Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[clancy688]

Ten months after the meltdown?

 

[zapperzero]

And what is with unit 2 temperature: http://www.tepco.co.jp/nu/fukushima-np/f1/images/12011612_temp_data_2u-j.pdf ?

That particular sensor holds the record for highest indicated temp, iirc. But other than a huge spike in the beginning, it has been tracking the others quite well until very recently, so SOMETHING must have changed.
Other temps seem to be creeping up as well. May be more than instrument error.

 

[Rive]

... SOMETHING must have changed.

And some other sensors related to the RPV bottom are also fluctuating.
It's interesting that some of them has measurement points below the last averages. So IMO the presence of a such intense heat source as corium is unlikely.

Maybe the cooling water found some way through the crust and now escaping as steam?

 

[zapperzero]

Maybe the cooling water found some way through the crust and now escaping as steam?

There would have to be water beneath the corium and I don't see how that could happen.

 

[tsutsuji]

http://www3.nhk.or.jp/news/html/20120117/t10015315481000.html The Diet's investigation commission held its first public hearing today. It was learned that the ministry of education and science sent the SPEEDI data to the American army immediately after the accident (while the Japanese public had to wait for months).

http://www.ustream.tv/user/jikocho/videos Ustream channel of the Diet's investigation commission, with the videos of the hearings.

http://www.naiic.jp/ website of the Diet's investigation commission.

http://www.naiic.jp/schedule/ Schedule of the 16 January hearing : "Exchange of views about each report on the accident" with
* Yōtarō Hatamura (president of the cabinet investigation committee, about their interim report)
* Masao Yamasaki (Tepco vice president, about Tepco's internal investigation interim report)
* Itaru Watanabe (Deputy director, science and technology policy bureau, about their 23 December "first report" : http://www.mext.go.jp/a_menu/saigaijohou/syousai/1314588.htm )

Just a glimpse : at 00:34:08 on http://www.ustream.tv/recorded/19800211 a commission member tells Tepco's vice president he disagrees with the "no scientific basis" wording used by Tepco about some tsunami studies predicting high tsunamis.

 

[duccio]

Looks like they want to send an endoscopic probe into reactor 2...

http://www.asahi.com/national/update/1226/TKY201112260664.html

I'm not sure about the reliability of the source, and it's only in Japanese, but easy to understand with Google Translator

 

[zapperzero]

Looks like they want to send an endoscopic probe into reactor 2...

Kindly stop posting last year's news, please. Thread is chaotic enough as it is. Thank you.

 

[LabratSR]

Looks like they want to send an endoscopic probe into reactor 2...

http://www.asahi.com/national/update/1226/TKY201112260664.html

I'm not sure about the reliability of the source, and it's only in Japanese, but easy to understand with Google Translator

They announced their intention to do this a month or so ago. Should be interesting when they do.

 

[LabratSR]

For what its worth, they have been tinkering with the water injection to Unit 2.

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120113_03-e.pdf

"Unit 2・11:20 on January 13:As variation in the injected water amount into the reactor was confirmed, we adjusted water injection from the reactor feed water system from approx 2.5 m3/h to 3.0 m3/h, and water injection from the core spray system from approx. 7.2 m3/h to 7.0 m3/h."

 

[tsutsuji]

They announced their intention to do this a month or so ago. Should be interesting when they do.

http://www.shimbun.denki.or.jp/news/main/20120116_04.html On 16 January Tepco said it had started the work to inspect inside unit 2's PCV using an endoscope. First they must install the drilling machine, then drill the "end plate of the penetrations", then install the endoscope. If everything goes well, they can take pictures and measure temperatures on 19 January. The goal is to measure temperatures, water levels and water temperatures.

The details of what they plan to do are on http://www.tepco.co.jp/nu/fukushima-np/roadmap/images/m111226_08-j.pdf pages 5/37 to 12/37. Even if you don't read Japanese you may enjoy looking at the diagrams. Do you have any idea what this "penetration X-53" is for, in normal times ? On the diagram on page 8/37 they show the welding of a "short pipe", the drilling,　then the pushing of a concrete block with a stick until it falls down　[?], then the installation of the guide pipe flange, and at last the insertion of the endoscope with its guide tube. On page 10/37 they say they will use ultrasonic testing to be sure there is no water in the penetration before they start drilling. They also say that in order to reduce steam (which might prevent from taking good photographs) they will increase the water injection to lower the temperature. The yellow area on page 9/37 is the area they expect to photograph. The violet triangles are "examples of photographs" taken with the "mock-up" performed at unit 5. CRDレール　means "CRD rail".

