Spent nuclear fuel rods – why can’t we just melt them down/reforge them?


As the title says; why can’t we just melt down the old fuel rods?

What would happen if we did melt them down?

Couldn’t we mix/contaminate them with another element to dilute the radioactive effects?

Most reactors work by heating water and turning turbines, why can’t we turn the spent fuel pools into a slow running reactors rather then using energy to keep them cool?

In: Physics

Sure, we could. However, there is a tiny problem. One of the radioactive byproducts is Plutonium. Melting spent fuel rods has to be done in a way that doesn’t facilitate the separation of this Plutonium and using it to make nuclear weapons. That’s increasingly difficult to convince the whole world you are doing. So, most of the time reprocessing isn’t done.

Fuel rods aren’t simply one kind of material to just melt down.

The easiest way to reduce their radioactive effects is to put them in a shielded location that people have minimal access to.

When they are spent, sure they do produce some heat, but not even close enough to produce steam to drive a turbine.

We do have some reactors that can use spent fuel, but it does get to the point where enough energy just simply isn’t produced. The other problem is that spent fuel needs stored somewhere where it can cool effectively and not spill radiation into the area. Fuel rods are dangerous to any living thing in their area. Risk plays a role in how we deal with them too. New reactors are able to use spent fuel though. That helps reduce some of the waste.

The spend fuel rods will be highly radioactive for millennia but will only generate heat so you need do cool them in spent fuel pool for 10 to 20 years.

The heat output is not that high so non have used it to produce power likely because the cost of the stuff you need is to expensive and would complicate thing and and increase the risk of a accident so it is not done.

The fuel rods can be reused where you remove the radioactive elements that is produced for storage and extract the uranium for new fuel rods. That is called [Nuclear_reprocessing](https://en.wikipedia.org/wiki/Nuclear_reprocessing). Part of the problem with it is that is how you extract plutonium for nuclear weapons so nuclear reprocessing contribute to nuclear proliferation ie the spread of nuclear weapons and what is needed for them. So today there is only plants in countries with nuclear weapons and fuel from other countries are reprocessed in som of them.

Spent fuel is extraordinarily radioactive. Also it’s not like a single solid material. You have zirconium cladding, which is the shell. Inside is fuel material, the ceramic fuel pellets. But you also have fission products, you have radioactive gasses, and all sorts of nasty stuff as a result of the random process of splitting atoms.

The radioisotope inventory is ridiculously high in the fuel rods. Melting them means breaking the zirconium shell that prevents lethal amounts of radioisotopes from escaping.