Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[SteveElbows]

But that the containment was leaking after the explosion is obvious, for example "www.youtube.com/watch?v=iV_r5Ifp8-I&hd=1#t=44s" . What one has to consider is that probably after the blast, melting fuel kept off gassing and more corium kept forming, boiling water ever-more vigorously and thereby increasing the pressure.

The containment was not blown wide open, just enough small leak paths were blasted open to have allowed a mushroom-cloud of steam to escape in an instant of sudden explosive force. After the explosion, the force propelling depressurization falls and pressures build back up as corium keeps off gassing and boiling water.

Yeah, Id go along with that, although I am somewhat suspicious of the quality of various measurements too.

 

[SteveElbows]

They did vent reactor 3 again several times (or at least once) after the explosive event didn't they?

 

[MadderDoc]

Cheers.

On first viewing, videos 3 & 5 offer us some views that were not apparent from the previously released photos.

Has anyone been able to identify any of the debris we see in the 5th video?

Yes, we are again seeing parts from the NW corner of the FHM bridge, corresponding to the part closest to Quince in this photo of FHM2.
http://photo.tepco.co.jp/library/120228/120228_02.jpg

The FHM3 is quite similarly built, but as westfield notes it is not identical. A relevant difference here is that the FHM3 bridge has extra diagonal reinforcement beams built into the bottom section of the northern face of the bridge, as shown in this video (at about 2:25)
http://video.sina.com.cn/v/b/48514912-1822430771.html

The identifiable parts which we have seen of the FHM appear to be no longer attached to each other, nor to other parts to which they were attached. Separation appear to have occurred by breakage of interlinking bolts. I fear we will find this FHM to be thoroughly broken up and fubar.

 

[jim hardy]

But there's also the possibility that the sensor, as so many others, already went to hell at that point.

one wonders what were they using for pressure indication? Got to put ourself in their shoes at the time:

we speculated at the time that with no electric power it was likely a mechanical pressure gage on the fire truck pumping into reactor that they used, hence readings would reflect the pressure drop along piping connecting the two. They'd be high when there is flow and accurate only at no flow. Operators would know to reduce flow to get a true reading, but the poor guy who's copying numbers for the record might not be so savvy. "Just read this gage and write it here every fifteen minutes"

I seem to remember looking at JStolfi's remarkable graphs and seeing correlation between flow and pressure. But that was a year ago.. don't trust my memory, 'cause i dont.

 

[MadderDoc]

<..>
Containment pressure did fall after the explosion, but it rose again to higher levels. Not the behaviour I'd expect from a leaking containment. But there's also the possibility that the sensor, as so many others, already went to hell at that point.
Taken from:
http://gyldengrisgaard.dk/fukmon/uni3_monitor.html

Those are earliest published data, and not the best available. Since then Tepco has assembled better and more complete data sets,
which yields better insight also in the period around the unit 3 explosion:
http://www.tepco.co.jp/nu/fukushima-np/f1/images/syusei_level_pr_data_3u.pdf

The impression of a rather sudden pressure drop concurrent with the explosion remains, however.

Data indicate to me that leading up to the event there was no longer any clear barrier between the atmosphere of the RPV, and the atmosphere of the primary containment. The whole system was well past design limits, the core was in the process of melting down, and the primary containment was probably already leaking to some degree. The sudden pressure drop in connection with the explosion is consistent with an assumed abrupt increase in leak area, resulting in a blow out of hydrogen and steam. One would expect such a blow out to be decreasing over time, as accumulated energy is being released from the system. In the case of unit 3, a rather vigorous evolution of steam was seen right after the explosion at 11 am, however this steam evolution swiftly subsided to become invisible before noon. (Only later in the afternoon unit 3 resumed steaming, apparently coincident with a renewed build up of pressure within the containment)

 

[jim hardy]

One would expect such a blow out to be decreasing over time, as accumulated energy is being released from the system. In the case of unit 3, a rather vigorous evolution of steam was seen right after the explosion at 11 am, however this steam evolution swiftly subsided to become invisible before noon. (Only later in the afternoon unit 3 resumed steaming, apparently coincident with a renewed build up of pressure within the containment)

indeed if water that's pumped in as liquid comes out as steam through a constant leak area, one would expect strong flow^2 relation to pressure.

 

[zapperzero]

It's heartening to see discussion of this topic, but also frustrating to know that the dedicated thread is lost. I wonder if the FHM really is in pieces. It wouldn't be much of a surprise if it were so, as it takes a lot of force to crumble concrete into small pieces like that.

