Fukushima Japan Earthquake: nuclear plants Fukushima part 2

[jadair1]

http://www.tepco.co.jp/nu/fukushima-np/handouts/2014/images/handouts_140707_01-j.pdf
(In Japanese)

They had to stop the cooling of the SFP at Unit 5 in Fukushima Daiichi, because of a leak that occurred at a valve located on the pipe that brings in sea water, to be used for cooling pumps and to remove heat from the water used for cooling the SFP.

The water leaked - clearly sea water, based on analysis, with no trace of radioactivity - amounts to ~1300 liters and most of it went down to the lower levels, about two floors.

The SFP is safe even without cooling for about 9 days. Should the repair last longer than that they consider diverting some cooling water from the circuits used for cooling the reactor itself. These circuits are working normally.

I have never worked in a NPP but I have worked many shutdowns in steam plants at pulp mills many years ago.

It seems like a simple procedure to replace the ruptured valve, lock out and isolate the valve, remove it and replace it.

It does not seem like radioactivity should be a problem, perhaps they have no replacement valves available, now that would be a different kettle of fish.

Even then they could burrow one from another company that has a suitable replacement on hand.

I know that Northwood Pulp in Prince George, BC did this on more than one occasion when they got into a bind.

 

[Sotan]

Well, replacement would have been my first choice too but for some reason that I don't know, they decided to do it in a completely different way. Enlarged that little hole in the valve's body, stuck a plug or something in it, and applied some hardening agent (?) on the surrounding area.
Check the link given above again, it contains the repair photos too now.

 

[Sotan]

http://www.tepco.co.jp/nu/fukushima-np/handouts/2014/images/handouts_140707_05-j.pdf
(In Japanese)

26-pages report of July 7 on the progress of works for sealing the trenches of Units 2 and 3, with a lot of info (including several photos) about the freezing of certain points in order to stop the water from going through.

It is rather technical and I suppose harder to understand compared to other reports (at least to me), but may be worth browsing. Again one gets a hint of how big and difficult the task is.

 

[westfield]

Daiichi U5

Well, replacement would have been my first choice too but for some reason that I don't know, they decided to do it in a completely different way. Enlarged that little hole in the valve's body, stuck a plug or something in it, and applied some hardening agent (?) on the surrounding area.
Check the link given above again, it contains the repair photos too now.

Yes, well if that's how a multibillion dollar company stages "repairs", even a provisional one as they call it, then I am dumbfounded. Some sort of polyurethane sealant from the hardware store, a wooden block and ratchet straps. The valve body is obviously shot, corroded\eroded from inside which is surely a predictable failure.

A continuing sad farce.

 

[Sotan]

The "range" of their attitudes and accomplishments is what amazes me. The distance between the highs and the lows.
You see them building ice walls, or the ALPS, installing countless tanks, handling robots, removing debris and cleaning and preparing and so on, so many huge tasks which I am not sure somebody else would have done much better.
But then you also see them pressing the wrong buttons, sending contaminated water where it shouldn't go, forgetting to cut electricity before doing some work, or repairing a valve hole with plug and sealant.
How to explain that. Different teams and different approaches? And the human factor?

 

[jim hardy]

Don't be too quick to condemn that temporary patch on the valve. From out here we do not know what else is connected to that piece of pipe, it may well be that to drain it renders something else inoperable that they'd rather not shut off just now.

 

[zapperzero]

How to explain that. Different teams and different approaches? And the human factor?

Under the keiretsu system, sub-sub-sub-sub-contractors end up doing most of the grunt-work; they do it for very little money and with very little oversight. Big-ticket items get handled by the big fish directly, and they actually pay people, train them and care about their corporate reputation.

 

[Sotan]

Don't be too quick to condemn that temporary patch on the valve. From out here we do not know what else is connected to that piece of pipe, it may well be that to drain it renders something else inoperable that they'd rather not shut off just now.

I agree, there must be reasons.
They could have explained them a little, though.
Otherwise, just showing that repair there... may seem a little weird.

