
Lasers could cut lifespan of nuclear waste, a Nobel winner suggests - tokstesla
https://bigthink.com/technology-innovation/laser-nuclear-waste
======
petschge
For all we know this is possible but not at all practical. The NIF [1] already
does experiments with lasers that start nuclear processes in the ICF [2]
capsule. An exeptionally good shot produces 2e16 neutrons [3], from (about)
2e16 nuclear reaction. But that single shot required more than 400 MJ of
energy from the electrical grid to charge the capacitor banks that drove the
flash lamps that pump the lasers that input 500 TW of laser light for a tiny
fraction of a second into a hohlraum to heat it so high that the thermal x-ray
compresses the implosion capulse in the middle to a sufficient temperature and
density that nuclear processes start. Per neutron that was 2*10^-8 Joules. A
typical large 1000 MW nuclear reactor produces 25–30 tons of spent fuel per
year [4]. Assuming that nuclear waste has an average Z of about 50 and weights
100 daltons, 100 grams of material are one mole, so we have 3e5 mole to
reprocess with 2e29 nucleii that need to be treated. Assume that on average
only one neutron needs to be added or removed that will requires 3e21 MJ. But
the 1000 MW reactor running for 365 days, 24 hours a day, 3600 seconds per
hour only produced 3e10 MJ to begin with. In other words it would require 100
billion times as much electrical energy to convert nuclear waste that way than
you get out of the reactor creating that waste. Can we make things more
efficient by a factor 2 here and a factor 100 there? Probably. But that wont
make a dent.

Transmuting elements with lasers is really cool for basic science, but
completely useless as a solution for nuclear waste.

1:
[https://en.wikipedia.org/wiki/National_Ignition_Facility](https://en.wikipedia.org/wiki/National_Ignition_Facility)

2:
[https://en.wikipedia.org/wiki/Inertial_confinement_fusion](https://en.wikipedia.org/wiki/Inertial_confinement_fusion)

3: [https://www.llnl.gov/news/nif-achieves-record-double-
fusion-...](https://www.llnl.gov/news/nif-achieves-record-double-fusion-yield)

4: [https://en.wikipedia.org/wiki/High-
level_waste](https://en.wikipedia.org/wiki/High-level_waste)

~~~
cbkeller
To be fair, it looks like what he's proposing is fundamentally different from
inertial confinement fusion. Inertial confinement with lasers is so hard
because it's so tricky to apply perfectly even, symmetric force on every side
of the hohlraum. What's being proposed here seems to be more on the line of
<attosecond laser pulses _directly_ exciting the nucleus, so wouldn't be
useful for fusion but would have very different yields and wouldn't have the
same trouble with maintaining confinement.

~~~
petschge
Maybe. It is hard to find any scientifically accurate information on his
proposal. But if you say he wants laser intensities that are directly
sufficient to get 1 MeV (typical nuclear energies) across the 10fm of a
nucleus he would need intensities that are about a factor 100 above the
Schwinger limit [1] where the laser simply produces electrons and positrons
out of the vacuum. Cool if you want to study the plasma environments of
pulsars, but probably a HUGE loss mechanism in getting energy into the
nucleus.

In the end it all boils down to the fact that visible light an laser operate
on the energy scale of electronic transitions whereas nuclear transmutations
occur at the vastly different energy scale of the strong force. This huge
separation between electromagnetic interactions and strong nuclear
interactions is btw also the reason why radioactive material is not typically
green glowing goo.

1:
[https://en.wikipedia.org/wiki/Schwinger_limit](https://en.wikipedia.org/wiki/Schwinger_limit)

~~~
sansnomme
Swinger?

~~~
petschge
Sorry, that was a horrible typo for "Schwinger limit" that is now fixed. An
explanation can be found at [1].

