Fukushima: Unit 2 Discharge - Why Differs from Units 1 & 3?

[SteveElbows]

Good list/

I don't know of other blowout panels in the Reactor Building proper. There is a series of hatches from the first floor to the refueling floor for movement of spent fuel casks and other heavy loads. These hatches are not designed to be air tight. Many US plants have open web cargo nets on these hatches as fall protection. Neither are there airtight doors on stairwells. Finally the elevator shaft is not airtight. The SBGT system (emergencies) and reactor building ventilation system (normal operation) are designed to keep the reator building at a negative pressure compared to the atmosphere. This ensures the leakage in the building and the exhaust is through monitored paths to detect possible radioactivity releases.

Thanks very much for the detail. Certainly I agree that we know of many non-airtight pathways from one part of the building to another, after all we have seen robots climbing the stairs without meeting doors that are hard to open. My talk of other blowout panels was based on a long reportI read recently, though I can't lay my hands on it right now as I've looked at too many different docs recently. I will post about this again when I find it.

How about between the reactor & turbine buildings? Overall when looking at all the post-disaster talk on the internet, I sometimes feel that the turbine buildings have not received enough attention, although that's not surprising considering that only a few times have we gotten any info, surveys etc from the turbine buildings. We saw blowout panels open on at least a few of the turbine buildings west-facing walls in the footage from days/weeks after the disaster struck, not sure that we ever heard whether these were opened by humans, by explosions, or by pressure.

 

[NUCENG]

Thanks very much for the detail. Certainly I agree that we know of many non-airtight pathways from one part of the building to another, after all we have seen robots climbing the stairs without meeting doors that are hard to open. My talk of other blowout panels was based on a long reportI read recently, though I can't lay my hands on it right now as I've looked at too many different docs recently. I will post about this again when I find it.

How about between the reactor & turbine buildings? Overall when looking at all the post-disaster talk on the internet, I sometimes feel that the turbine buildings have not received enough attention, although that's not surprising considering that only a few times have we gotten any info, surveys etc from the turbine buildings. We saw blowout panels open on at least a few of the turbine buildings west-facing walls in the footage from days/weeks after the disaster struck, not sure that we ever heard whether these were opened by humans, by explosions, or by pressure.

The turbine building has a separate ventilation system, that also uses a monitored exhaust path. However, according to discussions about Fukushima, there may have been cable paths and or drains that permitted leakage to move from the Reactor Buidling to thr Turbine Building. There is also a steam tunnel for the feedwater and main steam piping. Finally there are airlocks between the buildings to allow access, even though there may be pressure differences between buildings.

 

[r-j]

Forgive me, but how does anyone know how much radioactivity came from each building?

 

[clancy688]

Excellent question. I was asking myself the same thing. But apparently, TEPCO knows. Or they think they know. There's a detailed listing of how much radiation every building spew:

http://www.kantei.go.jp/foreign/kan/topics/201106/pdf/attach_04_2.pdf

Check out page seven.

(Though it's probably outdated by now... recent publications give much higher numbers for the total released quantity of Cs)

 

[tsutsuji]

Jun16-11, 05:37 PM:

Hm, okay. Let's see, "TEPCO reports that Unit 2 is probably responsible for nearly all of the contamination."

I think that's better than my previous claim. Of course I'd be interested in how TEPCO decided that Unit 2 released that much radioactivity.

Did they actually measure what was coming out of Units 1, 2 and 3? (I can't really imagine how that would be possible without dozens of sensors in and on the reactor buildings). Did they make that statement based on the course of events? (Big radioactivity spike after the explosion sound in Unit 2 -> Unit 2 is entirely at fault)
Or do they perhaps know more than us? But you're probably right. Before we can discuss why Unit 2 popped out so much radioactivity, we need to evaluate first if and/or why the report about that is justified.

