Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[SteveElbows]

A document was given to the press in June, which included estimates of radioactive releases in the 1st 100 hours of the crisis.

On page 13 a table is given with the following header:

解析で対象とした期間での大気中への放射性物質の放出量の試算値

"Estimated amount of radioactive material released into the atmosphere over the time period covered by the analysis" {google translate}

It shows 1.2254x10^12 becquerels of Plutonium 238, 239, 240, 241 combined, 99% of which was Pu-241

This document is available in English, and has come up before since it is one of the main publications with detail of both TEPCO and government agency estimates of reactor 2 & 3 core damage and associated consequences.

http://www.nisa.meti.go.jp/english/press/2011/06/en20110615-5.pdf

The table you refer to has long been of interest to me because I've always been interested in the reasons why this sort of data seems to show reactor 2 being responsible for a large chunk of the total. As part of this I have sometimes wondered whether such estimates included water, considering reactor 2 building survived and this reactors highly-radioactive water made headlines when first discovered. But most March release estimate data seems to involve methods that use data such as radiation levels at site boundaries, and levels detected on land at a variety of locations, which tends to suggest to me that at last some of the numbers we see are for 'air only'. But other grand totals, such as the ones I've just been going on about in my previous post, also add on water estimates. Its been quite hard for me to form highly detailed conclusions about some estimates though, sometimes down to translation issues or sparse/ambiguous use of language, but also because stuff such as MELCOR analysis of what may have happened is involved, and I don't actually know the full detail of how this model works.

I doubt it contains the full answers to the questions you have asked, but for some additional talk about this kind of release estimate data, you may also find the thread about Unit 2 of some use, especially since it is not very long so its not hard to pick out the posts that discuss this sort of data:

https://www.physicsforums.com/showthread.php?t=507252

 

[tonio]

Ive also often wondered exactly what I am looking at on this shot from March 12th at 3pm. Is there any find of flammable gas flaring feature built into the stacks?

I understand what you mean. See the added details of photos. In the left photo, a steam plume seems to come from the top of the stack. In the other photo (from the quoted message), a steam-like plume emerges from a lower level and changes from whitish to faint black (soot?).

 

[tonio]

forgot the photo.

 

[LabratSR]

At the bottom of page 10 they state they covered the Unit 4 SFP on Oct 14

http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/111017e3.pdf

 

[Astronuc]

. . . . Its been quite hard for me to form highly detailed conclusions about some estimates though, sometimes down to translation issues or sparse/ambiguous use of language, but also because stuff such as MELCOR analysis of what may have happened is involved, and I don't actually know the full detail of how this model works.

I doubt it contains the full answers to the questions you have asked, but for some additional talk about this kind of release estimate data, you may also find the thread about Unit 2 of some use, especially since it is not very long so its not hard to pick out the posts that discuss this sort of data

An analysis is only as good as the input. If one assumes no cooling whatsoever (i.e., purely adiabatic condition), then certainly core melting is only a matter of time. Only by knowing the exact cooling history can a reasonable analysis be performed.

Otherwise, one has to wait to see what the core looks like, then perform parametric studies with cooling time histories in an attempt to match predictions with results.

This might be of help - MELCOR Application of Selected Design Basis Accident Analyses.
Accession Number: ML111570055
Date Released: Thursday, June 9, 2011

http://pbadupws.nrc.gov/docs/ML1115/ML111570055.html - Enclosure 1 & 2 contain the details.

 

[westfield]

I understand what you mean. See the added details of photos. In the left photo, a steam plume seems to come from the top of the stack. In the other photo (from the quoted message), a steam-like plume emerges from a lower level and changes from whitish to faint black (soot?).

I have no idea about the colour of the emissions but it's two different stacks, one almost obscured by the other.

There is a stack each for Units 1 & 2, 3 & 4, 5 & 6, and the radwaste treatment building stack.

