Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[pdObq]

Weird, the sea water is just pumped in as is?
Is there a reason that there is no prefilter to keep the eels and seaweed out other than cost?

Compromise beteen possible flow-rate and size of objects being filtered out?
Also, finer filters would probably have to be replaced more often?

EDIT: Jim was faster... Interesting that the screens are continuously cleaned. I guess that would be a solution for my second point. But probably that gets harder as the filters get finer.

PS: I probably wouldn't go fishing around the outlets...

 

[~kujala~]

The text is a critical (no, condemning) description of how TEPCO, 40 years ago, after realizing that the weak clay and sandstone in the upper 25m of the building site would have made it necessary to drive foundations as far down as the layer of relatively firm mudstone (泥岩層) below, removed the top portion of the building site, which made for easier access to cooling water and loading facilities for fuel easier.

Thanks for the source!
http://ziphilia.net/bbs.cgi/economy/1304793715/detailview#A_DEFAULT

Even though mudstone may be "relatively firm" it is still a different thing than bedrock.

First there is (or was) a 25 meter layer of clay and sandstone.
Below that is mudstone.
And below that is bedrock (-46 meters from the current ground level).
http://mdn.mainichi.jp/mdnnews/news/20110427p2g00m0dm091000c.html

As jlduh https://www.physicsforums.com/showpost.php?p=3304601&postcount=7428" TEPCO is lying again when they state in their web-page that "the plants are built on solid bedrock".
http://www.tepco.co.jp/en/challenge/energy/nuclear/plants-e.html

BTW: Does anybody want to translate the texts in this picture from Japanese to English?
http://gbleez.myhome.cx/uploader/src/up7713.jpg
I could make a bigger version of it, with English texts.

 

[Curium]

There is that stem flow from under the top cover of the reactor...

Yeah, seems possible that stuff ejected from the reactor could have gone into the pool when the building blew up, if that is what happened. Question is how much is "high levels of I-131", what does that mean quantitatively? Then extrapolate that amount back two months, equals about 8 half-lives, meaning 'quantity x' to the eighth power was present at the beginning.

The only source about all this 'MOX fuel piece found far away' thing is Gundersen himself. Or at least I could not find anything else, and please inform me if anybody could.

The original source is an NRC document about the Fukushima crisis

http://www.nytimes.com/2011/04/06/world/asia/06nuclear.html?_r=1"[A] confidential assessment prepared by the Nuclear Regulatory Commission... The document, which was obtained by The New York Times, provides a more detailed technical assessment than Japanese officials have provided ... The document also suggests that fragments or particles of nuclear fuel from spent fuel pools above the reactors were blown “up to one mile from the units,” and that pieces of highly radioactive material fell between two units and had to be “bulldozed over,” presumably to protect workers at the site. The ejection of nuclear material, which may have occurred during one of the earlier hydrogen explosions, may indicate more extensive damage to the extremely radioactive pools than previously disclosed. "

So, NY Times says they have this NRC document and quote it verbatim as "up to one mile from the units". Is this "confidential assessment" NRC document now publicly available somewhere? It was either voluntarily provided, or leaked, to NY Times 5 weeks ago, according to the article.

If the 2-kilometer ejection radius is true, in some sense it doesn't matter whether the explosion was a transient criticality or hydrogen or some other detonation. Still a big mess.

 

[artax]

this stuff is still on the TEPCO site too!... guess removing it isn't top of their list of priorities!

1. Measures to prevent unexpected events

* All designs provide margins of safety capable of withstanding even natural disasters.
* Strict quality control at every stage, from design to construction to operation.
* In addition to the elaborate regular inspections that take place every year, interlock and fail-safe systems are incorporated at every turn to prevent erroneous operations or actions.2. Measures to prevent the escalation of unexpected events

* Detection devices to detect abnormalities immediately
* Equipment that automatically and safely shuts the reactor down3. In the extremely unlikely event of an accident
[to prevent release of radioactive substances]

* Emergency Core Cooling System (ECCS)
* Airtight structure of the primary containment vessel and the reactor buildingAnti-Earthquake Measures
img01

Designed for the Largest Conceivable Earthquake
Before constructing a nuclear power plant, the site is carefully studied for previous earthquake records and geological features. This study establishes that there is no active fault under the site. Then, the building, the equipment, the piping, and other equipment are all designed to withstand the strongest possible earthquake in the area.

