Finland has reached a historic milestone in nuclear waste management by issuing the world’s first operating licence for a deep geological repository designed to permanently isolate spent nuclear fuel. The Finnish government granted the permit to Posiva on 22 October, marking the culmination of more than four decades of preparation, according to Spider’s Web – technologie.
The Onkalo facility, located near the Olkiluoto nuclear power plant on Finland’s western coast, consists of a tunnel system carved into bedrock more than 400 metres below ground. The rocks themselves are nearly two billion years old, providing a stable foundation for waste that will remain hazardous for tens of thousands of years.
The licence, valid until the end of 2070, permits Posiva to operate both the encapsulation plant for spent fuel and the underground repository. The facility will accept waste from the Olkiluoto and Loviisa nuclear power stations, with a maximum capacity of 6,500 tonnes of uranium contained in approximately 3,300 special containers.
Multi-barrier system designed for millennia
The storage system relies on several independent safety barriers. Spent fuel will first be placed in containers with an iron core for mechanical strength and a five-centimetre-thick copper shell to resist corrosion. Each container will then be lowered into holes drilled into the rock and surrounded by bentonite, a special clay that swells when it comes into contact with water, filling gaps and restricting water flow.
The final barrier is the bedrock itself, which Finnish scientists have studied for decades to confirm its stability. According to Spider’s Web, the design ensures that even if one barrier eventually loses some of its properties, the remaining layers will continue to limit the release of radioactive substances into the environment.
The complex will eventually include around 40 kilometres of additional storage tunnels at depths reaching up to 455 metres. Finland’s nuclear safety authority, STUK, issued a positive safety assessment in August, which enabled the government to grant the licence. However, Posiva must still complete testing and obtain final approvals before placing any waste underground. The company has not announced a precise start date for disposal operations.
Century-long operation ahead
Once fully operational, up to 60 containers per year will be transported into the underground tunnels. The entire disposal process is expected to last approximately one hundred years, probably until the 2120s. After that, the tunnels will be filled and sealed permanently. This timeline should not be confused with the 2070 expiry date of the current licence, which covers only the initial phase of operations.
Finnish regulations explicitly prohibit accepting nuclear waste from abroad. Onkalo is designed exclusively for domestic spent fuel, meaning other countries must develop their own solutions.
What this means for Poles in Poland
The Finnish breakthrough has direct relevance for Poland, which is preparing to build its first nuclear power station. As Spider’s Web points out, generating electricity from nuclear power creates an obligation to safely manage spent fuel once it has been used in reactors.
Poland already operates a low- and intermediate-level radioactive waste facility in Różan and is searching for a new surface storage site for similar materials. However, these installations are not designed for high-level waste such as spent nuclear fuel. That requires a separate geological solution, similar to what Finland has now licensed.
While Poland continues searching for locations and solutions for future high-level waste storage, the Onkalo project demonstrates that it is possible to obtain regulatory approval for such a facility after decades of research, construction and safety assessments. Polish authorities and energy planners will need to begin addressing the long-term storage question well before the country’s first reactor comes online, as the process from initial studies to operating licence can span multiple generations.
