Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[Astronuc]

If the building 4 explosion were due to hydrogen from the spent fuel pool or from steam venting from the containment rising why would the roof and top wall cladding remain while the lower east facing wall appears to be blown out? The JAIF report for 1600 hours on March 17 suggests Unit 4 containment integrity is not damaged. Do the remains of building 4 suggest an explosion lower down in the containment and a major breach of the containment (or in the torus if it is not considered part of the containment)? Or is there a more likely explanation for the pattern of building 4 damage?

The size of the explosion depends upon the amount of hydrogen and how well it is mixed (on not) with O₂ at the time of ignition. Bear in mind that steam would also dilute the H₂ in air.

In Units 1 and 3, the hydrogen vented into the upper containment from the core, so perhaps steam did not dilute the hydrogen (hydrogen is lighter than steam), and the hydrogen-oxygen then ignited.

 

[Astronuc]

Yes it's difficult to judge elevation from that image but I can see the rocks that build up the seawall there.

Borek, myself and others have been saying the same thing previously in this thread. I know it sounds like a case of 20/20 hindsight but I'm also very surprised that a nuclear power plant would be so poorly protected from a tsunami.

In my opinion the quake was unavoidable but the tsunami was optional. And it's that "option" that is costing them so dearly now. I can see no reason why the plant couldn't have been situated where it would be safe from a 15m tsunami.

Clearly the height (or scale) of the tsunami was underestimated.

 

[BHamilton]

Question on timelines

Local, I am in USA Eastern Daylight Savings time and note that there is sometimes a 1-day difference between the day and time an event is reported in Japan, vs. the day and time I am hearing "breaking news". It is Thursday, 12:57 PM here, now. It is Friday, 1:56 AM at Fukushima. Obviously the international time line is in play.

Anyone have a source of a detailed local timeline for the events occurring at Fukushima that would avoid some of my confusion?

I don't have a simple link for that handy now, but the thing to remember is that JST is UTC+9, while EDT is UTC-4, so if you see times given in US Eastern, add 13 hours to get JST

 

[TCups]

I don't have a simple link for that handy now, but the thing to remember is that JST is UTC+9, while EDT is UTC-4, so if you see times given in US Eastern, add 13 hours to get JST

Yes but some of what I read says "Tuesday's explosion" etc. It isn't always clear. A single accurate timeline would be helpful. There must be one. I am just lazy and haven't searched thoroughly.

 

[BHamilton]

Yes but some of what I read says "Tuesday's explosion" etc. It isn't always clear. A single accurate timeline would be helpful. There must be one. I am just lazy and haven't searched thoroughly.

Ah, here we go: the wikipedia article has a timeline, and it's in JST and its probably as accurate as anything you'll find in news sources http://en.wikipedia.org/wiki/Timeline_of_the_Fukushima_nuclear_accidents"

 

[kfmfe04]

Interesting perspective from a Japanese insider:

http://www.asahi.com/english/TKY201103160136.html

 

[Reno Deano]

Does anyone know the type of fuel (standard U235 or Mixed Oxide/PU) used in the subject reactors? The reason is that MOX has a higher burn up rate and gap release than standard fuel.

 

[BHamilton]

Units 1 and 2 were on standard fuel, and 3 was MOX.

 

[uart]

Clearly the height (or scale) of the tsunami was underestimated.

I think the point is that the height of the tsunami couldn't have been be estimated when they built the plant, so more safety margin should have been allowed.

Everything else in the design seem to have safety margin and redundancy built in, but the elevation to protect from potential tsunami seems to have little safety margin. Six meters seems a bit like, "oh what's that biggest tsunami we've had in the last 100 years or so, yeah that will do, no need for any safety margin". The tsunami risk on the Pacific coast of Japan has been known to the Japanese for centuries. Even just restricting to the era of modern history, tsunamis bigger than 6m had been recorded.

