Laser pulses could reduce the half-life of nuclear waste to just 30 minutes

[ElliotSmith]

TL;DR Summary

Nobel-prize winning scientist believes he can use pulsed lasers to reduce the radioactivity half-life of nuclear waste from millions of years, to as little as 30 minutes.

If this could actually be achieved, it would probably win him another Nobel prize, and solve the dilemma of nuclear waste for good.

https://bigthink.com/technology-inn...4PHRXCKfWmBt2qeRquOYMAgIXUjqSVEK1kqK2hSkUktcg

 

[mfb]

It takes a huge amount of energy to kick out a proton or neutron from a nucleus.

Most of the problematic nuclear waste could be used in accelerator-driven subcritical reactors. You even get some energy out of the process. The few isotopes that are not suitable for transmutation there (neutron cross section too low) might be an interesting target for laser transmutation.

 

[DEvens]

The article is not particularly revealing as to exactly what is being suggested. But it seems like Gérard Mourou is suggesting using lasers to kick protons out of the nuclei of troublesome nuclear waste. I have my concerns about the energetics of such a process. Lasers are not known for being especially efficient. If it takes more energy to do it than you got from the nuclear reactor, there would seem to be a problem.

But just for fun. Suppose he can kick a proton out. Pu-239 starts with a half life of 24,100 years. Lose a proton you get Np-238. It has a half-life, by Beta decay, of 2.1 days to Pu-238. Hmm... Getting messy.

Sigh. It's getting more messy than I have time to do correctly just at the moment. But as a ballpark back-of-the-envelope estimate, each proton pulled out uses about 5 MeV, and a fission produces round about 200 MeV. So it's pretty expensive to do this proton extraction stuff. And the stuff that is produced by a single proton removal isn't all that much preferable to what you have before.

 

[PeterDonis]

Suppose you could bump it down again to Pu-237.

Bump from where? Knocking a proton out of what nucleus? (Same question for the further bumps.)

 

[DEvens]

Bump from where? Knocking a proton out of what nucleus? (Same question for the further bumps.)

Hmmm... I did that wrong, didn't I. Should have been Pu-239 going to Np-238, since he's kicking out a proton.

 

[DEvens]

I don't know a lot about smacking stuff with lasers. But to get a proton out of a nucleus, wouldn't it be necessary to have a photon with enough energy to get the proton over its energy hump? That is, typically a few MeV.

Since visible light is in the few-electron-volt range, does this guy really have lasers that produce MeV photons?

Hmmm... Googling around, maybe it's possible to get those several-MeV photons.

https://arxiv.org/abs/1102.4451
Seems the idea is to point a laser head-on into a beam of GeV electrons. Back scattered photons will come back with the required energy.

 

[mfb]

We do this already, and it is the brightest source of photons in the multi-MeV range we have. ~10 MeV here

It has been proposed to use heavy nuclei with a single electron as beams in the same way. Their gamma factor (speed) is lower but their cross section is orders of magnitude larger. At the LHC this could produce photons with tens to hundreds of MeV with unprecedented brilliance. The LHC already tested the acceleration step last year. Longer comment and further links here.

 

[ElliotSmith]

Wouldn't accelerating the radioactive decay of nuclear material to 30 minutes cause it to expel all of it's stored radiation within that timeframe?

 

[mfb]

The proposal transmutes the nuclei to different nuclei, so it's not the same. Anyway: Yes, it would increase the activity a lot. That's what you want. Store it for a day and it becomes harmless (or just chemical waste, or maybe even some useful chemical).

 

[gmax137]

stored radiation

This is at best, a flawed mental image of what it means for an atom to be radioactive.