Posted on 12/17/2012 8:27:22 PM PST by neverdem
The element thorium, which many regard as a potential nuclear "wonder-fuel", could be a greater proliferation threat than previously thought, scientists have warned.
Writing in a Comment piece in the new issue of the journal, Nature, nuclear energy specialists from four British universities suggest that, although thorium has been promoted as a superior fuel for future nuclear energy generation, it should not be regarded as inherently proliferation resistant. The piece highlights ways in which small quantities of uranium-233, a material useable in nuclear weapons, could be produced covertly from thorium, by chemically separating another isotope, protactinium-233, during its formation.
The chemical processes that are needed for protactinium separation could possibly be undertaken using standard lab equipment, potentially allowing it to happen in secret, and beyond the oversight of organisations such as the International Atomic Energy Agency (IAEA), the paper says.
The authors note that, from previous experiments to separate protactinium-233, it is feasible that just 1.6 tonnes of thorium metal would be enough to produce 8kg of uranium-233 which is the minimum amount required for a nuclear weapon. Using the process identified in their paper, they add that this could be done "in less than a year."
"Thorium certainly has benefits, but we think that the public debate regarding its proliferation-resistance so far has been too one-sided," Dr Steve Ashley, from the Department of Engineering at the University of Cambridge and the paper's lead author, said.
"Small-scale chemical reprocessing of irradiated thorium can create an isotope of uranium – uranium-233 – that could be used in nuclear weapons. If nothing else, this raises a serious proliferation concern."
Thorium is widely seen as an alternative nuclear fuel source to uranium. It is thought to be three to four times more naturally abundant, with substantial deposits spread around the world. Some countries, including the United States and the United Kingdom, are exploring its potential use as fuel in civil nuclear energy programmes.
Alongside its abundance, one of thorium's most attractive features is its apparent resistance to nuclear proliferation, compared with uranium. This is because thorium-232, the most commonly found type of thorium, cannot sustain nuclear fission itself. Instead, it has to be broken down through several stages of radioactive decay. This is achieved by bombarding it with neutrons, so that it eventually decays into uranium-233, which can undergo fission.
As a by-product, the process also produces the highly radiotoxic isotope uranium-232. Because of this, producing uranium-233 from thorium requires very careful handling, remote techniques and heavily-shielded containment chambers. That implies the use of facilities large enough to be monitored.
The paper suggests that this obstacle to developing uranium-233 from thorium could, in theory, be circumvented. The researchers point out that thorium's decay is a four-stage process: isotopically pure thorium-232 breaks down into thorium-233. After 22 minutes, this decays into protactinium-233. And after 27 days, it is this substance which decays into uranium-233, capable of undergoing nuclear fission.
Ashley and colleagues note from previously existing literature that protactinium-233 can be chemically separated from irradiated thorium. Once this has happened, the protactinium will decay into pure uranium-233 on its own, with little radiotoxic by-product.
"The problem is that the neutron irradiation of thorium-232 could take place in a small facility," Ashley said. "It could happen in a research reactor, of which there are about 500 worldwide, which may make it difficult to monitor."
The researchers note that from an early small-scale experiment to separate protactinium-233, approximately 200g of thorium metal could produce 1g of protactinium-233 (and therefore the same amount of uranium-233) if exposed to neutrons at the levels typically found in power reactors for a month. This means that 1.6 tonnes of thorium metal would be needed to produce 8kg of uranium-233. They also point out that protactinium separation already happens, as part of other chemical processes.
Given the need for access to a research or power reactor to irradiate thorium, the paper argues that the most likely security threat is from potential wilful proliferator states. As a result, the authors strongly recommend that appropriate monitoring of thorium-related nuclear technologies should be performed by organisations like the IAEA. The report also calls for steps to be taken to control the short-term irradiation of thorium-based materials with neutrons, and for in-plant reprocessing of thorium-based fuels to be avoided.