Yes I know it's 20/20 hindsight, but this issue of site placement just seems like the biggest weakness in the whole design. Zero safety margin when compared to tsunamis from just the era of modern history. This surprises me since more elevation doesn't seem as if it would have been difficult problem.

 

[BHamilton]

What's the status of main power at the station right now? Is there any hope of getting primary pumping going again? As I understand it, the decay heat dies off quite slowly, somewhat of a power law, so more water will need to be continually added to the pressure vessels for quite a while.

 

[andyr]

I think the point is that the height of the tsunami couldn't have been be estimated when they built the plant, so more safety margin should have been allowed.

Everything else in the design seem to have safety margin and redundancy built in, but the elevation to protect from potential tsunami seems to have little safety margin. Six meters seems a bit like, "oh what's that biggest tsunami we've had in the last 100 years or so, yeah that will do, no need for any safety margin". The tsunami risk on the Pacific coast of Japan has been known to the Japanese for centuries. Even just restricting to the era of modern history, tsunamis bigger than 6m had been recorded.

Yes I know it's 20/20 hindsight, but this issue of site placement just seems like the biggest weakness in the whole design. Zero safety margin when compared to tsunamis from just the era of modern history. This surprises me since more elevation doesn't seem as if it would have been difficult problem.

15m is a huge height though. It seems relatively little to think about as it is so easily walkable. Going up though it is around 5 storeys. IIRC the tallest waves produced by the 2004 tsunami were 90ft (27m) high and that was the third largest earthquake ever recorded.

It's not just immediate hindsight with this situation, we have the benefit of 40 years of hindsight from when these plants were first built, probably nearer 50 from when they were first conceived and designed.

 

[Astronuc]

I think the point is that the height of the tsunami couldn't have been be estimated when they built the plant, so more safety margin should have been allowed.

Everything else in the design seem to have safety margin and redundancy built in, but the elevation to protect from potential tsunami seems to have little safety margin. Six meters seems a bit like, "oh what's that biggest tsunami we've had in the last 100 years or so, yeah that will do, no need for any safety margin". The tsunami risk on the Pacific coast of Japan has been known to the Japanese for centuries. Even just restricting to the era of modern history, tsunamis bigger than 6m had been recorded.

Yes I know it's 20/20 hindsight, but this issue of site placement just seems like the biggest weakness in the whole design. Zero safety margin when compared to tsunamis from just the era of modern history. This surprises me since more elevation doesn't seem as if it would have been difficult problem.

We've learned a lot about simulation and the geodynamics in 40 years.

I've put together a database of mag 8+, and mag 7-9 earthquakes around the world and around Japan since 1990. I got some interesting results!

There has been a significant tsunami in Alaska, in 1964 - at the time these plants were being designed.
http://en.wikipedia.org/wiki/1964_Alaska_earthquake
Mag 9.2, tsunami: A 27-foot (8.2 m) tsunami destroyed the village of Chenega!

If they had bother to design to that, then . . . .

Somehow the designers rationalized a lower tsunami that the one that took out the EDGs.

In the interim, 40+ years, there have been mag 8+ earthquakes, including one off Chilean coast last year.
http://earthquake.usgs.gov/earthquakes/eqinthenews/2010/us2010tfan/#details
That should have prompt a site review, but . . . .

 

[AntonL]

Reactor 4

Reactor 4

Reactor 4

Reactor 3

Reactor 1

 

[Astronuc]

Meanwhile - Progress by on-site workers
http://www.world-nuclear-news.org/RS_Progress_by_on-site_workers_1703111.html
17 March 2011
FIRST PUBLISHED: 4.56pm
UPDATE 1: 5.22pm

The high levels of radiation braved by workers at the scene in Fukushima Daiichi appear to have reduced after the expansion of the workforce and announcements of infrastructure improvements to come.

