Catalyst with Shayle Kann The state and future of nuclear waste
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Mar 26, 2026 Dr. Jen Schaefer, a nuclear fuel-cycle expert and professor at Colorado School of Mines, breaks down what spent fuel is and which isotopes drive long-term risk. She walks through storage methods from pools to dry casks. The conversation covers Yucca Mountain, recycling versus disposal, how advanced reactor fuels change the problem, and novel take-back ideas for microreactors.
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Spent Fuel Is Mostly Solid Unused Uranium
- Spent nuclear fuel is primarily a solid uranium dioxide ceramic, not a liquid or goo.
- About 95% remains unreacted uranium and ~5% are fission and transmutation products including plutonium and other actinides that drive long-term risk.
Actinides Drive Multi‑Millennial Waste Burden
- The long-term hazard of used fuel is dominated by actinides (plutonium, neptunium, americium) that persist for tens of thousands to millions of years.
- Most fission products decay within hundreds of years, though exceptions like technetium-99 and some iodine isotopes have much longer burdens.
Recycle Actinides Using Fast Reactors To Shrink Long‑Term Waste
- Recycle and irradiate actinides in fast reactors to convert long‑lived elements into shorter‑lived fission products and reduce repository burdens.
- This requires fast reactor deployment and fuel‑cycle infrastructure; light water reactors can't easily do the same loop.