Dry Vent of Reactor 2 May Have Released Largest Amount of Radioactive Materials, Not Explosions

The paper by a Tokyo University researcher that was finally published nearly one year after he took the samples at the front gate of Fukushima I Nuclear Power Plant and in Iitate-mura in Fukushima Prefecture (see my post from yesterday) has this very interesting chart.

It shows the spacial dose of radiation at the front gate of Fukushima I Nuke Plant and the timeline of events at the plant in March. The largest spike seems to be around or after 12AM on March 15, and the label on the spike says "Dry vent at reactor no.2".

On checking the information from March 2011, I find that TEPCO did the dry vent at Reactor 2 at 12AM on March 15, 2011 for a few minutes. At first (on March 20), TEPCO announced they'd done the dry vent sometime on March 16 and 17, but on March 21 retracted that statement and said the dry vent was done at 12AM on March 15. (See Sankei Shinbun article on 3/21/2011.)

It is not clear whether the company informed the residents or the government before the the Reactor 2 dry vent on March 15 which caused a huge spike in radiation, and which may be the biggest contributor to radiation contamination in wide areas in Tohoku and Kanto. From the Sankei article it doesn't look like they gave any prior notice. This is the same company that didn't even tell the plant workers that the vent on Reactor 1 was about to be carried out on March 12.

Dry vent releases different types of radioactive materials compared to wet vent.

The peak that appears to the right side of the largest peak is after the hydrogen explosion of Reactor 4, but not at the time of explosion. I suspect the peak may have been the result of some event on Reactor 2's Suppression Chamber which seems to have taken place about the same time as the Reactor 4 hydrogen explosion. TEPCO says it was not "explosion" that happened at the Reactor 2 Suppression Chamber but still doesn't say what it was.

The second largest peak was when the fire broke out on Reactor 3 on March 16. The white smoke was seen at 8:30AM on March 16, and the radiation level at the front gate of the plant shot up to 10,000 microsieverts/hour (10 millisievert/hour) at 10:40AM (Asahi Shinbun 3/16/2011).

Again, it is just too bad that the researcher had to sit on the data for 11 months for his article to be published in a peer-review magazine.

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Update on Byron Nuclear Plant: Diesel Generators Used for Vent, Excelon Says Tritium Is Natural

From Rockford Register Star (1/30/2012 8:43PM):

ROCKFORD — A loss of power coming into the Byron nuclear plant caused one of two reactors to automatically shut down about 10:15 a.m. today.

Backup diesel generators were activated after the power outage and were being used for safety equipment that vents heat from the reactor, according to a spokeswoman from the Nuclear Regulatory Commission in Lisle.

“Right now, we believe the plant is in a stable condition,” said the NRC’s Viktoria Mitlyng. “There is no danger to the workers or the public.”

Exelon, which operates the Byron plant, declared an “unusual event” — the lowest of four emergency classifications established by the NRC — after the outage.

Mitlyng said two NRC resident inspectors are monitoring the plant.

...

Byron station spokesman Paul Dempsey said crews are still trying to determine how power coming to the generator was interrupted. The steam release, which he said made a whooshing sound, was expected to continue into the evening.

The steam contains tritium, a hydrogen isotope with low levels of radioactivity. Exelon, in a news release, said tritium occurs naturally and is found in virtually all surface water, although it is found in greater concentrations near nuclear reactors.

It was the first automatic shutdown of the plant since 2007 when a dime-sized hole in a water cooling pipe led to the shutdown of both reactors.

(Full article at the link)

They all say the same thing. It is safe, radioactive materials are natural. Soon they'll be talking about bananas and transcontinental flights and X-rays.

From wiki on tritium from fission:

Tritium is an uncommon product of the nuclear fission of uranium-235, plutonium-239, and uranium-233, with a production of about one per each 10,000 fissions.^[7][8] This means that the release or recovery of tritium needs to be considered in the operation of nuclear reactors, especially in the reprocessing of nuclear fuels and in the storage of spent nuclear fuel. The production of tritium was not a goal, but is rather just a side-effect.

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"Now They Tell Us" Series: NISA Says Reactors 1 and 3 Explosions May Have Been Caused by Vent

(In case you haven't read about it during my absence...)

Nikkei Shinbun reports that NISA admitted the hydrogen explosions that took place in Reactor 1 and Reactor 3 at Fukushima I Nuclear Power Plant in March may have been caused by hydrogen flowing back from the exhaust stack. In other words, vent may have caused the explosions.

From Nikkei Shinbun (12/27/2011):

経済産業省原子力安全・保安院は27日開いた東京電力福島第１原子力発電所の事故原因に関する専門家の意見聴取会で、１、３号機の水素爆発の一因として、原子炉格納容器からベント（排気）した水素が別の排気管を通って建屋内に逆流した可能性があると公表した。津波による電源喪失で排気管の弁が開き、水素の逆流を防げなかったという。

The Nuclear and Industrial Safety Agency under the Ministry of Economy, Trade and Industry disclosed during the experts hearing on December 27 on the cause of the Fukushima I Nuclear Power Plant accident that a possible cause of the hydrogen explosions in Reactors 1 and 3 may have been that the hydrogen that was vented from the Containment Vessel [to the exhaust stack] flowed back into the reactor building through a different pipe. As the power was lost due to tsunami, the valve of this different pipe remained open, and unable to prevent the reverse flow of hydrogen, according to the NISA.