 

[duccio]

sorry @zapperzero, what I really meant was that you can check many neat things with an endoscope, but no one was talking about it here and the press release hasn't even been translated to English. They talked for three months about sending a robot inside the building, with pictures and so on, and no single word about "putting your head deep inside the reactor". I couldn't find anything, that's why I was dubious and asked for more info.

@tsutsuji, thanks a lot. I'm also curious about the X-53, but google translate doesn't help, for X53ペネ拡大図 returns "Enlargement Pene X53"... wonder if it is the code for the pipe on page 7...

 

[Most Curious]

Anyone know what the building under construction is? Not really enough detail in the picture to learn much about it.


One of the diagrams of the endoscope penetration leads me to believe they are going to look below the pressure vessel lower head. Maybe to get an idea of the melt through and debris pile in that area? Is that correct?

 

[NUCENG]

http://www.shimbun.denki.or.jp/news/main/20120116_04.html On 16 January Tepco said it had started the work to inspect inside unit 2's PCV using an endoscope. First they must install the drilling machine, then drill the "end plate of the penetrations", then install the endoscope. If everything goes well, they can take pictures and measure temperatures on 19 January. The goal is to measure temperatures, water levels and water temperatures.

The details of what they plan to do are on http://www.tepco.co.jp/nu/fukushima-np/roadmap/images/m111226_08-j.pdf pages 5/37 to 12/37. Even if you don't read Japanese you may enjoy looking at the diagrams. Do you have any idea what this "penetration X-53" is for, in normal times ? On the diagram on page 8/37 they show the welding of a "short pipe", the drilling,　then the pushing of a concrete block with a stick until it falls down　[?], then the installation of the guide pipe flange, and at last the insertion of the endoscope with its guide tube. On page 10/37 they say they will use ultrasonic testing to be sure there is no water in the penetration before they start drilling. They also say that in order to reduce steam (which might prevent from taking good photographs) they will increase the water injection to lower the temperature. The yellow area on page 9/37 is the area they expect to photograph. The violet triangles are "examples of photographs" taken with the "mock-up" performed at unit 5. CRDレール　means "CRD rail".

No guarantee that it is the same at Fukushima, but in a US BWR-3/4, penetration X-53 was used for initial power testing. It is located below the centerline of the spherical portion of the drywell, but above the top of the vent pipes from the drywell to the torus. That is consistent with boring being performed on the first floor of the reactor building.

 

[triumph61]

That particular sensor holds the record for highest indicated temp, iirc. But other than a huge spike in the beginning, it has been tracking the others quite well until very recently, so SOMETHING must have changed.
Other temps seem to be creeping up as well. May be more than instrument error.

I don´t think so...

http://www.tepco.co.jp/en/nu/fukushima-np/f1/images/12011712_temp_data_2u-e.pdf

 

[jim hardy]

be aware that thermocouples, when wet and insulation damage let's moisture contact their metal, will give wildly erroneous readings

so be on lookout for water spillage in area of an erratic sensor like that. if misbehavior correlates with washdowns, well, give it some time to dry out.

 

[zapperzero]

be aware that thermocouples, when wet and insulation damage let's moisture contact their metal, will give wildly erroneous readings

so be on lookout for water spillage in area of an erratic sensor like that. if misbehavior correlates with washdowns, well, give it some time to dry out.

It certainly isn't working right, that's for sure. You're saying maybe it's been flooded.

What do we know about the water level in the RPV and PCV? Almost nothing, right?

