TEPCO to Redefine Its Idea of "Criticality"

Tokyo Shinbun (11/7/2011) reports:

東京電力は六日、福島第一原発の臨界判定基準を見直す方針を明らかにした。経済産業省原子力安全・保安院に先月提出した報告書では、半減期の短い希ガスが検出されないことを条件としていたが、今月二日に２号機で自発核分裂により発生したとみられる放射性キセノンを検出。実態と合わなくなり、修正を余儀なくされた。

On November 6, TEPCO disclosed its policy to review the standard to determine whether criticality has happened at Fukushima I Nuclear Power Plant. The report the company submitted to the Nuclear and Industrial Safety Agency under the Ministry of Economy, Trade and Industry defined the condition of criticality as whether noble gas with short half life was detected. However, radioactive xenon was detected in Reactor 2 on November 2, which is thought to have been created by spontaneous fission. TEPCO's definition didn't match the actual situation, and the company has no choice but redefine what it considers "criticality".

　二日にキセノンを検出した際、東電は「臨界の可能性がある」と発表したが、その後、検出量が少なかったことなどから「自発核分裂によるものだった」と訂正していた。

When xenon was detected on November 2, TEPCO announced "There is a possibility of criticality". However, the company corrected it as "spontaneous fission" partly because the amount of xenon detected was small.

　東電の川俣晋原子力品質・安全部長は、六日の記者会見で「再臨界かどうかでは、大変心配をおかけした。報告書の改訂版を準備している。その中で見解を示す」と述べた。

TEPCO's general manager Kawamata said in the press conference on November 6, "We're sorry we've had you worried over whether re-criticality happened or not. We are preparing the revised report, and we will elaborate on our view in that report."

　十月十七日に保安院に提出していた「中期的安全確保」に関する報告書では、キセノンなど半減期の短い希ガスが検出されないことが臨界判定基準だった。

In the report submitted to the NISA on October 17 on ensuring security in medium-term, the standard to judge the occurrence of criticality was the presence or absence of noble gas with short half life, such as xenon.

If this is true, then whoever crafted the October report to the NISA didn't know how xenon is apparently generated in spontaneous fission inside a normal reactor; and TEPCO has been operating this nuke plant for almost 40 years.

(Note to officials in Vietnam, Turkey, and India: Are you sure you want to import the Japanese nuclear power plant system?)

Tweet

#Fukushima I Nuke Plant Xenon Detection Announcement: "Wag the Dog"?

The Nuclear and Industrial Safety Agency (NISA) has now concurred (Yomiuri Shinbun 11/7/2011) with TEPCO's conclusion that it was just ordinary spontaneous fission, not re-criticality, which generated xenon gas in Reactor 2 of Fukushima I Nuclear Power Plant.

Here's a view from the supposed insider, the worker who tweets from Fukushima I Nuclear Power Plant who seems to work for one of the top-tier subcontractors.

He wonders why TEPCO announced the xenon detection when it did and strongly hinted that it was from re-criticality. I wonder the same thing, particularly when krypton-85 and xenon-131m were detected in even greater amounts in Reactor 2 Containment Vessel back in August.

From the worker's tweets on the subject:

11/3/2011 tweets:

自発核分裂のキセノンは定検中でもあることで、いつもの東電ならそこまで調べてから発表するはずなんだけど…？

Xenon from spontaneous fission is routinely detected in the regular maintenance. TEPCO normally make announcements after exhausting all possibilities.

まぁ政府や保安員にはタイムリーに伝えるけど、今まで報道発表する時はいつも調べて検討してから結果を発表してたんだよなぁ…。それが昨日に限って再臨界なんて東電が一番言いたくない表現で国民にインパクトを与え今日になって自発核分裂で安心させたのか？

They provide information to the government and the NISA in a timely manner. But when it comes to announcing to the public in the press conference, they would always investigate thoroughly before announcing. But yesterday, they shocked the public with the word "re-criticality" which TEPCO would never want to use. And today they are saying don't worry it is just spontaneous fission?

昨日の会見ではサンプリングを増やして調査に時間がかかりそうな感じだったのに、いつもなら時間をかけるのに…？まして昨日は細野大臣が1Fに来てたけど公には報道されてない。

In the yesterday's press conference [when they hinted re-criticality] it seemed like it would take long time to investigate, increasing the sampling. As they would do in normal circumstance. By the way, Minister Hosono [in charge of nuclear accident] was at the Fuku-1 plant yesterday but it was not reported in the media.

昨日あった出来事でインパクトある報道で打ち消したかったもの…？情報操作したかったもの…？

What event happened yesterday which they wanted to cover up with even more sensational news [like "re-criticality" at Fukushima I Nuke Plant]? What did they want to manipulate?

His answer to his own question is also shared by many people in Japan:

玄海原発再稼動かぁ…

Could it be the restart of Genkai Nuclear Power Plant?

