Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[PietKuip]

The expertise deployed on this forum to understand the processes which reduced four multi billion dollar reactors to steaming scrap is laudable.
For an outside observer, it would be wonderful if this expertise were also employed looking forward, to help evaluate and understand the challenges and risks posed by the clean up plan.
For instance, Areva is scheduled to have a water processing plant built by the end of June that will process 1200 tons of water/day. There are nearly 70,000 tons currently in the facility, increasing at 500tons/day, so there will be 100,000 tons by the time the plant is operational.
The plant will start to whittle down the flood at about 700 tons/day net once it starts, so it will take 150 days to drain the facility, if all goes well.
That says the cleanup will not begin until very late this year at the earliest.
Is this a plausible schedule? How does it tie into the TEPCO indication that the immediate crisis should be stabilized within 9 months? What are the risks that should be of most concern?

some more here :

In a process called co-precipitation, the water will be treated with chemicals that cause radioactive material to settle out.
...
By contrast, a floating treatment facility built by Japan and Russia for water with low-level radioactive contamination has a capacity of only 7,000 tons a year.
http://e.nikkei.com/e/fr/tnks/Nni20110419D19JFA25.htm

With all respect for Areva and their experience with fuel reprocessing and without being a chemist myself, I think this is way too optimistic about the future. It would take time even to build a plant for decontaminating fresh water. Maybe that can be done within a few months.

But how to handle cesium in salt water? Does co-precipatation using nickel ferrocyanide work in brine? Won't most of the precipatate contain other stuff than cesium? Are there any radiochemists here?

 

[MadderDoc]

So the damage TCups pointed at at the turbine building facing Unit 4 was already there three minutes after Unit 3 exploded?

11:01 JST / March 14th - #3 explosion:

11:04 JST / March 14th - Sat images show extensive damage to building #3 AND two damaged spots at the turbine building facing #4.

Yes. The spots must be from something spewed out by #3, however I am not sure how much damage those particular spots would represent. The fall-out of #3 was a bit like when you sift grain in the wind, the lightest stuf blows away, the medium dense objects ends like a fan on the ground in the wind direction, and the densest stuf ends fortunately -- or unfortunately in the case of #3 -- right back in the basket.

6:00 JST / March 15th - first explosion at #4 ejects two wall panels and damages #3 further (according to TEPCO)

Right. I think the explosion in #4 on the 15th caused very little damage to #3. I've attached a photo taken from the distance one and half hour after the explosion of #3, at 12:40 JST / March 14th. It looks to me in the large structures of it, to be then as it is now.

9:40 JST / March 15th - fire in SFP at #4<..>

Yes, but that's only part of it. The 15th and 16th were dreadful days at #4, really horrible, one can easily imagine. You can see the hourly webcams from those days at:
http://www.gyldengrisgaard.dk/tepcowebcam/

 

[PietKuip]

http://www3.nhk.or.jp/daily/english/20_30.html

In the video, NHK says that radioactivity increases in the basements of units 5 and 6. The contaminated water is spreading all over the place.

 

[rowmag]

Following up to myself: From page number 8 (PDF page 10) of http://www.tepco.co.jp/nu/f1-np/pres...a/bi8a08-j.pdf, they report that a suspected leaking fuel assembly in the core had been identified during operation in 2007, I gather by sliding different sets of control rods in and out with the plant running at reduced output until they managed to get the leaked radioactive gas to stop being produced. They isolated that assembly by inserting the control rods around it, and went back up to full power until the scheduled maintenance/inspection period in 2008. When they eventually pulled the suspect assembly out, it showed no visible signs of damage, but they treated it as a spent fuel assembly and did not re-use it.

This is pretty standard in the industry with respect to BWR failures. An operating failure can be found by inserting a control blade adjacent to the failure. During the process, the off-gas (Xe-133, Kr-85m, Kr-87, Kr-88, Xe-135/135m, Xe-138) activity is monitored for changes. A reduction in activity indicates a possible leaking fuel assembly.

