9 ms·

Lasers could cut lifespan of nuclear waste, a Nobel winner suggests

141 points by tokstesla 7y ago

goldilmje 7y ago
> 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?
- mikeyouse 7y ago
  I suspect it's vastly easier to add or remove a single neutron rather than to remove several protons like you'd have to do to transmute between elements.
- deleted 7y ago
  [deleted]
- jacquesm 7y ago
  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 7y ago
    (shhh don't tell him about biological fouling) Did I say that out loud?
deleted 7y ago
[deleted]
uranium 7y ago
... 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 7y ago
  Whats a fast reactor. I have never heard of it?
  - deleted 7y ago
    [deleted]
  - ttul 7y ago
    https://en.wikipedia.org/wiki/Fast-neutron_reactor https://en.wikipedia.org/wiki/Fast-neutron_reactor
  - jabl 7y ago
    A reactor with a fast, as opposed to thermal, neutron spectrum. Among other things, implies that it must be cooled by something else than plain water, which is is a neutron moderator (that is, slows down the neutrons to thermal velocities). Often the coolant of choice is a metal like sodium or lead. Fast reactors enables breeding, that is producing more fissile material from the fuel than is consumed. They are also better at burning up various isotopes that thermal reactors have trouble with.
  - acidburnNSA 7y ago
    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.pdf https://www-pub.iaea.org/MTCD/Publications/PDF/TRS435_web.pd... 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.
petschge 7y ago
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-yield https://www.llnl.gov/news/nif-achieves-record-double-fusion-... 4: https://en.wikipedia.org/wiki/High-level_waste https://en.wikipedia.org/wiki/High-level_waste
- cbkeller 7y ago
  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.
ganzuul 7y ago
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 7y ago
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 7y ago
  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.
- petschge 7y ago
  The mpg of reactors (or rather the burnup) is measured by the energy extracted from the primary fuel. In practice that is not limited by neutron flux, but by accumulation of gaseous fission products inside the fuel or the cladding. They do not get any better when you supply external neutron flux. Other, secondary concerns such as the fact that you need to leave the fuel in the ractor for a long time inside the reactor, which leaves a lot of time for corrosion to take place might be reduced. But in the end it is rather costly to produce neutrons with non-nuclear means on the outside.
Spooky23 7y ago
The usual HN-hive mind answer is that more deaths per megawatt would be caused by the laser than by the waste product. Usually there’s a follow up that the waste product isn’t really waste product, because it can be enriched and used in breeder reactors, etc.
- jacquesm 7y ago
  Pretty cheap to refer to comments older than yours in a comment like this.
  - Spooky23 7y ago
    Mea culpa, I’m on the road and apparently I didn’t refresh and took awhile to post. That said, any story on nuclear waste topics has those comments. I spent time in a place devastated economically by (non-nuclear) pollution from a supposedly contained industrial waste product, and I worry about proliferation. So the casual advocacy of nuclear energy may provoke a stronger reaction from me than may be warranted.
thesz 7y ago
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.pdf http://www1.jinr.ru/Pepan_letters/panl_2017_6/13_Andreeva.pd... 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.
trophycase 7y ago
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 7y ago
  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-u-s-recycle-nuclear-fuel/ https://www.forbes.com/sites/realspin/2014/10/01/why-doesnt-... https://en.m.wikipedia.org/wiki/Nuclear_reprocessing https://en.m.wikipedia.org/wiki/Nuclear_reprocessing
  - jimmaswell 7y ago
    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.
- nipponese 7y ago
  The solid nuclear fuel business is structured like the multi-color printer cartridge business: once a specific uranium isotope is depleted, you have to throw the whole thing away. FWIW, there are several projects, including one funded by the Bill & Melinda Gates Foundation, trying to solve the issue, but are running into significant political pushback. https://en.wikipedia.org/wiki/TerraPower https://en.wikipedia.org/wiki/TerraPower
  - trophycase 7y ago
    Am I reading this right? "erraPower notes that the US hosts 700,000 metric tons of depleted uranium and that 8 metric tons could power 2.5 million homes for a year.[9] Some reports claim that the high fuel efficiency of TWRs, combined with the ability to use uranium recovered from river or sea water, means enough fuel is available to generate electricity for 10 billion people at US per capita consumption levels for million-year time-scales." That sounds completely crazy haha
SpaceMnkyPolice 7y ago
This sounds a lot more efficient than smelting it down into ammunition and shooting it at brown people, like the Bush administration tried.
dr_dshiv 7y ago
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?
m3kw9 7y ago
Maybe another idea is when rockets are cheap enough < cost of storing. Send them into the sun.
- m3kw9 7y ago
  On the other hand, the risk of it blowing up in the sky shoots down the plan.
- comicjk 7y ago
  Launching things from the Earth to the Sun is very difficult. We're talking a Saturn-V-sized rocket to move less than a lunar-lander-mass of waste. The fundamental problem is that the Earth moves fast in its orbit, and in order to drop your spaceship's orbit towards the Sun you have to slow down. https://space.stackexchange.com/questions/13396/do-any-current-icbms-have-the-delta-v-to-target-the-sun https://space.stackexchange.com/questions/13396/do-any-curre...
- cameronbrown 7y ago
  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 7y ago
    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_generator https://en.m.wikipedia.org/wiki/Radioisotope_thermoelectric_...
jl2718 7y ago
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 7y ago
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 7y ago
  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.
manfredo 7y ago
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 7y ago
  Nuclear waste storage is a huge issue politically though.
  - manfredo 7y ago
    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 7y ago
      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_management https://en.wikipedia.org/wiki/High-level_radioactive_waste_m...
      - manfredo 7y ago
        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.
jacknews 7y ago
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 7y ago
  Nice idea, but refuted already: https://www.nwmo.ca/~/media/Site/Reports/2015/11/11/06/32/1287_baird-submissiononthetopic_cho.ashx https://www.nwmo.ca/~/media/Site/Reports/2015/11/11/06/32/12...
  - Roverlord 7y ago
    It doesn't read like a refutation, more an endorsement of subductive disposal, but with recognition that it's not presently legal, but that maybe there's a loophole in Vancouver.
  - jacknews 7y ago
    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.
WheelsAtLarge 7y ago
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.
smaddox 7y ago
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.htm https://www.sciencedaily.com/releases/2011/04/110426160211.h... 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 7y ago
  Even if it somehow works, photofission will never be energy efficient. You will be spending gigawatt hours per gram of fissioning matter
  - smaddox 7y ago
    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.
08-15 7y ago
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.
rdl 7y ago
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.

