Roughly 300 km northwest of Finland's capital, Helsinki, is the island of Olkiluoto, home to two nuclear power plants and the potential site for one of the world's first permanent underground high-level nuclear waste repositories.

Onkalo (Finnish for hiding place) is hundreds of meters deep. Research is still under way, but burial of canisters of spent fuel is scheduled to begin around 2020.

A documentary that Danish filmmaker Michael Madsen made about the repository, "Into Eternity," has gained a strong following in Japanese theaters since the atomic crisis began at the Fukushima No. 1 nuclear power plant in Fukushima Prefecture.