Japan Earthquake: nuclear plants Fukushima part 2

[jim hardy]

Thanks.

I'd missed this
http://www.world-nuclear-news.org/R...st-fuel-remains-in-unit-2-vessel-2907164.html

29 July 2016

Most of the fuel that melted in unit 2 of the damaged Fukushima Daiichi plant in Japan remains within the reactor pressure vessel, an examination using a muon detection system indicates.

Speaking of imagery from the upper inside pedestal area, one can get unit 2 and 3 mixed up. Main rule is, If it doesn't look like a complete wreck, it is from unit 2.

Being under water doesn't help.

What are these instruments? Looks like they experienced some physical abuse. I think maybe @Hiddencamper has been under a BWR...

https://www.flickr.com/photos/simplyinfo/albums/72157683819520183/page2

 

[MadderDoc]

What are these instruments?

The images are looking up at the hanging bottom ends of some of the Control Rod Drive Mechanisms (CRDMs) in unit 3 (except for the smaller one with the funny bent and cut off thing coming out it, which is some other kind of tube, probably for some instrumentation or sensors). There should be looping black tubes connecting up to all the bottom ends, we see only some cut-off remnants of the metal leads for signal readouts, which were inside the tubes. During the pedestal inspection, the robot shot videos of this same area on two separate days, thus providing a view from two different angles.

In the top left hand side of the image to the left below, something looking like being of the blackish lava type of unit 3 is visible- apparently a portion of it has come stuck up here at this level of the pedestal. In the top middle of the image to the right, we see reflections from the robot lights in the water surface up above. We have unobstructed view from below to these tormented 'thingies' because the heavy metal construction that should normally be underneath them, has gone. According to the video, in the visited part of the pedestal of unit 3, the robot didn't find anything at the level of the CDRMs bottom end, that didn't look a total wreck.

 

[jim hardy]

"Tormented"
...
i'd say there's been some violence down there.

 

[MadderDoc]

i'd say there's been some violence down there.

Yeah. "Let us give it a good hosing before we jump to the conclusion that anything is damaged" doesn't seem to apply. Here is a cut away model of a BWR which I fell over. It is simplified, but quite instructive, if one is not a BWR guy. Down below we see the CRDMs in their welded-in housings, coming down from the bottom outside of the RPV into the pedestal area, and, inside the vessel, the main components the pistons of the CRDMs are working with.

 

[Sotan]

On the IRID site there is a section about a symposium dated 24 Aug from which I took these two links to PDF documents (in Japanese)

http://irid.or.jp/_pdf/Sympo2017_Kiyoura.pdf
"Pursuing the fuel debris". 1) Assumptions regarding the spread of fuel debris 2) Investigations (muon scanning, robotical inspections of PCV) 3) plans for the future. More investigations into the PCV, investigations in the RPV, sampling of the fuel debris. Page 44: possibility of opening a hole at the top of the RPV to use for inspection.

http://irid.or.jp/_pdf/Sympo2017_Okuzumi.pdf
Current stage of IRID research on removing the fuel debris.
1) techniques for repairing the PCV and stopping water leaks 2) technologies for removing the fuel debris, with access from the top, lateral access, and safety measures; 3) collecting, transporting and storing the removed debris.

If something draws your eye, I can try to translate those portions.

 

[MadderDoc]

Being under water doesn't help.

That is true. One needs to add a layer of imagination in order to picture, how these CDRM endings looked years ago. They are of stainless steel themselves, but globs of corrosion products have accumulated around bolts, as they have on other steel constructions seen in the imagery. Scrubbing away those tolls of time, the stainless steel portion may not be degraded that much, not visually at least. That puts some sanity limits on what temperature they can have been heated up to. However, the robot found nothing looking like the intact black rubberhose-like signal tubings above them, or below them, which were once there, and which we see a lot of in unit 2. There appears to have been heat enough to destroy them utterly. From the endings seen in the pictures you posted can be seen only short remnants of denuded, likely metallic, leads coming out, if anything at all. As you say, they appear to have suffered some violence, the way they have been bent.

