Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[tsutsuji]

Xenon detected in unit 2: http://enenews.com/tepco-press-handout-xenon-detected-reactor-2-containment-vessel-9-hour-half-life
http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120214_07-e.pdf

These results are hardly different from those of 6 February, are they?

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120208_07-e.pdf Fukushima Daiichi unit 2 charcoal filter nuclides, February 6

 

[Yamanote]

These results are hardly different from those of 6 February, are they?

Right. That's why I ignore all the stuff on enenews.

 

[etudiant]

Right. That's why I ignore all the stuff on enenews.

Well, ENENews has been in the forefront of the disaster focused reporting, so they deserve to be taken with more than a pinch of salt.
That said, we've not had afaik a nuclear reactor of this size experience as catastrophic a failure, so Fukushima is writing new chapters in the book.
The layman's understanding is that there is no plausible mechanism to achieve recriticality in the damaged fuel, but that residual decay heat is a serious issue. Is this incorrect and are there plausible ways the damaged fuel can be brought back to criticality in any substantial way as a consequence of this accident?

 

[Rive]

The layman's understanding is that there is no plausible mechanism to achieve recriticality in the damaged fuel, but that residual decay heat is a serious issue. Is this incorrect and are there plausible ways the damaged fuel can be brought back to criticality in any substantial way as a consequence of this accident?

ftp://ftp.cordis.europa.eu/pub/fp5-euratom/docs/09-sara.pdf

So they think it's likely happens in some circumstances.

But Tsutsuji is right about the Xenon levels, so in this particular case it's not likely happened.

 

[Yamanote]

Thanks Rive, very interesting!

Enenews compares two different measurement anyway...
So they seem to be more into headlines than into explanations and solutions. Not helpful to me.

 

[etudiant]

ftp://ftp.cordis.europa.eu/pub/fp5-euratom/docs/09-sara.pdf

So they think it's likely happens in some circumstances.

But Tsutsuji is right about the Xenon levels, so in this particular case it's not likely happened.

Thank you, Rive, for a useful link.
This is an informative study, but dealing with a much lesser accident than Fukushima.
They posit a situation after an accident where the control rods have melted but the fuel is largely intact, and resume cooling water injections with unborated water. Obviously the fuel geometries maximize the neutron capture once the water moderates the neutrons emitted.
Here we have damaged/destroyed fuel, maybe in heaps, maybe melted into corium, under a shower of borated water, so we have fast neutrons, with no moderator around and bad geometries.
How is recriticality possible in those conditions?

 

[Jim Lagerfeld]

They posit a situation after an accident where the control rods have melted but the fuel is largely intact, and resume cooling water injections with unborated water. Obviously the fuel geometries maximize the neutron capture once the water moderates the neutrons emitted.
Here we have damaged/destroyed fuel, maybe in heaps, maybe melted into corium, under a shower of borated water, so we have fast neutrons, with no moderator around and bad geometries. How is recriticality possible in those conditions?

How about this paper - it seems to me to better match the current situation, although apologies in advance if I have missed something obvious. They suggest that based on a simulation similar to three mile island, cycling criticality events are quite possible in a damaged fuel debris bed, although they conclude that they should be self-regulating and not large enough to destroy the containment (average 5-7GJ):

"Recriticality Energetic of a Hypothetical Water Reflood Accident in a Damaged Light Water Reactor"

http://www.osti.gov/bridge/purl.cover.jsp?purl=/16911-VGVXER/webviewable/

As far as the boration is concerned, if the water is flowing through the primary containment like a sieve at many tons per hour, I can not see how sporadically injecting large amounts of boron would maintain any kind of stable boration - I think the media people have misread the boron injections.

During the last injection of boron, the TEPCO daily update hinted that their motivation was actually that by rapidly increasing the injection rate they might raise the level of the water in the reactor and reflood a damaged section of the core and inadvertently increase reactivity:

http://www.tepco.co.jp/en/press/corp-com/release/12020805-e.html

"In order to avoid the increasing
possibility of re-criticality to occur, which might be brought up by
sudden cold water injection, resulting in the rise of water density
inside the reactor, we injected boric acid into the reactor as a safety
countermeasures against the re-criticality from 0:19 am to 3:20 am on
February 7, which was before increasing the amount of injection water,
and changed the amount of the core spray system injection water from 3.7
m3/h to 6.7m3/h at 4:24 am (the amount of the continuing feed water
system injection is 6.8m3/h)."

