Stuff You Should Know

What To Do With All This Nuclear Waste?

November 4, 2025

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  • The current primary methods for managing spent nuclear fuel involve temporary storage in cooling pools followed by transfer to dry casks, as a permanent geologic repository solution, like the one planned for Yucca Mountain, remains stalled in the U.S. 
  • Despite the high danger of high-level waste (which constitutes only 3% of total waste volume but 95% of the radioactivity), there is significant untapped energy potential in spent fuel that could power the entire U.S. for 150 years if recycled. 
  • Finland is currently leading the world with its nearly complete deep geologic repository, Onkalo, which uses copper canisters encased in expanding bentonite clay buried 1,430 feet deep, representing the closest approach to a permanent solution discussed in this segment of *Stuff You Should Know*. 

Segments

Nuclear Waste Appearance and Types
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(00:02:29)
  • Key Takeaway: Nuclear waste does not glow green like in cartoons; the most dangerous form starts as solid uranium fuel pellets, about half a thumb’s size.
  • Summary: Nuclear waste is typically solid, not glowing green sludge, though toxic sludge consistency is mentioned as a possibility. The most dangerous waste originates from spent uranium fuel pellets, which are small cylinders. This high-level waste requires the most careful management.
Waste Volume and Danger Profile
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(00:05:58)
  • Key Takeaway: The total volume of nuclear waste generated per person is surprisingly small—about a hockey puck’s worth—but its danger stems from its extreme longevity.
  • Summary: All the nuclear power used by one person in their lifetime compresses to roughly a hockey puck’s volume. In the U.S. alone, the total waste amounts to about 90,000 tons. The primary issue is that this waste remains very dangerous for extremely long periods, necessitating specialized, long-term storage solutions.
Reactor Operation and Waste Generation
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(00:07:09)
  • Key Takeaway: Nuclear reactors boil water to create steam via fission of uranium-235 pellets housed in fuel assemblies, which must be replaced every five or six years.
  • Summary: Nuclear energy generation functions by using uranium-235 pellets within fuel rods, bundled into fuel assemblies, to boil water and turn a turbine, similar to fossil fuel plants but without emissions. These assemblies are kept underwater for cooling and to prevent criticality. Spent fuel assemblies are removed every 1.5 to 2 years and constitute the most dangerous nuclear waste.
Initial Cooling and Dry Cask Storage
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(00:11:28)
  • Key Takeaway: Spent fuel assemblies are first moved to deep, water-filled spent fuel pools for 2-5 years of cooling before being transferred to massive, concrete-encased dry casks rated for about 100 years.
  • Summary: Fuel assemblies are moved from the reactor core via canals into spent fuel pools containing about 40 feet of water for cooling, as exposure to air would cause them to combust and release dangerous isotopes like cesium-137. After cooling, they are placed into dry casks—steel canisters surrounded by specialized concrete—which are only guaranteed safe for about a century.
Interim Storage and Yucca Mountain Failure
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(00:17:06)
  • Key Takeaway: The U.S. lacks a permanent disposal site after the Yucca Mountain project was canceled in 2010, leaving the NRC reviewing applications for consolidated interim storage sites in New Mexico and Texas.
  • Summary: Currently, about 70% of global spent fuel is in pools and 30% in dry casks, often stored on or near the surface. The U.S. plan to use Yucca Mountain for deep geologic disposal was halted in 2010, leaving the waste in limbo. Interim storage sites, such as the proposed one in New Mexico, could fill up within 15 years given the current rate of 2,000 tons added annually.
Finland’s Permanent Repository
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(00:22:27)
  • Key Takeaway: Finland’s Onkalo repository buries copper-encased canisters 1,430 feet deep in bedrock, sealing the shafts with expanding bentonite clay, aiming for safety over 100,000 years.
  • Summary: The Finnish geologic repository, Onkalo, is designed to store waste 1,430 feet down in bedrock, utilizing steel canisters surrounded by a two-inch layer of non-corroding copper. The final shafts are filled with bentonite clay, which expands upon contact with water to form a tight seal around the canisters.
Waste Classification and Decommissioning Water
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(00:28:33)
  • Key Takeaway: Low-level waste (90% of volume) decays safely in 20-30 years and is treated like landfill material, but decommissioning plants still require dumping treated cooling water into waterways.
  • Summary: Low-level waste, such as contaminated protective gear, constitutes the majority of volume but decays relatively quickly. Transuranic waste, often from defense programs, has extremely long half-lives (e.g., Plutonium-239 at >24,000 years) and is stored in salt layers at the Waste Isolation Pilot Plant. After reactors are decommissioned, the water used in cooling pools is filtered, diluted, and typically dumped into nearby bodies of water.
Recycling and Future Solutions
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(00:39:56)
  • Key Takeaway: Recycling spent fuel, potentially through advanced reactors or MOX fuel creation, could reduce the most dangerous waste volume by 99% and unlock 150 years of U.S. power.
  • Summary: Recycling spent fuel allows for the extraction of usable fissile material, reducing the volume of highly radioactive waste significantly. Startups like Oklo estimate that current spent fuel could power the entire U.S. for 150 years if reused. A major obstacle to recycling is the security risk associated with handling fissile material that could be used for weapons.