4 stacks all up at F1.

edit : At a glance the "lower down" emissions may be from the Units 1 & 2 shared stack, with units 3 & 4 stack obscuring it.

The documents intimate that the majority of the emergency venting from Unit #2 came from the drywell hardened vent which may or may not have something to do with the colour of the plume. ( I.e. completely unfiltered from the drywell hardened vent vs somewhat scrubbed if done via wetwell\S\C direct venting)

 

[westfield]

Tsutsuji, can you please check if there was any released information about cleaning up U4 top levels, or covering U4 SFP? <snip>

It would be interesting to see more related photos or vids about this.


<snip> .

Yes it would be interesting to see more of the work at Units 3 & 4. It would be even better if they moved the webcam over there now that Unit 1 RB is fully "tented". But I would understand if we don't get to see much. I'm not sure TEPCO would want to show us exactly how they have been tackling the debris cleanup near units 3 & 4. Debris which was mapped as significantly contaminated to highly contaminated in spots.

They have been extremely busy around units 3 & 4.

Actions like ripping open the large ducting between Units 2 & 3 leading to the common radwaste treatment building in order to get crane access and sorting and crushing concrete and steel as if it's being prepared for recycling on a conventional demolition site like here right next to RB 3 makes me wonder if TEPCO are doing a "rush job" on the debris without what would be considered "best practice", understandable I guess if that's the case, but not something good for the public's eyes.

http://i1185.photobucket.com/albums/z360/fukuwest/misc/demolitionexample01f1.jpg

http://i1185.photobucket.com/albums/z360/fukuwest/misc/110825_1_crop_removedpiping.jpg

Does anyone here work on Superfund sites or similar that may care to comment on the cleanup methods being deployed at F1?

 

[MadderDoc]

<..>At a glance the "lower down" emissions may be from the Units 1 & 2 shared stack, with units 3 & 4 stack obscuring it.

Indeed the plume seen in the webcam from 15:00 on March 12th is most likely from the 1+2 shared stack. This emission event appears to have been captured also in a video taken from a helicopter overfly in the afternoon on March 12th, here's a frame from that video.

Also, Tepco has reported that on March 12th at 14:00 a makeshift air compressor was installed such that the unit 1 AO valve for S/C venting could now be operated, and an hour later, that emission of radioactivity from the S/C vent was ongoing. Pressure data too indicate that the S/C and D/W pressure decreased over that period, from about 0.75 MPa to 0.5 MPa.

 

[Rive]

...Actions like ripping open the large ducting between Units 2 & 3 leading to the common radwaste treatment building in order to get crane access and sorting and crushing concrete and steel as if it's being prepared for recycling on a conventional demolition site like here right next to RB 3 makes me wonder if TEPCO are doing a "rush job" on the debris without what would be considered "best practice", understandable I guess if that's the case, but not something good for the public's eyes.

The 'rush job' is correct, but while they are just collecting the debris and deploy it in an on-site storage area, IMHO it's OK. I think they will try to cover U3 and U4 before the end of the year, and to remove all that debris from the top levels of the units will take some time.

I don't think that any of this part is 'non public'. In fact, it's a kind of victory. I can't understand why is it not presented with more publicity.

http://www.tepco.co.jp/cc/press/betu11_j/images/111017d.pdf is about the safety of the four spent fuel pools, and some pages are about unit 4, but it does not seem to address the covering issues of unit 4 or unit 3. I have not heard about the covering of unit 4 SFP since it was last discussed on https://www.physicsforums.com/showpost.php?p=3528287&postcount=11378 and https://www.physicsforums.com/showpost.php?p=3526548&postcount=11372 (september 27). The pictures of debris removal on the top of unit 3 and unit 4, including the "curing for spent fuel pool, oct 14" picture shown in http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/111017e6.pdf are new to me.