The process has been called 'flux-tilting'. The process was codified about 18 years ago and is now generally called power suppression testing (PST). Once the failure is located the local control blade is inserted, and others maybe inserted as well in order to reduce the power in the failed assembly. Most utilities prefer to shutdown the reactor in a mid-cycle outage to remove the failed assembly.

It is policy not to return a failed assembly or one suspected as failed to the core.

Meanwhile the industry has been working to achieve zero failures in LWR fuel.

I thought it sounded pretty clever.

Thanks for the info.

 

[Joe Neubarth]

where did you see that , I must admit i no longer watch nhk 247 (especially since they resume regular program)

That is amazing! Something so very obvious as the data from Reactor Two and nobody appears to understand what is happening.

Reactor Two is at Atmospheric pressure. Reactor Two has tons of water being poured into it. Reactor Two is NOT venting steam.

In fact the top of the reactor is considerably higher than the temperature of steam. Steam can only go to a higher temperature if it is under pressure, which it is not in this case. Reactor two is venting hot radioactive gases.

So,I ask my question in the morning that I asked at night. Does anybody have any theories as to how the water is missing the core which has to be out of containment at this time. Are we going to see a continued release of hot radioactive gases until the BLOB has diluted itself, or will they continue for a generation or so?

 

[jlduh]

Hi, back again after more than 2 weeks without internet, try to sum up the informations i missed in between.

Sorry if this has been already posted but I wanted to mention that this page on the messy Tepco website has a bunch of videos and pictures that they released, you have to download them sometimes which is not very friendly but anyway, i think there may be some interesting material to analyze.

http://www.tepco.co.jp/en/news/110311/index-e.html

I let you go through the material there, some was not available before I left beginning of April.

I put this interesting picture of the level of water at the plant during the tsunami, very impressive:

http://www.tepco.co.jp/en/news/110311/images/110412_2f_tsunami_6.jpg

The same point without the tsunami water:
http://www.tepco.co.jp/en/news/110311/images/110422_2f_tsunami_7.jpgOf interest also this part of the page with videos from remote T Hawk helicopter (17 April)
Movies taken from T-Hawk, Reactor Building, Unit 1, 3,4 Fukushima Daiichi Nuclear Power Station

Unit 1 ,3,4(1/3)
(Video on April 15, 2011)
http://www.tepco.co.jp/en/news/110311/images/110415_1f_1.zip

Unit 1 ,3,4(2/3)
(Video on April 15, 2011)
http://www.tepco.co.jp/en/news/110311/images/110415_1f_2.zipUnit 1 ,3,4(3/3)
(Video on April 15, 2011)
http://www.tepco.co.jp/en/news/110311/images/110415_1f_3.zip

 

[M. Bachmeier]

Does anyone know about the use of hydrogen peroxide in BWR's during shutdown. I'm interested in storage (in or out of reactor building), added concentrations in reactor and SFP.

For example:

"Appropriate biocides (hydrogen peroxide) at concentrations up to 1000 ppm were added (to the pool water) to control biofouling."

From: http://www-pub.iaea.org/MTCD/publications/PDF/te_0944_scr.pdf

Also anyone with knowledge about what chemicals might be stored/used (in or near reactor) during BWR shutdown that might interact with hydrogen peroxide (powerful oxidizer).

I have a feeling that hydrogen peroxide may have played a role in the explosion at the Fukushima Diiachi #4 reactor building.

Also, @Astronuc: were you making reference to hydrogen peroxide in post: https://www.physicsforums.com/showpost.php?p=3217855&postcount=1968 in response to my earlier inquiry?

I'm wondering if someone can either help put this line on inquiry to bed, or point me in the right direction for additional research.

 

[rowmag]

I put this interesting picture of the level of water at the plant during the tsunami, very impressive:

http://www.tepco.co.jp/en/news/110311/images/110412_2f_tsunami_6.jpg

The same point without the tsunami water:
http://www.tepco.co.jp/en/news/110311/images/110422_2f_tsunami_7.jpg

Note that these are pictures taken at Fukushima Daini power plant, not Daiichi. Daini is 10 km south of Daiichi, and has achieved stable cold shutdown at all their reactors.

Pretty impressive, though, agreed.

