Ex-Representative Kawauchi Went Inside #Fukushima Reactor 1 Bldg, Says Hydrogen Explosion May Have Happened on 4th Floor, Not 5th (Top Floor)

So that was the occasion for the "blank" videos that TEPCO uploaded two days ago. I didn't pay much attention until I saw the tweets today by Mr. Hiroshi Kawauchi, former DPJ member of the Japanese Diet Lower House from Kagoshima Prefecture who lost in the December 2012 election along with many of his party.

As per previous offer and agreement from TEPCO while he was still a member of the Diet, Mr. Kawauchi went inside the Reactor 1 building at Fukushima I Nuclear Power Plant on March 13, 2013, accompanied by TEPCO (or affiliate company) workers. They had a video camera, which was to record whatever Mr. Kawauchi wanted, as he directed. The problem was that the tape that was used to protect the camera got partially detached, and stuck on the camera lens. So the lens cover closed, leaving only a small hole in the center. (For TEPCO's report (in Japanese only) on the incident, see here.)

Mr. Kawauchi is not too happy, and says another trip will be arranged with TEPCO.

In the meantime, he has tweeted what he found on his March 13, 2013 visit to the Reactor 1 building. He now thinks it was on the 4th floor of the building that a hydrogen explosion took place, not the top 5th floor as has always been assumed. The 4th floor is where the Isolation Condenser (IC) is located.

福島第一原発1号原子炉建屋視察報告。今回の視察で分かったことは、1号の水素爆発は最上階の５階ではなく、ひとつ下、非常用復水器のある４階で起こったのではないか、ということ。そう考える根拠を２つあげたい。４階と５階の間、即ち４階の天井５階の床には、大きな機材搬入の為の穴がある。(tweet link)

Report on my visit to Fukushima I Nuke Plant Reactor 1 building. What's been revealed [to me] in this visit is that the hydrogen explosion of Reactor 1 may have happened not on the top 5th floor but on the one below, on the 4th floor where the Isolation Condenser is located. I'd like to submit two reasons why I think that way. Between the 4th and 5th floor - in other words the ceiling of the 4th floor which is the floor of the 5th floor, there is a huge hole to bring large equipment through.

この大物搬入口は、5メートル四方。作業時には、労働安全衛生法上の義務として、転落防止の為の手摺が設置される。作業時以外は、重さ1.5トンの鉄板で塞がれている。即ち、手摺があるかないかが、搬入口が閉じていたか、開いていたかの判断の分かれ目になる。では、実際にはどうだったのか？(tweet link)

This opening is 5 meters square (5 x 5). When it is in use, handrails are installed to prevent falls, as required by the Industrial Safety and Health Law. When not in use, the opening is covered with the steel plate weighing 1.5 tonnes. In other words, presence or absence of the handrails would indicate whether the opening was open or closed [when the explosion took place]. So, which was it?

原子炉建屋４階から天井を見上げると、五メートル四方の搬入口が、パックリと空いていた。肝腎の手摺はどうか？手摺は、無かった。手摺が無いということは、鉄板が閉まっていた筈。同行した東電社員も確認した。では、なぜ鉄板が無いのか？即ち、４階の水素爆発で吹き飛ばされたのではないか？(tweet link)

On the 4th floor and looking up at the ceiling, I saw the 5x5 opening open. How about the handrails? There were no handrails. No handrails means the opening was closed with the steel plate. Why wasn't the steel plate there? Is it because it was blown off by the hydrogen explosion on the 4th floor?

４階天井、５階床の大物搬入口。４階での水素爆発で下から上へ吹き上げられた、だから現在は、パックリ口を空けているのではないか、と考えるのが自然。実際、国会事故調のヒヤリングでも当時、現場の作業責任者が、大物搬入口の蓋を閉めた、と証言している。今回の視察で、その証言が裏付けられた。(tweet link)

It is natural to think this [steel plate covering the] opening on the 4th floor ceiling which is the 5th floor floor to carry large equipment through was blown upward by the hydrogen explosion on the 4th floor, therefore it is open now. In fact, in a testimony in the National Diet accident investigation commission, the person in charge of the work testified that they had closed the opening with the steel plate. In my visit, this testimony was confirmed.

もうひとつ、４階で水素爆発が起きてたのではないか、という根拠を示す。４階非常用復水器のすぐ横を、主蒸気管が垂直に通っている。この主蒸気管の、物凄く分厚い被覆材が凄まじい勢いでめくり上がっているのだ。非常用復水器の蒸気ラインの被覆材も同様だ。４階の凄まじい損壊の状況も合わせ考えると(tweet link)

Another reason why I think the hydrogen explosion took place on the 4th floor. The main steam pipe runs vertically right next to the Isolation Condenser on the 4th floor. Extremely thick covering material around the main steam pipe is severely turned up. Same thing with the covering material around the steam line of the Isolation Condenser. Taking together the severe destruction of the 4th floor...

この被覆材の捲れは、爆発の影響以外の何者でもない。1号原子炉建屋は、最上階の５階ではなく、ひとつ下の非常用復水器が設置されている４階で水素爆発が起きたと考える方が、水平方向に爆発していた爆発映像も考えあわせると、自然である。同行した東電社員も、否定できない、と認めていた。(tweet link)

... I believe this turning up of the covering material is definitely from the explosion. It makes more sense to think the hydrogen explosion of the Reactor 1 building happened not on the top 5th floor but on the 4th floor where the Isolation Condenser is located. Recall the video of the explosion, which spread in horizontal direction. TEPCO workers who accompanied me admitted that the possibility couldn't be denied.

現場を実際に、自分で確認し、私が知り得たことで、皆に報告をしなければならないことが、まだ他にもあるが、次回に回す。しかし、水素爆発が５階でなく、４階で起きていたとすれば、何故水素が４階に溜まったのかを解明しなければならない。これまでの、政府や東電の説明では説明できないからだ。(tweet link)

There are other things I saw and confirmed in person that I need to report to you, but that has to wait until next time. However, if the hydrogen explosion did take place not on the 5th floor but on the 4th floor, we have to figure out why hydrogen had accumulated on the 4th floor. That cannot be explained by the explanations so far by the government or TEPCO.

What difference does it make at this point, you may ask? That is indeed the rhetorical question some of the tweets to him ask.

After more than two years since Reactor 1 blew up, we still don't know how that happened. Many details of the accident are still not clear (and not many are interested in knowing), and many influential experts, journalists, bloggers base their pronouncements on the accident or the radiation contamination on assumptions and hearsay.

Without knowing and understanding exactly what happened and how, I don't believe there can be a "recovery". People in Japan will simply repeat a one-issue mantra of "beyond nuclear", without knowing and understanding exactly what has happened to them and their land because of that "nuclear".

