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Wednesday, March 16, 2011 2:05 PM

Plutonium, MOX, and Chicken Little

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Yesterday someone called me a "Chicken Little" regarding events Japan. This brave soul bragged about living near 3-Mile Island as if it was some sort of badge of honor, yet simultaneously admitting it was no big deal.

Events in Japan go far beyond 3-Mile Island and it is well beyond foolish to think this is no big deal. None of us knows how it will play out, yet this is a major crisis with the potential to be a Chernobyl-type disaster if a MOX reactor blows.

Please consider MOX fuel rods used in Japanese Nuclear Reactor present multiple dangers

The mixed oxide fuel rods used in the compromised number three reactor at the Fukushima Daiichi complex contain enough plutonium to threaten public health with the possibility of inhalation of airborne plutonium particles. The compromised fuel rods supplied to the Tokyo Electric Company by the French firm AREVA.

Plutonium is at its most dangerous when it is inhaled and gets into the lungs. The effect on the human body is to vastly increase the chance of developing fatal cancers.

One of the unique characteristics of mixed oxide fuel is that relatively little of the plutonium in the fuel rods is used up in the fuel cycle in a reactor. “When the plutonium in the fuel rods goes into a reactor for commercial power, a very little of it is going to be consumed. I don’t know what percentage, maybe half percentage or something like that, but it’s going to generate an extraordinary amount of contamination throughout the fuel rods…,” says William Lawler, an expert on radioactive waste.

The damaged number three reactor was undergoing its first fuel cycle using MOX at Daiichi. MOX fuel was first used in a thermal reactor in 1963, but it did not come into commercial use until the 1980s. One reason proponents of MOX reactor fuel support its use is because, once the fuel is burned in a reactor, it is so hot that terrorists would not be able to steal a fuel assembly.

Lawless, who worked at the DOE’s Savannah River Site and first exposed massive contamination there in the early 1980s, says MOX being used as a way of controlling weapons proliferation is a myth: “You will decrease the amount of plutonium minutely but you will increase the amount of waste inside the fuel rod greatly into something that is very contaminated for a long period of time and they think is that it would be too deadly to handle for a terrorist…This is not necessarily following the best scientific plan or the best engineering decision; this is more a political decision, the MOX.”
Plutonium Isotopes

If one of those MOX reactors blows, spewing plutonium dust across Japan and elsewhere, it is lights out via cancer for anyone who breathes the stuff.

The half-life of various plutonium isotopes ranges from minutes to 80 million years. Plutonium-239, has a half-life of 24,100 years.

Japan’s MOx Reactor Fuel

With the above information at hand, inquiring minds are reading about Japan’s MOx Reactor Fuel
In every nuclear reactor there is both fission of isotopes such as uranium-235, and the formation of new, heavier isotopes due to neutron capture, primarily by U-238. Most of the fuel mass in a reactor is U-238. This can become plutonium-239 and by successive neutron capture Pu-240, Pu-241 and Pu-242 as well as other transuranic isotopes (see page on Plutonium). Pu-239 and Pu-241 are fissile, like U-235. (Very small quantities of Pu-236 and Pu-238 are formed similarly from U-235.)

“Normally, with the fuel being changed every three years or so, about half of the Pu-239 is ‘burned’ in the reactor, providing about one third of the total energy. It behaves like U-235 and its fission releases a similar amount of energy. The higher the burn-up, the less fissile plutonium remains in the used fuel. Typically about one percent of the used fuel discharged from a reactor is plutonium, and some two thirds of this is fissile (c. 50% Pu-239, 15% Pu-241). Worldwide, some 70 tonnes of plutonium contained in used fuel is removed when refuelling reactors each year.
Please consider Japan nuclear plant faces new threat
Shaun Burnie, an independent nuclear energy consultant and former head of nuclear campaigns at Greenpeace, said the presence of a percentage of fuel core loaded with plutonium Mox fuel in the No 3 reactor posed a grave threat to the surrounding area.

"Plutonium Mox fuel increases the risk of nuclear accident due the neutronic effects of plutonium on the reactor," Burnie told the Guardian. "In the event of an accident - in particular loss of coolant - the reactor core is more difficult to control due to both neutronics and higher risk of fuel cladding failure. In the event of the fuel melting and the release of plutonium fuel into the environment, the health hazards are greater, including higher levels of latent cancer."

The Mox fuel was delivered in 1999 and was loaded into the reactor by Tepco only last year after sitting in Fukushima storage ponds amid opposition and delays from the prefecture's governor, Burnie said.
As I mentioned earlier, accurate information is difficult to come by. Moreover, I get the distinct impression that the full story regarding the risks is not being disclosed for fear of panic.

Regardless, the odds one of these reactors completely melts spewing radioactive particles is not only non-zero but sufficiently high such that those mocking this series of events as if it was chicken little material are complete fools.

Mike "Mish" Shedlock
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