It seems as if the #3 RPV was leaking hydrogen and steam at a fairly rapid rate even before the explosion. I was very skeptical regarding the theory of hydrogen going from Unit 3 into the others, but I am almost convinced, now.

 

[SteveElbows]

we speculated at the time that with no electric power it was likely a mechanical pressure gage on the fire truck pumping into reactor that they used, hence readings would reflect the pressure drop along piping connecting the two. They'd be high when there is flow and accurate only at no flow. Operators would know to reduce flow to get a true reading, but the poor guy who's copying numbers for the record might not be so savvy. "Just read this gage and write it here every fifteen minutes"

I find it unlikely that this was the source of pressure readings, since readings at various reactors were taken at moments when fire-trucks for reactor water pumping were not available, and we also have drywell and wetwell pressure readings.

Batteries were used to power existing instrumentation.

 

[Yamanote]

The latest plan for the fuel removal of unit 4 is now available:

http://www.tepco.co.jp/en/press/corp-com/release/betu12_e/images/120416e0201.pdf

 

[Yamanote]

And there are also some videos of SFP #3:

http://photo.tepco.co.jp/en/date/2012/201204-e/120416-02e.html

 

[tsutsuji]

http://www.tepco.co.jp/nu/fukushima-np/images/handouts_120416_04-j.pdf report on the recent nitrogen injection system failures (pressure swing adsorption)

http://www.tepco.co.jp/nu/fukushima-np/images/handouts_120416_03-j.pdf report on the recent contaminated water leak after reverse osmosis

http://www.tepco.co.jp/nu/fukushima-np/images/handouts_120416_02-j.pdf report on unit 4 SFP cooling system leak

http://www.tepco.co.jp/nu/fukushima-np/images/handouts_120416_05-j.pdf The plan to remove the remaining part of unit 4 reactor building roof

 

[Tepconium-311]

These posts made me think of a scenario.

If it did so before the FHM fell, was it thrust at an almost horizontal angle like a javelin?

Then the explosion-like sudden decompression can be excluded...
...I think small leak paths would not be enough for that big mushroom cloud. An overheated RPV would, but small leaks wouldn't.

I find it unlikely that this was the source of pressure readings, since readings at various reactors were taken at moments when fire-trucks for reactor water pumping were not available, and we also have drywell and wetwell pressure readings.

Readings were manually taken in intervals, yes?
Then it would be unlikely that explosion pressure/vacuum spike was recorded, right?
Could we then actually really exclude existence of such a spike?

And now my questions:
Could there have been a pressure surge ("explosion") in RPV/drywell which lifted concrete reactor seal a bit for a moment, propagating hydrogen explosion from drywell to maintenance floor 5, so pressing reactor concrete seals back into place, mostly undamaged except two or three points ("white steam leaks")?
If so, wouldn't pressure wave have been directed in a way that would lift up FHM from below sideways, and then push it horizontally like a javelin into the pool?

 

[thebluestligh]

These posts made me think of a scenario.
Readings were manually taken in intervals, yes?
Then it would be unlikely that explosion pressure/vacuum spike was recorded, right?
Could we then actually really exclude existence of such a spike?

And now my questions:
Could there have been a pressure surge ("explosion") in RPV/drywell which lifted concrete reactor seal a bit for a moment, propagating hydrogen explosion from drywell to maintenance floor 5, so pressing reactor concrete seals back into place, mostly undamaged except two or three points ("white steam leaks")?
If so, wouldn't pressure wave have been directed in a way that would lift up FHM from below sideways, and then push it horizontally like a javelin into the pool?

The AEC transmitted a scenario where the head bolts stretched, which GE didn’t think was what happened.

"All the three units (IF] -3) experienced containment overpressure in the early phase of the accident, which caused excessive leakage from flange, ailocks and other peentrations. Hydrogen produced by Metal Water reaction in the core damage process must have escaped to the reactor building via this containment leakage path and accumulated on the top and caused deflagration/detonation there. Further, containment was steam inerted and a large fraction of hydrogen escaped -by “hardened” venting."

http://www.scribd.com/doc/89386167/AEC-Hydrogen-Analysis-Pages-From-C142015-02B

 

[SpunkyMonkey]

I think small leak paths would not be enough for that big mushroom cloud. An overheated RPV would, but small leaks wouldn't.

How does an overheated RPV allow the big mushroom cloud to escape? Assuming just leaks, a steam explosion in the containment would force out a larger amount of steam than the slower steady lease from just boiling water. Imagine a plastic bottle you can squeeze and there's a steam generator in it with a steady amount of steam ejecting from leaks in the bottle. Then you suddenly squeeze the bottle with great force (simulating the explosion) and poof, a much bigger dose of steam shoots out the same leaks. No?