The video of Reactor 1 explosion on March 12, 2011 does show, after the initial puff upwards, lateral spread of smoke and/or steam (as Professor Takashi Tsuruda of Akita Prefectural University (his specialty is combustion) thinks there was an explosion in the Suppression Chamber of Reactor 1):

It was good that Mr. Kawauchi was able to go inside the reactor building. It would be even better if he could bring along an explosion expert like Professor Tsuruda.

According to my own post on that day;

• At 3PM 3/12/11, about 30 minutes before the explosion took place, TEPCO (the power company) announced that it was successful in relieving the pressure in the fuel core container.

• The fuel rods are half-exposed, due to lower water level.

• Cesium and Iodine have been detected in the atmosphere near the plant. [Both are products of nuclear fission.]

• 4 people were injured.

As to the destruction of the 4th floor of Reactor 1 near the Isolation Condenser, see this video (if you haven't seen it yet) from October 2011:

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#Fukushima I Nuke Plant Nitrogen Injection System: Compressor Failure, Backup Injection System Started

Details in the press conference at 9:30AM, April 13 in Fukushima (Fukushima I Nuclear Power Plant?), and at 11:00AM at TEPCO's headquarters in Tokyo.

From the tweets by an independent journalist who's on the list to receive TEPCO's emails on the plant situation:

• Drop in the amount of nitrogen gas being injected into Reactors 1, 2, 3 was noted by a TEPCO employee at 1AM, April 13 when he was checking the plant parameters.

• The nitrogen injection system was inspected at 1:30AM. It turned out that the system alarm had gone off at 1:04AM for "compressor failure", and the system had stopped ("nitrogen gas separation system B").

• At 3:10AM, the backup system ("nitrogen gas separation system" on the high ground) was started, and at 3:46AM the nitrogen gas injection restarted.

• There has been no discernible change in the plant parameters, hydrogen density, or the monitoring post data.

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(UPDATED) #Fukushima I Nuke Plant: Nitrogen Injection System for Reactors 1, 2, 3 Stopped, TEPCO Trying to Restart

(UPDATE: TEPCO started the backup system at 12:30PM, and nitrogen injection has started. Still no word about why the system stopped in the first place. Since TEPCO is incurious, don't hold your breath for the answer.)

(2nd UPDATE 4/4/2012: TEPCO monitors the system every 6 hours. A worker just happened to look at the monitor screen and noticed the amount of nitrogen injected showed zero. No one seems to know how long the system had stopped, and no one seem eager to find out.)

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From Jiji Tsushin (4/4/2012, 12:24PM):

１～３号機の窒素封入装置停止＝水素濃度抑制へ、復旧急ぐ－福島第１原発

Nitrogen injection system for Reactors 1, 2, 3 at Fukushima I Nuke Plant stopped, TEPCO trying to restore the system to keep the hydrogen concentration low.

　東京電力福島第１原発事故で、東電は４日、１～３号機の格納容器に窒素を封入する装置が停止したと発表した。窒素は水素爆発の原因となる格納容器内の水素濃度を抑えるために封入されているが、東電は水素が危険な濃度になるまでは３０時間かかるとしており、復旧を急いでいる。

TEPCO announced on April 4 that the system that injects nitrogen gas into the Containment Vessels of Reactors 1, 2 and 3 had stopped. Nitrogen is being injected into the Containment Vessels to suppress the rise of hydrogen gas concentration , which could cause hydrogen explosions. According to TEPCO, it takes 30 hours before the hydrogen concentration reaches a dangerous level. The company is currently trying to restore the system.

　東電によると、同日午前１１時前、窒素封入装置が止まっているのを作業員が見つけた。同社は装置の復旧作業を進めるとともに、原因を調べている。

According to TEPCO, before 11AM on April 4, a worker found the nitrogen injection system had stopped. The company is restoring the system, and trying to identify the cause.

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Futaba-machi Mayor on March 12, 2011 Explosion of Reactor 1: "Insulation Materials Falling Like Large Snowflakes. I Knew We Were Finished"

Mayor Idogawa says he knew it was the end.

Journalist Hiromichi Ugaya compiled a togetter of the press conference by the mayor of Futaba-machi on February 11, 2012.

Futaba-machi is where part of Fukushima I Nuclear Power Plant is located (Reactors 5, 6). The town's function has been moved to Kazo City in Saitama Prefecture, and the mayor, Katsutaka Idogawa, is now demanding that his town of about 7,400 residents be relocated instead of "decontaminated".

Ugaya says Mayor Idogawa held three separate press conferences, one for TV, one for newspapers, and one for independent journalists. I haven't looked carefully yet, but I don't see any coverage at the websites of major newspapers.

Mayor Idogawa said:

• There was no instruction from the government as to where to evacuate, or how to evacuate.

• The town was not told of the vent, and the vent was carried out while there were lots of people still in town.

• What looked to be the insulation materials from the plant fell like snowflakes on them, and he knew they were finished.

The following is my translation of most of the remarks by Mayor Idogawa, as tweeted by Ugaya, who was at the conference:

Current situation of Futaba-machi in exile, as narrated by the journalist Ugaya:

同町は福島第1原発が町内にある「立地自治体」。町全体が立入禁止（警戒区域）になって全町民６４００人が避難。練馬区くらいの大きさの町。役場は埼玉県加須市に移転。きょう移転先役場で町長に会った。

Futaba-machi is one of the "municipalities with nuclear power plants", where Fukushima I Nuclear Power Plant is located. The entire town was designated as "no entry zone" and all 6400 [sic] residents have evacuated. It is the size of Nerima-ku [in Tokyo]. The town hall has relocated to Kazo City in Saitama Prefecture. I [Ugaya] met the mayor at the temporary town hall of Futaba-machi.

移転先は埼玉県加須市、生徒が減って廃校になった騎西高校をそのまま使っている。なお５００人弱の双葉町民がそのまま避難生活を続けている。そのありさまにも驚いた。アパートなど借り上げ住宅に移っていない人もまだそんなにたくさんいるのだ。

The temporary town hall is located in Kazo City, Saitama. They use the high school building that has been closed. About 500 Futaba-machi residents still live there. I am surprised. Still that many people living in the shelter, instead of living in apartments or other temporary housing arrangements.

Mayor Idogawa's recollection on the day of Reactor 1 hydrogen explosion (3/12/2011):

町民は、過去の歴史だけでなく、将来をも奪われてしまった。これはどんな価値よりも大切なものを奪われたということです。それは東京電力の補償など絶対に追いつかない

Residents of Futaba-machi have been deprived not only of their past but also of their future. They have been deprived of the most precious thing that no amount of compensation from TEPCO could buy.