141 points by tokstesla 7y ago

> 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?

mikeyouse 7y ago
I suspect it's vastly easier to add or remove a single neutron rather than to remove several protons like you'd have to do to transmute between elements.
deleted 7y ago
[deleted]
jacquesm 7y ago
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 7y ago
  (shhh don't tell him about biological fouling) Did I say that out loud?

deleted 7y ago

[deleted]

uranium 7y ago

... 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 7y ago
Whats a fast reactor. I have never heard of it?
- deleted 7y ago
  [deleted]
- ttul 7y ago
  https://en.wikipedia.org/wiki/Fast-neutron_reactor https://en.wikipedia.org/wiki/Fast-neutron_reactor
- jabl 7y ago
  A reactor with a fast, as opposed to thermal, neutron spectrum. Among other things, implies that it must be cooled by something else than plain water, which is is a neutron moderator (that is, slows down the neutrons to thermal velocities). Often the coolant of choice is a metal like sodium or lead. Fast reactors enables breeding, that is producing more fissile material from the fuel than is consumed. They are also better at burning up various isotopes that thermal reactors have trouble with.
- acidburnNSA 7y ago
  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.pdf https://www-pub.iaea.org/MTCD/Publications/PDF/TRS435_web.pd... 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.

petschge 7y ago

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-yield https://www.llnl.gov/news/nif-achieves-record-double-fusion-... 4: https://en.wikipedia.org/wiki/High-level_waste https://en.wikipedia.org/wiki/High-level_waste

cbkeller 7y ago
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.

ganzuul 7y ago

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 7y ago

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 7y ago
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.
petschge 7y ago
The mpg of reactors (or rather the burnup) is measured by the energy extracted from the primary fuel. In practice that is not limited by neutron flux, but by accumulation of gaseous fission products inside the fuel or the cladding. They do not get any better when you supply external neutron flux. Other, secondary concerns such as the fact that you need to leave the fuel in the ractor for a long time inside the reactor, which leaves a lot of time for corrosion to take place might be reduced. But in the end it is rather costly to produce neutrons with non-nuclear means on the outside.