In recent days emergency managers were faced with an extremely complicated task to prioritise jobs across all four struggling reactor units in the main part of the site, while a skeleton operating crew maintained the status of units 5 and 6 about two hundred metres away.

http://www.world-nuclear-news.org/RS_Attempts_to_refill_fuel_ponds_1703111.html

 

[AntonL]

The high levels of radiation braved by workers at the scene in Fukushima Daiichi appear to have reduced after the expansion of the workforce and announcements of infrastructure improvements to come.

time scale of measured radiation (sorry labelling is in German) source is Tepco

 

[Astronuc]

Zeitpunkt = Time point = Time, der Messung = of the measurement.
Dosisleistung = Dose rate

 

[themaxmax]

Stills from this video showed some interesting green emissions (30 second mark):

http://www.youtube.com/watch?v=lBXqiw6EJUk"

Could this be chlorine vapor, or some kind of radioactive emission showing up on the CCD of the camera not visible to the naked eye?

 

[TCups]

Reactor 4

Reactor 4

Reactor 4

Reactor 3

Reactor 1

YIKES!
The damage at unit 4 is much more extensive than apparent on the earlier photo. It would seem the single gaping hole on the far side (next to the tower) with the "tongue" of stuff hanging out the hole is the least damaged portion of the building.

The green metal structure is the crane, I suspect. If so, and if it is over the SFP, then the SFP is indeed on the opposite side of the building from the picture of the first gaping hole and "tongue" of insulation.

All that said, it certainly doesn't look promising.

 

[Astronuc]

YIKES!
The damage at unit 4 is much more extensive than apparent on the earlier photo. It would seem the single gaping hole on the far side (next to the tower) with the "tongue" of stuff hanging out the hole is the least damaged portion of the building.

The green metal structure is the crane, I suspect. If so, and if it is over the SFP, then the SFP is indeed on the opposite side of the building from the picture of the first gaping hole and "tongue" of insulation.

All that said, it certainly doesn't look promising.

The green structure could be the refueling or fuel-handling machine, which could be over the core, or the spent fuel pool. SFP is obviously to either side of the core, but we don't know which side without a schematic.

 

[TCups]

The green structure could be the refueling or fuel-handling machine, which could be over the core, or the spent fuel pool. SFP is obviously to either side of the core, but we don't know which side without a schematic.

It looked like on the earlier schematic that the fuel-handling machine only went over the core or the pool, not on both sides of the pool. That said, it also looked as if there might be a second pool on the opposite side. Not a detailed enough drawing for me to know. What is encouraging is the apparent integrity of the concrete walls beneath the fuel-handling machine. Is is a safe assumption that the rising smoke is coming from the pool and fuel rods? I think probably so.

Here's the schematic again.

Is the overhead crane (2) that is orange perhaps a completely different structure than the yellow fuel-handling machine under it? The overhead crane rails do traverse the entire length of the building. The fuel-handling machine's tracks on the floor only go as far as the access to the core. And there does look to be a second pool of some sort on both sides of the core containment (3), (4).

 

[AntonL]

My analysis of https://www.physicsforums.com/showpost.php?p=3193827&postcount=363"

Reactor 1 to 3 are concrete frame with metal framed roof top. In reactor 4 the metal framed rooftop has been replaced by concrete construction thus a much stronger building. With H2 explosion 1 and 3 destroyed the metal frame rooftop leaving concrete structure much intact, a sort of a vent. However, in unit 4 when H2 exploded it had no vent thus destroying much of the concrete structure.

 

[TCups]

My analysis of new photos

Reactor 1 to 3 are concrete frame with metal framed roof top. In reactor 4 the metal framed rooftop has been replaced by concrete construction thus a much stronger building. With H2 explosion 1 and 3 destroyed the metal frame rooftop leaving concrete structure much intact, a sort of a vent. However, in unit 4 when H2 exploded it had no vent thus destroying much of the concrete structure.

Good eye, Anton. And as I look closer, Astronuc is exactly right, as usual. The more apparent green structure is the fuel-handling machine. There is a much heavier overhead crane above it.