 

[Rive]

Well, replacement would have been my first choice too but for some reason that I don't know, they decided to do it in a completely different way.

IMHO it can be about the usual papermill of the permissions and components. It might be weeks to get everything ready for the work - while that cooling would run on reserve, without any further reserves.

With that patchwork it'll have the 'main' and the 'reserve' for all the time of the papermill.

I would be worried only if the proper replacement would not be performed within a month or two.

 

[Sotan]

Two short new reports on Tepco site (unfortunately only in Japanese):

1. (Daiichi plant) 2 pages report with 2 photos of the collapsed NW portion of the Unit 3 building here (the photos can be seen in larger size here.

2. (Daini plant) This report announces that all 764 fuel units of Reactor 1 have been moved to the spent fuel pool.

 

[zapperzero]

That beam which is featured in both pictures is cracked in the middle. I guess it's a good thing they cleared the debris above it so (relatively) fast.

 

[Sotan]

IMHO it can be about the usual papermill of the permissions and components. It might be weeks to get everything ready for the work - while that cooling would run on reserve, without any further reserves.

With that patchwork it'll have the 'main' and the 'reserve' for all the time of the papermill.

I would be worried only if the proper replacement would not be performed within a month or two.

In a new post on their site, TEPCO announces that they will replace the pierced valve with the similar one from Fukushima Daini Unit 3.

This should take until the end of month. Until then, they will cool the reactor and the SFP alternately using the cooling system that is in working state.

http://www.tepco.co.jp/nu/fukushima-np/handouts/2014/images/handouts_140717_03-j.pdf (in Japanese)

 

[Sotan]

http://www.tepco.co.jp/nu/fukushima-np/handouts/2014/images/handouts_140717_05-j.pdf
(in Japanese)

Overview on the planned dismantling of the cover of the Reactor 1 building.
General presentation of the dismantling operation.
Measures for preventing the spreading of dust and other particles. (Spraying of water and some special agent that fixes dust and other particles in place.)
Throughout the operation they will monitor 19 spots for changes in radioactivity.

This article from Asahi Shinbun kind of relates to the above:
http://ajw.asahi.com/article/0311disaster/fukushima/AJ201407160064

 

[zapperzero]

Thank you for the update. I wonder why they put up the tent in the first place.

 

[Sotan]

The "Mid-and-Long-Term Roadmap" report of June 27 (most recent one) has been translated in English and posted on the METI site here.

 

[Hiddencamper]

I'm not sure where the actual report is, but apparently Japanese regulators determined on their own that the tsunami was the cause of the accident at Daiichi, and the earthquake did not cause the event.

http://www.neimagazine.com/news/newsdaiichi-accident-caused-by-tsunami-not-earthquake-japanese-regulator-concludes-4322346

If anyone can find this report, please let me know!

 

[jim hardy]

I agree - the high water killed the electrics which pretty well doomed the plant.
It would have survived the earthquake with no tidal wave
but not the tidal wave with no earthquake.

Events followed reasonably closely a "Loss of all AC Power" scenario hypothesized years ago by Oak Ridge.
http://web.ornl.gov/info/reports/1981/3445600211884.pdf

 

[Sotan]

I read about that too, on several sites.

I believe the reports of the Japanese regulator (NRA) are those from http://www.nsr.go.jp/committee/yuushikisya/jiko_bunseki/20140718.html

(Unfortunately, they are only in Japanese.)

The first two of them (1-1 and 1-2) are about the causes of the loss of electric power in Unit 1.

The next two (2-1 and 2-2) contain a more general evaluation of the nuclear accident at Fukushima Daiichi (they actually contain the 7 items researched by NRA which are mentioned in the link given above by Hiddencamper in post #527 (1. Minor water leaks at unit 1, 2. Loss of function in emergency power supply at unit 1, etc., up to 7. Hydrogen explosion at unit 4.)

The last report (2.3) is a short material called "About the method for further research in the future".

As translating such materials in full would require more time than I have (I haven't even perused them properly at this moment), I can only hope they will be translated in English at some point in the near future. Or, as always, if you have more punctual points of interest, I could try to find those portions and attempt to present a summary.

