from little they saw.
6 TEPCO workers entered the basements (mezzanine floor) of Reactors 2 and 3 buildings on March 14 to try to survey the damage in the Suppression Chambers. Max radiation exposure for the workers was 2.87 millisieverts. Expected dose was 10 millisieverts, but they seem to have gotten out of Reactor 3 rather quickly, spending only 8 minutes there as opposed to 20 minutes in Reactor 2.
From what Yomiuri reported (3/14/2012), about Reactor 2's basement:
No apparent damage as far as the workers could see;
Photos of the Suppression Chamber taken from a small adjacent room (window);
Radiation levels in the adjacent rooms were 20 to 35 millisieverts/hour;
Radiation levels near the Suppression Chamber were 130 to 160 millisieverts/hour;
Water in the 1st floor of the basement;
TEPCO will use robots for further survey, as the radiation levels [in the Suppression Chamber] were too high for humans.
Well wasn't that rather obvious that the radiation levels would be rather high? Why didn't TEPCO use Quince or Packbot? (TEPCO needs those swarming flying robots.)
Looking at the photos released by TEPCO, Reactor 2 Suppression Chamber looks more or less undamaged. The workers were supposed to take temperature and humidity measurements as well as radiation levels, but no information released regarding temperature and humidity.
Looking at the photos of Reactor 3 basement, they look highly humid. The workers apparently didn't, or couldn't measure the radiation levels at the door of the Suppression Chamber, like they did in Reactor 2.
From TEPCO's handout for the press in English (3/14/2012):
(Note: Date is wrong. It was March 14. The timeline is wrong. They entered Reactor 3 at 12:40 and exited from Reactor 3 at 12:48.)
The photos of Reactor 2 torus (red colored) taken from the adjacent rooms:
If the Suppression Chamber of Reactor 2 is not broken, where did all the radioactive materials from Reactor 2 come from?
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27 comments:
Try that again: the most interesting photo is of the bent door in reactor unit 3.
The door should be bent the other way if there was overpressure within the unit 3 containment.
Negative pressure within the torus room would be hard to imagine although the suppression pool would act as a condenser (isolation condenser as in unit 1). It is very strange ...
It would take a lot of force to bend the steel door that is closed in its frame, the door handle would break first.
It is also possible the door was propped open at the bottom before the earthquake. A shock wave from the 'inside' bent the door free from what held it, then the door-closer shut it afterward.
And that is supposed to be the torus? It looks more like a piece of piping or an air duct. The torus is massive and doesnt just hang there in a large empty space.
@anon at 12:49, no, not that shiny pipe. Look to the right. Blurry red thing, that's the torus. It's painted red.
@Steve, is it possible that the explosion sucked the air out of the suppression chamber, and the door caved in?
@Anonymous : the torus is not the silver colored pipe. it's the red mass on both photos, leaking on the right.
Can somebody explain how the hell you spend 44 minutes in an environment as high as average 30mSv/h, min 20 and take only 3mSv ????
The measurement device was probably tampered by tepco.
Maybe they were wearing tungsten armor.
I really don't think these photos show anything like enough to even begin to conclude that the torus is undamaged. There are many parts of the torus we cannot see, and there are forms of potential damage that will not look very exciting in photos anyway.
It was quite understandable that peoples attention was drawn to dramatic explosions and other things we can see with our own eyes when looking at the disaster, but when it comes to nuclear many of the nasty things that can happen are not going to be visually stunning.
For example although I do not rule out the possibility of explosions other than the reactor building ones we saw, I don't think people should be convinced that other explosions, such as suppression chamber ones or steam explosions, actually occurred. Its possible to have serious nuclear contamination without any of these things having happened.