So rather than temp going up -> better add boron, it seems like temp going up -> better increase water injection -> better borate reflood water in case more reactive fuel is flooded. Looking at it that way, the boron injections suddenly seem less knee-jerk.

 

[etudiant]

How about this paper - it seems to me to better match the current situation, although apologies in advance if I have missed something obvious. They suggest that based on a simulation similar to three mile island, cycling criticality events are quite possible in a damaged fuel debris bed, although they conclude that they should be self-regulating and not large enough to destroy the containment (average 5-7GJ):

"Recriticality Energetic of a Hypothetical Water Reflood Accident in a Damaged Light Water Reactor"

http://www.osti.gov/bridge/purl.cover.jsp?purl=/16911-VGVXER/webviewable/

As far as the boration is concerned, if the water is flowing through the primary containment like a sieve at many tons per hour, I can not see how sporadically injecting large amounts of boron would maintain any kind of stable boration - I think the media people have misread the boron injections.

During the last injection of boron, the TEPCO daily update hinted that their motivation was actually that by rapidly increasing the injection rate they might raise the level of the water in the reactor and reflood a damaged section of the core and inadvertently increase reactivity:

http://www.tepco.co.jp/en/press/corp-com/release/12020805-e.html

"In order to avoid the increasing
possibility of re-criticality to occur, which might be brought up by
sudden cold water injection, resulting in the rise of water density
inside the reactor, we injected boric acid into the reactor as a safety
countermeasures against the re-criticality from 0:19 am to 3:20 am on
February 7, which was before increasing the amount of injection water,
and changed the amount of the core spray system injection water from 3.7
m3/h to 6.7m3/h at 4:24 am (the amount of the continuing feed water
system injection is 6.8m3/h)."

So rather than temp going up -> better add boron, it seems like temp going up -> better increase water injection -> better borate reflood water in case more reactive fuel is flooded. Looking at it that way, the boron injections suddenly seem less knee-jerk.

Thank you for a very relevant insight.
This paper certainly seems to fit the bill pretty well. It suggests that recovering the fuel with water has in fact quite a powerful impact on the potential for criticality, which is certainly news to me. That implies that the future performance of this facility is in fact somewhat unpredictable, rather than being bounded by the decay heat curve. It also means that getting a good handle on the distribution and location of the fuel in these reactors is of more than academic importance.

 

[Atomfritz]

It also means that getting a good handle on the distribution and location of the fuel in these reactors is of more than academic importance.

Yes.
There was a large thread about the topic "what caused the explosion of reactor 3" or the like which got deleted by the moderators.

My impression is that this happened because this thread threatened to become blasphemic in the way that it could show that recriticality issues are in fact possible.

It showed the neutral and attentive reader the thinking taboos of the nuclear "professionals".
I remember the <edit> user "Morbius" multiply stating apodictically that a recriticality would be impossible, implying that the corium is present in the form of one big, contiguous blob and basing his "calculations" on this assumption.
Three Mile Island proved that this is unlikely, but this belief appears to be still firm at most nuclear "professionals".

The user "Jim Hardy" pointed several times to the fact that he considers reflooding a reactor that has run dry as a very dangerous thing.
How true, as the control/absorber rods are going to melt away long before the fuel rods, and the water moderator would fill that void and create the risk of an uncontrolled chain reaction.
But nobody seemed to understand what "Jim Hardy" shyly pointed at and there was no discussion about this problem.

Anyway, can we really exclude the possibility that the "reordering" of the corium particles due to the changes of the cooling by Tepco could create critical configurations when they randomly form "lattices" of fuel material and moderating water?
The fact Tepco felt the need to use boron again proves that they are actually concerned.

I know that what I said is pure blasphemy to some nuclear "professionals".

But can their over-simplified models like MELCOR, MAAP etc really cope with the complex reality in an actual core-melt situation and its aftermath?

These models grossly failed already at analyzing the Three Mile Island event.
So, should we sheeple still believe and trust in models the nuclear industry propagates even though they have been proven to be inadequate since decades?

I would really appreciate if there would be a discussion that goes beyond some particular dogmata like the categoric stating that (re)critical configurations would be impossible, towards a discussion that tries to find out what configurations could possibility lead to re-criticality, and then to find out how to avoid such configurations occurring.
This would be way more constructive than that flaming I am used from some residents here.

 

[zapperzero]

I was an avid participant in that discussion.

Yes.
There was a large thread about the topic "what caused the explosion of reactor 3" or the like which got deleted by the moderators.
My impression is that this happened because this thread threatened to become blasphemic in the way that it could show that recriticality issues are in fact possible.

