Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[sheffters]

This gives rise to frustration and the opinion in some minds that TEPCO are witholding information. In fact, TEPCO are only witholding interpolation and opinion. Rightly in my mind.

They don't help themselves though in the eyes of the world. They can do it when they want to.

"Explosive sound and white smoke were confirmed after the big quake occurred at 3:36 pm on March 12. It was assumed to be hydrogen explosion."

So why not state the facts and the most likely cause to save all the speculation? They could best guess (aka assume or similar wording) based on what they know.

They could also employ some decent translators. Some of their phrasing is ridiculous. Surely between TEPCO, IAEA, NISA, JAIF and a whole host of others international bodies they have someone who understands the nuclear lingo and can translate effectively.

Ian.

 

[Most Curious]

While the guidance requirements seem to be pretty effective, they are not totally robust.
If memory serves, the Besse Davis reactor vessel had the head almost corroded through, as no one asked where the copious rust in the water was coming from. More seriously, slowly emergent problems such as the risks posed by overfilled spent fuel pools do not seem to be surfaced very effectively. Is there an industry mechanism to help bring such generic problems to the foreground?

IIRC the Davis Besse head was corroded from the OUTSIDE, therefore no evidence would have existed in the coolant.

 

[etudiant]

IIRC the Davis Besse head was corroded from the OUTSIDE, therefore no evidence would have existed in the coolant.

You are of course correct and I was mistaken. The reference should have been to the boric acid buildup around the head.
The gory details are in this report:
http://www.nrc.gov/reactors/operati...essons-learned-files/lltf-rpt-ml022760172.pdf

 

[NUCENG]

You said:




What is wrong with it? Wrong that you regret that *after this disaster* (word "now" in the above quote has that meaning), there is a "need to make sure it doesn't happen somewhere else". Which is WRONG, THIS NEED WAS THERE EVEN BEFORE THE DISASTER. Waiting for a disaster to happen in order to start looking at the problems seriously is WRONG.

How can I say this even more clearly?



Wrong again. I don't have to prove that plants are unsafe. It's the other war around - the nuclear industry must prove to the satisfaction of the people that they are safe.

There is a direct parallel with Challenger disaster. Engineers who voiced concerns about O-ring erosion were asked to provide a proof that O-rings can be breached. Rogers Report specifically points out that managers were dead wrong about it. Shuttle can be launched not when engineers can't prove it's unsafe to do so, it can be launched only if engineers are sure that it is reasonably safe to do so!

Your believe that everything is shiny in France, Russia and US just because this disaster happened in Japan, not those countries. I am not so sure about it.

I read post-disaster reports after both Shuttle disasters, I know how stubborn people may be in (self)deception about safety when it comes to multi-billion projects. NASA managed to self-hypnotize itself into believing Shuttles are safe even after NASA itself dramatically proved it's not true.

We are basically in port-Challenger state right now in regards to NPPs, and unless we start to do something differently now, we are going to get Columbia.

The reaction of worldwide nuclear community up to now is mostly PR. PR is not going to convince me. I need to see deeds, not words.

"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled", said Richard Feynman, and I fully agree with him.

While you are trying to parse words and change the meaning of what I wrote, have you figured out what the definition of is is? ;-}

I agreed with you that the need was there before the accident. Quote: "You are right that the need was there, and it wasn't done." Do you also want to argue with yourself? Does agreeing with you make me "stubborn and self-deceptive"?

It does appear you didn't read my post because I specifically said I could not answer for France and Russia.

I did not ask you to prove plants were unsafe. Again, if you look at my previous posts you will find that I don't believe the word safe is meaningful. Risk is meaningful and nothing in life is risk free. The shuttle disasters demonstrate that point well. As new risks were discovered they were fixed. Risks include human errors. But the benefite of space exploration were balanced against the clear risks and the program continued.

I asked you to discuss concrete steps being taken by industry and referenced in my earlier posts. I've explained that American nuclear plants and regulators continuously review design bases and new information and operating experience. We are not "waiting around for a disaster." You don't believe that and you want to win the argument simply by labeling me as "WRONG." If you continue with rants that don't add to the PF forum I will report them to mentors for deletion. I would much rather discuss specifics. I can't do anything about your fears, opinions, and feelings.