Please note that in its report of 12 March 2012 http://www.irsn.fr/FR/expertise/rap.../IRSN_Rapport_Fukushima-1-an-apres_032012.pdf page 46/189, the French IRSN expresses the view that unit 3 released more radiations than unit 2:

(in PBq)

                  Xe-133     I-131    Cs-137
unit 1           1530           13          1
unit 2           2180           57          6
unit 3           2240          126        14

They comment, page 47/189 : the distribution among the reactors estimated by IRSN is uncertain (...) most [other] experts agree with each other on the view that reactor No. 2 produced a majority of releases, because of the PCV damage that occurred during the hydrogen explosion. Moreover, after the main release period (up to 17 March) attributing the releases to each reactor is very uncertain.

Surprisingly, on page 29/189, they ignore Tepco's view that there was no hydrogen explosion at unit 2 (and that the sound heard and the seismic measurement recorded around 6 AM on 15 March was produced by an explosion at unit 4).

Surprisingly, on page 36/189 Figure 5-16 they attribute the MP8 radiation peak in the night of 12 March to "unit 2 PCV venting" ? Wasn't unit 2's venting started on 14 March ?

 

[SteveElbows]

Well sadly that report does not go into much detail about how they did calculations etc.

Certainly we should still be careful when comparing the reactors, because nobody really knows and there are a number of factors which can have a very large impact on estimates:

The assumption that reactor 2 suppression chamber sustained damage can make a big difference to release estimates, and although TEPCO said explosion wasn't there, damage cannot be ruled out yet. Probably safe to assume that most release estimates still involve assumption of s/c damage at reactor 2.

Possible very brief factor 2 drywell vent that we don't know whether actually happened or not (at 0:02 on 15th).

The wind was blowing out to sea during key big events for reactor 3, so it would be easier to underestimate this reactors releases.

Later events at reactor 3 might be hard to distinguish from events at reactor 2, and we hear little of events that happened after the 16th.So with this in mind, it is probably safer to say the following, as opposed to saying that reactor 2 released more in total. Reactor 2 was responsible for the majority of the contamination on land, because of timing of wind and rain. And because of the highly contaminated water int he basement and the leaking of some of this to the ocean, we can blame reactor 2 for a lot of the ocean contamination too. But reactor 3 could have released a lot into the air over the sea, and may have contributed to some of the march 15th-16th and 20th land contamination that's mostly blamed on reactor 2.

While the French report is lacking in some areas, I think it is very very good for looking at the detail of what the weather was doing at key moments, and the land contamination data.

As to why it labels an event of a graph as being caused by reactor 2 venting at approx 9pm on the 12th, this looks like a simple mistake to me but I shall go and check other sources to remind myself what event actually happened at that time.

 

[MadderDoc]

<..>
What I find especially annoying is that we don't even know exactly when steam was first noticed to be coming from the blowout panel hole in the side of reactor 2. We certainly know that plenty of steam etc came out of this hole later, as we have footage, but not knowing when it began is frustrating. Assuming it was from the reactor rather than the fuel pool, which is a reasonable bet given much later footage showing steam from the reactor arena and the robot-measured radiation readings showing high levels by one side of the floor above the reactor well, we may well imagine that this started on March 15th. But it would be good to know for sure, especially as events at reactor 4 building on the 15th also got in the way of really clear explanations of radiation data on that day.

http://www.tepco.co.jp/en/news/110311/images/110412_1f_tsunami_6.jpg (This is the earliest dated photo I know of showing steam coming from Unit 2.)

 

[SteveElbows]

http://www.tepco.co.jp/en/news/110311/images/110412_1f_tsunami_6.jpg (This is the earliest dated photo I know of showing steam coming from Unit 2.)

Wow! I had missed that one when it was originally released as Tepco published it last April in reference to tsunami water levels, I had not considered the possibility that the photo was taken on a crucial day of the unfolding disaster.

If the timestamp is accurate then this photo was taken during the period when the reactor 2 drywell pressure was falling substantially, and a time when large number of people had been evacuated from the site. Hardly the time that you would choose to send people to take photos relating to the tsunami, but certainly a time where you may want photo of what's happening at reactor 2.