「どの方向似」「何で避難する」避難指示が国や県からなかったので、役場の前の旗を見て風向きを見て逃げる方向を判断せざるをえなかった。

"Which direction?" "How do we evacuate?" There was no evacuation instruction from the national or prefectural government. So we looked at the flag in front of the town hall, figured out the wind direction, and decided which way to evacuate.

それまでの毎年の避難訓練は「電源が失われたが、３時間くらいで復旧、冷却装置が作動」というシナリオだったので、まったく役に立たなかった。

The scenario of the annual evacuation drills was "Power is lost, and recovers in about 3 hours, and the reactor cooling system comes back online". The drills were useless in the real-life accident.

町民はやむなくバラバラにマイカーで逃げるしかなかった。福島県川俣町が避難を受け入れることを決めたので、防災無線で「とにかく川俣町へ」と必死で呼びかけた。

Residents had to flee in their own cars. Kawamata-machi [northwest of Futaba-machi, just beyond Iitate-mura] had just decided to accept evacuees, so we used the emergency communication system and called out desperately to the residents to somehow go to Kawamata-machi.

政府が決めた「ベント」も何の予告もなかった。町民が真下にまだいるのに、ベントが行われた。自分たちを日本国民と思っているのか。まるで明治維新の前からそのままではないか。

We weren't told of the "vent" [of Reactor 1] that the government decided to do. The vent was carried out while the residents were still in town. I wonder if they [the government] think of us as Japanese citizens. This is like pre-Meiji Restoration [when there was no notion of citizens of a nation].

１２日、町民が脱出するなか、双葉厚生病院の前で入院者や近くの老人ホームのお年寄りをバスに乗せる誘導をしていたら、最初の水素爆発が起きた。「ズン」という鈍い音がした。

On March 12, as the residents were fleeing, I was in front of Futaba Kosei Hospital guiding the hospital patients and elderly people from the nearby senior citizens' home to a bus [for evacuation] when the first hydrogen explosion took place. There was a dull "thud".

「ああ、とうとう起きてしまった」と町長は思った。数分して、断熱材（グラスファイバー）のような破片がぼたん雪のように降ってきた。「大きなものはこれぐらいあった」と町長は親指と人差し指でマルをつくった。

"Oh no, it finally happened," the mayor thought. After a few minutes, small debris that looked like glass fiber insulation materials came falling down from the sky like large snowflakes. "Big ones were this big", the mayor puts his thumb and index finger together to form a circle.

双葉厚生病院は福島第1原発から２キロしか離れていない。雪のように断熱材（？）の破片が降るのを、３００人くらいの町職員や医師、看護師らが呆然と見つめた。町長は「これでもう終わった」と思った。

Futaba Kosei Hospital is only 2 kilometers away from Fukushima I Nuclear Power Plant. About 300 people, including municipal workers, doctors and nurses, watched the flakes of insulation materials fall like snow, stunned. The mayor thought, "We're finished."

福島第1原発から断熱材（？）が雪のように降り注ぐ光景を、町長は「それはそれは不思議な光景だった」と振り返る。「そういう映画にでも出てきそうな光景だった」。なすすべもなく、服についた「チリ」を手で払い落とすしかなかった。

The mayor looks back and says, "That was a very, very strange sight. It was like a movie". Not knowing what to do, he just dusted off his clothes with his hand.

The sight of some filament falling from the sky, shining, was also seen by people in Iitate-mura, and Namie-machi.

About "We're finished" remark and the mayor's health:

そうした「福島第1原発からのチリ」を浴びた町長に「それは危険なものだという認識はあったのですか」と問うと「今でも『もう終わった』と思っている」と応えた。「それはどういう意味ですか」と問い返すと「鼻血がとまらない」と言った。

I [Ugaya] asked the mayor who was doused with "dust from Fukushima I Nuke Plant", "Did you think it was dangerous?" He answered, "Even today, I think "We're finished"." "What do you mean?" I asked. He said "Nosebleed hasn't stopped."

「ずっと鼻血がとまらない。鼻をかむと今でも血が出る。たらたら垂れることもある。もう乾燥しているんだかなんだかわからない」

"Nosebleed hasn't stopped. If I blow my nose it bleeds. Sometimes the blood drips. I don't know what's going on, whether the nose is too dry."

「胸から下、すね毛まで毛が抜けてつるつるになった」「銭湯で隣に座ったじいさんが『おい、女みたいにすべすべになっているぞ』というので気づいた」「陰毛だけは大丈夫だった」「体毛がないと肌着がくっついて気持ちが悪い」

"Ive lost almost all body hair from chest down, all the way down to the legs. I noticed it when an old man sitting next to me in "sento" (public bath) said to me, "Hey your skin's smooth like a woman." Pubic hair remains. It's uncomfortable without body hair, because my underwear clings to the skin."

About TEPCO employees who came to Futaba-machi town hall:

３月１１日直後から東電の職員は２人が町役場に来ていた。ふだんから担当している広報課の職員だ。しかしメルトダウンや水素爆発の情報は何も教えてくれなかった。今から思うと顔面蒼白で、知っていたのかもしれない。

Since the accident started on March 11, there were 2 TEPCO employees at the town hall. They were the regular PR department personnel. But they didn't tell us anything about meltdown or hydrogen explosion. In retrospect, the color was drained from their faces. They may have known something [about meltdown and hydrogen explosion].

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"Baseless Rumor" from an LDP Upper House Politician: Explosion in Fukushima I on January 9?

Satsuki Katayama is an LDP member of the Upper House of the Japanese Diet and a former career bureaucrat in the Ministry of Finance.

In her official blog on January 13, 2012, Katayama relates the following rumor:

さきほど、南相馬の元市議会議員から市長に連絡がはいり、1月9日にまた、福島第一で（おそらく4号炉だと思うが）なんらかの爆発が起きており、それを政府が隠している、という話であった。真偽のほどはわからないが、水素爆発ではあっても、核爆発ではないであろう。

Just then, there was a communication from the ex-council member of Minami Soma City to the mayor [of Soma City] that there was some kind of explosion at Fukushima I Nuclear Power Plant on January 9 (probably at Reactor 4 building) and the government is hiding it. I don't know whether it's true or not, but if it is, it is probably a hydrogen explosion, not a nuclear explosion.

Katayama says she was speaking with Hidekiyo Tachiya, mayor of Soma City (north of Minami Soma City) when the mayor related the "rumor" to her. I have no idea why she's allowed to talk loose like this in her official blog.　

So far, it doesn't seem to have gathered much attention in Japan, and many on Twitter ridicule her. But some people are connecting this "rumor" to the massive deployment of the Self Defense Force helicopters on January 9.

