The OL3, the third and newest reactor of the nuclear power plant Olkiluoto. LEHTIKUVA

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Finland is at the forefront of nuclear safety innovation with the development of new methods for controlling spent nuclear fuel, a crucial step ahead of commissioning the world's first disposal facility in Olkiluoto, Eurajoki. This significant advancement is the result of a collaboration between the Radiation and Nuclear Safety Authority (STUK) in Finland and the Helsinki Institute of Physics.

The meticulous process of safely disposing of spent nuclear fuel involves precise and reliable measurement to ensure that the fuel sealed in disposal canisters is accurately accounted for. This includes verifying the presence of all declared fuel rods. Moreover, it is essential to maintain the measurement results in a secure database, ensuring they remain accessible and comprehensible for future generations.

The research projects GOSSER and GOSSER II, initiated in 2015 and concluding in 2023, have been pivotal in developing these measurement methods and the corresponding database. These projects encompassed the design of specialized measurement equipment, software for analyzing results, and establishing inspection criteria for spent nuclear fuel safeguards in their final disposal.

Two innovative methods have been employed to measure the nuclear fuel: Passive Gamma Emission Tomography (PGET) and Passive Neutrino Albedo Reactivity (PNAR). PGET provides a detailed cross-sectional view of the fuel, clearly depicting individual fuel rods, while PNAR offers additional verification of the nuclear properties of the fuel.

Riina Virta, a researcher at STUK, emphasized the significance of Finland's role in this development, stating, "It is very natural that new methods are being developed specifically in Finland, as we are leading the world in final disposal of spent nuclear fuel. These methods will later be available for other countries to use in their own disposal projects."

The GOSSER projects have produced scientific publications and have been showcased at international conferences. They have also contributed to academic research, including two Master’s theses and a doctoral dissertation.

Posiva Oy, jointly owned by Finnish nuclear power companies Fortum and TVO, is responsible for the safe final disposal of spent fuel from the Loviisa and Olkiluoto nuclear power plants. This initiative by Finland represents a significant step in global nuclear safety, setting a precedent for other nations to follow.

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