Interesting that image 193230 seems to have been cropped, perhaps right above where the contents of the pool might have been visible in the shot. Hmmm.

 

[AntonL]

Interesting that image 193230 seems to have been cropped, perhaps right above where the contents of the pool might have been visible in the shot. Hmmm.

Hmmm, we have not seen any photos in possession of US government of todays surveillance flight by drone, which USA have passed to Japan. I just read that USA will reimburse 20000 US citizens their flight home Hmmm they seem to know more than they willing to tell

 

[LanceV]

time scale of measured radiation (sorry labelling is in German) source is Tepco

This is interesting. It seems that the emission of radioactive material only happened in "discrete" events. After each event an exponential decay can be observed, as expected if the radioactive material is not replenished.
So a slow burn or oxidation or whatever of the possibly bare fuel rods in the SFPs seems unlikely as this would lead to a continuous emission.
So would it be reasonable to assume, that the radioactive material is emitted from a slightly damaged containment?

Btw: The last picture in your earlier post also depicts reactor 3 (not 1).

 

[M. Bachmeier]

Hmmm, we have not seen any photos in possession of US government of todays surveillance flight by drone, which USA have passed to Japan. I just read that USA will reimburse 20000 US citizens their flight home Hmmm they seem to know more than they willing to tell

Seems there's no indication at present that photos will be released for public scrutiny.

 

[Astronuc]

It looked like on the earlier schematic that the fuel-handling machine only went over the core or the pool, not on both sides of the pool. That said, it also looked as if there might be a second pool on the opposite side. Not a detailed enough drawing for me to know. What is encouraging is the apparent integrity of the concrete walls beneath the fuel-handling machine. Is is a safe assumption that the rising smoke is coming from the pool and fuel rods? I think probably so.

Is the overhead crane (2) that is orange perhaps a completely different structure than the yellow fuel-handling machine under it? The overhead crane rails do traverse the entire length of the building. The fuel-handling machine's tracks on the floor only go as far as the access to the core. And there does look to be a second pool of some sort on both sides of the core containment (3), (4).

The overhead crane is used to lift the heavy plug and upper equipment of the top of the reactor pressure vessel (RPV). The plug can be set aside on the floor (I'm not entirely familiar with specific practices). The RPV head and internals, e.g., steam dryers, would be placed in an equipment pool (4) for shielding.

The refueling machine handles the fuel between the SFP (3) and core. There should be a transfer canal between the reactor cavity and SFP. When the core is being unloaded or loaded, the irradiated fuel is transferred underwater which shields the workers from the radiation.

Some wonder if the any of the SFPs or the transfer canal area, particualy in Unit 4, were damaged by the quakes. If so, there could be a leak - which compounds the problem of water loss from the SFP. BUT - we don't have that information.

 

[1001001]

What is the volume of SFP's in Daiichi reactors 3 and 4?

 

[rjb100]

Does anyone understand why the Grid supply from the Japanese nuclear plants cannot be simply back fed to supply electricity to the cooling pumps.

Relying on diesel generators at all nuclear plants seems a little hit and miss.

 

[andyr]

Does anyone understand why the Grid supply from the Japanese nuclear plants cannot be simply back fed to supply electricity to the cooling pumps.

Relying on diesel generators at all nuclear plants seems a little hit and miss.

You mean from other plants that were unaffected? Or you mean from the Fukushima plant?

 

[Astronuc]

Does anyone understand why the Grid supply from the Japanese nuclear plants cannot be simply back fed to supply electricity to the cooling pumps.

It appears that the transmission and distribution system in the area was damaged or destroyed by the quake, and parts by the tsunami. TEPCO is attempting to put in a 1 mi/1.6 km line ASAP - and I expect they have been working very hard to restore grid connection.

Relying on diesel generators at all nuclear plants seems a little hit and miss.