I didn't find other photos taken with the same camera, so its hard to find evidence that the time & date were correct. I note that the photos taken from the ground that show reactor 4 damage were taken with a different camera approximately one hour earlier (if this other cameras timestamp is accurate).

 

[MadderDoc]

Wow! I had missed that one when it was originally released as Tepco published it last April in reference to tsunami water levels, I had not considered the possibility that the photo was taken on a crucial day of the unfolding disaster.

If the timestamp is accurate then this photo was taken during the period when the reactor 2 drywell pressure was falling substantially, and a time when large number of people had been evacuated from the site. Hardly the time that you would choose to send people to take photos relating to the tsunami, but certainly a time where you may want photo of what's happening at reactor 2.

I didn't find other photos taken with the same camera, so its hard to find evidence that the time & date were correct. I note that the photos taken from the ground that show reactor 4 damage were taken with a different camera approximately one hour earlier (if this other cameras timestamp is accurate).

A _third_ camera was according to exif data involved in the taking of the photo at
http://www.tepco.co.jp/en/news/110311/images/110412_1f_tsunami_5.jpg.

According to its exif data this photo was taken about 10 minutes before the photo showing steam from unit 2, and the camera was pointed west, from 100 m down the road between units 2 and 3, i.e. pointed towards the position from which the steam photo according to its exif data was taken a few minutes later.

Judging from details shown in this photo (e.g the presence of particular pieces of debris, that were later removed, and the absence of hoses laid out later,) this photo must have been taken quite soon after the explosion in unit 3, so I am rather confident that the exif date of this photo is correct.

And albeit indirectly, this would support that the Unit 2 steam photo was in fact taken on the morning of March 15, along with other photos, apparently by a 2+ camera/man expedition.

 

[Gary7]

From today's Tokyo Shinbun

Large Release From Unit 2 - "From the upper part of the containment vessel"
Tepco Announcement on Fukushima Accident

On March 19th Tepco announced that the sudden increase in radiation readings measured around the power plant on March 15th last year was possibly caused by leaks coming from between the containment vessel and its lid, as well as from pipe connections. Previously it was thought that the most likely source of the radiation was damage to the suppression chamber.


The article goes on to say that the suppression chamber was initially suspected because of the large explosion heard just as pressure readings from the suppression chamber dropped, but that it was later determined that the explosion was from #4 (this based on seismic readings from around the plant on the morning of the 15th of March, 2011).

 

[tsutsuji]

From today's Tokyo Shinbun

Link : http://www.tokyo-np.co.jp/article/national/news/CK2012032002000020.html

The announcement was made at the Japan Atomic Energy Society meeting in Fukui.

The explosive sound was heard at 06:10 on 15 March 2011.

Almost at the same time, unit 2's suppression chamber pressure reading declined to 0 Pa, which is below atmospheric pressure.

The radiation rose to 15 mSv/hour at the main gate at 9 AM on 15 March 2011.

Tepco's nuclear safety group manager Koichi Miyada said that unit 2's PCV pressure declined from 730 kPa at 7 AM on 15 March 2011 to 150 kPa at 11 AM, and "it is inferred that at this stage, large quantities of radioactive substances were released". "(as the S/C pressure reading below atmospheric pressure is hard to believe) there is a high probability that the measuring instrument is broken".

 

[SteveElbows]

Thanks for the detail on this story, good timing! I assume this possibility is discussed now because they did not see massive damage when they looked inside the torus room.

Here is my attempt at an explanation for large reactor 2 environmental release even if the suppression chamber did not sustain much damage:

Its because there was no opportunity to wet-vent some of nastiest substances that were generated during the core melt. At reactors 1 & 3 they were able to wet vent after the really bad problems started, trapping a lot of these substances in the suppression chamber water. But at reactor 2 there was no such vent, so far more of these substances were mostly still in the drywell. Then the drywell failed whilst it was under high pressure, allowing these substances to be released to the environment in quite a vigorous manner.

There are other possible factors too, but I think the above is basically all we need to explain reactor 2 release being greater than the other reactors.

