From my limited understanding, although the reactors were shut down, it still takes time for the level of heat/radiation they produce to come down. Its obvious now the emergency cooling systems they have in these particular plants are not sufficient. http://en.wikipedia.org/wiki/Loss-of-coolant_accident
UPDATE New explosions, rooftop of reactor 4 burst, water cookin. 2 workers missing after explosion. To guys above me: Nuclear material needs months to cool down completely.
even if there is no weblink, please let us know where you are hearing the updates from (ie. broadcast on a news network, etc) -- many thanks
this link posted by RC Cola seems to clearly answer and address all the major questions and issues with the nuclear plant (including yours Lady Di). Along with the link posted earlier by bullardfan and basso, the main question concerning whether this event will be disastrous ecologically or just disastrous financially is the integrity of the containment shells. If the shells hold up even while the core melts... the effects of radiation leak are minor. But if the shells were to be breached, damaged, melted thru, the leak would be disastrous. Bullardfan's and Basso's link http://morgsatlarge.wordpress.com/20...lear-reactors/ appears to be much more confident that the shells will hold while RC Cola's link seem less sure, though at the same time, they are also somewhat confident.
German news networks, the information was released via Kyodo, NHK(japanese news-channel). The statement was from a spokesman of japanes nuclear security, so it's 100% official. UPDATE: New fire at reactor 4 right now.
The core of the nuclear reactor (without cooling) can get up to anywhere from 2000-3600F from everything I've read.
According to the link RC COLA found, (i hope hes right about everything)... http://forums.somethingawful.com/sho...readid=3396817 Is a "China Syndrome" meltdown possible? Strictly speaking, no, any fuel melt situation at Fukushima will be limited, because the fuel is physically incapable of having a runaway fission reaction. This is due to their light water reactor design. In a light water reactor, water is used as both a coolant for the fuel core and as a "neutron moderator". What a neutron moderator does is very technical (you can watch a lecture which includes this information here), but in short, when the neutron moderator is removed, the fission reaction will stop. An LWR design limits the damage caused by a meltdown, because if all of the coolant is boiled away, the fission reaction will not keep going, because the coolant is also the moderator. The core will then only generate decay heat, which while dangerous and strong enough to melt the core, is not nearly as dangerous as an active fission reaction. The containment vessel at Fukushima should be strong enough to resist breaching even during a decay heat meltdown. The amount of energy that could be produced by decay heat is easily calculated, and it is possible to design a container that will resist it. If it is not, and the core melts its way through the bottom of the vessel, it will end up in a large concrete barrier below the reactor. It is nearly impossible that a fuel melt caused by decay heat would penetrate this barrier. A containment vessel failure like this would result in a massive cleanup job but no leakage of nuclear material into the outside environment. A worst case scenario regarding the cores is a containment vessel failure combined with an uncontrolled release of radioactive steam. This would cause a localized and temporary increase in radioactivity similar to what is already present (see below) but would not result in actual nuclear fuel leakage or widespread contamination. It is this possibility that lead to the evacuations.
Pretty amazing that these reactors are even still holding up this well. I saw the headline on CNBC earlier that they weren't designed to withstand a 9.0 earthquake and 30 foot tsunami. There was some talk that GE would have some liability, but it seems pretty clear they did a great job when they designed this 40 years ago. I was trying to figure out exactly what they were designed to withstand, but I couldn't find it. Also, in case yall were curious all liability is placed on the operator Tokyo Electric Power, and they are 100% backed by the Japanese govt.
The plant had been tested to withstand a 7.9 magnitutde earthquake. Link: http://online.wsj.com/article/SB10001424052748703555404576195700301455480.html As far as the tsunami (which is what ultimately crippled the plant) is/was concerned they built a 25 foot wall as a prevention for that scenario unfortunately what they were hit with was 30+ feet high as you mentioned.
From what I've read, I wouldn't say it would be disastrous if the shells were breached. What would be disastrous is if there was an explosion, and the shell couldn't contain the radioactivity. Those elements could end up in the atmosphere and be spread across a large area, somewhat like Chernobyl. Not good. (also the scenario mentioned in that FAQ I guess...constant venting of radioactive steam I guess?) If the shell is breached, but the radioactive elements (I guess mostly the fuel) just stays there (maybe it melts through the container), then it might not be as bad. You wouldn't want to go near the plant, but at least it might be contained to only that area. Although I suppose it could also get into the ground and affect the groundwater... That said, I'd be more concerned about the fuel rods in #4, which I'm not sure even have much containment at all (just the building?). Couldn't really tell given the info out there, but if there was a major explosion around those fuel rods, which is possible given the fire and likely build-up of hydrogen, then...uh-oh. I'm still trying to figure out how the situation in #4 is even possible. To put that much effort into the active reactors, but then have such a huge vulnerability in #4. Blows my mind. I'm more concerned about that then the other reactors (think I read something that even said the other 3 reactors have stabilized to some degree?). That link is a bit older than the forum thread I linked too. Plus, being a forum thread, my link would be updated with new info. The older link (which I think I also posted at some point?) was posted around the time that we only knew about the problems with unit #1. Not sure if we even had the explosion yet, although even then, it appeared to not damage the containment structure. A lot easier to be concerned with 2 other reactors having similar problems, and one even appears to have damage to its containment (plus the fire with #4).