As my lengthy comments to the older post about reactor 2 dry vent demonstrate, I am fascinated by reactor 2. I tried to learn more about the MELCOR model which was used to do theoretical analysis of the disaster, and come up with some of the estimates for radioactive release at the different reactors. The information I have learnt so far is not enough to 'reverse-engineer' their conclusions to establish what factors may have resulted in a higher analysis estimates for reactor 2 than the other reactors, but it was a start. Its possible that reactor 2 analysis was based simply on what was actually detected in the environment around that time, and their early assumption that the explosive sound came from reactor 2 s/c rather than reactor 4 building. Part of the reason they thought it came from reactor 2 is because for at least 8 hours before the 6am events of the 15th, they were worried about the state of the suppression chamber and its ability to survive the reactor steam release that they wanted to carry out. The partial site evacuation that happened on the morning of the 15th was planned hours earlier due to these concerns, the situation was bad enough that they expected trouble even sooner than it actually arrived.
Anyway, in future I would not be at all surprised to discover that there is suppression chamber damage at one or more reactors. But I would not be shocked if there isn't. Radioactive releases from the drywell due to a number of different failures are well known in accident planning studies, and can be a major source of radioactive release to the outside world.
And its worth noting that the torus room itself can be the scene of a number of dramatic containment failure events, quite separate to what the suppression chamber itself is doing. Blow-down of core material from the drywall to the torus room is featured in MELCOR, and this involves drywall shell failure rather than suppression chamber problems. Small or large hydrogen deflagrations can happen in the torus room. And if you have bad substances in the air of the torus room, some of them are expected to travel to other parts of the reactor building and then to the outside world, especially if high-pressure is involved, or the leakage is happening at the same time as core-concrete reactions.
f4eru the total exposure figures seem fine to me. They didn't spend 44 minutes in the buildings, and the time they did spend in the buildings also involved them being in other areas (such as stairs) which are not included in those figures.
Also sorry that sometimes in my posts it says drywall instead of drywell, there is a spelling correction thing active in my browser and it doesn't like drywell, and sometimes I don't notice that its changed it.
arevamirpal::laprimavera: What happened in the reactor buildings would be a good subject for fluid dynamic modeling. Tepco should have started this right after the disaster was underway, particularly with the controversy about the spent fuel pool and the 'hydrogen explosion' in reactor unit 4.
Tepco has blamed unit 4 damage on the explosion in unit 3 it is theoretically possible the explosion at the top of the unit 3 building bent a steel door below ground level the 'wrong way'.
This is beyond me, but what you suggest makes sense if there is gas movement on the other side of the door. The relationship of the drywell and the lower containment/torus space could have acted as a venturi, with the jet of materials out of the containment creating a strong draft/negative pressure at the bottom.
Unfortunately, the workers only went to one corner of the 1st floor, it would be interesting to see if the other doors are also bent or damaged.
Another interesting photo is of the loading platform of unit 4 taken shortly after the blow-up. The loading platform is at ground level but all the concrete side panels are blown out (white polygon at lower left):
http://www.pmw.de/pm_online/data/PCP_deutsche-betonpumpe-fukushima-504x378.jpg
Unit 3's door is bulged OUT towards the stairwell, not in towards the torus room. So there was pressure in the torus room/suppression chamber that was pushing out on that door. Likely during the blast at 3.
3's door opens inward. Doors at 2 open out into the stairwell. Why the doors open two different ways on the two units I don't know. Probably really doesn't matter but I noticed the difference going through photos earlier.
as elbows said, one can see only little (probably less than 5%) of the torus on these pictures (by the way, the bottom halve of the torus is embedded in the concrete floor), so one can not conclude anything about the integrity or failure of the torus at this moment.
But if the torus is really intact, I think the more interesting question is, where and how does all the water get out??? Because on the second picture of the Nr2 torus, the floor seems quite dry to me. This could indicate, that either the bottom side of the torus is damaged and the water is running through a crack in the concrete floor to the cellar (not so likely) or the water is reaching the cellar via a broken pipe higher up (e.g. one of the pipes that was feeding water into the reactor from the condensers during normal operations), surpassing the torus room completely.
I think if you can find the way how the water is reaching the cellar, you will find the answer to your question: '... where did all the radioactive materials from Reactor 2 come from?'
Im not sure quite what you mean because as far as I know the torus room IS the cellar.
