Nuclear waste is managed through a combination of temporary storage, recycling, and permanent burial deep underground. The specific approach depends on how radioactive the waste is and how long it stays dangerous. Most of the world’s high-level waste sits in temporary storage right now, waiting for permanent solutions that are only just beginning to come online.
Not All Nuclear Waste Is the Same
Nuclear waste spans a huge range, from lightly contaminated gloves and tools to intensely radioactive spent fuel rods. The international system divides it into six classes, but the three that matter most are low-level, intermediate-level, and high-level waste. Low-level waste makes up the largest volume. It includes things like protective clothing, filters, and equipment from hospitals and power plants. In the U.S., about 1 million cubic feet of commercial low-level waste was shipped for disposal in 2020. This material can be safely buried in shallow landfills with modest shielding.
Intermediate-level waste includes reactor components and chemical residues that need more substantial shielding but don’t generate significant heat. High-level waste is the real challenge. It includes spent fuel pulled from reactor cores and the liquid byproducts of reprocessing that fuel. It’s intensely radioactive, generates heat, and remains dangerous for thousands to hundreds of thousands of years. High-level waste represents a small fraction of the total volume but contains the vast majority of the radioactivity.
Step One: Cooling in Water Pools
When fuel rods come out of a reactor, they’re extremely hot, both thermally and radioactively. They go straight into spent fuel pools: deep, water-filled basins with dedicated cooling systems attached to them. The water absorbs radiation and carries away heat. Even if the cooling system fails, operators have substantial time to restore it before the water would begin to boil, and backup equipment is available even after fires, explosions, or other events that could damage normal systems.
Spent fuel typically sits in these pools for at least several years. Once it has cooled enough, it can be moved to the next stage.
Step Two: Dry Cask Storage
After years in a pool, spent fuel is transferred into dry casks. These are massive steel and concrete containers filled with an inert gas instead of water. They’re passively cooled, meaning they don’t rely on pumps, electricity, or moving parts. They just sit on a concrete pad, radiating heat into the air. This makes them remarkably resilient. They’re designed and licensed for decades of use.
Dry cask storage is where the vast majority of the world’s high-level waste sits right now. It works as a holding pattern, but it’s not a permanent answer. The casks need monitoring, the sites need security, and the waste will outlast any institution currently responsible for it.
The Permanent Solution: Deep Geological Disposal
The international scientific consensus is that high-level waste should ultimately go deep underground, hundreds of meters into stable rock formations. The idea is to isolate it from the surface environment for so long that by the time anything could possibly migrate upward, it would no longer be dangerous.
These repositories rely on a multi-barrier system. The waste itself is sealed inside heavy canisters, often with a copper outer shell over a steel inner container. The canisters are then surrounded by a thick layer of bentonite clay, a material that swells when wet and forms an almost impermeable seal. All of this sits within a carefully chosen host rock. Different countries have selected different rock types based on their geology: crystalline bedrock in Finland and Sweden, clay formations in Belgium and France, salt deposits in Germany and at the U.S. facility in New Mexico. Each layer adds redundancy. If one barrier degrades over millennia, the others continue to contain the waste.
Finland is leading the world on this front. Its ONKALO repository, built into crystalline bedrock on the country’s western coast, is aiming to begin permanent disposal of spent fuel in 2026. It will hold 6,500 tons of uranium in roughly 3,250 sealed canisters. No other country has gotten this far. Sweden is close behind with a similar design.
The U.S. Problem: No Permanent Repository
The United States currently has no permanent disposal facility for spent nuclear fuel or other high-level waste. Congress designated Yucca Mountain in Nevada as the sole site for a repository back in 1987, and the Department of Energy submitted a license application in 2008. But the project was halted under the Obama administration due to sustained opposition from Nevada. The Trump administration requested funding to restart licensing for three consecutive years, but Congress never approved it. Neither the Trump nor Biden administrations sought funding after fiscal year 2020.
The result is that spent fuel remains stored at dozens of reactor sites scattered across the country, with no centralized plan. Two private-sector interim storage facilities have been proposed in New Mexico and Texas, but neither has broken the political deadlock over where this waste ultimately goes.
Recycling: Extracting More Energy From Spent Fuel
Spent fuel isn’t entirely “spent.” About 95 to 96% of it is still uranium, and roughly 1% is plutonium. Both can be extracted and turned back into usable reactor fuel. The standard industrial process for doing this achieves 99.9% separation of uranium and plutonium from the remaining waste.
France is the most prominent example. Its recycling program produces mixed oxide fuel (called MOX), which blends recovered plutonium with uranium. MOX powers about 10% of France’s reactor fleet, generating roughly 10% of the country’s nuclear electricity. The remaining high-level waste after recycling is smaller in volume than the original spent fuel, which makes eventual geological disposal easier.
Recycling isn’t universally adopted, though. The U.S. abandoned commercial reprocessing decades ago, largely over concerns that separated plutonium could be diverted for weapons. Countries weigh energy benefits against proliferation risks differently.
Transmutation: Shrinking the Danger Timeline
Some of the most problematic isotopes in nuclear waste have natural half-lives stretching into the hundreds of thousands of years. Transmutation is a technique that bombards these long-lived isotopes with neutrons inside specialized reactors or particle accelerators, converting them into isotopes that decay far more quickly. Research published in Scientific Reports demonstrated that effective half-lives of several long-lived fission products could be reduced from roughly a million years down to about a hundred years.
This wouldn’t eliminate the need for geological disposal, but it could dramatically shrink the timeframe that a repository needs to remain intact, from hundreds of thousands of years to something closer to a few centuries. The technology works in principle but hasn’t yet been deployed at industrial scale.
Getting Waste There Safely
Transporting nuclear waste is one of the more tightly regulated parts of the process. Shipping casks must pass a series of brutal tests before they’re approved for use. For hypothetical accident conditions, a cask is dropped 30 feet onto an unyielding surface, then dropped 4 feet onto a 6-inch steel pin to simulate puncture. It’s fully engulfed in fire and submerged in 50 feet of water to confirm it stays watertight. For normal transport conditions, it’s tested across a temperature range from negative 40 to 100 degrees Fahrenheit and dropped up to 4 feet to simulate loading mishaps.
Thousands of shipments of spent fuel and high-level waste have been completed worldwide over the past several decades without a release of radioactive material that caused harm to people or the environment.
What It Costs
For conventional light water reactors, the cost of disposing of major components adds roughly $0.68 to $0.90 per megawatt-hour of electricity generated over a 40-year operating lifetime. That’s generally below the $1 per megawatt-hour typically budgeted. For the average electricity customer, waste disposal costs are a small fraction of the total bill. Newer advanced reactor designs may face higher disposal costs because their components can become more intensely radioactive, but these reactors are still in early stages of deployment.