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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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#Fukushima I Nuke Plant: TEPCO to RAISE Temperature of RPVs

After 8 and a half months of trying to lower the temperature of the Reactor Pressure Vessels (RPV), which by the way are broken and probably devoid of melted fuel, TEPCO announced they would now try to raise the temperature to avoid hydrogen explosion.

It seems like another non-reason why they do and do not want to reduce the amount of water in the building basements. (If they reduce the water level too much too soon, the ground water will seep in more - something like that. The ground water keeps coming in anyway.)

From Yomiuri Shinbun (11/24/2011):

東京電力は２４日、福島第一原子力発電所１～３号機の原子炉への冷却水の注水量を減らし、圧力容器内の温度を上げる作業を始めたと発表した。

TEPCO announced on November 24 that the work had started on reducing the amount of water being injected to Reactors 1 - 3 at Fukushima I Nuclear Power Plant in order to raise the temperature inside the Reactor Pressure Vessels.

　圧力容器には水素が存在していると考えられ、容器が冷えすぎると中の水蒸気が水になって乾燥し、水素に着火する危険が増すため。東電は同時に、中の水素を排出するため、圧力容器に窒素を注入する準備も始めた。

The RPVs are thought to contain hydrogen. If the RPVs are cooled too much, the steam inside the RPVs will become water, making the atmosphere inside the RPV too dry and increasing the danger of igniting hydrogen. At the same time, TEPCO has started the preparation for injecting nitrogen into the RPVs to expel hydrogen inside the RPVs.

　１号機の注水量を毎時０・５立方メートル（現在の注水量は毎時５・５立方メートル）、２、３号機は毎時１・５立方メートル（同毎時１０立方メートル）ずつ減らす。現在、１～３号機の圧力容器底部の温度は７０度未満に下がっているが、８０度を上回るほどに上げて水蒸気量を確保する。窒素が注入でき次第、注水量を元に戻すという。

The amount of water injected to Reactor 1 will be reduced by 0.5 cubic meter per hour (currently 5.5 cubic meters/hr water is being injected), and the amount of water injected to Reactors 2 and 3 will be reduced by 1.5 cubic meter per hour (current amount is 10 cubic meters/hr). Right now, the temperatures at the bottom of the RPVs of Reactors 1, 2 and 3 are below 70 degrees Celsius. TEPCO wants to raise them to slightly above 80 degrees Celsius to maintain the amount of steam. As soon as nitrogen is injected inside the RPVs, the amounts of water injection will be restored to the existing level, the company says.

So far, nitrogen injection has been to the Containment Vessels.

Well let's see. According to the latest plant status by TEPCO (11/24/2011), the temperatures at the bottom of the RPVs are:

• Reactor 1: 40.4 degrees Celsius
• Reactor 2: 68.3 degrees Celsius
• Reactor 3: 66.6 degrees Celsius

And here's TEPCO's diagram of the effect of the gas management system on Reactor 2's CV. It doesn't make sense whatsoever, as it depicts a reactor that was leaking gas from all over the place but now has stopped leaking, thanks to the gas management system that sucks out the gas from the CV. But isn't it cute that the melted fuel is depicted still nside the RPV?

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#Fukushima I Nuke Plant Reactor 4: TEPCO Says Explosion on 4th Floor Air Duct

from the hydrogen gas that came from Reactor 3 when they did the vent of Reactor 3. TEPCO says in the handout for the press on November 10 that the gas, instead of going up the exhaust stack (oh no here we go again, the stack...) into the air, went to Reactor 4's air duct on the 4th floor.

To prove their case, TEPCO released the photographs on November 10 taken on the 3rd, 4th, and 5th floors of Reactor 4 on November 8. The heaviest damage is on the 4th floor with totally destroyed and disfigured air duct pipes. The rebar of the floor of the 5th floor is lifted upwards, while the floor of the 4th floor is pushed downward. It seems plausible enough that an explosion (there may be more than one, judging by the number of "fires" that Reactor had on March 15 and 16) took place on the 4th floor.

Photographs taken inside Reactor 4 before were rather neat and orderly. But this set of photographs shows the inside to be just as badly destroyed as Reactor 3. Or for that matter, as the top floor of Reactor 1 as seen in the video I posted before.

5th floor: Rebar blown to vertical position


5th floor: Rebar of the floor lifted upward


5th floor: Floor lifted upward


4th floor: Wreckage of air duct


4th floor: Wreckage of air duct, on the floor


4th floor: Floor pushed downward (could be seismic damage?)


3rd floor: Wreckage of air duct

For the complete set of photos, go to TEPCO's "Photos for Press" page, here.

The sequence of the explosive events in Reactors 3 and 4 is this, then:

1. TEPCO did the vent of Reactor 3 at 9:20AM on March 13. The hydrogen gas supposed to have flowed into Reactor 4 through the air duct, to the 4th floor.

2. Reactor 3 blew up at 11:01AM on March 14. The duct connecting Reactor 3 to the exhaust stack (shared by Reactors 3 and 4) was destroyed in the explosion and disconnected from the stack.

3. After nearly 2 days after the hydrogen gas from Reactor 3, as the result of the vent, had filled the air duct on the 4th floor of Reactor 4, Reactor 4 had a hydrogen explosion at 6:12AM on March 15.

The problems I have are these:

• Why did the hydrogen gas from Reactor 3 go to Reactor 4 to begin with, instead of out to the stack and into the atmosphere?

• Why didn't Reactor 4 blow up when Reactor 3 did, if it was filled with hydrogen gas? Instead, it waited another day till it finally blew.

It does look like a hydrogen explosion, as I don't see any evidence of high temperature. The Spent Fuel Pool of Reactor 4 looks pretty much intact.

Any insight, readers?

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#Fukushima I Nuke Plant: Hydrogen Gas Level Increased in Reactor 2

From Asahi Shinbun (10/30/2011):

東京電力は３０日、福島第一原発２号機で原子炉格納容器から吸い出したガスの水素濃度が２．７％に上昇したと発表した。酸素が入って爆発しないよう窒素を送り続けており、「爆発を心配するレベルではない」としている。

TEPCO announced on October 30 that the hydrogen concentration in the gas being sucked out from inside the Containment Vessel of Reactor 2 at Fukushima I Nuclear Power Plant rose to 2.7%. Nitrogen gas is continuously pumped to eliminate oxygen gas, and the company says "It is not the level where we need to worry about explosion."

