Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[unlurk]

From the pictures I have seen posted here, it seems building 3 has steam coming from 3 areas, and they all seem to be at what I believe would be the edge of the reactor core. Is it possible that this is where all the steam is coming from? Containment, or reactor cavity escaping around weak spots at the edge? (Not a critical SPF3?)

And if so, is it possible that there had also been part of the explosion occur on floors below the refueling deck? Which would explain the damage to the north west corner?

If that is entirely possible, I would love to hear the mechanics of how it could have happened. In layman terms, obviously! :D

Thanks in advance...

In my post just above I propose that the containment lid(s) for the drywell were physically moved on March 14th during the beginnings of the explosive event.

I'll add to that that it is unlikely that the shield plugs ever achieved a tight seal again after that event. The result is gas leakage from the drywell and occasional puffs - or belches from the lower regions.

Oh, BTW
Thanks again for finding that seismic data, it's just too bad that there is no data for the 14th.

 

[razzz]

http://earthquake.usgs.gov/earthquakes/seqs/events/usc0001xgp/

 

[yakiniku]

The same question I ask with the installation of what is obvious second hand tanks (rust marks on the flanges). I stated earlier I can see no evidence of deep foundations (no excavation marks) just a leveling slab of concrete on the tarmac. Supposedly they will use similar temporary flexible pipes to pump contaminated water to these tanks. Furthermore these tanks are bottom filled (as per the drawing snippet), catastrophic result if failure in filling system.

Regarding the storage tanks, the photo I saw previously (attached) looks to at least have a lower center of gravity. I wonder where the tanks from the older attached photo are located.

When tanks are bottom filled, what safety mechanisms are available to stop the liquids flowing back out if there is a failure in the filling system?

 

[MiceAndMen]

Re lifting a shroud through a round hole in roof with a crane
here's what TEPCO proposed in a 1995 paper, for a somewhat bigger lift

{ does anybody know how to embed a PDF picture? }
this link., page 6 of 8

http://www.jsme.or.jp/monograph/pes/1999/ICONE7/PAPERS/TRACK04/FP7292.PDF

edit tried to insert image no luck

There is a construction video on youtube that someone here pointed out a while back. At around the 10:30 mark you can see them installing the RPV for Unit 1 way back when.



A few weeks ago I posted about the core shroud replacements TEPCO has been doing https://www.physicsforums.com/showpost.php?p=3247620&postcount=3769

The first link in that post goes to a Hitachi website that has some good information. One of the pages indicates the core shroud is about 75% the diameter of the RPV and about 1/3 as long from top to bottom. The last link is for a different PDF from the same conference as the one you posted. It describes some of the work TEPCO did when they replaced Unit 3's core shroud back in the late '90s.

 

[yakiniku]

elektrownik's post was a few hours ago, the news piece you cite was released on the 8th

As stated, it was for the photos that were posted previously of steam over the reactors (not the photo from elektrownik but the time before that).

Should TEPCO's statements be true, it is possible that the new photos are the result of the same ongoing situation.

 

[Most Curious]

In my post just above I propose that the containment lid(s) for the drywell were physically moved on March 14th during the beginnings of the explosive event.

I'll add to that that it is unlikely that the shield plugs ever achieved a tight seal again after that event. The result is gas leakage from the drywell and occasional puffs - or belches from the lower regions.

The Drywell head has leaked during past tests in the US - at pressures far less than those reported at unit 3. Blowing out a gasket between the DW Head and Drywell / PCV is not out of the question. Even a small leak would allow enough hydrogen to accumulate to make a mess. If a hydrogen explosion occurred IN the Drywell, further damage to the DW head would be likely. It kinda looks like some permanent damage to that seal has occurred and is now leaking steam. Would not take a large area of failure to allow that amount of steam to escape.

Hopefully a member with better knowledge than mine will confirm / deny this: I doubt the concrete biologic shield plug or the interlocking blocks in the fuel tunnel were EVER water or air tight! Steam above the DW head will leak to the refueling floor and beyond.