 

[MadderDoc]

http://irid.or.jp/_pdf/Sympo2017_Kiyoura.pdf
"Pursuing the fuel debris". 1) Assumptions regarding the spread of fuel debris <..>

On page 8 are estimates at the current time of the whereabouts of debris ( in total 279, 237, and 364 tons in unit 1, 2 and 3 respectively). Of which, according to the estimate, very little (15, 42, 21 tons respectively) remain inside the RPV bottom, while the main part of the debris (264, 195, 343 tons in unit 1, 2 and 3 respectively) is estimated to have accumulated at the bottom of the PCV, inside the pedestal, or flowed outside it through the workers entrance.
Debris, that would include fuel debris, as well as debris of other degraded parts of the RPV internals, I reckon.

 

[jim hardy]

If this was already discussed i apologize. News to me, though
http://www.jaif.or.jp/en/new-data-obtained-on-debris-locations-based-on-temperature-changes-using-reduced-injections-of-water/

TEPCO made use of records of dozens of thermometers installed in each of the RPVs and elsewhere at Units 1 to 3. At Unit 1, temperatures near the control rod drive mechanism below the RPV rose as the volume of injected water decreased. The power utility believes that the debris that fell toward the bottom of the RPV was caught by the mechanism, becoming a heat source. Most of the debris is thought to have dropped to the bottom of the containment vessel.

At Unit 2, the temperature at the bottom of the RPV rose distinctively, so TEPCO thinks that there may be debris present there. At Unit 3, meanwhile, the temperature of the water in the containment vessel was higher than at the bottom of the RPV. TEPCO believes that most of the debris there dropped from the RPV, remaining at the bottom of the containment vessel.

http://www.jaif.or.jp/en/fuel-debris-at-fukushima-daiichi-2-mostly-found-at-bottom-of-reactor-pressure-vessel/ The results match those of the investigation of temperature change using reduced injection water. The company will continue its investigations and try henceforth to ascertain the positions of the debris more accurately.

Where there's heat there's fuel.
Significant melt-through on 3, not 1 & 2 ?
Still tentative but based on real data and sound reasoning .
And not contradicted by photo evidence so far.

Samples will nail it down.

 

[MadderDoc]

If this was already discussed i apologize. News to me, though
http://www.jaif.or.jp/en/new-data-obtained-on-debris-locations-based-on-temperature-changes-using-reduced-injections-of-water/
Where there's heat there's fuel.

I don't think it was already discussed here. It would have been nice if the JAIF had provided a link to the reported Tepco compilation of data and the actual records of the alleged 'dozens of thermometers' in each of the RPVs and elsewhere at the units.

It stands to reason, that if the unit 3 bottom of the RPV is cooler than the standing water in the PCV, then the RPV bottom is heated by the water, not the other way around. As to unit 2, we are only told that the temperature of the RPV bottom 'rose distinctively', when water injection was reduced. And, for unit 1, only that temperatures near the CRDMs 'rose'. We are left to guess, if and how all those other 'dozens of thermometers' in the units reacted to the change.

"TEPCO made use of records of dozens of thermometers installed in each of the RPVs and elsewhere at Units 1 to 3. At Unit 1, temperatures near the control rod drive mechanism below the RPV rose as the volume of injected water decreased. <..> At Unit 2, the temperature at the bottom of the RPV rose distinctively,<..>At Unit 3, meanwhile, the temperature of the water in the containment vessel was higher than at the bottom of the RPV."

 

[MadderDoc]

http://irid.or.jp/_pdf/Sympo2017_Kiyoura.pdf

On page 8 again, interestingly there is an infographic showing an exemplary RPV with a lot of its CRDMs apparently having fallen out from the RPV bottom complete with their housings. I don't remember seeing that possibility indicated in any infographics from before the pedestal area of unit 3 was inspected.

 

[jim hardy]

I don't remember seeing that possibility indicated in any infographics from before the pedestal area of unit 3 was inspected.

Something inspired that artist. A photograph would be nice..

the alleged 'dozens of thermometers' in each of the RPVs and elsewhere at the units.

I understand why they release information slowly both to quell wild speculation and to make sure they have answers to the reporters' questions that'll arise.

 

[MadderDoc]

Something inspired that artist. A photograph would be nice...

Yes. Sadly we have only video-snippets from unit3, those which Tepco selected for release, and nothing there seems grossly inconsistent with the artists expression.

