Japan earthquake
Live updates of developments after the earthquake and tsunami in Japan, selected by Reuters.com editors and readers. To see updates from Reuters only, click "Options" and turn off comments.
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Reuters photographers getting closer to scene of tsunami. Amazing pictures here blogs.reuters.com
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They believe that there may be a leak. The last I heard, radiation levels are 8 times the normal amount outside the plant (note that this is nothing. It's eight times an incredibly small number. We get irradiated by other natural sources more than this). However, this could lead to polluted water and other things.
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Three Mile Island and Chernoble had drastically different outcomes. Chernoble breached the containment building and released radiation to the atmosphere. TMI was contained in the vessel. The next containment boudary was the containment building. The media is taking information pieces and sensationalizing it. Yes, there very well could be fuel damage but that doesn't mean that the reactor vessel will be compromised nor will the containment building be compromised. The purpose of these two systems is to contain a problem. The other difference between the PWR reactor and the French designed Chernoble is that the PWR will reduce fission as it heats up, instead of increasing the fission.
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Japanese nuclear authorities say there was a high possibility that nuclear fuel rods at a reactor at Tokyo Electric Power's Daiichi plant may be melting or have melted, according to Jiji news agency.
Experts have said that if the fuel rods have been damaged, it means that it could develop into a breach of the nuclear reactor vessel and the question then becomes one of how strong the containment structure around the vessel is and whether it has been undermined by the earthquake. -
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As long as there is reactor melt down, the area around that region is going to be rendered "unsafe" to stay in many years to come. The affected people in that region will and is expected to go through some very tough time. Lets hope the situation in the reactor is and will be under control.
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The danger of a meltdown comes from the fact that these incredibly hot rods come into contact with water. This makes a ton of steam, which builds up pressure in the containment structure. They've already vented some of this pressure and steam into different parts of the building. The main danger now comes from losing the plant, as in not being able to use it any more. The threat of nuclear contamination outside the barrier is pretty small compared to the damage the tsunami and quakes have caused elsewhere.
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If cesium has been detected, that means some fuel got very hot (at least 671 C) to vaporize the cesium. That doesn't happen if the fuel is all still properly underwater. So if these fragmentary reports of cesium are right, that's not good. But perhaps someone can please clarify whether this 40-year-old plant actually has a containment dome like modern ones. Some press reports say no, it has only the reactor vessel inside a building. Does someone have a spec-sheet handy for Fukushima 1 Unit 1, please?
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It's also unclear what the problem is (probably multiple). TEPCO reportedly said it had a backup generator onsite; in principle that should run the valves and controls. However, there were reports of a faulty valve (whether an automatic pressure relief valve or one that needs special operation wasn't clear). We need to await an informed announcement to start understanding what's happening.
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As long as the containment building can hold back the release of system pressure to internal atmosphere, there will be no or little contamination of the surrounding area. The danger is the plant location (The Coast) and possible structural damage to the containment building.
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The post just now that the big issue with meltdown is when molten fuel contacts water. There can be hydrogen explosions or steam explosions (like a big foundry accident) or both, and these may rupture any containment. Delphic_Dave says containment has 4-8' thick walls. Modern US reactors have that. It's not at all clear that this 1971 reactor has it, or anything like it.
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That is really to bad. I posted below that the key indicator of an approaching catastrophe would be exposure and melting of the fuel rods. When they opened the vent they must have gotten radiation indicating fuel pellet disintagration.
I tried to post these quotes from the LA times article before, but I don’t think they took.
www.latimes.com
Qoute: The reactor uses a single cooling loop and does not have a containment dome, but rather uses a smaller containment vessel around the reactor core.
"These first-generation boiling water reactors have the least margin of safety of any reactor design," said Frank N. von Hippel, a Princeton University physicist and former White House advisor. -
ロイターニュースランキング