 

[unlurk]

I doubt the concrete biologic shield plug or the interlocking blocks in the fuel tunnel were EVER water or air tight!

And especially not hydrogen tight. I think you have hit the nail on the head.But it seems as if you and I are the only two here who understand (or are willing to speak about) what is going on with these "steam leaks."

There seems to be some taboo subjects here.edited I meant hydrogen not nitrogen

 

[NUCENG]

In my post just above I propose that the containment lid(s) for the drywell were physically moved on March 14th during the beginnings of the explosive event.

I'll add to that that it is unlikely that the shield plugs ever achieved a tight seal again after that event. The result is gas leakage from the drywell and occasional puffs - or belches from the lower regions.




Oh, BTW
Thanks again for finding that seismic data, it's just too bad that there is no data for the 14th.

FYI shield plugs are only designed to provide shielding diirectly over the core during normal operation. They are set in place not bolted or sealed so they have no fiunction to provide a pressure seal. The steam space above the dryers and separators is filles with N-16 during operation. The core itself is shielded from the steel of the steam dome, dryers and separators, vessel head and the containment cap dome and the liquid water above the core. N-16 decay generates high energy gammas which produce a shine type of exposure if not shielded.

Once the containment cap begins to leak (as low as 27 psid based on sources quoted in earlier posts) the release is to the refueling floor air space.

 

[sp2]

WSJ reporting over-limit Cesium-137 in tea leaves grown SOUTH of Tokyo.

IF this is confirmed, it's a very big deal.

http://online.wsj.com/article/SB10001424052748703864204576317152274615660.html

 

[Jim Lagerfeld]

Looks like the recalibration efforts in reactor one may have succeeded, however the news is not good. In fact it may be very bad, although I suspect many people were already expecting something like this:

"JNN's investigation has revealed that there is hardly any water inside the Reactor Pressure Vessel (RPV) and the Containment Vessel of the Reactor 1 at Fukushima I Nuclear Power Plant"

http://ex-skf.blogspot.com/2011/05/fukushima-i-nuke-plant-reactor-is-rpv.html

Guess we will now have to wait for figures and confirmation from TEPCO.

 

[Most Curious]

Nuceng, while we are in this area, I have a question:

I understand during refueling the reactor well is flooded and a seal exists between the RPV and DW. (IIRC, there was an accident some years back where it leaked and allowed some 200,000 gallons of water to leak into the DW.) My question is, how or if, this seal is changed, maybe a hatch or several are removed after the reactor head is installed and the well is drained but before the DW head is installed? I assume during operation the lower DW communicates with the DW head area above the reactor head?

 

[unlurk]

FYI shield plugs are only designed to provide shielding directly over the core during normal operation. They are set in place not bolted or sealed so they have no function to provide a pressure seal. The steam space above the dryers and separators is filles with N-16 during operation. The core itself is shielded from the steel of the steam dome, dryers and separators, vessel head and the containment cap dome and the liquid water above the core. N-16 decay generates high energy gammas which produce a shine type of exposure if not shielded.

Once the containment cap begins to leak (as low as 27 psid based on sources quoted in earlier posts) the release is to the refueling floor air space.

That fits with my previous assumptions.

Are you also in agreement with my scenario about what happened on March 14th?

By that I mean that with the 27 or 57 or whatever psi level that was continuously present that morning a few puffs of oxygen/hydrogen reaction lifted the containment caps enough to create a much more substantial jet of hydrogen and flame and steam out into the region of the "cattle trough" initiating the sequence of events which we can see on film?

Are you also in agreement with the idea that occasional "puffs", or minor gas explosions are occurring and causing the episodes that we have seen this morning and last week?

 

[yakiniku]

WSJ reporting over-limit Cesium-137 in tea leaves grown SOUTH of Tokyo.