 

[Samy24]

That is amazing! Something so very obvious as the data from Reactor Two and nobody appears to understand what is happening.

Reactor Two is at Atmospheric pressure. Reactor Two has tons of water being poured into it. Reactor Two is NOT venting steam.

In fact the top of the reactor is considerably higher than the temperature of steam. Steam can only go to a higher temperature if it is under pressure, which it is not in this case. Reactor two is venting hot radioactive gases.

So,I ask my question in the morning that I asked at night. Does anybody have any theories as to how the water is missing the core which has to be out of containment at this time. Are we going to see a continued release of hot radioactive gases until the BLOB has diluted itself, or will they continue for a generation or so?

Maybe Fred (and I) want to know where you have picked this: "Reactor Two is NOT venting steam"

 

[Joe Neubarth]

Maybe Fred (and I) want to know where you have picked this: "Reactor Two is NOT venting steam"

Have you seen any hot billowing clouds out of Reactor Two in the past week? Note that the temperature at the top of the reactor is above that of steam.

 

[Dmytry]

That is amazing! Something so very obvious as the data from Reactor Two and nobody appears to understand what is happening.

Reactor Two is at Atmospheric pressure. Reactor Two has tons of water being poured into it. Reactor Two is NOT venting steam.

In fact the top of the reactor is considerably higher than the temperature of steam. Steam can only go to a higher temperature if it is under pressure, which it is not in this case. Reactor two is venting hot radioactive gases.

So,I ask my question in the morning that I asked at night. Does anybody have any theories as to how the water is missing the core which has to be out of containment at this time. Are we going to see a continued release of hot radioactive gases until the BLOB has diluted itself, or will they continue for a generation or so?

spotted it myself ages ago, it was also the case for #1 that steam was hotter than it could be if the fuel is covered (and it was under pressure).
http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/plots/cur/plot-un1-full.png

http://www.engineeringtoolbox.com/saturated-steam-properties-d_457.html

Actually, steam can be at higher temperature when it is not under pressure. What it can't do, it can't get to a higher temperature without being heated by something hotter still, that is not covered by water. Water cannot be at higher temperature if it is not under pressure.

 

[rowmag]

Rowmag and Tcups, can I please take a moment to say THANK YOU! Thank you for these two absolutely pure rational logical conclusions. This thread is becoming so wildly speculative, I am almost amazed people haven't come out and said these explosions were an inside job...

Don't know about you, TCups, but I have been called many things, but rational/logical is not one of them. A first!

 

[Samy24]

Have you seen any hot billowing clouds out of Reactor Two in the past week? Note that the temperature at the top of the reactor is above that of steam.

At the TEPCO (lowres) webcam I can not see any steam since the last two days
http://www.gyldengrisgaard.dk/tepcowebcam/tepweb20110420.html"

So does that mean that reactor 1-3 and all the SFP's are run dry?

 

[clancy688]

So does that mean that reactor 1-3 and all the SFP's are run dry?

Or they are sufficiently cooled -> water isn't boiling, no steam

 

[Jorge Stolfi]

So, no surprise, we see steam coming from that area...But soon that steam dissipated. .

Also remember that the SkyGlobe pic is taken from orbit, so it will include any clouds that happened to be between the plant and the satellite, even in the statosphere. Not so for wbcam and airplane pics.

 

[jlduh]

Originally Posted by jlduh
I put this interesting picture of the level of water at the plant during the tsunami, very impressive:

http://www.tepco.co.jp/en/news/11031..._tsunami_6.jpg

The same point without the tsunami water:
http://www.tepco.co.jp/en/news/11031..._tsunami_7.jpgNote that these are pictures taken at Fukushima Daini power plant, not Daiichi. Daini is 10 km south of Daiichi, and has achieved stable cold shutdown at all their reactors.

Pretty impressive, though, agreed.

Sorry, i didn't give this precision but you are right, this is Daini. But really we didn't talked a lot about this second plant as it achieved cold shutdown but looking at this picture anyone can see that we've been pretty close to a second disaster! I will be interested to see what can explain the difference concerning the consequences between the two plants: technical differences (positionning of the diesel generators?) or... luck?

After the fact, that's really a scary picture to me.