 

[tsutsuji]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20120118/index.html On 17 January workers entered into the north-west part of unit 2's reactor building first floor and drilled in the spare penetration the hole through which the endoscope will be inserted. The work is made by ten teams of four people, which makes a workforce of 40. They were trained in drills performed at unit 5 in order to spend as little time as possible. The maximum exposure was 3 mSv. On 18 January they will do preparation work such as installing the endoscope and on 19 January they will start taking pictures with it.

http://www3.nhk.or.jp/news/genpatsu-fukushima/20120117/index.html At 04:10 PM on January 17, there was a trouble at the Minami Iwaki switching station, in Tamura city, and voltage declined momentarily in a wide surrounding area. As a consequence, the spent fuel pool cooling systems stopped for a little more than one hour at Fukushima Daiichi units 2, 3, and 6 and Fukushima Daini units 1 and 3. There was no major variation of temperature in those pools. The nitrogen injection systems of units 1, 2 and 3 stopped for 50 minutes. Fukushima Daiichi's water injection systems and monitoring posts continued working, and no radioactive substances were released. Tepco is investigating the cause of the switching station trouble and checking the status of the equipments that stopped. Commenting the fact that it took a little more than one hour to restore the systems, Tepco said "as we have a time margin until pool and reactor temperatures rise, the reactor water injection systems and the pool cooling systems are not designed to restart automatically".

 

[SteveElbows]

Thanks for all the info about the unit 2 endoscope work.

Here is a document that shows a little about the trial run they did at reactor 5. The image quality of photos they can take with this tech seems fairly poor, but its much better than nothing.

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120118_01-e.pdf

 

[Yamanote]

You can follow this link to a video of this trial run:

http://www.tepco.co.jp/en/news/library/movie-01e.html

Just select the tab "Video For Press" and choose the first video in the list.

 

[tsutsuji]

On December 16 the Nisa asked Tepco some questions about the accident progression, and Tepco answered on December 22 with a report hardly explained in the very short English press release here : http://www.tepco.co.jp/en/press/corp-com/release/11122216-e.html I guess the Nisa wanted to keep up with some of the problems raised by the government investigation committee, for example why unit 3's HPCI was stopped on March 13. There are also questions about unit 2. My problem is that I have not read that far into the government investigation report, so I am not trying to read that 22 December report for now. I just wanted to mention that this piece of information exists, which is the latest one provided by Tepco concerning the accident, and that the NISA's questions have now been translated into English :

part of the pressure behavior of the reactor pressure vessels and primary containment vessel drywells of Units 2 and 3 as well as part of the venting operation at Units 1, 2 and 3 at Fukushima Dai-ichi NPS, TEPCO have not been made clear. This is to inform the public that NISA directed TEPCO to report the points mentioned above to NISA by December 22, 2011 as described in the Appendix.
http://www.nisa.meti.go.jp/english/press/2012/01/en20120113-2-1.pdf

And the appendix with each question is here : http://www.nisa.meti.go.jp/english/press/2012/01/en20120113-2-2.pdf (English)

http://www3.nhk.or.jp/news/genpatsu-fukushima/20120119/index.html On 18 January the NISA held a meeting on the aging of Fukushima Daiichi. A report was presented with the conclusion that the aging of the plant over the past 40 years had no consequence on the accident. However, one specialist said there are not enough data to says so, another one said it is not possible to say so while the inside of the plants cannot be inspected. So finally the NISA decided to revise its conclusion, to study again and to hear specialists again on this topic. [It might be a slightly different topic, but I think I saw a Tepco report on the metal fatigue caused by the earthquake lately, but I don't remember where it was. Perhaps in the middle long term roadmap, or in the "concept of securing mid term safety" reports. Or was it in a separate press release ?]

You can follow this link to a video of this trial run:

http://www.tepco.co.jp/en/news/library/movie-01e.html

Just select the tab "Video For Press" and choose the first video in the list.

Thanks for the link. What is this "snow" on the video ? Dust ? Steam ?

 

[duccio]

Thanks for the link. What is this "snow" on the video ? Dust ? Steam ?

Yup, I'm also curious. And in reactor 2, the dots are caused by radiation on the sensor... or not?

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120119_03-e.pdf

 

[clancy688]

http://www3.nhk.or.jp/daily/english/20120119_28.html

The operator of the crippled Fukushima Daiichi nuclear power plant has failed in an attempt to get clear images from inside damaged reactors using fiber-optic lines.

Let me get this straight - they are boring into the primary containment of a melted down reactor, with the reactor vessel in question being perforated and leaking water and corium into the said containment - and they are surprised that steam and radiation are causing poor visibility?