Reactor 4 of Genkai Nuclear Power Plant in Saga Prefecture, which is operated by the scandal-ridden Kyushu Electric, restarted on November 2 despite strong protests and opposition in the neighboring municipalities and from all over the country. The company just did it with the approval from the pro-nuke governor of Saga Prefecture (whose father worked for Kyushu Electric) and the NISA, saying there is no need for consent from the community (Mainichi Shinbun 11/2/2011) at all.

The same vein of thinking as the petty bureaucrats in the Tokyo Metropolitan government.

But back to the xenon/krypton detection in Reactor 2 of Fuku-I Nuke Plant, not all nuclear experts are convinced of spontaneous fission, particularly those not so intimately connected with the government. I am reading what they have to say, and will report back if I can digest.

Maybe the news they wanted to cover up with a hasty declaration of re-criticality possibility and dismissal the very next day was the real re-criticality. Next time when xenon-135 is detected, no one will pay attention. "Oh it's just routine spontaneous fission, happens all the time."

Tweet

Xenon Detection in Reactor 2: Different Detection Limits on Different Days at Different Sampling Locations

Spontaneous fission, says TEPCO, the NISA says they cannot rule out criticality, and no one cares as no one believes either of them.

Here's another reason not to believe them, or take their words at face value: TEPCO tested at different locations and for different durations for the nuclides in the gas that was sucked out of the CV of Reactor 2.

Take a look at the table below, which I compiled from TEPCO's handout for the press on November 2, 2011. For each nuclide, the detected amount and the detection limit are listed for October 28, November 1, and November 2.

I was fooled when I first looked at the result of October 28, when TEPCO started the gas management system in Reactor 2. Krypton and xenon were all below detection limit. Then on November 1, they were all detected, and on November 2 xenon-133 (half life 5 days) seemingly dropped out, but other nuclides increased slightly. I thought "Something must have happened between October 28 and November 1."

That was what some reporters at the press conference on November 2 were wondering, and TEPCO's Matsumoto went along with them, not saying anything definite but hinting that the fission event was recent.

WRONG. These reporters didn't look at the fine print. (Well, neither did I...)

On October 28, the detection limits were HIGH, including those for radioactive iodine and cesium (not in the table above), indicating TEPCO didn't test long enough. That can also be inferred from the "date of sampling" information, because for October 28, no duration is indicated in the TEPCO's press handout. The nuclides may well have been in the gas on October 28 but weren't detected.

Then I also noticed that the samples were taken at different locations. On October 28, the sampling location was "gas sampling system intake"; on November 1 and 2, it was "gas sampling system dust radiation monitor".

For some unknown reason, between October 28 and November 1, someone somewhere in TEPCO seems to have decided to test longer, and at a different location. It is also possible that the dust radiation monitor was simply not ready on October 28, although I doubt that even TEPCO would start running the system before the system components were put in place and functional.

And do not be fooled that xenon-133 stopped being detected on November 2. Look at the detection limit for xenon-133 on November 1 and compare it to November 2: 10^-6 vs 10^-5. Since the amount of xenon-133 found on November 1 was in the order of 10^-6, it may well have been present in the sample on November 2, but not detected.

Here's TEPCO's handout for the press (11/2/2011):

October 28, 2011 (2nd measurement):

November 1, 2011:

November 2, 2011:

Here's the Reactor 2's gas management system overview, as released by TEPCO on October 27, 2011:

TEPCO and the Japanese government don't even know where the corium is or whether the Containment Vessel has been breached (most likely). Sucking the gas out of the Containment Vessel, which may or may not have the corium, to "reduce the amount of radioactive materials" is like trying to scoop water with a sieve.

(H/T anon reader)

Tweet

Xenon in Reactor 2: TEPCO Now Says "Spontaneous Fission" of Curium

After confidently saying it may have been criticality in the press conference on November 2, TEPCO's Matsumoto now says it is spontaneous fission of curium in the reactor.

On the other hand, the Nuclear and Industrial Safety Agency, who was skeptical of criticality yesterday, now says, "We cannot rule out the possibility of localized criticality."

OK it's a "good cop, bad cop" routine, or a "covering all the bases" approach. If both "spontaneous fission" and "criticality" are mentioned in the same news, the Japanese government/TEPCO can say "See, we told you, either way."

From NHK News (11/3/2011):

東京電力福島第一原子力発電所の２号機内の気体から放射性物質のキセノンが検出された問題で、東京電力は、検出したキセノンの量などの解析結果から、核分裂が連続する臨界が起きたのではなく、別の放射性物質が自然に核分裂したことが原因と判断したことを明らかにしました。

Regarding the radioactive xenon detected from the gas inside Reactor 2 of Fukushima I Nuclear Power Plant, TEPCO revealed that the analysis of the amount of xenon detected led the company to conclude that it was a natural fission of a radioactive material, not criticality where nuclear fission takes place continuously.

福島第一原発２号機では、１日と２日、格納容器の中の気体を採取し、分析した結果、核分裂した時にできる放射性物質のキセノン１３５がごく微量、検出され、東京電力は、最近核分裂反応が起き、核分裂が連続する臨界が一時的に一部の場所で起きた可能性もあるという見方を示していました。

The gas from inside the Containment Vessel of Reactor 2 was sampled and analyzed on November 1 and 2. A minute amount of xenon-135 was detected, and TEPCO said it was possible that there had been a recent nuclear fission, and that the localized criticality took place temporarily.