I think it is quite a tall room to accommodate the size of the suppression chamber. And the door that they have looked through is actually about half-way up the total torus room height. Thats why there are more stairs leading down to a lower level, they lead to the door at the floor level the torus room. And the reason why they would have doors half-way up the torus room is because there are walkable platforms etc which go around some parts of the upper area of the torus, that humans would want to access sometimes.
Also I cannot see the torus room floor in any photos, and the lower staircase indicates deep flooding.
As to how the water is reaching the cellar if the suppression chamber/torus isn't damaged, well there are a number of possibilities. There are likely to be points in the roof of the torus room where stuff could come down from a higher level of the reactor building. But there are also several places where the drywell could fail which would lead to the torus room without having to go via the suppression chamber. When we think of all the pipes that connect the drywell to the suppression chamber, do not think only about the pipes. There is also the area where the pipes meet the walls & floor that they are travelling through, which offer the opportunity for stuff to travel from the lower parts of the drywell to the torus room. This is an example of what I mean when I talk of core blowdown from drywell to torus room, in cases where the drywell shell is melted by the corium in a certain place.
Anyway as discussed, because of the flooding and the lack of resolution & photos taken from many different angles and points, we can't really conclude that the suppression chamber did not play a significant part, but we should still consider the role the torus room could have played in theory, independent of a problem with the suppression chamber itself.
I do not get.
In R2 tour you see (central photograph up) the orange railing of the stairs immersed in water at the bottom, left side.
If the stairwell is flooded with water ---as I think---, (the first steps are very rusty), how did they get out and take pictures of that portion of torius?
typo: get out=> downstairs
# 2:
The picture of the man scouting the radiation suggests the outward-opening door blew open (btw, this safety flaw could have possibly been the reason why the door of #3 opens into the torus room).
The image (2) of the torus could be particularly interesting.
What is the white stuff, what is the oil-like distributed liquid? (To me it looks more like oil or hot grease creeping instead of water.)
(direct link to image http://www.tepco.co.jp/en/news/110311/images/120314_07.jpg )
# 3: The image of the door:
When looking at the part below the interlock, I get the impression that it got bent towards the torus room after being pushed toward the stairwell.
If I see correctly, could this have been caused by the vacuum that follows a hydrogen explosion when the over-heated steam produced by the reaction quickly condensated?
(direct link to image: http://www.tepco.co.jp/en/news/110311/images/120314_11.jpg )
Sadly the images are very small, in contrast to the hi-res pics we get from things that are way less interesting. Does Tepco want us to see only unclear images?
@ f4eru
It always is also very useful to put the dosimeter in chest height when the radiation is expected to be more concentrated at floor level than in air.
@ elbows
Agree. As long Tepco hasn't told us why they are so sure almost from beginning of the Fuku thing that most of the nasties emanated from reactor 2, in doubt we have to treat this statement as baseless rumor.
Actually it might be not worth any more than my unsubstantiated feeling that will find out in some years that there actually was no melt-through at all.
Well a melt-through would not surprise me, but I think you can get bad contamination without one. There are plenty of areas where containment can fail for other reasons, and if containment breaks at the same time as it is under pressure then I imagine plenty of stuff could be released.
Mind you it obviously also depends exactly what people interpret a melt-through to mean. As far as I can tell the bad thing about a melt-through of some kind is not just about part of the core escaping, its what happens during the core-concrete reaction. Studies suggest that rather a lot of substances form during this process, substances which could then go on to escape the drywell via air. Sometimes people spend too long looking down instead of up, or looking for explosions instead of less dramatic leaks or flows of material.
Is there a possibility that the bent door of unit 3 was damaged in the earthquake? If the building flexed or shifted I wonder if it might not have put pressure on the door and caused it to squeeze or fold a bit.