Afaik the thread got locked for cleanup, there was a rash of trolling and hyperventilating n00bs near the end.

It showed the neutral and attentive reader the thinking taboos of the nuclear "professionals".
I remember the <edit> user "Morbius" multiply stating apodictically that a recriticality would be impossible, implying that the corium is present in the form of one big, contiguous blob and basing his "calculations" on this assumption.
Three Mile Island proved that this is unlikely, but this belief appears to be still firm at most nuclear "professionals".

Morbius is a bomb-maker. He doesn't really do (or indeed grok) slow-neutron, moderated criticality stuff. His area of expertise is with reflectors and neutron initiators and high keff reactions in highly enriched material. Understandable bias.

The user "Jim Hardy" pointed several times to the fact that he considers reflooding a reactor that has run dry as a very dangerous thing.
How true, as the control/absorber rods are going to melt away long before the fuel rods, and the water moderator would fill that void and create the risk of an uncontrolled chain reaction.
But nobody seemed to understand what "Jim Hardy" shyly pointed at and there was no discussion about this problem.

I understood. Debris beds look a lot like working reactors - a roughly 50/50 mix of solids and water, in a steel can. Worse, the metal (structural steel, control blades etc) separates from the oxide (the contents of the fuel rods, basically) during the melt formation phase.

Anyway, can we really exclude the possibility that the "reordering" of the corium particles due to the changes of the cooling by Tepco could create critical configurations when they randomly form "lattices" of fuel material and moderating water?

Not in my opinion.

The fact Tepco felt the need to use boron again proves that they are actually concerned.

Yes, which is why I, just as yourself, find the insistence that it can't happen faintly ridiculous. It is not happening now, though, or there would be Xe and I and other fission products released again.

 

[elektrownik]

New temperature data for unit 2, it is interesting that CRD sensor value is increasing and that at some points it was close to second sensor value (before >200C readings):

 

[Shinjukusam]

They announced that three thermocouples were broken. Would that be one of them?

 

[zapperzero]

New temperature data for unit 2, it is interesting that CRD sensor value is increasing and that at some points it was close to second sensor value (before >200C readings):

It's maddening that they track up to a point. Makes it seem like something is happening and they're failing because of it. Simplest thing I can think of is corrosion due to water. But I don't know if failure due to corrosion is as fast as all that.

Another thing that's clouding the issue is that some of these are actually normalized readings - there has been some corrosion since day one and TEPCO said they are adjusting for this in their reporting - up to a point.

 

[elektrownik]

They announced that three thermocouples were broken. Would that be one of them?

The problem is that they are close to each other so this suggests that something is going on there
here is plot:

 

[jim hardy]

""Another thing that's clouding the issue is that some of these are actually normalized readings - there has been some corrosion since day one and TEPCO said they are adjusting for this in their reporting - up to a point.""

sigh - it is so hard to troubleshoot through somebody's interpretation of facts.
If only they'd post the raw millivolt readings..

do i recall those are iron-constantan thermocouples? Type J? I'm not at all sure.
In my plant we preferred chromel-constantan type E because the iron wire rusts but chromel doesn't. The tc's inside our reactor were chromel-alumel type K.

here's a link to some millivolt-temperature tables.
http://www.temperatures.com/tctables.html

 

[Rive]

My impression is that this happened because this thread threatened to become blasphemic in the way that it could show that recriticality issues are in fact possible.

IIRC what made that topic closed is flaming about recriticality in U3 fuel pool, without any scientific backup but with many emotions involved.

The possibility of recriticality is 'on the desk' here, from start as I recall: and as you can see, it's already discussed in depth by the nuclear scientific community (some links already here).

 

[zapperzero]

do i recall those are iron-constantan thermocouples? Type J? I'm not at all sure.
In my plant we preferred chromel-constantan type E because the iron wire rusts but chromel doesn't. The tc's inside our reactor were chromel-alumel type K.
[/url]

copper-constantan, according to ex-skf, who in turn quotes Matsumoto:

http://ex-skf.blogspot.com/2012/02/fukushima-i-nuke-plant-additional-info.html

 

[tsutsuji]

I translated two pages of Tepco's Report on “The Concept of Securing the Mid-Term Safety” (part 1, revision 2, December 2011) about unit 2's thermometers:

http://www.tepco.co.jp/cc/press/betu11_j/images/111207a.pdf pages 1-81 - 1-82 (87/131 - 88/131).

 

[tsutsuji]

http://www.tepco.co.jp/cc/press/betu11_j/images/111207a.pdf Figure 4-4 page 1-63 (69/131).