　２号機では格納容器からガスを吸い出し、フィルターを通して外部に出すガス管理システムが２８日に稼働した。その時点で約１％だった水素濃度が３０日午後５時には２．７％だった。このため水素濃度が上がらないよう窒素を送る量を増やしている。

The gas management system started to operate on October 28 in Reactor 2. The system sucks the gas out of the Containment system, run it through filters and release it outside [the building]. When the system started running, the hydrogen concentration was about 1%. However, at 5PM on October 30, the concentration rose to 2.7%. TEPCO has increased the amount of nitrogen gas [into the Containment Vessel] to prevent the hydrogen concentration from rising further.

　東電原子力・立地本部の川俣晋本部長代理は「空気の流れが起きて水素が漏れ出てきたのではないか」と話している。

TEPCO's Kawamata says, "The gas [inside the CV] has been disturbed [because of the gas management system] and that is stirring up hydrogen."

What a non-answer.

The hydrogen concentration level at which a danger of explosion increases is 4%.

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#Fukushima I Nuke Plant: Hydrogen Gas in a Pipe Leading to Reactor 2 CV

The concentration is less than in the case of Reactor 1 pipe (63%), as it was only 6.5%.

From Yomiuri Shinbun (10/12/2011):

東京電力は１２日、福島第一原子力発電所２号機の格納容器につながる配管から、高濃度の水素が検出されたと発表した。

TEPCO announced on October 12 that the high concentration of hydrogen gas was detected from the pipe that connects to the Containment Vessel of Reactor 2 at Fukushima I Nuclear Power Plant.

　１号機の配管で検出された水素濃度６３％よりも低い６・５％だったが、東電は「格納容器の水素濃度は１％未満なので、配管の濃度は想定より高い」としている。事故直後に発生した水素が配管に押し込められていた可能性が高い。

The concentration was 6.5%, lower than 63% detected in the pipe in Reactor 1 the other day. Nonetheless, TEPCO says "Normally the concentration of hydrogen gas within the Containment Vessel is less than 1%. The concentration detected in the pipe is higher than expected". It is likely that hydrogen gas generated right after the accident remains in the pipe.

　この配管には、格納容器内のガスに含まれる放射性物質をフィルターで除去するシステムを新設する予定で、設置後に水素を抜く。空気中に４％以上の水素と５％以上の酸素が同時にあると爆発の危険性が高まる。

TEPCO plans to install a gas management system to filter out radioactive materials in the gas inside the Containment Vessel. After the installation TEPCO plans to remove hydrogen gas. If there are more than 4% hydrogen and more than 5% oxygen in the atmosphere, a chance of explosion increases.

After the installation?

However, looking at TEPCO's diagram (from press handout on 10/12/2011), this pipe is different from the one they found 63% concentration in Reactor 1. The Reactor 1 pipe was originally used for the core spray system - i.e. it was a pipe for water, so were the valves. But the Reactor 2 pipe and valves on the pipe are for the flammable gas, which I suspect has different specs.

It looks like the ever-incurious TEPCO decided to use the pipe for gas in Reactor 2, probably correctly assuming the valves would stop hydrogen gas from the CV better than the valves for the core spray system.

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#Fukushima I Nuke Plant Hydrogen-Filled Pipe: TEPCO Cut the Pipe, TIG Welded

and everything is dandy now. The whole work took about 5.5 hours on October 9, according to Yomiuri. No information of the radiation exposure for the workers who had to work in the high-radiation Reactor 1 building.

TEPCO, which has caused the worst nuclear disaster in the world since Chernobyl (if not ever), is not at all interested in finding out WHY hydrogen gas was in the pipe.

The information that it was TIG welding came from the independent journalist Ryuichi Kino, who attends almost all TEPCO press conferences.

From TEPCO's handouts for the press on October 10:

(Pipe cutting operation)

(After the pipe was cut: the bottom part was welded shut, but I see duct tape on the top part...)

Good weld, I think. But my understanding is that TIG welding takes more time than other types of welding. I wonder what the radiation exposure for the welder was. I hope he was paid extremely well.

This bottom part of the pipe connects to the Suppression Chamber. The top part is where TEPCO will attach the "gas management" system.

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#Fukushima I Nuke Plant Reactor 1 Hydrogen Gas Conundrum

So TEPCO tried to expel hydrogen gas inside the pipe that leads to the Containment Vessel of Reactor 1 yesterday. But the word is that the work is stopped, because the hydrogen gas in the pipe, which initially had dropped to 0.1% concentration with nitrogen gas injection, went back up again after 2 hours, indicating continuous supply from somewhere (like the CV, maybe).

As the pipe is originally for the water spray system not for hydrogen gas or any type of gas, the hydrogen gas seems to permeate, even if the valves are closed off.

Ooops.

From Yomiuri Shinbun (10/8/2011):

東京電力は８日、福島第一原子力発電所１号機の格納容器につながる配管から高濃度の水素を抜く作業を行ったが、濃度が目標の「１％未満」まで下がらなかったと発表した。

TEPCO announced on October 8 that the concentration of the hydrogen gas in the pipe that leads to the Containment Vessel of Reactor 1 at Fukushima I Nuclear Power Plant didn't go down to the intended level of "less than 1%".

　配管内に窒素を入れて水素を押し出す作業の結果、約６３％だった配管内の水素濃度は０・１％以下に下がった。しかし、１～２時間後に最高３・９％まで再上昇した。水素が依然、配管内に残っているとみられ、東電は９日も同様の作業を行うとしている。

Injection of nitrogen gas in the pipe to expel hydrogen gas lowered the concentration of hydrogen gas in the pipe from 63% to less than 0.1%. However, it wet back up to 3.9% in 1 to 2 hours. Hydrogen gas is considered to still remain in the pipe. TEPCO said it will do the nitrogen injection again on October 9.

　この配管には、格納容器内のガスに含まれる放射性物質をフィルターで除去する「ガス管理システム」を新設する予定。水素濃度が高いと、設置作業中に爆発する恐れがある。

The company plans to install the "gas management system" that will filter the radioactive materials in the gas inside the Containment Vessel. If the concentration of hydrogen gas is high, it may explode during the installation of the system.

Independent journalist Ryuichi Kino tweeted yesterday that TEPCO either doesn't know (or is not telling) the hydrogen gas concentration, if any, inside the Containment Vessel. The company remain curiously incurious.

The Fuku-1 worker tweeted that he suspects hydrogen gas may be coming from the "torus" (= suppression chamber). He says, as does Kino, that the valves for a water system would not stop hydrogen gas even if they are closed.

TEPCO will repeat the same procedure on October 9, hoping to lower the concentration below 1% so that the pipe can be cut safely to install the gas filtering system. And if hydrogen gas keeps coming through the pipe? TEPCO apparently don't care to know.