 

[SteveElbows]

http://www3.nhk.or.jp/daily/english/20120119_28.html
Let me get this straight - they are boring into the primary containment of a melted down reactor, with the reactor vessel in question being perforated and leaking water and corium into the said containment - and they are surprised that steam and radiation are causing poor visibility?

I doubt they are really surprised by this at all, they knew conditions inside would not be ideal for imagery. I assume they hoped for more, but the mission isn't exactly a failure, NHK story is badly worded.

Of more concern is that they appear surprised that the water level inside containment was not visible and so does not seem to match their estimates. I don't know exactly what their estimates told them but I am not really surprised that they estimated this stuff wrong again, as they seem to like to assume things that give some reassurance, rather than err-ing on the side of caution.

 

[SteveElbows]

Here is a news item that mentions image quality & water level quotes from an official:

http://www.timeslive.co.za/scitech/2012/01/19/tepco-uses-camera-to-survey-fukushima-plant

 

[clancy688]

Recent news about emergency power for sensors being disconnected in November 2010:

http://www.bloomberg.com/news/2012-01-19/tepco-cut-backup-power-at-fukushima-before-crisis-sankei-says.html

Tokyo Electric Power Co. (9501) disconnected an emergency power source at its Fukushima nuclear plant four months before the earthquake and tsunami in March last year wrecked the station, the Sankei newspaper said.
The supply was cut during maintenance work in November 2010 and wasn’t reconnected, the paper reported, without citing the source of its information.
The backup would have provided power for transmitting temperature and radiation data from monitors near the Fukushima Dai-Ichi plant’s reactors and helped assess the severity of the situation once the main electricity supply was knocked out, the Sankei said.
Tokyo Electric is checking the Sankei report and can’t immediately comment, spokeswoman Ai Tanaka said.

A german news portal (spreadnews) refers to jiji and says that the sensor system in question was the "Emergency Response Support Systems", or ERSS.

Does anyone have a clue what exactly this ERSS is monitoring? Reactor data (pressure, temperatures) for example?Here's a report saying that the ERSS didn't work when the accident started: http://www.kantei.go.jp/foreign/kan/topics/201106/pdf/chapter_v.pdf

The Emergency Response Support System (ERSS), which monitors status of reactors and forecasts progress of the accident in a nuclear emergency, got errors in the data transmission function of the system right after the occurrence of the accident. Therefore, necessary information from the plant could not be obtained and the intended functions of the system V-2 could not be utilized.

And here's a NHK report:

https://www.nhk.or.jp/daily/english/20120119_20.html

 

[tsutsuji]

Yup, I'm also curious. And in reactor 2, the dots are caused by radiation on the sensor... or not?

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120119_03-e.pdf

http://www3.nhk.or.jp/news/genpatsu-fukushima/20120119/index.html On 19 January, Tepco checked inside unit 2's PCV using the endoscope. In addition to many white spots caused by radiations, the pictures are unclear because of water drops caused by the contaminated water's steam. It was not possible to check the upper surface of the water, which is lower than expected. No important damage or deformation was found on the PCV walls or on the pipes that were pictured. The PCV's internal temperature was 44.7°C (versus 42.6°C displayed by the thermometer that has been used until then : this is a small error range). Tepco commented that the vision field was limited by high gamma rays and water drops, and said they will study the possibility of using a different equipment in the future. Professor Ninohe of Tokyo university said that the temperature of around 40°C is confirming the fact that the melted fuel has also accordingly a low temperature and that it is a pity that the water surface could not be observed because it is an important clue for finding the location and the size of the PCV damages.

 

[Jim Lagerfeld]

I doubt they are really surprised by this at all, they knew conditions inside would not be ideal for imagery. I assume they hoped for more, but the mission isn't exactly a failure, NHK story is badly worded.

Of more concern is that they appear surprised that the water level inside containment was not visible and so does not seem to match their estimates. I don't know exactly what their estimates told them but I am not really surprised that they estimated this stuff wrong again, as they seem to like to assume things that give some reassurance, rather than err-ing on the side of caution.

According to the press conference I watched yesterday (and assuming I understood it all correctly) they had expected to see the water level at about 'OP 10000' (about 5m above the bottom of the primary containment floor). This prediction was based on 'pressure differentials'. Instead they found they could see the exposed grating walkway at 'op 9500' (about 4.5m / one floor above the containment bottom). So they infer that the water is <4m deep.

