessment is significant not only for Posiva and our owner companies TVO and Fortum, but also for the international nuclear energy community."

A deep geological repository comprises a network of highly-engineered underground vaults and tunnels built to permanently dispose of higher activity radioactive waste so that no harmful levels of radiation ever reach the surface environment. Countries such as Sweden, France, the UK and the USA are also pursuing this option.

The operating licence will be decided by the government on the basis of the materials submitted to it and the authorities' assessments. The Ministry of Economic Affairs and Employment said it "considers that a proposal for the decision on the operating licence could be prepared and submitted to the government in the autumn".

The ministry noted that it has already made decisions by which Posiva has joined the financial provision system for the costs of nuclear waste management under the National Nuclear Waste Management Fund. The ministry has also notified the European Commission of the final disposal project in accordance with Article 37 of the Euratom Treaty, and the Commission has issued its statement on the matter.

"Our ambitious goal is to achieve operational readiness for the start of final disposal by the end of 2026," Poikolainen said.

Posiva said it will continue preparations related to the commissioning of the facility and the measures required by the regulatory process according to plan. Before final disposal operations can begin, testing and commissioning activities remain to be completed at the encapsulation plant and, in particular, in the underground final disposal facilities.

Before the facility is commissioned, STUK will conduct the inspection referred to in section 20 of the Nuclear Energy Act to ensure that all conditions for safe operation are met. Even after receiving a positive decision on the operating licence from the government, Posiva may not start operating the facility until STUK has conducted the inspection.