Spooky23 7y ago

The usual HN-hive mind answer is that more deaths per megawatt would be caused by the laser than by the waste product. Usually there’s a follow up that the waste product isn’t really waste product, because it can be enriched and used in breeder reactors, etc.

jacquesm 7y ago
Pretty cheap to refer to comments older than yours in a comment like this.
- Spooky23 7y ago
  Mea culpa, I’m on the road and apparently I didn’t refresh and took awhile to post. That said, any story on nuclear waste topics has those comments. I spent time in a place devastated economically by (non-nuclear) pollution from a supposedly contained industrial waste product, and I worry about proliferation. So the casual advocacy of nuclear energy may provoke a stronger reaction from me than may be warranted.

thesz 7y ago

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.pdf http://www1.jinr.ru/Pepan_letters/panl_2017_6/13_Andreeva.pd... 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.

trophycase 7y ago

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 7y ago
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-u-s-recycle-nuclear-fuel/ https://www.forbes.com/sites/realspin/2014/10/01/why-doesnt-... https://en.m.wikipedia.org/wiki/Nuclear_reprocessing https://en.m.wikipedia.org/wiki/Nuclear_reprocessing
- jimmaswell 7y ago
  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.
nipponese 7y ago
The solid nuclear fuel business is structured like the multi-color printer cartridge business: once a specific uranium isotope is depleted, you have to throw the whole thing away. FWIW, there are several projects, including one funded by the Bill & Melinda Gates Foundation, trying to solve the issue, but are running into significant political pushback. https://en.wikipedia.org/wiki/TerraPower https://en.wikipedia.org/wiki/TerraPower
- trophycase 7y ago
  Am I reading this right? "erraPower notes that the US hosts 700,000 metric tons of depleted uranium and that 8 metric tons could power 2.5 million homes for a year.[9] Some reports claim that the high fuel efficiency of TWRs, combined with the ability to use uranium recovered from river or sea water, means enough fuel is available to generate electricity for 10 billion people at US per capita consumption levels for million-year time-scales." That sounds completely crazy haha

SpaceMnkyPolice 7y ago

This sounds a lot more efficient than smelting it down into ammunition and shooting it at brown people, like the Bush administration tried.

dr_dshiv 7y ago

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?

m3kw9 7y ago

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

m3kw9 7y ago
On the other hand, the risk of it blowing up in the sky shoots down the plan.
comicjk 7y ago
Launching things from the Earth to the Sun is very difficult. We're talking a Saturn-V-sized rocket to move less than a lunar-lander-mass of waste. The fundamental problem is that the Earth moves fast in its orbit, and in order to drop your spaceship's orbit towards the Sun you have to slow down. https://space.stackexchange.com/questions/13396/do-any-current-icbms-have-the-delta-v-to-target-the-sun https://space.stackexchange.com/questions/13396/do-any-curre...
cameronbrown 7y ago
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 7y ago
  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_generator https://en.m.wikipedia.org/wiki/Radioisotope_thermoelectric_...

jl2718 7y ago

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 7y ago

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 7y ago
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.

manfredo 7y ago

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 7y ago
Nuclear waste storage is a huge issue politically though.
- manfredo 7y ago
  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 7y ago
    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_management https://en.wikipedia.org/wiki/High-level_radioactive_waste_m...
    - manfredo 7y ago
      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.

jacknews 7y ago

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 7y ago
Nice idea, but refuted already: https://www.nwmo.ca/~/media/Site/Reports/2015/11/11/06/32/1287_baird-submissiononthetopic_cho.ashx https://www.nwmo.ca/~/media/Site/Reports/2015/11/11/06/32/12...
- Roverlord 7y ago
  It doesn't read like a refutation, more an endorsement of subductive disposal, but with recognition that it's not presently legal, but that maybe there's a loophole in Vancouver.
- jacknews 7y ago
  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.

WheelsAtLarge 7y ago

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.

smaddox 7y ago

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.htm https://www.sciencedaily.com/releases/2011/04/110426160211.h... 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 7y ago
Even if it somehow works, photofission will never be energy efficient. You will be spending gigawatt hours per gram of fissioning matter
- smaddox 7y ago
  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.

08-15 7y ago

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.

rdl 7y ago

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.