The end of nuclear waste ? 6


fission-and-fusionBy reading Clean Technica I came across a news that might change the way many people consider nuclear energy. Indeed, one of the main issues of nuclear today is the waste produced by fission.

But to researches carried out in the University of Texas at Austin a process called Compact Fusion Neutron Source (CFNS), combines fission and fusion and would allow to cut by 99 percent the amount of by-products.

CFNS  is based on tokamak technology and uses a crucial invention: the Super X Divertor. This could represent a brilliant solution for the future.To PhysOrg.com :

“We have created a way to use fusion to relatively inexpensively destroy the waste from nuclear fission,” says Mike Kotschenreuther, senior research scientist with the Institute for Fusion Studies (IFS) and Department of Physics. “Our waste destruction system, we believe, will allow nuclear power-a low carbon source of energy-to take its place in helping us combat global warming.”

(…) The physicists’ new invention could drastically decrease the need for any additional or expanded geological repositories.

“Most people cite nuclear waste as the main reason they oppose nuclear fission as a source of power,” says Swadesh Mahajan, senior research scientist.

The scientists propose destroying the waste using a fusion-fission hybrid reactor, the centerpiece of which is a high power Compact Fusion Neutron Source (CFNS) made possible by a crucial invention.

The CFNS would provide abundant neutrons through fusion to a surrounding fission blanket that uses transuranic waste as nuclear fuel. The fusion-produced neutrons augment the fission reaction, imparting efficiency and stability to the waste incineration process.

Kotschenreuther, Mahajan and Prashant Valanju, of the IFS, and Erich Schneider of the Department of Mechanical Engineering report their new system for nuclear waste destruction in the journal Fusion Engineering and Design.

(…) The scientists’ waste destruction system would work in two major steps.

First, 75 percent of the original reactor waste is destroyed in standard, relatively inexpensive LWRs. This step produces energy, but it does not destroy highly radiotoxic, transuranic, long-lived waste, what the scientists call “sludge.”

In the second step, the sludge would be destroyed in a CFNS-based fusion-fission hybrid. The hybrid’s potential lies in its ability to burn this hazardous sludge, which cannot be stably burnt in conventional systems.

“To burn this really hard to burn sludge, you really need to hit it with a sledgehammer, and that’s what we have invented here,” says Kotschenreuther.

One hybrid would be needed to destroy the waste produced by 10 to 15 LWRs.

The process would ultimately reduce the transuranic waste from the original fission reactors by up to 99 percent. Burning that waste also produces energy.

The CFNS is designed to be no larger than a small room, and much fewer of the devices would be needed compared to other schemes that are being investigated for similar processes. In combination with the substantial decrease in the need for geological storage, the CFNS-enabled waste-destruction system would be much cheaper and faster than other routes, say the scientists.

The CFNS is based on a tokamak, which is a machine with a “magnetic bottle” that is highly successful in confining high temperature (more than 100 million degrees Celsius) fusion plasmas for sufficiently long times.

The crucial invention that would pave the way for a CFNS is called the Super X Divertor. The Super X Divertor is designed to handle the enormous heat and particle fluxes peculiar to compact devices; it would enable the CFNS to safely produce large amounts of neutrons without destroying the system.

“The intense heat generated in a nuclear fusion device can literally destroy the walls of the machine,” says research scientist Valanju, “and that is the thing that has been holding back a highly compact source of nuclear fusion.”

Valanju says a fusion-fission hybrid reactor has been an idea in the physics community for a long time.

“It’s always been known that fusion is good at producing neutrons and fission is good at making energy,” he says. “Now, we have shown that we can get fusion to produce a lot of neutrons in a small space.”

Producing an abundant and clean source of “pure fusion energy” continues to be a goal for fusion researchers. But the physicists say that harnessing the other product of fusion-neutrons-can be achieved in the near term.

In moving their hybrid from concept into production, the scientists hope to make nuclear energy a more viable alternative to coal and oil while waiting for renewables like solar and pure fusion to ramp up.

“The hybrid we designed should be viewed as a bridge technology,” says Mahajan. “Through the hybrid, we can bring fusion via neutrons to the service of the energy sector today. We can hopefully make a major contribution to the carbon-free mix dictated by the 2050 time scale set by global warming scientists.”

The scientists say their Super X Divertor invention has already gained acceptance in the fusion community. Several groups are considering implemented the Super X Divertor on their machines, including the MAST tokamak in the United Kingdom, and the DIIID (General Atomics) and NSTX (Princeton University) in the U.S. Next steps will include performing extended simulations, transforming the concept into an engineering project, and seeking funding for building a prototype.

Original news by Clean Technica.


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6 thoughts on “The end of nuclear waste ?

  • Tim

    That would be a major step toward public-acceptance even if it does not solve the large misunderstanding that Nuclear Powerplants and Atom Bombs are not the same thing at all (and this is, in my opinion, the major issue). But it’s none too late for that kind of technology to show up, now that ITER is on its way.

    One limit though is the cost of the project. Knowing our representative’s way of thinking, I doubt they will do things for the good sake of the environment. If I am not mistaken, the SuperPhoenix Powerplant installed in France in the 80s (?!) used to recycle waste into MOX and then use MOX to produce energy again… but was closed at the end of the century due to the “current low price of Uranium”…

    Anyway, I’ll keep an eye on this, thanks Ed.

  • Kiashu

    They have to make fusion reactors work before they can make fission-fusion reactors work.

