Japan Earthquake: nuclear plants Fukushima part 2

[turi]

SPF 4 has been successfully emptied.

 

[Sotan]

On December 26 Tepco presented to the Nuclear Regulation Authority a report on the progress of the filling of trenches.
The report - in Japanese - is here:
http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/data/0030_01.pdf

They have data indicating that the tunnels were filled correctly, as planned, with the ~2500 m³ of mixture which they poured in the water.

Page numbered 6 in this report shows the results of tests after filling in the trenches of Reactor 2.
They removed water from two shafts and checked water levels in the other places to see if they change (thus indicating that water is still passing through the filled trenches).
Out of 4 tunnels, 2 seem to be watertight, while the other 2 still allow a water flow estimated at 20-400 l/h.
Additional action will be needed to stop this water flow completely.
Trenches of Unit 3 and 4 are to be filled using similar methods and on the basis of the experience gathered at Unit 2.

 

[Sotan]

I just watched a short NHK TV news piece reporting on the fact that TEPCO has announced it will not be able to meet the March deadline for treating all the water stored in tanks on site at Fukushima Daiichi plant. Two links on this subject:

http://www3.nhk.or.jp/nhkworld/english/news/nuclear.html
http://www.tepco.co.jp/en/press/corp-com/release/2015/1247689_6844.html

Other news:
Two workers died recently in work related accidents at Fukushima Daiichi:
http://ajw.asahi.com/article/0311disaster/fukushima/AJ201501210064

 

[Sotan]

Asahi Shinbun article about the scheduled investigation of the molten fuel location using muons:

http://ajw.asahi.com/article/0311disaster/fukushima/AJ201501240039

 

[etudiant]

TEPCO is certainly advancing the state of the art in nuclear accident management.
ALPS is globally unprecedented afaik, this muon scanning is likewise new to the nuclear power world. If memory serves, muon detectors have been used to try to locate possible hidden chambers in the pyramids, so the technique is established.
Picking up the relatively small lumps of nuclear fuel will be challenging, especially as the positioning of the detectors will be restricted.
Even so, good on Japan, their efforts to clean up this mess are beginning to bear some fruit.

 

[Sotan]

New Mid- and Long Term Roadmap report documents available here (in Japanese:)
http://www.tepco.co.jp/nu/fukushima-np/roadmap/conference-j.html

From among them, I would like to single out, for now, this interesting document:
http://www.tepco.co.jp/nu/fukushima-np/roadmap/images/d150129_14-j.pdf

It contains sketches of proposals for investigating and removing the melted fuel debris submitted by various companies/entities.

I only took a glance at the document, will study it more later, but I already found it interesting that they are seriously considering approaches for debris removal which do not require filling the reactors with water. (Probably as a preparation for the case when they cannot be made water-tight.)

There are also various proposals for devices and robots for imaging, cutting.

A more comprehensive report on the progress in various areas is expected to be available by the end of March.

 

[nikkkom]

TEPCO is certainly advancing the state of the art in nuclear accident management.
ALPS is globally unprecedented afaik

I'm actually yet to hear why ALPS - apparently, a very complex apparatus, judging by frequency it breaks down - is necessary; why a "simple" water treatment via filtration and distillation was not used instead.

You can say that "TEPCO are not idiots, they would surely use that if it would work". I'm not convinced that "TEPCO are not idiots"... call me a cynic. This organization proved to be quite capable to act stupidly as a whole. Maybe they just refused to back down, admit that this ALPS thing was a mistake?

 

[Sotan]

NHK English article of Jan 30: "New findings on fallout"
http://www3.nhk.or.jp/nhkworld/english/news/nuclearwatch/20150130.html

 

[etudiant]

I'm actually yet to hear why ALPS - apparently, a very complex apparatus, judging by frequency it breaks down - is necessary; why a "simple" water treatment via filtration and distillation was not used instead.

You can say that "TEPCO are not idiots, they would surely use that if it would work". I'm not convinced that "TEPCO are not idiots"... call me a cynic. This organization proved to be quite capable to act stupidly as a whole. Maybe they just refused to back down, admit that this ALPS thing was a mistake?