I understand why they release information slowly both to quell wild speculation and to make sure they have answers to the reporters' questions that'll arise.

Right. If the robot actually managed to shoot a scene with CRDMs neatly lined up in place in unit 3, Tepco wouldn't necessarily include it in the video-release.

 

[jim hardy]

Right. If the robot actually managed to shoot a scene with CRDMs neatly lined up in place in unit 3,

I'd welcome that.
As a lifelong "nuke",
to see this coming out of my industry -
well, ... i think i know how Charlie Manson's Mom must've felt.

Setting emotions aside ---
were the CRDM's and vessel bottom found all intact
and a significant amount of core not in the vessel
the obvious question would be "How then did it get out?"

I think they're doing a pretty darn good job of investigating and apprising the public.
Samples will tell a lot . As their robot skills continue to improve they're getting close to that day.

Golly - we thought Mars robots were a challenge. These are underwater in high radiation environment.

old jim

 

[MadderDoc]

Setting emotions aside --- were the CRDM's and vessel bottom found all intact and a significant amount of core not in the vessel the obvious question would be "How then did it get out?"

That would be an unexpected outcome. I'd say, least implausibly through the RPV wall somewhere close to the bottom and above the RPV skirt. Debris could then be found outside the pedestal. We do have splatter on the CRD rail outside the pedestal in unit 2, but fortunately also an apparent localized damage of CRDMs up and to the left from the degraded rail end, inside the pedestal, to connect the splatter with.

In comparison with that, going in with the CRD rail in unit 3 everything looks intact, neat and tidy all the way to the apparently pristine end of the rail at the pedestal entrance. Inside, sudden change of scene -- wreckage, utter destruction, nothing really intact. Up and to the left can be seen just a few remaining pieces of the CRDM layer, obviously broken, a bare fraction of what should be visible of it. Below masses of molten now solidified material. How then did it get out..

 

[Sotan]

The most recent English translation of the Mid- and Long-term Roadmap Progress monthly report (of July 27) has been posted online on Aug 31.
http://www.meti.go.jp/english/earthquake/nuclear/decommissioning/pdf/20170727_e.pdf

 

[jim hardy]

In comparison with that, going in with the CRD rail in unit 3 everything looks intact, neat and tidy all the way to the apparently pristine end of the rail at the pedestal entrance. Inside, sudden change of scene -- wreckage, utter destruction, nothing really intact. Up and to the left can be seen just a few remaining pieces of the CRDM layer, obviously broken, a bare fraction of what should be visible of it. Below masses of molten now solidified material. How then did it get out..

What pictures are you looking at ?
http://photo.tepco.co.jp/library/170719_01/170719_05.jpg

Are those bolts bent or is it a fisheye lens effect ?

EDIT:

Ahhh now i see

that picture is about minute 1:41 on this video from July 19th
http://www.tepco.co.jp/en/news/library/archive-e.html?video_uuid=qf64ne97&catid=61785
247 meg for a two minute video ? Must be good resolution.

Anyhow, I've never been under a BWR so it's all unfamiliar
but it doesn't look shipshape.

 

[MadderDoc]

that picture is about minute 1:41 on this video from July 19th
http://www.tepco.co.jp/en/news/library/archive-e.html?video_uuid=qf64ne97&catid=61785
247 meg for a two minute video ? Must be good resolution.

There are 3 of them for the three consecutive expeditions. 6min/715 MB combined. Yes, they are quite good. I'd say the resolution 1920x1080 is a bit overblown for the information contained. The exact picture there is apparently not in the snippets included in the video, and the video has been cropped and likely degraded by recompression. The exact picture there, from the Tepco site, has effectively a better resolution.

I see 5 bolts in the foreground and 3 bolts lurking behind, and that appears to be how many remain there, which is striking. There are obvious perspective effects, but to be sure they are not all 8 of them in place oriented relative to each other as they used to be.

 

[turi]

I don't think it was already discussed here. It would have been nice if the JAIF had provided a link to the reported Tepco compilation of data and the actual records of the alleged 'dozens of thermometers' in each of the RPVs and elsewhere at the units.