Give it a try, you might learn something. Even better, I might learn something.

 

[tsutsuji]

http://www.yomiuri.co.jp/science/news/20110706-OYT1T00400.htm Parts of the cover structure for unit 1 have arrived at the plant harbour this morning after being brought by boat from Onahama Port. They are two 35 ton concrete foundation stones. They are going to be unloaded by crane.

http://www3.nhk.or.jp/news/html/20110706/t10014003071000.html Tepco wants to calculate by the end of this month an estimation of the radiation emitted by the reactor building(s). The purpose is to be able to compare the figures and measure the effect before and after the cover has been completed.

http://www.nikkei.com/news/category...3E2E2E2E2E2E2;at=DGXZZO0195591008122009000000 3 workers have been sent to hospital today ; 2 are workers in their twenties suffering from hyperthermia, one laying cables at unit 1's turbine building, the other controlling entrance and exit at the West Gate. The third one is a heavy equipment operator working near unit 4 who slipped in a stair.

http://www.nikkei.com/news/category...39F9FE2E2E2E2;at=DGXZZO0195165008122009000000 Tepco is unveiling a plan to build a new water treatment system to be completed by spring or summer of 2012. The plan is to purify water in each reactor rather than go on sharing the present water treatment facility with its 4 km long pipes. The reactors will require cooling by water injection for years before the fuel can be removed (at Three Mile Island it took 10 years). The present water treatment facility has been designed with a durability of one year.

http://sankei.jp.msn.com/economy/news/110705/biz11070516200015-n1.htm Interview of Areva vice president Dominique Mockly in Paris on 4 July : Areva will supply Tepco with evaporation equipment for the final treatment of the contaminated water.

http://www3.nhk.or.jp/news/html/20110706/t10014013131000.html The water treatment facility achieved a utilization rate slightly above 80% during the week up to 5 July. But it was only 55% before that, as the facility encountered a number of issues on 29 and 30 June. So as a whole the 80% goal is not achieved. While Tepco wants to achieve an 80% goal, the 90% goal is abandoned.

http://mainichi.jp/select/today/news/20110706k0000e040049000c.html From 16 June to 5 July, 46 adsorption towers have been replaced at the Kurion facility. The maximum radiation at the surface of the vessel was 6.1 mSv/h. The maximum worker exposure was 1.13 mSv. Tepco is studying improvements, including changes in replacement frequency, in order to diminish worker exposure.

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110705_01-e.pdf and http://mainichi.jp/select/weathernews/news/20110706ddm001040018000c.html Tepco announced on 5 July the completion of the work to seal the water intake at units 1,2,3,4. An amount of 109 concrete plates (32 cm thick, 4560 kg heavy) were installed as shown in the Tepco handout pdf.

http://www.mbs.jp/news/jnn_4769268_zen.shtml a video made last week on the plant site, independently acquired by JNN.　It shows an automated machine performing debris removal near unit 3, the open doors at unit 2 reactor building, the fallen crane near unit 5 sea water intake, the blue tanks used for storing decontaminated water, and the arrival of the cover parts at the harbour.

http://www.tudou.com/programs/view/Cw5FeFIJxeI/ the video released by Tepco on 14 June showing the Meccano-toy-like construction of the cover structure. I guess the music is not from Tepco, though.

A 1 minute long accelerated version of 24 hours of Fukushima Daiichi Nuclear Power Plant　Live Camera. 2011-07-05

 

[zapperzero]

http://www.mbs.jp/news/jnn_4769268_zen.shtml a video made last week on the plant site, independently acquired by JNN.　It shows an automated machine performing debris removal near unit 3, the open doors at unit 2 reactor building, the fallen crane near unit 5 sea water intake, the blue tanks used for storing decontaminated water, and the arrival of the cover parts at the harbour.

Thanks for all these informative links. I was not aware there was a fallen crane? Also, it will be interesting to see how much contamination TEPCO thinks is going on.

 

[jim hardy]

Bandit observed "This gives rise to frustration and the opinion in some minds that TEPCO are witholding information. In fact, TEPCO are only witholding interpolation and opinion. Rightly in my mind.""

