Sweden has begun construction of one of the world's first permanent nuclear waste repositories near the Forsmark power plant (a nuclear facility roughly 140 kilometres north of Stockholm), where 12,000 tonnes of radioactive waste will be sealed in 6,000 copper capsules and buried 500 metres underground in a network of tunnels. The so-called KBS-3 system, developed by the nuclear industry's waste management company SKB, relies on three barriers — copper casing, bentonite clay, and the surrounding bedrock — to contain radioactivity for approximately 100,000 years. The project, which broke ground in 2025 and is expected to be sealed around 2090, has drawn criticism from environmental groups who question the long-term integrity of the copper capsules, with some corrosion experts warning of potential leaks within as little as 100 years.