Va = (Ra/Rb) * (Vin-Vb) + Vin

 

[jim hardy]

Remarkable find tsujitsu !

THANK YOU!

copper constantan is a good choice because niether wire rusts.

And your find confirms they know about insulation damage and have localized it with TDR as one would expect of top notch folks.
Recall i said they have better technicians than me over there...
they know their plant like their own living room so know the likelihood of water where that damaged insulation is.

here's why i look for corroboration on those temperature measurements:

Galvanic Action
Some thermocouple insulating materials contain dyes that form an electrolyte in the presence of water. The electrolyte generates a galvanic voltage between the leads, which in turn, produces output signals hundreds of times greater than the net open circuit voltage. Thus, good installation practice calls for shielding the thermocouple wires from high humidity and all liquids to avoid such problems.

http://www.sensorland.com/HowPage017.html


Constantan is a copper-nickel alloy 55/45 i think. A us nickel is 75/25...
i just put a US nickel and a US penny in a coffee cup of salted water and read ~170 millivolts between them.

Thank you!

ps - edit:
And they've used circuit analysis to estimate thermocouple voltage in presence of interfering Vb , as from galvanic action...
nice.
now i need to repeat that penny-nickel experiment at various temperatures...

thanks, Tsujitsu

old jim

 

[Yamanote]

Thanks to you as well for explaining Jim!

 

[tsutsuji]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20120214/1350_ondokei.html The NISA instructed Tepco to write a report by 15 February, on such things as the cause of the high thermometer values and the way to measure temperatures by other methods.

http://www.47news.jp/47topics/e/225687.php On 15 February Junichi Matsumoto said "the report to NISA will be sent late in the night. I will explain its contents on 16 February".

 

[Atomfritz]

Thank you Tsutsuji for your finding.

I feel really amazed that a cheap two-wire thermocouple configuration was used and no four-wire-one with return wires.

With a four-wire thermocouple it would have been possible to narrow down the cause of the problem without having physical access. Possibilities include damage of the thermocouple element itself, wiring damage, shifting/decalibration etc.


Further reading about thermocouple basics for the interested reader "www.omega.com/temperature/z/pdf/z021-032.pdf" .

 

[mscharisma]

http://www.47news.jp/47topics/e/225687.php On 15 February Junichi Matsumoto said "the report to NISA will be sent late in the night. I will explain its contents on 16 February".

And then there was silence?

 

[Shinjukusam]

And then there was silence?

From NHK :

The operator of the crippled Fukushima Daiichi nuclear power plant has attributed abnormally high temperature readings at one of the facility's reactors to a malfunctioning thermometer.

Tokyo Electric Power Company, or TEPCO, reported the analysis of the problem at the Number 2 reactor to the government's nuclear safety agency on Thursday.

The thermometer at the reactor has been showing much higher readings than 2 others.

The utility said it's highly unlikely that temperatures could rise so high unless at least 60 percent of the melted nuclear fuel in the reactor were concentrated near the thermometer.

TEPCO confirmed signs of rising temperatures in experiments it conducted under unusually large electric resistance, as was found in the thermometer.

The thermometer serves as an indicator to assess whether the reactor can stay in a state of cold shutdown.

TEPCO says the thermometer will no longer be monitored. The firm says it will comprehensively examine data, including other thermometer readings and radiation levels in the reactor's containment vessel, to determine whether a state of cold shutdown is achieved.

The utility plans to reduce water injections into the reactor to a level at which such injections were done before the thermometer readings began rising, if the nuclear safety agency says that doing so is reasonable. Thursday, February 16, 2012 17:28 +0900 (JST)

 

[elektrownik]

And this sensor is also damaged ?

 

[zapperzero]

And this sensor is also damaged ?

Common cause failures have been a recurring theme in this accident. I wouldn't be too surprised.

 

[tsutsuji]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20120216/index.html Tepco is studying new thermometers for unit 2. Already 8 out of 41 or 20% of unit 2's thermometers are broken. As more might break down in the future, Tepco is studying how to install new thermometers. As one cannot easily approach the reactor, the study will take from one to two years.

http://www.tepco.co.jp/cc/press/betu12_j/images/120216a.pdf Report to NISA about unit 2's thermometer (48 pages, Japanese)

 

[jim hardy]

Common cause failures have been a recurring theme in this accident. I wouldn't be too surprised.

Tsujitsu's post 12383 mentions in the third thumbnail a "multiconductor cable" for some TC's around bellows seal.
Assuming multiconductor cable was also used around RPV bottom, it would not be surprising to find that common mode failure.