Hard-to-Shake Structure
Reactor buildings are built directly on solid bedrock after all soil has been removed. Furthermore, the reinforced concrete walls are far thicker than those used in other buildings. The building itself is a strong dice-like structure. Therefore, in the event of an earthquake, reactor buildings shake far less than an ordinary building.

Automatic Shutdown
Seismic detecting devices in the reactor building are designed to automatically shut the reactor down if they sense an earthquake of level 5 or greater.

 

[jlduh]

I repost here this film in two parts (already posted i think) about the construction of Daichi plant, unfortunately it is in japanese but there are some interesting images of the construction.

Could a japanese language member here view it and try to catch some useful infos from the commentary (don't know if they say something about the preparation on the ground...)?



http://www.youtube.com/watch?v=cTshYXmN1AY&feature=related

There is a part concerning construction of the building starting at around 9'30 (part I) and there is a nice helicopter view at 10'42 over the all plant, showing on the left the concrete foundation of what will become N°2 reactor and turbine buildings besides the N°1.

I attached a capture of the screen at 10'46 (see below)

You can get a bigger image size clicking here:
http://www.netimago.com/image_200707.html

 

[StrangeBeauty]

Tepco released many important data: http://www.tepco.co.jp/nu/fukushima-np/

Thank you elektrownik. Out of those docs, imo here is the biggest problem atm:
http://www.tepco.co.jp/nu/fukushima-np/f1/images/temp_data_3u-j.pdf

Barring all these temp readings being wrong, core material must still be inside the #3 RPV doing something.

 

[zapperzero]

They mention that the leak was detected by noticing a rise in saline concentration in the re-condensed water. Then they switched to a different cooling system. No explanation of where the 400 ton estimate came from.

So, they detected ions that shouldn't have been there, measured concentration, did a quick napkin-based calculation and stated "hmm, we must have taken on an additional 400 tons of seawater for the concentration to be what we found".

They are assuming the best-case scenario. Stuff is coming in, stuff may have been getting out as well.

Where is the coolant mass calculation? They should know to the liter, or at least to the ton, what they put in. It should NOT have been going anywhere. Somewhere, there are volume measurements (for water), pressure and temp readings (for steam plenums, all of which are of known volume, RPV included as the plant is in "cold shutdown" so the water is barely boiling).

Also, the different cooling system must be one of those available for emergency use. The primary cooling has been shut down. The plant is thus in the same situation as Fukushima Dai-ni, post-tsunami, only this time they have chlorine in the RPV. Dai-ni was serious enough to rate a 10 km exclusion zone.

 

[bytepirate]

Tepco released many important data: http://www.tepco.co.jp/nu/fukushima-np/

and many not so interesting as well ;-)

what is new to me, are the documents, that seem to contain *all* data (or at least much more, than i have seen before), that they have for the early days:
http://www.tepco.co.jp/nu/fukushima-np/f1/images/syusei_level_pr_data_1u.pdf
http://www.tepco.co.jp/nu/fukushima-np/f1/images/syusei_level_pr_data_2u.pdf
http://www.tepco.co.jp/nu/fukushima-np/f1/images/syusei_level_pr_data_3u.pdf

have i missed them before, or have they been published only recently?

 

[pdObq]

I repost here this film in two parts (already posted i think) about the construction of Daichi plant, unfortunately it is in japanese but there are some interesting images of the construction.

Could a japanese language member here view it and try to catch some useful infos from the commentary (don't know if they say something about the preparation on the ground...)?



http://www.youtube.com/watch?v=cTshYXmN1AY&feature=related

These have been posted here or at least on houseoffoust a few weeks back. A version with English subtitles has been around for quite a while too (over a month), see the video responses, here for part 1, .

 

[jlduh]

These have been posted here or at least on houseoffoust a few weeks back. A version with English subtitles has been around for quite a while too (over a month), see the video responses, here for part 1, .

Great! Thanks, i didn't see the english subtitled one!

 

[Curium]

[PLAIN]http://galeon.com/saboten7/fukushima3.jpg

Some massive solid debris reaches an apex of more than 200 meters, then falls back to earth. Those parts end up fairly close to the building site.