 

[Sotan]

Today I took a look at those reports and I have to say that the short newspaper article linked by Hiddencamper actually can serve as a good summary - at least for non-specialists like me. The reports are simply much more documented, they take each item and discuss it in relation with the earlier findings of the Parliament commission that investigated the accident, they list the evidence and discuss it, but the conclusions given in the newspaper articles actually do convey the main content.

Also, I have to confess that the first two reports are extremely technical and, because they refer to electrical issues, I really don't understand much (I only have a mechanical engineering degree).

---------

But: the main reason I post this time is to say I am impressed by this new source of information I found while searching for the report wanted by Hiddencamper: the NRA site, the homepage of the Japanese nuclear regulating authority.

Every two weeks or so they have a meeting, for which they post the schedule, the discussion agenda, the materials used for those discussions, a detailed record of all the talks, as well as a video recording on Youtube. http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/

I browsed through the minutes of the meeting of June 6 (the last available - it seems that the minutes are posted a good while after the meeting is over) and it was actually very interesting. TEPCO has several representatives who that attend these meetings and who know what's in those materials they prepared. They are the first to speak, and they take each material which has been prepared for the meeting, and present it in detail, explaining what is on every page, every diagram. Then the invited experts and NRA members express opinions or ask questions, to which TEPCO representatives answer. This goes on until all topics are approached. The June 6 meeting was about TEPCO's progress in building the ice wall.

For somebody who really follows the events, these minutes are probably invaluable. Many of the facts that transpire in only several words in newspaper articles and news could be much better explained based on materials and discussions held here. Specialized journalists are probably reading these and then conveying what they can, but they probably have to deal with space limitations, plus how much of the public is really interested in details.

For example, I remember at some point that 1) some people were worried how will the ice wall affect the stability of the terrain (won't the soil sink?) and therefore the buildings in the Fukushima Daiichi complex. 2) TEPCO replied that they are confident such effects, if any, will be negligible. 3) people expressed concern regarding how well grounded was this conclusion and what were their arguments. Well, among the materials of the NRA meeting of May 26 there's an http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/data/0022_02.pdf that deals exclusively with this issue. Of course I cannot say I read and understood it all and I can say anything about the scientific conclusions they drew - but it does show that they are at least trying to do a serious job.

This was just one example... I still don't know how to deal with the amount of information, but I will browse through it and post when I find something interesting.

 

[Sotan]

And again I jump to something else (apologies!)

I found this very instructive video which some of you might have missed.
It does have some rather unrelated portions, but the first 20 minutes or so present the works for opening Reactor 5 at TEPCO's Kashiwazaki-Kariya plant for scheduled maintenance.
Also, at min. 46:40 or so there's a short appearance of Fukushima Daiichi, as they are restarting a reactor after maintenance.
It's been shown on TV first in 1994.
It's only in Japanese, but still, worth a look, at least it was for me.

 

[Sotan]

NHK English article of Jul 23:
http://www3.nhk.or.jp/nhkworld/english/news/nuclear.html

 

[Sotan]

Another NHK English article, Jul 23:
http://www3.nhk.or.jp/nhkworld/english/news/nuclear.html

These NHK reports are actually good summaries of the presentations made by TEPCO in the NRA meetings.

 

[zapperzero]

A some of you might have missed.

Don't think I've seen it before. Thanks.

 

[Sotan]

I haven't read the NAS Report itself, instead I found this comment by Dave Lochbaum, on the UCS site:

http://allthingsnuclear.org/nas-report-lessons-learned-from-fukushima-nuclear-accident-for-safety-of-u-s-nuclear-plants/ (July 25, 2014)

Worth a look.

 

[Sotan]

IMHO it can be about the usual papermill of the permissions and components. It might be weeks to get everything ready for the work - while that cooling would run on reserve, without any further reserves.

With that patchwork it'll have the 'main' and the 'reserve' for all the time of the papermill.

I would be worried only if the proper replacement would not be performed within a month or two.