That aside, in "www.youtube.com/watch?v=VZoBb-8oxdg&hd=1" , the well cap is assumed to've been momentarily lifted, which is denoted as it falls back in place.

 

[Rive]

How does an overheated RPV allow the big mushroom cloud to escape?.

I mean: if all (or: most) of the overheated and pressurized water in the RPV is suddenly released (through a BIG hole) then it would be more than sufficient explanation for the secondary, mushroom-like cloud.

Just (relative) small leaks could not be able to carry out the necessary energy I think.

To turn it around: if that cloud were from the RPV then the release path would not be able to close itself and keep a relative high (or even just any over-) pressure after the explosion.

One more turn: I think we should assume that the energy of the secondary mushroom was also based on chemical reaction, and not on (or at least not mainly on) steam explosion.

(Sorry for my English.)

Ps.: Another possible explanation is that after the primary hydrogen explosion the escaping steam/hydrogen mixture burned for some seconds. That would require just a relative small hole, but it also would mean sufficient energy for a mushroom.

 

[MadderDoc]

I mean: if all (or: most) of the overheated and pressurized water in the RPV is suddenly released (through a BIG hole) then it would be more than sufficient explanation for the secondary, mushroom-like cloud.

I can see the need for a hole of a certain size, but not why it would have to be a hole in the RPV. A hole in the primary containment would seem quite fine for the job seeing the containment contained the main portion of the overheated water in the system. Indeed pressure readings indicate that the pressure in the PCV was higher than in the RPV leading up to the event. That could indicate that there was already a big hole connecting the RPV and the PCV, meaning any sudden leak to the upside would tap from both sources.

Just (relative) small leaks could not be able to carry out the necessary energy I think.

To turn it around: if that cloud were from the RPV then the release path would not be able to close itself and keep a relative high (or even just any over-) pressure after the explosion.

Perhaps we could have some reason to not trust the accuracy of the readings after the explosion? One failure mode could be the drying out of reference legs, which would if I understand result in faulty (too high) readings.

One more turn: I think we should assume that the energy of the secondary mushroom was also based on chemical reaction, and not on (or at least not mainly on) steam explosion.

(Sorry for my English.)

Ps.: Another possible explanation is that after the primary hydrogen explosion the escaping steam/hydrogen mixture burned for some seconds. That would require just a relative small hole, but it also would mean sufficient energy for a mushroom.

Considering the state the reactor was in, it stands to reason that any steam release from the containment could have included hydrogen possibly available for combustion, thus (only) adding heat to the mixture in the cloud. However, there would seem to me to be quite sufficient energy contained in the overheated water in the RPV/PCV, so I think perhaps it is an unnecessary assumption to make that combustion of hydrogen in the rising cloud played a significant role for its evolution.

 

[SteveElbows]

They have a different kind of robot which they are going to use to survey more of the torus of reactor 2 on the 18th:

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120417_03-e.pdf

I note that the building layout diagrams showing where it will go have a bit more detail than the ones they normally use. The resolution is barely good enough to read the labels but quite a number of them can be worked out if you zoom in on the pdf.

 

[jim hardy]

This INPO report from last November may be of interest to newcomers.

http://www.nei.org/resourcesandstat...t-the-fukushima-daiichi-nuclear-power-station

A Unit 3 timeline begins on p91 (that's p91 of the report which is p94 of the PDF).

It appears they were trying to lower primary containment pressure by venting in the hours before the explosion.

 

[tsutsuji]

They have a different kind of robot which they are going to use to survey more of the torus of reactor 2 on the 18th:

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120417_03-e.pdf

I note that the building layout diagrams showing where it will go have a bit more detail than the ones they normally use. The resolution is barely good enough to read the labels but quite a number of them can be worked out if you zoom in on the pdf.

I appreciate the fact that the sump pits are shown on the right hand diagram. It enables to narrow the possible locations for the pedestal opening ("slit").

 

[Yamanote]

Indeed, pretty cool and detailed drawings this time, would like to walk through the plant to see how it looks in reality! Years ago I did such kind of drawings for other types of big industrial plants, but I have never been to an NPP.

 

[tsutsuji]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20120418/index.html On 18 April the robot will do such things as inspecting from the catwalk the vicinity of the inspection manholes, where it is possible that there is damage, or measuring the surroundings' radiations.

