So the depleted nuclear fuel cannot be used to heat the reactor, but still has plenty of energy in the form of radiation. Why this radiation cannot be used or eliminated by trapping the neutrons from it and produce heat?
In: Physics
While decay heat can be significant enough to require cooling pumps for spent fuel pools, it’s not really enough to be cost-effective, as far as building a system that would capture heat and use it to generate power. It’d be a substantial fraction of the cost of a nuclear reactor but only generate a tiny sliver of the same energy. Also, the isotopes that are most radioactive also decay the fastest. So you get quickly diminishing returns from decay heat. Now, there is something called beta-voltaics, which involves taking isotopes that undergo beta decay (beta particles are just high-speed electrons) and putting them in a battery-like device to capture that energy. But it’s important that those devices only contain isotopes that undergo beta decay. Beta particles are super easy to stop. Neutrons and gamma rays, not so much. Since you don’t want your nuclear battery to irradiate you, you can’t just shove spent fuel into these things; you have to melt it down and process it and extract only the stuff that decays by spitting out beta particles. Which, again, is expensive. Also, only a very small amount of that spent fuel is going to consist of beta-decay-only isotopes..
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