Fukushima Japan Earthquake: nuclear plants Fukushima part 2

[jim hardy]

(One photo shows a worker looking into the reactor using binoculars.)
- 382 units of fuel have already been moved by June 13. In the upper right of the page there is a detailed presentation of the procedure for removing fuel units. For every group of 4 fuel units there is a control rod in the center. Two fuel units are removed so two are remaining, diagonally, to support the control rod. An auxiliary device is then inserted to support the control rod while the remaining two fuel units are removed. Then the control rod is pulled out, and then the auxiliary device removed. In all, it is computed that 1200 such “steps” will be needed to remove the 764 fuel units.

They're lifting complete elements?
Do i understand then that they are in good enough shape to be lifted from the top, and so are the control blades?

 

[turi]

They're lifting complete elements?
Do i understand then that they are in good enough shape to be lifted from the top, and so are the control blades?

The report is about Daini, not Daiichi.

 

[nikkkom]

Well, the "low energy" comes into play when tritium is an external contamitant. Electrons with av. 5.4 keV are sufficient to break bonds in organic matter.

Wrong. Energy does matter a lot for internal irradiation too.

18 kEv electron from Tritium can break only a few bonds.

Compare that to two beta electrons from Sr-90 -> Y-90 -> Zr-90 decay chain, first electon is 546 kEv, second is 2280 kEv - more than two orders of magnitude more energy. They damage A LOT of molecules while decelerating.

 

[jim hardy]

The report is about Daini, not Daiichi.

Whew ! Thanks ..

 

[Sotan]

Sorry, wasn't clear enough. I edited that post to make it clearer.

 

[turi]

ALPS is fully back online:
http://www.tepco.co.jp/en/press/corp-com/release/2014/1238403_5892.html

On May 23 Unit B was the first to be restarted after the upgrades, followed by Unit A on June 9 and now Unit C on June 22.

 

[Sotan]

That's good news.
But there's some bad news too:
http://www3.nhk.or.jp/nhkworld/english/news/20140625_09.html

 

[Rive]

That's good news.
But there's some bad news too:
http://www3.nhk.or.jp/nhkworld/english/news/20140625_09.html

Ex-SKF article about the same thing.

 

[Sotan]

A new monthly "roadmap" report has been published on June 27. Unfortunately all materials are in Japanese only, at this time.
All the documents are here.
The summarized version of the progress report (the one that will be translated in about 2-3 weeks, if the past trend continues) is here.
I only took a quick look but it doesn't seem to contain new information, meaning which hasn't been at least mentioned here previously.
One exception - for me at least this was news: [STRIKE]the crane above the spent fuel pool[/STRIKE] a crane on the first floor at Unit4 is entering a mandatory inspection, which means that the extraction of fuel units from SPF 4 will take a break from July 1st till the beginning of September. This is a scheduled inspection, not an unexpected delay.

Edit: the crane and its location can be seen on the last page of this document.

 

[Sotan]

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.

 

[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?

 

[Hiddencamper]

Consider that unit 3 underwent an automatic depressurization system (ADS) blowdown, and with this new data, we know the fuel was already damaged/melted when ADS actuated. The ADS system would have discharged a lot of fission products and noble gasses to the suppression pool.

Unit 3 did have containment venting a short while after the ADS blowdown:

http://www.cas.go.jp/jp/seisaku/icanps/eng/03IIfinal.pdf

Although depending on specifically what you read, its possible that venting may not all have gotten to the stack. Some of it may have went to unit 4, some may have gone into the reactor building. The venting was from the suppression chamber. This would have created a direct pathway for radioisotopes to migrate from the damaged fuel, out the safety relief valves to the suppression pool, and out the suppression pool to the environment.

This isn't a sure thing, just an idea looking at what we know.

 

[zapperzero]

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

I am not sure the gamma detectors they had were all THAT sensitive/discriminating.
Too, one does not exclude the other.