 

[SteveElbows]

Two images from the robot, showing manhole covers:

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120418_04-e.pdf

 

[SteveElbows]

The press photo page version of those images include some radiation detection levels:

http://photo.tepco.co.jp/library/120418_02/120418_11.jpg

http://photo.tepco.co.jp/library/120418_02/120418_12.jpg

 

[Cire]

I have seen quite a bit of speculation that there is a large vertical crack in thereactor pressure vessel (RPV), but cannot figure out how they could tell. There has been no entry of the Dryell (Primary Containment) due to rad levels and I am not aware of cameras that would survive longtime exposure in the drywell during normal operations and they certainly haven't installed cameras since the accident. If pressure was high enough to cause a break it would likely occur in piping or rod penetrations of the RPV. Breaches due to core melt would be on the bottom of the vessel. It just doesn't seem to me that a vertical crack in the RPV can be any more than speculation.

At least I hope so.

There are many more easier ways to fail the interfaces to the RPV then to crack the actual containment vessel. I think we'll find failed piping and as you mention rod penetrations etc and a mostly intact RPV.

Just my guess.

 

[tsutsuji]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20120418/index.html [unit 2] On 18 April, the robot checked 90% of the upper part of the suppression chamber but until now no major damage or deformation was found. The north and south inspection manholes were checked but water leaks or traces of leaks were not found, and they looked comparatively clean. Otherwise, Tepco says that leaks might be located in the parts that connect the PCV and the suppression chamber, but their status has not been checked yet and Tepco has yet to analyse the pictures taken on 18 April. The highest radiation was 120 mSv/hour in the north-western region. Saying that "It is a high value, but it is still possible to plan short time human operations for important tasks that cannot be performed by robots", among other things, Tepco is taking the necessary steps to grasp the radiation distribution.

 

[LabratSR]

I stumbled across this on the TEPCO Photo page.

General Plan and Start of Main Work of the Cover for Fuel Removal of Unit 4

http://www.tepco.co.jp/en/press/corp-com/release/2012/1201934_1870.html

 

[Rive]

Regarding the radiation in the torus room: would it reduce the airborne radiation if they cover the water surface with oil?

 

[MadderDoc]

These posts made me think of a scenario.
Readings were manually taken in intervals, yes?
Then it would be unlikely that explosion pressure/vacuum spike was recorded, right?
Could we then actually really exclude existence of such a spike?

Right, we have no continuous recordings, and not even a lot of discrete readings. Strictly the pressure readings we have can only say that the reactor pressure in unit 3 appeared to be lower after the event than it did before.

And now my questions:
Could there have been a pressure surge ("explosion") in RPV/drywell which lifted concrete reactor seal a bit for a moment, propagating hydrogen explosion from drywell to maintenance floor 5, so pressing reactor concrete seals back into place, mostly undamaged except two or three points ("white steam leaks")?

I hope you don't mind some correction in terms of understanding. The RPV/drywell/wetwell,( in short the reactor) of unit 3 is strictly a steel container, it is nowhere sealed with concrete. It's got interesting things inside it, and it has an interesting shape, but looked at from the outside one must visualise it as a mere steel container, having a closed surface made of steel. A leak in it implies there's a hole in that steel surface.

However true enough there's concrete packed up all around the reactor, for support, for radiation shielding, and for making the building structures around it, but none of all that concrete is there to keep the reactor tight. Specifically the concrete slabs stacked on top of the reactor, which I think you are referring to, are not there to keep any pressure at bay. You should, in principle, be able to operate the reactor quite well without them. So, to get back to your point, an assumed falling back of those top concrete slabs after an explosive pressure surge from the reactor could not be assumed to reseal the hole in the reactor below, from which that pressure surge would have to be coming from.

If so, wouldn't pressure wave have been directed in a way that would lift up FHM from below sideways, and then push it horizontally like a javelin into the pool?

The hall mark of the unit 3 explosion is exactly the vertically rising cloud over the building. It stands to reason that this vertical rise represented a considerable upwards mass flow over a short period. Anything that stood in its way should have experienced the impulse. So I can well imagine your scenario, it is possible that the FHM was lifted up/sideways. Only from what I have seen of the FHM it appears to be more beaten up than I'd expect if it had been just pushed sideways into the pool.

 

[Rive]

This might be relevant regarding U3 explosion: http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120419_03-e.pdf

 

[SteveElbows]

This might be relevant regarding U3 explosion: http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120419_03-e.pdf

Aha, very interesting.

Its not terribly surprising given that we have previously seen attention paid to high radiation levels from the rail on the floor in front of this equipment hatch.