IF this is confirmed, it's a very big deal.
http://online.wsj.com/article/SB10001424052748703864204576317152274615660.html

Singapore banned vegetables that were shipped from Shizuoka. Shizuoka is further away from Tokyo than Kanagawa. The levels of radiation exceeded codex guidelines. The news is quite old but I didn't see it widely publicised:

http://www.soshiok.com/article/15097

http://www.asiaone.com/News/AsiaOne+News/Singapore/Story/A1Story20110401-271240.html

 

[Sabbatia]

elektrownik's post was a few hours ago, the news piece you cite was released on the 8th

I'm glad they responded to it...even if I don't necessarily trust them. I was watching at the time are talking about and it looked like black smoke as it moved past the towers. Pics were posted here about it over the weekend. The pics posted today made me think it was fog.

 

[robinson]

A thread about one reactor problem would be hard to follow. This one is actually about 6 reactors, and at least six fuel ponds, and all kinds of water related issues, and four explosions, in four different reactor buildings. It's not surprising that it is vast and almost impossible to catch up if you haven't been reading since the start.

This will probably get worse in the future.

 

[WhoWee]

A thread about one reactor problem would be hard to follow. This one is actually about 6 reactors, and at least six fuel ponds, and all kinds of water related issues, and four explosions, in four different reactor buildings. It's not surprising that it is vast and almost impossible to catch up if you haven't been reading since the start.

This will probably get worse in the future.

That is a fair assessment.

 

[AntonL]

Areva demonstrates some of the water decontamination equipment

[PLAIN]http://k.min.us/insXmQ.JPG
http://www.youtube.com/watch?v=jvOwzZSH9gI&NR=1"

 

[NUCENG]

Interesting find, it's not only the shroud, it's a study about replacing the whole RPV! I wonder if any of their RPV are in a state that might need full replacement?

The shroud goes into the RPV. It probably doesn't fit through the refueling tunnel and that vertical shaft for cask and fuel and whatever transfer in the SW corner, does it?

EDIT: The documents in your other post are also pretty interesting (It's kind of interesting that all this stuff can be found on the internet...). So, it is extremely likely they had welding equipment inside unit 4, as there seems to be a whole bunch of welding involved there and they mention that in one of those documents. They also write they sliced the old shroud into small pieces and "put the containers in DSP". They used "underwater plasma slicing".

EDIT2: With respect to https://www.physicsforums.com/showpost.php?p=3292292&postcount=6332 , one of the documents you found mentions that N2 nozzles are recirculation inlets, N4 is feedwater as we know, and N5 is core spray. (Just for completeness.)

[I don't think there is any reasonably easy way to link to a picture in a pdf file. Attached is a simple screenshot.]

I had a friend pull information from design drawings in a BWR-4 Mk1 plant. The core shroud is 167 inches ID (4.24 m) x 204 in length (5.18 m). The first floor is the reactor building where the cask loading/unloading is performed is about 28 ft high (8.54 m). The equipment hatch from the railroad airlock to the refueling floor is 20 ft x20 ft (6.09 m x 6.09 m. Can't guarantee those dimensions apply to Fukushima, but at least at that plant a replacement shroud could have been uprighted and lifted through the equipment hatch.

The main reasons that the replacement of an RPV is different are that the weight exceeds the capacity of the crane; there is no way to upright a load that big on the cask load area; and the RPV is taller than the refueling floor clearance for the RB crane. Those limitations don't apply to the core shroud.

 

[MiceAndMen]

Once the containment cap begins to leak (as low as 27 psid based on sources quoted in earlier posts) the release is to the refueling floor air space.

This has been my feeling all along: that a compromised drywell cap seal allowing gas or steam to escape would result in that gas diffusing upward through the non-pressure-sealed shield plugs and into the upper reaches of the secondary containment, i.e. the reactor building. That makes more sense to me than jetting sideways through the fuel transfer chute blocks and whatever seal might be present there. The pressure increase, to me, seems more likely to seat the tongue-and-groove shield blocks leading to the fuel chute even more firmly in place, making it less, not more, likely to get through there. Not when there's a path out through the plugs above that were never designed to hold pressure at all.

