Wednesday, November 30, 2011

"Now They Tell Us" Series: TEPCO Admits Reactor 1 Corium May Be 65 Centimeters into the Concrete Pedestal of Containment Vessel

(UPDATE: See TEPCO's drawing of Reactor 1 in my next post.)
(UPDATE 2: Government-commissioned research institute says "corium 2 meters into the concrete". See my post.)

There you go! It took TEPCO only 8 and a half months to say what many people have been saying at least for 8 months.

The corium has long escaped the Reactor Pressure Vessel as admitted by TEPCO and the government. There are experts (like Hiroaki Koide) who have suggested the corium may have already left the Containment Vessel of Reactor 1, and TEPCO itself said back in May that Reactor 1 CV may have a 7-centimeter hole. Now the company says the corium may have eaten into the concrete floor of the CV to about 65-centimeter deep.

For Reactors 2 and 3, TEPCO thinks (hopes, wishes...) that a good chunk of the corium dropped from the RPV onto the CV. No mention whether the corium there is eating into the concrete or not.

From NHK News (11/30/2011; quick translation, subject to revision):

溶融燃料 相当量が格納容器に(11月30日 19:00更新)

Significant amount of melted fuel in the Containment Vessel

東京電力福島第一原子力発電所の事故で、メルトダウンが起きた1号機の燃料は、鋼鉄の原子炉の底を突き破って相当の量が格納容器に落下し、容器の底のコンクリートを溶かして最大で65センチ浸食していると推定されることが、東京電力の解析結果から分かりました。

It has been discovered by TEPCO's analysis that the significant amount of Reactor 1's melted fuel pierced through the steel Reactor Pressure Vessel and dropped onto the Containment Vessel, then melted the concrete at the bottom of the CV. It is estimated that the melted fuel may have eaten into the concrete to maximum 65 centimeters deep.

2号機と3号機についても一部の燃料は格納容器に落下していると推定しており、改めて事故の深刻さが浮き彫りになっています。

For Reactors 2 and 3, TEPCO also estimates that part of the fuel has dropped to the Containment Vessels, showing how severe the accident has been.

福島第一原発の1号機から3号機については、核燃料が溶け落ちるメルトダウンが起き、一部の溶けた燃料が原子炉から格納容器に落下したとみられていますが、事故から8か月以上がたっても、詳しい状況は分かっていません。

In Reactors 1 thorugh 3 of Fukushima I Nuclear Power Plant, core meltdowns have occurred, and it is considered that part of the melted fuel has dropped from the RPVs to the CVs. However, the details are not yet known even after more than 8 months since the accident started.

これについて東京電力や国内の複数の研究機関が、これまで得られた原子炉の温度や注水状況などから溶けた燃料の状態を異なる方法で解析し、30日、国が開いた研究会で結果を発表しました。

Using different methods, TEPCO and various other research institutions have been analyzing the state of the melted fuel based on the reactor temperatures and the amount of water being poured into the reactors, and the results were announced on November 30 at a workshop held by the national government.

このうち東京電力の解析では、最も厳しい評価をした場合、1号機については、すべての燃料が溶け落ち、原子炉の底を突き破って相当の量が格納容器に落下したと推定しています。

TEPCO's result shows that, in the most severe case, all of the fuel would have melted, of which a significant portion pierced through the bottom of the Reactor Pressure Vessel and dropped onto the Containment Vessel.

格納容器の底にはコンクリートがあり、さらに鋼鉄の板で覆われています。

There is a concrete platform [pedestal] at the bottom of the Containment Vessel, which is then covered with steel plates.

燃料が格納容器の底に落ちると、高熱で反応してこのコンクリートを溶かして浸食するということで、最悪の場合、1号機で65センチの深さまで達すると推定しています。

When the melted fuel drops to the bottom of the Containment Vessel, a core-concrete reaction takes place at a high temperature, melting the concrete. In the worst case, in Reactor 1, the melted fuel could reach 65 centimeters deep into the concrete.

最もコンクリートの薄いところでは、格納容器の鋼板まで37センチしかないということで、改めて事故の深刻さが浮き彫りになっています。

At the thinnest part of the concrete, it is only 37 centimeters to the outer steel plate of the Containment Vessels. This is a very severe accident.

また、2号機と3号機についても、最悪の場合、それぞれ57%と63%の燃料が溶け落ちて、その一部が格納容器に落下したと推定しています。

TEPCO also estimates that in the worst cases for Reactors 2 and 3, 57% and 63% of the fuel have melted, respectively, and part of the fuel dropped onto the Containment Vessels.

東京電力によりますと、原子炉と格納容器の温度は、21日現在で、いずれも100度以下になっていて、溶けた燃料は水で冷却されており、コンクリートの浸食は止まっていると評価しています。

According to TEPCO, the temperatures of the RPVs and CVs as of November 21 are all below 100 degrees Celsius, the melted fuel is cooled by the water, and the erosion into the concrete has stopped.

