system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How come spent nuclear fuel is constantly being cooled for about 2 decades? Why can't we just use the spent fuel to boil water to spin turbines?
gpt
Spent nuclear fuel just doesn't produce enough heat to make it useful for producing steam. The amount of power you'd get out of it that way simply would never pay for the cost of building and running the system.

It can be recycled however. Spent fuel still contains a lot of useful radioisotopes and there are types of reactors designed to recycle the spent fuel back into usable nuclear fuel. The problem is, that on top of the normal political concerns with nuclear reactors, recycling can produce plutonium, which is used in nuclear weapons. Because it is very difficult to tell the difference between a fuel recycling plant and a weapon-making plant from outside, many countries have decided to not recycle to avoid political and diplomatic troubles.