 

[Samy24]

Or they are sufficiently cooled -> water isn't boiling, no steam

That was the thing I want to point at. But this would mean that TEPCO reports wrong data readings or the instruments are all gone crap.

 

[clancy688]

I will be interested to see what can explain the difference concerning the consequences between the two plants: technical differences (positionning of the diesel generators?) or... luck?

I think, Daiichi 1-4 are at 10 metres elevation. 5-6 and Daini 1-4 are at 14 or 15 metres elevation.

The tsunami had a height of 14-15 metres. So there's your explanation.

 

[jlduh]

Can somebody explain me how to interpret the fact that since several weeks know, i see written in the reports (Tepco, AIEA) that the fuel rods are around half length uncovered -so outside of water- in reactors 1 to 3?

I mean, do i have to understand that:

1) they are still "uncovered" half length,
or
2) that they have melted this length and possibly relocate at the bottom, in the water?

If 1), how can they be uncovered and still not melted?

Thanks for your precisions on that.

 

[clancy688]

If 1), how can they be uncovered and still not melted?

Thanks for your precisions on that.

You missed 3) sensor malfunction.

 

[elektrownik]

Who want explain why core temperature (empty core as tepco say) is 11C bigger than SFP ?
http://www.mod.go.jp/j/approach/defense/saigai/tohokuoki/kanren/230420.pdf

 

[jlduh]

clancy 688: that may be A difference (I have to confirm your elevation data) but still, the picture i posted shows that there has also been a heavy flooding of the platform at the Daini plant (which i didn't really know about to tell you the truth). At the Daichi plant, if i remember well, the diesel generators were at ground level (or even below ground level maybe, in the basement of the turbine building? Don't remember...). So my point is: ok the tsunami has been worse at Daichi than at daini because some difference of height of the platform but still, did the EDG at Daini went under water, or close to go under water too?

http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110409e9.pdf

 

[default.user]

Once again in german:

1.Mit welcher Sicherheit kann man eine neuerliche Kritikalität ausschließen?

http://www.gyldengrisgaard.dk/tepcowebcam/20110417190100.jpg

Es gibt viele solcher Bilder. Das Bild vom 15.04.2011 - 19:00 Uhr ist nicht auffindbar.

2.Kann man eine Kernschmelze ohne Problem mit Wasser kühlen?
3.Welche Umstände führen zu einer Wasserdampfexplosion?

Vielen Dank

 

[clancy688]

ok the tsunami has been worse at Daichi than at daini because some difference of height of the platform but still, did the EDG at Daini went under water, or close to go under water too?

I have currently no sources (I'm in class right now), but as far as I remember, Daichi 1-4 have been flooded 5 metres deep and Daiichi 5-6 and Daini 1-4 only 1 metre deep.

 

[Joe Neubarth]

I think, Daiichi 1-4 are at 10 metres elevation. 5-6 and Daini 1-4 are at 14 or 15 metres elevation.

The tsunami had a height of 14-15 metres. So there's your explanation.

To be precise, the tsunami was only about four meters. The run up from the tsunami reaching land was in excess of 14 meters.

San Onofre in San Diego County is not designed to withstand a run up in excess of 9 meters, which can be caused by a tsunami half that height. And yet, San Onofre is still allowed to operate with over 3 million people living within 50 miles of the site.

 

[tsutsuji]

Trying to find basic information on Areva's water treatment facilities :

The used fuel treatment station at La Hague also manages liquid wastes.

In this facility at La Hague, AREVA treat the liquid releases.
http://www.areva.com/EN/operations-1182/waste-management-at-areva-la-hague.html

 

[Joe Neubarth]

I have currently no sources (I'm in class right now), but as far as I remember, Daichi 1-4 have been flooded 5 metres deep and Daiichi 5-6 and Daini 1-4 only 1 metre deep.

I do not remember reading of any wave breaking into the building housing the Diesel generators like it did at Daichi. In the turbine buildings at Daichi, men were killed (severely lacerated) by the wave action inside the building.

 

[jlduh]

I do not remember reading of any wave breaking into the building housing the Diesel generators like it did at Daichi. In the turbine buildings at Daichi, men were killed (severely lacerated) by the wave action inside the building.