The thermometers currently used are: http://www.tepco.co.jp/en/nu/fukushima-np/f1/pla/2017/images/figure-e.pdf referenced here http://www.tepco.co.jp/en/nu/fukushima-np/f1/pla/index-e.html
Historical values (twice a day) can be found here: http://www.tepco.co.jp/en/nu/fukushima-np/f1/pla/2017/index-e.html Unfortunately that data isn't very userfriendly...
I believe to remember a nicer interface for the historical temperature data but can't seem to find it.

 

[MadderDoc]

The thermometers currently used are: http://www.tepco.co.jp/en/nu/fukushima-np/f1/pla/2017/images/figure-e.pdf referenced here http://www.tepco.co.jp/en/nu/fukushima-np/f1/pla/index-e.html
Historical values (twice a day) can be found here: http://www.tepco.co.jp/en/nu/fukushima-np/f1/pla/2017/index-e.html Unfortunately that data isn't very userfriendly...
I believe to remember a nicer interface for the historical temperature data but can't seem to find it.

Thank you turi. There are included in that page links to 1 hour and 6 hour measurements in comma separated data files, they can be read into a spreadsheet and graphed easily. Still, I may be blind, or it may be the wrong thermometers included there, but I do not find the pattern of temperature change, like the one referenced by the JAIF, accompanying changes in water injection in that data.

 

[turi]

[...]Still, I may be blind, or it may be the wrong thermometers included there, but I do not find the pattern of temperature change, like the one referenced by the JAIF, accompanying changes in water injection in that data.

Me neither. Not even in the separately linked files for water injection change days for unit 1 (e.g. http://www.tepco.co.jp/en/nu/fukushima-np/f1/pla/2017/images/20170125_pcvtemp1u-e.pdf). I don't see any special pattern.

 

[MadderDoc]

I don't see any special pattern.

Glad that I am not alone. :-) Of particular interest could be unit 2, where reportedly a distinct rise in temperature should have been observed at the RPV bottom accompanying the reduction in water injection rate. I may have another go of it tonight.

 

[jim hardy]

I see 5 bolts in the foreground and 3 bolts lurking behind, and that appears to be how many remain there, which is striking. There are obvious perspective effects, but to be sure they are not all 8 of them in place oriented relative to each other as they used to be.

I don't know what or where it is, or even where it belongs. i'll have to wait 'til the "For Dummies" video comes out.

What went on down there is far from figured out. Or at least far from explained.
Plastic gone? Steel bent ? Looks that way a this early stage.

That's how disaster investigations go - painstakingly slow.

 

[MadderDoc]

I don't know what or where it is, or even where it belongs.

Well, the 8 bolts are somewhere, where should be a literal forest of lined up bolts. There's a reference photo from unit 5 below. The bolts hold a criss-crossing jigsaw puzzle of steel elements together and up to provide a structure underneath the CRDMs that would restrict the downward motion of CRDM housing tubes in case untoward conditions inside the RPV should make their welds inside the RPV to fail. Unrestricted, the housing tubes might fall out of the RPV bottom, which could be catastrophic.

 

[MadderDoc]

What went on down there is far from figured out. Or at least far from explained.
Plastic gone? Steel bent ? Looks that way a this early stage.

Indeed. Referring to the objects that are visible in the reference image from unit 5 in previous post, nearly all of it appears to be gone in unit 3. Of the rotatable platform remain in place (sort of), apparently only the supporting rail construction along the pedestal inside wall. Tepco think hundreds of tons (the equivalent gross vehicle weight rating of about two dozen heavy trucks) of more or less molten material from the RPV fell out of it, and passed through this area.

 

[jim hardy]

Too turbid to see very far through the water

Blowing your today at 10 AM image up to 3x and snipping

might it be about here ?

 

[MadderDoc]

Too turbid to see very far through the water
Blowing your today at 10 AM image up to 3x and snipping
might it be about here ?

Yes, I think you've got directions right, caveat though the reference photo is from unit 5, where geometry/orientation may differ. From the second day of the expedition under unit 3, there is another interesting snippet with a view up to a section of remains of this bolted layer. It must have been shot somewhere across the room from the pedestal entrance, close to the opposite wall. The stains on the wall conveniently define the direction of vertical. It is from about 0:35 in this video:

 

[jim hardy]

the second day of the expedition under unit3, there is another interesting snippet with a view up to a section of remains of this bolted layer. It must be shot somewhere across the room from the pedestal entrance, close to the opposite wall. It is from about 0:35 in this

About 1:35 you can see what i think is a CRDM bottom flange above the rack, looks like it's where it belongs.

