#Fukushima I Nuke Plant: 3.6 Sieverts/Hr at Stack Drain Pipe for Reactors 1 and 2

Another solid "sievert" number from Fukushima I Nuclear Power Plant.

Maybe I shouldn't be writing in sieverts. It minimizes the significance somewhat. It is 3.6 sieverts/hour, or 3,600 millisieverts/hour, or 3,600,000 microsieverts/hour. No humans of any age should be exposed to that kind of radiation, not even the TEPCO workers.

From what I've found, only Mainichi Shinbun (only a brief mention) and Nikkan Sports (tabloid newspaper covering mostly sports-related news) carried the news from Kyodo News. (But I couldn't find it at Kyodo News site.)

Nikkan Sports citing Kyodo News (8/4/2011):

福島第１原発１、２号機の主排気筒の底部で毎時１０シーベルト（１万ミリシーベルト）以上の高線量が測定された問題で、東京電力は４日、底部につながる配管から毎時３・６シーベルトを測定したと発表した。

Investigating the 10-plus sieverts/hour radiation at the bottom of the main exhaust duct for the Reactors 1 and 2 at Fukushima I Nuclear Power Plant, TEPCO announced on August 4 that 3.6 sieverts/hour radiation was detected at the drain pipe that connects to the bottom of the main exhaust stack for Reactors 1 and 2.

　配管は底部にたまった雨水を排出するのに使われ、主排気筒から数メートル離れたところで毎時３・６シーベルトが測定された。東電は新たに配管周辺も立ち入り禁止区域とした。

The pipe is for draining rainwater from the bottom of the exhaust stack. 3.6 sieverts/hour radiation was measured at several meters from the exhaust stack. TEPCO has designated the area around the pipe as off-limits.

　１０シーベルト超の高線量の原因を調査するため、作業員４人が周辺を測定して発見。作業員の被ばく線量は最高で２～３ミリシーベルトだった。

The 3.6 sieverts/hour spot was found by 4 workers measuring the area as part of investigation to find out why the radiation at the exhaust stack had such high radiation exceeding 10 sieverts/hour. The maximum radiation exposure for the workers was 2 to 3 millisieverts.

Here's the photo released by TEPCO on August 5. The orange cone to the left marks the location where 10-plus sieverts/radiation was measured on August 1:

This is the photo of the location with 10-plus sieverts/hour. The pipe that extends right from the exhaust stack is the one that measured 3.6 sieverts/hour:

I have to wonder where the rainwater has been draining, all these 4-plus months.

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#Fukushima I Nuke Plant: 10+ Sieverts/Hr Spot Photos from TEPCO

So there are more than one spot.

A human worker measures the radiation with the survey meter on the stick, August 1. Judging by the pale green color on the ground, workers must have been here, spraying the resin to suppress radioactive particles from flying:

Then, the photo taken with a gamma-ray camera on July 31 shows two spots with high radiation. The lower left one is the one measured by the human worker in the first photo.

Maybe it was not such a good idea to remove the debris. They may have shielded the workers from extreme radiation like these.

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#Fukushima I Nuke Plant: Workers Knew About the Extremely High Radiation Around Exhaust Stack

They may not have known the exact number (well, for that matter, no one knows because the survey meter went overscale at 10 sieverts/hr), but they've been running past the area when they have to enter Reactor 1 building to install the external heat exchanger to the Spent Fuel Pool, according to the tweets by a worker currently at Fukushima I Nuclear Power Plant.

So much for TEPCO's word that "there is no work planned near the area, and there will be no effect on the progress of the work at the plant", which is technically correct, at least the first half.

There may not be any work planned in the area there, BECAUSE RADIATION IS TOO HIGH. There may be no work planned there, but the workers have to go near it to enter the Reactor 1 building. The radiation is so high that the workers, with all their full protection gear and equipment and construction materials they carry, have been running past the area in order to minimize radiation exposure.

So it's been known.

More information from his tweets:

(Someone asked if it's true that TEPCO does not have the survey meter that can measure more than 10 sievert/hr radiation.) I think that's correct. We do have the instrument to measure the radiation of the nuclear fuel rods, but I wonder what happened to that. Broke?

(Referring to the area where over 10 sievert/hr radiation has been detected,) the radiation level around the exhaust stacks has been too high to even go near, ever since the accident started. Not just the area around the stack for Reactors 1 and 2, but also the stack for Reactors 3 and 4.

Debris are removed by shielded heavy equipment or remote-controlled equipment. That (10+ sievert/hr) spot was found during such operation.

