Japan is having trouble cooling down five nuclear reactors at two power plants after a massive 8.9 earthquake struck near the east coast of Honshu, Japan yesterday. After the quake struck, “the plants immediately shut down, but the cooling systems failed, leading to a dangerous build-up of radioactive steam.” The Japanese government responded by evacuating people living around both the Fukushima Daiichi and the Fukushima Daini nuclear power plants. Most recently, an explosion was reported from the Fukushima Daiichi nuclear power plant. As a result of the situation at both plants, Japan may hand out potassium iodine near nuclear plants to limit the intake of radioactive material by the thyroid. Updates on the situation at Japan’s Fukushima nuclear power plants can be found with Kate Sheppard at Mother Jones. More on the explosion at the Fukushima Daiichi plant via NPR:
NPR’s Jon Hamilton tells us it was NOT a nuclear explosion. Images from the scene show one building was destroyed. The Associated Press reports that the blast “tore down the walls of a building Saturday.”
Reuters says that:
“A nuclear industry body official said on Saturday he believed a blast at a Japanese atomic power plant was due to hydrogen igniting, adding it may not necessarily have caused radiation leakage. ‘It is obviously an hydrogen explosion … due to hydrogen igniting,’ Ian Hore-Lacy, communications director at the World Nuclear Association, a London-based industry body, told Reuters after reports of the explosion in Japan.”
And the AP adds that: ” ‘meltdown’ is not a technical term. Rather, it is an informal way of referring to a very serious collapse of a power plant’s systems and its ability to manage temperatures. It is not immediately clear if a meltdown would cause serious radiation risk, and if it did how far the risk would extend. Yaroslov Shtrombakh, a Russian nuclear expert, said a Chernobyl-style meltdown was unlikely. ‘It’s not a fast reaction like at Chernobyl,’ he said. ‘I think that everything will be contained within the grounds, and there will be no big catastrophe.’ “
More on what happens during a meltdown at a nuclear power plant via the BBC:
You can think of the core of a Boiling Water Reactor (BWR), such as the ones at Fukushima Daiichi, as a massive version of the electrical element you may have in your kettle.
It sits there, immersed in water, getting very hot.
The water cools it, and also carries the heat away – usually as steam – so it can be used to turn turbines and generate electricity.
If the water stops flowing, there is a problem. The core overheats and more of the water turns to steam.
The steam generates huge pressures inside the reactor vessel – a big, sealed container – and if the largely metal core gets too hot, it will just melt, with some components perhaps catching fire.
In the worst-case scenario, the core melts through the bottom of the reactor vessel and falls onto the floor of the containment vessel – an outer sealed unit.
This is designed to prevent the molten reactor from penetrating any further. Local damage in this case will be serious, but in principle there should be no leakage of radioactive material into the outside world.
More on the importance of potassium iodine via ABC News:
“Any attempt to make it seem that this is not the worst case imaginable is foolhardy,” said Edwin Lyman, a senior scientist with the Union of Concerned Scientists.
Both the U.S. and France have plans in place to distribute doses of stable potassium iodine to children who live in the vicinity of a nuclear power plant in the event of a catastrophic radiation release. Lyman said he did not know whether Japan had similar plans in place.
If the reactor core melts through the steel vessel that is housing it, Lyman said, the risk Japan faces is a radioactive plume that could disperse tens or even hundreds of miles. “You could have large swaths of areas that will need severe remediation. And a lot of people exposed to radioactivity who will have an increased chance of cancer.”
After the nuclear accident at Chernobyl, Lyman said there were over 6,000 cases of childhood thyroid cancers, and it was later determined if the children had taken stable iodine a few hours before being exposed to the radiation it would block the intake of the radioactive material in the thyroid. “That has been shown to reduce exposure significantly,” he said.
UPDATE 1 (14 March 11): There’s been another explosion at the troubled Fukushima Daiichi nuclear power plant. This time, the explosion “ripped through Unit 3 of the Fukushima Dai-ichi Nuclear Power Station.” The first explosion occurred at the plant’s Unit 1 reactor.
UPDATE 2 (15 March 11): According to the BBC, after a third blast at the Fukushima Daiichi nuclear plant that may have damaged a reactor’s containment systems, “radiation from Japan’s quake-stricken Fukushima Daiichi nuclear plant has reached harmful levels.”