Does distillation actually work for this kind of job?
The quantities of contaminants are minuscule, in the part per million or less class. Meanwhile the amount of water to be processed is around a half million tons, so it is a refinery sized facility that would be needed. Distilling on that scale to the level; of purity required may be even more challenging than making ALPS work.
Is there anyone on PF from the chemical/refining sector on this forum who could speak from expert knowledge?

ALPS is a filtration system, albeit a very complex one, because of the wide range of contaminants it is expected to deal with. I don't know if a 'simple' filtration is helpful in this case, where there are lots of dissolved nasties in very low concentrations.

 

[nikkkom]

Does distillation actually work for this kind of job?
The quantities of contaminants are minuscule, in the part per million or less class.

This would not make caesium or strontium salts any more able to escape distillator with steam.

Meanwhile the amount of water to be processed is around a half million tons, so it is a refinery sized facility that would be needed. Distilling on that scale to the level; of purity required may be even more challenging than making ALPS work.

Are you speaking from experience, or just guessing?

Saudi Arabia operates a number of desalination plants. For example, Yanbu Multi Effect Distillation Plant, distills 68000 m3 _every day_. Evidently, even such huge distillators exist.

TEPCO needs much smaller distillator. From what I read, double distillators are used as a STANDARD first stage in producing ultrapure water.
Let me use google...

http://www.alibaba.com/showroom/industrial-water-distillers.html
http://products.lulusoso.com/biz/Distilled-Distilled-Water.html
http://dir.indiamart.com/impcat/water-distillation-plant.html

Even a 5 minute search turns up units capable of processing several tons per hour.

I don't know if a 'simple' filtration is helpful in this case, where there are lots of dissolved nasties in very low concentrations.

In this case filtration needs to remove only contaminants which can clog the distillator, such as oil, dirt, sand and other particulates. It does not need to remove any dissolved salts. This is indeed not a rocket science, thus 'simple'.

 

[etudiant]

This would not make caesium or strontium salts any more able to escape distillator with steam.
Are you speaking from experience, or just guessing?

Saudi Arabia operates a number of desalination plants. For example, Yanbu Multi Effect Distillation Plant, distills 68000 m3 _every day_. Evidently, even such huge distillators exist.

TEPCO needs much smaller distillator. From what I read, double distillators are used as a STANDARD first stage in producing ultrapure water.
Let me use google...

http://www.alibaba.com/showroom/industrial-water-distillers.html
http://products.lulusoso.com/biz/Distilled-Distilled-Water.html
http://dir.indiamart.com/impcat/water-distillation-plant.html

Even a 5 minute search turns up units capable of processing several tons per hour.
In this case filtration needs to remove only contaminants which can clog the distillator, such as oil, dirt, sand and other particulates. It does not need to remove any dissolved salts. This is indeed not a rocket science, thus 'simple'.

Hi Nikkom,
My only experience has been working with lab scale distillation and HPLC for bio purposes, so big volumes are an unknown world for me.
My main concern is that on very dilute solutions, distillation does not seem to be a magic bullet.
Note that the various sites you so helpfully gave links for advertise 99.9 or even 99.99 % cleanup, presumably of salt. Perhaps that is that good enough, but I wonder.
I did not know the desalination plants were that big, wonder what their fuel use is, but clearly a plant 1% that size should be no problem and would offer ALPS equivalent throughput.
So your question remains on the table, maybe distillation was the better way, or perhaps there was a reason for ALPS that is still undisclosed.

 

[Sotan]

There is a new press release in English on Tepco site:
http://www.tepco.co.jp/en/press/corp-com/release/2015/1247946_6844.html
"ADVANCES IN FUEL REMOVAL, WATER AT FUKUSHIMA NOTED IN MOST RECENT QUARTERLY REPORT"
A link is provided to a summary of the report, in English - a lot of information in there.
Plus there's a link to a video with comments of Dr. Dale Klein, " former chairman of the U.S. Nuclear Regulatory Commission, who chairs the Nuclear Reform Monitoring Committee overseeing TEPCO's progress in implementing its Nuclear Safety Reform Plan".