Something found in the 1000 - 2000 meter range from the building would have to be on a low initial trajectory, or thrown higher than the "mushroom cloud" and maybe carried by wind

 

[MadderDoc]

Thanks for finding those. They don't look conclusive to me whether the pipe was damaged or not. I'll keep looking.

You can arrive at a stronger conclusion by looking at another and later photo which shows where the part of the pipe that came off the wall ended up on the ground. In that way you will have two corroborating pieces of information from this photo you are looking at:

a) the pipe does appear to broken (although some would not like to say so conclusively)
b) the part of the pipe that came off does appear to be lying under it, in the same spot, and angled similarly to how we find that part on later photos.

Added together, this would seem to me sufficient evidence to force us to reject the hypothesis that the pipe remained intact after the unit 3 explosion.

Edit: By 'later photo' I mean any photo showing this area and _taken in the period March 14 through March 20._
We know from the photos that Tepco in order to make access for spraying to the pool had moved the part of the pipe that fell to the ground by March 24th, but had not done so on March 20th.

 

[Rive]

Yeah, seems possible that stuff ejected from the reactor could have gone into the pool when the building blew up, if that is what happened. Question is how much is "high levels of I-131", what does that mean quantitatively? Then extrapolate that amount back two months, equals about 8 half-lives, meaning 'quantity x' to the eighth power was present at the beginning.

With the steam flowing continuously (nighttime pictures) we have a possibly continuous, unpredictable source of I-131 with unknown volume. So with only one sample (I know about only one sample) any deep 'analysis' is just guessing.

The original source is an NRC document about the Fukushima crisis

It'll be this one I think: http://cryptome.org/0003/daiichi-assess.pdf

All it has is:

Fuel pool is heating up but is adequately cooled, and fuel may have been ejected from the pool (based on information from TEPCO of neutron sources found up to 1 mile from the units, and very high dose material had to be bulldozed over between Unit 3 and 4. It is also possible the material could have come from Unit 4.)

What's only a 'may have been'.

IMHO it's unlikely that fuel ejected, and found only a mile away and right near the reactor, and nowhere else around the site (it's quite easy to notice ejected fuel by the alarming dosimeters :-) ). So that early 'may have been' actually is a 'not likely' and should not be taken as a fact and used as backup for wild speculations.

PS.: of course: IMO.

 

[Azby]

Good point. I live near Fukushima and I'm wondering if there is any way I can test for radiation on my own. My spouse and I are particularly concerned about the health of our young children.

We want to know if we can test food, water, ground surfaces and background radiation on our own, or if we can only trust the government to keep us safe.

I've heard of a farming community in Nasu, Tochigi Prefecture, that pooled funds to buy 50 geiger counters, and made an agreement with a local lab to use scintillation counters and other more expensive equipment to measure produce, milk, etc.. By all means buy yourself a geiger counter, but please try to organize your community to do the same, and collaborate in order to produce more reliable and meaningful data.

<http://www.safecast.org/> has a program to put geiger counters in the hand of communites that need them.

 

[SteveElbows]

and many not so interesting as well ;-)

what is new to me, are the documents, that seem to contain *all* data (or at least much more, than i have seen before), that they have for the early days:
http://www.tepco.co.jp/nu/fukushima-np/f1/images/syusei_level_pr_data_1u.pdf
http://www.tepco.co.jp/nu/fukushima-np/f1/images/syusei_level_pr_data_2u.pdf
http://www.tepco.co.jp/nu/fukushima-np/f1/images/syusei_level_pr_data_3u.pdf

have i missed them before, or have they been published only recently?

The original uncorrected ones were published at some point in the past because a user of this forum managed to find cached copies on the internet and posted them here. I was using these originals as the basis for several posts I made yesterday in response to people questioning the timing of events in light of the reactor 1 meltdown news.

The republished data certainly contains a lot more data points, though I have not had time to notice whether there are any really significant new bits of data yet.