When questioned on what this might suggest about the condition of the containment, they refused to speculate. The PR strategy was basically to instead repeatedly emphasis the fact that the measured temperatures closely matched their existing estimates (see tsutsuji's post above).

 

[zapperzero]

Does anyone have a clue what exactly this ERSS is monitoring? Reactor data (pressure, temperatures) for example?

I remember reports that some/all of the radiation sensors set up on the plant's perimeter were down. Just a guess.

 

[elektrownik]

You can download now full video from unit 2 inspection: http://www.tepco.co.jp/tepconews/pressroom/110311/index-j.html

 

[duccio]

The 30/50 mS/h where they were working with the endoscope, do you believe it is from the dust inside of the building, or from the corium and the walls of the PCV aren't thick enough to shield it completely?

 

[Rive]

The wall of the PCV is thick enough to be a shield against a reactor on full steam (what means the whole inventory AND the working reactor together). For now, there is only the inventory.
So my bet is on the contaminated building.

 

[zapperzero]

I skimmed all 4 of the videos. I see girders and corroded piping, the lining of the PCV (lots of that), I see some kind of grille or walkway, I see what looks like garden hoses but should be hydraulics conduits for the control rod drives.

I do NOT see streams of water (the "rain" notwithstanding), nor do I see standing water anywhere in the videos.

All in all, it looks as if aside from the downpour, nothing is amiss. Very odd.

In other news, it's amateur hour all over again at TEPCO... The camera was stuck on the business end of the scope, knowing full well that it's going into a high radiation field...

 

[tsutsuji]

http://mainichi.jp/select/jiken/news/20120120ddm001040022000c.html The endoscope investigation was done by 34 Tepco employees who worked from the inside of a shielded cabin [see diagram]. The maximum exposure was 3.7 mSv (less than the planned exposure of 5 mSv). The peeling off of the painting of the PCV wall reveals that it was exposed to high temperature and high humidity for a long time.

http://www.shimbun.denki.or.jp/news/main/20120120_04.html The endoscope was able to look down to the grating (PCV first floor) at OP 9.5 metre, so that the water level must be lower than this. As part of severe accident countermeasures, a water level gauge is installed at OP 8.3 m, which switches on when submerged, and this switched on signal is being received. For this reason, it is possible to estimate that the water level is between OP 8.3 and OP 9.5 m, but Tepco said : "the integrity of the water level gauge is unclear, so it is necessary to carefully evaluate that matter". Pictures are extremely unclear because of the radiation noise and of the water drops dripping on the camera. Tecpo said "as the water drops will be reduced as the reactor is further cooled, our main problem is the radiations". Unit 2 was chosen because a penetration was available and with consideration for working safety. At unit 3 a penetration is available, but the radiations in the reactor building are high, and working conditions are difficult. Concerning unit 1, whether a suitable penetration is available or not is being investigated. At present there is no plan to perform endoscope investigation in those two units, as the priority is to analyse the results of unit 2's endoscope investigation in detail.

http://www.tepco.co.jp/en/news/110311/index-e.html unit 2 endoscope videos are available

 

[Yamanote]

Well, so no special news from the endoscope investigations, except the water level thing.

I find it somehow interesting to see the current status of the cleanup work at Fukuichi:
http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120120_02-e.pdf

What do you think, good progress, bad progress? Everything possible is done? Or much more could/should be done?
I would really appreciate to read your opinion.

 

[Rive]

Some pictures after cleanup attached, some others - maybe: a mosaic - is in progress... Does somebody recognizes anything?

Ps.: there is too much 'rain' inside... IMO it's not the condensed water but the cooling water.

 

[Joffan]

I didn't find the radiation noise a real problem in viewing those videos. You pretty quickly cancel it out. The "rain" was occasionally a problem but at least it gave a sense of where "up" and "down" are.

Nice picture clean-up Rive, I look forward to more!

 

[duccio]

In the second picture of Rive's, it seems that the C shaped bar has melted or anyway has deformed. Anybody with an opinion on that?

 

[dezzert]

Recent news about emergency power for sensors being disconnected in November 2010:

Does anyone have a clue what exactly this ERSS is monitoring? Reactor data (pressure, temperatures) for example?