 

[Sotan]

http://www.tepco.co.jp/en/press/corp-com/release/2015/1248057_6844.html
Fukushima Daiichi NPS Prompt Report (Feb 09,2015)
Recent topics: COSMIC "MUON" RAYS TO LOOK INSIDE FUKUSHIMA REACTORS AS TEPCO BEGINS TESTING

A few photos with the installation works:
http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2015/images/handouts_150209_01-e.pdf

 

[gmax137]

Anyone have a link to current or at least recent dose rates / contamination levels in the countryside surrounding the plant? Is there a source for updated dose maps? Thanks.

 

[turi]

Anyone have a link to current or at least recent dose rates / contamination levels in the countryside surrounding the plant? Is there a source for updated dose maps? Thanks.

http://new.atmc.jp/
http://jciv.iidj.net/map/

 

[Sorai]

Anyone have a link to current or at least recent dose rates / contamination levels in the countryside surrounding the plant? Is there a source for updated dose maps? Thanks.

Yesterday the NRA released the latest map from the airborne monitoring survey: http://radioactivity.nsr.go.jp/ja/contents/11000/10349/24/150213_9th_air.pdf It covers an 80 km radius from the plant, the values represent dose rates at 1m height, decay corrected to Nov 7, 2014.

There would be an English translation later on I assume, but the translation of previous reports can be accessed here: http://radioactivity.nsr.go.jp/en/list/307/list-1.html and here: http://radioactivity.nsr.go.jp/en/list/203/list-1.html

The latest one to include estimates of surface contamination by Cs-134 and Cs-137 is this one: http://radioactivity.nsr.go.jp/en/contents/7000/6936/24/270_0513.pdf (it only covers the evacuation areas.)

There is also an extension site which includes these and several other survey results on a zoomable map and larger PDF files with local maps: http://ramap.jmc.or.jp/map/eng/ You can click where it says "As of November 7, 2014", choose an earlier survey, and the check the different boxes to access available data (either air dose rates or ground contamination.)

Apart from that, Fukushima Prefecture has a map with fixed monitoring post data which updates daily: http://fukushima-radioactivity.jp/ (you can zoom and click on a specific monitoring station.)

There is also an NGO called Safecast that has a lot of cool maps based on car rides with mounted Geiger-counters and fixed monitoring post data contributed by volunteers: http://blog.safecast.org/maps/ They have a world map where they upload results from all over the world, but it seems it conflates data from the last 4 years on a single image, so I'm not sure it's representative of the current values around the plant (Cs-134 was the main contributor to the air dose rate early on, but it must have decayed to close to 27% by now): http://safecast.org/tilemap/

 

[Sotan]

This is an old thing (October 26, 2014) but I have just seen it and it was... impressing, so to speak:
A simulation of the sloshing that occurred in Unit 1 spent fuel pool during the earthquake.


Are there usually any measures taken in nuclear power plants against this phenomenon?
The case of tanks used to transport liquids by road, or that of firetrucks, comes to mind.

 

[turi]

Tepco has a (new?) english overview page showing the different robots beeing used on site: www.tepco.co.jp/en/decommision/principles/robot/index-e.html

 

[Sotan]

NRA press release of Feb 25 regarding the most recent trouble at Fukushima Daiichi.
Possible Flow of Contaminated Water to the Outside of the Controlled Area of Fukushima Daiichi NPS
http://www.nsr.go.jp/data/000098312.pdf

About the same subject, from NHK:
http://www3.nhk.or.jp/nhkworld/english/news/20150225_13.html

Some sites are speculating that this might have been going on ever since the accident...

 

[Astronuc]

This is an old thing (October 26, 2014) but I have just seen it and it was... impressing, so to speak:
A simulation of the sloshing that occurred in Unit 1 spent fuel pool during the earthquake.

Are there usually any measures taken in nuclear power plants against this phenomenon?
The case of tanks used to transport liquids by road, or that of firetrucks, comes to mind.

The spent fuel pool is designed to provide cooling and shielding to spent fuel which sit in racks in the bottom of the pool. There should be at least about 10 m of water over the top of the fuel, based on I'm familiar with.