 

[mscharisma]

...
The original source is an NRC document about the Fukushima crisis

http://www.nytimes.com/2011/04/06/world/asia/06nuclear.html?_r=1

"[A] confidential assessment prepared by the Nuclear Regulatory Commission... The document, which was obtained by The New York Times, provides a more detailed technical assessment than Japanese officials have provided ... The document also suggests that fragments or particles of nuclear fuel from spent fuel pools above the reactors were blown “up to one mile from the units,” and that pieces of highly radioactive material fell between two units and had to be “bulldozed over,” presumably to protect workers at the site. The ejection of nuclear material, which may have occurred during one of the earlier hydrogen explosions, may indicate more extensive damage to the extremely radioactive pools than previously disclosed. "

So, NY Times says they have this NRC document and quote it verbatim as "up to one mile from the units". Is this "confidential assessment" NRC document now publicly available somewhere? It was either voluntarily provided, or leaked, to NY Times 5 weeks ago, according to the article.
...

As previously pointed out, the word "may" is a key word throughout here as well as in the original NRC document, indicating possibility, but not certainty. The document is available here:

http://www.fairewinds.com/content/nrc-report-official-use-only-fukushima-assessment-march-26th-2011

 

[SteveElbows]

The republished data certainly contains a lot more data points, though I have not had time to notice whether there are any really significant new bits of data yet.

OK first stuff of significant I notice is for reactor 2. New version of data contains tons more information about water levels and reactor pressure during a very crucial period of time between 13:00 and 23:11 on the 14th. Given what was happening during that time period (fuel uncovered) its tempting to say that they had a reason to hide this data before.

 

[Astronuc]

Thanks for the source!
http://ziphilia.net/bbs.cgi/economy/1304793715/detailview#A_DEFAULT

Even though mudstone may be "relatively firm" it is still a different thing than bedrock.

First there is (or was) a 25 meter layer of clay and sandstone.
Below that is mudstone.
And below that is bedrock (-46 meters from the current ground level).
http://mdn.mainichi.jp/mdnnews/news/20110427p2g00m0dm091000c.html

As jlduh https://www.physicsforums.com/showpost.php?p=3304601&postcount=7428" TEPCO is lying again when they state in their web-page that "the plants are built on solid bedrock".
http://www.tepco.co.jp/en/challenge/energy/nuclear/plants-e.html

BTW: Does anybody want to translate the texts in this picture from Japanese to English?
http://gbleez.myhome.cx/uploader/src/up7713.jpg
I could make a bigger version of it, with English texts.

I'm guessing that 'mud-stone' rock is a reference to sedimentary or metamorphic rock as opposed to clay or sandstone. Generally, large structures like containment buildings and dams are built on or into 'bedrock' which hopefully is geologically stable, and doesn't creep. Soft soils amplify the effects of seismic waves.

For general interest - http://www.world-nuclear-news.org/RS-Fukushima_fuel_melt_confirmed-1605115.html

I disagree with the term 'confirmed'. They have not confirmed, but rather strongly expect that the core of unit 1 melted. That is not necessarily the case, unless they had no cooling water or steam whatsoever in the core, i.e., within the core barrel. Outside the core barrel is the annular region around between the core barrel and RPV shell. That is where coolant normally goes from the feedwater system, and that is then pumped into the bottom plenun and up into/through the core. In the jet pump design, the pump risers would preclude water from the base of the annulus from getting to the core. If they were able to pump water into the bottom plenum, it's not clear why they couldn't get it into the core - unless some of the control rod drive housings had broken or the seals had given way. Then it would be possible that they pumped water into the RPV, but it leaked out the bottom without entering the core.

We really won't know what happened until they get a camera inside.

Bear in mind that the core did have water at some point. Without cooling, stagnant water would have boiled, and that water/steam should have been 'saturated'. When the water was gone, then the steam can become superheated. That steam would have reacted/corroded the cladding, and possible the channels and control rods, which would have produced hydrogen, which ostensibly escaped through breaks or leaks into containment. From the primary containment, the hydrogen is expected to have leaked into the secondary containment structure where it ignited/detonated. It's a similar scenario to Unit 3 and 2, but ostensibly there was more success in getting cooling water into the reactors of those units.

Melting of the core is not necessary for significant release of fission products, particuarly the gases (Xe, Kr) and volatiles (I, Cs, perhaps Te). The corrosion and breaching of the Zircaloy cladding is all that is necessary, and there was probably a lot of oxidation of the Zircaloy.