The limit comes from the following process: Thanks to quantum mechanics there
is an uncertainty principle between position and momentum. Less known it the
uncertainty between time and energy. (If you have studied classical mechanic
you will recognize that the variable pairs are the same that you know from
Noethers theorem [3].)This implies that nature can (and will) violate
conservation of energy by an amount deltaE for a time deltat up to
hbar/deltaE. One such process is the creation of a electron-positron pair out
of vacuum. That violates energy conservation by about 1 MeV and you have to
return the (virtual) particles within hbar/1MeV or approximately 6e-22
seconds. If however the electric field is sufficiently large that the
particles get accelerated to an energy of 1 MeV within that time they get to
stay. An electric field that can do that has a field strength of 1.3e18 V/m.

At that intensity the laser light does not simply propagate through vaccuum as
predicted by Maxwells equations, but is producing a pair plasma and gets
damped. The process is fairly well described by QED. We are currently trying
to get laser up to that intensity and to make accurate measurements of this
QED effect as it does not only work for electron-positron pairs, but arbitrary
particle-antiparticle pairs. Experimental deviations from the QED predictions
would therefore imply the existence of additional light particles (and
antiparticle) that we have not found through other methods.

1:
[https://en.wikipedia.org/wiki/Schwinger_limit](https://en.wikipedia.org/wiki/Schwinger_limit)

2:
[https://en.wikipedia.org/wiki/Uncertainty_principle](https://en.wikipedia.org/wiki/Uncertainty_principle)

3:
[https://en.wikipedia.org/wiki/Noether%27s_theorem](https://en.wikipedia.org/wiki/Noether%27s_theorem)

------
thesz
I know about such suggestion for about, I guess, 20 years. It was suggested as
a way to clear radioactive waste in Chrenobyl contamination area.

And if you can read Russian, here a paper for your amusement for
semisuccessful attempt to implement that:
[http://www1.jinr.ru/Pepan_letters/panl_2017_6/13_Andreeva.pd...](http://www1.jinr.ru/Pepan_letters/panl_2017_6/13_Andreeva.pdf)

It contains a short English abstract which I copy here: _The influence of
laser irradiation on the gamma-activity of aqueous solutions of both 137Cs and
134Cs is experimentally studied in presence of Au nanoparticles at laser
intensity of order of 10^(12)W /cm2. It is found that laser irradiation
reduces the gamma-activity of both nuclides. This decrease is not accompanied
by excessful gamma radiation in the spectral range of gamma-activity of their
spontaneous decay. Possible mechanisms are discussed of the influence of laser
radiation on the activity of isotopes on the basis of laser field enhancement
on the plasmon resonance of nanoparticles._

------
uranium
... Or just burn it in a fast reactor, and get some use out of all that
leftover energy, instead of calling it waste?

~~~
brian_herman
Whats a fast reactor. I have never heard of it?

~~~
acidburnNSA
Neutrons come out of a fission event at high speed, about 20% the speed of
light. These are called fast neutrons. In almost all nuclear reactors we've
built, we deliberately slow these neutrons down with a moderator material
(which must have light atoms in it: things like graphite, water, beryllium).
It's much easier to get a pile of nuclear fuel to chain react when you slow
neutrons down, largely because Uranium-235's liklihood of absorbing a slow
neutron is much higher than its liklihood of absorbing a fast neutron.

(Aside: slow neutrons are often called "thermal" neutrons because they're in
thermal equilibrium with the atoms around them. At room temperature they're
going 2200 m/s, which corresponds to an energy of about 0.0253 electron-volts,
slowed down from 2 million electron-volts when they emerged from fission)

A fast-neutron reactor ("fast reactor") is a reactor where the neutrons that
emerge from a fission event are kept moving fast, simply by not putting a
moderator into the design. These reactors use heavy nuclei or very low density
material as coolants (sodium metal, lead-bismuth eutectic, helium, etc), so as
to not slow down any neutrons. It takes much more fissile fuel to get a pile
of nuclear fuel chain reacting in this configuration, but once you get it
going, you get some very nice benefits.