But yikes what a mess. Broken pipes, sludge,

need those samples..

 

[MadderDoc]

About 1:35 you can see what i think is a CRDM bottom flange above the rack, looks like it's where it belongs. But yikes what a mess. Broken pipes, sludge, need those samples..

Yes, you see several CRDM bottom flanges up there above the bolted layer in that snippet. Bordering to that same area, you see some, er, sludge, which appears to have come down and solidified while slithering down through the bolted layer. After solidification, apparently the bolted layer has given in towards center of the construction, leaving 'sludge-stalactites' hanging on there, close to the wall, in an awkward skewed direction relative to vertical. Samples would be nice, but it is kind of a samplers nightmare, considering the inhomogenity of the mess.

 

[MadderDoc]

BTW, in the same video, the 'layer cake' we talked about earlier appears at about 1:53. I've come to think of that whatever solidified material those succesively added layers consist of, one cannot assume that the toll of time doesn't affect such solidified material. Erosion or crack off could explain the now ragged edges of the layers. They may originally have been laid out more 'elefant foot like'.

 

[MadderDoc]

Me neither. Not even in the separately linked files for water injection change days for unit 1 (e.g. http://www.tepco.co.jp/en/nu/fukushima-np/f1/pla/2017/images/20170125_pcvtemp1u-e.pdf). I don't see any special pattern.

I did give it another go regarding the reportedly distinct rise in RPV bottom temperature when injection was reduced in unit 2 in late February-March this year. It is true that temperatures relating to the lower RPV has been generally increasing from about the time injection rate was reduced, but so has the temperature of the injected water (and so has the temperature of the PCV). Looking at the difference between the temp. of the injected water and the RPV temperature, there appears to have been an up-tick of about 1-2K when injection through the core spray line was reduced, but none earlier, when injection through the feed water line was reduced. That could be taken as an indication of the presence of a heat source inside the RPV, which is being cooled or cooled better by core spray injection, than by injection through the feed water line.

 

[MadderDoc]

In regard of the recent observations on the state of affairs in unit 3, and previous theories that a steam explosion could have been involved in the explosive event in the unit on March 14th 2011, one might take note of the more recent results of the PULIMS and SES experiments on the possibility of steam explosions in molten core-coolant interaction in a stratified configuration.

It has previously been believed that a steam explosion would not likely occur, in the absence of premixture of the molten material (e.g. by jet expulsion from the RPV). The experiments have shown this not to be the case; in the experiments spontaneous steam explosions frequently occurred, also when the molten material was laid out under relatively shallow and somewhat subcooled (~10K) water without prefragmentation of the hot melt, and with conversion rates heat energy-->kinetic energy at about 1-3 %.

https://www.researchgate.net/publication/280719489_Investigation_of_Steam_Explosion_in_Stratified_Melt-Coolant_Configuration
https://www.researchgate.net/publication/280719566_Insight_into_steam_explosion_in_stratified_melt-coolant_configuration

 

[Rive]

in the experiments spontaneous steam explosions frequently occurred

Sigh. Am I right that these experiments were conducted on atmospheric pressure?
Just because the behavior of molten mass-water mixture heavily depends on the pressure. What's needed is some pressurized experiment.
Just think about (deep)underwater lava flows. The whole stuff works entirely different than a mere surface lava flow.

BTW, is there a possibility of water in DW at the time we suspect the RPV rapture?

 

[MadderDoc]

Yes, these experiments were conducted under atmospheric pressure. I can't see how the possibility of water standing in the bottom of the DW can be excluded, seeing they were pumping water into the RPV but were apparently not able to raise the level of water inside it.

 

[jim hardy]

Fascinating read. Doc
sure makes sense.
There are a lot of Youtubes of foundry accidents involving molten metal and small amounts of water

 

[jim hardy]

Here's one for you , Doc

http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/35/041/35041887.pdf