Other factors could include things such as the timing of the drywell failure in relation to any possible core-concrete reaction. A lot of stuff is generated by the core-concrete reaction, and at reactors 1 & 3 we could assume that wet-venting was performed after such a core-concrete reaction happened, providing some scrubbing. This didn't happen at reactor 2, where direct drywell->environment release occurred without any significant prior wet vent.

As mentioned in previous posts we should also consider that wind direction & rain/snow gave reactor 2 emission far greater chance of being detected.

Anyway I notice that on TEPCO press releases from the 19th March 2012 they mention changes to the nitrogen injection to reactor 2 in preparation for the 2nd endoscope mission, so I don't think we have to wait long to discover more about water level etc, unless this mission fails even worse than the first try.

 

[MadderDoc]

So, would the chunks of debris slumped across the reactor well (along the red fence) represent fragments of the concrete plug(s) produced by some violent impulse from below?

 

[clancy688]

What's the radiation up there? There are a lot of white dots on the picture...

 

[zapperzero]

What's the radiation up there? There are a lot of white dots on the picture...

In the tens of mSv/h iirc. The survey results were posted along with the pictures.

 

[SteveElbows]

So, would the chunks of debris slumped across the reactor well (along the red fence) represent fragments of the concrete plug(s) produced by some violent impulse from below?

I wouldn't say that, the debris doesn't really look like that to me.

To be honest I don't think we should necessarily be looking for signs of violent concrete plug action, I think it is quite possible for sizeable quantities of stuff to leak out in a far less spectacular way, e.g. via degraded gaskets, seals etc. Likewise even if the containment cap moves, it doesn't mean the concrete plugs have to.

 

[SteveElbows]

In the tens of mSv/h iirc. The survey results were posted along with the pictures.

Yeah, but in the range of hundreds of mSv/h either side of the reactor well top concrete containment caps.

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120228_04-e.pdf

 

[SteveElbows]

A _third_ camera was according to exif data involved in the taking of the photo at
http://www.tepco.co.jp/en/news/110311/images/110412_1f_tsunami_5.jpg.

According to its exif data this photo was taken about 10 minutes before the photo showing steam from unit 2, and the camera was pointed west, from 100 m down the road between units 2 and 3, i.e. pointed towards the position from which the steam photo according to its exif data was taken a few minutes later.

My EXIF viewing tool says that one was from a day later, the 16th.

 

[MadderDoc]

I wouldn't say that, the debris doesn't really look like that to me.

To be honest I don't think we should necessarily be looking for signs of violent concrete plug action, I think it is quite possible for sizeable quantities of stuff to leak out in a far less spectacular way, e.g. via degraded gaskets, seals etc. Likewise even if the containment cap moves, it doesn't mean the concrete plugs have to.

True enough, but the debris is still there crying for an explanation.

 

[MadderDoc]

My EXIF viewing tool says that one was from a day later, the 16th.

You are right, thanks for the correction.

 

[zapperzero]

True enough, but the debris is still there crying for an explanation.

It looks like plastic sheeting. Maybe that's just what it is. It would have been used, I believe, for most any kind of maintenance activity in that area. The boots tell the same story - work in progress, abandoned because of the quake, or simply because it was the weekend.

 

[SteveElbows]

It looks like plastic sheeting. Maybe that's just what it is. It would have been used, I believe, for most any kind of maintenance activity in that area. The boots tell the same story - work in progress, abandoned because of the quake, or simply because it was the weekend.

Yeah, and we don't actually know the exact time that humans were on the refuelling floor for the very last time before that reactor went seriously wrong. In theory they may have been there on occasions after the earthquake, official narratives are not detailed about stuff that is not considered central to the decline of each reactor or measures taken to try to control the situation. For all we know they may have been dealing with the consequences of sloshing of the spent fuel pool for some time, although I know of no reports that point strongly in that direction, just giving an example of events that would be overshadowed by later dramatic events.

 

[MadderDoc]

It looks like plastic sheeting. Maybe that's just what it is. It would have been used, I believe, for most any kind of maintenance activity in that area. The boots tell the same story - work in progress, abandoned because of the quake, or simply because it was the weekend.

