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Ok so it looks like there actually was a partial meltdown in reactor unit 1 and a new situation ongoing in reactor unit 3.
Unit 3 uses a unique fuel type (MOX fuel) which requires different procedures for cooling because the plutonium component in the fuel has different neutron characteristics whereas Unit 1 can be moderated with treated water. Unit 3 is harder to cool in an emergency without the backup pumps operating. The Japanese government gave away a huge clue when they said cesium was detected in the atmosphere. Cesium isotopes are heavy and usually aren't going to be detected except in trace amounts during a SCRAM if the plant is venting coolant water to the atmosphere---radioactive iodine and krypton gas are more likely to be detected in a steam release from a BWR of this type. If a cesium spike is detected in the atmosphere it means there's a containment problem going on---not just a coolant problem. And why the name of God won't the Japanese government tell us what the state of the control rods are? Did all of them get completely pushed in? Was the meltdown severe enough that it damaged the rod channels? If that's the case then they really need to evacuate the whole Fukishima prefecture until they kill the melt. |
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Since we're talking about (partial) meltdown, this is the problem the Japanese plant engineers are fighting:
http://en.wikipedia.org/wiki/Corium_(nuclear_reactor) Corium is melted fissile products which has been turned into a liquid, making it difficult to stop the reaction (rods can't be inserted to stop it). Kind of how you microwave a bad TV dinner and parts of it are ice and parts of it are white hot... corium has the same locaized temperature variances and parts of it may still be critical which could increase temperature. Pouring a moderator (water) over uranium corium will moderate only the part of the blob the water can reach. Plutonium-uranium blended fuel solids makes it more dangerous because Pu throws off more neutrons so the fuel is going to want to stay fissile for longer, so more cooling water is needed to lower the temperature to keep the fuel in a solid state (or whatever other material is needed to moderate the neutrons if water is not the appropriate moderator). If it turns liquid it's going to be hard to keep it under control. Japan's foreign minister to the U.S. is still saying this isn't TMI, but with cesium 137 in the atmos, which normally is a liquid swimming around the fuel rods, to have this show up as particulates in a gas outside the power plant indicates meltdown and containment breach (failure of the rector vessel to keep the contaminant solids-turned-to-gases from escaping). ![]() This disaster could make the case that Thorium feeder molten salt nuclear reactors might be the better way to go. |
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BTW there's some interesting biodiversity going on in Chernobyl.
Scientists discovered radiotropic fungi which uses gamma radiation as a food source.. inside the reactor room where radioactivity is the highest. The fungi uses melanin, the same chemical humans have which reacts to UV radiation, more than chloryphyll to generate food. Major biological discovery…inside the Chernobyl reactor?? « Doug’s Darkworld |
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Here's an NYTimes slideshow that provides a basic review of the Fukushima reactor design. Unfortunately it doesn't offer a detailed view of the core itself and its geometry. You would think NBC would be able to get this information from its former parent company, since General Electric built all of these reactors.
The Crippled Japanese Nuclear Reactors - Interactive Feature - NYTimes.com The latest update is that Reactor No 1 did not have some of its control rods inserted far enough in before the steam pressure increased to a point that it exposed the fuel rods up to a meter, which caused the fuel cladding to interact with the steam. If this is true, this is the source of the hydrogen blast. When the engineers vented the reactor vessel, the pressurized hydrogen oxidized and the rapid oxidation was the source of the explosion at Reactor Unit 1. They are swearing up and down that the seawater pumping is cooling off the core and overmoderating the fuel (killing off the melt). I hope that's true. Water is a neutron moderator, so if one is not careful, water at the wrong temperature or pressure in a boiler reactor can actually accellerate a nuclear reaction, not slow it down. Reactor Unit 3 is feared to be undergoing the exact same process. If this is the case, another explosion might be likely at the plant. Hopefully the explosion will be exactly the same as Reactor 1 and sheer the roof off but leaving the reactor vessel intact, and they can depressurize the core and continue flooding it until the metals have cooled off. I wonder about the MOX fuel type though. Sea water with boric acid mixed in it can still be a problem with a reactor using plutonium in the fuel. NYT is also running a report of 2 additional nuclear reactor cooling problems on top of the Fukushima reactors running on TV. |
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Here's an NYTimes slideshow that provides a basic review of the Fukushima reactor design. Unfortunately it doesn't offer a detailed view of the core itself and its geometry. You would think NBC would be able to get this information from its former parent company, since General Electric built all of these reactors. Thanks for the updates and descriptions. |
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Well that is the Japanese goverment or ya, they rather save face then fest up. |
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Man they still tell their sheep that the US started the Pacific war. I heard this morning where the Jap PM Alos, remember things are lost in translation....So "crisis" might be the word we translate but mean something totally different. |
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Sea level has dropped five metres off Fukushima, confirming imminent arrival of tsunami - Japanese TV.
HONG KONG (MarketWatch) -- Japanese media reported Monday that a new a tsunami alert had been issued for northern cost following a 6.2-magnitude aftershock that struck mid-morning. The reports said a fire-services helicopter off Fukushima prefecture spotted a three-meter high wave heading toward the northern coast. However, Japan's Meteorological Agency and the The Hawaii-based Pacific Tsunami Warning Center did not issue tsunami warnings. Japan's Meteorological Agency said the morning's aftershock had produced minor wave action that did not warrant an alert. |
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This can't be good. BBC News - Japan earthquake: Meltdown alert at Fukushima reactor
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This can't be good. BBC News - Japan earthquake: Meltdown alert at Fukushima reactor Radiation alert: US ship contaminated 100 miles offshore |
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Late Monday, the chief government spokesman said there were signs that the fuel rods were melting in all three reactors, all of which had lost their cooling systems in the wake of Friday's massive earthquake and tsunami
"Although we cannot directly check it, it's highly likely happening," Chief Cabinet Secretary Yukio Edano told reporters. Some experts would consider that a partial meltdown. Others, though, reserve that term for times when nuclear fuel melts through a reactor's innermost chamber but not through the outer containment shell. Officials held out the possibility that, too, may be happening. Meltdown Threat Rises at Japanese Nuclear Plant - FoxNews.com |
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