One input in the plant design is an acceleration curve based on some probable maximum seismic event. For such a design basis event, the depth of the pool should be sufficient to prevent loss of water and loss of shielding. In the case of Fukushima, they may have experience local accelerations beyond those in the original design. The other factor would be whether or not they lost the drainage or recirculation system, so that when the added water to the pool, it might have overflowed. I don't know if that is the case at Fukushima Daiichi, Units 1-4.

 

[Gary7]

The muon "x-ray" of Fukushima #1 showed no fuel in the reactor.

http://mainichi.jp/english/english/newsselect/news/20150320p2g00m0dm028000c.html

Edit: This article (below) has a visual... may be slightly more interesting than the previous.
http://mainichi.jp/english/english/newsselect/news/20150320p2a00m0na013000c.html

 

[LabratSR]

Here is TEPCO's release on the Muon imagery. The future investigation plans outlined at the bottom are interesting.

http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2015/images/handouts_150319_01-e.pdf

 

[Sotan]

On Mar 26 Tepco announced that there is a possibility that the sunk FHM in Spent Fuel Pool of Unit 3 might be in contact with (and perhaps has caused some damage) to the gate that separates the pool from the reactor well.

In order to better understand the situation as they are planning to remove the dropped FHM the investigated the area using the cameras used in the debris removal operatin, from the air and from underwater. A report on this is available here (in Japanes only):
http://www.tepco.co.jp/nu/fukushima-np/handouts/2015/images/handouts_150406_04-j.pdf

Apparently there are 2 gates that separate the SFP from the reactor well, designated as G1 (towards the pool) and G2 (towards the reactor well). G1 appears to be in good state, well fixed in its supports and its seal seems functional - in agreement with the fact that no loss of SFP water has been observed in time. However, G2 seems to have been changed shape/position during the accident. The FHM was found to have no contact with the gate, except for some thin sheet of metal touching it somewhere. They will use the information in the operation for removing the FHM from the SFP.

---------------------

As you know the muon imagery has brought new evidence suggesting that the fuel in Unit one has melted and relocated toward the base of the reactor (not clear where exactly). They are now planning important investigation around the pedestal of Reactor 1. This document shows the outline of the operation and its schedule (sorry, only in Japanese):
http://www.tepco.co.jp/nu/fukushima-np/handouts/2015/images/handouts_150406_03-j.pdf
The investigation consists of sending one shape-changing robot (equipped with camera, thermometer and radiation measurement device) through the 100mm diameter X-100B penetration and then have it walk over the grating located at first floor inside the PCV.
The robot investigation is planned for April 10 and 13 - perhaps the action is split in two as somewhere in the document it is stated that the robot will take a clockwise route up to a point, and then an anti-clockwise route for the remaining portion.
The results will be used, among other, in the planning of another investigation - this time down lower, outside of the pedestal.

 

[Rive]

Apparently there are 2 gates that separate the SFP from the reactor well, designated as G1 (towards the pool) and G2 (towards the reactor well). G1 appears to be in good state, well fixed in its supports and its seal seems functional - in agreement with the fact that no loss of SFP water has been observed in time. However, G2 seems to have been changed shape/position during the accident.

Quite interesting. Especially, because on the early days one of the main steam/heat sources around the U3 reactor well was rather close to those gates.

Ps.: it was said at one point that the steam there is just 'rainwater on the hot plate', but my personal opinion is, that the damage on the drywell/PCV cap there could be more extended than just the expected temporal leaking.

 

[Sotan]

By what mechanism do you think the G2 gate could have been damaged, while G1 escaped unharmed?
I don't have a clear image of the geometry of the area, but would it be possible for the falling FHM to hit, with some corner or some piece of its structure, the G2 gate, while (by total chance) missing gate G1? A beam or other object falling right in the space between gate G2 and the inside of the drywell and causing a wedge effect which practically dislocated one side of the G2 gate?

 

[Rive]

Here is the geometry, from the linked document:
http://keptarhely.eu/view.php?file=20150408v00gqxhsl.png

The 'steaming' locations, from the early days:
http://keptarhely.eu/view.php?file=20150408v00gtevln.jpeg
(The one on the right is not really visible, but I remember where it is - in the corner of the equipment pool and the drywell :) )

The same locations on a 'fresh' picture, with the pool gates visible:
http://keptarhely.eu/view.php?file=20150408v00gzoofr.jpeg

What I have in mind is, that steam pressure might be a reason of the relocation of the G2 pool: such event would not affect G1 (which is also has the water pressure on one side as advantage).