There are other scenarios studied over the years that result in containment breach that do not involve the drywell cap being displaced or breached. A structural failure of the torus is just as likely to be the release point for an overpressurized containment as the drywell cap. So are the seals for electrical conduit drywell penetrations. So are the emergency cooling systems' pump seals. So are leaks in the venting ductwork. All these potential pathways could leak substantial amounts of hydrogen into the building.

Occam's Razor leads me to believe that a burping drywell cap jetting burning hydrogen sideways at the exact spot where the fuel chute blocks/gates/seals might be weak is less likely to be the release path for hydrogen into the secondary containment than any number of other, simpler explanations. I'm not claiming the idea is totally without merit, but until we learn more I don't see how it can be given more credence than any of the other equally credible scenarios.

 

[unlurk]

A thread about one reactor problem would be hard to follow. This one is actually about 6 reactors, and at least six fuel ponds, and all kinds of water related issues, and four explosions, in four different reactor buildings. It's not surprising that it is vast and almost impossible to catch up if you haven't been reading since the start.

This will probably get worse in the future.

I have been trying to catch up for three weeks now.
I'm up to about post #3750 in my begin at the beginning task but the posts at the end keep me busy too. Today has seen a lot of posts. I think I'm only about 500 posts short of having read them all but I'm not sure if I'll ever get there.

IMO
If this thread were broken up it would then be impossible to develop a big picture of the event. I want to hear about what people are discussing about aspects of this that I'm not really keeping up on. If the thread were broken up I know that I wouldn't keep current with all the threads.

 

[etudiant]

A thread about one reactor problem would be hard to follow. This one is actually about 6 reactors, and at least six fuel ponds, and all kinds of water related issues, and four explosions, in four different reactor buildings. It's not surprising that it is vast and almost impossible to catch up if you haven't been reading since the start.

This will probably get worse in the future.

Unfortunately, you are entirely correct.
Just the lake in the turbine hall will take till year end to drain, given a 1200 ton/ day processing capacity, a 100,000 ton water problem and a 500+ ton/day new water injection.
So this thread can reasonably be extrapolated to at least 20,000 posts, possibly much more as additional data becomes available.
At The Oil Drum, another interesting site, the discussion threads were chopped into roughly weekly sections.
This kept them manageable, but also made for a lot of repetition.
Unfortunately, this disaster has so many dimensions that even a weekly update could easily have a thousand entries.
Nevertheless, I do hope the leaders of this forum take time to look ahead, make a realistic appraisal of the expected volume of activity and gear up accordingly. This will cost money, but I believe this forum is sufficiently useful that the needed support will be forthcoming. The Gulf spill had a similar catalyzing effect on The Oil Drum.

 

[AntonL]

Looks like the recalibration efforts in reactor one may have succeeded, however the news is not good. In fact it may be very bad, although I suspect many people were already expecting something like this:

"JNN's investigation has revealed that there is hardly any water inside the Reactor Pressure Vessel (RPV) and the Containment Vessel of the Reactor 1 at Fukushima I Nuclear Power Plant"

http://ex-skf.blogspot.com/2011/05/fukushima-i-nuke-plant-reactor-is-rpv.html

Guess we will now have to wait for figures and confirmation from TEPCO.

Confirmed Unit 1 has huge problems
http://www.asahi.com/national/update/0512/TKY201105120174.html
http://english.kyodonews.jp/news/2011/05/90559.html

and check the water level logs published by Tepco
http://www.tepco.co.jp/nu/fukushima-np/f1/images/011_1F1_05120600.pdf

What does this imply for the other reactors especially Unit 3 which shows extremely high temperatures and 150^oC at the bottom.

Or have Tepco engineers made a mistake in calibrating the differential pressure meters?