これについて東京電力は、もともと核燃料の中にあるキュリウム２４２とキュリウム２４４という放射性物質が、自然に核分裂をしてキセノンを発生することから、その量をもとにキセノンの濃度を計算したところ、今回、検出された濃度とおおむね一致したということです。

Since curium-242 and curium-244, the radioactive materials which exist in nuclear fuel, undergo natural fission and generate xenon, TEPCO calculated the density of xenon based on the amount of these nuclides. The calculation mostly matched the density detected from the samples.

また、仮に臨界が起きていたとすると、キセノンの濃度は今回よりも大幅に高くなるということで、これらの分析から、今回のキセノンは臨界に伴って発生したものではなく、「自発核分裂」によるものだと判断したということです。「自発核分裂」は、ウランではない別の放射性物質が自然に核分裂する現象で、臨界は伴わないということです。東京電力は、これらの調査結果を経済産業省の原子力安全・保安院に報告し、妥当かどうか評価してもらうとしています。

According to TEPCO, the density of xenon would be much greater if there was a criticality. Xenon this time therefore is from spontaneous fission, not from criticality, says TEPCO. "Spontaneous fission" is a phenomenon in which radioactive materials other than uranium fissions naturally, and it does not cause criticality. TEPCO says it will submit the report of the findings to the Nuclear and Industrial Safety Agency under the Ministry of Economy, Trade and Industry, who will evaluate whether the conclusion is appropriate.

福島第一原発２号機内の気体から放射性物質のキセノンが検出された問題で、東京電力が核分裂が連続する臨界が起きたのではなく、別の放射性物質が自然に核分裂したことが原因と判断したことについて、原子力安全・保安院の森山善範原子力災害対策監は「自発核分裂の可能性は高いと思うが、科学的に見て、局所的な臨界の可能性をすべて否定できるわけではないので、東京電力の調査内容を含めて専門機関の分析結果を見て評価したい。さまざまなリスクを分析したうえで、ホウ酸水の注入など、万一の事態に備えた設備面での対応ができているかどうか、東京電力に確かめていきたい」と話しています。

The NISA spokesman Yoshinori Moriyama says about TEPCO's analysis, "We think it is highly possible that it is a spontaneous fission, but we cannot rule out completely the possibility of localized criticality. We would like to evaluate TEPCO's analysis as well as analysis by experts. We will assess various risks and make sure TEPCO has emergency measures ready, including injecting water with boric acid."

Uh... what about krypton-85? Is this produced in spontaneous fission of curium? If it is spontaneous fission, why was not happening on October 28?

Tweet

Reactor 2 CV Gas Analysis on November 2: Slight Increase in Xe-131m, Xe-135, 100-Fold Increase in Krypton-85 from November 1

TEPCO disclosed the latest result of the analysis of the gas coming from the Containment Vessel of Reactor 2 at Fukushima I Nuclear Power Plant, along with the result of the analysis done on October 28, 2011 when the gas management system started operating in Reactor 2.

There was no xenon or krypton detected on October 28. Then they were there in the analysis on November 1.

From TEPCO's handout for the press (11/2/2011), from November 1 to November 2,

• Krypton-85 (half life 10.8 years) went from 3.6 x 10^-3 to 5.3 x 10^-1, 100-fold increase

• Xenon-131m (half life 12 days) went from to 5.3 x 10^-4 to 6.1 x 10^-4

• Xenon-133 (half life 5 days) went from 6.5 x 10^-6 to below detection limit

• Xenon-135 (half life 9 hours) went from 1.3 x 10^-5 to 1.7 x 10^-5.

The unit is Bq/cubic centimeter. According to wiki, "About three atoms of krypton-85 are produced for every 1000 fissions (i.e. it has a fission yield of 0.3%)". It sure looks like a nuclear chain reaction happening, i.e. re-criticality, the possibility of which TEPCO's Matsumoto has already admitted.

The numbers for krypton and xenon are still under evaluation.

Result of November 1, 2011:

Result of November 2, 2011:

Tweet

More on Xenon Detection in Reactor 2 (TEPCO's Press Conference)

Xenon was detected in the order of 10^-5 (ten to the power of minus 5) per cubic centimeter, says TEPCO's Matsumoto in the press conference that is on-going right now in Japan. It is significant enough to conclude it is not from March. (TEPCO by the way started to netcast its press conference live, here.)

Matsumoto does think a localized, small-scale, and/or temporary nuclear fission may have occurred in Reactor 2. But not a large, sustained re-criticality, judging by the parameters (temperature, pressure, etc.).

Xenon-133's half life is 5 days, and xenon-135's half life is 9.2 hours. As to whether the amount of xenon is large or not, the company is evaluating with the help of experts.

Possibilities:

• Neutrons that exist inside the reactor hitting uranium or plutonium

• Curium-244, -242, causing "spontaneous fission"

• (I missed the third possibility that Matsumoto mentioned.)