 

[tsutsuji]

An Asahi article mentions the following :

The collapse of a transmission tower at Fukushima Daiichi NPP is seen by Tepco as being a consequence of a mudslide caused by the March 11th earthquake.

Some readings are missing in the seismometer data of Fukushima Daiichi and Daini. NISA is instructing Electric Power companies to review their seismometers.

The earthquake design basis which had been set in 2006 was overridden at Fukushima Daiichi units 2,3 and 5. Slightly so too at unit 1 during some phases of the quake.

A seismometer located 200 m underground recorded quake intensities below the design basis.

http://www.asahi.com/national/update/0516/TKY201105160568.html

Reuters deems newsworthy to say:

The magnitude 9 earthquake that struck a Japanese nuclear plant in March hit with almost 30 percent more intensity than it had been designed to withstand, raising the possibility that key systems were compromised even before a massive tsunami hit.

http://uk.reuters.com/article/2011/05/16/uk-japan-nuclear-idUKTRE74F17K20110516

 

[jlduh]

You can arrive at a stronger conclusion by looking at another and later photo which shows where the part of the pipe that came off the wall ended up on the ground. In that way you will have two corroborating pieces of information from this photo you are looking at:

a) the pipe does appear to broken (although some would not like to say so conclusively)
b) the part of the pipe that came off does appear to be lying under it, in the same spot, and angled similarly to how we find that part on later photos.

Added together, this would seem to me sufficient evidence to force us to reject the hypothesis that the pipe remained intact after the unit 3 explosion.

Edit: By 'later photo' I mean any photo showing this area and _taken in the period March 14 through March 20._
We know from the photos that Tepco in order to make access for spraying to the pool had moved the part of the pipe that fell to the ground by March 24th, but had not done so on March 20th.

I post below one of these pictures that show the broken venting pipe from N°3: we can very well see in the alignment at the right of the building:

- the remaining part going to the stack (which is towards the right, outside of the picture), - - the fallen part laying on the ground,
- and remaining pipe coming from the building at the bach (east side)

http://www.netimago.com/image_200730.html

To me, looking at several pictures, this pipe has been broken by the n°3 explosion (probably falling wall).

 

[razzz]

Once the foundations are in place the site would be backfilled around the foundations to reach current levels, In the US there are extensive provisions for controlled runoff and draining to ensure potential released of ground water are not contaminated or if contamination exists, that it is monitored and reported. Would that help stabilize the mudstone so it wouldn't erode?

Keep it dry via de-watering. It's not the their term for bedrock that is the problem or even if construction techniques can overcome the shortcomings of poor soil conditions, it's the area between sea level and to the bottom of the evacuation where underground water can travel. To control the flow of underground water from traveling inland, you pump water out of a well to keep underground water traveling to that point of the well(s) intake level and not allowing water to pool underground and/or flow inland. The situation is twofold now. Keep the ground from saturating and keep the contaminated (underground) water from migrating inland from the plant site.

 

[tsutsuji]

BTW: Does anybody want to translate the texts in this picture from Japanese to English?
http://gbleez.myhome.cx/uploader/src/up7713.jpg
I could make a bigger version of it, with English texts.

Here you are :

 

[SteveElbows]

OK first stuff of significant I notice is for reactor 2. New version of data contains tons more information about water levels and reactor pressure during a very crucial period of time between 13:00 and 23:11 on the 14th. Given what was happening during that time period (fuel uncovered) its tempting to say that they had a reason to hide this data before.

OK I didnt find any further differences between previously available data and this new release that struck me as really significant.

However, as many people may never have seen the data before, there are probably some noteworthy things in there that may have room left for further discussion.

I do wonder if there has been a large release of data officially at this time because of the leak to the newspaper, and this is TEPCO responding by publishing the material themselves.

For example the following Japanese page appears to have some very large pdfs which contain the raw data from the period, collected in a bewildering array of forms and those little measurement graphs that get plotted in realtime by clunky old equipment at the plant:

http://www.tepco.co.jp/nu/fukushima-np/index10-j.html

 

[Uagrepus]

To me, looking at several pictures, this pipe has been broken by the n°3 explosion (probably falling wall).