 

[Jim Lagerfeld]

Looks like the recalibration efforts in reactor one may have succeeded, however the news is not good. In fact it may be very bad, although I suspect many people were already expecting something like this:

"JNN's investigation has revealed that there is hardly any water inside the Reactor Pressure Vessel (RPV) and the Containment Vessel of the Reactor 1 at Fukushima I Nuclear Power Plant"

http://ex-skf.blogspot.com/2011/05/fukushima-i-nuke-plant-reactor-is-rpv.html

Guess we will now have to wait for figures and confirmation from TEPCO.

Confirmed at 12pm TEPCO conference: fuel in reactor one is completely exposed; previous reports that only the top 1.5-1.7m of the fuel were exposed attributed to sensor error.

They now believe 100 percent fuel melt in reactor one, with some water cooling still occurring in the bottom of the vessel, as indicated by the relatively low temperatures measured outside the vessel.

They are 'strongly emphasizing' that they believe they can still cool the vessel.

(Loose partial translation to give you the gist)

*Edit - also see AntonL's links above!

 

[unlurk]

They are 'strongly emphasizing' that they believe they can still cool the vessel.

As long as there isn't a problem with re-criticalities the worst is probably over with unit one. They will probablyhave to keep cooling it for the next decade or so.

 

[jim hardy]

Thanks M&Mand Nuke.

Did you friend have the crane clearance on refueling floor?

One of the articles i saw today showed a generic 'to scale' drawing of shroud standing up in a GE containment, ready to be lifted and set into vessel..
There was barely clearance for crane with shroud sitting in S/D pool which is lower than refueling floor. So i think that's the bottleneck, vertical clearance to overhead crane once it's up to refueling floor.
Looked like there's plenty of clearance to roof but crane is lower than roof by at least enough for people to stand on it and clear the roof beams.

The article was by a services company that makes a special lifting ring for shroud, to accomplish that particular lift - i looked for an hour and can't find it again but will post link if do.

So it was a generic drawing , again not Fukushima . But a nice round roof beam sounds to me more likely to have been made on purpose than accident.

 

[NUCENG]

Nuceng, while we are in this area, I have a question:

I understand during refueling the reactor well is flooded and a seal exists between the RPV and DW. (IIRC, there was an accident some years back where it leaked and allowed some 200,000 gallons of water to leak into the DW.) My question is, how or if, this seal is changed, maybe a hatch or several are removed after the reactor head is installed and the well is drained but before the DW head is installed? I assume during operation the lower DW communicates with the DW head area above the reactor head?

You are correct. There are manholes in the bellows which are closed during floodup of the reactor cavity for refueling. They are opened during normal operation to permit drywell cooling to cool the area above the vessel head.

 

[Jim Lagerfeld]

As long as there isn't a problem with re-criticalities the worst is probably over with unit one. They will probablyhave to keep cooling it for the next decade or so.

I wish I could concur with you on that point, but the fact that they are unable to maintain any stable water level over the core at this point does not inspire confidence.

http://www.47news.jp/CN/201105/CN2011051201000254.html

This summary goes on to say that they are 'making preparations' towards the installation of a new cooling system for reactor one, but that they are currently struggling to 'come to grips' with conditions inside the reactor one building and that this would 'probably have an impact' on the implementation of the plan.

And this is all presuming that nothing goes wrong at any of the other potential crisis points.

 

[NUCENG]

Thanks M&Mand Nuke.

Did you friend have the crane clearance on refueling floor?

One of the articles i saw today showed a generic 'to scale' drawing of shroud standing up in a GE containment, ready to be lifted and set into vessel..
There was barely clearance for crane with shroud sitting in S/D pool which is lower than refueling floor. So i think that's the bottleneck, vertical clearance to overhead crane once it's up to refueling floor.
Looked like there's plenty of clearance to roof but crane is lower than roof by at least enough for people to stand on it and clear the roof beams.

