MIXED REVIEWS: Plutonium produced for U.S. nuclear weapons is now headed toward use in nuclear power plants as mixed oxide fuel.
Image: U.S. Department of Energy
-
The Best Science Writing Online 2012
Showcasing more than fifty of the most provocative, original, and significant online essays from 2011, The Best Science Writing Online 2012 will change the way...
Read More »
The nuclear reactors at the Fukushima Daiichi power station in Japan that were crippled by the March 11 earthquake and tsunami are a lot like reactors in the U.S. They are a common, if not exactly modern, General Electric design that harnesses nuclear fission to boil water and drive steam turbines to generate electricity. The same reactor designs and containment system are in use across the U.S., for instance at the Browns Ferry Nuclear Plant near Athens, Ala., and the Vermont Yankee facility in Vernon, Vt.
But reactor No. 3 at Fukushima Daiichi, one of the units that has experienced severe problems in the past two weeks, has one characteristic that differentiates it from its neighboring reactors and from any operating reactor in the U.S. Among the hundreds of standard nuclear fuel assemblies in its core, which rely on the splitting of uranium atoms to release energy, are some that contain a mix of uranium and plutonium. This so-called mixed oxide, or MOX, fuel was loaded into Fukushima Daiichi reactor No. 3 in 2010 and has found use in several other countries' power plants as well. And a big-budget U.S. government project is scheduled to begin producing MOX for domestic utilities in 2016.
But, as with most issues relating to nuclear energy, the use of MOX is a source of some controversy. Proponents say that burning MOX in nuclear reactors is a sensible way to dispose of weapons-grade plutonium from Cold War nuclear stockpiles, as the U.S. plans to do with 34 metric tons of surplus plutonium at its planned Mixed Oxide Fuel Fabrication Facility (MFFF) in South Carolina. (Some countries also reprocess spent nuclear power plant fuel to produce MOX.) Critics say that MOX is riskier than standard fuel and that there are better ways to dispose of excess plutonium.
"I think it's a magnificent solution," says David Jones, senior vice president for the back-end business group at Areva, a Paris-based nuclear fuel manufacturer with U.S. headquarters in Bethesda, Md. Areva is half of a partnership that is the prime contractor to the U.S. Department of Energy (DoE) on the $5-billion MFFF project. "You're taking something that was designed to be dangerous, and you're turning it into something that benefits society," Jones says.
Ordinary low-enriched uranium fuel contains primarily uranium 238, the most common natural isotope of the element, along with about 5 percent uranium 235, a rarer isotope that splits, or fissions, more readily. MOX fuel, on the other hand, substitutes plutonium 239 as the fissionable component, reducing the need for uranium 235.
"It's a fairly well established technology, especially overseas," says Jess Gehin, a nuclear science and engineering researcher at Oak Ridge National Laboratory, where MOX fuel rods have undergone testing. "All of our analyses show that it can be used without significant differences to uranium dioxide."
But Robert Alvarez, a senior scholar at the Institute for Policy Studies, a Washington, D.C., think tank, says that MOX is not the best way to irreversibly render plutonium unsuitable for weapons use. "If you really want to pursue the path of irreversibility, there are probably cheaper, easier ways to do it," he says. One way would be to blend the plutonium down to a low concentration and put it in the DoE's Waste Isolation Pilot Plant in the New Mexico desert. With the price tag attached to the MFFF, "it's certainly not something you'd think you could make money off," Alvarez says. "I kind of see it as a nuclear equivalent to a bridge to nowhere."
And Edwin Lyman, senior scientist for global security at the Union of Concerned Scientists in Washington, D.C., argues that MOX is more likely to cause nuclear accidents than ordinary uranium fuel and is liable to release more harmful material in the event of an accident. "Plutonium has different properties than uranium 235 that generally tend to degrade some of the safety systems in nuclear plants," Lyman says. For instance, because weapons-grade plutonium fissions more readily than uranium 235, reactors may need more robust control rods—neutron absorbers that shut down the nuclear chain reaction when inserted into a reactor's core. "You never get quite as much margin even after doing all that as you do with uranium," Lyman says.
Jones counters that MOX has a proved track record. "You'll hear some folks say that MOX is experimental," he says. "Over 6,000 MOX assemblies have been safely used in reactors around the world." Jones notes that MOX has passed muster with several different regulatory bodies in Europe and Japan, where the fuel has found use in dozens of nuclear power plants. "They found that it does not pose a significant, unacceptable level of risk," he says.