Very thanks. So it's just another 'we just did it, you don't have to know much about it' thing :(

---------------------------------------------------

What 'soundness' could be originally?
http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111019_01-e.pdf

 

[SteveElbows]

The documents intimate that the majority of the emergency venting from Unit #2 came from the drywell hardened vent which may or may not have something to do with the colour of the plume. ( I.e. completely unfiltered from the drywell hardened vent vs somewhat scrubbed if done via wetwell\S\C direct venting)

Given that reactor 1 building suffered an explosion about half an hour after the webcam image was taken, I was tentatively working on the basis that it was reactor 1 venting seen in the image. And so I was wondering if hydrogen was coming out of the stack during the period leading up to the explosion.

 

[SteveElbows]

Another attempt to ascertain reactor integrity using existing detection equipment has failed to provide useful results. This time they tried to use the neutron detectors of reactors 2 & 3:

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111019_01-e.pdf

No healthy detectors were found, with results suggesting short-circuits or disconnects in all cases.

 

[tsutsuji]

http://www.tepco.co.jp/en/news/110311/index-e.html Tepco released a new video showing the 12 October emergency drill.

 

[NUCENG]

Another attempt to ascertain reactor integrity using existing detection equipment has failed to provide useful results. This time they tried to use the neutron detectors of reactors 2 & 3:

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111019_01-e.pdf

No healthy detectors were found, with results suggesting short-circuits or disconnects in all cases.

Sounds like Time Domain Reflectometry. It is not surprising if there has been damage to cables from temperature, core failure, or integrated dose to the cable insulation. The neutron detectors are not considered to be post-accident instruments and have no requirements to survive an accident. It was a good try, but no new information.

I guess we should add that to the list of design conditions that should be discussed or reconsidered.

 

[tsutsuji]

unit 2:

- From 11:20 am to 11:52 am on October 21, aiming to restore the function
of primary reactor water level gauge, we filled the measurement piping
with water from makegarbage gauge (gauge in the makeshift lac) in the
primary reactor Water Level Gauge in Unit 2.
http://www.tepco.co.jp/en/press/corp-com/release/11102106-e.html

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111021_01-e.pdf "Operation of Filling Water to Reactor Water Level Gauge in Unit 2"

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111021_04-e.pdf "Unit 2 Installation Work of Gas Maintenance System of Nuclear Containment Vessel"

http://www.asahi.com/national/update/1021/TKY201110210505.htmlOn 20 October, robot Quince was sent to unit 2 reactor building to measure radiations and take pictures. On its way back, on the third floor, it stopped moving and communicating. Tepco will try to start it again after receiving help from specialists. It it can't be started again, it will be retrieved by employees. Its weight is 26 kg. (see also the video attached to the Asahi article, showing the "lost" signal on the control screen)

(ANN news) According to Tepco, Quince was entangled in a cable, and the communication was cut when it tried to pass over that cable. In case it is needed to send employees to take it back, they will need to work in an area with radiations up to 97 mSv/h.

http://www.tepco.co.jp/nu/fukushima-np/images/handouts_111021_03-j.pdf The location where Quince has stopped is shown on page 4 (pink collapsed robot symbol). The pink numbers are old radiation measurements. The black numbers are the new radiation measurements made by Quince on 20 October (the highest value is 250 mSv/h on 5th floor page 6). The blue numbers are temperatures.

http://news24.jp/nnn/news89023721.html Tepco is releasing a new video taken on 18 October during an inspection of unit 1, whose conclusion is that the emergency cooling system was not damaged by the earthquake before the tsunami.

 

[gregtomko]

I just wanted to make a quick suggestion in case no one else mentioned it. There are some videos on line by "fairewinds associates" and also by"christopher busby" which are painting a very different picture than you see from most other sources. I would be very interested to hear what some knowledgeable people think about those points of view. Unless they have already been addressed, in which case, sorry for being redundant, this is quite a long thread.

