>10Sv/h - I wouldn't touch it with a 10' pole: Fukushima ROV 64

TEPCO site photo shows greater than 10 Sieverts per hour being measured with a 3-meter-long arm.  Picture by gamma ray camera shows two sources of high radiation at the bottom of the exhaust stack for Unit 1 and 2 Reactor Buildings.

Aug 2, 2011 - Site photo and picture of γ-ray camera of high radiation source over 10 Sv/h.(66.6KB)PDF

NHK World - TEPCO to check plant radiation levels carefully

The operator of the crippled Fukushima nuclear complex is searching for radioactive hotspots after finding extremely high radiation near an exhaust pipe at the plant.
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A photo released on Tuesday shows workers taking measurements with a detector attached to the tip of a 3-meter-long arm. The level of radiation where the workers stood reportedly reached 40 millisieverts per hour.
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The utility has declared the area off-limits, and is planning to seal it off with mats stuffed with lead.
It will also carefully check whether there are other highly contaminated sites within the premises that may hamper cleanup work.

Tuesday, August 02, 2011 12:34 +0900 (JST)

NHK World - Highest radioactivity level detected at nuke plant

The operator of the Fukushima Daiichi nuclear power plant says it has detected 10,000 millisieverts of radioactivity per hour at the plant. The level is the highest detected there since the nuclear accident in March.

Workers of Tokyo Electric Power Company, or TEPCO, on Monday measured the extremely high level of radioactivity near pipes at the bottom of a duct between the No.1 and neighboring No.2 reactor buildings.
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The utility had detected a maximum of 1,000 millisieverts per hour outdoors in debris, and also found a maximum of 4,000 millisieverts per hour indoors in one of the reactor buildings.

Tuesday, August 02, 2011 06:33 +0900 (JST)

XKCD Radiation Dose Chart (90KB PNG) comparing radiation doses from different sources.

EX-SKF blog post with English translations of Japanese articles from Kyodo News and Jiji Tsushin.Fukushima I Nuke Plant: OVER 10 SIEVERTS/HR Radiation OUTSIDE Reactor 1 and 2

After over a month without an update, TEPCO finally published new Radiation Survey Maps 2011, August, 2 - Survey map of Fukushima Daiichi Nuclear Power Station(on August,1) 457KB PDF showing a light yellow balloon that was "Measured at 14:00∼14:30, August 1 2011"

U1/2 SGTS
>10,000

The Radiation Survey Map should show a black arrow pointing to the location, but that is missing in the English version.  The black arrow can be seen on the Japanese version.  2011, August, 2 - Survey map of Fukushima Daiichi Nuclear Power Station(on August,1) 467KB PDF

Comment by Joleau in k9disc diary 10,000 Millisieverts/Hour @ Fukushima

10 Sv is 1,000 Rem. A thousand Rem acute absorbed dose causes gastrointestinal syndrome - the lining of the stomach and intestines is destroyed, violent vomiting and diarrhea ensue within 10 minutes, death in a matter of hours.

For reference, LD50 for whole body absorbed dose (gamma) is 300 Rem, or 3 Sieverts. 50% of those exposed to this amount of radiation will die within 60 days.

Thanks for posting this, k9. My read (from the SFGate via Bloomberg) is that the reading was taken at the base of the main vent stack for units 1 & 2 (the tall white oil derrick looking thing), apparently coming from the vent pipe trench. It doesn't say exactly what the level may have been, just that it pegged the high gage on the geigers. It could have been ten times higher for all anybody knows.

Now, TEPCO insists that it must be coming from "venting" of one or both reactors back in March, but if it's this hot four and a half months later, they'd have noticed it before now. I promise. Besides, these big vent stacks weren't used to vent the reactors when they first melted, because the torus vents didn't fucking work. Instead, the gas went out into the buildings and exploded rather spectacularly. If they're getting high level gas to the vent at this point something critical is happening beneath the drywell(s) of one or both plants. Maybe corium melted through those infernal stuck vents. Who knows?

I'll keep looking for photos/video and would surely love to see data on what's present in the way of gases. Though I doubt seriously that information will ever be released. They've got that place screwed down tight now that they've officially declared the entire reservation to be in "stable" condition.

The TEPCO Live Camera has had the Unit 1/2 Exhaust Stack centered in the frame for the last couple of months.  You can see the duct angling down towards the exhaust stack between Unit 1 and 2 Reactor Buildings, just to the left of the green vegetation.

Today, it was announced that TEPCO found a 5 Sv/h reading in the Unit 1 Reactor Building on the second floor.

NHK World - High radioactivity level at reactor building

The operator of the Fukushima Daiichi nuclear power plant says it has detected the highest confirmed indoor level of radioactivity at the facility since the March accident.

The Tokyo Electric Power Company, or TEPCO, said on Tuesday that the level in a room on the second floor of the Number One reactor building was 5,000 millisieverts per hour.

The utility restricted access to the room, saying it will consider measures to block the radioactivity and that it has no immediate plans for operations needed in the room to bring the troubled reactor under control.
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Tuesday, August 02, 2011 20:24 +0900 (JST)

But that is not all, the Mainichi Daily News reports that TEPCO has found other highly radioactive pipes, but that TEPCO will not measure them.  TEPCO claims that no workers will be in that area, so the readings are not needed!

The Mainichi Daily News - Highest levels of radiation since March 11 detected at Fukushima nuclear reactors

In a related development, TEPCO said on Aug. 2 that there were two more pipes nearby that apparently showed radiation in excess of 10 sieverts. The utility said it had not actually measured the radiation there and it had no plans to do so because there would be no one working there.
(Mainichi Japan) August 2, 2011