( Last november http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111122_02-e.pdf )

However I do not recall Tepco talking about the 'crevice between shield plug and reactor building' before, so I think this new information is only going to increase suspicion that TEPCO do not reveal every detail as soon as they discover it.

My knowledge is not sufficient to judge whether this damage would occur due to explosion (e.g. explosion within containment) or whether damage to seals due to heat or pressure would be sufficient to cause such a gap & leak.

 

[SteveElbows]

My other question is whether this shield plug has moved considerably away from the position that it is supposed to be in. Is it supposed to be so much further away from containment than the rest of the containment wall? (i.e. in photo it is much nearer to camera than the rest of wall, is it supposed to be flush to wall?)

 

[MadderDoc]

My other question is whether this shield plug has moved considerably away from the position that it is supposed to be in. Is it supposed to be so much further away from containment than the rest of the containment wall? (i.e. in photo it is much nearer to camera than the rest of wall, is it supposed to be flush to wall?)

As I understand it, the backside of the shield plug is not meant to be flush with the wall, but there is not supposed to be so much of an opening (the 'crevice') between the wall and the shield plug as there is now, so the shield plug is not in place, and appears as pushed out a bit from some impulse from inside the hatch.

BTW, if there is currently an active leak of water from somewhere in PCV flange of the hatch, as the wet floor inside the hatch could indicate, would that mean the PCV of unit 3 is water filled to that level?

 

[Rive]

BTW, if there is currently an active leak of water from somewhere in PCV flange of the hatch, as the wet floor inside the hatch could indicate, would that mean the PCV of unit 3 is water filled to that level?

IMHO not necessarily. In U2 PCV the water level is low, but everything is wet and there is heavy 'rain' inside. A small leak can catch enough water to keep wet those rails and areas even if it's not under water if the 'weather' is any similar in U3 PCV.

Ps.:

By the way I am quite impressed with the quality of the video from the robot that did the reactor 2 torus room survey, good detail & well lit.

It'll be perfect for steam hunting :-)

 

[SteveElbows]

BTW, if there is currently an active leak of water from somewhere in PCV flange of the hatch, as the wet floor inside the hatch could indicate, would that mean the PCV of unit 3 is water filled to that level?

Not sure, would need to know something about leak rate. As we saw from video inside reactor 2 containment, water injection/spraying can cause a lot of droplets of water to be dispersed quite widely inside containment. Failure to get inside torus room at reactor 3 doesn't help build a picture either.

By the way I am quite impressed with the quality of the video from the robot that did the reactor 2 torus room survey, good detail & well lit.

http://photo.tepco.co.jp/en/date/2012/201204-e/120419-01e.html

 

[SteveElbows]

As I understand it, the backside of the shield plug is not meant to be flush with the wall, but there is not supposed to be so much of an opening (the 'crevice') between the wall and the shield plug as there is now, so the shield plug is not in place, and appears as pushed out a bit from some impulse from inside the hatch.

If I take the diagrams they used literally, then its been seriously displaced. We see from both the main floor plan and the smaller diagram that either side of the outer shield plug, the wall comes out at at approx 45 degree angle, so the 'frame' around the plug sticks out compared to the rest of the wall. But the shield plug is currently well beyond this, perhaps as much as a meter or so away from the frame?

 

[MadderDoc]

Aha, very interesting.

Its not terribly surprising given that we have previously seen attention paid to high radiation levels from the rail on the floor in front of this equipment hatch.

( Last november http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111122_02-e.pdf )
<..>.

Those rails might be what the shield plug is traveling upon, cf.the floorplan of Unit2 which is showing the hatch in the open position:

The PCV hatch we are talking about would seem to be large opening seen to the right at the equator of the PCV bulb in that never-boring photo of a BWR reactor during construction before it gets dressed up in concrete:

 

[SteveElbows]

The more I look at the photo, the more I think that plug should be flush with the frame part of the wall.

This is because you can see behind the ladder the part of the wall that is at about 45 degrees, which to me means that the wall to the left of the ladder is the frame part that's supposed to be about flush with the plug.

 

[SteveElbows]

Those rails might be what the shield plug is traveling upon, cf.the floorplan of Unit2 which is showing the hatch in the open position:

Yes I think this fact was fairly well discussed at the time that the rails (& attempted cleaning of rails) was news.

 

[MadderDoc]

If I take the diagrams they used literally, then its been seriously displaced. We see from both the main floor plan and the smaller diagram that either side of the outer shield plug, the wall comes out at at approx 45 degree angle, so the 'frame' around the plug sticks out compared to the rest of the wall. But the shield plug is currently well beyond this, perhaps as much as a meter or so away from the frame?