These TC's may not have been deemed important for post accident monitoring so not run in seismic grade conduit?
Perhaps a BWR person would know.

Looking at the formula they use for estimating thermocouple voltage,
again from Tsujitsu's thumbnails this time the one in post 12384,
Va = (Ra/Rb) * (Vin-Vb) + Vin
When everything is dry all three voltages Va Vb and Vin are same order of magnitude.
When the low resistance location gets wet Rb becomes a small denominator and Vb grows to a substantial multiple of Va.
a good math guy would run sensitivities...

That they did so well with it so long really impresses me
and makes me think that when they changed injection flow it washed down the area.
That's my two cents from 6536 miles away.
What do you folks make of those thermocouple symptoms?

old jim

 

[zapperzero]

makes me think that when they changed injection flow it washed down the area.
That's my two cents from 6536 miles away.
What do you folks make of those thermocouple symptoms?

old jim

My head hurts and I'm 8500 km away, give or take. What I can't understand is why the indicators first go way up, and only then way down. As far as I understand it, the actual measuring device is a voltmeter, right?

The way up part I can understand - the "electromotive force" as the Japanese so quaintly call it increases, because the water has salts in it, there's a (bigger) battery in there all of a sudden, so indicated temp rises.

But then, why the sudden crash to small but positive values? Does the wire get corroded through and through, so there is a huge increase in resistivity?

Then again, maybe I didn't understand something about that circuit correctly.

 

[jim hardy]

Wet thermocouples are not well behaved at all.

Their diagram is okay so far as it goes.

BUt think what they probably have in there:
thermocouple extension wire with insulation scraped or melted, adjacent structural material perhaps conduit wall or insulation?
so you have the possibility not only the 'electromotive force' from the copper-constantan galvanic cell,
but copper to conduit galvanic cell
constantan to conduit galvanic cell
either of above to insulation
any combination of above, and that's too many permutations for me.
and what's the conduit? In my plant the conduit was galvanized (zinc) and reactor vessel instlation was stainless steel

not trying to be difficult here, just explaining why i am not surprised at Tepco's difficulties with pulling a reading out of this mess.

Tsujitsu's link in post 12393
http://www.tepco.co.jp/cc/press/betu12_j/images/120216a.pdf

see page 21, right hand chart looks to me like a wet thermocouple ,
its reading swings between -300 and +400 and it looks like they drew a line through mean..
They showed more patience than i would have.

A wet TC will act like a small battery. You can charge it with your ohm-meter and watch voltage drift back down.
My heart goes out to those guys .
Whole world is watching and seldom is heard an encouraging word..

If any Daichi instrument techs are reading this - I say you have "True Grit."

Sorry i can't be more scientific about it.


old jim

 

[jim hardy]

and indeed ZZ it's a voltage measurement.

 

[zapperzero]

any combination of above, and that's too many permutations for me.

You and me both. Out the window goes my neat little mental model.

Tsujitsu's link in post 12393
http://www.tepco.co.jp/cc/press/betu12_j/images/120216a.pdf

see page 21, right hand chart looks to me like a wet thermocouple ,
its reading swings between -300 and +400 and it looks like they drew a line through mean..

A-ha. I hadn't seen that. It makes sense now. Thanks.

 

[tsutsuji]

Tsujitsu's link in post 12393
http://www.tepco.co.jp/cc/press/betu12_j/images/120216a.pdf

see page 21, right hand chart looks to me like a wet thermocouple ,
its reading swings between -300 and +400 and it looks like they drew a line through mean..

Page 21 is an experiment they made by connecting a variable resistor in series in one of the wires. When they set the resistor at 1.2 kΩ a small oscillation takes place and at 8 kΩ they find a large oscillation. The water's temperature is controlled by the reference thermometer (black curve) : 59°C for the 1.2 kΩ experiment, and 100°C for the 8 kΩ experiment.

They call these variations "hunching" (?) in English.

On pages 22 and 23 they make another experiment, by simulating cable damage, stripping the cable's insulator, leaving only one strand of copper on the copper wire, connecting a 40 kΩ resistor, and using salt water.

The resistance measurement results on unit 2's thermometers are in the table at the bottom of page 8 (copied also in the table page 15) :

30 september 2011 : 175.47 Ω (low insulation)
3 February 2012 : 244.25 Ω (low insulation)
13 February 2012 : from 500 to 523 Ω (rupture)
Average value of regular inspections : 303.37 Ω

They say that as a rule when the ratio of ( measured resistance / average regular inspection value ) is higher than 1.1, it means that the wire is in a rupture trend. It seems also that when this ratio is smaller than 1 they conclude "low insulation" in the table page 8.

