As the scale of Japan’s nuclear crisis begins to come to light, experts in Japan and the United States say the country is now facing a cascade of accumulating problems that suggest that radioactive releases of steam from the crippled plants could go on for weeks or even months.
he emergency flooding of stricken reactors with seawater and the resulting steam releases are a desperate step intended to avoid a much bigger problem: a full meltdown of the nuclear cores in reactors at the Fukushima Daiichi Nuclear Power Station. On Monday, an explosion blew the roof off the second reactor, not damaging the core, officials said, but presumably leaking more radiation.
Later Monday, the government said cooling systems at a third reactor had failed. The Kyodo news agency reported that the damaged fuel rods at the third reactor had been temporarily exposed, increasing the risk of overheating. Sea water was being channeled into the reactor to cover the rods, Kyodo reported.
So far, Japanese officials have said the melting of the nuclear cores in the two plants is assumed to be “partial,” and the amount of radioactivity measured outside the plants, though twice the level Japan considers safe, has been relatively modest.
But Pentagon officials reported Sunday that helicopters flying 60 miles from the plant picked up small amounts of radioactive particulates — still being analyzed, but presumed to include cesium-137 and iodine-121 — suggesting widening environmental contamination.
MUCH ADO ABOUT NOT MUCH: 7th Fleet repositions ships after contamination detected. “For perspective, the maximum potential radiation dose received by any ship’s force personnel aboard the ship when it passed through the area was less than the radiation exposure received from about one month of exposure to natural background radiation from sources such as rocks, soil, and the sun.”
Still, if that’s the dose received 100 miles away after wind dispersal and dissipation, it’s small wonder that the Japanese are evacuating the area near the plant. No nation has the history of radiation poisoning that Japan does, and one has to believe that this danger will loom the largest among the people even after the tsunami damage that killed thousands of people. The government will face a great deal of scrutiny for years to come for its actions in these few days, and they appear to understand that.
That’s the title of a post on the Morgsatlarge, reprinting a letter from Dr. Josef Oehman of MIT. According to his web page, his main research interest is “risk management in the value chain, with a special focus on lean product development.” Although he’s a business professor and not a nuclear scientist, his father worked in the German nuclear power industry, and the post provides a detailed and persuasive (at least to me) explanation of how the endangered Japanese nuclear power plants work, and why their multiple backup systems ensure that there will be neither an explosion nor a catastophic release of radiation. The American cable TV channels, by the way, seem to be taking a much more sober approach than they did yesterday, when Wolf Blitzer was irresponsibly raising fear of “another Chernobyl.”
John Sullivan at ProPublica:
As engineers in Japan struggle to bring quake-damaged reactors under control , attention is turning to U.S. nuclear plants and their ability to withstand natural disasters.
Rep. Ed Markey, a Massachusetts Democrat who has spent years pushing the Nuclear Regulatory Commission toward stricter enforcement of its safety rules, has called for a reassessment. Several U.S. reactors lie on or near fault lines, and Markey wants to beef up standards for new and existing plants.
“This disaster serves to highlight both the fragility of nuclear power plants and the potential consequences associated with a radiological release caused by earthquake related damage,” Markey wrote NRC Chairman Gregory Jaczko in a March 11 letter .
Specifically, Markey raised questions about a reactor design the NRC is reviewing for new plants that has been criticized for seismic vulnerability. The NRC has yet to make a call on the AP1000 reactor , which is manufactured by Westinghouse. But according to Markey, a senior NRC engineer has said the reactor’s concrete shield building could shatter “like a glass cup” under heavy stress.
The New York Times reported last week  that the NRC has reviewed the concerns raised by the engineer, John Ma, and concluded that the design is sufficient without the upgrades Ma recommended. Westinghouse maintains that the reactor is safe .
The inner doll, which looks like a gigantic cocktail shaker and holds the radioactive uranium, is the heavy steel reactor vessel. It sits inside a concrete and steel dome called the containment. The reactor vessel is the primary defense against disaster — as long as the radiation stays inside everything is fine.
The worry is that a disaster could either damage the vessel itself or, more likely, damage equipment that used to control the uranium. If operators cannot circulate water through the vessel to cool the uranium it could overheat and burn into radioactive slag — a meltdown.
Steve Mirsky at Scientific American
Maggie Koerth-Baker at Boing Boing:
This morning, I got an email from a BoingBoing reader, who is one of the many people worried about the damaged nuclear reactors at Fukushima, Japan. In one sentence, he managed to get right to heart of a big problem lurking behind the headlines today: “The extent of my knowledge on nuclear power plants is pretty much limited to what I’ve seen on The Simpsons“.
For the vast majority of people, nuclear power is a black box technology. Radioactive stuff goes in. Electricity (and nuclear waste) comes out. Somewhere in there, we’re aware that explosions and meltdowns can happen. Ninety-nine percent of the time, that set of information is enough to get by on. But, then, an emergency like this happens and, suddenly, keeping up-to-date on the news feels like you’ve walked in on the middle of a movie. Nobody pauses to catch you up on all the stuff you missed.
As I write this, it’s still not clear how bad, or how big, the problems at the Fukushima Daiichi power plant will be. I don’t know enough to speculate on that. I’m not sure anyone does. But I can give you a clearer picture of what’s inside the black box. That way, whatever happens at Fukushima, you’ll understand why it’s happening, and what it means.