Several of Fukushima Daiichi's reactors are spewing radioactive material, but just one contains the even more toxic MOX fuel. Eve Conant reports on the controversial mixture of uranium and plutonium—and the likelihood of its dispersal into the air. Plus, full coverage of
Japan's nuclear crisis.
At least three reactors at Japan’s beleaguered Fukushima Daiichi plant appear to be releasing some radioactive material. But it is reactor No. 3 that, unlike the others, recently began using a special kind of mixed fuel that some scientists argue could be radically more toxic to human health if released into the atmosphere.
Japanese officials said Wednesday that smoke had been seen around the No. 3 reactor, that it may have ruptured and that the reactor was a “priority” without going into detail. High radiation levels also prevented a helicopter mission to dump water on the reactor to cool its fuel rods.
The Daily Beast spoke with half a dozen nuclear scientists about the peculiarities of MOX fuel, a mixture of uranium and plutonium—reprocessed from spent uranium and sometimes from the disposal of weapons-grade plutonium. Unlike uranium, plutonium is not naturally occurring,, and it was Berkeley scientists in the 1940s who figured out how to create it in a lab.
The bad news about plutonium: Its potential harmful effects, if absorbed by humans, are exponentially greater than that of most other elements used in nuclear processing.
The better news is that it is extremely hard to disperse.
MOX is a controversial and rarely used fuel, except in France and a handful of other countries, usually because of proliferation concerns. While some plans to fabricate MOX from weapons-grade plutonium are under way in South Carolina, the U.S. largely decided during the Ford and Carter administrations to abandon reprocessing and plutonium-based civilian nuclear energy.
The Fukushima Daiichi plant began using the fuel only in September, and its presence has been little more than a footnote in the unfolding drama in Japan. Nuclear Regulatory Commission Chairman Greg Jaczko addressed MOX at a briefing Monday, saying: “We are providing assistance to the Japanese where they request our assistance. And at this time, they have not asked for any specific information with regard to the MOX fuel.”
But some American scientists are stressing concern.
“It could change the nature of what could happen if it’s released,” said Paul Carroll. “The bottom line is that if you have an uncontrolled accident and release, then MOX fuel will raise your health and safety risks.”
“I wouldn’t call it a ‘game changer,’” said Paul Carroll, who has worked on nuclear weapons production and waste management issues for nearly 20 years in Congress, the Energy Department, and now at Ploughshares Fund, a nonproliferation organization in San Francisco. “But it could change the nature of what could happen if it’s released. The bottom line is that if you have an uncontrolled accident and release, then MOX fuel will raise your health and safety risks.”
Ed Lyman, senior staff scientist with the Union of Concerned Scientists in Washington, echoed others who have calculated that some 6 percent of the fuel in Reactor No. 3 could be MOX. This, he wrote on his blog, “generally increases the consequences of severe accidents in which large amounts of radioactive gas and aerosol are released” because it “contains greater amounts of plutonium and other actinides, such as americium and curium, which have high radio-toxicities.” Lyman estimated that long-term cancer rates resulting from an accident with a reactor filled with just 6 percent MOX could increase by at least 10 percent if a major meltdown were to occur.
But Ray Guilmette of the National Council on Radiation Protection and Measurements said that what causes damage to human health is not necessarily plutonium or uranium, but the fission materials that are most likely to escape during a meltdown, such as iodine and cesium. (He explained that iodine tablets are being issued in Japan because if the thyroid is already “loaded up” with stable iodine it won’t absorb radioactive iodine, which gets excreted in urine.) Plutonium is a much smaller threat: If it were to melt, he said he expects it would become a sludge-like substance that wouldn’t be released into the environment. But if it were absorbed in the body, “it is thousands of times more radioactive than uranium,” he said.
That likelihood is small, Guilmette said. “But the concern would be a very large explosion.” Hydrogen explosions at the first and third reactors have blown the roofs off of their secondary containment buildings; the spent fuel rods in a storage pool next to reactor No. 3 may also have lost their roof in a fire.
Donald Olander, professor emeritus of nuclear engineering at the University of California, Berkeley, said that because plutonium decays quickly, it produces radiation that can kill cells in the body more quickly. But the plutonium itself would pose a severe threat only it was involved in a violent reaction that turned it into dust particles, which could be inhaled. The length of the time the fuel has been in the reactor plays a role, as the does the mix of fuel. Plutonium can be about 4 to 8 percent of a typical MOX mix, and is also found in much smaller percentages (1 to 2 percent) in more traditional uranium reactors.
Temitope Taiwo, a nuclear engineer at Argonne National Laboratory, an Energy Department research facility near Chicago, said MOX fuel is not more volatile than typical enriched uranium, “but if that material is able to be dispersed in the atmosphere, the plutonium is much more toxic.” If workers are able to keep the system cool, he said, the probability of an explosion is low.
The real worry is cesium and iodine, said Charles Forsberg, executive director at MIT’s Nuclear Fuel Cycle Study. Even at the Chernobyl meltdown in 1986, he pointed out, cesium and iodine were the problem. Based on past experiments and experience, he said, these volatile byproducts pose the real threat to human health.
Eve Conant is a Newsweek staff reporter covering immigration, politics, social and culture issues.