eli5 If nuclear waste is radioactive, can’t we generate electricity from it emitting radioactive particles?
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It’s radioactive, but nuclear reactors don’t work off of the natural decay of the materials in them (which are, in fact, a lot *less* radioactive than the produces in waste).
Nuclear reactors work by using a nuclear chain reaction to make atoms decay millions of times faster than they normally would. And it turns out that only a very few specific isotopes can sustain such a chain reaction. Once the chain reaction shuts down, you’re left with the normal decay rate of the material, which is high enough to be dangerous to life but not high enough to be useful for power generation.
To put some scale on this, a short-term radiation exposure of about 10 Sv is nearly always fatal to a human being. 1 Sv is, with some weighting, about 1 J of energy per kg of body tissue, meaning that for a 75 kg human, a 10 Sv exposure is only about 750 J of energy. That’s enough to power a lightbulb for a matter of seconds or, if you prefer, about as much energy as being hit by a heavy object at human-typical speeds. So even when it’s not emitting very much overall power, nuclear waste can still be incredibly dangerous to human life.
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