To recap, their optimistic diagram of the attempt:

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#Fukushima I Nuke Plant: TEPCO Has Started to Expel Hydrogen Gas from the Pipe Leading to Reactor 1 CV

Remember that pipe filled with 63% hydrogen gas (the rest was nitrogen gas, according to TEPCO) that leads to the Containment Vessel of Reactor 1?

TEPCO is removing the gas from the pipe right now. They started at about 2 hours ago (12 noon on October 8, 2011 Japan Standard Time), according to NHK News Japanese (12:57PM JST 10/8/2011):

東京電力福島第一原子力発電所１号機で、格納容器につながる配管に高濃度の水素がたまっている問題で、東京電力は、８日正午すぎから水素を抜き取る作業を始めました。東京電力は、作業は配管に窒素を入れて水素の濃度を下げながら行うため、爆発のおそれはないとしています。

Regarding the hydrogen gas in the pipe that leads to the Containment Vessel of Reactor 1 at Fukushima I Nuclear Power Plant, TEPCO started the operation to expel the gas from the pipe at noon on October 8. TEPCO says there is no danger of explosion as the nitrogen gas will be injected in the pipe to lower the concentration of the hydrogen gas.

福島第一原発１号機では、先月下旬格納容器につながる配管に水素がたまっていることが分かり、東京電力が配管の水素濃度を測定したところ、６１％から６３％と全体の３分の２近くを占める高い濃度だったことが分かりました。この配管の中に酸素はないとみられ、今のところ、爆発のおそれはないとしていますが、今後の復旧作業で配管を切断する計画があるため高濃度の水素が外部に放出されると爆発するおそれがあるとして、８日正午すぎ、配管から水素を抜き取る作業を始めました。水素を抜き取る作業は、配管の中に窒素を入れて、水素の濃度を下げるとともに、発火につながる静電気が起こりにくい特殊なホースをつなぎ込んで、建屋の外に放出するということで、爆発するおそれはないとしています。東京電力は、２号機と３号機についても配管などの水素濃度を調べるよう国から指示を受けていて、今後、１号機と同じように調査を行うことにしています。

In late September it was discovered that the hydrogen gas was in the pipe that leads to the Containment Vessel of Reactor 1. When TEPCO measured the concentration of the gas, it was very high between 61 and 63%. It is considered that there is no oxygen in the pipe, and there is no danger of explosion so far, according to TEPCO. The company plans to cut the pipe later, and to eliminate the danger of explosion if the hydrogen gas in the pipe is released it started to expel the gas at noon on October 8. Nitrogen gas will be injected in the pipe to lower the concentration of the hydrogen gas there, and a special hose that suppresses static electricity which could trigger explosion will be attached to expel the gas outside the building. There will be no danger of explosion, TEPCO says. TEPCO has been ordered by the national government to check the concentration of hydrogen gas in the similar pipes in Reactors 2 and 3, which the company has said it will do in the near future.

TEPCO hasn't said anything definite about where this hydrogen gas came from, other than saying it may be the remaining gas from zirconium (in the cladding) and steam reaction when the fuel was melted down. The company doesn't seem eager to find out.

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TEPCO Now Says There Was No Hydrogen Explosion at Reactor 2

From Yomiuri Shinbun (3:03AM JST 10/2/2011):

福島第一原子力発電所の事故を巡り、東京電力が社内に設置した「福島原子力事故調査委員会」（委員長＝山崎雅男副社長）の中間報告案の詳細が明らかになった。

Details of an interim report by TEPCO's internal "Fukushima nuclear accident investigation committee" (headed by Vice President Masao Yamazaki) were revealed.

　２号機で水素爆発があったとする従来の見解を覆し、爆発はなかったと結論付けた。事故を招いた津波について「想定できなかった」と釈明し、初期対応の遅れについても、「やむを得なかった」との見解を示すなど、自己弁護の姿勢が目立つ。東電は、社外有識者による検証委員会に報告案を諮った後、公表する方針だ。

The committee reversed the company's position that there had been a hydrogen explosion in Reactor 2, and now concluded there was no such explosion. As to the tsunami that triggered the accident, the committee says "it was beyond expectations"; of the delay in initial response to the accident, the committee concludes "it couldn't be helped". Overall, the report looks full of self-justification. TEPCO plans to run the report with the verification committee made of outside experts before it publishes the report.

　同原発では、１号機の原子炉建屋が３月１２日午後に水素爆発を起こしたのに続き、１４日午前に３号機が水素爆発した。さらに１５日早朝、爆発音が響き、４号機の建屋の損傷が確認された。爆発音の直後に２号機の格納容器下部の圧力抑制室の圧力が急落したため、東電は２、４号機でほぼ同時に爆発が起きたとし、政府も６月、国際原子力機関（ＩＡＥＡ）に同様の報告をしていた。

At Fukushima I Nuclear Power Plant, the Reactor 1 reactor building blew up in a hydrogen explosion in the afternoon of March 12, followed by a hydrogen explosion of Reactor 3 in the morning of March 14. Further, in the early morning on March 15, there was an explosive sound, and the damage to the Reactor 4 reactor building was confirmed. Right after the explosive sound the pressure in the Suppression Chamber of Reactor 2 dropped sharply, which led TEPCO to conclude that there were near-simultaneous explosions in Reactors 2 and 4. The Japanese government reported the events as such in the report to IAEA in June.

So then what does TEPCO now think happened in Reactor 2 in the early morning on March 15? Yomiuri doesn't say in the article text, but at the bottom of the illustration that accompanies the article it says:

"There was no explosion, but a possibility of some kind of damage to the Containment Vessel."

So, before TEPCO completely changes story, here's what they say happened on Reactor 2 on March 15 (from the daily "Status of TEPCO's Facilities - past progress" report, page 6):

It says "abnormal sound was confirmed near the suppression chamber" at 6:14AM on March 15.

Now, this is what TEPCO says about Reactor 4 on the same day, about the same time, from Page 16:

It says "an explosive sound was heard" at 6AM on March 15. The Reactor 4 explosion occurred before the Reactor 2 "explosion" which TEPCO now says never happened.

The two sounds are 14 minutes apart, and TEPCO now claims they misheard the second one and there was no explosion in the Suppression Chamber of Reactor 2.

(By the way, the fire spotted at 9:38AM on March 15 on Reactor 4 was never reported to the local fire department or the local government, as I reported on March 15.)

Well I can't wait to read their report and see how they explain away how Reactor 2 is supposed to have spewed more radioactive materials far and wide than any other Reactors.

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Fuku I Hydrogen Gas Update: It Was 63% Concentration

and no need to worry, TEPCO will take care of it.

TEPCO also says since there is no oxygen in the pipe that leads to the Reactor 1 Containment Vessel, there is NO DANGER of explosion.