-WM
The bent door to Unit 3's torus room got me thinking about how much overpressure could have caused it. Assuming the door is about 2m tall by 1m wide (or about 6.5ft by 3.5ft), the area of the door would be about 3,042 sq. in. An overpressure of 1 kilopascal (0.15psi) would be a force of about 300 lbs when multiplied by the area of the door. That looks too small, as one NFL lineman could probably not cause that much damage to an ordinary (i.e. not blast-proof) steel door. 10 kPa (1.5psi) would be about 3000lbs. 100 kPa (15psi or 1 atmosphere) would be about 30,000lbs or 15 short tons. 100kPa looks like it is too much and 1kPa too little. So, order of magnitude around 10kPa. However, was this due to the hydrogen explosion? Looking at the rest of the building, 10kPa (1.5psi) looks like it is way too small an overpressure. 100kPa is more like it. According to the source below, overpressures could be as high as 500kPa (72.5psi). To snap thick concrete columns like twigs and reduce Unit 3 to a pile of rubble, an overpressure on the order of 500kPa seems more likely. However, 500kPa at the door would be a force of about 220,000lbs (100 metric tons) - no way the door could still be standing.
So, was the explosion that bent the door different than the one that leveled the building? Could the door have been bent by comparatively smaller steam explosions from hot corium falling into wet concrete or something like that? If so, maybe the models are wrong in estimating that 90% of the radioactivity that escaped came from Unit 2. It looks more logical, when thinking about breached containments, that the one that looks like a pile of rubble on the surface and that has evidence of a sub-ground explosion was the one responsible for the majority of the contamination (i.e Unit 3).
1. http://products.construction.com/swts_content_files/1486/P14504.htm
Sorry. Wrong reference. Use this:
1. http://vgr.ing.unipi.it/ichs/images/stories/papers/254.pdf
@ anon 5:06
The torus floor is so high that it actually is two floors, as somebody earlier mentioned. Only the upper one has been accessed.
@ anon 6:54
No cracks in the concrete walls visible, this indicates that this cannot be the case.
@ anon 1:04
Actually there are many possible scenarios in discussion, many of them assuming a lower-energy explosion/deflagration in the lower building parts that triggered the explosion in floor 5 which resulted in spectacular wreckage and a scary webcam video.
I think your approach can really be helpful estimating how large the pressure energy at the door had been. But we also have to keep in mind that a more distant explosion could have been the cause, which shockwave got dampened on its way to the door so that it didn't pop open.
I think we only can speculate until a forensic examination of the torus room is possible.
@ elbows
Yes, I mean with "no melt-through" that the corium has been contained in the RPV. I have this feeling somehow "intuitively" even if this seems very improbable in sight of the extreme temperatures.
But a melt-through through the concrete seems extremely improbable to me, given the more than seven meters of pedestal thickness.
And somehow I think ~100 millisieverts would be a very low radiation in a room where large corium quantities were dripping.
So my feeling says to me, if any corium left the RPV, most of it will have stayed on the drywell pedestal.
But this all is speculation for now.
i wonder if someone can do a spatial wikipedia for the fukushima nuclear station, tie all the pepco releases into models so you can click and see the survey data.
@Atomfritz
Cheers for the reply. I don't think there are many possibilities we can completely rule out. I do struggle a bit to imagine the majority of the core still being in the reactor vessel given the length of time that they failed to inject water reliably, but I have no way to even guesstimate what percentage of the core may have left the reactor.
When it comes to what happened if the core left the reactor vessel, a lot seems to depend on the way it came out. If it slowly dribbled out then this would have different implications for the drywall than if a large percentage of it fell out quickly in a big mass.
For example the core blow-down into the torus room which I mention, does not require the corium to eat through many meters of concrete. Rather the assumption is that if a sufficient mass of corium landed on the drywell floor quickly, and it was of a high enough temperature, it can travel horizontally along the drywell floor until it reaches the beginning of the side wall of the drywell. There it just needs to penetrate the steel liner, and fall through gap down into the torus room.
And its not necessarily a large percentage of the core that needs to make this journey, only a small amount could end up in the torus room, creating the pathway, and the rest of the nasty stuff that then enters the torus room does so via air/aerosols.
I agree that the detected radiation levels in the torus room don't seem ridiculously high, but Im unsure to what extent the meters of water in the torus room would act as shielding if, for example, a percentage of the core was lurking at the bottom of the torus room.