I hope they will make public in what condition they find the reactor vessels.

I believe they are withholding information.
Perhaps it's rightly withheld, for it would be leapt on by sensationalists in the irresponsible sector of press. ... maybe product liability lawyers too.

Reason i say that is from observing the scarcity of hi res photos of unit 3, as was noted by Atlantic Monthly back in April:
"Unfortunately, Welch couldn't share the specifics of the missions his team flew. The cone of secrecy around Fukushima extends far and wide. We don't get to know where they launched from or what their camera targets were. He couldn't discuss whether their operations center had a roof over it or not, or whether it was a tent. We don't even know how many flights they made, though he confirmed it was "a bunch."
http://www.theatlantic.com/technolo...he-drone-missions-to-fukushima/237981/#slide6

the plastic covers will keep away roving eyes in the sky.

but were they my reactors i just might do the same thing.

 

[tsutsuji]

Thanks for all these informative links. I was not aware there was a fallen crane?

We talked about it in May :

I add a picture showing how they look like -these are from N°5 reactor and got hit by this big blue structure, but they look similar to the others:

http://www.netimago.com/image_202944.html

The trajectory of the big blue structure, a gantry crane, is shown on page 40 of http://www.tepco.co.jp/nu/fukushima-np/images/handouts_110525_01-j.pdf. (...)
English version is now available at http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110525_01-e.pdf

 

[robinson]

I'm not sure anymore where to even post at times, too many threads.

After some investigation, we can now confirm that the Kauai Monitoring Station in Hawaii broadcast yet another Radiation Alert recently (see graph at right), commencing toward midnight of June 29th and continuing into the early morning hours of June 30th.

This is becoming somewhat of a routine event for the Kauai station, considering elevated radiation detections twice before, on June 10th and June 22nd.

This most recent Alert was triggered by a detection of over 100 CPM (Counts per Minute) for a sustained period of almost 15 minutes, followed by lower, yet elevated radiation levels for another half hour, making this the longest detection period yet for the Kauai station (clear sky this time – no rain). Background radiation for that station approximates 37 CPM, so these sustained levels were 2 to 3 times normal. Again, our best judgment is that the source of this radiation is probably Fukushima, perhaps from recent “releases” – we will try to correlate.

http://hawaiinewsdaily.com/2011/07/kauai-station-suspects-new-traces-of-fukushima-radiation/

 

[Caniche]

Cook em Dano

 

[RealWing]

If memory serves, the Besse Davis reactor vessel had the head almost corroded through, as no one asked where the copious rust in the water was coming from. Is there an industry mechanism to help bring such generic problems to the foreground?

The Davis Besse reactor vessel corrosion event was another significant wake-up-call for the whole industry. One or more long standing reactor coolant system leaks resulted in boric acid completely eating through ~6.5" of the vessel pressure boundary. All the was preventing a Loss of Coolant Acident was the thin S/S liner inside the vessel.

So - what are the "industry mechanisms to help bring such generic issues to the foreground"??

First - what failed?
1. The utility who has primary responsibility for the safety of the plant - failed to act on clear evidence of a leak. This included all levels of management as well as their internal oversight group
2. The regulator (NRC) failed to adequately communicate indications of a leak and assess the safety consequences
3. The industry oversight organization (INPO) failed to adequately assess the safety culture and outage programs in the utility.

In my view - a failure of the whole industry.

Like NUCENG - who knows the US industry very well, I can only comment with some knowledge on the Canadian industry. I know that this event had a significant effect on me personally because we, as nuclear plant managers must always keep a strong questionning attitude and strive to never become complacent. We do this by having a relentless focus on safety and by learning from other's mistakes. This was a major learning.
This event had many parallel's to the Columbia and Challenger events where management became complacent about O-ring leakages and foam detachments. The issue eventually faded into the background because of a poor management safety culture.
Even though Canadian reactors do not have a reactor pressure vessel or boric acid, this event resulted in an in-depth review of our safety culture as well as ensuring there are no "hidden" long term safety issues lurking in the plants.

My $0.02.