 

[Shinjukusam]

I just wanted to make a quick suggestion in case no one else mentioned it. There are some videos on line by "fairewinds associates" and also by"christopher busby" which are painting a very different picture than you see from most other sources. I would be very interested to hear what some knowledgeable people think about those points of view. Unless they have already been addressed, in which case, sorry for being redundant, this is quite a long thread.

Fairewinds associates: They have some good stuff and some bad. Arnie (nice hair) Gunderson is trying really, really hard to establish himself as the go-to guy as a talking head about nuclear issues. He is good at explaining things to non technical people, but I think he overstated his hand a few times in an attempt to be the one who "called" the disaster. For example, he embraced the "reactor 4 is leaning" issue, and made some other questionable statements that weren't backed up by facts.
He does have experience in the nuclear industry but was fired for incompetence (designed a very expensive system that didn't actually fit in the enclosure for which it was build), so he might have a bit of an axe to grind.

Chris Busby: Complete fruitcake. Has a reputation in England for uncovering patterns of leukemia around nuclear power plants but his sampling methodology was heavily biased and the results did not stand up to scrutiny. Also has been selling "purifying supplements" to remove radioactive substances from the body, which are in complete disagreement of actual medical principles (and quite pricey, as well). Seems a: genuinely terrified of radiation and b: willing to scare people into lining his pockets.

 

[tsutsuji]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20111022/0550_1gouki.html During the 18 October inspection of unit 1, it was found that the isolation condenser's water level gauge indicates it is 65% full of water. Tepco earlier testified to the government's investigation panel that the isolation condenser had been shut down by an operator fearing a "boil-dry". Asked whether both findings condradict each other, Tepco said "we are investigating why the operator shut the IC down, based on facts. It remains possible that the level gauge is broken and indicates a wrong value".

[URL]http://www.tepco.co.jp/en/news/110311/images/111021_04t.jpg[/URL]
http://www.tepco.co.jp/en/news/110311/images/111021_3.wmv Unit 1 Isolation Condenser video (taken on 18 October)

 

[rmattila]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20111022/0550_1gouki.html During the 18 October inspection of unit 1, it was found that the isolation condenser's water level gauge indicates it is 65% full of water. Tepco earlier testified to the government's investigation panel that the isolation condenser had been shut down by an operator fearing a "boil-dry". Asked whether both findings condradict each other, Tepco said "we are investigating why the operator shut the IC down, based on facts. It remains possible that the level gauge is broken and indicates a wrong value".

Not being familiar with the local culture and phraseology, this is sometimes very difficult to follow: already in May, in their long report to the IAEA, TEPCO told that the IC hd been shut down at 15:03, to be replaced with the HPCI as the decay heat removal method at 15:07 (IIRC, see earlier postings in this thread for reference). Then it was said having been reactivated briefly between 18:18 to 18:25 (at the time there possible already was some hydrogen to hinder its functionality) and depending on the report you choose to follow, steam either was or was not detected. And then its valve was finally opened at 21:30, at the time it would certainly have been useless.

And now they appear to be hesitant to admit that the logical consequence of their earlier testimony - i.e. that the IC is full of water - is true.

 

[tsutsuji]

My understanding is that the NHK journalist is trying to figure out what happened at 18:25. See also the quotes of the second report to IAEA I made at https://www.physicsforums.com/showpost.php?p=3517649&postcount=11314 . But as everyone seems to agree with the fact that "steam was confirmed" at 21:30, It seems that there was water in the condenser at 21:30. So I don't really understand why the NHK journalist views the 65% water gauge reading of 18 October as a "contradiction".

 

[hbjon]

Fairewinds associates: They have some good stuff and some bad. Arnie (nice hair) Gunderson is trying really, really hard to establish himself as the go-to guy as a talking head about nuclear issues. He is good at explaining things to non technical people, but I think he overstated his hand a few times in an attempt to be the one who "called" the disaster. For example, he embraced the "reactor 4 is leaning" issue, and made some other questionable statements that weren't backed up by facts.
He does have experience in the nuclear industry but was fired for incompetence (designed a very expensive system that didn't actually fit in the enclosure for which it was build), so he might have a bit of an axe to grind.

