Union of Concerned Scientists on the Japan Nuclear Disaster

[Kalun D]

a live blog with a concise scientific account in layman's terms

http://allthingsnuclear.org/tagged/Japan_nuclear

all 3 working reactors have had low water and partial meltdowns

3 and 4 have complete failure of secondary containment

#2 has a compromised primary containment

this model of GE reactor has documented problems (by Sandia labs) of known failure issues with the primary containment.

Pray for the workers who stay to the last to try to put this fire out.

[Ghost Dog]

1. Excellent, thanks. *** Monday Update on Fukushima Reactors ***

Monday Update on Fukushima Reactors
| by David Wright | nuclear power | nuclear power safety | Japan nuclear |
As of 11:30 pm EDT Monday 3/14/11

...

Unfortunately, reports on Unit 2 suggest the situation is more serious. After the cooling systems for this reactor failed over the weekend, workers were unable to fill the reactor vessel with sea water. This appears to have been caused in part by human error, and the plant owner, TEPCO, has stated that the fuel in the core of Unit 2 was completely uncovered for a matter of hours. This could lead to very serious melting of the fuel. If that condition continues long enough, it could lead to a total melting of the fuel, which is called a meltdown.

If that occurs, the molten fuel can drop to the bottom of the reactor vessel, burn through the reactor vessel, and drop onto the floor of the primary containment. There is currently no indication this has happened at Unit 2, but if they are unable to get cooling water into the reactor vessel it is likely only a matter of time until this happens.

...

Monday night TEPCO confirmed there is damage to the Unit 2 containment and that it may be leaking gases and or liquids... So if the primary containment is leaking, then a core meltdown could lead to a very large release of radioactivity to the environment.

The second concern is that even if the primary containment is currently intact, the Mark I containment system used in these reactors has a known vulnerability to meltdowns. Molten fuel that enters the primary containment area can melt through the wall of the primary containment—a situation called liner melt-through—which would also allow the release of large amounts of radioactivity to the environment.

/...Excellent Summary:... http://allthingsnuclear.org/post/3870616176/monday-update-on-fukushima-reactors