 

[robinson]

Big new crane on the live cam

http://www.tepco.co.jp/nu/f1-np/camera/index-j.html

 

[Joe Neubarth]

It may be too early for Tepco to even know exactly what went wrong and when. It does seem obvious that even a 30 meter wall wouldn't have prevented the immense pressure to the intake/outflow areas, the pipes that actually have to be directly connected to the ocean for cooling.

The turbine rooms and other areas may still have failed even if somehow they had a wall high enough to stop the ocean. From careful observation of the tsunami waves, it isn't just a matter of stopping the waves. The intakes have to be connected to the ocean. A wall would have stopped the damage to the buildings, but not to the intakes and where they connect to.

Loss of cooling may still have happened, both to the diesels and the reactors. It's an issue that probably wasn't planned for at all.

An increase in pressure to the intake and discharge points would have no effect on the operation of the Nuclear Reactor Plant for any short term interval...

 

[joewein]

I have never seen this mentioned, but may have missed if it was discussed early in the thread: Unit 3 had the biggest explosion of the three blocks that blew their tops, but when you look at shots of the unit 3 building, you can see that the truck bay, a tunnel-like entrance on the west side is largely intact. In unit 4, the walls of the truck bay are cracked and have almost blown away (probably only held by some reinforcement bars inside the concrete).

See for example on these Cryptome pictures:
http://cryptome.org/eyeball/daiichi-npp15/daiichi-photos15.htm

This suggests that hydrogen filled the ground floor (1F) of unit 4, but perhaps not unit 3.

 

[joewein]

Units 5 and 6 survived because one of the diesels at unit 6 was air cooled, so losing the sea water pumps didn't kill it. Other than that single diesel, units 5 and 6 still depend on either the grid or truck-mounted generators. I have not heard anything about moves to replace the dead diesels.

That has in fact already happened, I missed the news. Two new emergency diesels were installed and tested in unit 5 on June 27/28, mentioned towards the end of this document:
http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110629_02-e.pdf

As a result, units 5 and 6 should now have 3 EDGs between them. No word on whether the replacement units are water-cooled or air-cooled...

 

[tsutsuji]

http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110706e11.pdf is a 6 July update of the "storing and treatment of accumulated water including highly concentrated
radioactive materials at Fukushima Daiichi Nuclear Power Station". You can compare it with the first release http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110629e13.pdf published on 29 June.

http://www.jiji.com/jc/c?g=soc_30&k=2011070600860 from 29 June to 5 July 6380 tons have been produced from the 8400 capacity. This gives a 76% utilization rate, which is an improvement from the 55% rate a week earlier. The 96,980 ton accumulated in the plant on 5 June is 1830 ton less than at the end of June. Tepco initially planned to achieve an 80% utilization rate by 5 July, and a 90% rate henceforth. Instead, it is now planning an 80% rate by the end of July and 90% from August. This could cause delay to the goal of treating 200,000 tons within this year. The Areva system has already produced 109 tons of highly radioactive sludge, which is more than planned. Tepco is studying the possibility to undertake purification again with the top layer in order to reduce the volume of the sludge.

http://www.jiji.com/jc/c?g=soc_30&k=2011070700396 In a reply to Yukishige Okubo at the Upper House Budget Committee on 7 July, minister Goshi Hosono said there was a plan to introduce Japanese technology led by Toshiba in August to supplement the French/US, Areva/Kurion technology currently used at Fukushima Daiichi. He also insisted that the current facility was a temporary one, while a permanent facility using Japanese technology was being studied in combination with the temporary one.

http://www.tepco.co.jp/nu/fukushima-np/images/handouts_110707_03-j.pdf (not yet translated into English) the Decontamination Factor at the Kurion facility has greatly improved. As a result the radiation at the end of the Areva facility is below the detection limit for cesium.

http://www.jiji.com/jc/c?g=soc_30&k=2011070500852 In order to reduce worker exposure, flushing with low contaminated water has been performed since some time ago before replacing the adsorption towers at the Kurion facility, which is done using a crane. To further reduce worker exposure, what is planned is to change the policy to change 2~4 towers every day into 4 towers or so every other day. This has already been tried on 5 July with the replacement of 4 towers at the same time.

http://www.nikkei.com/news/category...3E2E2E2E2E2E2;at=DGXZZO0195165008122009000000 0.13 Bq/cm³ of Cs-134 and Cs-137 is detected again in ground water South East of the Process Main Building, after a number of days below the detection limit. This is thought to be either a consequence of the rain or of moving debris nearby.

http://japanfocus.org/-Sakai-Yasuyuki/3546 (English article) Sakai Yasuyuki, Japan’s Decline as a Robotics Superpower: Lessons From Fukushima, The Asia-Pacific Journal, Volume 9, Issue 24, No. 2, June 13, 2011.