The article was by a services company that makes a special lifting ring for shroud, to accomplish that particular lift - i looked for an hour and can't find it again but will post link if do.

So it was a generic drawing , again not Fukushima . But a nice round roof beam sounds to me more likely to have been made on purpose than accident.

Oops, missed that. From the floor to the bittom of the crane support girders is 24 ft (7.3 m). The shroud would be light enough that the would use the secondary hook on the RB crane. Depending on the size of the lifting ring it might be close. There is also plenty of room on the refueling floor for a purpose built crane to do the lift if the RB crane is too low. The bottom of the roofing girders is about 40 feet above the floor (12.2 m).

 

[unlurk]

unable to maintain any stable water level over the core at this point does not inspire confidence.

There is no "core" anymore. That's an anachronism in the case of units 1,2 and 3.

There is a puddle of corium (or several such globs or puddles) which have been cooling for 2 months and which will decline in temperature as time goes on.

 

[AntonL]

They are 'strongly emphasizing' that they believe they can still cool the vessel.

As long as there isn't a problem with re-criticalities the worst is probably over with unit one. They will probablyhave to keep cooling it for the next decade or so.

As long as an earthquake does not shake it up and rearranges the fuel such that re-criticality is possible. All the core may not have collapsed and fallen to the bottom and is cooled by the continues rain from the core spray. Who knows -

(Arnie Gunderson will have a field day analysing this latest news)

 

[jim hardy]

thanks 7.3m - 5.18m = 6.95 ft for a lifting bar and crane hook...

tight, sure not much clearance to lift it above floor... but it might work.

Murphy wouldn't let us have a definite go-no go.

thanks!

 

[yakiniku]

As long as there isn't a problem with re-criticalities the worst is probably over with unit one. They will probablyhave to keep cooling it for the next decade or so.

Are there indications that if the fuel has melted and is at the bottom of the RPV that it is being sufficiently cooled such that it won't melt through the RPV?

 

[MiceAndMen]

They now believe 100 percent fuel melt in reactor one, with some water cooling still occurring in the bottom of the vessel, as indicated by the relatively low temperatures measured outside the vessel.

The word "meltdown" is very non-specific in its meaning, I know that. But this sounds like confirmation of one. If all the fuel has relocated into the bottom of the RPV and cooling is uncertain, then do they have any choice now except to wait and see what happens next?

Even if the drywell could hold water, I don't think you'd want any there just waiting for corium to fall into it. That could create the mother of all steam explosions and perhaps a huge release of fission products into the environment.

 

[razzz]

I was under the impression that if you commit to a GE designed reactor, you get an onsite nuclear engineer from GE to assist and advise for life. 6 reactors, 6 onsite nuclear engineers from GE. Not that GE gets to approve of anything but they certainly are in the know about how their designs are performing from day 1.

Unit 1 sounds scary because they don't know what's going on inside. Wondering if the saltwater injections changed the parameters of cooling somehow via rapid decay or encrustation or some other hereto unknown reaction(s). That radioactive lava has to be a couple of feet thick or more.

 

[Jim Lagerfeld]

There is no "core" anymore. That's an anachronism in the case of units 1,2 and 3.

There is a puddle of corium (or several such globs or puddles) which have been cooling for 2 months and which will decline in temperature as time goes on.

You are dead right on this, it's no longer a 'core' as such. And it will cool eventually, and 10 years of water cooling now sounds more realistic than TEPCO's 'cold shutdown in 6-9 months' statement.

Tepco were very keen to stress that there is still 'some' water over the corium blob(s) and that this 'is currently cooling the fuel'.

However to me, it also seems that their ability to get sufficient water to the blob is deteriorating rather than improving over time. They also announced that there is no measurable water in the secondary containment, so they will have to abandon the cool from the outside 'water coffin' plan too.

Hopefully they are able to work around the 700mSv/h inside the building and get a more effective cooling system up and running, but if they can't, how long for the blob to cool of it's own accord?