Agreed, it seems to be displaced quite a lot more than a bit :-)

 

[SteveElbows]

The PCV hatch we are talking about would seem to be large opening seen to the right at the equator of the PCV bulb in that never-boring photo of a BWR reactor during construction before it gets dressed up in concrete:

No, I think that opening is on the opposite side to the equipment hatch we are talking about today. Look at where the personnel airlock is on that photo (equator).

Anyway I have been looking again at the photos and videos from November that showed robots cleaning the rail areas.

I am still a bit uncertain as to how everything should look under normal conditions. For example looking at images at left of page 2 of this document:

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111105_02-e.pdf

It seems that the equipment hatch itself has some thin doors. Both of these doors were open in first photo, but they managed to shut the right-hand one in second photo. This is confirmed by another photo on page 4.

So now I am not sure if this entire structure has moved, or whether the plug part that moves on rails is behind these doors (and structure that sticks out is a kind of porch).

Then look at this document:

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111122_02-e.pdf

First image on page 2 shows that this structure is at an angle, not 90 degrees to the floor. Can see probable hinge for the thin doors that I mention above.

Also if TEPCO diagram of radiation detection points has point very close to where equipment hatch should be at normal time, so either diagram is lying or it hasn't really moved forwards like I suggested before.

So I think its quite easy for me to make a mistake when looking at this stuff, really could do with seeing photos of how equipment hatch of this type should look under normal conditions, but equipment hatch pictures we have seen at other sites are very different so not much help.

 

[SteveElbows]

OK I have figured out my above confusion.

There is an additional white box that has doors on it, that is in front of the main shield plug that we saw in todays photo. It is further to the left, so cannot be seen much in that photo, but it is visible in the cleanup photos which I mentioned in previous post.

Check out the following video at about the 7 minute mark, and it becomes very clear, because we can see both this protruding porch that has doors on it, and the much larger shield plug that is behind it. The grey box with black wire duct that goes upwards and then left can be seen in todays photo and that video, thus making sense of the whole thing.

http://www.tepco.co.jp/en/news/libr...368209002&bclid=59370327002&bctid=59374639002

 

[MadderDoc]

<..>

There is an additional white box that has doors on it, that is in front of the main shield plug that we saw in todays photo. It is further to the left, so cannot be seen much in that photo, but it is visible in the cleanup photos which I mentioned in previous post.

Check out the following video at about the 7 minute mark, and it becomes very clear, because we can see both this protruding porch that has doors on it, and the much larger shield plug that is behind it. The grey box with black wire duct that goes upwards and then left can be seen in todays photo and that video, thus making sense of the whole thing.

http://www.tepco.co.jp/en/news/libr...368209002&bclid=59370327002&bctid=59374639002

Thanks, well done! So the plug has in fact moved considerably.

 

[SteveElbows]

Well, I don't think anything I've said or shown proves this conclusively. Maybe its supposed to stick out of the wall like that, but I have serious doubts about that.

Sadly it may be hard to learn more unless some journalists actually notice this news and ask the right questions. Or someone who knows what that hatch is supposed to look like talks.

I am somewhat amused that the websites that like to do big scary headlines and poor analysis of Fukushima disaster don't seem to have noticed this stuff, maybe there is a flashing light or some weather on a camera that is distracting them.

 

[tsutsuji]

If this big plug was moved, how ? Earthquake or explosion ?One more unit 2 thermometer is broken :

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120419_04-e.pdf We evaluated the reliability of the thermometer (RPV bottom head 135°) which was monitored for reference based on safety regulations 138 through direct current resistive measurement. We evaluated the thermometer broken down based on the increase in direct current resistance. No large swings confirmed at other thermometers, monitoring posts, and PCV gas management system indicators. We will continue monitoring PCV temperature by thermometers (RPV bottom upper head 270°and RPV upper skirt junction 135°).