Once started, fast neutron chain reactions have a vast surplus of neutrons
going around. This is for two main reasons: (1) The number of neutrons emitted
per fission increases dramatically as the neutron speed increases above a
threshold around 1 MeV, and (2) parasitic absorption of fast neutrons is low
for all nuclides. With so many extra neutrons around, you can afford to put
extra "stuff" in your reactor, such as spent nuclear fuel (nuclear waste) or
extra fertile material (uranium-238 or thorium-232).

You can make these reactors into breeder reactors (which convert U-238 or
Th-232 into fissile fuel in such a way that could power the entire of humanity
10x over for a few million years, at least, using known resources), or you can
make these reactors into burner reactors, whose job it is to transmute used
fuel from other reactors into shorter-lived material (similar to what OP's
article is about, but much more practical).

A definitive guide to understanding transmutation of spent fuel in fast-
neutron reactors is put out by the UN's International Atomic Energy Commission
[TRS-435]:

"Implications of Partitioning and Transmutation in Radioactive Waste
Management" [https://www-
pub.iaea.org/MTCD/Publications/PDF/TRS435_web.pd...](https://www-
pub.iaea.org/MTCD/Publications/PDF/TRS435_web.pdf)

A handful of fast-neutron reactors have been built, starting with tiny single
critical mass assemblies in the 1940s, to the first true demo of breeding more
fuel than you consume in EBR-1 in 1951 to the EBR-2's safety demo weeks before
Chernobyl showing that the reactor could passively shut down and cool itself
without any human intervention or external power or control rods inserting, to
India's PFBR fast reactor that's been under construction for the past 18
years.

Only the Russians have successfully operated fast reactors commercially, via
the BN-350 and BN-600. In general, fast neutron reactors are considered more
complex and expensive to build and operate than traditional water-cooled
thermal neutron reactors.

We once thought uranium was very scarce, and so we put a lot of money into
fast breeder reactors. Then it turned out that there's lots of uranium and
fast reactors are largely on hold internationally. France just announced the
cancellation of its national fast reactor program (ASTRID). Russia delayed
their next BN fast reactor, saying their VVER (slow neutron) reactors are bout
4x cheaper. China and India are pushing forward. The US shut down its last
fast reactors (EBR-II and FFTF) in the early 1990s. Many nuclear startup
companies are now exploring options to get back into fast reactors.

The US DOE is putting forth a major project to build a new fast reactor very
similar to the FFTF, but in Idaho instead of Washington and with metal fuel
rods instead of oxide ceramic ones. The project is called the Versatile Test
Reactor (VTR) and is actively discussed in current nuclear news.

~~~
Synaesthesia
Lemme guess, they haven't become popular yet because there wasn't a way to
weaponise the results?

~~~
acidburnNSA
No. Weaponization of nuclear fission technology was completed in 1944.
Plutonium production plants of similar design to those used in the Manhattan
Project were used throughout the Cold War (at Hanford and Savannah River).
There are myths about various nuclear technologies being cancelled because
they "couldn't be weaponized" (usually talking about molten salt reactors),
but these myths are quite wrong.

Fast reactor tech hasn't been popular because it's more expensive than regular
old water-cooled fission reactor tech. To keep neutrons going fast you have to
use exotic coolants like sodium metal. Since you don't want to mix a chemical
hazard with a radiological one, you insert an additional intermediate heat
transfer loop into the system. Hot radioactive sodium transfers heat to hot
non-radioactive sodium which transfers heat to water which boils and turns a
turbine to crank a generator to push electrons around to provide low-carbon
service to human quality of life.

~~~
08-15
Can you please not call sodium "exotic"? Doing so adds to an irrational fear
of relatively benign technology.

Molten sodium is easy to pump, non-corrosive to many metals including steel,
and a good heat transfer medium. The chemical industry uses it routinely. In a
nuclear reactor, it would also chemically sequester a particularly annoying
fission product (I-131) in case of a fuel element leaking. Unpressurized, it
is good up to 800C before it boils.

By contrast, water at 300C will corrode most steels. At higher temperature, it
will corrode zircalloy, forming hydrogen. And it really wants to be a gas,
hence the giant containment buildings around LWR.

What did you say? "But sodium explodes in contact with water?" That's easy to
solve, just keep the water out. A sodium cooled reactor should be coupled to a
supercritical CO2 turbine instead of a steam turbine. That removes the problem
of leaking and exploding heat exchangers.

(Footnote: I like molten salts better than sodium. But sodium is still better
that water.)