It would be difficult to deny that the same thing is not happening in Reactors 1 and 3, says Matsumoto.

He thinks the possibility of re-criticality is low with the damaged fuel melted together with control rods and other things. Even if it does happen as the reactor is cooled further and the amount of water increases, TEPCO thinks it can be controlled by carefully monitoring the temperature and pressure.

(Reporters seem to want to reassure themselves by saying "In a nutshell, even if it is in re-criticality, TEPCO can control it, right?")

TEPCO's handout for the press on November 2, the result of gas analysis in Reactor 2 is reproduced below. The numbers are still being evaluated, says Matsumoto:

Tweet

Fuku-I Nuke Plant: Nuclear Fission in Reactor 2? Xenon-133, -135 Detected

(UPDATE: Additional information from TEPCO's press conference on November 2 in a new post.)

TEPCO poured the water with boric acid into the reactor to prevent re-criticality.

From NHK News (6:38AM JST 11/2/2011):

東京電力福島第一原子力発電所の２号機の格納容器から、核分裂反応が起きた時にできる放射性物質のキセノンが検出され、東京電力は核分裂反応が起きている可能性が否定できないとして、原子炉に核分裂反応を抑えるホウ酸水を注入しました。

Xenon has been detected in the Containment Vessel of Reactor 2 at Fukushima I Nuclear Power Plant. Xenon is created when there is nuclear fission.

福島第一原発の２号機では、先月２８日から格納容器の中から気体を吸い出し、フィルターを通して放射性物質を取り除く装置の運転を始めていて、この装置の出口付近で放射性物質の種類や濃度を測定して分析しています。その結果、１日に行った分析で、核燃料のウラン２３５が核分裂してできる放射性物質のキセノン１３３と、キセノン１３５が検出されたということです。

The gas management system has been operating since October 28 in Reactor 2 to suck out the gas from the Containment Vessel and filter out radioactive materials. TEPCO has been analyzing the gas to identify the nuclides and density. The analysis done on November 1 found xenon-133 and xenon-135, which are created when uranium-235 undergoes nuclear fission.

キセノン１３３は放射性物質の量が半分になる半減期が５日と短いため、東京電力は、再び核分裂反応が起きている可能性が否定できないとして、午前３時前から１時間にわたって原子炉に核分裂反応を抑えるホウ酸水の注入を行いました。

Xenon-133's half life is 5 days. TEPCO says it could not rule out the possibility of nuclear chain reaction happening again, so the company poured water with boric acid into the reactor to suppress the nuclear chain reaction for one hour starting 3AM [on November 2].

東京電力によりますと、原子炉の温度や圧力、それに敷地周辺の放射線量を計測しているモニタリングポストの値に大きな変動はないため、核分裂反応が起きていても規模は小さいとしています。経済産業省の原子力安全・保安院によりますと、検出されたキセノンの濃度は低く、原子炉の温度などに変化がないことから、今のところ燃料が再び溶融しているとは考えにくいとしていますが、ホウ酸水を注入したあともキセノンの検出が継続されないかどうか、状況を見極めるとしています。

According to TEPCO, there is not much change in the reactor temperature or pressure, or at the monitoring posts that measure radiation levels in and around the plant compound. Therefore, if the nuclear chain reaction is happening, it is small-scale, says the company. The Nuclear and Industrial Safety Agency says since the density of xenon detected is low and there is no change in the reactor temperature and other parameters, it is hard to imagine the fuel is melting again. But the Agency says it will monitor the situation to see if xenon continues to be detected after pouring in the water with boric acid.

Reactor 2 is where hydrogen gas concentration was rising the other day.

Tweet

#Fukushima I Nuke Plant: Some Kind of Fissioning Still Somewhere?

Radioactive iodine (I-131) inside the silt fence at the water intake canal for the Reactor 2 continues to be detected, although the amount is nothing like what it used to be back in April.

From TEPCO's press releases, the amount of iodine-131 inside the silt fence at the water intake canal for the Reactor 2, in becquerels/liter

6/22: 310
6/23: 1,000
6/24: 180
6/25: 1,300
6/26: 1,600
6/27: 1,200

Tweet

Arnie Gundersen: "On-and-Off Recriticality Possible in Reactor 3"

I was listening the podcast of the interview Arnie Gundersen gave to Chris Martenson the other day (in order to translate into Japanese) and noticed something I had missed when I skimmed through the transcript for my post.

Gundersen is saying that 10% of the fuel core of the Reactor 3 may be repeating a re-criticality, on and off:

"Unit 3 may not have melted through and that means that some of the fuel certainly is lying on the bottom, but it may not have melted through and some of the fuel may still look like fuel, although it is certainly brittle. And it's possible that when the fuel is in that configuration that you can get a re-criticality. It's also possible in any of the fuel pools, one, two, three, and four pools, that you could get a criticality, as well. So there’s been frequent enough high iodine indications to lead me to believe that either one of the four fuel pools or the Unit 3 reactor is in fact, every once in a while starting itself up and then it gets to a point where it gets so hot that it shuts itself down and it kind of cycles. It kind of breathes, if you will.

