With the half life of the radioactive metals used in the fuel rods being thousands of years, the fuel used in reacors, i would think, should last for similar amounts of time. How come nuclear plants go through large ammount of spent fuel that then has to be stored?
A fission reactor is actively smashing the fuel to pieces, in order to release the energy faster. There are [RTGs](https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator) that only use the normal decay as its energy source, but they produce far less energy.
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