So your point is be that the difference would be that at Daini the wave didn't break the walls or doors of the building in which the generators were which was not the case at Daichi?

Can someone confirm with a good source document where were exactly located the EDG at Daichi and Daini? I'm not only talking about their position from the top view (at daichi they are in the east north side of each reactor, in the turbine building) but also their elevation location relative to platform level: at ground level or BELOW ground level?

 

[tsutsuji]

So my point is: ok the tsunami has been worse at Daichi than at daini because some difference of height of the platform but still, did the EDG at Daini went under water, or close to go under water too?

http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110409e9.pdf

The following 2011/04/07 Asahi article was posted earlier in this thread :

The emergency generators at the No. 2 [that is Daini] plant were in buildings housing the reactor cores. Because the reactor buildings are much more airtight, the generators at the No. 2 [Daini] plant continued to function after the tsunami struck.
http://www.asahi.com/english/TKY201104060126.html

 

[default.user]

Das kann man nicht sicher ausschließen. Auch Physiker sind sich da nicht einig.

One can not rule out safely. Physicists are not as united.
Eine vollständige und spontane Kernschmelze kann wohl nicht effektiv mit Wasser gekühlt werden. Ob und wie eine Kernschmelze in Fukushima abläuft, weiß man jedoch nicht.

A complete and spontaneous meltdown may well not be effectively cooled with water. Whether and how a meltdown going on in Fukushima, we know not.
Wenn der sehr hoch erhitzte Kern plötzlich auf eine größere Menge Wasser trifft könnte es zu einer Wasserdampfexplosion kommen.

If the very-high temperature nuclear suddenly take on a greater amount of water it could cause a steam explosion.

Vielen Dank.

Ich habe mich gefragt, ob es Tepco überhaupt möglich ist, die Reaktoren direkt zu kühlen, oder ob man die Druckbehälter via containment kühlt. Eine sehr wichtige Frage.

Also, entweder die Kerne sind geschmolzen und sehr heiß als nicht direkt kühlbar oder sie sind ok und direkt kühlbar.

Abgesehen davon, dass ich mir nur schwer vorstellen kann, dass irgendwelche Hochdruck-Rohrsysteme intakt sind.

 

[|Fred]

That is amazing! Something so very obvious as the data from Reactor Two and nobody appears to understand what is happening.
Reactor Two is NOT venting steam.

In fact the top of the reactor is considerably higher than the temperature of steam. Steam can only go to a higher temperature if it is under pressure, which it is not in this case. Reactor two is venting hot radioactive gases.

So,I ask my question in the morning that I asked at night. Does anybody have any theories as to how the water is missing the core which has to be out of containment at this time. Are we going to see a continued release of hot radioactive gases until the BLOB has diluted itself, or will they continue for a generation or so?

Sorry, You'll probably get amassed as I don't get it, you are saying that visually looks like steam/ exiting unit 2 is not steam but Gaz ? Because RCV is not pressurized and the top of the reactor is to hot ?
What do you think happens when the watter enter the hot RCV ? or does it enter at all?


edit: ah... no you are saying that there is no longer steam exiting unit 2... oh well all I was asking is when has it been reported.. nothing more, nothing less

 

[jlduh]

more than 67 000 tons of contaminated water accumulated at the Daichi plant...

http://www3.nhk.or.jp/daily/english/20_30.html

And i don't see how the accumulation of water would stop in the next month as long as they will have to continue to keep cooling down the stuff in open loop! A second ongoing flooding after the tsunami one...

What are the alternatives (if any exists)?

 

[clancy688]

Ich habe mich gefragt, ob es Tepco überhaupt möglich ist, die Reaktoren direkt zu kühlen, oder ob man die Druckbehälter via containment kühlt. Eine sehr wichtige Frage.

Scheinbar ist das noch nicht der Fall. Zumindest wurde in dem TEPCO-6-Monatsplan angegeben, dass in naher Zukunft die Containments der Reaktoren 1 und 3 mit Wasser geflutet werden. Was heißt, dass es jetzt noch nicht der Fall ist.

