Japan Earthquake: nuclear plants

shadowncs

And pic4 (sorry for doublepost)

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MadderDoc

Indeed. The puffs appear from behind the corner of unit 2, while they do block the view to unit 1, i.e. the puffing would seem to be in the vicinity of the space between those two units.
We could be looking at visual evidence of the initial operations of the unit 1 Isolation Condenser.

clancy688

How thick is the door in question?

If it's an entry into the containment then it ought to be a massive, reinforced steel door. Is there anything else besides an explosion which could deform such a door?

A question to the physicists here: How would a steel door react if it's suffering massive heat on one side, but not on the other? Would it really bend outwards, away from the heat?
Perhaps I'm telling total bogus now, but if there'd be any thermal deformation, I'd expect the door to bend exactly the other way - inwards.

zapperzero

It doesn't matter which way it would bend. You'd have scorch marks at the very least - in fact, you'd have no paint left on that door at all, if you put in enough heat to warp it permanently. Not much door either, I believe :)

shadowncs

Judging from unit 2 video the door is not as thick as one might guess. Certainly it has a knob and can easily be opened (and more importantly closed) by hand. As I understand it this is not a door into containment, it's just a door to the torus room. While torus is part of containment the room in which it resides might not qualify as containment (ie if torus breaks then containment is breached). If that is the case then to get that pressure differential to bend the door (even if the door is not that thick) means a break either in torus or in one of the massive pipes that leads to drywell AND a pressure spike in the drywell.

Now normally the drywell has no oxygen (N2 atmosphere). However the explosion happened 3 days (if I remember) after power was lost which means there is ample time for some percentage of oxygen to seep in and react with the H2 from Zr-steam after venting. Another alternative that I see is a superheated bundle of metal falling all at once into a pool of water - no idea if the core (or a big chunk of) can possibly drop all at once to the bottom of RPV into water causing a steam explosion.

Not to beat a dead horse but I'd personally go with H2 explosion in drywell.

clancy688

Um, it's not the first time I've posted the following document here (though jlduh provided it first), but it was mostly ignored. So, here again:

http://www.osti.gov/bridge/servlets/...Hq/5835351.pdf

"The impact of BWR MK I primary containment failure dynamics on secondary containment integrity."

We probably do have some corium outside the pressure vessel, at least that's what TEPCO thinks, and this paper proclaims that under certain circumstances (corium attacks the drywell liner) a blowdown in the torus room is very likely.


On a second note:
If there actually is a hole connecting the primary containment with the torus room (either through drywell liner failure as explained above or torus damage), shouldn't the torus room be filled with water?
As far as I understand, TEPCO kept pouring water into the reactor vessels and containments until the drywell was filled to a certain height, so if there is a leak to the torus room, it should be filled with water as well.

Edit: Oh, tsutsuji already answered that question:

Which spikes new questions for me:

First, where does the water come from? If shadowncs is correct and those chambers are secondary and not primary containment, then there have to be some containment breaches in either the torus itself or the drywell. Where else would the water come from otherwise?

And second, why are they only filled partially and not totally? If there are leaks and if there's water in the drywell (to cool escaped fuel) then I'd expect the lower lying chambers to be totally submerged and not only partially. Why aren't they?

shadowncs

And perhaps it is? In the vids you can clearly see both unit 2 and unit 3 lower-level basements are flooded at the stairwell. For unit3 vid the worker spends a large amount of time measuring radioactivity of the stairwell water, outside the torus room, which appears to be a few meters lower than the basement level the torus room door is located. That water comes from somewhere perhaps the most likely being the torus room. Remember those rooms are quite high. As to water in drywell, TEPCO is yet to confirm there is any water at all - see unit 2 endoscope. We simply don't know yet but I tend to agree, if the torus were intact then we'd expect water in drywell.

I'm surprised by the fact the unit 2 door could be opened, that with the "explosive sounds" reported coming from unit 2 torus early on.

SteveElbows

Don't worry you are not alone, I go on about blowdown to the torus room from time to time, especially now that we've had a glimpse into the torus rooms so it is fresh in peoples minds. Cant take it much further though until we have more useful evidence or data, which could be a long wait.


TEPCOs original stabilisation plan involved filling the drywells up with water to a certain height, but they realised it wasn't working, and all that contaminated water was then found in the basements. Also when they did the endoscope camera thing at reactor 2 the water level in the drywell was lower than their more recent assumptions, so they are still playing catchup with reality. The next endoscope will be longer and they hope to get a visual on the water, though frankly I wouldn't be shocked if it turns out there is hardly any water staying in the drywell at all. We don't have too long to wait till this next mission, Im sure its supposed to happen in March.

Im sure the torus rooms don't count as primary containment. And they have not been able to deny some kind of containment breach ever since they found so much water at the lower levels.

The lower levels are not completely submerged for several reasons. Firstly there is also lots of water in the basement of the turbine buildings, which may be flowing from the reactor building, so there is lots of room for the water to take up. And secondly they have been pumping water out of the turbine buildings to be processed by the water treatment systems. This ties into the leaks into the sea via trenches etc, and their desperate race against time to keep the water level to a certain limit. The water level fluctuates but ue to the pumping it doesn't get high enough to fill the entire torus room.