~~~
acidburnNSA
Sodium coolant is exotic from an operational point of view. Exotic doesn't
mean dangerous. Sodium systems from a probabilistic risk statement are usually
100x safer than pressurized systems because of passive decay heat removal
capabilities. Exotic means "different from normal." So far, all operating
sodium-cooled plants have suffered from operational and economic challenges
due to sodium's characteristics. This is solvable with experience, but it's
not easy.

Have you ever studied a detailed procedure for heating up a large sodium valve
from the solid sodium phase to the liquid? If not I highly recommend doing so.
It's truly remarkable. Molten salt systems are the same level of complexity,
but much more radioactive in the primary system. Remote maintenance of this
stuff is totally doable, but it sure as hell is exotic. Rickover's
characterization of sodium systems stands to this day.

Traditional sodium systems with void-swelling resistant structural materials
may not go to high enough temperatures to strongly justify the tech
development needed for a sCO2 balance of plant in the short term. Sodium-water
steam generators with leak detection have worked well-enough to build a few
more of them while sCO2 turbomachinery gets figured out at the 100s of MW
scale.

------
trophycase
Can someone with more knowledge explain to me why it's so hard to reuse waste?
Like if it is emitting enough energy to contaminate entire swaths of land, why
can't you just build something to absorb all the radiation? I can't imagine it
is that much less efficient than a solar cell if you just stick it in a box.

~~~
hn_throwaway_99
It's not, and many other countries do. However, there are still big concerns
about the overall economic payback of reprocessing, and also concerns about
nuclear proliferation:

[https://www.forbes.com/sites/realspin/2014/10/01/why-
doesnt-...](https://www.forbes.com/sites/realspin/2014/10/01/why-doesnt-u-s-
recycle-nuclear-fuel/)

[https://en.m.wikipedia.org/wiki/Nuclear_reprocessing](https://en.m.wikipedia.org/wiki/Nuclear_reprocessing)

~~~
jimmaswell
Makes sense all the other power source industries would try to lobby nuclear
into the ground - if it was used to its potential without political
shenanigans and scaremongering in the way we'd have all the cheap green energy
we needed with all the other sources out of business.

------
smaddox
It seems unlikely to me that this could be an efficient way to burn
radioactive waste. However, there is another approach that combines a linear
electron accelerator with infrared laser pulses to generate absurdly high
power (compared to traditional accelerator sources) gamma rays:
[https://www.sciencedaily.com/releases/2011/04/110426160211.h...](https://www.sciencedaily.com/releases/2011/04/110426160211.htm)

The tunability of this gamma rays source makes it possible to target and
induce nuclear reactions in unstable atoms.

If I remember correctly, when I saw the seminar talk by the originator of the
concept, a few years ago, he said that an existing super-conductor-based
linear accelerator in Japan could feasibily by modified to generate enough
gamma rays to burn thousands of tons of radioactive waste per year. (Don't
quote me on the exact amounts, though, it's been a while).

~~~
baybal2
Even if it somehow works, photofission will never be energy efficient. You
will be spending gigawatt hours per gram of fissioning matter

~~~
smaddox
Why do you say that? The approach I linked can be an absurdly efficient way to
generate gamma rays with super-conductor magnets and electron recycling, like
the Japanese electron accelerator has. And keep in mind, these atoms are
already unstable. The photon just excites the nucleas out of the meta-stable
ground state.