On another note, apart from the basement areas and points either side of the reactor refuelling floor where the concrete plugs sit above the containment cap, radiation surveys of reactor building 2 don't tend to show really high levels of contamination, unlike reactors 1 & 2, so not many clues about what path the highly radioactive substances may have taken within the building. Whereas at reactor 1 they find high elves of contamination near certain equipment on a few different floors, which allows them to talk about how substances may have flowed through various systems. And at reactor 3 building we see higher levels of contamination to the north-east and south-west of containment, near drywell equipment hatches & pipe penetrations. These are interesting parts of the puzzle but I don't think I can do much with them until more pieces of the puzzle are in our hands,which could be a long wait.
I wait with interest to see what the next reactor 2 endoscope mission reveals, can at least hope they will find the water level (or a complete lack of water in drywell) as the last endoscope mission showed that their assumptions about this were wrong, but we don't yet know how wrong.
Sorry for the mistake in my last post, at one point I mentioned reactors 1 & 2 but I meant to type 1 & 3.
Anonymous, the door is a mystery. Apparently (according to an NHK report) the door could not be opened. Was this b/c of a broken latch or b/c there is something behind the door? Nobody knows what the entire suppression pools/toruses look like.
I was trying to make the same calculations but with bars rather than kPcs. .100 bar is inside an EF3 tornado (according to Wunderground) which is a very large differential, then add the overpressure elsewhere INSIDE the containment. Nobody is going to convince me that the unit 3 explosion didn't take place deep inside the reactor building.
The 'floors' that were explored are small mezzanines, there are four of these in each building, one at each corner. The entire torus space is about 6 meters tall. The mezzanines are about half-way down to the basements.
The way Tepco conducts its business I would not be surprised that workers had wedged the door open while doing some sort of minor maintainence (which would be a massive safety violation as the reactor was operating at full power. It would mean that the negative pressure inside the reactor unit was not working/switched off.)
A blast wave from inside the reactor would easily bend the door if it was open and propped against something. The force of the blast (or the door closer) would slam the door against the jamb. Otherwise, that door is probably almost impossible to bend by any person: too heavy and rigid with fire-resistant material within the door itself.
The entire reactor building is probably out of square due to the force of the earthquake AND the explosion. It may be that none of the doors open within that reactor building.
An explosion could indeed take place inside the torus and not cause much destruction nearby. There might be a split seam at the top of the torus with a very small hole in the concrete overhead. It is also possible that the blast took place inside the torus w/ the force 'feeding back' though the downcomer vents, into the drywell and past the bioshield plugs and reactor dome.
Whatever happened included some reactor fuel, so something melted and was blasted out of the reactor, either SFP or the core, itself.
Hmmm ... door. What would Homer Simpson think ...?
Maybe the dosimeter badges were wearing armor... probably more important to Tepco to avoid bad press than to protect workers.
Now videos are available for download on the press handouts page ( http://www.tepco.co.jp/en/news/110311/index-e.html ).
I just do not understand it.
They rush through without really caring for potential radiation fields around corners etc.
Almost looks like if they only pretended to check for radiation fields. As if they already knew.
Like bad actors in a bad movie.
And: It's full of temporary installations.
Plastic tubing, cabling, scaffoldings and apparatuses around practically immediately before the stair down to the torus room upper entrances.
I somehow have difficulties to believe nobody scouted there before. It's just a few steps away from where they installed all that makeshift stuff.
To be honest, to me these videos leave a bad aftertaste of possibly being staged. I just can't help it.
Maybe Tepco seems to know much more than they admit and tries making us to believe that they are clueless.
Semi-OT:
Virtual nuclear plant tour:
Look inside a Mark-I torus:
1. Go to http://zwentendorf.com
2. Click "Rundgang" in the upper bar on the page
3. Flash window pops up, click link "Zum virtuellen 360 Rundgang" in middle of window
4. Click at "Kondensationskammer" (=suppression chamber) in the right menu
5. Drag mouse to change view
This is an authentic S/C of the Fukushima type like in Reactor 2-4.
Images taken in the safest NPP of the world.
Zwentendorf NPP in Austria, never got critical due to a referendum.
Other panoramic views available via right menu.
Enjoy :-)
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