Lyman authored a study in 2001 in Science & Global Security showing that radioactive leakage from a meltdown with MOX fuel, which in addition to plutonium has higher levels of radioactive isotopes such as americium 241 and curium 242, would be deadlier than a low-enriched uranium meltdown. "Because plutonium is so much more radiotoxic than many of the other radionuclides, even if it's released in relatively small concentrations it can have an impact on the effects," Lyman says. He adds that it is not possible at the moment to identify how much the MOX fuel in Fukushima reactor No. 3 has contributed to the radioactive plumes emanating from the plant.
Oak Ridge's Gehin argues that the flavor of nuclear accident is more important than the flavor of fuel in the reactor. "The uncertainty of what would happen [in an accident] is not driven by MOX fuel versus uranium dioxide," he says. "It is driven in what happens in the event itself."
And Jones points out that low-enriched uranium fuel and MOX fuel become more similar as the fuel is consumed in fission reactions. "Folks try to cast a pall over MOX fuel because it has plutonium in it," he says. "We're trying to make sure people understand that uranium fuel, once it goes in the reactor, starts producing plutonium as well as fissioning plutonium and generating energy from it."
Even reactors loaded with straight uranium fuel, such as those in the U.S., end up with a mix of radioactive elements in the core, essentially a lower-plutonium version of MOX. "I don't know why people keep trying to make MOX an issue, because every reactor in the world burns MOX fuel," Jones says. "It goes in as uranium fuel, but once it starts going it has plutonium in it."
Even as the South Carolina fabrication plant progresses toward start up, the future of MOX fuel remains somewhat uncertain in the U.S. "The DoE still can't find a utility that's willing to take this stuff," Alvarez says. Duke Energy had signed an agreement with the DoE to load four of its reactors with MOX fuel, but the utility let the contract lapse in 2008. The federally owned Tennessee Valley Authority (TVA), which operates the Browns Ferry Nuclear Plant and two other nuclear facilities, has expressed some interest in trying MOX and may step up to take fuel from the MFFF. But Lyman questions whether even TVA will be a willing taker. "I don't see why any utility, even a government-owned one like TVA, would want to dabble with this stuff," he says.
See what we're tweeting about
9 Comments
Add CommentThe second and third paragraphs from the end say it. I'll say it again--once Uranium Oxide fuel is put into the reactor (and it is operating) the all-Uranium fuel will now contain Plutonium due to U-238 capturing a neutron and transmuting to Pu-239. I believe that after about 3 years of use, when the fuel would be removed, most of the power generation is actually from Pu. You cannot escape Pu by fueling with U only!
Reply | Report Abuse | Link to thisBernie Cohen once challenged Ralph Nader to eat as much caffeine as he ate in plutonium. That shut Nader up and sent him running with his tail between his legs.
Reply | Report Abuse | Link to this"...During the Manhattan Project in 1944 and 1945, 26 men accidentally ingested plutonium in quantities that far exceeded what is now considered to be a lethal dose. Since there has been a consistent interest in the health effects of this brand new substance (first discovered by Glenn Seaborg's team at the University of California in 1940), these men were closely tracked for medical studies.
Forty Years Later:
As of 1987, more than four decades later, only four of the workers had died and only one death was caused by cancer. The expected number of deaths in a random sample of men the age of those in the group is 10. The expected number of deaths from cancer in a similar group is between two and three..."
http://www.atomicinsights.com/may95/plutonium_eff.html
QUANTUM ENERGETICS - THERE IS AN ALTERNATIVE TO THE NUCLEAR POWER PLANTS
Reply | Report Abuse | Link to thisVladimir Leonov
There are now over 440 commercial nuclear power reactors operating in 30 countries. It's 440 nuclear bombs. 1986 - Chernobyl, 2011 – Fukushima. Who will be next? Large earthquakes occur every 20 years. The mankind can to disappear in 200 years.
Leonov V. S. Quantum Energetics. Volume 1. Theory of Superunification. Cambridge International Science Publishing, 2010, 745 pages.
http://leonov.inauka.ru/
Quantum energetics is based on new fundamental discoveries of quantum of space-time (quanton) and super-strong electromagnetic interaction (SEI) made by Vladimir Leonov in 1996. On the basis of new fundamental discoveries the theory of Superunification of fundamental interactions of electromagnetism, gravitation, nuclear and electro-weak forces is completed. It is important that new fundamental discoveries have the widest practical application in the development of quantum energetics. It is discovered that the single source of energy in the Universe is the quanton in the structure of quantized space-time, which is the carrier of super-strong interaction (SEI). All known methods of energy generation (chemical and nuclear reactionsm etc.) are redued to the release and transformation of SEI energy. Quantum energetics is a more general concept in energetics, which includes both the new energetic cycles, and traditional ones, including nuclear energetics.