Chris Busby: Complete fruitcake. Has a reputation in England for uncovering patterns of leukemia around nuclear power plants but his sampling methodology was heavily biased and the results did not stand up to scrutiny. Also has been selling "purifying supplements" to remove radioactive substances from the body, which are in complete disagreement of actual medical principles (and quite pricey, as well). Seems a: genuinely terrified of radiation and b: willing to scare people into lining his pockets.

You criticize the only two people (almost) that the establishment has allowed to put a message out there warning people of some of the dangers we may face. I like both of them because they can do it with a calm and controlled demeanor. Myself, when I try to tell people the physics of Fukushima, I seem frantic and hysterical.

 

[Shinjukusam]

You criticize the only two people (almost) that the establishment has allowed to put a message out there warning people of some of the dangers we may face. I like both of them because they can do it with a calm and controlled demeanor. Myself, when I try to tell people the physics of Fukushima, I seem frantic and hysterical.

So we should throw out scientific analysis and proof as long as the spokesman is calm and controlled? No, I don't think so. I listed the reasons that their testimony should be doubted, if you should choose to dismiss me then that's your prerogative.

 

[elektrownik]

Important: Tepco fixed one of reactor 2 water level indicators and... reactor 2 water level is down scale which mean that water level is at last 5m below top of fuel rods, so reactor could be dry

 

[gregtomko]

Gunderson is trying really, really hard to establish himself as the go-to guy as a talking head about nuclear issues. He is good at explaining things to non technical people

It looked to me like he was just trying to point out some facts that were not being addressed. Information is very tightly guarded around the Fukushima nuclear plant, so it looked to me like he was doing the best he could with what little was available. Everybody gets some things wrong some times.

Chris Busby: Complete fruitcake.

Thats kind of what my feeling was too, but at least an interesting fruitcake :-)

 

[SteveElbows]

You criticize the only two people (almost) that the establishment has allowed to put a message out there warning people of some of the dangers we may face. I like both of them because they can do it with a calm and controlled demeanor. Myself, when I try to tell people the physics of Fukushima, I seem frantic and hysterical.

Gunderson deserves even worse criticism than you see here recently. I don't care how calm he is, he went on about how he knew a thing or two about spent fuel pools, and then proceeded to analyse a video of unit 4 spent fuel pool in a very wrong way. He said the crane had fallen into the pool, and that fuel racks were exposed. He made little or no effort to correct this terrible inaccuracy later. Meanwhile other people who did not have his background or experience were able to look at the same video and reach much better conclusions.

 

[tsutsuji]

http://www.asahi.com/national/update/1018/TKY201110180453.html (18 October) there was a leak of high level contaminated water (290,000 Bq/cm³ of Cs 137) that was found on 18 October during maintenance at the Kurion system when workers entered the area to change a motor. The cause is investigated. The leaked water has already been pumped back to the concentrated waste treatement facility. With 3 tons, it is the second amount of leaked highly radioactive water after the 6 ton leak that occurred in June.

Or in Tepco's words:

- At around 11:00 am on October 18 we found approx. 15cm depth of accumulated
water (approx. 3m3 ) inside the skid, during motor replacement works of the pump
(H2-2) inside the skid of the suspended Cesium adsorption apparatus. We also confirm
that leaking stopped when we found. After that we suspended replacement work of
relative motor and started to drain of the accumulated water by submersible pump. The
cause is currently under investigation.
- At 9:06 pm on October 19, in the water treatment facilities under operation, a SMZ
pump of the 4th process line of cesium adsorption apparatus automatically stopped. A
pump of the 3rd process line is continuously operated. Water treatment by the cesium
adsorption apparatus is also continuously operated at the flow rate approx. 17m3/h (the
flow rate before the automatic stop was approx. 20m3/h).
http://www.tepco.co.jp/en/nu/fukushima-np/past-progress/images/newestfile-e.pdf