Fair enough, zapperzero. We do know from the operation log that maintenance work of the overhead crane was ongoing; from the Quince photos it can clearly be seen that the crane has been parked over the reactor cap, and a ladder has been improvised at its east end to gain access to the operator booth of the crane, from which there is access to the rest of the crane. Also some ropes can be seen hanging from the ceiling to the floor at each end of the beams of the crane, plausibly for hoisting stuff up and down.

And there is the very technical, albeit temporary looking machinery that has been planted on the middle of the reactor cap.

During its tour Quince stares into a sort of controlled route to the work area under the crane, and this route leads straight to the area with the funny boots, at the edge of the reactor cap.

Right at the entry to this route can be seen big plastic bags, plausibly for unloading personal plastic coveralls etcetera before exiting the work area.

So, the irregular debris strewn along the red fence could well be wrapped up waste material produced during the maintenance work, left there by the maintenance workers for later waste disposal.

 

[MadderDoc]

Not too much can be gleaned from the scaled version of this image, looking towards an entry to the torus room in unit 2, which we have been discussing:

One could well get the impression that the place just needs a good clean up, and a lick of paint.

However, there may be more to it. Looking at the original photo, at:
http://photo.tepco.co.jp/library/120314/120314_05.JPG

Is that door still on its hinges?

 

[SteveElbows]

Nothing in that photo really suggests its not on its hinges, or have I missed something?

The vent on the wall above the door was of slightly more interest to me.

 

[MadderDoc]

Nothing in that photo really suggests its not on its hinges, or have I missed something?

The vent on the wall above the door was of slightly more interest to me.

I'd expect the signs on the door to be on the outside, but if the door is on its hinges, this door would be left-hinged, opening out from the torus room, and the signs we can see on this door would be meant to be seen only from inside of the torus room. The corresponding door in unit 3 is right-hinged. and would open inward towards the torus room. Perhaps this could explain why the door in unit 3 came to bulge out jammed shut, while the door in unit 2 was merely slammed open.

The tilting of the vent (if that's what interests you?) could be a design feature, such as to not blow air into the corner, but rather into the room. A similar tilt can be seen with the corresponding vent in unit 3 in the high res photo at:
http://photo.tepco.co.jp/library/120314/120314_10.JPG

 

[jim hardy]

Well the fellow is wearing respirator, full plastic pc's and using a survey meter with long handle to see what's the field on far side of doorway before he goes through it.

Did they go beyond the door, anyone know?

Most of you know this, but for possible benefit of others -
He's dressed for an area that's highly contaminated with transferables ( stuff that'll rub off on your clothes), not just radiation from stuff inside pipes..

 

[SteveElbows]

I'd expect the signs on the door to be on the outside, but if the door is on its hinges, this door would be left-hinged, opening out from the torus room, and the signs we can see on this door would be meant to be seen only from inside of the torus room. The corresponding door in unit 3 is right-hinged. and would open inward towards the torus room. Perhaps this could explain why the door in unit 3 came to bulge out jammed shut, while the door in unit 2 was merely slammed open.

The tilting of the vent (if that's what interests you?) could be a design feature, such as to not blow air into the corner, but rather into the room. A similar tilt can be seen with the corresponding vent in unit 3 in the high res photo at:
http://photo.tepco.co.jp/library/120314/120314_10.JPG

Thanks for the info about the vent, makes sense.

As for the door, it does not surprise me to see signs on the inside of the door. The building seems pretty heavily labelled everywhere. And there are signs in other photos that the triangular rooms at this level are labelled MB, and the very edge of a letter B may just be visible on the sign on that door.

 

[SteveElbows]

Did they go beyond the door, anyone know?

Yeah according to TEPCOs report they went through that door and took 2 more photos, one of the stairs ( http://photo.tepco.co.jp/library/120314/120314_06.JPG )and then one of the suppression chamber ( http://photo.tepco.co.jp/library/120314/120314_07.JPG ).