    Commercial fusion has been “thirty years away” for more than fifty years, now. The longest sustained fusion reaction was achieved in 1997, it lasted half a second. More than a decade later, we’ve not improved on that. ITER hopes that after the thing’s finished building in 2016 they’ll manage up to 1,000 seconds of sustained reaction, and also hope that they can manage a single commercial power reactor by 2050.

    There will remain many technical difficulties. For example, fusion reactions produce neutron radiation which over time makes metal brittle. So the entire containment vessel would have to be replaced every few years (and the old vessel would be radioactive for a century or two afterwards). This is a fundamental physical property of fusion reactions, not a simple engineering problem.

    I think it’s always good to fund scientific research, you never know what useful stuff will show up. But it’s nothing something to get breathlessly excited over until we see actual results. Especially since it’s just a paper.

    I think it’s better to focus on what we know definitely works. If I fall off a building and someone tosses me a rope, I grab the rope rather than hoping I’ll learn to fly before I hit the ground.

  • Tim

    @Kiashu: You’re right in all you say, we are not at all close to a functionning fusion reactor and that thus any technology based on fusion should not be source of too much excitement.

    Nevertheless, and as you state it, 2050 is still far away from us and the world’s fission reactor park will definately have increased in size and if and when ITER evolves to a commercial project the switch to such a technology will never occure in less that a few decades at best. Thus having such a technology being developped in parallel could help the transition when it comes, and help us take care of the waste we have accumulated… maybe?

    Finally I am not sure I understand what you mean by focusing on what we know. I am pretty sure that dozen of projects are actually on the run with the pretention to improve existing fission- technology or treatment of radioactive-waste and even more to improve use of other source of energy.
    Talking about fusion this way does not mean that one does not search elsewhere, does-it?

  • Edouard Post author

    > Tim :

    To James Lovelock, the amalgam between nuclear weapons and nuclear plants date from the Hippie movement where people assimilated the A bomb to nuclear energy.
    (see: http://www.elrst.com/2007/12/30/the-revenge-of-gaia-by-james-lovelock/ )

    In a sense they are not totally wrong. After all:
    Nuclear plants = waste = dirty bombs and other stuff.

    Now I know that German people (and Australian, and many others) don’t like nuclear.

    I also remember talking to a hübsche kleine Fraulein who told me that nuclear was the worst thing possible and that renewables were oh so nice.

    But well, that brings me back to my old question: do we prefer coal or nuclear ? I will have to write this article I have on my mind.

    To conclude on that topic: I still don’t get why Germany is stopping its nuclear plants. After all, France got 80% of its electricity from it and nobody here got 6 fingers per hand or 3 arms. (or two heads, like Zaphod Beeblebrox 😛 )

    edit: concerning your 2nd comment you wrote while I was typing this: Agreed as well. a solution to take care of the waste we accumulated is needed. It’s like cleaning up landfills and mining them.

    This would represent a great solution and great news. To what I understood: CFNS is different from pure fusion like ITER. so perhaps it’s easier to prepare it.

    Anyway, fusion will be an energy source for the second part of the century. If we managed our current problems that is.

    > Kiashu

    Yes, indeed fusion is not ready yet, of course it still needs some work to be viable. I also totally with you, alternatives and energy efficiency and conservation have to be pursued aggressively (I loved you metaphor… thanks for the laugh)

    > both

    Thanks for your comments. You both point to ITER and I send you back to my previous article on that topic:
    http://www.elrst.com/2009/01/12/could-fusion-be-a-solution-to-our-problems/

  • Kiashu

    Tim, I didn’t say we should focus on what we know. I said that in planning solutions to our problems, we should focus on what we know works.

    For example, we know that gas, coal, oil, fission, hydro, wind, solar PV, solar thermal, tidal, and geothermal all work. Fusion and ocean power look promising in many ways, but have not been made to work yet. So when planning for the future, we should begin with the first list, and set aside the other stuff.

    Of course the first list of things which actually work, we then have to consider environmental impact, cost and so on. But we have to begin with what works – if it doesn’t work, it doesn’t matter how good or bad it is.

    “Talking about fusion this way does not mean that one does not search elsewhere, does-it?”

    Yes and no. Simple research needn’t. But what you have to realise is that we have two sciences in the world. We have science, and we have Science! Science is good and useful, Science! is the religious form. For example, some people now having seen this article about a fission-fusion reactor which eliminates fission waste will say, “see? we can do a big buildout of fission because we have a way of dealing with the waste.”

    That’s Science!, it’s where we make plans based on blind faith and hope rather than on what we actually know. Science! has a strong effect on public opinion and on government policy.

    For example, my own federal government in Australia is planning the rather unambitious target of a 5% reduction in emissions by 2020. How is it planning to achieve those? Around half the reduction is meant to come from “clean coal” – from burying the CO2 in the ground. Which no-one has been able to make work yet on a large scale. They assure us that it’ll work. But if the government said to me, “this thing you’re working on, we’re thinking of giving you $1,000,000,000 to get it going, can you make it work?” what would I reply? 🙂

    And that billion bucks could have gone to something we know works.

    So we’re planning decades ahead based on Science! Which is bound to lead to disappointments.

    We should definitely research things. I want fusion work, I want us to put people in space and on Mars, enormous colliders to study physics, people in labs working on obscure organic chemistry – I want all that stuff.

    But I also want us to take stuff that we know works well and put it into place. The danger of Science! is that it distracts us and tells us we don’t have to do anything except sit around and wait for the Magic Machine to solve everything.

    I’ll grab the rope, thanks.