http://www.tepco.co.jp/tepconews/library/movie-01j.html 19 April press conference 14:50 (Junichi Matsumoto on the robot mission into unit 2's torus room) : we recorded sounds with an IC recorder, but the "beep beep" sounds of the radiation dosimeter is mixed to it, so we could not make a good sound recording. We were thinking that water flowing sounds could be checked that way, but in retrospect the situation is that it could not be done well enough. Concerning this PCV suppression chamber torus room inspection with "Survey Runner" [the robot's name], one thing is that we confirmed that it is possible to use Survey Runner for this kind of mission, and the other thing is that at this point, although some heat insulating material covers were found to have fallen down, no major pipe or equipment deformation or damage was found in the upper part of the torus room. [...] (20:26, replying to a question by NHK's Hanada) I think it is possible that the heat insulating material's covers fell down because of the earthquake. As one year has elapsed since the earthquake and the humidity was high, corrosion can also be a possible cause. The exact cause is not known, but the heat insulating material, the wool-like material itself was not blown away, so that we think the cause is not liquids or gasses flowing out of the pipe. [...] (29:01) If no damage is found in the upper part of the torus room, we'll have to find a way to inspect underwater. [...] (29:30) Hanada : What methods can be thought to inspect the inner side of the torus room and the lower part that is not submerged by water ? Matsumoto : first we have to create a route astride the suppression chamber to get to the inner side catwalk. If we manage to take Survey Runner there, we can have it make a round trip on the inner side catwalk and inspect the vent pipes. For the area between the water surface and the catwalk, the grating is an obstacle, but I think it is possible to move the camera so that it focusses downwards. At this point we have not yet decided how or when we will do that. [about sound recording] I think perhaps we can try to record sounds again after turning off [all other] sounds. [about unit 3's equipment hatch] (...) (33:30) Yomiuri's Funakoshi: What did you want to see with this survey ? Matsumoto: One thing is that if water is oozing like that, it could be a valid water level. One other thing is that when we inspected the North-eastern area with Packbot, water was accumulated near the rail, and the radiation there was comparatively high, so we thought it was quite probable that water is leaking from the PCV (...) At this point, we don't know if it is a leak. The situation is that although it is wet like this, it was not confirmed that water is flowing. Funakoshi: Which quantity of water is accumulated on the floor ? Matsumoto: the floor is somewhat wet. At present we don't know the width and length of the wet area. Funakoshi: You don't know which percentage of the area is wet, and which percentage is dry ? Matsumoto: No we don't. We only inspected a small part with the endoscope. As the radiation is high the duration of the work was 4 minutes. Funakoshi: what is the most natural leak route that can be thought ? Matsumoto: the hatch is closed with bolts, like a manhole, and the most likely route is between bolt and packing.

http://www.tepco.co.jp/en/press/corp-com/release/2012/1202043_1870.html Report submitted to NISA concerning response to safety regulation breach during first FY2011 safety investigation at Fukushima Daiichi Nuclear Power Station

 

[jim hardy]

No, I think that opening is on the opposite side to the equipment hatch we are talking about today. Look at where the personnel airlock is on that photo (equator).

Are there two hatches?
Looking a MadderD's drawing in post 12898, the one at 2 o'clock is clearly a hatch with plug extended.
Opposite, 8 o'clock, is that another one with plug inserted?
It'd make sense to have one near each recirc pump for motor replacement.

Not a BWR guy,

old jim

 

[SteveElbows]

Are there two hatches?
Looking a MadderD's drawing in post 12898, the one at 2 o'clock is clearly a hatch with plug extended.
Opposite, 8 o'clock, is that another one with plug inserted?
It'd make sense to have one near each recirc pump for motor replacement.

Not a BWR guy,

old jim

Well the other large opening, that you describe as 8 oclick, looks a bit different on the plans we've seen. If I take the diagram literally then I get the idea that this hatch is not routinely used, does not have rails, may have been 'bricked in'. Perhaps it is was only used during reactor construction, or could be unblocked if something went wrong with opening the other one that is normally used. Been a while since I saw photos of this area, seem to think I may have seen a picture that confirms it is blocked off, but maybe I dreamt it.

There is also the personnel airlock one, which is obviously smaller, and in a part of the building that I don't think we have seen much of.

Big shame nobody at the press conference seemed to ask about whether the plug was further forwards than it should be when closed according to what Tsutsuji translated (thanks again!). Understandable that they talk about the unseen bolted hatch by the steel part of containment and possible kind of leak, but I really wanted to know whether todays discussion about the plug being forwards is true and important or not. Now I have no idea if/when we will ever find this out!

 

[MadderDoc]

Well the other large opening, that you describe as 8 oclick, looks a bit different on the plans we've seen. If I take the diagram literally then I get the idea that this hatch is not routinely used, does not have rails, may have been 'bricked in'. Perhaps it is was only used during reactor construction, or could be unblocked if something went wrong with opening the other one that is normally used. Been a while since I saw photos of this area, seem to think I may have seen a picture that confirms it is blocked off, but maybe I dreamt it.

There is also the personnel airlock one, which is obviously smaller, and in a part of the building that I don't think we have seen much of.