Of course right now it's just speculation.

 

[Sotan]

English material from Tepco presenting the Unit 1 PCV investigation by robot which has probably started today:

http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2015/images/handouts_150406_01-e.pdf

 

[Sorai]

English material from Tepco presenting the Unit 1 PCV investigation by robot which has probably started today:

http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2015/images/handouts_150406_01-e.pdf

It seems the robot got stuck a few hours after going into Unit 1:

"The robot entered the containment vessel through piping on April 10 at 9:30 a.m. It began its journey around the netted first floor of the vessel at 11:20 a.m. to measure the temperature and radiation levels while transmitting images of the surrounding conditions. But after covering about two-thirds of its planned route, the robot came to a standstill after 2 p.m.

According to an IRID official, the operators tugged on the robot's cable and sent instructions for it to change shape, but it still would not move. The robot’s camera, dosimeter and temperature gauge were not damaged, and the robot was still capable of transmitting data."
​

http://ajw.asahi.com/article/0311disaster/fukushima/AJ201504110035

 

[Sotan]

I am reading Tepco's press release (in Japanese) http://www.tepco.co.jp/cc/press/2015/1249672_6818.html

Indeed, the robot got stuck, doesn't look like it can be recovers, so tomorrow (April 13) they are going to cut it's cable.
Such a result was considered, and cutting the cable was one of the possible outcomes.
They are also postponing the other half of the investigation, in which they were planning to use a second robot to go the other half of the grating.

They did get some valuable data though. The robot managed to go two thirds of its intended route and covered 14 out of the intended measurement and imaging points.

 

[westfield]

Here is the geometry, from the linked document:
http://keptarhely.eu/view.php?file=20150408v00gqxhsl.png

The 'steaming' locations, from the early days:
http://keptarhely.eu/view.php?file=20150408v00gtevln.jpeg
(The one on the right is not really visible, but I remember where it is - in the corner of the equipment pool and the drywell :) )

The same locations on a 'fresh' picture, with the pool gates visible:
http://keptarhely.eu/view.php?file=20150408v00gzoofr.jpeg

What I have in mind is, that steam pressure might be a reason of the relocation of the G2 pool: such event would not affect G1 (which is also has the water pressure on one side as advantage).

Of course right now it's just speculation.

If we are having a stab at this then I think the steaming was the symptom of the problem, not the cause.

Have a look at the red circled keyway on the right in this image that you linked -
http://keptarhely.eu/view.php?file=20150408v00gzoofr.jpeg

Its one of the steaming locations but more alarming is how displaced the keyway is in relation to the gate. I noticed this years ago and to me it was perhaps a hint that the whole "ring" around the top of the containment vessel is fractured. At the time we couldn't see that the middle section of concrete "lid" over the containment vessel had been broken in half by the falling overhead crane, it must have placed enormous stain on that ring of concrete that normally supports it.

I think the sort of damage that has created that displacement on the big concrete gate to the DS pool (or whatever you would like to call that pool) could also allow the SFP "G2" gate to simply fall out of its track over on the other side. Its not clear enough to see if that's the case though.

P.S> Just be be clear - I am certainly not saying this has anything to do with a containment failure, this is just the concrete ring around the top of the containment vessel I'm referring to in relation to the U3 SFP "G2" Gate displacement.

 

[Gary7]

Video from the robot inspection of Unit #1 is up on YouTube. (Video is from a Japanese news program. Feel free to remove if it is against forum rules).


The still photos are also getting a lot of attention from the papers as well. They say the robot encountered radiation of between 7 and 9.7 sieverts inside the unit (which was in line with Tepco's estimates). Ambient temperature was between 17.8 and 20.2 Celsius.
http://www.tokyo-np.co.jp/article/national/news/CK2015041402000134.html

 

[Sotan]

- Even if it is very early, I would be interested to hear the comments of the knowledgeable people in this forum about what is seen in that video.
What is that yellowish stuff that can be seen on the grating here and there?