------
goldilmje
> _Take the nucleus of an atom. It is made up of protons and neutrons. If we
> add or take away a neutron, it changes absolutely everything. It is no
> longer the same atom, and its properties will completely change._

Are they talking about transmutation with lasers? Would it work for Lead ->
Gold too?

~~~
jacquesm
Yes, but not economically. For an encore, the oceans contain plenty of gold
too, a coupe of parts-per-trillion. It's yours for the taking.

~~~
mint29
(shhh don't tell him about biological fouling) Did I say that out loud?

------
jacknews
Is that figure correct, 22,000 m3?

That's just a cube 28m on a side, maybe the same size as a small apartment
block.

Just dump it into a subduction zone

~~~
endymi0n
Nice idea, but refuted already:
[https://www.nwmo.ca/~/media/Site/Reports/2015/11/11/06/32/12...](https://www.nwmo.ca/~/media/Site/Reports/2015/11/11/06/32/1287_baird-
submissiononthetopic_cho.ashx)

~~~
jacknews
Am I skimming this too quickly, or does it actually say sub-seabed/subduction
sequestration is one of the few options that actually works - it's just not
currently possible because of international "dumping at sea" treaties?

With such a small volume I think 'do nothing' is fine at the moment until we
can find an economical use for it (fast breeder, traveling-wave etc, etc), or
agree the best way to dispose of it - 20,000-year managed repositories don't
seem viable to me.

------
jl2718
I don’t understand how high-intensity CPA photons with wavelengths in order of
a micron are supposed to have any effect on the nucleus, but there definitely
are a lot of electrons ready to absorb them. Regardless, there are many much
more efficient ways to generate thermal neutrons if that’s what he’s after,
which agree with, and you can get controlled energy out of it! Years ago I
proposed a small nuclear waste fueled engine design based on this principle.

------
egdod
My understanding was that you’d need gamma radiation for the nucleus to even
notice it. Lots of low energy photons isn’t the same as fewer high energy
photons.

~~~
petschge
That is true until you have to so many photons that you hit the QED regime
where photons interact with each other and electrodynamics becomes non-linear.
However at that point no just the nucleii notice, but you start to get all
kinds of other effects.

------
08-15
Awful reporting about a bad idea.

The actual proposal isn't to irradiate nuclear waste with lasers. The idea is
to use the laser to accelerate protons, irradiate heavy nuclei with those
protons to get them to either fission or at least emit neutrons, irradiate
long-lived waste with those neutrons to transmute it. It's possible in theory.

In practice, it's nonsense. These accelerators have low efficiency and produce
few neutrons. This makes the process slow and inefficient. So inefficient in
fact, that all practical (for small values of "practical") proposals are
actually for sub-critical reactors that use nuclear fission to amplify the
neutron output.

But then the idiocy becomes clear: instead of a sub-critical reactor and an
unbelievably expensive accelerator, you might as well build a critical
reactor, recycle the actinides directly and maybe transmute the fission
products.

In other words, this is a guy who just likes particle accelerators. He has a
solution, now he's looking for a suitable problem.

------
dr_dshiv
If nuclear material is irradiated by tunable lasers, are there particular
wavelengths that increase or decrease alpha/beta/gamma emission?

Short of neutron guns, are there environmental conditions that affect nuclear
half-life?

------
ganzuul
This must actually be about stimulated emission on the nuclear scale, with
much getting lost in translation on the way to something politically
marketable...

There is much to be learned in this space still.

------
elif
I failed physics but, in theory if you could keep pouring neutrons into
fissile material, couldn't you lower the amount of nuclear fuel required to
achieve critical mass (which is bound by the rate of neutron loss)?

Wouldn't this basically boost mpg and/or increase safety of reactors?