 

[tsutsuji]

Fukushima One's first four reactors were just one tsunami away from destruction from the first day they put number One in operation about 40 years ago.

Consider this:

1. When they lost one Utility Power Line leading to the plant, there was no backup source of commercial electricity. (Was this the case for 40 years and nobody realized what a serious error it was in site design?)

Tepco has always said that there were 6 or 7 lines : see http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110516e17.pdf which is one of the attachments from the 16 May press release on the damage of electric facilities ( http://www.tepco.co.jp/en/press/corp-com/release/11051613-e.html ). If this is what you mean, could you explain your view that losing only one line was enough to cause a black out of the whole plant ?

By the way, there is a fresh new press release concerning the reliability of the power supply to the neighbouring Fukushima Daini power plant published today : http://www.tepco.co.jp/cc/press/11070704-j.html (not yet translated into English).

 

[joewein]

http://en.wikipedia.org/wiki/Fukushima_Daiichi_Nuclear_Power_Plant#Electrical_connections" also lists multiple grid connections (pre-tsunami):

Electrical connections

The Fukushima Daiichi plant is connected to the power grid by four lines, the 500 kV Futaba Line (双葉線), the two 275 kV Ōkuma Lines (大熊線) and the 66 kV Yonomori line (夜の森線) to the Shin-Fukushima (New Fukushima) substation.

The Shin-Fukushima substation also connects to the Fukushima Daini plant by the Tomioka Line (富岡線). Its major connection to the north is the Iwaki Line (いわき幹線), which is owned by Tohoku Electric Power. It has two connections to the south-west that connect it to the Shin-Iwaki substation (新いわき).

TEPCO seems to have managed to lower radioactivity levels in one corner of unit 3 to 1/3-1/4 of http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110703_01-e.pdf" in preparation for nitrogen injection, after robot-cleaning and laying steel plates for shielding:
http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110707_02-e.pdf

Units 1 and 2 are already receiving N₂ injections.

 

[robinson]

An increase in pressure to the intake and discharge points would have no effect on the operation of the Nuclear Reactor Plant for any short term interval...

I don't know. If the outflow from the turbine room, the hot water discharge, is designed to operate at atmospheric pressure, and suddenly the water being pumped out is facing water at a depth of 20 meters, that's a lot of pressure to be forcing water against. In fact the pressure of the water forcing itself in when the pumps want the water to be going out, that might damage the pumps. It's the sort of thing that could be tested of course.

There are a lot of unknowns involved. Did anyone ever do any testing to see what would happen?

If the force of the water was enough to rip strong metal objects from their moorings, smash sturdy objects and in general just destroy, I can see it doing some serious damage to a pump motor trying to pump 10,000 gallons a second against the flow.

 

[Joe Neubarth]

I don't know. If the outflow from the turbine room, the hot water discharge, is designed to operate at atmospheric pressure, and suddenly the water being pumped out is facing water at a depth of 20 meters, that's a lot of pressure to be forcing water against. In fact the pressure of the water forcing itself in when the pumps want the water to be going out, that might damage the pumps. It's the sort of thing that could be tested of course.

There are a lot of unknowns involved. Did anyone ever do any testing to see what would happen?

If the force of the water was enough to rip strong metal objects from their moorings, smash sturdy objects and in general just destroy, I can see it doing some serious damage to a pump motor trying to pump 10,000 gallons a second against the flow.