At paragraph d) on page 18, which is the last sentence of the part of the report concerning the causes of the problem (following pages are attachments), they tell about their plans for the future : to verify the consistency between the experiments and the real phenomenon and to elucidate how the problem was generated.

The last part of the report, from page 36 to the end is about the different approaches that can be thought to perform alternative temperature measurements. They are listed in the table page 38. The schedule is on page 39.

 

[jim hardy]

Thanks Tsujitsu

I guess i should have kept quiet - all i could see was the pictures..
I hope i didnt mis-lead severely, thought that was plant data. I apologize.

Page 21 is an experiment they made by connecting a variable resistor in series in one of the wires.
When they set the resistor at 1.2 kΩ a small oscillation takes place and at 8 kΩ they find a large oscillation.

Unbalance in the leads can upset low level measurement systems.

They are becoming the world experts at thermocouple failure interpretation...

Thank you again for your hard work at finding and posting this information.



old jim

 

[rmattila]

Tsutsuji-san is truly doing a remarkable effort in helping many people to get an ever-improving picture of the events that took place and the current status of the plants. I have no doubt in my mind that some of this information will eventually lead into actual improvement of nuclear safety in many existing plants, as well as in those built in the future. With persistence and devotion, one man can really make a difference.

Thank you for not giving up!

 

[NUCENG]

Tsujitsu's post 12383 mentions in the third thumbnail a "multiconductor cable" for some TC's around bellows seal.
Assuming multiconductor cable was also used around RPV bottom, it would not be surprising to find that common mode failure.

These TC's may not have been deemed important for post accident monitoring so not run in seismic grade conduit?
Perhaps a BWR person would know.

Looking at the formula they use for estimating thermocouple voltage,
again from Tsujitsu's thumbnails this time the one in post 12384,
Va = (Ra/Rb) * (Vin-Vb) + Vin
When everything is dry all three voltages Va Vb and Vin are same order of magnitude.
When the low resistance location gets wet Rb becomes a small denominator and Vb grows to a substantial multiple of Va.
a good math guy would run sensitivities...

That they did so well with it so long really impresses me
and makes me think that when they changed injection flow it washed down the area.
That's my two cents from 6536 miles away.
What do you folks make of those thermocouple symptoms?

old jim

An additional consideration is the effect of radiation (beta and gamma) on the instrumentation cables insulation and cable jackets. Over time I would expect more of the thermocouple cables to have insulation degradation and develop problems. These instruments were not required to be qualified as BWR post-accident monitoring instruments in US plants under RG 1.97. That may be changing.

 

[tsutsuji]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20120217/index.html Tepco will reduce unit 2's injection rate by 4 tons/hour on 18 February.

http://www3.nhk.or.jp/news/genpatsu-fukushima/20120218/index.html The cause of the collapse of the Yonomori line tower No. 27 was underground water. The tower collapsed 2 minutes 30 seconds after the start of the earthquake. Underground water flows under the embankment. The ground became weaker as a consequence of shaking for a long time. The embankment was constructed during the 1965 - 1975 period to fill up a marsh, so there is much water. Tepco checked 530 towers concerning the Fukushima Daini and Kashiwazaki Kariwa plants, etc. but found no similar case.

http://www.tepco.co.jp/cc/press/betu12_j/images/120217c.pdf "causes of damage situation of power facilities inside and outside of Fukushima Daiichi Nuclear Power" (2nd release) (Japanese, 15 pages)

http://www.tepco.co.jp/cc/press/betu12_j/images/120217b.pdf "safety evaluation of transmission tower foundations regarding the offsite power supply to nuclear power stations and reprocessing plants" (Japanese, 17 pages)

 

[tsutsuji]

http://www.yomiuri.co.jp/e-japan/chiba/news/20120221-OYT8T00073.htm Robots Quince No.2 and No. 3　were dispatched from Chiba Institute of Technology to Fukushima Daiichi on 20 February. They are equipped with a cutter so that they can cut their cable to free themselves in case the cable is entangled. Quince No.2 has a camera arm long enough to look over the fuel pool fence, which Quince No.1 could not do.