http://kyushu.yomiuri.co.jp/news/national/20111022-OYS1T00221.htm The reason of the automatic shutdown of Genkai NPP unit 4 on October 4 was a wrong instruction manual used during maintenance work at a system related with the condenser, Kyushu electric announced on 21 October. The workers removed a cable that supplied electric power to a valve. The degree of vacuum in the condenser declined and that triggered the automatic shutdown.

http://www.kyuden.co.jp/library/pdf/press/2011/111021b-2.pdf Kyushu electric's press release on Genkai unit 4's shutdown. The maintenance was the change of a torque switch at the main turbine gland steam valve. It is a a control cable (not a power cable) that was unplugged, and it resulted in a closure signal being transmitted to the gland steam control valves. It was the first time that this maintenance was done while the plant is running.

 

[Azby]

You criticize the only two people (almost) that the establishment has allowed to put a message out there warning people of some of the dangers we may face. I like both of them because they can do it with a calm and controlled demeanor. Myself, when I try to tell people the physics of Fukushima, I seem frantic and hysterical.

I would make even stronger criticisms of them both. The problem with Gundersen is that he's sometimes been right. But he continues to repeat speculation without substantiating it, even after others have proven him wrong, and I've never seen him retract anything (like the "unit 4 is leaning story"). And he continues to talk about a piece of fuel rod found over 1km away from the plant, but has never shown the evidence for that to my knowledge. As for Busby, the "science" behind his claims and risk estimates has been solidly debunked time and again, even by other anti-nukes and people who are inclined to want to support his positions. It's as bad as UFOlogy. Just because he seems like a nice guy and stands up to authority is no reason to accept his scientific opinion. Wrong is wrong, misleading is misleading, and disinformation is disinformation no matter what the source or motivation.

 

[hbjon]

Chris Busby is a fruitcake? Why? Because he says the stuff that was in those building was really really bad stuff, and it can kill ya? Because he uses the "bedtime story" approach at presenting this dreadfull information? Or is his science all wrong? He seems to think he knows what he is talking about. It is hard to get worried listening to him. I find myself going to sleep.

 

[tsutsuji]

"Tepco never pushed electrical safety plan at nuke plant":

Tokyo Electric Power Co. sources said while consideration had been given in 2006 to connecting all sources of electricity at all six reactors, no decision was made because of technical problems.
http://ajw.asahi.com/article/0311disaster/fukushima/AJ2011102315544

 

[LabratSR]

Unedited Fukushima accident manual released, loss of power sources not envisioned

http://mdn.mainichi.jp/mdnnews/news/20111025p2a00m0na007000c.html

 

[NUCENG]

Unedited Fukushima accident manual released, loss of power sources not envisioned

http://mdn.mainichi.jp/mdnnews/news/20111025p2a00m0na007000c.html

First question: What are the pressure limits and process requirements for venting? Did they follow their manual?

 

[LabratSR]

From the Japan Times article on the manuals.
http://www.japantimes.co.jp/text/nn20111026a1.html

"Instructions in the manuals were all based on the assumption that two backup direct current batteries at reactor 1 would keep working throughout any emergency. In fact, the batteries were knocked out by water when the monster tsunami struck and crippled the Fukushima plant.

The manuals also failed to instruct workers to open by hand critical valves normally powered by electricity to vent steam and thus reduce pressure in the containment vessel. The DC batteries were supposed to supply power to operate those valves.

The containment vessel is the last line of defense to prevent radioactive materials from escaping the reactors. Tepco tried to open the valves to keep the vessel from breaking apart on March 12. Pressure also needed to be reduced to allow coolant water to be injected to prevent a meltdown of the reactor core.