研究会では、このほかの研究機関の解析結果も発表され、複数の結果を基に原子炉や燃料の状態について議論されました。
東京電力や国は、今回の解析結果をさらに詳しく分析し、今後の廃炉に向けて核燃料をどのように取り出すかなどについて検討することにしています。

In the workshop, the results from other research institutions were announced, and the experts discussed the conditions of the reactors and fuel based on those results. TEPCO and the national government plans to further analyze the result of the study, and determine how to remove the fuel for decommissioning the reactors.

原子力安全基盤機構、技術参与の阿部清治さんは、東京電力の解析結果について「間違っているとは思わないが、まだ第一歩だと受け止めている。解析結果は一つだけでは答えを導き出すことができないからだ。今後はいろいろな解析結果を積み重ねて、事故の実態を分析していく必要がある」と話しています。

Seiji Abe, technical advisor to the Japan Nuclear Energy Safety Organization (JNES) says about TEPCO's analysis, "I don't think it is wrong, but it is only the first step. You can't get answers from only one analysis. We will need to understand the situation from various analyses."

TEPCO's presentation is posted on their site, but only in Japanese:
http://www.tepco.co.jp/nu/fukushima-np/images/handouts_111130_07-j.pdf

Here's the list of documents that were presented in the workshop on November 30:

Status of the fuel core in Reactors 1 through 3:
http://www.tepco.co.jp/nu/fukushima-np/images/handouts_111130_09-j.pdf

Plant parameters after the accident (including data that hasn't been disclosed so far)
http://www.tepco.co.jp/nu/fukushima-np/images/handouts_111130_03-j.pdf

Modification of JAEA model
http://www.tepco.co.jp/nu/fukushima-np/images/handouts_111130_04-j.pdf

Various approaches taken to estimate the condition of the fuel
http://www.tepco.co.jp/nu/fukushima-np/images/handouts_111130_05-j.pdf

MAAP analysis and core-concrete reaction
http://www.tepco.co.jp/nu/fukushima-np/images/handouts_111130_06-j.pdf

(You can still flip through the pages to see the charts and graphs.)

TEPCO's drawing that indicates the thickness of the CV concrete:

19 comments:

Anonymous said...

psst.

Reactor 3, 16 meters 65 centimeters

Majia's Blog said...

The radiation levels, as measured by the US's EPA radnet hit 650 CPM beta today in Phoenix. This is a record "official" high and we are not currently fully under the jet stream. 30 to 60 is normal.

Tomorrow or the next day we'll be more directly engulfed by the jet stream and I imagine our beta levels will skyrocket still higher.

I've been watching the Tepco cam and considerable steam appears to be coming from reactors 1 and in the vicinity of the common spent fuel pools.

I don't believe anything is stable.

The infrared image of reactor 1 released a few weeks ago (posted at Fukushima Diary) seems to indicate the core is definitely out of any containment, based on the amount of red splotched around.

It seems that the situation is worsening dramatically.

Atomfritz said...

Long documents to sift through.
Particularly interesting drawings in the _09 document that even a granny understands... molten out cores, boiling water table in the containments etc.

Page 31-34 show all three reactors, like in next ex-skf post the image of reactor 1.

Page 29 shows ceiling floor infrared photo from March 20, up to 129 degrees hot. Either I have forgotten them already or these weren't published back in March with that temperature data.

Page 1-45 and 46 shows some EPRI diagrams that I also never have seen before. They suggest that in containment vessel there are hydrogen igniters.
Do the Fukushima reactors have such things, are they functional, connected and working? Or is Tepco wholly dependent on nitrogen injection forever to avoid explosions in the containment?

Just my thoughts on that little in the documents that I could understand.

Regarding the concrete melt-through, I believe it could be even deeper, maybe even through the containment vessel lining. This would be not much apparent, but later when the containment cracks and microcracks led to big radiation seeping through the containment, causing difficult radiation situations in the basement and in the "tent".

At least, personally I am optimistic that no corium has molten/will melt through the building bottom, as it probably has become colder than the melting point anywhere in this more-than-eight-meter of concrete still existent (according to Tepco images in these documents).

However, we still have to believe that it's a "cold shutdown" as Mother Tepco tells us...
...even if boiling and steaming water wells in the reactor building may suggest otherwise.

(see the video here: http://ex-skf.blogspot.com/2011/06/video-of-4-sieverthour-steam-gushing.html)

R.B. said...

Blame it on G.E. with their Nuclear Division. They knew about this Cooling Problem Breech Problem back in 1973, with 3 Engineers who resigned, stressing that the Nuclear Mechanism for Cooling had very little redundancy on the BWR Nuclear Reactor design. G.E. was warned back in 1973, with this and didn't take heed to this critical Problem

Anonymous said...

