June 22, 2006
Thorium Nuclear Reactor Designs Advancing

The use of thorium to power nuclear reactors holds out the prospect of a huge reduction in nuclear wastes, a nuclear fuel cycle that is much more proliferation resistant, lower costs, and a fuel that is many times more plentiful than uranium. Australian science writer Tim Dean examines the prospects for thorium reactors in a recent article and finds two avenues of technological advance that might make thorium powered nuclear reactors feasible. The more immediately promising approach uses a mixture of thorium with other radioactive materials.

The main stumbling block until now has been how to provide thorium fuel with enough neutrons to keep the reaction going, and do so in an efficient and economical way.

In recent years two new technologies have been developed to do just this.

One company that has already begun developing thorium-fuelled nuclear power is the aptly named Thorium Power, based just outside Washington DC. The way Thorium Power gets around the sub-criticality of thorium is to create mixed fuels using a combination of enriched uranium, plutonium and thorium.

At the centre of the fuel rod is the 'seed' for the reaction, which contains plutonium.

Wrapped around the core is the 'blanket', which is made from a mixture of uranium and thorium. The seed then provides the necessary neutrons to the blanket to kick-start the thorium fuel cycle. Meanwhile, the plutonium and uranium are also undergoing fission.

The primary benefit of Thorium Power's system is that it can be used in existing nuclear plants with slight modification, such as Russian VVER-1000 reactors. Seth Grae, president and chief executive of Thorium Power, and his team are actively working with the Russians to develop a commercial product by the end of this decade. They already have thorium fuel running in the IR-8 research reactor at the Kurchatov Institute in Moscow.

The potential to use existing reactors to burn thorium lowers the barrier to use of thorium. Success in existing reactors could catalyze the construction of new reactors designed to use thorium from their start.

He also goes over Carlo Rubbia's proposal to use a particle accelerator to shoot a stream of protons into a thorium reactor.

AN ALTERNATIVE DESIGN does away with the requirements for uranium or plutonium altogether, and relies on thorium as its primary fuel source. This design, which was originally dubbed an Energy Amplifier but has more recently been named an Accelerator Driven System (ADS), was proposed by Italian Nobel physics laureate Carlos Rubbia, a former director of one of the world's leading nuclear physics labs, CERN, the European Organisation for Nuclear Research.

An ADS reactor is sub-critical, which means it needs help to get the thorium to react. To do this, a particle accelerator fires protons at a lead target. When struck by high-energy protons the lead, called a spallation target, releases neutrons that collide with nuclei in the thorium fuel, which begins the fuel cycle that ends in the fission of U-233.

Governments should accelerate research into new nuclear reactor designs that promise to lower wastes and reduce costs.

Share |      Randall Parker, 2006 June 22 09:48 PM  Energy Nuclear

William Wood said at June 23, 2006 3:03 AM:

There's an excellent article summarising the ADS technology and some of the benefits at an Australian science magazine site - www.cosmosmagazine.com (in the features section).

K said at June 23, 2006 10:54 AM:

Wonderful news if it works. And I think it will.

Thorium is plentiful and avoids many of the problems of nuclear power. Only it didn't quite work - a trait that is often considered a big problem.

Paul Dietz said at June 23, 2006 11:43 AM:

Thorium could be useful if it enables reactors to go longer between refuelings, by achieving higher burnup with in situ production of more fissionable material. This would reduce fuel fabrication cost and the volume of the spent fuel, reducing disposal costs.

The ability to avoid the cost of uranium is not useful now and will not be useful anytime soon. While uranium prices have increased recently, the cost of uranium is still very low, and is nowhere near the level that would justify reprocessing. If the thorium fuel cycle requires reprocessing, it will be little more than a curiosity in the foreseeable future.

The thorium cycle has some problems with wastes. 233U is quite a bit more dangerous than 235U (much higher alpha activity), and it's potentially much more mobile in the environment than plutonium. The 232U contaminant is very dangerous (due to its short halflife), and would make the produced uranium even more alpha-active than reactor-grade plutonium.

CANDU reactors can use thorium fuel elements, with a complex online rearrangement of the fuel elements to even out breeding and burning. As far as I know no CANDU operator has elected to use thorium.

James Bowery said at June 23, 2006 11:54 AM:

No one has yet dealt adequately with the geopolitical ramifications of widespread use of nuclear power plants. The biggest problem is nuclear weapons deployed under false-flag.

Dezakin said at June 27, 2006 10:24 PM:

I'm extremely skeptical of ADS. Its an excellent way to be exceedingly paranoid about an impossible event in many modern reactors and in the process double the cost of the reactor.

If you could get the accelerator to be very cheap you could use it for excess neutron production so you can do a single fluid molten salt reactor without protactinum partioning to mitigate some proliferation risk, but I sort of doubt you would be able to make it compete on cost.

Sam said at June 30, 2006 9:17 AM:

James read up on the thorium based nuclear tech. With those types of plants there is not an issue of weapons and proliferation.

Paul Dietz said at August 31, 2006 9:13 AM:

James read up on the thorium based nuclear tech. With those types of plants there is not an issue of weapons and proliferation.

Of course there is a risk. You will either have something where the uranium is mostly 233U, which could be easier to enrich (stripping the 232U) to a purity level for weapons than natural uranium would be, or you will have denatured it with 238U, in which case there is plutonium present, just as in conventional reactors.

Kirk Sorensen said at February 16, 2007 1:54 PM:

Separating U-233 from U-232 by enrichment would be virtually impossible. Not only is there a very small mass difference between them, but the U-232 would be decaying rapidly and spraying the enrichment facility with hard gamma rays, killing everyone who wasn't behind a few feet of lead. Enrichment facilities aren't shielded, since natural uranium (U-235 and U-238) decays extraordinarily slowly over billions of years, and decays by emitting easily-shielded alpha particles. The enrichment facility would then be ruined for any future use with natural uranium because of U-232 contamination, and would have to be abandoned, at a loss of hundreds of millions of dollars.

Even terrorists aren't that stupid.

reuben archilla said at February 11, 2010 1:05 PM:

Just read the article in WIRED entitled THE NUKE about energy from Thorium reactors which appears to hold great promise for clean and abundant energy well into the future. I was encouraged to learn that there is legislation cosponsored by Orrin Hatch and Harry Reid in the Senate to provide funds at the Dept of Energy for research into Thorium reactors. With all the controversy about climate change now claiming so much media time, why isn't there more discussion about this potentially green solution for energy independence?

G.Abhiram said at June 6, 2011 4:52 AM:

By the proporsal of carlo rubia about fuel generation in thorium reactor & it will generatre nearly 675 mwts of power in the action.why we are not using this system.

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