(Uh huh. "There is no danger of explosion" was what they said to the fire department and the Self Defense Force right before Reactor 1 blew up, and then before Reactor 3 blew up.)

From Yomiuri Shinbun (9/28/2011):

　東京電力福島第一原子力発電所１号機の格納容器に通じる配管から高い濃度の水素が検出された問題で、東電は２８日、濃度は６３％に上ると発表した。

TEPCO announced on September 28 that the concentration of hydrogen gas in the pipe that leads to the Containment Vessel of Reactor 1 at Fukushima I Nuclear Power Plant was 63%.

　配管内で酸素が検出されなかったことから爆発の恐れはないとしているが、東電は２９日に配管内に窒素を注入し、水素を排出する。

TEPCO says there is no danger of explosion because no oxygen was detected in the pipe. The company will inject nitrogen in the pipe on September 29 to expel hydrogen.

　高濃度の水素は、格納容器から放射性物質の漏出を抑えるための排気装置で使用する配管から見つかった。２、３号機でも同様の配管の水素濃度を調べる。

The high concentration of hydrogen was found in the pipe that was to be used as part of the filtering system to suppress the leak of radioactive materials in the Containment Vessel. TEPCO will measure the levels of hydrogen gas in the similar pipes in Reactors 2 and 3.

　水素は、事故直後に核燃料が高温になり燃料を覆う金属と水が反応して発生したものとみられる。空気中に４％以上の水素と５％以上の酸素が同時にあると爆発の危険性が高まる。東電では、格納容器の上部やほかの配管にも水素がたまっている可能性があることから、今後の作業では水素がある可能性を前提にして安全対策を行うとしている。

It is considered that hydrogen gas was generated when the nuclear fuel was heated to high temperature right after the accident and the cladding and water reacted. If there are more than 4% hydrogen and more than 5% oxygen in the atmosphere, the chance of explosion increases. It is possible that there is hydrogen gas in the upper part of the Containment Vessel and in other pipes. The company says it will take measures to address hydrogen gas before proceeding on any work from now on.

Looking at TEPCO's handout for the press on September 28 (Japanese only for now), all they will do is to try to expel hydrogen in the pipe alone by injecting nitrogen from the far end of the pipe. They must be operating on the assumption that all the hydrogen in the pipe is from the initial zirconium cladding and water interaction, not the recent or on-going radiolysis, and once the hydrogen currently in the pipe is expelled, that will be the end of the story.

The idea seems to be that as long as the "MO11" valve is closed off, they can just purge hydrogen from the pipe and not worry about any "fresh supply" if any from the Containment Vessel, and they are free to cut the pipe for their gas management system.

There's a word for that in Japanese, "ba-atari-teki", and it can be translated as "ad hoc". The word seems to describe how TEPCO has been dealing with the crisis very well. (Remember the bath salt as tracer?)

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Fuku I Hydrogen Gas Update: TEPCO Was Going to Cut the Pipe Without Testing

In case you're wondering what happened to the precise measurement of the hydrogen gas inside the pipe that leads to the Reactor 1 Containment Vessel, the worker who tweets from Fukushima I Nuke Plant says (in Japanese) it will be a few more days till TEPCO can even get the instrument for measurement.

"I'm so glad that we didn't cut the pipe. It may sound incredible but there was no measurement [of flammable gas] scheduled in the initial work plan. But they decided to measure one day before they were going to cut the pipe. Close call. There is no instrument that can measure hydrogen alone, at Fuku I. It will come on September 28, so the measurement may be done on either September 28 or 29. The result seems obvious, but..."

You have to give TEPCO some praise for their dare. They were going to cut the pipe without measuring what could be inside the pipe. But don't breathe a sigh of relief just yet, because the worker also says TEPCO currently plans to cut the pipe anyway while purging the hydrogen gas inside the pipe with nitrogen gas. There seems to be no plan to deal with anything else than this particular pipe, although the regulatory agency NISA has asked TEPCO to conduct similar tests in Reactors 2 and 3.

TEPCO sort of knows how to operate a nuclear power plant. They have zero expertise in how to fix an utterly broken nuclear power plant, but they continue to be allowed to attempt, to the horror and dismay of the northern hemisphere.

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TEPCO: It May Be 100% Hydrogen Gas Inside the Pipe Connecting to Reactor I Containment Vessel

First it was reported that "over 10,000 ppm" or over 1% of hydrogen gas was detected at 2 locations in the pipe that connects to the Containment Vessel of Reactor 1 at Fukushima I Nuclear Power Plant. Then it was allegedly "over 40,000 ppm" or 4%.

According to Jiji Tsushin, TEPCO thinks the hydrogen gas concentration in the pipe may be 100%. 1,000,000 ppm.

Still, TEPCO says possibility of explosion is not necessarily high because there is no source nearby that could cause sparks. (Never mind that they were going to use blow torches to cut the pipes...)

Jiji Tsushin (12:28PM JST 6/24/2011):　

福島第１原発１号機の格納容器につながる配管から１％を超える濃度の水素が検出された問題で、東京電力は２４日、配管内部の気体はほとんどが水素である可能性が高いと発表した。東電の松本純一原子力・立地本部長代理は同日の記者会見で、「着火源がないので、直ちに爆発のリスクが高いとは言えない」と述べた。

Concerning the detection of hydrogen gas in more than 1% concentration inside the pipe that connects to the Containment Vessel of Reactor 1 at Fukushia I Nuclear Power Plant, TEPCO announced on September 24 that it is highly probable that almost all the gas inside the pipe is hydrogen gas. TEPCO's Matsumoto said in the press conference, "Since there is no source for sparks, it cannot be said that there is a high risk of explosion immediately".

　東電によると、２３日午後に配管の出口部分の気体を複数回測定したところ、いずれも「水素を含む可燃性ガスが１００％以上」との数字が出た。今後、水素だけを計れる測定器を用意し、正確な濃度を測定する方針。

According to TEPCO, they measured the gas at the pipe exit several times in the afternoon of September 23. Each time, the result showed "flammable gas including hydrogen gas, over 100% ". The company plans to use the instrument that only measures hydrogen, in order to accurately measure the concentration of hydrogen.

It's so TEPCO. First they used the device that could only measure up to 10,000 ppm, and that maxed out. Then they apparently used the device that could only measure up to 40,000 ppm, and that maxed out. So they brought in a bit more powerful instrument, but it measures all flammable gases including hydrogen.

I suppose they were hoping that one of these devices would suffice. But now, even they have admitted that the air inside the pipe may be 100% hydrogen.

(H/T WaveCepter311)

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It Is More Than 40,000 ppm Hydrogen Gas, not 10,000 ppm Inside Reactor 1 CV Pipe

(UPDATE 9/24/2011: It may not be even 40,000 ppm or 4%. TEPCO now says it may be 100%, or 1 million ppm, hydrogen gas. See my post.)