... and the mysterious green-scaffold-builder were there ...

 

[elektrownik]

Here are 60 pages of data plots: http://www.tepco.co.jp/nu/fukushima-np/plant-data/f1_8_Parameter_graph.pdf

 

[MadderDoc]

Here are 60 pages of data plots: http://www.tepco.co.jp/nu/fukushima-np/plant-data/f1_8_Parameter_graph.pdf

This, elektrownik, is a most interesting document. It includes far more datapoints than I have seen before, including during the most interesting moments. I've previously estimated the pressure drop within the containment during the explosion of unit 3 to be >=0.1 MPa. Based on this document, the estimate of DW pressure drop must be revised to >=0.4MPa.

It is also news to me from this document, that the RPV during the period of the 'black smoke event' on March 21st briefly peaked out at >12MPa, before it dropped back abruptly and went down to to atmospheric. My,my.

 

[jlduh]

... and the mysterious green-scaffold-builder were there ...

Where did you get this picture? When was it taken? Are you sure it was there (the scaffold builder) when the explosion occurred? I don't see it on the pictures...

Probably a stupid remark, and I don't know if this has been discussed already but i find something strange in the way this vent has been destroyed: the remaining part of the tubing at the west side is in perfect shape, including the very end of it, where the part that fell was supposed to be connected... That's quite bizarre, because if the part that fell was crushed by the falling wall, one could imagine that the remaining end would have so damages at the jonction. Here it's perfect! The comparision with the other side is very self explanatory of what I mean...

Something else is strange: from the top view, we have the impression that the fallen part is in fact TOO SHORT to cover the whole initial distance, like if one part of the tubing was missing?

http://www.netimago.com/image_200771.html

I mention this because it looks strange and also because of the scaffold builder you mention, with an idea in mind: could it be possible that they were doing some maintenance on the vent at this place, so the pipe was disconnected at this point when explosion happened?

Of interest, on later pictures, we can see that the curved tubing that was intact after the explosion in now... bent towards the ground!

See it:
http://www.netimago.com/image_200769.html

Do you think they bent it purposely in between? Why? For the crane to go maybe?

 

[StrangeBeauty]

...To me, looking at several pictures, this pipe has been broken by the n°3 explosion (probably falling wall).

Agreed. That pipe was definitely broken after the #3 explosion. Also it can be seen on this page (about half way down):
http://www.houseoffoust.com/fukushima/april15.html

However, I thought Tepco was claiming that the hydrogen went from #3 to #4 via a different piping system? Here's the quote:

According to Tepco, hyrogen produced in the overheating of the reactor core at unit 3 flowed through a gas-treatment line and entered unit No. 4 because of a breakdown of valves.

Where is this gas-treatment line?

 

[I_P]

This, elektrownik, is a most interesting document. It includes far more datapoints than I have seen before, including during the most interesting moments. I've previously estimated the pressure drop within the containment during the explosion of unit 3 to be >=0.1 MPa. Based on this document, the estimate of DW pressure drop must be revised to >=0.4MPa.

It is also news to me from this document, that the RPV during the period of the 'black smoke event' on March 21st briefly peaked out at >12MPa, before it dropped back abruptly and went down to to atmospheric. My,my.

The 21st is when the radiation monitors in Ibaraki showed a large abrupt spike in radiation - similar in character and magnitude to the one on the 15th. Measured levels have been steadily declining since the 21st with no other major peaks - just very minor increases during periods of rain showers or disturbed weather.

 

[SteveElbows]

Do you think they bent it purposely in between? Why? For the crane to go maybe?

Either that or perhaps it was damaged when the control room concrete from the south west corner of the building fell (we don't know when this fell, or even if it was deliberately removed, but at some point it goes from being still attached to the building to being on the ground.)

 

[SteveElbows]

It is also news to me from this document, that the RPV during the period of the 'black smoke event' on March 21st briefly peaked out at >12MPa, before it dropped back abruptly and went down to to atmospheric. My,my.

Yes I think that's the main event that stands out when looking at data from later than the initial days of the crisis.

You are probably better off looking at the version of the documents that contains the data in tabular form, which for reactor 3 is this one:

http://www.tepco.co.jp/nu/fukushima-np/f1/images/level_pr_data_3u-j.pdf

So it didnt quite get above 12Mpa.