But I also think its quite likely that they may be relying on the water in the basements to provide shielding against anything nasty that may have fallen down there, and cooling of such corium, so even if they have the capacity to pump almost all of the water out of the torus rooms, turbine basements etc, I don't know as they would want to at this stage.

SteveElbows

Yes Im pretty sure that the water in the stairwell is the same as torus room water, because those stairs lead down to the floor level of the torus room (as opposed to the door they opened to look into the torus room, which is at least half-way up the torus room wall).

If neither the torus or the lower part of the drywell had damage then yes, we would expect to see much more water in the drywell, TEPCOs original drywell flooding plan would not have been abandoned. We can't use this to establish with certainty that the torus is damaged though because if the torus was intact but the bottom or lower walls of the drywell were damaged, we could still expect to see little water in the drywell and lots of water in the torus room.

As for the explosion at reactor 2, this has not been a safe assumption for a long time either. Firstly because the explosion at reactor 4 building happened around the same time, causing confusion, and later when they looked at local plant seismograph readings it looked like reactor 4 was the epicentre, not reactor 2. And the other reason they made a hasty assumption that the reactor 2 suppression chamber went boom, was because for many hours before the explosion they were afraid that the reactor 2 suppression chamber was in trouble. They knew its pressure & temperature was too high, but they failed in their mission to vent it, so they had to release more steam from the reactor into the suppression chamber anyway, because they were desperate to lower reactor vessel pressure so they could get some water pumped in. The site manager had already made plans for an evacuation, hours before the partial site evacuation actually took place. So with this in mind, its no surprise that when an explosive sound was heard and radiation levels on site climbed dramatically, they assumed the suppression chamber had failed.

And it may well have failed, all we can now rule out is that it failed in a manner where the torus was completely mangled, doors deformed etc.

The intriguing mysteries of reactor 2 only grow for me, because as we have seen from past surveys by humans & robots, there aren't the same sorts of highly contaminated areas at various locations within reactor 2 building that we see with reactor 1 (where various bits of equipment are well contaminated) or reactor 3 (where there were some very high levels of contamination to north-east and south-west of the drywell containment near to pipe penetrations and access doors). At reactor 2 we just have the highly contaminated water in the basement, and several hotspots on the refuelling level near to the concrete cap over containment, not much on any of the other reactor building floors with which we may gain clues about emission pathways.

Yamanote

Looks like a kind of unintended groundwater-corium-cooling-system to me. At least if any corium had reached the torus, it must have been cooled well by the groundwater inflow. Perhaps this is also one reason, why they keep the water level around OP 3000.

And if even the door to the torus room is damaged by the explosion in unit 3, I would expect severe damage inside the PCV too.

It will be an incredible effort to clean up this huge mess...

zapperzero

I will take this opportunity (the release of videos and announcement that survey work will begin in earnest there) to publicly plead with the moderators to unlock (or at least un-hide) the Unit 3 explosion thread. It's been quite a while, there is new stuff to discuss and I would like to at least have the old stuff available for reference.

MadderDoc

I do know you have been intrigued by unit 2, if I remember correctly, centered about the question why such a large proportion of total emissions is assumed to have originated from unit 2. To me otoh unit 3 has remained the most vexing (while nothing really earthbreaking, I do feel quite a lot of new information on unit 3 has been surfacing since the thread specifically dealing with the unit 3 event was suspended by the moderators, -- and which I would like to turn about with like minded souls, but alas.) Unit 2 is also an interesting subject :-)

I note that there's a rather straightforward radiation gradient down through the building along the staircase positioned in the NE corner of the service floor: that would seem to me to indicate strongly that airborne emissions from unit 2 escaped predominantly via the service floor. The exact route(s) it has taken from the RPV to the service floor is unclear, but it stands to reason that emission did pass through cracks and openings in and around the top concrete plugs.

Borek

Sadly, the thread got damaged and its content is no longer available. I have no idea what have happened. As far as I can tell it was not physically removed, as it is still on the list of soft deleted threads - but it is empty.

zapperzero

This is way beyond annoying. There was some good stuff in there, good sources that were cited. Perhaps some of it could be retrieved from Google cache, or from backups? There are backups, right?

zapperzero

http://www.youtube.com/watch?feature...HEQ7IP0#t=388s

An impromptu blow out ring!

EDIT: make that two
http://www.youtube.com/watch?v=zfohH...ailpage#t=404s

LATER EDIT: Whatever it was, it was not inside those pipes. They look pristine. The overpressure came from below, from the 2nd basement level. Curiouser and curiouser.

Borek

Question is - how long ago it happened. I don't know how long Greg keeps old backups, they are done to allow restoring the latest state in case of crash, not to keep track of everything that ever happened at forum. Besides, I doubt it is possible to restore just a single thread. But we will investigate, as it can be a sign of some serious problem.

zapperzero

There should be incremental backup. It's a serious problem if there isn't :D