The Emergency Response Support System (ERSS) is not what failed at the plant. It was the media converter, a device which relays real time temp and radiation readings from the reactors to both the ERSS and SPEEDI. The reason it wasn't functioning is because four months previous the line connecting it to a power source was cut and Tepco couldn't find a cable long enough at the time to reconnect, so they left it as it was, as they didn't consider it an "urgent task".

http://mdn.mainichi.jp/mdnnews/national/news/20120120p2a00m0na008000c.html

There are conflicting media reports concerning this data feed. Depending on which article or report you read it was operational at some point in time on the 12th, 13th or not at all. Ill research more

 

[NUCENG]

Some pictures after cleanup attached, some others - maybe: a mosaic - is in progress... Does somebody recognizes anything?

Ps.: there is too much 'rain' inside... IMO it's not the condensed water but the cooling water.

Without some sense of scale I can't be sure but the first picture shows a 90 degree elbow with threaded fittings. That may be a cooling water line to the drywell coolers. The second picture has dense packed metal tubes within some curved supports. I don't think they are CRD guide tubes because that would be inside the shield wall. They could be CRD hydraulic lines outside the shield wall. No guarantees. I'll wait for the mosaic.

 

[Rive]

I'll wait for the mosaic.

Sorry, I can't do it as it seems :-( The trick requires plenty (hundreds) of frames about the same view, and - due the spherical distortion of the cam - from the same position. There isn't enough of this kind of frame series in the released videos. Even small movements are problematic, because the noise prevents any automated alignment algorithm to be effective.

There will be only a dozen 'enhanced' picture soon, but most of them from different viewpoints. They will not fit for a mosaic.

About the scale: what's illuminated there is close to the cam. This can give a hint. I think the yellowish tubes are ~ 1 inch, the brown packed ones maybe 2 inch in diameter.

 

[SteveElbows]

In the second picture of Rive's, it seems that the C shaped bar has melted or anyway has deformed. Anybody with an opinion on that?

If you are referring to its slightly curved appearance in that image, I think we'd need to take into strong account the possibility of slight image deformation caused but the lens setup of the endoscope.

 

[clancy688]

And what is with unit 2 temperature: http://www.tepco.co.jp/nu/fukushima-np/f1/images/12011612_temp_data_2u-j.pdf ?

Just FYI, the sensor's gone by now.

http://www.tepco.co.jp/en/nu/fukushima-np/f1/images/12012212_temp_data_2u-e.pdf

So first it measures rising temperatures at the CRD. And then suddenly it's giving us readings from Pluto. Or some other planets where it's as cold as -200°C.


I guess there are two likely answers for such a behaviour:

1) Something heats up the sensor until it fails
2) The sensor was broken all along

So what are the implications of the first case? Corium flowing out of the RPV, first heating the sensor up and then killing it? But why ten months after the shutdown?

 

[jim hardy]

sounds like wet extension wires to me.

thermocouple effect, dissimilar metals in contact with each other, gives you tens of MICRO-volts per degree.

battery effect, dissimilar metals in contact with electrolyte, gives tens or hundreds of MILLI-volts, usually overwhelming the theromcouple.

negative temperature is pretty good clue.

have they changed water injection recently?

 

[Rive]

Some more pictures.

Ps.: don't ask about the orientation...

 

[zapperzero]

don't ask about the orientation...

well, the grid thing is a walkway below the penetration level, so that's "down"

 

[jim hardy]

been seawater in there?

 

[zapperzero]

been seawater in there?

Monday, March 14 2011 seawater injection was first attempted at reactor 2 (containment breach occurred the next day).

As water flowing from the reactor building basement to the turbine building basement was found later to be contaminated heavily, we can assume that there is a direct path for water to flow through the RPV and then the PCV/torus walls.

 

[jim hardy]

there was talk at one time of flooding the containment
which cools the vessel directly from its outside
and is a suggested mitigation action in that (now famous) ORNL report.

but i don't remember hearing whether they actually did it.

 

[Rive]

It was for the first month, as I recall, and they had given up with it when they noticed that the water actually pumped in had to be enough to fill the containment several times.

 

[NUCENG]

If you are referring to its slightly curved appearance in that image, I think we'd need to take into strong account the possibility of slight image deformation caused but the lens setup of the endoscope.

No argument from me. Your interpretation is just as likely as mine. But it looks curved to me.