That's probably not the case. The recently announced TEPCO-6-month-plan stated, that they'll fill the containments of Units 1 and 3 with water in the near future, indicating that they're currently dry and unfilled.

 

[Rive]

Who want explain why core temperature (empty core as tepco say) is 11C bigger than SFP ?
http://www.mod.go.jp/j/approach/defense/saigai/tohokuoki/kanren/230420.pdf

We can't see the SFP directly, so the temperature what the senor see is some mixture of the temperature of the roof and the FHM. The SFP temperature of Unit 4 is close to the boiling point by the direct measurement (some sample were taken by the concrete pump truck along with a direct temperature measurement.)

 

[Joe Neubarth]

Scheinbar ist das noch] nicht der Fall. Zumindest wurde in dem TEPCO-6-Monatsplan angegeben, dass in naher Zukunft die Containments der Reaktoren 1 und 3 mit Wasser geflutet werden. Was heißt, dass es jetzt noch nicht der Fall ist.

There are too many unanswered questions and the Japanese are not in position to answer them.

 

[jlduh]

The emergency generators at the No. 2 [that is Daini] plant were in buildings housing the reactor cores. Because the reactor buildings are much more airtight, the generators at the No. 2 [Daini] plant continued to function after the tsunami struck.
http://www.asahi.com/english/TKY201104060126.html

Tanks tsutsuji, that looks to me a significant difference between the two if this is confirmed. I believe based on one drawing that i saw (but i don't find it again) that the EDG at Daichi were in fact below the ground level in the reactor buiding which is not intended to be waterproof of course... One can imagine the consequences in case of flooding. Pure stupidity. Putting them in the reactor building seems more intelligent, even if maybe they should have put them on the hills around the plant!

 

[Joe Neubarth]

Tanks tsutsuji, that looks to me a significant difference between the two if this is confirmed. I believe based on one drawing that i saw (but i don't find it again) that the EDG at Daichi were in fact below the ground level in the reactor buiding which is not intended to be waterproof of course... One can imagine the consequences in case of flooding. Pure stupidity.

Absolute pure stupidity. They did not design for the run up from a tsunami. Somebody gave the engineers a number for tsunami height, but it looks like they airheaded the engineering.

 

[tsutsuji]

To be precise, the tsunami was only about four meters. The run up from the tsunami reaching land was in excess of 14 meters.

San Onofre in San Diego County is not designed to withstand a run up in excess of 9 meters, which can be caused by a tsunami half that height. And yet, San Onofre is still allowed to operate with over 3 million people living within 50 miles of the site.

Do you have a source for the "about four meters" ?

Looking at the "predicted maximum level caused by tsunami O.P. 5.7 meter" caption leading via the blue arrow to the red dots just above the sea wall at http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110409e9.pdf , I am wondering how tall that sea wall is. If the sea wall is 5.7 m high and the tsunami only "about four meter" high, should not the nuclear plant have been safe then ?

I would be glad to read more basic science on this topic : how tsunami height and tsunami "run up" are related with each other and possibly modelized, and how sea walls are designed to ensure some predicted level of protection.

What is the meaning of the "O.P." acronym ?

 

[|Fred]

Ich habe mich gefragt, ob es Tepco überhaupt möglich ist, die Reaktoren direkt zu kühlen, oder ob man die Druckbehälter via containment kühlt. Eine sehr wichtige Frage.

he ask him self if tepco has to cool the core from the inside or if could be cooled from the outside (I think)

If I understand you right.. by design it is meant to be cooled from the inside of the RCV. In case of an accident cooling from the outside seems to be procedure because it can help a bit . is it a good solution ? that's debatable.

Ob ich Sie verstehe .. von Design ist gemeint, von der Innenseite des Reactor vessel gekühlt werden.Im Falle eines Unfalls Kühlung von außen scheint Verfahren. Es hilft .I st es eine gute Lösung? that's fraglich.

 

[tsutsuji]

Absolute pure stupidity. They did not design for the run up from a tsunami. Somebody gave the engineers a number for tsunami height, but it looks like they airheaded the engineering.