~~~
Enginerrrd
I believe there are some newer theoretical reactor designs based around this
concept! In essence, they are designed such that the fuel is not in itself
capable of sustaining a chain reaction. It is only with the active addition of
neutrons that you can get the fission reaction underway. So if you halt that
supply of neutrons from the neutron generator, the reaction dies off, greatly
enhancing passive safety.

------
rdl
I've been waiting for Atomic Vapor Isotope Separation (AVLIS or MLIS or SILEX)
to let a small group or small state produce their first nuclear weapon
basically outside the current nonproliferation controls.

------
manfredo
Is storing nuclear waste even a significant concern? The entirety of US
nuclear power generation's waste can fit in a rectangle that is 20 feet high
and the width and length of a football field. This is trivial in terms of
volume of waste disposal. There's really not much difficulty in disposing
this. Bury it in a site without groundwater.

~~~
chris11
Nuclear waste storage is a huge issue politically though.

~~~
manfredo
My point remains: is there any actual safety concern with putting nuclear
waste underground other than potential groundwater pollution if the
containment casks get perforated (which can be avoided by not burying waste
where there's groundwater)?

The only scenarios that people have presented in which nuclear waste could
result in contamination are borderline absurd, like if humanity hypothetically
loses all records of where waste is buried along with knowledge of what
radiation is and some future civilization might dig up the waste canisters and
crack them open.

~~~
grzm
There’s plenty of research on this topic. Perhaps you can find the Wikipedia
entry a useful jumping off point. [https://en.wikipedia.org/wiki/High-
level_radioactive_waste_m...](https://en.wikipedia.org/wiki/High-
level_radioactive_waste_management)

~~~
manfredo
Nothing in your link covers the safety or dangers of waste disposal beyond the
vague statement that, "There is general agreement that placing spent nuclear
fuel in repositories hundreds of meters below the surface would be safer than
indefinite storage of spent fuel on the surface." That article is a couple
paragraphs on waste containers, and a list of different countries' waste
management schemes. It doesn't dig into any long term risk assessment.

------
m3kw9
Maybe another idea is when rockets are cheap enough < cost of storing. Send
them into the sun.

~~~
cameronbrown
And if something goes wrong and nuclear waste is scattered through the
atmosphere? I think we'll get to a point where we can do it safely, but
there's always a chance. Maybe if costs are low, generating energy in space
and shipping it back (either as batteries or a literal wire) would be better.

~~~
Retric
It’s not a good idea, but it could be done very safely. Personally, I think
nuclear power is simply to expensive to be particularly useful going forward,
but IMO waste is a smaller issue than generally perceived.

Sure, you would encase them in something that could survive reentry or
detonation of the rocket. Choosing a launch location and trajectory for easy
recovery is also possible.

However, paying 1,000+$/lb to get rid of Nuclear waste is extremely expensive.
Simply storing it in a pond for ~120 years and the stuff gets vastly less
radioactive as short half-life material decays. Strontium-90 and cesium-137
have half-lives of about 30 years so you get 6% as much of them and
essentially everything with a shorter half life is gone. Plutonium-238 has a
longer half life of 87 years, but you also get rid of ~2/3 of that.

You still have almost off the Plutonium-239 with a half-life of 24,000 years,
but that stuff is not nearly as nasty and can be reprocessed for fuel.
Further, reprocessing becomes cheaper after waiting for it to cool down.

PS: Plutonium-238, Strontium-90 and cesium-137 can also be used for space
probes via:
[https://en.m.wikipedia.org/wiki/Radioisotope_thermoelectric_...](https://en.m.wikipedia.org/wiki/Radioisotope_thermoelectric_generator)

------
WheelsAtLarge
We see all these pie in the sky solutions all the time but please don't start
counting on them becoming reality. It's great to dream and work towards the
dream but don't count on it as a solution.

For now, the solution is to use nuclear fuel in the most efficient manner so
as to minimize waste.