 

[mheslep]

I am not sure the gamma detectors they had were all THAT sensitive/discriminating.
Too, one does not exclude the other.

I only know detectors that can discriminate gamma (obviously) exist. No information what was on site.

 

[etudiant]

The recent TEPCO statements do seem to provide a coherent sequence for the failure of the three reactors.
Clearly the reactor systems functioned largely as designed and postponed the meltdowns, but not long enough for the operators to regain control. This raises the question whether anything could have averted the disaster once the tsunami had struck, had the operators had better knowledge.

 

[jim hardy]

This raises the question whether anything could have averted the disaster once the tsunami had struck, had the operators had better knowledge.

With hindsight there's some things that could have been tried, for example ignoring the vessel's cooldown limits and cooling the reactor very quickly to below 100C..
Nobody knew how big the tidal wave would be. Who'd thermal shock a reactor vessel for a "maybe" ?

But without electric power they were trapped . Lots of heat to get rid of and no way to move it.

Probably they'd have been able to only postpone things a matter of hours or very few days.

just my thoughts...

old jim

 

[Hiddencamper]

I think, if they did not lose DC batter/control power at units 1/2, then maybe, they might have been able to do something.

24 hours should be more than ample time to restore power or at least implement a decay heat removal solution. But they spent so much time dealing with no reactor indications, trying to figure out the state of their cooling systems, the inboard valves for the IC at unit 1 appears to have isolated on loss of control power, and shortly after that they were dealing with core damage, high rad levels, explosions, personnel shortages.

Seriously, I think if they had control power at units 1/2, they would have kept core cooling capability of the unit 1 IC, and rather than spend time trying to figure out the status of unit 1/2, they could have devoted resources to an ultimate heat sink solution similar to the Daini site.

On a separate note, the Us industry does not assume total DC control power failure for any scenario, including the new Fukushima based scenarios or for the AP1000. I think this is a significant gap, and that there needs to be training on how to deal with this. The extensive damage mitigation guidelines do have steps for performing specific tasks without control power, like hooking batteries up to instruments to get readings, but a total cd power loss would be extremely challenging to deal with as you would be blind to the majority of your indications.

Just my thoughts.

 

[jim hardy]

The extensive damage mitigation guidelines do have steps for performing specific tasks without control power, like hooking batteries up to instruments to get readings, but a total cd power loss would be extremely challenging to deal with as you would be blind to the majority of your indications.

That's the one plant guys have nightmares about. Without DC you can't start your diesels, either.

At my plant we knew just where to connect engine driven DC welders. But you're right it wasn't in procedures . Well, more correctly it wasn't when i retired twelve years ago.

 

[jim hardy]

Hmmmm they're working on it.
http://www.gpo.gov/fdsys/pkg/FR-2012-03-20/pdf/2012-6665.pdf

golly I'm out of date ! It even mentions coronal mass ejection...

 

[Hiddencamper]

We can start our DGs once without control power. I actually simulated the emergency start procedure today for one of my license qualifications. But we are just one plant. Manually open the air start solenoids, while you have a guy standing by the generator breaker and service water breaker to close them in and at least pick up the bus. Let the mechanical governor hold the engine rpm until you can bring the battery charger on service.

Obviously it's a very complicated procedure. If 9/11 and Fukushima brought anything good, it's the fact that we actually have this procedure and others like it, and we train on it.

 

[jim hardy]

Manually open the air start solenoids,

Now THAT's interesting.

I wonder if they've added such a bypass at my prior plant.

Our diesels were air cooled by huge radiators and the fans driven mechanically by engine shaft so they needed no service water
had hours of fuel available by gravity feed day tank
the air start reservoirs were sized for five start attempts
the starting air electric compressors could run from either bus
and we had a small one cylinder diesel compressor to recharge the start reservoirs if things ever got that bad...
...but we needed battery.

How'd you flash your field? Pilot exciter?