- Tepco has a PDF report with some explanations (in Japanese but worth a look as figures and photos make it almost understandable):
http://www.tepco.co.jp/nu/fukushima-np/handouts/2015/images/handouts_150413_02-j.pdf

-Page 2 shows the intended route of the robot, out of X-100B penetration and then to the right (anti-clockwise) toward investigation points B0...B17. (The other route, clockwise, from C0 to C11, planned for the other robot, can also be seen.)
-Page 3 mentions that the actual course (blue line) had to be corrected because of obstacles fallen on the grating, and that the robot got stuck somewhere around point B14. Green X signs mark the place of major obstacles. The 20mm scale shown on photos helps understand the size of some of those fallen objects (I don't know why but from the video I wrongly assumed they were much larger).
- Page 4: report on results regarding objectives 1 to 3 of the present investigation. (1) Access opening in the grating towards the lower floor was found to be in good condition, without major obstacles (in view of the planned investigation of the basis of the pedestal). (2) CRD rail (?) was not reached but there is some filming of CRD from the last point where the robot was active (images being processed now). (I don't know why this CRD rail was a major objective, I don't even know what it is.) (3) Along the traveled route no major destruction was observed; the HVH, PLR piping, walls of the pedestal showed no signs of major damage. Temperature and radiation values were measured along the way. (I don't know right now what HVH, PLR abbreviations stand for.)
- Page 5: Again we see the opening planned to be used to lower the robot down towards the basis of the pedestal. No major obstacles in the area.
- Page 6: Images from point B7. No major damage on the PLR piping (insulation). However there is some insulation material (?) fallen down on the grating.
- Page 7: View of the outside wall of the pedestal, in good shape (B3). View of the outside of the "machinery hatch" (?), in good shape, no major damage (B2).
- Page 8: Views from B1 point. No major destruction of HVH (D).
- Page 9: Radiation and temperature measurements.
- Page 10: In the narrowest portion of the route (between points B14 and B15) an obstacled was found and an alternative route was chosen. That's when the robot got stuck. But it managed to take some images in the direction of the CRD. Probable cause - robot rollers stuck in some uneven place formed between preexisting piping and the grating.
- Page 11: They measured about 10 Sv/h and under and are happy to see that the camera resisted 2-3 hours under such conditions. The second part of the investigation is being reconsidered to make use of the information achieved until now. A tentative schedule shows 13 to 17 April as the time window for this second attempt.
- Page 12: Mockup image showing the place where the robot got stuck.
- Page 13: Mockup image showing the CRD rail.

 

[Sotan]

- Correction to yesterday's post:
"Page 11: They measured about 10 Sv/h and under and are happy to see that the camera resisted 2-3 DAYS (not hours) under such conditions." (my apologies)

- There's a new pdf on Tepco's site (in Japanese) showing the planning o fthe second half of the investigation - using the clockwise route, which is probably under way as I post this.
http://www.tepco.co.jp/nu/fukushima-np/handouts/2015/images/handouts_150415_01-j.pdf

- Page 3: some new hypotheses about how the first robot got stuck. Probably one roller was rotating in the air as it caught an empty space, a wider gap in the grating, combined with a difference in height. They plan to advance more slowly (since the robot can last for 2-3 days at least) and more carefully this time.

 

[Rive]

Its one of the steaming locations but more alarming is how displaced the keyway is in relation to the gate.

I could not decide if it's really a relocation or just there is no rubble there to fill the hole.

Page 3: some new hypotheses about how the first robot got stuck. Probably one roller was rotating in the air as it caught an empty space, a wider gap in the grating, combined with a difference in height.

Ouch. That would be a really stupid mistake. They already lost a robot in U2 for another such 'facepalm'.

 

[jim hardy]

- Page 11: They measured about 10 Sv/h and under and are happy to see that the camera resisted 2-3 hours under such conditions.

A few tens of sv is about where NMOS semiconductors should start degrading from radiation.

"Page 11: They measured about 10 Sv/h and under and are happy to see that the camera resisted 2-3 DAYS (not hours) under such conditions." (my apologies)

Thanks for the update. I was puzzled why they'd not use parts with better rad tolerance. Now it appears they did, which makes sense...