The area at the other large opening has been the scene of some cleaning and monitoring effort, so there is reasonable photo coverage of it. It appears as you say, to be blocked with a semipermanent plug. The plug appears to be in position, same as shown in the diagram of unit 2. That is: its outer face is at some distance from the wall, on the right hand side it has that 45 angles frame reinforcement you've pointed to, in order to meet the wall. On its left hand side it comes together with the shield walls around the personal airlock.

Best views I've found are at around 12:09 in this video:
http://photo.tepco.co.jp/en/date/2011/201106-e/110615-01e.html

Areas close to where the plug meets the wall to the right of this opening appear to be strong gamma sources:

http://photo.tepco.co.jp/en/date/2011/201106-e/110611-02e.html

and there has been quite some cleaning efforts at the site:
http://photo.tepco.co.jp/en/date/2011/201107-e/110702-01e.html

Big shame nobody at the press conference seemed to ask about whether the plug was further forwards than it should be when closed according to what Tsutsuji translated (thanks again!). Understandable that they talk about the unseen bolted hatch by the steel part of containment and possible kind of leak, but I really wanted to know whether todays discussion about the plug being forwards is true and important or not. Now I have no idea if/when we will ever find this out!

Assuming the plug was not moved by the earthquake or later events, the only possibility I can see how the plug can be in the semi-open position shown to us by the Tepco diagrams and videos would be if it had been intentionally, temporarily unplugged and I think if that were the case Tepco would have left no doubt about it. From that I deduce that the plug must have been moved by the earthquake or later events.

 

[jim hardy]

From that I deduce that the plug must have been moved by the earthquake or later events.

One can be sure the plug is restrained for seismic acceleration. When M is that large a small A generates lots of F; that ~1/2 g quake would have made the plug push against its restraints with half its considerable weight.

Presumably there's a bolted steel door on inside that could flex on overpressure and push against the plug like a piston. The available force from pressure is far greater than from earthquake but one has to consider most of it should have been opposed by door's rigidity. We need a GE guy who knows the design of that piece.

As always not quite enough data. But it is interesting to keep these observations in the back of our mind and be on lookout for relevant details.

You guys are doing an excellent job at that.

 

[MadderDoc]

If this big plug was moved, how ? Earthquake or explosion ?

I can't exclude that the earthquake moved it, I suppose it could plausibly have moved anything anywhere, however this plug appears so distinctly to have been pushed out, so I'd put my money on an explosion (some pressure wave from it).

(...) (33:30) Yomiuri's Funakoshi: What did you want to see with this survey ? Matsumoto: One thing is that if water is oozing like that, it could be a valid water level. One other thing is that when we inspected the North-eastern area with Packbot, water was accumulated near the rail, and the radiation there was comparatively high, so we thought it was quite probable that water is leaking from the PCV (...) At this point, we don't know if it is a leak. The situation is that although it is wet like this, it was not confirmed that water is flowing. Funakoshi: Which quantity of water is accumulated on the floor ? Matsumoto: the floor is somewhat wet. At present we don't know the width and length of the wet area. Funakoshi: You don't know which percentage of the area is wet, and which percentage is dry ? Matsumoto: No we don't. We only inspected a small part with the endoscope. As the radiation is high the duration of the work was 4 minutes. Funakoshi: what is the most natural leak route that can be thought ? Matsumoto: the hatch is closed with bolts, like a manhole, and the most likely route is between bolt and packing.

Thanks a lot, tsusuji, for these extra insights non-Japanese speaking users get from you.

From one of Tepco's publications, I've attached a cropped diagram, and a photo of a PCV hatch, as seen from inside the PCV. From what I've read elsewhere, the flange of a Japanese BWR would be sealed with silicone rubber seals, which should be good for at least 225 degrees C, but PCV temperatures upwards of 400 C were reported during the weeks after the explosion.

 

[SpunkyMonkey]

I can't exclude that the earthquake moved it, I suppose it could plausibly have moved anything anywhere, however this plug appears so distinctly to have been pushed out, so I'd put my money on an explosion (some pressure wave from it).

The fact that the first floor into which any impulse from the crevice would have entered was covered with dust and rubble and looked like it was hit by a hurricane further supports that the plug was pushed open by the explosion. Or maybe just that an impulse passed through the crevice whenever the plug was moved.

However, could the interior hatch still be in place and any impulse that pushed out the plug have been carried by air between the PCV steel liner and the concrete surrounding it? The reason I wonder this is that despite the disarray in the first floor, I'm not impressed that it took the full explosive force one might expect had there been a direct passage from a PCV explosion into the first floor. Or maybe the hatch was largely left in place but just enough of an impulse passed through its seams to push out the plug.

Btw, which Tepco publication has those images?