Robinson, there is video footage of the Tsunami striking the plant complex. You can see the 4.2 meter swell out in the harbor rolling in. You can see the Run Up effects as it reaches shallower water. You can see the Big Splash at it hits the quay wall and water shoots up thirty or more meters. (Now, that was impressive!) You see that happen and you run like 'ell up the nearest hill. There are many reports of people having done just that at the site. A couple of technicians inside the turbine room complex were killed and mutilated by the wave as they did not have the presence of mind to get out of that area before the wave struck. As you can see along the coast in that immediate area, there are sea cliffs. Like any wave the water runs up against the cliff and then runs back out as a wave going in the opposite direction. There is video and still photos of the wave washing back out from Fukushima just a few seconds later. The sea water injection pumps would not have been effected by that momentary surge and increase in pressure at the inlet. They might have sped up a little, but the amount of sea water coolant running through the condenser tubing probably would not have increased that much simply because of capacity limitation. Any effluent flow might have been held up by the increase in pressure, but being of short duration it was not an issue of major importance considering that most of the Emergency Diesel Generators were under water and their controlling panels were water logged and inoperable

 

[Joe Neubarth]

Tepco has always said that there were 6 or 7 lines : see http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110516e17.pdf which is one of the attachments from the 16 May press release on the damage of electric facilities ( http://www.tepco.co.jp/en/press/corp-com/release/11051613-e.html ). If this is what you mean, could you explain your view that losing only one line was enough to cause a black out of the whole plant ?

.

TEPCO admitted that they had one electrical tower go down on the mainland.

When they lost that one tower, they lost all commercial power to the Fukushima Plant. That is the reason why right after the earthquake all of the Emergency Diesel Generators that were operable were running when the tsunami hit forty some minutes later.

A loss of electrical power to a nuclear plant is considered to be the Worst Case Scenario. Because of that, Nuclear Plants are designed to have multiple redundancy in commercial power sources. TEPCO lost one source (One Line Source) and the plants were in the dark. THERE IS NO ABSOLUTELY EXCUSE FOR THAT!

When the emergency diesel generators were submerged (again a serious site engineering design flaw), the reactors were left with no power for the coolant pumps and the meltdowns started within a couple of hours and were quite well advanced within 24 hours.

 

[nikkkom]

I don't know. If the outflow from the turbine room, the hot water discharge, is designed to operate at atmospheric pressure

No. Reactors were already scrammed ~40 minutes ago when tsunami arrived. IOW, turbine was not working, and even if F1 used regular turbine hall condensers for post-scram cooling, the required sea water flow was about fifty times smaller than one needed at 100% rated power operation.

 

[robinson]

The same problem could have effected the cooling pumps for the EDGs

 

[Atomfritz]

Is there an industry mechanism to help bring such generic problems to the foreground?

At least in Germany, this is not the case. Here the operating companies try to hide all that could undermine trust in the nuclear industry.

Here is just one such example:
Biblis NPP operators in the course of ten years repeatedly made dangerous maneuvers not covered by the procedure manuals to avoid shutdowns of the reactor. With these maneuvers (venting primary circuit coolant to outside the containment, into the machine building) they risked uncontrollable LOCAs.
This incident was not told to german nuclear authorities until almost half a year later, and then the violations were omitted in the report.
German government and public media got alarmed by an article in "Nucleonics Week" that made them start investigations and so uncover the coverup.

Technical description of this "top-level" incident: http://www.oecd-nea.org/nsd/docs/1990/csni90-180.pdf
Description of the cover up by the NPP operators in: http://www.greenpeace.org/raw/content/international/press/reports/the-greenpeace-book-of-the-nuc.pdf (Sorry for this source, it was the only one in English. All other detailed articles about this I found are in German)

It galls me to the core that this accident could have been prevented. I am trying hard not to let my anger and embarrassment prevent me from seeing that opponents like Arnie may have some valid points.

Maybe even stupid people like me sometimes have valid points.
And yes, it's so sad that they now build a higher tsunami wall... only after that lovely NPP has been destroyed.

This suggests that hydrogen filled the ground floor (1F) of unit 4, but perhaps not unit 3.

I always thought that in normal operation (#1-#3) the transport shaft zone is sealed by a sort of door.
Maybe this seal was open in RB4 due to core shroud material transport and other maintenance, so the damage?

http://en.wikipedia.org/wiki/Fukushima_Daiichi_Nuclear_Power_Plant#Electrical_connections" also lists multiple grid connections (pre-tsunami)

If this is what you mean, could you explain your view that losing only one line was enough to cause a black out of the whole plant ?