At least "Tsunami assessment for nuclear power plants in Japan" by M.Takao, TEPCO : http://www.jnes.go.jp/seismic-symposium10/presentationdata/3_sessionB/B-11.pdf (1st Kashiwazaki International Symposium on Seismic Safety of Nuclear Installations, November 2010), page 14, seemed confident in the 4.4 + 1.3 = 5.7 m calculation, whatever that might mean.

 

[clancy688]

At least "Tsunami assessment for nuclear power plants in Japan" by M.Takao, TEPCO : http://www.jnes.go.jp/seismic-sympos...sionB/B-11.pdf , page 14, seemed confident in the 4.4 + 1.3 = 5.7 m calculation, whatever that might mean.

Well, in case of Onagawa they didn't stick with those 5.7 metres but went far beyond. http://search.japantimes.co.jp/cgi-bin/nn20110408b3.html

 

[default.user]

Ich habe mich gefragt, ob es Tepco überhaupt möglich ist, die Reaktoren direkt zu kühlen, oder ob man die Druckbehälter via containment kühlt. Eine sehr wichtige Frage.

If I understand you right.. by design it is meant to be cooled from the inside of the RCV. In case of an accident cooling from the outside seems to be procedure because it can help a bit . is it a good solution ? that's debatable.

Ob ich Sie verstehe .. von Design ist gemeint, von der Innenseite des Reactor vessel gekühlt werden.Im Falle eines Unfalls Kühlung von außen scheint Verfahren. Es hilft .I st es eine gute Lösung? that's fraglich.

Das ist fraglich.

Es ist doch auch fraglich, ob man einen in Kernschmelze befindlichen Druckbehälter ohne Problem [Wasserdampfexplosion] direkt kühlen kann.

Wenn man nicht weiß, wie der Zustand der Kerne ist, so wird man doch sicher keine Fehler machen wollen.

About 130 minutes after the first malfunction, the top of the reactor core was exposed and the intense heat caused a reaction to occur between the steam forming in the reactor core and the Zircaloy nuclear fuel rod cladding, yielding zirconium dioxide, hydrogen, and additional heat

http://en.wikipedia.org/wiki/Three_Mile_Island_accident#Consequences_of_stuck_valve

Wie lange war die Kühlung in Daiichi unterbrochen?

 

[tsutsuji]

Well, in case of Onagawa they didn't stick with those 5.7 metres but went far beyond. http://search.japantimes.co.jp/cgi-bin/nn20110408b3.html

[At Onagawa] The recorded tsunami height of about 13 meters far exceeded the plant's anticipated maximum level of 9.1 meters, and wave marks were found at the edges of the plant, indicating the tsunami fell just short of reaching the main buildings, Tohoku Electric said.
http://search.japantimes.co.jp/cgi-bin/nn20110408b3.html

See also IAEA/JNES/NIED Seminar on Nuclear Disaster & General Disaster Management against Tsunami and Earthquake, Tokyo, December 2007, “Safety Assessment and Disaster Management for Tsunami Hazards at Onagawa Nuclear Power Plant”, Y. Matsumoto, (Tohoku Epco, Japan) : http://www.jnes.go.jp/content/000015486.pdf (in Japanese, but pictures , diagrams and mathematical formulas may provide some information even if you don't read Japanese)

In particular the diagram p.10 indicates that the ground floor's height is 14.8 m at Onagawa, which was perhaps enough for the 11 March tsunami at that location.

 

[clancy688]

See also IAEA/JNES/NIED Seminar on Nuclear Disaster & General Disaster Management against Tsunami and Earthquake, Tokyo, December 2007, “Safety Assessment and Disaster Management for Tsunami Hazards at Onagawa Nuclear Power Plant”, Y. Matsumoto, (Tohoku Epco, Japan)

Wow. The tsunami-chart is interesting. They plotted wave heigths along the coast for three major tsunamis (1611, 1896, 1933).
But at the Onagawa location, all of these three tsunamis were around 5 metres. The really big wave heights of 20 metres and more were reached on the shore starting at 100 km north of the plant location.