 

[LabratSR]

Nuclear Regulatory Commission releases audio of Fukushima disaster

http://www.marketplace.org/topics/w...-commission-releases-audio-fukushima-disaster



About 3000 pages of transcripts

http://pbadupws.nrc.gov/docs/ML1205/ML120520264.html

Audio
http://youtu.be/ciRRsCIAy6A

 

[tsutsuji]

http://www.jiji.com/jc/c?g=soc_30&k=2012022300661 Thermometer "H2" on unit 2's RPV bottom rose by 11.5°C in 24 hours reaching 47.8°C at 11:00 AM on 23 February. However the other thermometer located at the same height rose by only 2°C during that time.

http://www.jiji.com/jc/c?g=soc_30&k=2012022300661 Unit 2 RPV bottom temperatures on 23 February, 17:00 :
"H1" (broken)
"H2" 49.5°C
"H3" 37.5°C

If "H2" alone continues to rise, there will be a suspicion that it is broken. The situation will be surveyed for the coming 2 or 3 days.

 

[Joffan]

This is after reducing the cooling water flow back down again, right? So some rise is expected, but not sudden shifts. There have been glitches in the past wher the readings have suddenly flipped to a new value, though, which looks like instrumentation rather than reality. http://atmc.jp/plant/temperature/?n=2

 

[r-j]

On page 232 of the transcripts they are talking about "the lifting of the flange on the drywell", at 65 pounds pressure. What does that mean?

The drywell head, the bolted flange, it might be lifting from pressure, causing the pressure in the containment to rise. Are they talking about the top of the reactor? Or the containment?

 

[tsutsuji]

http://www.47news.jp/47topics/e/225985.php Unit 2's thermometer that was rising, dropped by 4°C to around 45°C. However there is a 6°C difference with the other thermometer at the same height, which displays between 38 and 39°C. Either it is a consequence of the dispersion of the meltdown fuel or one of the two thermometers has a defect.

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120224_05-e.pdf "Temperature of the RPV Bottom at Unit 2, Fukushima Daiichi (1F) NPS"

 

[Joffan]

On page 232 of the transcripts they are talking about "the lifting of the flange on the drywell", at 65 pounds pressure. What does that mean?

The drywell head, the bolted flange, it might be lifting from pressure, causing the pressure in the containment to rise. Are they talking about the top of the reactor? Or the containment?

I think they're speculating that the containment lid lifted off its seals at that containment pressure (venting gas into the building), resealing when pressure dropped.

The operating pressure in the reactor vessel is routinely a great deal higher than 65psi.

 

[tsutsuji]

http://icanps.go.jp/eng/interim-report.html Full English translation of Cabinet Investigation Committee Interim Report (26 December 2011) [I had translated a few parts of the same document at https://www.physicsforums.com/showpost.php?p=3699408&postcount=12105 ]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20120224/2115_rousai.html The 60 year old worker who died in Fukushima Daiichi in May was recognised by the Labor Standards Inspection Office as a case of "workmen's accident", saying that "the cause is excessively heavy work under the unfree condition where one wears a protective clothing and a mask".

http://www3.nhk.or.jp/news/genpatsu-fukushima/20120224/1950_robo.html Tepco is studying the use of underwater robots in order to inspect the containment vessels. After opening a hole in the floor of the reactor building's first floor, the robot would be put into the accumulated water in the basement. The robot would be able to inspect the containment vessel's bottom and to perform repairs. As the start of the removal of fuel debris is scheduled within 10 years, the progress in the development of the necessary techniques is a key question.

http://www3.nhk.or.jp/news/genpatsu-fukushima/20120224/index.html The result of the NISA's onsite inspection from 6 February to 24 February is that the safety measures are "by and large suitable", although a few unsufficient responses were found, such as not writing down the necessary notifications when injection rates were changed at unit 2.

 

[Lambert]

NRC Operation Center Fukushima Day 1 Transcripts Audio Clips

sorry dbl post link already posted

 

[zapperzero]

I think they're speculating that the containment lid lifted off its seals at that containment pressure (venting gas into the building), resealing when pressure dropped.

See also this post by TCups, from March 19.
https://www.physicsforums.com/showpost.php?p=3197399&postcount=536

 

[zapperzero]

http://icanps.go.jp/eng/interim-report.html Full English translation of Cabinet Investigation Committee Interim Report (26 December 2011) [I had translated a few parts of the same document at https://www.physicsforums.com/showpost.php?p=3699408&postcount=12105 ]

This should clarify a lot about how and why the J-gov acted.