Follow up on this issue:
http://www.tepco.co.jp/nu/fukushima-np/handouts/2014/images/handouts_140730_05-j.pdf (in Japanese)
They took out the valve and discovered it was deeply corroded on the inside.
It originally had some (rubber?) lining on in the inside, that was mostly gone, plus the metal was deeply corroded too, hence the piercing of the valve body and the 3 mm diameter hole.
The cause they indicated is the high speed of water through the valve in that region; the valve was kept open only 30% for a long time, a rather unusual regime, which led to high fluid speed in that area. That damaged the rubber lining and opened the way for corrosion. They replaced this valve with the similar one from Fukushima Daini plant Unit 3 which was in good condition. They will check this valve more often in the future.

They dismantled another similar valve in the vicinity of this one, and they found some damage to the rubber lining; they repaired that and put the valve back, but they plan to replace this one too, with a new one, in the future.

The cooling of the SFP at Unit 5 in Fukushima Dainichi has thus been restored using the usual circuit.

 

[Hiddencamper]

TEPCO releases their next report on unexplained occurrences at Fukushima Daiichi

http://www.tepco.co.jp/en/press/corp-com/release/2014/1240140_5892.html

(if you recall, the first major report came out in dec 2013 http://www.tepco.co.jp/en/press/corp-com/release/2013/1233101_5130.html)

The key findings from this report: Unit 3 RCIC likely tripped due to high turbine exhaust pressure. Unit 3's HPCI likely stopped injecting earlier than originally expected due to low steam supply pressure, which meant that fuel damage likely started a few hours earlier and that there was greater damage at unit 3. This may help close some of the gaps as to why unit 3 had so much hydrogen compared to units 1/2.

 

[Sotan]

Good and quick find, Hiddencamper - that English summary report.

In case somebody is interested, the full report and the load of related materials are available at http://www.tepco.co.jp/cc/press/2014/1240099_5851.html

But they are only in Japanese.

 

[zapperzero]

The report also determined that the detected presence of neutrons near the facility's main gate on March 13-14 was the result of spontaneous nuclear fission of easy- to-decay (short-life) actinides in Units 2 and 3 as the result of the fuel melting, and not a return of the reactor core to recriticality (sustained nuclear fission).

I would like to see the reasoning behind this. Also, I don't recall anyone claiming that sustained nuclear fission was taking place at that time. That seems an odd thing to disprove - what might need disproving is the claim that there were short fission bursts taking place because of the core debris being (re)flooded.

Too, the actual summary report does not use nearly the same assured tone, to wit:

"It is possible that intermittent increases in nuclear pr
essure after forced depressurization at Unit 2 (issue list
"Unit 2 - 7") may have been due to hy
drogen and water vapor discharged while
fuel was melting. In conjunction,
the neutrons observed near the main
gate may have been generated by th
e spontaneous fission of actinides
discharged while fuel was me
lting at Units 2 and 3. "

http://www.nrmc.jp/en/report/detail/__icsFiles/afieldfile/2014/08/06/er9.pdf
has more detail

It's funny how they claim there is no correlation between gamma ray spikes and neutron spikes, but then on page 28 they show a gamma+neutron spike starting at or near the time when water injection from fire engines starts.

 

[mheslep]

I would like to see the reasoning behind this. ...

I dunno, but the gamma signatures from the fission of generated actinides, versus that from critical U235 would be like a fingerprint.
http://www.lanl.gov/orgs/n/n1/panda/11. Nuclear Data for NDA.pdf

 

[jim hardy]

I would like to see the reasoning behind this.

I remember being glued to the computer back when this was going on. (I'm retired from a plant so was very interested).

If i recall
that indication came from neutron detectors at the entrance gate . That seemed strange to me for in my plant we didn't have any way out there . The level was extremely low, almost individual counts.
It was about the same time as water was being added and some venting, to best of my recollection.
Wind was in the direction from plant toward entrance gate - that i do remember checking.

so at the time i assumed it was some neutron emitting fission fragments carried out through the vents, generated when water hit hot and crumbly fuel elements. Or else hot particles on somebody's muddy boots.


Does that jibe?