The theory of Superunification is confirmed experimentally: Leonov effect, Usherenko effect and other.
LEONOV EFFECT.
Results of the tests of a quantum engine for generating thrust without the ejection of reactive mass. http://inauka.ru/blogs/article104833.html
In two years of experimental work it was possible to increase the thrust from 0.1 N to 500 N with the mass of apparatus being 50 kg together with the chassis. The diameter of the apparatus of was 1.5 m, the height 1.05 m together with the chassis. Unusual even for the author was to observe the motion of the apparatus which has no screws, jet nozzle and drive for the wheels. High stability is typical of the work of the quantum engine.
USHERENKO EFFECT
In 1974 the Belorussian scientist Sergey Usherenko discovered the effect of the ultradeep penetration (UDP) of particle-strikers of micron sizes in solid targets with the release of colossal energy in the channel of the target.
Leonov V.S., Russian Federation patent No. 220 1625, A method of generation of energy and a reactor for this purpose, Bull. 9, 2003.
Hmm. Business type with a large financial stake says A, scientist who is not financially involved says B. Who do you believe? Tough question.
Reply | Report Abuse | Link to thisPlutonium is such a dangerous substance that it is time to decomission all nuclear submarines that carry the stuff. Imagine a nuclear submarine sinking in miles-deep oceans. The risk of plutonium leaks in the long term is inevitable. Plutonium is a very nasty substance that military authorities have forced people to make with tax-subsidised electricity schemes that are not economical if all the hidden costs are factored in.
Reply | Report Abuse | Link to thisStevie - Deep ocean is the safest place for plutonium because the saltwater will absorb all of the radiation and prevent any significant damage. If the sub were to sink in shallow water then it could cause some real damage to the ecosystem. It all depends on life density in the area.
Reply | Report Abuse | Link to thisBurning the plutonium in MOX form in nuclear reactors will not reduce the radioactivity burden. The radioactivity in the by products of this burning will be more than what we started with. So what we actually have is an increase in the total amount of radioactivity that will have to be managed.
Reply | Report Abuse | Link to thisThe only advantage may be in the half lives of the by products of MOX fuel burning. Can someone enlighten me on this subject ? What are the principal radioactive by products of MOX fuelled reactors ? What are their half lives ?
"There are now over 440 commercial nuclear power reactors operating in 30 countries. It's 440 nuclear bombs. 1986 - Chernobyl, 2011 – Fukushima. Who will be next? Large earthquakes occur every 20 years. The mankind can to disappear in 200 years."
Reply | Report Abuse | Link to this440 nuclear bombs? You honestly do not understand nuclear reactors do you? When a reactor has a "meltdown" it doesn't go boom like a bomb, it overheats. It will never go bang as it doesn't have a high enough concentration to. This typically requires higher concentrations than anything we put into a reactor. Now, when it melts down, it is do to the uncontrolled via fission. This will typically exceed the temperature threshold of most containment vessels. In Chernobyl it was a human error. Most reactors are 100 times safer than that one. In canada, we have double automatic kill mechanisms in the case of a meltdown. Both a control rod and a control fluid that can kill the reactor in under 2 seconds. These do not require an electrical mechanism and will kick in automatically without human intervention.
Yes a major earthquake occurs every 20 years, heres a solution, don't build it near fault lines durrrrr... or build it to withstand an earthquake? Just like we built them to withstand getting hit by a 747?
also wtf are you talking about near the end...
http://en.wikipedia.org/wiki/File:ThermalFissionYield.svg
Reply | Report Abuse | Link to thisShows a bit of the daughter product proportions for different fission elements. It is actually nearly the same daughter products as uranium.
As for the comment on reducing the amount of radioactivity it depends on how you look at it. What is worse, long lived isotopes or short lived? Long lived ones stay mildly radioactive (you can pick up deweaponized uranium and not instantly get cancer), or is it better to have isotopes that degrade within 10 years but release the same amount of radiation over the time period?
I personally think these short lived isotopes are the best idea due to the thermal recovery you can have from them so it is an additional amount of energy. We also need to build reactors that can process these isotopes and get more energy from them.