Actinides (plutonium and minor actinides)

The heavy elements from actinium upward in the periodic table, including uranium, plutonium, neptunium, americium and curium. In reactor fuel, those heavier than uranium are made when uranium absorbs neutrons without splitting. After most fission products have decayed, actinides dominate the long-term radioactivity of spent fuel, over thousands to hundreds of thousands of years. Fast reactors can fission actinides that thermal reactors mostly cannot, which is the physical basis for claims that a reactor 'burns waste'. Such a claim is only meaningful if it says which actinides, from what fuel, at what rate, and whether the reprocessing it depends on exists. Fusion produces no actinides.

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concept:actinides

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