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Meltdown Likely Under Way At Japan Nuclear Reactor


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Kyodo News:

Radiation twice the maximum seen so far detected at nuke plant Monday: TEPCO

Fuel rods fully exposed again as of 11 p.m.

00:42 15 March 2011 JST

Isn't this a big problem? Fully exposed rods? I keep watching for a post from you guys.....

Isn't 11pm very recent? The posting times confuse me.

This is a huge - huge - problem. Sorry for sounding alarmist but that's how I see the situation now.

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I'm going to bed now... remember...I'm on Thailand time...

Yes...exposed rods are a huge problem.. No cooling means the reactor casing enclosing the fuel rods begins to melt and potentially expose the nuclear fuel, which can fall out of the enclosure and start doing all kinds of bad things...

The reactor no. 2 reactor rods were totally uncovered two different times Monday...including one time for at least two hours....

And those babies get HOT!!!!!

Worst case scenario in that kind of situation is an explosion caused by the melting fuel...the impact of which could spread the contamination far and wide....if it's not contained by the reactor's external enclosure...

But that's the doomsday stuff... Not there... hopefully ever...and certainly not yet. That's why it's so crucial the Japanese keep those reactors cooled down at least until the fission process subsides.'

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Explosion at the Daiichi #2 plant.

This one seems to be a bit more serious though, as it seems to have happened within the outer containing vessel (the structure between the steel reactor vat and the outer building)

Streaming on NHK world: http://www3.nhk.or.jp/nhkworld/

- Right after the explosion a radiation level of 965.5 μSv was reported, now lowered to 882.7μSv. Still reasonably low levels.

- Plant operators not directly involved in this operation are being evacuated to prevent long-term exposure.

- Wind direction at the plant is NNE shifting to N

- Suppression pool (the donut-shaped structure at the very bottom of the reactor) may have been damaged, which may lead to contaminated water leaking into the environment.

Edited by Jdietz
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- Water level before and after the explosion constant at 2700mm exposed (means the fuel rods are still partially under water and nothing seems to be leaking out right now)

- Around 50 staff remain on site, rest is evacuated.

Edited by Jdietz
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Status update Daiichi #2 reactor:

- Water injection is still continuing

- Damage to structure not confirmed, though pressure dropped, water level constant. Only really known fact is the sound of an explosion

- No significant change in the reactors parameters after the explosion

Status update Daiichi #3 reactor:

- Steam-like substance is accumulating in the top of the reactor, unknown consistence.

Status update Daiichi #4 reactor:

- Temperature dropped below 100C, and is now in cold shutdown

Meteorological data at the site is unavailable since the quake

Northerly wind reported at MET site 50km south

Current radiation level at the site border: 871uSv/hour

Translator seems to have some problems with radiation units, looks like the earlier numbers are correct.

After the blast at #2 the pressure in the suppression chamber went down from 3 atmosphere to 1, indicating some kind of damage.

Edited by Jdietz
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New Blast Reported at Nuclear Plant as Japan Struggles to Cool Reactor

By HIROKO TABUCHI, KEITH BRADSHER and MATT WALD

Published: March 14, 2011

TOKYO — An explosion early Tuesday morning may have damaged the inner steel containment vessel of the No. 2 reactor at Japan's Fukushima Daiichi Nuclear Power Station, leading to the wide release of radioactive materials there and forcing the evacuation of some emergency workers, the plant's operator said.

The blast appeared to be different — and more severe — than those that at two other troubled reactor at the same nuclear complex because this one, reported to have occurred at 6:14 a.m., happened in the "pressure suppression room" in the cooling area of the reactor, raising the possibility to damage to the reactor's containment vessel.

Any damage to the steel containment vessel of a nuclear reactor is considered critical because it raises the prospect of an uncontrolled release of radioactive material and full meltdown of the nuclear fuel inside. To date, even during the four-day crisis in Japan that amounts to the worst nuclear accident since Chernobyl, workers had managed to avoid a breach of a containment vessel and had limited releases of radioactive steam to relatively low levels.

Details of what happened remain unclear, with executives of Tokyo Electric Power, the plant's operator, giving only preliminary reports of damage to the suppression pool but declining to provide a full explanation of what that meant.

But the new blast came after emergency operations to pump seawater into the same reactor failed, leaving the nuclear fuel in that reactor dangerously exposed late Monday into early Tuesday morning.

Continues:

http://www.nytimes.c...tml?_r=1&emc=na

LaoPo

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An extra pump vehicle is on the way to reactor #2 to help cool it, will arrive this morning.

This seems to be the latest real radiation information:

The radiation level at the troubled nuclear plant in Fukushima Prefecture shot up to 8,217 micro sievert per hour temporarily Tuesday morning after an explosion was heard at its No. 2 reactor, Tokyo Electric Power Co. said.

Perspective:

natural background radiation exposes people to about 0.35 micro Sievert per hour.

cosmic radiation during commercial flight exposes fliers to about 10 micro Sievert per hour.

After the incident the numbers dropped off again quickly.

965.5 uSv at 7am

882.7 uSv at 8am

387.3 uSv now.

Edited by Jdietz
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Jdietz... thanks for providing the morning updates here while I was blissfully sleeping...

Please do, however, provide the source and links for that kind of info, so everyone knows the source/sources it's coming from. That's SOP. A-OK! :D

As the situation seems not to be worsening now, I'm going to have a shower and breakfast, I'll keep monitoring the situation.

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