A typical nuclear power plant produces roughly 20 to 30 metric tons of spent fuel per year. That’s a surprisingly small volume for a facility generating enough electricity to power hundreds of thousands of homes. All the spent nuclear fuel ever produced by commercial reactors in the United States would fit on a single football field, stacked about 10 yards deep.
But “nuclear waste” covers more than just spent fuel. Understanding the different types, what they contain, and how they’re managed puts those numbers in perspective.
How Much Spent Fuel One Reactor Produces
A standard 1,000-megawatt reactor, the most common size in the U.S. fleet, discharges about 20 to 30 metric tons of spent fuel assemblies each year. These are bundled metal rods, each about 4 meters long, that spent several years inside the reactor core. Despite the weight, the physical volume is compact. A single year’s worth of spent fuel from one reactor would fit in the back of a large pickup truck.
This tiny footprint is one of nuclear energy’s defining features. A coal plant of similar capacity produces millions of tons of ash and carbon dioxide annually. A nuclear plant’s solid waste output is smaller by a factor of roughly a million in mass, though of course the waste itself is far more hazardous and requires careful long-term management.
What’s Actually Inside Spent Fuel
Spent fuel is not entirely “waste” in the traditional sense. According to the U.S. Nuclear Waste Technical Review Board, a typical spent fuel assembly is about 93.4% uranium that never fissioned, still containing some energy potential. Another 5.2% is fission products, the atoms left behind when uranium splits. About 1.2% is plutonium, and the remaining 0.2% consists of other heavy elements like neptunium, americium, and curium.
That 5.2% of fission products is where most of the intense radioactivity and heat come from. Some of these isotopes decay within days. Others remain dangerously radioactive for thousands of years. The plutonium and other heavy elements add to the long-term hazard, since some take tens of thousands of years to decay to safe levels. This is why spent fuel requires isolation from the environment for such extraordinary timescales.
Types of Nuclear Waste by Radioactivity
Not all nuclear waste is spent fuel. Power plants also generate contaminated clothing, tools, filters, resins, and reactor components. The International Atomic Energy Agency classifies radioactive waste into several categories, and the breakdown reveals something counterintuitive: the vast majority of nuclear waste by volume is only mildly radioactive.
About 95% of all radioactive waste worldwide is classified as very low level or low level. This includes things like contaminated work gloves, plastic sheeting, and slightly activated metals. It requires minimal shielding and can often be disposed of in near-surface facilities. Another 4% is intermediate-level waste, which includes reactor components and chemical sludges that need more robust containment. Less than 1% of the total volume is high-level waste, primarily spent fuel and the byproducts of reprocessing it.
Here’s the catch: that tiny fraction of high-level waste contains the overwhelming majority of the total radioactivity. So while 95% of the volume is relatively easy to handle, the small remainder demands the most engineering, the deepest burial, and the longest institutional oversight.
Where the Waste Goes After Removal
When spent fuel assemblies are pulled from a reactor, they’re immediately placed in a spent fuel pool, a deep basin of water next to the reactor building. The water serves two purposes: it shields workers from radiation and absorbs the intense heat that fresh spent fuel generates. Fuel typically stays in the pool for at least five years, though practical constraints like cask availability and regulatory approvals often extend that timeline.
After sufficient cooling, spent fuel can be transferred to dry cask storage. These are massive steel and concrete cylinders, each holding about 10 to 15 tons of fuel, that sit on concrete pads at the reactor site. They require no active cooling or electricity, relying instead on passive air circulation. According to Sandia National Laboratories, smaller casks can accept fuel within five years of discharge, but fully loading very large casks with high-burnup fuel (fuel that was used more intensively in the reactor) may require decades of pool cooling first.
In the United States, there is currently no permanent disposal site for high-level waste. The proposed Yucca Mountain repository in Nevada has been politically stalled for decades. As a result, spent fuel sits in pools and dry casks at more than 70 reactor sites across the country. Finland is the first nation to build and begin operating a deep geological repository, tunneled into bedrock roughly 400 meters underground.
Putting the Volume in Perspective
After more than six decades of commercial nuclear power in the United States, the total inventory of spent fuel is around 90,000 metric tons. The Nuclear Energy Institute notes that this entire stockpile, if consolidated, would fill one football field to a depth of 10 yards. For an industry that has generated about 20% of U.S. electricity for decades, that’s a remarkably small physical footprint.
The comparison becomes even more striking on a per-person basis. If you got all your electricity from nuclear power for your entire life, your share of the high-level waste produced would be roughly the size of a soda can. The low-level waste would add another few pounds of material. By contrast, the average American’s share of coal ash, a byproduct that also contains radioactive elements like thorium and uranium, would weigh several tons over a lifetime.
None of this makes the waste problem trivial. A soda can’s worth of spent fuel is intensely radioactive and will remain hazardous for thousands of years. The challenge with nuclear waste has never really been volume. It’s the duration and intensity of the hazard, and the political difficulty of choosing where to put it permanently.