This report shows how the photos relate to the locations:

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120314_01-e.pdf

 

[jim hardy]

Thanks Steve.
( http://photo.tepco.co.jp/library/120314/120314_07.JPG ).

Is that insulation or the actual pressure vessel?

Any observations on the red stain ? It looks to surround an irregular shape resembling a crack.
Insulation cracked wouldn't be a surprise.

 

[MadderDoc]

Yeah according to TEPCOs report they went through that door and took 2 more photos, one of the stairs ( http://photo.tepco.co.jp/library/120314/120314_06.JPG )and then one of the suppression chamber ( http://photo.tepco.co.jp/library/120314/120314_07.JPG ).

This report shows how the photos relate to the locations:

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120314_01-e.pdf

Thank you. Referring to the new images you link to, taken from through a doorway to the torus room (according to the handout that would be a door from the NE side of the torus):
120314_06.JPG has EXIF time 12:11:58, and
120314_07.JPG has EXIF time 12:12:11.

Then this photo, at:
http://photo.tepco.co.jp/library/120315/120315_01.jpg
would seem have been taken from through the very same doorway of the torus room: it has EXIF time 12:12:18.
But, this photo has been published as coming from the NW side of the torus room? So from which side of the torus have these photos actually been taken?

Also I am not quite sure what is up in this third photo.

 

[MadderDoc]

Thanks Steve.
( http://photo.tepco.co.jp/library/120314/120314_07.JPG ).

Is that insulation or the actual pressure vessel?

Any observations on the red stain ? It looks to surround an irregular shape resembling a crack.
Insulation cracked wouldn't be a surprise.

I certainly see it as the actual painted metal surface of the torus, or suppression chamber. Is a torus insulated? Never thought they would be, but I am just an amateur in those matters.

The red stain looks to me as if it is coming from dripping from further above, or perhaps from a leak higher up on the torus. It does not seem to me to originate from the irregular shape resembling a crack. That shape could be more innocently, a rusty weld.

 

[tsutsuji]

Thanks Steve.
( http://photo.tepco.co.jp/library/120314/120314_07.JPG ).

Is that insulation or the actual pressure vessel?

Any observations on the red stain ? It looks to surround an irregular shape resembling a crack.
Insulation cracked wouldn't be a surprise.

This picture is captioned as followed by http://www.yomiuri.co.jp/science/news/20120314-OYT1T01074.htm

Whitish dust has deposited on red brownish paint, but some part was soaked by water. This is how the suppression chamber is looking, a part of the PCV, a 34 m diameter donut. On the right hand side, a different silver-colored pipe can be seen (Picture taken by Tepco)

The caption of the other picture ( http://photo.tepco.co.jp/library/120314/120314_04.JPG ) is the following:

Unit 2's suppression chamber photographed for the first time since the accident. On the right hand and far side, the suppression chamber can be seen. On the left and closer side a different silver-colored pipe can be seen. (Picture taken by Tepco)

[Do you think the whitish "dust" can be salt ?]

 

[SteveElbows]

Yes I was just going to say that as far as I know the torus is red, something stained this part of the torus white, and then something else washed off part of the white stain.

The photo from the other door shows the torus looking quite red, but the lighting isn't good so I wouldn't like to stretch this comparison too far.

I not know about the possible wrong location of that other photo, I haven't thought about it much but mis-labelling is always possible. I suspect that down is to the right of the photo, and that the 'floor' that can be seen in this direction is actually the water which has reached that level of the torus room (the same water we see in the stairwells). This water can hardly be seen but if you follow the wall downwards then it becomes visible to the eye.

Anyway they were in quite a rush when taking those photos due to the radiation, and the video from the reactor 2 mission suffered from lack of focus/plastic bag issues, so I don't think I will be able to piece much more together from the available footage, but I will watch the dreadful video again just in case.

 

[SteveElbows]

[Do you think the whitish "dust" can be salt ?]

Thanks again for the very helpful translations.

Salt seems like a possibility for sure, though I am not good at chemistry so I cannot comment on what other substances it could be.