Fuck 'em all

robertb said...

These strokes need to be held liable for they're death machines

robertb said...

*Their

Bruce Hayden said...

If TEPCO finally admits what many of us have known or surmised from the first few weeks, it would be a safe bet that the situation is double or triple or worse than the scenario they admit exists. Pathological liars rise to the top of corporations and governments (one and the same) in these times. I second the "fuck 'em all" comment.

Anonymous said...

Is the containment vessel 8 meters thick or only 1 meter?

Yosaku said...

Majia,

I wouldn't worry too much about those Phoenix readings. Just a quick scan of Radnet's pre March 11 historical data will show you that 650 cpm Beta is not all that uncommon in Phoenix. For example, the reading hit 628 on Feb 2, 688 on Jan 16, and 778 on Dec 11. These readings clearly were not due to Fukushima.

(By the way, I think you may have picked this up from the Alexander Higgins blog. I would take everything he says with a grain of salt--he is not exactly the most reliable source.)

Yosaku said...

arevamirpal::laprimavera,

In your second paragraph you say, "The corium has long escaped the Reactor Pressure Vessel AND the Containment Vessel of Reactor 1".

However, the supporting information seems to say that the corium only escaped the RPV and not the CV. Am I missing something here?

Thanks.

Majia's Blog said...

Yosaku said...

How did you get the EPA radnet data for beta history when the link is broken for the data inquiry exchange site?

A working link would be appreciated if you have one.

I've found Alexander higgins' site to be very reliable - the data posted there have always matched the data I found using the radnet system, while it still functioned accessibily.

arevamirpal::laprimavera said...

Well that looks like several different lines of thought that failed to be written out, in haste. I corrected it, and it is as follows:

"The corium has long escaped the Reactor Pressure Vessel as admitted by TEPCO and the government. There are experts (like Hiroaki Koide) who have suggested the corium may have already left the Containment Vessel of Reactor 1, and TEPCO itself said back in May that Reactor 1 CV may have a 7-centimeter hole. Now the company says the corium may have eaten into the concrete floor of the CV to about 65-centimeter deep."

Majia's Blog said...

Yosaku

I found another way in to the data exchange. The readings for the two dates you suggest are highly unusual and are not representative, although they can be found in a couple of instances like in 1986
http://www.rrt5.org/acp/docs/App6_AirMonitoringGuidelines.pdf

For background on risk for radiation, read the EPA's guide for emergency responders in radiological emergencies
http://www.rrt5.org/acp/docs/App6_AirMonitoringGuidelines.pdf

"If readings are three times background, responders consult with a Health Physicist."

Yosaku said...

arevamirpal::laprimavera,

No worries--I think the rewrite looks great.

Yosaku said...

Marja,

Try the following link: https://cdxnode64.epa.gov/radnet-public/query.do. This should enable you to look up the historical data. If you need any assistance, just let me know--I'm happy to help.

As for whether or not that data was representative, I just went back to the three months before the earthquake and found the highest readings for each month. From that it seems that the recent readings in the 650 cpm range are not all that unusual.

Anonymous said...

Sounds like gently breaking the news to the cancer patient.

Apart from that, I am angry because they seem to have based this analysis, in part, on unreleased data.

Had they released it, many people and research institutions could have duplicated the work. Confidence in the results would have increased.

Atomfritz said...

Dear Majia,

as you live in Phoenix and are downwinder of the Palo Verde nuclear plant, there is good chance that you don't need to look as far as Japan to find out the cause of the high CPM counts.

It could even be possible that these high counts are wholly legal releases during maintenance of the plant, or just blowout of radioactive gases to use up the permitted annual release limit. The latter is common practice at nuclear plants, as it is always cheaper to release nuclear waste into the environment instead of storing it.

Palo Verde is an aging nuclear plant that also got uprated, meaning that its releases will be way higher than a new plant that is operated conservatively.

As the permissible releases are usually very high, it is very difficult to find out by internet search what is actually allowed. Looks like some people prefer that the public doesn't know what stunning high releases the nuclear stations are allowed.
Common permissible release for Tritium alone in nuclear plants is several thousand curies per annum.

In German nuclear plants the peak radioactivity of the gas that is released in the maintenance periods reaches the magnitude of millions becquerels/cubic meter. And remember, this is permissible release, just "normal" operation!

So please check out what is happening in Palo Verde. If they are currently blowing out the contents of their off-gas tanks, this might be tens, hundreds or even thousands of curies released over a few days, maybe even completely legally.

Then you and the other downwinders will wonder about high CPM counts, of course. Homemade ones, not imported.

Anonymous said...

"I've found Alexander higgins' site to be very reliable"

Comedy Gold!!

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