I think it would also be most useful to look at the temperature data for the same time period:

http://www.tepco.co.jp/nu/fukushima-np/f1/images/temp_data_3u-j.pdf

So yes, there is a match, with some very high temperatures at the same time, 01:25 on the 21st.

I had previously keep a somewhat open mind about the black smoke events that happened that week at reactor 3, simply because it was also a week where they were switching various things back on after restoring power. So I thought maybe some piece of equipment caught fire. But the temperature & pressure data does make it seem more likely that something more dramatic was happening at that time.

 

[MadderDoc]

<..>To me, looking at several pictures, this pipe has been broken by the n°3 explosion (probably falling wall).

I agree, we can leave the theory that the exhaust stack pipes between unit 3 and 4 after the explosion in unit 3 would have been able to lead hydrogen from unit 3 to unit 4.

If I remember correctly Tepco's original idea was that the leak of hydrogen to unit 4 went through the 'gas treatment lines'. I suggest what could be meant there is the large pipe system running along the turbine buildings, leading to a minor building at the Centralized Radiation Waste Treatment Facility, and from there to the big south exhaust stack SW of unit 4.

 

[jlduh]

Yes I think that's the main event that stands out when looking at data from later than the initial days of the crisis.

You are probably better off looking at the version of the documents that contains the data in tabular form, which for reactor 3 is this one:

http://www.tepco.co.jp/nu/fukushima-np/f1/images/level_pr_data_3u-j.pdf

So it didnt quite get above 12Mpa.

I think it would also be most useful to look at the temperature data for the same time period:

http://www.tepco.co.jp/nu/fukushima-np/f1/images/temp_data_3u-j.pdf

So yes, there is a match, with some very high temperatures at the same time, 01:25 on the 21st.

I had previously keep a somewhat open mind about the black smoke events that happened that week at reactor 3, simply because it was also a week where they were switching various things back on after restoring power. So I thought maybe some piece of equipment caught fire. But the temperature & pressure data does make it seem more likely that something more dramatic was happening at that time.

One possibility IHMO being that the RPV got eaten by the corium, maybe helped with some local criticality... Your opinion?

By the way, the BLACK SMOKE was reported on March 23, not 21 if I'm not wrong...

But of course, black smoke can be the visual effect seen from outside of an event started earlier inside the RPV.

 

[MadderDoc]

Yes I think that's the main event that stands out when looking at data from later than the initial days of the crisis.

You are probably better off looking at the version of the documents that contains the data in tabular form, which for reactor 3 is this one:

http://www.tepco.co.jp/nu/fukushima-np/f1/images/level_pr_data_3u-j.pdfSo it didnt quite get above 12Mpa.

When I say pressure, you can assume that I am talking absolute pressure, Tepcos data are gauge. Thank you so much for pointing me to the tabular data, that is most convenient (drool).

I had previously keep a somewhat open mind about the black smoke events that happened that week at reactor 3, simply because it was also a week where they were switching various things back on after restoring power. So I thought maybe some piece of equipment caught fire. But the temperature & pressure data does make it seem more likely that something more dramatic was happening at that time.

Indeed, I had it also parked there, that since data appeared to say nothing particular happened -- reactor-wise -- then probably nothing of that sort happened. It could have been some plastic caught fire, lubricant, whatever giving off yucky smoke, but nothing really to see as a main development. Oh well.

 

[tsutsuji]

As Reuters puts it :

In another instance of an apparent error in judgement, Tepco said that a worker may have shut down a cooling system known as the isolation condenser shortly after the earthquake when he saw that the No. 1 reactor was losing temperature quicker than the utility's guidelines allowed.
http://uk.reuters.com/article/2011/05/16/uk-japan-nuclear-idUKTRE74F17K20110516

But http://www.chunichi.co.jp/s/article/2011051790014812.html says that while Tepco is emphasizing that the shutdown of the isolation condenser by a worker, in accordance with the manual which instructs to do so when reactor temperature falls by more than 55°C per hour, is one possibility, the other possibility is that the isolation condenser was damaged by the earthquake before the tsunami struck. Tepco says that the second possibility can't be ruled out.