Nuclear waste - is it possible to use it all via fast reactors?

[Jarob22]

Hi, first poster here :$

I'm doing a case study on nuclear waste and was wondering whether it's possible to use all (or a large percentage of) the dangerous nuclear waste we currently dump, as fuel in fast reactors? Sorry if it's a stupid question to you but I don't know all that much about nuclear power :)

 

[Astronuc]

Hi, first poster here :$

I'm doing a case study on nuclear waste and was wondering whether it's possible to use all (or a large percentage of) the dangerous nuclear waste we currently dump, as fuel in fast reactors? Sorry if it's a stupid question to you but I don't know all that much about nuclear power :)

The actual waste - fission products - are not used as fuel, or are they useful as fuel. Much of the spent (used) fuel consists of unused uranium (U-235 or U-238) or transuranics (TU), e.g., isotopes of Pu, Am, Cm. Those elements have been proposed for use as fuel in fast reactors.

In most commercial light water reactors, about 5% of the fuel is used. The remaining fuel is unused while some (few %) is converted to TU isotopes.

 

[Jarob22]

I see - I'm just reading that these fission products can be used for other industrial and medical uses (though it doesn't cite what these uses are) - is it at all possible to use up a large %age of these fission products in other procsses? Or will we have to bury most of the fission waste?

 

[Astronuc]

I see - I'm just reading that these fission products can be used for other industrial and medical uses (though it doesn't cite what these uses are) - is it at all possible to use up a large %age of these fission products in other procsses? Or will we have to bury most of the fission waste?

In the US, the eventual disposal of spent (used) fuel has not been determined. Some want to place spent fuel in a respository, direct disposal, while others wish to reprocess (recover) the unused fuel and TU component. The rest of the spent fuel, i.e., fission products would be vitrified into a stable form and deposited into a repository.

Still others proposed to use accelerator driven systems to transmute spent fuel to shorter-lived nuclides prior to final disposal.

Some of the fission products (those which are not radioactive) would be useful for industrial purposes, but the problem is that they would have to be separated chemically from their radioactive relatives and other fission products.

 

[Jarob22]

Some of the fission products (those which are not radioactive) would be useful for industrial purposes, but the problem is that they would have to be separated chemically from their radioactive relatives and other fission products.

And I guess that's very expensive, right?

 

[Astronuc]

And I guess that's very expensive, right?

It's energy intensive and must be done remotely. That = expensive.

Laser isotopic separation helps reduce the cost somewhat.

 

[Jarob22]

Ah right. Thanks for your help :)

 

[nikkkom]

And I guess that's very expensive, right?

After U and Pu is separated, remaining stuff (fission products and some TUs) is emitting *millions* R/h. Any operations with it are hard. For example, chemical extraction of a non-radioactive element from it needs to be done several times: after first stage impurities make result "a bit" radioactive - "only" thousands R/h. You can easily calculate how many times one needs to repeat the process to arrive at acceptable level of activity (some micro-R/h).