"The most important thing is to recognise that thorium is not a route to a nuclear future free from proliferation risks, as some people seem to believe," Ashley added. "The emergence of thorium technologies will bring problems as well as benefits. We need more debate on the associated risks, if we want a safer nuclear future."
The researchers are: Dr Stephen F. Ashley and Dr. Geoffrey T. Parks from the University of Cambridge; Professor William J. Nuttall from The Open University; Professor Colin Boxall from Lancaster University; Professor Robin W. Grimes from Imperial College London.
Copies of the comment piece in this week's Nature are available on request. Interviews with Dr Steve Ashley can also be arranged by contacting Tom Kirk.
More information: Nuclear energy: Thorium fuel has risks, DOI: 10.1038/492031a
Journal reference: Nature
It these bed wetters were around when mankind discovered fire we’d all still be naked and freezing in the dark.
Ping
lol, well said!
How does one make a bomb from uranium 233? Has it ever been done?
Yeah. Except the operators of such a clandestine plant would be dead 1000 times over from gamma ray exposure. That’s the rub with Thorium, which in all other respects looks excellent as a power source. There is much less waste, but what there is, is powerful and much more radioactive by gamma radiation than U-process waste. That type of radiation is far more damaging to tissue than alpha radiation or neutron radiation.
Zinger and at the same time profound and true. Well said. ;-)
Same way as a U-235 device. Don't know if it has ever actually been done. Most stuff uses either U-235 or plutonium.
How very true. Someone messes his drawers an everyone has to wear a diaper.
I don’t know your background obviously but this statement is so overly simplistic as to completely incorrect.
Radiation damages tissue because it carries energy and that energy can be transferred to atoms in the tissue of the body changing the chemical properties of the molecules to which those atoms belong. The more energy the radiation carries the more damage it will cause.
Gamma radiation is far more penetrating than alpha or neutron radiation but also carries far less energy than the other two.
Alpha radiation will not penetrate the dead layers of skin on the body but will do far more damage to tissue than gamma or neutron radiation if the source of the radiation is inside the body (radioactive material swallowed inhaled or absorbed through the skin).
Neutron radiation is more penetrating alpha radiation; it will penetrate the skin and carries far more energy than gamma radiation. Neutrons can also do double damage. A neutron can bounce around ricocheting off of Hydrogen atoms in the cells of the body transferring energy to those atoms causing damage to the cells they are a part of. Finally it is absorbed in to an atom possibly changing that atom from one element to another. It is also likely that the new atom will be radioactive itself. This new radioactive atom is inside the body where it will maximize the damage it can do.
But you left out Beta radiation entirely. Beta radiation is between gamma and neutron in energy level. Beta radiation is more penetrating than alpha but far less than neutron. Some Beta radiation can generate gamma radiation if it strikes a metal object so someone designing components to process nuclear material must take this in to consideration.
Read the comments after the article for the rebuttals.
The fact is that any nation-state that wants to can produce nuclear weapons. If North Korea can do it, anyone can. Thorium reactors aren’t a realistic risk in this regard. As someone pointed out in the comments, anyone with a neutron source can pursue the same process without a reactor.
The world needs clean, safe energy in abundance, and thorium reactors are the most promising high density source. What we need to do is avoid the insanity of dotting the landscape with wind turbines. That is very likely to be a fad leaving thousands of rusting, expensive eyesores for all of us to “enjoy”.
Until highschool girls get off their boney asses and learn some science it ain’t going to happen. Peace symbol T shirts trump any rational discussion involving ununderstandable facts.
Now that they've explained how to do it, can't they make the bomb even without Thorium reactors?
Read something interesting in a book about the effects of nuclear radiation. A dosage which will kill if received in an hour might not kill at all if you got in a year
Also, If you get a fatal dosage, say one that will kill you in 3 days, the number of cells in your body actually affected would be something like this: Expose 200 people in the US to some agent, 3 days later everyone in the country is dead!
Pretty scary stuff.....
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