The EDGs are there precisely to provide power when there is loss of offsite power - loss of connection to the grid.

 

[jinxdone]

Perhaps. But as a radiologist, I make my living with my eyes, interpreting what I see. Here is a picture from the net of the Fukushima (nomen, omen?) of units 3 and 4, dated October 3, 2008. Note the location of the berm (X).

another view, after unit 3 has exploded, but before the explosion and fire at unit 4:

http://media.kansas.com/smedia/2011/03/14/20/495Japan_Earthquake.sff.slideshow_main.prod_affiliate.80.jpg

Some brave soul peeked out from behind that berm (X) in the first photo to take this picture (annotated with my personal interpretations).

Presuming the access tunnel (1) in the diagram below is coming from the building next to the reactor in the first photo, which seems reasonable, that square hole in the side of unit 4 is, in fact, precisely where the diagram puts the SFP's location (3).

Do you think the roof of the Unit 4 building still looks intact? If there is still (boiling?) water in the SFP, where is the steam? Instead, I see a faint cloud of dark, sooty smoke wafting from the square hole with the red dots inside at an angle across the tower to the right, in the last photo. I hope I am wrong, but my eyes tell me something different from the official reports you quote.

I looked at the helicopter video frame by frame. There are a few frames in it showing the side of reactor building 4 with the supposed SFP hole in it.

The angle is only visible for a few frames before the tower obscures the view at 00:57. The copter is moving from this location showing reactor 4 towards the bottom left and reactor buildings 3, 2 and 1 are shown in succession in this fly-by.

Curiously, I think there should have been a much better view of this side of reactor building 4 earlier in the video, as the helicopter was flying the other way. But this part of the video is missing (I would assume it has been cut out?).

See the video for yourself on http://www.youtube.com/watch?v=lBXqiw6EJUk".

 

[turbo]

Surely, it is not necessary to rely on hand-held video taken from a helicopter trying to stay out of a dangerous or fatal radiation zone. We have a carrier group off-shore that likely has remote surveillance drones. Decent hi-rez stuff (with IR sensors as well, possibly) that could show us in great detail what is going on there without risking human exposure.

 

[Astronuc]

Worker at Japanese nuclear plant: We’re putting our lives on the line

http://news.yahoo.com/s/yblog_thelookout/20110317/us_yblog_thelookout/worker-at-japanese-nuclear-plant-were-putting-our-lives-on-the-line

The sprayed water like they were fighting a fire, not filling a pool with water.

 

[turbo]

Worker at Japanese nuclear plant: We’re putting our lives on the line

http://news.yahoo.com/s/yblog_thelookout/20110317/us_yblog_thelookout/worker-at-japanese-nuclear-plant-were-putting-our-lives-on-the-line

The sprayed water like they were fighting a fire, not filling a pool with water.

Yep. Air-dropping water from a bucket made for fighting forest fires is not too effective. To replace half of the water in a 40x40x40 SFP would require 992 tons of water, accurately delivered. Earlier reports that 30 (IIR) tons of water had been dumped from 'copters seem like a drop in the bucket, especially when looking at that image, because the water is essentially going about everywhere and is not targeted.

For fire-suppression in a brushy place, those drops might be effective, but not here.

 

[TCups]

Yep. Air-dropping water from a bucket made for fighting forest fires is not too effective. To replace half of the water in a 40x40x40 SFP would require 992 tons of water, accurately delivered. Earlier reports that 30 (IIR) tons of water had been dumped from 'copters seem like a drop in the bucket, especially when looking at that image, because the water is essentially going about everywhere and is not targeted.

For fire-suppression in a brushy place, those drops might be effective, but not here.

I am wondering if there isn't some place they could scoop up lots of snow and drop that. Per volume, the weight wouldn't be different. Snow would be less dense than water, but big snow ball might be easier to drop precisely on target, and the heat of transition of the ice would provide an additional 880Kcal/M of cooling as it melted to water to fill the SFP.