Warning, highly speculative:
So that's probably one of the reasons, they only build Daiichi 10 metres above sea level and not really water proof - because historic tsunamis didn't reach 15 metres at Fukushima which's between 100 and 200 km south of Onagawa...?

 

[PietKuip]

Wie lange war die Kühlung in Daiichi unterbrochen?

Cooling at Fukushima was interrupted for longer times than at Three Mile Island, but this was several hours after the chain reaction had been stopped. Thermal power was much lower.

 

[Dmytry]

Wow. The tsunami-chart is interesting. They plotted wave heigths along the coast for three major tsunamis (1611, 1896, 1933).
But at the Onagawa location, all of these three tsunamis were around 5 metres. The really big wave heights of 20 metres and more were reached on the shore starting at 100 km north of the plant location.

Warning, highly speculative:
So that's probably one of the reasons, they only build Daiichi 10 metres above sea level and not really water proof - because historic tsunamis didn't reach 15 metres at Fukushima which's between 100 and 200 km south of Onagawa...?

Sounds stupid. Should of been built to at least withstand max historical tsunami height for entire coast there, the crack goes all the way along. They've de-rated lifetime risk of failure for that plant to worse than 1/100 if we assume that max wave height location is approximately random.

 

[clancy688]

Building 4 has already exploded. Two panels have blasted out of the east side and impacted on the west facade of the turbine building for Unit 4, and smoke is pouring out of the east side of Building 4.

One last comment to that idea:

I checked the T-Hawk Video for the two impact spots you mentioned. There's a guard rail or something like this going along the turbine building. But the debris is sticking between the guard rail and the building, indicating it's come from above.

If it has come from the east side of Unit 4, it should have smashed the guard rail. But that's not the case. The impact damage on the west side of the turbine building origins in the blast at Unit 3. The smoke is probably an optical illusion, it's most likely smoke from Unit 3 as well.

 

[Borek]

Das ist fraglich.

Ich habe mich gefragt, ob es Tepco überhaupt möglich ist, die Reaktoren direkt zu kühlen, oder ob man die Druckbehälter via containment kühlt.

Das kann man nicht sicher ausschließen.

Scheinbar ist das noch nicht der Fall.

Please note: per forum rules all posts should be in English and those in other languages should be deleted.

 

[clancy688]

Please note: per forum rules all posts should be in English and those in other languages should be deleted.

Sorry... ^^; :/

 

[Jorge Stolfi]

Can somebody explain me how to interpret the fact that since several weeks know, i see written in the reports (Tepco, AIEA) that the fuel rods are around half length uncovered -so outside of water- in reactors 1 to 3?

The readings from the only sensors that are still working say that water level in the cores of reactors #1--#3 are 1.6 meters, 2.1 meters, and 2.2 meters below the top of the fuel, respectively. The most optimistic interpretation is that the fuel rods are still there, but uncovered by that amount. Pessimistic interpretations are boundless, of course.

Note that water is being continuously pumped into the innermost pressure vessel (RPV) of each reactor at the rate of >100 liter per minute, and yet the water level is not budging. So there must be leaks that can support that much flow out. It is not clear whether the water flowing out of the reactor pressure vessels is going into the second containment vessel (ironically called "drywell") and from there to the donut-like suppression chamber below; or whether the leak is in some pipe outside the drywell, so that the water is trickling down to the basement; or whether there is a return pipe leading outside the building.

As I understand, each water level sensor consists of two pipes that start in the RPV, one above the water and the other below it, and end on pressure meters outside the building. The difference in pressure between the two pipes gives the water level inside the RPV (about 10 kPa for each meter of water).

The water level sensors do seem to be partly damaged. There are two sensors (3 pipes?) in each reactor, and they give different readings. In the #2 reactor, one says the water level is 1.5 meters below the top of the fuel, the other says 2.1 meters. However, from previous comments in this forum, I gather that the plausible failure modes would cause this kind of sensor to err on the plus side. That is: if the readings are wrong, the actual water level is likely to be lower, rather than higher. That is because there is a steel sleeve between the RPV wall and the fuel, and the sensors may be measuring the water in the gap between the sleeve and the RPV, not the water in the core proper. I gather that the fuel could even be completely dry.