"I think it's a relatively significant amount – maybe a tenth of the nuclear reactor core starts back up and shuts back down and starts back up and shuts back down. And that’s an extra heat load; you are not prepared to get rid of one tenth of a nuclear reactor’s heat by pumping water in the top."

Hiroaki Koide of Kyoto University suspected an on-and-off recriticality in the Reactor 1 back in early April when TEPCO announced, supposedly erroneously, chlorine-38 was detected. Dr. Tetsuo Matsui of Tokyo University suspected recriticality in the Reactor 2 and/or the Reactor 4 Spent Fuel Pool. Gundersen suspects an on-and-off recriticality in the Reactor 3 (or any of the Spent Fuel Pools).

Below is the chart of iodine-131 detection at the Federal Office of Radiation Protection in Germany, plotting the CTBTO station data from around the world. Station 38 is Takasaki, Gunma Prefecture in Japan, 218 kilometers (135 miles) from Fukushima I Nuclear Power Plant. I always thought it was rather peculiar that there seemed to be periodic spikes in the amount of iodine-131 (also of cesium-137 but to a lesser degree) followed by a relatively calm, steady decline.

Could these spikes indicate what Gundersen is talking about? On-and-off recriticality?

Tweet

#Fukushima I Nuke Plant Reactor 1: Seawater Injection Halted on March 12 at Prime Minister's Order

Well, since this prime minister claimed to be a "nuclear expert" during the early stage of the Fukushima crisis, he must have good reasons.

Since the fuel was likely to have melted down by the morning of the day the seawater injection started, maybe it wouldn't have mattered anyway.

Kyodo News Japanese (9:28PM JST 5/20/2011):

１号機の海水注入を５５分間中断　再臨界恐れ首相指示

Injection of seawater into the Reactor 1 RPV was interrupted for 55 minutes, at the order from the Prime Minister who feared recriticality

　地震翌朝に燃料が溶け落ちるメルトダウンが起きたとみられる福島第１原発１号機で、政府が公表した３月１２日の海水注入開始時刻の前に東京電力は注入を開始、政府の指示で５５分間注入を停止していたことが２０日、分かった。

It was revealed on May 20 that TEPCO had started the injection of seawater into the Reactor 1 at Fukushima I Nuke Plant sooner than the government had disclosed previously, but the company halted the injection for 55 minutes at the order from the government.

　海水注入の遅れで被害が拡大したとの批判があり、専門家は「海水注入を続けるべきだった」と指摘している。

There are some criticisms that the damage got more grave due to the delay in the seawater injection. Experts say the seawater injection should have been continued.

　政府の対策本部の資料では、海水注入の開始時刻は３月１２日午後８時２０分としていた。だが、東電が５月１６日に公表した資料では、午後７時４分に海水注水を開始し、同２５分に停止、午後８時２０分に海水とホウ酸による注水開始、と記載されている。

The government information identifies the start of seawater injection at 8:20 PM on March 12. However, according to the data released on May 16 by TEPCO, the injection of seawater started at 7:04PM, but was halted at 7:25PM, and resumed at 8:20PM with boric acid mixed in the seawater.

　政府筋によると、午後７時すぎの海水の注入は現場の判断のみで開始。原子力安全委員会への問い合わせで海水注入で再臨界が起こる恐れがあることが判明したとして、菅直人首相がいったん注水を止めさせたという。その後、問題ないことが分かり、ホウ酸を入れた上での注水が再開された。

According to government sources, the seawater injection at 7PM was the decision made by the people at the plant. After inquiring at the Nuclear Safety Commission and [supposedly] finding out that there was a danger of recriticality if seawater was poured into the RPV, Prime Minister Naoto Kan ordered the halt. Afterwards, it turned out that there was no such danger, and the seawater injection restarted with boric acid.

　１号機は地震、津波による全電源喪失のため、３月１２日朝には燃料の大半が溶け落ちていたとの暫定評価を、東電が公表している。

TEPCO has already announced its provisional assessment that due to the power loss resulting from the quake and tsunami, most of the fuel in the Reactor 1 had melted down by the morning of March 12.

Tweet

#Fukushima I Reactor 3: TEPCO Pouring Boric Acid to Prevent Recriticality

Yomiuri Shinbun (10:02PM JST 5/15/2011):

　東京電力は１５日、福島第一原子力発電所３号機の原子炉で再臨界が起きないよう、原子炉の冷却水に、中性子線を吸収するホウ酸を溶かした上で、同日から原子炉への注水を始めたと発表した。

TEPCO announced on May 15 that it started to use boric acid in the reactor cooling water for the Reactor 3 at Fukushima I Nuclear Power Plant to prevent recriticality from happening. Boric acid absorbs neutrons.

　１、２号機も今後、同じ措置を取る。

TEPCO plans to do the same for the Reactors 1 and 2.