On Google Earth images I can see at least three grid connections (rough directions: SW, SWW, W). Maybe some masts carry more than one connection, ripping them all open when masts fall? There were reports of several fallen masts.
If six or even seven grid connections fail at once this shows clearly that complete station blackouts may be not that rare and hypothetical as postulated. Especially if all grid connections lead to the same grid node station, as Wikipedia article could be interpreted. This is no real redundancy to rely upon imho.

If the force of the water was enough to rip strong metal objects from their moorings, smash sturdy objects and in general just destroy, I can see it doing some serious damage to a pump motor trying to pump 10,000 gallons a second against the flow.

I think they will have backflow prevention, though designed only for 5.7m tsunami.
Some kind of valve (in German: "Rückschlagklappe", don't know in english) that is common in flood areas, like those that avoid the drain flowing over into your basement at heavy rains.

 

[joewein]

TEPCO admitted that they had one electrical tower go down on the mainland.

When they lost that one tower, they lost all commercial power to the Fukushima Plant. That is the reason why right after the earthquake all of the Emergency Diesel Generators that were operable were running when the tsunami hit forty some minutes later.

But according to this diagram there were multiple, simultaneous points of failure in the grid connections:
http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110516e17.pdf

From that diagram, it doesn't look like it was a single tower going down that triggered it all.

 

[zapperzero]

But according to this diagram there were multiple, simultaneous points of failure in the grid connections:
http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110516e17.pdf

From that diagram, it doesn't look like it was a single tower going down that triggered it all.

Yet another example of fake redundancy - a common failure mode exists for the assumed redundant elements, and moreover a common-cause failure is possible. So it happens, naturally, sooner or later.

 

[tsutsuji]

The collapse of Yonomori tower No. 27 is mentioned on http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110516e17.pdf : it is responsible for the collapse of two lines because both lines are using the same towers. Yet this event does not account for the failure of the other 5 lines.

As I wrote in June ( https://www.physicsforums.com/showpost.php?p=3356083&postcount=9758 ) I think the Japanese government's view expressed in the report to IAEA that more should have been done to ensure that the power lines are able to withstand earthquakes is interesting. I would be glad to learn more about the feasibility and the cost of earthquake resistant power lines, which sounds to my ears better than multiple, redundant lines, if they are not designed to withstand earthquakes in the first place. Conversely, if they were thought and designed to withstand earthquakes, an investigation should tell what was wrong in that design.

Also I was wondering whether it would not be possible to use the high voltage power lines backwards to supply power back to the plant in case of emergency if they are still safe while all other lines have collapsed.

 

[Atomfritz]

But according to this diagram there were multiple, simultaneous points of failure in the grid connections:
http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110516e17.pdf

From that diagram, it doesn't look like it was a single tower going down that triggered it all.

Yet another example of fake redundancy - a common failure mode exists for the assumed redundant elements, and moreover a common-cause failure is possible. So it happens, naturally, sooner or later.

Thanks for the link.
If I interpret the pdf correctly then each reactor has one 275kV line.
Each mast carries two lines. So mast cave-ins, mast collapses, shorts due wires tied together always put out out two reactors.
The 66kV Tohoku line (maybe Earth cable) backup also was damaged.
The only functional lines (Okuma 1+2) could not be utilized because line switch and circuit breaker damage on unit 1/2 switchyard.

So sad that there has been no redundancy switch so that unit 3/4 switchyard could have been supplied via Okuma 1 line, the only one whose connection to the Daiichi plant was not broken.
If it had, at least reactors 3+4 possibly could have been saved.

 

[Bandit127]

Quite a substantial piece of framework to hang the plastic curtains from. It is good to see that they are having a trial run too.

Trial fitting of the cover for Unit 1, Fukushima Daiichi Nuclear Power Station at Onahama port
[URL]http://www.tepco.co.jp/en/news/110311/images/110707_1.jpg

[/URL]

 

[Luca Bevil]

Also I was wondering whether it would not be possible to use the high voltage power lines backwards to supply power back to the plant in case of emergency if they are still safe while all other lines have collapsed.

What do you mean exactly ?