Radioactive waste is the leftover material from nuclear reactions. It comes from power plants, research labs, hospitals, and weapons programs. The waste emits radiation that can damage living cells. How dangerous it is depends on the type and concentration of radioactive isotopes.

Waste is classified by activity level. Low-level waste includes protective clothing, tools, and filters. It decays relatively quickly and is stored in shallow trenches or warehouses. High-level waste includes spent nuclear fuel. It remains dangerous for thousands of years and requires deep geological disposal.

No country has opened a permanent high-level repository for commercial spent fuel, though Finland is close. Most spent fuel sits in cooling pools or dry casks at reactor sites. The technical problem is solvable. The political one is harder. Communities resist hosting repositories. The waste accumulates while the debate continues.

Common categories

• Low-level waste
• Intermediate-level waste
• High-level waste
• Spent nuclear fuel
• Transuranic waste