　再臨界は連続的な核分裂が再び起こる現象。１～３号機の原子炉圧力容器には当初、冷却のために海水を注入した経緯があり、東電はその塩分が中性子 線を吸収すると見ていた。ホウ酸を冷却水に溶かすのは、冷却水を海水から淡水に替えて以降、塩分濃度が下がっていると見られるためだ。

Recriticality is when the nuclear chain reaction is restarted. There is salt in the Reactor Pressure Vessels of the Reactors 1, 2 and 3, as TEPCO initially poured seawater to cool the RPVs. TEPCO thought the salt would absorb neutrons. TEPCO has decided to use boric acid in the cooling water because the level of salt in the cooling water may have decreased since TEPCO switched the cooling water from seawater to regular water.

　一方、３号機の圧力容器は、上端部の温度が急上昇している。東電は「注水用配管から水が漏れている可能性がある」として、１２日からは別の配管を 追加し、二つの配管で毎時計１２トンを注水した。１４日からは注水量を毎時計１５トンに増やしたが、上端部の温度は１５日午前５時までの２４時間で４６・ ５度上昇し、２９７度になった。東電は、「注水がまだうまくいっていない」と見ている。

In the meantime, the temperature at the top of the Reactor 3 RPV has risen rapidly. TEPCO increased the amount of cooling water to 12 tons per hour on May 12 using two water feeding systems, then to 15 tons per hour on May 14. However, the temperature at the top of the RPV increased by 46.5 degrees Celsius in 24 hours to 297 degrees Celsius as of 5:00AM on May 15. TEPCO thinks there's a problem with the pipes that feed water into the RPV.

In the latest measurement data (11:00AM 5/15) released by the Ministry of Economy, Trade and Industry (METI) , that temperature (the 4th column) appears to have dropped slightly to 291.7 degrees Celsius, although the data table is put up sideways and it is a bad scan and hard to see. The second digit could be 9, 8, or 3. An age-old trick by bureaucrats to discourage people from seeing the data... (My neck is hurting from trying to read the number.)

Tweet

Recriticality at #Fukushima I Nuke Plant: Japanese Researcher Says Nuclear Chain Reaction May Have Reignited Long After Tsunami Disabled the Plant

Tetsuo Matsui is a professor at University of Tokyo's Institute of Physics. On May 2, he submitted his paper titled "Deciphering the measured ratios of Iodine-131 to Cesium-137 at the Fukushima reactors" to arXiv.org, in which he says "The data of the water samples from the unit-4 cooling pool and from the sub-drain near the unit-2 reactor show anomaly which may indicate, if they are correct, that some of these fission products were produced by chain nuclear reactions reignited after the earthquake." (quote taken from his paper)

Chain nuclear reactions reignited = recriticality

That is what some of the non-mainstream researchers like Japan's Hiroaki Koide of Kyoto University and the US's Arnie Gundersen of Fairewind Associates have been saying all along, that there may have been recriticality in some of the reactors at Fukushima I Nuclear Power Plant.

Now the Japanese mainstream Tokyo University professor is saying it. TEPCO's and the Japanese government's acknowledgement can't be that far away. (And no doubt it will be presented as "it's nothing, it's safe.")

From The Physics arXiv Blog at Technology Review at MIT (5/9/2011):

Chain Reactions Reignited At Fukushima After Tsunami, Says New Study: Radioactive byproducts indicate that nuclear chain reactions must have been burning at the damaged nuclear reactors long after the disaster unfolded

..... Today, Tetsuo Matsui at the University of Tokyo, says the limited data from Fukushima indicates that nuclear chain reactions must have reignited at Fuksuhima up to 12 days after the accident.

Matsui says the evidence comes from measurements of the ratio of cesium-137 and iodine-131 at several points around the facility and in the seawater nearby. He has calculated what the starting ratio must have been by assuming the reactors had been operating for between 7 and 12 months.

He says the ratios from drains at reactors 1 and 3 at Fukushima are consistent with the nuclear reactions having terminated at the time of the earthquake.

However, the data from the drain near reactor 2 and from the cooling pond at reactor 4, where spent fuel rods are stored, indicate that the reactions must have been burning much later.

"The data of the water samples from the unit-4 cooling pool and from the sub-drain near the unit-2 reactor show anomaly which may indicate, if they are correct, that some of these fission products were produced by chain nuclear reactions reignited after the earthquake," he says.

These chain reactions must have occurred a significant time after the accident. "It would be difficult to understand the observed anomaly near the unit-2 reactor without assuming that a significant amount of fission products were produced at least 10 - 15 days after X-day," says Matsui.

So things in reactor 2 must have been extremely dangerous right up to the end of March.
....

The blogpost above includes some imprecise information that does not appear in the original paper. For those of you who want to read Matsui's original paper (9 pages with calculations), the link is this: http://arxiv.org/PS_cache/arxiv/pdf/1105/1105.0242v1.pdf

ArXiv.org was originally hosted at the Los Alamos National Laboratory and is currently hosted by Cornell University. Researchers submit electronic preprints in the fields of mathematics, physics, astronomy, computer science, quantitative biology and statistics, which can be accessed via the world wide web. In many fields of mathematics and physics, almost all scientific papers are self-archived on the arXiv. Though it is not peer-reviewed, there are moderators in each field who review the submissions. (from Wikipedia.)