Here's one little story, in http://icanps.go.jp/eng/120224Honbun05Eng.pdf for example

In the meantime, on March 30, IAEA announced that the radiation dose level in
Iitate-mura had exceeded the IAEA criterion for evacuation, which corresponded to
100mSv for 7 days.The IAEA value, which exceeded its criteria was one data from one
point of total 9 points, was presented after converting the data measured by Japan to the
IAEA’s standard.
The inconsitency between Japan and IAEA happned even the same original data was
used. It might be caused by different criteria and method of judgement for evacuation.
IAEA criteria was based on a value of the ground surface density of radioactivity
(Bq/m2) which was derived by converting 100mSv for 7days, while Japanese criteria for evacuation is based on the radiation dose in the air. Moreover IAEA judged the necessity
of evacuation based on only one value above while Japan judged taking into account the
extended area of the radiation dose because only one one particular point data of higher
radiation dose in the air does not necessarily indicates a higher level of air dose in the
living space.
In addition, on April 1, the NSC determined that the air radiation dose rate was
decreasing day by day and that it might not be necessary to change the protective zone.
Subsequently, the NSC made an announcement to that effect.

(The IAEA criteria prescribes that the criterion for radioactive iodine 131 should be 10MBq/㎡. It was discovered
that the value that had been measured and converted at one particular point was an average value for the
concentration of radioactive iodine (Bq/kg) in the soil that had actually been measured between March 19 and 27,
that it was obtained by converting the surface concentration of radioactivity of radioactive iodine (Bq/㎡), and that
the value was approximately 20MBq/㎡)

 

[zapperzero]

also from http://icanps.go.jp/eng/120224Honbun05Eng.pdf

pp 319 and following

f. Establishment of specific spots recommended for evacuation

By April 22 when deliberate evacuation areas and emergency evacuation preparation
zones had been established, spots where annual cumulative radiation dose might exceed
20mSv assuming that the radiation dose levels continued afterwards had been found in
parts of Date-shi and Minami-soma-shi. However, the distribution of these spots was not
understood for an extended area, but for a limited area. Hence, the Government
Emergency Response Center did not designate those entire areas including these points as
deliberate evacuation zones. Instead, they decided to take a wait-and-see approach to
observe how radiation dose might decrease with time by monitoring them over time.
Subsequently, however, on June 3, MEXT estimated cumulative radiation dose and
found that there were spots where the estimated annual cumulative radiation dose for one
year after the nuclear accident might exceed 20mSv of a criteria for deliberate evacuation
zones, in parts of Date-shi and Minami-soma-shi, which are located outside the deliberate
evacuation zone.
In response to this fact, the NERHQ discussed the adoption of concrete measures for
locations where spots with high radiation dose were found in some areas and created a
guideline referred to as "Response to specific spots estimated to exceed an integral level of
exposure of 20mSv over a one-year period after the accident." The guideline stated that
spots where the estimated annual cumulative radiation dose over a one-year period after
the nuclear accident might exceed 20mSv should be designated as "specific spots
recommended for evacuation," and that the NERHQ should notify all residents living in
these spots and assist and support their evacuation. On June 16, the Government
Emergency Response Center asked the NSC for its advice on this guideline. That same
day, the NSC responded to this request replying to the effect that it had no objection to the
Government Emergency Response Center' ideas, although it might be necessary to
consider possible ways to solve this problem without conducting an evacuation, including
finding ways to decontaminate the areas that were only partially contaminated with high
concentration of radioactive materials.
Based on this advice, the NERHQ decided that the spots where the estimated annual
cumulative radiation dose over a one-year period might exceed 20mSv should be
designated as specific spots recommended for evacuation. That same day, Chief Cabinet
Secretary Edano released a statement to that effect.
It was decided that the NERLHQ should specify spots, per house, where
decontamination is not easy and are estimated to exceed 20mSv/year, through mutual
consultation between the Fukushima prefectural government and the cities, towns or
villages where those spots are located. Through mutual consultation with the respective
municipal governments, the NERLHQ designated parts of Date-shi on June 30 and
November 25, parts of Minami-soma-shi on July 21 and August 3, and parts of
Kawauchi-mura as specific spots recommended for evacuation.
Additionally, specific spots recommended for evacuation have not been issued with
evacuation orders pursuant to the provisions of Article 20, Paragraph 3 of the Act on
Special Measures Concerning Nuclear Emergency Preparedness. This policy is based on
the idea that specific spots recommended for evacuation are not dangerous enough to
instruct all residents to begin evacuation since radiation levels will be minimal if residents
leave the area, and that the government will provide information to alert them to the
possibility of radiation exposure and support residents if they need to be evacuated.

All formatting mine.