Nuclear waste is disposed of in different locations depending on how radioactive it is. Low-level waste goes to a handful of licensed shallow burial sites. Waste contaminated with plutonium from weapons production is buried 2,150 feet underground in a salt formation in New Mexico. And the most dangerous category, spent fuel from nuclear reactors, currently sits in temporary storage at reactor sites across the world because almost no country has opened a permanent disposal facility for it. Finland is on track to become the first, with operations expected to begin in 2026.
Not All Nuclear Waste Is the Same
About 95% of all radioactive waste by volume is classified as very low-level or low-level. This includes things like contaminated clothing, tools, filters, and medical waste. It’s mildly radioactive and loses most of its hazard within a few hundred years. Another 4% is intermediate-level waste, which requires more robust containment. Less than 1% of all nuclear waste by volume is high-level, but that small fraction contains the vast majority of the total radioactivity.
These categories determine where waste can legally go. Low-level waste can be buried in shallow, engineered trenches near the surface. Intermediate-level waste needs more rigorous packaging and additional barriers to prevent anyone from accidentally digging into it in the future. High-level waste, primarily spent reactor fuel, requires deep underground isolation designed to last thousands of years.
Low-Level Waste: Four Active US Sites
In the United States, four licensed facilities accept commercial low-level radioactive waste:
- EnergySolutions Barnwell Operations in Barnwell, South Carolina
- U.S. Ecology in Richland, Washington
- EnergySolutions Clive Operations in Clive, Utah
- Waste Control Specialists (WCS) near Andrews, Texas
These are all located in Agreement States, meaning the state itself handles licensing oversight rather than the federal Nuclear Regulatory Commission. The waste is typically placed in engineered containers and buried in near-surface disposal cells. Access restrictions and monitoring continue after the sites are filled and closed, but the radioactivity levels are low enough that deep underground burial isn’t necessary.
Weapons Waste: Deep in a New Mexico Salt Bed
The Waste Isolation Pilot Plant, known as WIPP, sits near Carlsbad, New Mexico. It is the only operating deep geological repository in the United States, and its mission is narrow: permanently disposing of transuranic waste generated by nuclear weapons production and related defense research. Transuranic waste contains man-made elements, primarily plutonium, that remain radioactive for tens of thousands of years.
The facility buries this waste 2,150 feet below the surface in an ancient salt formation. Salt was chosen because it is geologically stable, has very little groundwater flow, and slowly creeps inward over time to seal around the waste containers. WIPP does not accept spent reactor fuel or commercial high-level waste. It also cannot receive free-flowing liquids or ignitable materials.
Spent Reactor Fuel: Stuck in Temporary Storage
Spent nuclear fuel is by far the most radioactive waste stream, and right now it has no permanent home in the United States or most other countries. Instead, it sits at or near the reactor sites where it was generated, stored in one of two ways.
When fuel rods are first removed from a reactor, they go into a spent fuel pool. These are deep, water-filled basins with built-in cooling systems. The water absorbs radiation and carries away the intense heat that spent fuel produces through ongoing radioactive decay. Fuel assemblies are spaced apart in racks with neutron-absorbing plates between them to prevent any chain reaction. The pools are designed to hold a large volume of water, making rapid uncovering unlikely even in an emergency.
After cooling in the pool for several years, spent fuel can be transferred to dry cask storage. Each cask is a steel cylinder filled with an inert gas to prevent corrosion, then surrounded by additional steel, concrete, or other shielding material. These casks sit on concrete pads outdoors at reactor sites. They are licensed for up to 40 years, with possible renewals of another 40 years. The NRC has expressed confidence that spent fuel can be safely stored in either pools or casks for at least 60 years beyond the licensed life of any reactor without significant environmental effects.
This is functional, but it was never meant to be the answer. Over 70 reactor sites across the US hold spent fuel, and the amount grows every year.
Yucca Mountain: The US Plan That Stalled
Congress designated Yucca Mountain in Nevada as the site for a permanent high-level waste repository in 1987. Engineers excavated more than 8 kilometers of tunnels roughly 300 meters deep in volcanic rock to test whether the site could isolate spent fuel for up to 10,000 years. But political opposition, particularly from Nevada, stalled the project. Federal funding was cut, and the licensing process was suspended.
As of 2025, the project remains in limbo. The Trump administration has signaled interest in looking at alternative locations rather than reviving Yucca Mountain. The result is a policy stalemate: the US generates thousands of tons of spent fuel with no approved permanent disposal path.
Finland: The World’s First Permanent Repository
Finland is ahead of every other country. Its facility, called ONKALO, is built into bedrock on the island of Olkiluoto and reaches a depth of about 450 meters. The actual disposal tunnels sit between 400 and 430 meters underground, covering an area of two square kilometers. Roughly two million cubic meters of rock were excavated to create the facility.
Posiva, the company operating ONKALO, aims to begin disposing of spent nuclear fuel in 2026, making it the first permanent high-level waste repository to go operational anywhere in the world. The facility includes an above-ground encapsulation plant where spent fuel is sealed into disposal canisters before being lowered into the repository.
How Waste Is Prepared for Permanent Disposal
Before high-level waste goes underground, it needs to be locked into a stable form. For liquid waste from reprocessing, this is done through a process called vitrification: the radioactive material is mixed with powdered glass and melted at around 1,200°C. The molten mixture is poured into large stainless steel canisters, each holding about 1,700 kilograms, which are then welded shut. The glass matrix resists leaching, meaning radioactive elements dissolve out of it extremely slowly.
For spent fuel that hasn’t been reprocessed (the approach used in the US, Finland, and most countries), the ceramic fuel pellets themselves are already a relatively stable solid form. They get sealed into corrosion-resistant canisters designed to last at least 1,000 years, and in some designs much longer.
Deep geological repositories rely on multiple layers of protection rather than any single barrier. The waste form itself resists dissolving. The canister provides physical containment. A buffer material, often a special clay called bentonite, surrounds the canister and swells when wet to seal gaps and slow water movement. Finally, the surrounding rock provides the ultimate barrier, keeping groundwater away and isolating the waste from the surface for geological timescales.
Reprocessing: A Different Approach in France and Russia
Some countries don’t treat all spent fuel as waste. France operates a “closed fuel cycle,” extracting usable uranium and plutonium from spent fuel at its reprocessing plant and mixing them into a new type of fuel called MOX, which can power certain reactors. This reduces the volume of waste that needs permanent disposal, though it doesn’t eliminate it. The leftover high-level liquid waste is vitrified into glass.
France’s system has a significant dependency, though. While it handles most fuel fabrication domestically, it lacks large-scale facilities to re-enrich the recycled uranium and sends much of its stockpile, exceeding 34,000 tons stored near Pierrelatte, to Russia for processing at a Siberian facility. Russia operates the world’s only large commercial-scale plant for this step, giving it substantial leverage in global nuclear fuel supply chains.
The United States abandoned commercial reprocessing in 1977 over nuclear weapons proliferation concerns. The UK shut down its Sellafield reprocessing facility. Japan’s Rokkasho plant has faced decades of delays and limited operations. In practice, no Western nation currently reprocesses spent fuel and re-enriches the recovered uranium at scale.