(h/t あ)

Tweet

#Fukushima I Nuke Plant: TEPCO Stating the Obvious After 5 Weeks - "Part of Fuel Rods May Have Melted"

Following the cue from Nuclear and Industrial Safety Agency, who finally admitted that the fuel pellets may have melted, TEPCO now says the fuel rods may have melted in the Reactor 1.

Even the inept Japanese government already admitted, through the Prime Minister's advisor, that they knew the core had melted but they didn't feel like announcing it.

But don't worry, says TEPCO, chlorine-38 wasn't detected after all (as we now interpret the data according to the advice of the experts under the government guidance), so there is no "re-criticality" as some have alleged happening.

(Expect the admission of re-criticality in about 3 weeks.)

From Yomiuri Shinbun (4/20/2011):

Junichi Matsumoto of TEPCO admitted on April 20 [in the press conference] that there was a possibility that the fuel rods have melted in the Reactor 1, where about 70% of the fuel rods may have been damaged". Matsumoto said "the melted fuels may be stuck in the middle of the Pressure Vessel and hasn't dropped to the bottom."

He cited the lower temperature at the bottom of the Pressure Vessel than at the top as the reason for his assumption. So far, TEPCO has described the damage of the fuel rods as probably "holes on the surface, or the cracked cladding", and has avoided commenting on the fuel melt.

　東京電力の松本純一・原子力立地本部長代理は２０日、燃料の約７０％が損傷しているとみられる福島第一原子力発電所１号機の原子炉について「燃料 が溶融している可能性がある」と認め、「圧力容器の中ほどに水あめのような状態で引っかかり、底までは落ちていないだろう」と述べた。

　理由として、圧力容器の底部の温度が上部より低いことを挙げた。

　東電はこれまで、燃料の損傷状況について「表面に穴が開いたり、燃料を詰めた合金製の被覆管が割れたりしているのではないか」と説明し、溶融については明言していなかった。

And this is the new and improved data on water in the Reactor 1 turbine room from March 24 that have been re-evaluated for accuracy, and the proof that there is no re-criticality (no chlorine-38; on the table it says "below detectable range"). The second column from the left is the new and improved interpretation, the third column from the left is the original announcement on March 25. The column on the right indicates reasons for change (if any), and in the case of chlorine-38, the reason was "Based on the guideline from NISA to avoid misinterpretation of the data, the nuclides were identified and the level of radiation determined by the main peaks."

To browse through the charts, go here and click on the PDF files at the bottom. They are in Japanese. No English version has been posted yet.

Tweet

#Fukushima I Nuke Plant: Kyoto University Researcher "Reactor 1 May Be Undergoing "Recriticality"

Evidence? Chlorine-38.

I posted this on my Japanese blog for the Japanese readers. I'm putting out the summary for the English readers here, too.

A nuclear researcher at Kyoto University (which is considered one of the two most prestigious national universities, the other one being Tokyo University) has reversed his opinion and now says the Reactor 1 may be experiencing the "recriticality".

His name is Hiroaki Koide, assistant professor at Kyoto University's Research Reactor Institute who belongs to the Nuclear Safety Research Group at the Research Reactor Institute. He has given interviews on TV and radio, mostly in Kansai stations and not aired in Kanto (where Tokyo is), and would be considered one of the "sceptics" of the official story about Fukushima I Nuke Plant that everything is safe, getting under control.

There ARE researchers in Japan who go against the mainstream government scholars. Koide is one of them (and far from being the most critical), and there are others from universities other than the top few schools (and therefore they don't get hardly any airtime on the Japanese MSM). But thanks to talk radio shows and the Internet (hey it's the same as in the US), at least a small portion of the Japanese people are getting the "alternative" reality other than what's given by the government and the MSM.

This is from the transcript of the interview (in Japanese, NOT the literal translation) Koide gave on April 5, 2011 on Osaka's MBS Mainichi Broadcasting Radio:

"The Fukushima I Nuke Plant accident is not winding down at all. I think I have to revise my opinion which was too optimistic."

- What was too optimistic?

"We thought the reactors "cold stopped", which means the uranium fission stopped. But now I've started to think the fission has started again. In other words, the reactor has become "critical" again - which we call "recriticality"."

- Professor Koide, you were of the opinion that the recriticality was not happening.

"Yes, and I've changed my mind. It may be happening."

- On what evidence?

"First, the level of iodine[-131] is not decreasing; it is increasing. Iodine[-131]'s half life is 8 days. It has been more than 3 weeks since the accident, so the level of iodine[-131] should be about 1/10 of the initial level measured. Second, the presence of chlorine-38 was detected from the contaminated water in the turbine building [he doesn't say which one]."

- What about chlorine-38?

"Well, if chlorine-38 was detected [according to TEPCO], and that can only mean "recriticality".

Chlorine-37 is a stable isotope, and it exists in salt in the sea water. TEPCO had poured literally tons and tons of sea water into the Reactor Pressure Vessels at Fukushima. The way the stable chlorine-37 becomes highly unstable chlorine-38 (half-life 37 minutes) is for chlorine-37 to acquire neutron.