But it took hours for Tepco workers, who apparently had no training in how to open the valves manually, to vent the steam and relieve the pressure, and many experts say the delay may be a key factor that led to the meltdown at unit 1."

 

[Norman]

Interesting paper posted on the Xenon and Cesium releases from the disaster.

http://www.atmos-chem-phys-discuss.net/11/28319/2011/acpd-11-28319-2011.html

The paper states there is some evidence the that Xenon release happened very early correlating with the Earthquake and not the Tsunami damage.

 

[NUCENG]

From the Japan Times article on the manuals.
http://www.japantimes.co.jp/text/nn20111026a1.html

"Instructions in the manuals were all based on the assumption that two backup direct current batteries at reactor 1 would keep working throughout any emergency. In fact, the batteries were knocked out by water when the monster tsunami struck and crippled the Fukushima plant.

The manuals also failed to instruct workers to open by hand critical valves normally powered by electricity to vent steam and thus reduce pressure in the containment vessel. The DC batteries were supposed to supply power to operate those valves.

The containment vessel is the last line of defense to prevent radioactive materials from escaping the reactors. Tepco tried to open the valves to keep the vessel from breaking apart on March 12. Pressure also needed to be reduced to allow coolant water to be injected to prevent a meltdown of the reactor core.

But it took hours for Tepco workers, who apparently had no training in how to open the valves manually, to vent the steam and relieve the pressure, and many experts say the delay may be a key factor that led to the meltdown at unit 1."

That is possible. Venting would reduce pressure in containment and subsequently allow continued depressurization for the RPV. This would allow low pressure external fire pumps or trucks to make up water to the reactor. If melting was not already underway then delaying venting could be a key factor.

However, as I understand the timeline at unit 1 the Isolation Condenser had been tripped, there was no water makeup to the core, inventory was being lost due to the SRVs venting the vessel to containment, and containment was more than double its pressure rating for a period of hours. Under those conditions the core would have begun melting shortly after fuel was uncovered, increasing temperatures at a rate of about 1 degree per second. Once zirc water reactions start that is an exothermic reaction increasing boiloff and heating. A large part of the delay was to get government permission to vent. IMO, operator training for manual vent operation is a contributing cause but not at the top of the list. Operators did not have the authority to take action when it might have helped. Their emergency manuals may have been woefully inadequate, so naturally the training or lack of training on implementing the manual would be suspect. In short, the core was probably melting before they even tried to vent.

I know I have harped on this before, but even that wasn't the real root cause. Japanese industry and regulators built plants and then stopped looking. They ignored geological findings about earthquakes and tsunamis. They built up a regulatory system that left no one responsible. The repeated scandals of fudged paperwork and testing were warnings. The KK earthquake was a warning. Japanese attitudes that they didn't need to worry about 9/11 terror because Japan was a 'stable society' was a warning.

Was it complacency, or greed, or negligence, or incompetence? I know this is the technical thread, but in this case I am not sure the accident could have been prevented by any technical solutions.

 

[Astronuc]

Was it complacency, or greed, or negligence, or incompetence? I know this is the technical thread, but in this case I am not sure the accident could have been prevented by any technical solutions.

Certainly not after the fact.

The proactive actions of ensuring the protection of EDGs and their fuel supply, and ensuring the protection of the electrical lines from EDGs to the ECCS and safety systems, should have been a priority. Ensuring protection = prevention of flooding and prevention of failure due to seismic loads.

 

[Bandit127]

Interesting paper posted on the Xenon and Cesium releases from the disaster.

http://www.atmos-chem-phys-discuss.net/11/28319/2011/acpd-11-28319-2011.html

The paper states there is some evidence the that Xenon release happened very early correlating with the Earthquake and not the Tsunami damage.

An article in Nature about the same paper I think.
http://www.nature.com/news/2011/251011/full/478435a.html"