Yes, there is a risk that plutonium, the most deadly of the nuclear fuels, could "get out." What do we know about it, particularly with respect to the reactors of Fukushima Daiichi?
Plutonium is indeed nasty stuff, especially damaging to lungs and kidneys. It is also less stable than uranium and can more easily spark a dangerous nuclear chain reaction.
But plutonium, like uranium, is a heavy element that is not easily dispersed in the air. It is the other byproducts of nuclear power generation, such as radioactive forms of cesium and iodine, that are more prone to spread and cause widespread contamination.
Ed Lyman, a physicist at the activist group Union of Concerned Scientists, estimates the fuel in Unit 3 is 5 percent to 10 percent more dangerous than the fuel in the other crippled reactors. ...NYT
For plutonium to get out and do some damage, it would have to reach "critical mass." The possibility of critical mass occurring in the Japanese nuclear plant isn't likely. But it's being discussed in blogs and in some mainstream media. Rachel Maddox raised the issue last night during a series of discussions on her show about fuel rods. More power to her and her efforts to clarify the science of nuclear power generation, but she leaves an inevitable trail of doubt and speculation.
As for the current situation in Japan, the plutonium "is very unlikely to become packed tightly enough to reach what is known as critical mass and start a chain reaction. The plutonium would qualify as weapons grade only if a large quantity was packed together," according to the Times report.
Still, the spectre of a plutonium escape was raised early on by the Economist and is discussed in the Times report this morning in connection with efforts to cool the spent fuel rods at Fukushima Daiichi.
The Fukushima Dai-ichi site has a considerable number of fuel rods on hand, according to information provided Thursday by Toyko Electric Power Co., which owns the atomic complex: There are 3,400 tons of fuel in seven spent fuel pools within the six-reactor plant, including one joint pool storing very old fuel from units 3 and 4. There are 877 tons in five of the reactor cores. Officials have said that the fuel in Unit 4's reactor vessel was transferred to its spent fuel pool when the unit was temporarily shut in November.
If plutonium did get out, it wouldn't disappear quickly. Plutonium-239 has a half-life of 25,000 years, meaning it takes that long to lose half of its radioactive potency. Uranium-235 has a half-life of 700 million years. And cesium, which tends to go airborne much more easily, has a half-life of 30 years. ...NYT
The risk of plutonium "getting out" comes, also, from a process used in Japan which is generally frowned upon by other nations. The spent fuel in the fuel rods is removed and processed for reuse, increasing the possibility of an accident or of the recovered plutonium being used to make nuclear weapons.
How much do we know -- how much can we know -- about what's really happening in Japan? Are we being told everything? Not likely, according to Michael Hirsh reporting yesterday at National Journal.
Whatever is being communicated is meager and seemingly reluctant. Earlier in the week, foreigners had to rely on the U.S. Navy for comprehensive radiation readings offshore far more than the Japanese government itself or the Tokyo Electric Power Co., which runs the most damaged reactors. “Now outsiders, local governments, and prefectures are doing radiation monitoring,” said [nuclear inspector David] Albright. “But there’s no system that says what radiation doses are occurring in evacuation zones or outside. It’s hit and miss. They didn’t have a joint crisis center going until Tuesday. They really have done themselves a disservice, because now is when they need the people’s trust.”
There are few countries where maintaining nuclear credibility is more important than in Japan. It’s a little-known fact that for many years, Japan has been the chief surveillance target of the International Atomic Energy Agency, whose mission is to track plutonium and enriched uranium used by the 143 signatories to the Nuclear Non-Proliferation Treaty so that it isn't diverted to weapons and doesn't end up in the hands of terrorists, thieves, or unscrupulous traders.
It comes right back to the worries about plutonium.
Japan has, by all accounts, always been cooperative with IAEA inspectors. But the reason for this extensive surveillance is that Japan has such a huge civilian nuclear program, and because it is still largely plutonium-fueled, the country has huge stockpiles of the stuff, far more tons than any country except the major nuclear powers Russia and the United States. “They’re separating too much plutonium they can’t use,” said Albright.
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At this hour, AP has the latest risk assessments even as a new power line is reaching the plant to power the cooling process.
— ATTEMPTS TO COOL REACTORS: Military fire trucks spray seawater for a second day on the stricken Fukushima Dai-ichi nuclear complex in a desperate attempt to prevent its fuel from overheating and spewing dangerous radiation. A U.S. military fire truck joins six Japanese vehicles, but is apparently driven by Japanese workers. Japanese air force says some water appears to be reaching its target.
— SEVERITY LEVEL OF ACCIDENT RAISED: Japan's nuclear safety agency raises the rating of the nuclear accident from 4 to 5 on a 7-level international scale, making it the same as the U.S. Three Mile Island nuclear accident in 1979. Four of the six reactor units at the Fukushima plant have experienced fires, explosions or partial meltdowns since last Friday's 9.0-magnitude quake and tsunami knocked out power to cooling systems.
— IAEA CALLS ACCIDENT "EXTREMELY SERIOUS." The head of the U.N.'s International Atomic Energy Agency says authorities are "racing against the clock" to cool the complex and calls the accident "extremely serious."