We have to run when we go by the stack to enter Reactor 1. That's hard work. My legs hurt already from climbing up and down the stairs in the reactor building. Now I appreciate elevators!

All the elevators inside the reactor buildings at Fukushima I Nuke Plant are broken.

As to the worker who measured the radiation with the survey meter attached to a stick, Hiroaki Koide of Kyoto University says he must have spent only 1 or 2 seconds near the stack to get 4 millisieverts radiation.

Let's see. 2.78 millisieverts for one second, if the radiation was 10 sieverts/hr.

Koide thinks the radiation level is impossibly high to be coming from inside the duct or stack. He suspects there is a piece or two of the spent fuel blown out of the Spent Fuel Pool when Reactor 1 and Reactor 3 had hydrogen explosions.

He also says the protection suits that workers wear do nothing to protect them from gamma rays, unless they wear lead vests, but even then only marginally.

(For more of his comment, there's a transcript of the radio program that he appeared in, in Japanese.)

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#Fukushima I Nuke Plant: OVER 10 SIEVERTS/HR Radiation OUTSIDE Reactor 1 and 2

The survey meter went overscale, so no one knows how high the actual radiation really is.

TEPCO hasn't updated the "survey map (contamination map)" of the plant for about a month, and I've been wondering why. (They have a new one out now, but it doesn't mention the exhaust duct at all.)

If you are exposed to 10 sieverts radiation in a short time, you will be dead.

Photo is from Kyodo News Japanese, with the original photo by the Ministry of Defense. The exhaust duct is where the black arrow is pointing.

Not clear from the Jiji article below, but the Kyodo article does say the meter went overscale and the accurate measurement is not available.

From Jiji Tsushin (11:59PM JST 8/1/2011):

東京電力は１日、福島第１原発１、２号機の原子炉建屋の間にある屋外の排気筒の表面で、過去最高の１時間当たり１０シーベルト（１万ミリシーベルト）以上の放射線量が測定されたと発表した。測定した作業員の被ばく量は最大４ミリシーベルトだった。

TEPCO announced on August 1 that the highest radiation of over 10 sieverts/hour (or 10,000 millisieverts/hour) was detected on the surface of the exhaust duct between Reactor 1 and Reactor 2 at Fukushima I Nuclear Power Plant. The workers who measured the radiation were exposed to maximum 4 millisieverts of radiation.

　これまでの最高値は、１号機原子炉建屋内で６月に測定された同４０００ミリシーベルト。同１０シーベルトを仮に６分間防護服などなしに浴びると、１０００ミリシーベルトを被ばくすることになり、吐き気やリンパ球の急激な減少などの症状が出る。

Prior to this reading, the highest radiation measured was 4,000 millisievert/hour [or 4 sieverts/hour] measured inside the reactor building of Reactor 1 in June. If one is exposed to 10 sieverts/hour radiation for 6 minutes without any protection, he would get 1,000 millisieverts [or 1 sievert] radiation, the level which causes nausea and rapid decrease of lymphocytes.

　東電は半径数メートルを立ち入り禁止にするとともに、今後、付近に鉄板を設置するなどして放射線を遮蔽（しゃへい）する。ただ、この付近での作業は予定されておらず、今後の事故収束作業への影響はないという。

TEPCO will prohibit access to the area within a few meters radius of the duct, and plans to shield the radiation by installing steel panels around the area. However, according to TEPCO, there is no work planned near the area, and there will be no effect on the progress of the work at the plant.

　 東電によると、排気筒には非常用ガス処理系と呼ばれる配管が接続されており、この接続部で高線量が測定された。１号機では震災直後の３月１２日、原子炉格 納容器の圧力逃がし弁を開く「ベント」が行われたが、その際に、容器内の空気がこの配管の中を通った。東電は、通過した気体に含まれる放射性物質が配管内 に付着し、何らかの理由で高い放射線量になったとみている。

According to TEPCO, the pipe for the emergency gas process system is connected to the exhaust duct, and it was at the joint that the high radiation was measured. On March 12 right after the earthquake/tsunami, they did the venting in Reactor 1, in which the pressure release valve on the Containment Vessel was opened to let the air inside the CV out. TEPCO thinks the radioactive materials in that air somehow got attached inside the duct, causing the high radiation.

Wait a minute. How could the work at the plant not be affected? TEPCO is going to put the gigantic cover over Reactor 1, and this exhaust pipe is right in the way.

(h/t Dr. Ono and anon readers)

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