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Just last night I reported on the hydrogen gas detected inside the pipe leading to the Reactor 1 Containment Vessel. TEPCO, according to the report and by their own press conference, said the density was "over 10,000 ppm".

Well. It was an understatement if the worker who tweets from Fukushima I Nuke Plant is correct. He says they went back to test the locations again with the meter that can measure up to 40,000 ppm. The meter maxed out.

It is over 40,000 ppm, or over 4%.

The media and TEPCO reported the number as "over 10,000 ppm", which is technically correct. "Over 40,000 ppm" is definitely over 10,000 ppm.

The worker tweeted:

そして今日は4%まで計れる測定器を準備して測定したら4%Maxだったから、またまた作業中止で発表になったんだ。オイラは化学の事詳しくないからわからなかったけど、水素が4%を越えると爆発する可能性があるみたいなんだ。

And today [September 23; they knew about "over 10,000 ppm" the day before] we went to measure using the meter that can measure up to 4%. It was 4% max. So the work [to cut the pipe] was canceled, and TEPCO made an announcement. I didn't know, as I'm not very knowledgeable about chemistry, but it seems there's a chance of explosion if hydrogen gas is more than 4%.

He is wondering if zirconium cladding is still melting and reacting, producing hydrogen.

But as one reader of this blog points out after putting two posts from yesterday together (the one about Reactor 4 SFP water radiolysis and the one about the hydrogen detection in the Reactor 1 CV pipe), it may be possible that the water radiolysis is happening somewhere deep inside the reactor building where boiling water is getting irradiated and generating hydrogen gas.

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More than 10,000 ppm Hydrogen Detected Inside the Pipe That Leads to Containment Vessel of Reactor 1

Speaking of hydrogen, TEPCO just announced it detected hydrogen at 2 locations inside the pipe that leads to the Containment Vessel of Reactor 1.

TEPCO's handout for the press on September 23 says (not their exact words):

• TEPCO was planning to cut the pipe for the spray system to install a gas management system for the Reactor 1 Containment Vessel;
• Before cutting, they measured hydrogen inside the pipe to be safe. More than 10,000 ppm hydrogen was detected;
• They won't cut the pipe until the safety is assured.

10,000 ppm is equivalent to 1%. As we know from the previous post, if the hydrogen density is more than 4% in the air, a hydrogen explosion could happen.

The company assures us, according to Yomiuri Shinbun, that the existence of hydrogen in the pipe had been expected, although the density was higher than expected, and that there would be no danger of an explosion.

So if TEPCO says "more than 10,000 ppm", it either means they didn't bring the instrument that could measure higher than 10,000 ppm, or they don't want you to know how high.

I wouldn't be surprised at either. We haven't heard anything more about the location near the exhaust stack for Reactors 1 and 2 that measured "more than 10 sieverts/hour". Was it 11 sieverts? 20 sieverts? 50 sieverts?

It could be the same here in the pipe. "More than 10,000 ppm" could be 11,000 ppm, 20,000 ppm, or 40,000 ppm.

Yomiuri also mentions the reassuring word from TEPCO:

東電は、４月から格納容器への窒素を注入しており爆発に不可欠な酸素がほとんどないと思われることから、直ちに爆発の心配はないとしている。

TEPCO has been injecting nitrogen into the Containment Vessel since April, and it is considered there is hardly any oxygen that would be required for an explosion, according to the company. TEPCO says there is no immediate danger of explosion.

Here we go again, "no immediate" danger. (Calling Mr. Edano...) That word makes me nervous.

Besides, the very fact that the water being injected into the Reactor Pressure Vessel somehow ends up in the basement means the Containment Vessel is leaking badly. Nitrogen that's been injected since April is leaking, as the pressure doesn't go up at all. How would they know that there is hardly any hydrogen left? It could easily leak in from outside, couldn't it?

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How Reactor 4 at Fukushima I Nuke Plant "Exploded", According to TEPCO

TEPCO is trying to explain what happened to Reactor 4 at Fukushima I Nuclear Power Plant. The explanation is that hydrogen gas along with radioactive materials from Reactor 3 flowed to the main exhaust stack, which then flowed backwards from the exhaust stack through Reactor 4's Emergency Gas Treatment System into the reactor building of Reactor 4.

To support this hypothesis, TEPCO released this diagram on August 27 press conference, which shows the surface radiation levels of the gas filters. Highest radiation is at the filter closest to the exhaust stack, lowest radiation at the filter closest to the reactor building.

The radiation seems low though, considering the amount of hydrogen it must have taken to render the building in a wreck, and therefore the amount of radioactive materials that came with the hydrogen gas must have been high. TEPCO's Matsumoto's explanation was because the gas from Reactor 3 came through the Suppression Chamber - i.e. wet vent. (Matsumoto's answer is via Ryuichi Kino's tweet; Kino is an independent journalist covering TEPCO from the day one of the crisis.)



Reactors 1 and 3 exploded with explosive sounds that were clearly heard and felt in the nearby towns. But there wasn't any such sound when Reactor 4 supposedly exploded. I say supposedly, because no one seem to know for sure exactly what happened, including TEPCO.

Cabinet Secretary Edano at that time said "explosion" of some sort at Reactor 4 on March 15, but the media report was focused on the mysterious "fire" that was spotted by a TEPCO employee who didn't bother to report to the local fire department (as he should have). The fire died down on its own, but then another fire flared up again the next day.

The initial report on the Reactor 4 incident was that one or two wall panels in the northwest corner of the reactor building were blown out, and there was some damage on the roof. It sounded minor.

Then all of a sudden we were shown the wreckage. One or two wall panels blown out? It was more like "one or two wall panels remaining".

Read my earliest post on Reactor 4, on March 15. No photo was released that day.

Here's what TEPCO has put down in the plant status report (page 16). TEPCO does say "explosion" but that's decidedly not what was reported back then:

• At approx. 6:00am, March 15, an explosive sound was heard and the damage in the 5th floor roof of Unit 4 reactor building was confirmed. At 9:38am, the fire near the northwest part of 4th floor of Unit 4 reactor building was confirmed. At approx. 11:00am, TEPCO employees confirmed that the fire was extinguished.

• At approx. 5:45am on March 16, a TEPCO employee discovered a fire at the northwest corner of the reactor building. TEPCO immediately reported this incident to the fire department and the local government andn proceeded with the extinction of fire. At approx. 6:15am, TEPCO employee confirmed at the site that there were no sign of fire.

It's about time we get the much better, and precise picture of what happened in the early days of the crisis, now that we've been better educated since March 11.

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