Sweden has started building a long-term repository for spent nuclear fuel, designed to store highly radioactive waste for 100,000 years. Located in Forsmark, about 150 kilometers north of Stockholm, the facility will feature 60 kilometers of tunnels buried 500 meters deep in 1.9-billion-year-old bedrock. Once completed in the late 2030s, it will have the capacity to hold around 12,000 tons of spent nuclear fuel.