The only way for neutron to be present near chlorine-37 is for uranium to go critical and emit neutron.

That's what Fairewinds Associates' Arnie Gunderson said in his April 3 video, and that's probably why IAEA mentioned the possibility of "recriticality" on March 30.

Koide thinks the recriticality may be happening in the Reactor 1 where the fuel rods may have been melted down most (Koide thinks there is no cladding left, and the tiny uranium pellets are forming a heap at the bottom of the RPV), but says the other two reactors (2 and 3) are also vulnerable if TEPCO cannot cool them sufficiently and the core melt continues.

He also suspects TEPCO is not pouring enough boron to prevent fission.

Maybe that's another item at Fukushima I that's missing: boron.

It took almost 3 weeks for TEPCO to admit they didn't have enough dosimeters for the workers.

Don't hold your breath for a TEPCO's announcement that they are out of boron. Maybe they can dump bath salt in the pressure vessels and that may stop the fission.

And remember, repeat the mantra of the Japanese government: it is safe.

Tweet

#Fukushima I Nuke Plant: Neutron Measured Only at the West Gate?

I just noticed a peculiar thing, after watching the video by Arnie Gunderson from Fairewinds and Associates at Zero Hedge. Gunderson is the one who said his previous video that there was no water in the Reactor 4 Spent Fuel Pool. (For that video, go to my post here.)

In the new video, he is talking about on-and-off "inadvertent re-criticality" in the Reactor 1 possibly happening, and pointed to the neutron ray detection at the plant as one of the evidence (the other one being tellurium-129).

Now, about the peculiar thing I noticed. I went to TEPCO's site and looked up their monitoring data. Neutron ray is being monitored, but the only data that TEPCO is willing to show is the neutron ray at the West Gate. There is no other neutron measurement data at other monitoring posts in the compound.

Either TEPCO measures neutron at the West Gate only, or it is not sharing the data from other points.

Here's the latest monitoring data from TEPCO. Go to page two for neutron ray. It is measured at the West Gate, and it's below detection range. That's all we need to know. No need to ask questions about other monitoring posts.

By the way they still don't post the data from their regular 8 radiation monitoring systems on the perimeter of the plant, even though the power was finally restored to them on April 1. So they are not working? Or...?

Tweet

More on IAEA's "Re-Criticality at Fukushima Plant": Bloomberg Japan vs Bloomberg US

That news is there in Bloomberg Japan's site in Japanese, which is basically what CNN reported in their 2nd update. But it is nowhere to be found on Bloomberg US site, yet. Interesting.

From Bloomberg Japan (in Japanese; 4:40AM JST 3/31/2011)

ＩＡＥＡ原子力安全局：福島第一原発、局所的に再臨界の可能性も(1)

　　３月30日（ブルームバーグ）：国際原子力機関（ＩＡＥＡ）は30日のウィーンでの記者会見で、東京電力福島第１原子力発電について、「再臨界」の可能性もあるとみて、分析作業を進めていることを明らかにした。

On March 30, IAEA disclosed in their press conference in Vienna that there is a possiblity that Tokyo Electric Fukushima I Nuclear Power Plant has achieved "re-criticality", and IAEA are proceeding with analysis.

　ＩＡＥＡ原子力安全局担当のデニス・フローリー事務次長は30日、「最終判断ではない」と発言。「局所的に起こる可能性があり、放出が増える可能性もある」と述べた。

IAEA nuclear safety director Denis Flory said "It is not IAEA's final assesment" He also said, “This may happen locally and possibly increase the releases.”

Bloomberg Japan's article says at the bottom of the article that it has been translated, supposedly from English. But as I said above, I can't find it at Bloomberg US site.

Oh I forgot! Fukushima I Nuclear Power Plant's accidents are so "over-hyped" outside Japan and that the US media should "apologize" for over-hyping! My bad..

So far, as of 5:47AM JST on March 31 in Japan, NOTHING on Kyodo News, Yomiuri, Asahi, Nikkei, Mainichi, Sankei. Only Bloomberg Japan.

Tweet

IAEA: #Fukushima I Nuke Plant Might Have Re-Criticality

from Zero Hedge:

Remember Fukushima?

• IAEA SAYS `THERE MIGHT BE RE-CRITICALITY' AT FUKUSHIMA
• IAEA COMMENTS AT PRESS CONFERENCE IN VIENNA
• IAEA DIRECTOR GENERAL YUKIYA AMANO SPEAKS AT BRIEFING IN VIENNA
• IAEA HAS NO INFORMATION FROM TEPCO ON NEUTRON DETECTORS

If indeed the reactor has gone critical again, the whole concrete dome idea may have to be promptly scrapped.

From CNN:

Update 2: The IAEA has said that the Fukushima nuclear power plant may have achieved re-criticality. “There is no final assessment,” IAEA nuclear safety director Denis Flory said at a press conference on Wednesday, according to Bloomberg News. “This may happen locally and possibly increase the releases.”

Don't see anything at Bloomberg site yet.

Tweet