　１、３号機は炉心溶融で格納容器に水素がたまり、水素を抜くベントをした。ベントの排気管は、原子炉建屋の換気をする「非常用ガス処理系」の排気管と合流し、排気筒につながっている。

In Reactors 1 and 3, hydrogen accumulated in the Containment Vessels after the core meltdowns, and TEPCO carried out the vent in order to remove hydrogen. The exhaust pipe for the vent connects to the exhaust pipe for the "standby gas treatment system" for the air ventilation of the reactor building, and then to the exhaust stack.

　非常用ガス処理系の排気管は電源喪失時に建屋の換気を妨げないよう弁が開いた。実際に事故後の３号機の調査では弁が開いていたという。ベントをした際に水素が弁を通って建屋に逆流。格納容器の上蓋から漏れた水素と一緒に原子炉建屋に流れ込み、水素爆発したとみられる。

The valve of the exhaust pipe for the standby gas treatment system opened when the power was lost, so that the air ventilation of the reactor building would continue. In fact, the investigation of Reactor 3 after the accident showed the valve was open. When TEPCO did the vent, hydrogen may have flowed back to the reactor building through the open valve, and with the hydrogen leaked from the top lid of the Containment Vessel caused the hydrogen explosion.

　国内の他の原発も電源喪失で弁が開く構造。保安院は対策として、２本の排気管を独立させ、逆流防止弁を設置する方法を挙げた。奈良林直・北海道大学教授は「ベントを徹底的に改善する必要がある」と指摘する。

All the other nuclear reactors in Japan has the same system whereby the valve opens when the power is lost. As a countermeasure, the NISA suggests two separate exhaust pipes and installing a valve to prevent backflow. Professor Tadashi Narabayashi of Hokkaido University points out that the vent process needs to be improved fundamentally.

Narabayashi, one of the "Three Plutonium Brothers" who said the toxicity of plutonium was the same as salt, used to work for Toshiba.

So after more than 9 months since the accident NISA feels like telling the truth for some reason, now that the accident is officially "over".

The very act of venting probably caused the explosions, says NISA. How about that, GE?

Product liability lawsuits anyone?

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TEPCO: "Release of Radioactive Materials from Reactor 1 Building Will Be Small"

and the famous last word, I'm sure. "No ill effect on human health".

The latest from Yomiuri Shinbun (10:26PM JST 5/7/2011):

　東京電力は７日、福島第一原子力発電所１号機の原子炉建屋内から８日午後にも、放射性物質が外部へ放出される可能性があると発表した。

TEPCO announced on May 7 that there is a possibility that radioactive materials may be released in the afternoon of May 8 from the reactor building of the Reactor 1 at Fukushima I Nuclear Power Plant.

　原子炉建屋内で人が本格的な作業を始めるのに先立ち、原子炉建屋の二重扉を開放するため。東電は発電所周辺の放射線量の監視を強化する。

TEPCO is going to open the double door to the reactor building [for the first time since the accident] so that the workers can work inside the reactor building for longer periods. TEPCO will monitor the radiation level in and around the plant.

　東電によると、タービン建屋との間にあるこの二重扉を利用して敷設した配管で、原子炉建屋内の空気をタービン建屋側に設置した浄化装置に引き込 み、浮遊する放射性物質を除去している。二重扉はタービン建屋側に作った小部屋で覆っているため、両方の建屋は事実上は仕切られていた。

The air inside the reactor building is being fed through the ducts that go through the double door between the reactor building and the turbine building, and to the air filtering system set up inside the turbine building that removes radioactive materials in the air. TEPCO built a compartment to separate the area where the double door is; so far the turbine building and the reactor building have been separated by this compartment.

　しかし、５日に始めた浄化で原子炉建屋内の放射性物質濃度が下がり、作業を本格化させるめどがついた。そのため、東電は８日午後にも小部屋を取り払い、扉を開放することを決めた。

However, [TEPCO says] the level of radioactive materials inside the reactor building has been reduced enough for further works to be carried out inside the building, thanks to the air filtering system that's been in operation since May 5. TEPCO will remove the compartment [between the reactor building and the turbine building] in the afternoon of May 8 and open the double door.

That's diametrically opposite of what the government officials were apparently saying on May 1, when the PM's assistant was on record saying "there will be a large amount of radioactive materials released on May 8".

No estimate or simulation of how low (or high) the level may be of the radioactive materials coming out of the Reactor 1 reactor building. No official (government) word.

For the rest of us, we are supposed to take TEPCO's word and feel secure and comforted that radiation will be low.

This is the company that somehow forgot (didn't bother, I might say) to inform the plant workers of the "dry vent" (the link is in Japanese) that it did on Reactor 1 on March 12, exposing the workers on the ground to high radiation without them knowing. Only a handful operators who did the vent, and some in the operation headquarters at the plant knew about it, and not all workers had dosimeters with them at that time (dosimeters were swept away and lost in the tsunami).

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