Fukushima Japan Earthquake: nuclear plants Fukushima part 2

[MadderDoc]

Of course the core is still mostly or all in place you want to inject with whatever you have but if it's not you want to avoid a big pressure spike.

I can understand that. You'd be risking injection of water into a system in which water(steam) availability had been rate limiting for the exothermic Zr-water reaction, and seeing that reaction produces hydrogen, pressure could rise dramatically.

 

[jim hardy]

i've only added two lines to your picture to help me visualize the time frame

wetwell vent(purple) and explosion(red)

Stolfi's plot of pressure from data available at the time( i think they were manually logging it from gages, recall plant conditions then)
snipped from here http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/plots/cur/out/plot-un3-t-I-full.png
shows quite a pressure rise starting shortly after midnight on the 13th , about the time injection stopped.
I retrieved it because it shows wider range.
Caution log scale takes some getting used to but is great... He's a professor after all.

indeed it shows (red dots) pressure rose a lot

from the June 2011 gov't report to IAEA, for times:

the HPCI stopped at 2:42 on March 13. The reason for that appears to be a drop of pressure in
the reactor. The other probable cause could be water-vapor outflow from the HPCI system.
∙ (Status of the reactor core) The operation for injection of water containing boric acid
commenced using a fire extinguishing line at around 9:25 on March 13. However, the water
could not be injected sufficiently due to the high pressure in the reactor, and the water level in
the reactor lowered. As a result, water injection was halted at least for 6 hours and 43 minutes
after the HPCI stopped at 02:42 on March 13 until water injection using the fire extinguishing
line started at 09:25 on the same day.

It's ambiguous how much water the fire engines pumped in. Probably none until pressure got below ~300 psi , ~2000 kpa.
I don't know what made pressure drop so sharply around 9AM the morning of 13th but it does look to be same time as injection started via fire truck.

Could be that's when reactor vessel opened up to drywell - their pressures started tracking about 9:10
here's a snip of Stolfi's data from http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/plots/cur/data/pres-un3-t.txt

and that great graph he made showing that they indeed coupled
http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/plots/cur/out/pcor-PCA-PD-un3-full.png

.

Hard to believe it was seven years ago. I have forgotten a lot of what we analyzed back then.

BUt what's curious to me is -

IF there was 177 megawatts of heat being produced in that vessel,
and presumably tons of hydrogen gas as well...
Adding energy to gas usually raises its pressure...
THEN the time of heat production (purple in the NDF chart, first image in this post ) should correlate with the pressure rise around 3:30 AM, beginning of "without water injection" interval, not the pressure drop around 9 am at end of that interval ?

just one of those little physics things my pea brain has to resolve.

old jim

 

[MadderDoc]

Adding energy to gas usually raises its pressure...
THEN the time of heat production (purple in the NDF chart, first image in this post ) should correlate with the pressure rise around 3:30 AM, beginning of "without water injection" interval, not the pressure drop around 9 am at end of that interval ?

The RPV pressure rise in the early hours past midnight on March 13 correlates with the loss of water injection by HPCI. The pressure in the RPV then went up to be steady at the level where SRVs starts cycling, such as to release steam to the suppression pool, while consuming the water inventory of the RPV. That would seem to be the expected behaviour.

The RPV pressure drop around 9 am Tepco have thought might have been caused by the Automatic Decompression System's being (unintendedly) triggered. IOW, the abrupt RPV pressure drop at 9 am would then be explained by the ADS forcing the opening of several (6-8) SRVs, adding further to the loss of RPV water inventory at that time.

Timewise, the proposed Zr water reaction is put right up in the tail of these events; while the core was getting uncovered, its temperature would increase due to decay heat until the the temperature threshold to set the Zr-water reaction going was reached. Tepco think that happened in a major burst from just after 9 am, in very close timely connection to the RPV pressure drop, and that another portion of Zr went off again around 12:00 on the same day, each time adding heat and pressure to the system. The operators had recorders running during this period, and they did record three PCV/RPV pressure increases/spikes, at 9 am (major), at 10 am (relatively small), and at 12 am (minor). The recorded values are shown on page 47 in the report. As you note, the RPV and PCV pressures were coupled ever since whatever it was that happened inside the reactor at about 9 am that morning.

 

[MadderDoc]

i've only added two lines to your picture to help me visualize the time frame
wetwell vent(purple) and explosion(red)

Yeah, that's nice. That serves as orientation points in time on March 14. There were vents or such also earlier, on March 13, at about 10:00, 13:00, and 14:00. Steam fans from the stack from these vents can be seen in the hourly webcam images, and was captured also by a satelite photo shot at 9:50. If the suggested timing of the zirconium-water reaction in the core is correct, these vents would have drawn down the hydrogen inventory that had been produced by it. It would have reduced the amount of hydrogen available to the later explosions, to the extent the vents managed to get it out through the stack.

 

[jim hardy]

The RPV pressure drop around 9 am Tepco have thought might have been caused by the Automatic Decompression System's being (unintendedly) triggered. IOW, the abrupt RPV pressure drop at 9 am would then be explained by the ADS forcing the opening of several (6-8) SRVs, adding further to the loss of RPV water inventory at that time.

Thanks !
My simplistic thinking was depressurization was likely incore thimbles melting creating a vent path .

Your ADS seems a better fit with Occam.
old jim

 

[MadderDoc]

Your ADS seems a better fit with Occam.

It was Tepco's idea, and one they came up with it rather early. The implication of the ADS explanation is the negative, that the abrupt pressure drop at 9am on March 13 was _not_ caused by the RPV's failing in any major way. However, the recent investigations in the pedestal area could call that into question. At the least one is allowed to ask: if the RPV didn't fail in a major way at 9 am on March 13 -- such as to produce the mess that can be observed there now -- when did it?

 

[jim hardy]

At the least one is allowed to ask: if the RPV didn't fail in a major way at 9 am on March 13 -- such as to produce the mess that can be observed there now -- when did it?

Fair question.

Said mess, from Sotan's link a few pages back

I see lots of 'stuff' that appears to have run down from above. No clue whether it came through vessel bottom or down outside of vessel from above, running along underneath the insulation.
No clue what it is.
Looks a lot like sea salt , maybe some boric acid too, but that's just a visual interpretation of course prejudiced because i know they injected both.

To those of you who've been under a BWR
are these broken tubes of some sort ?

.
2X snip from Sotan's picture , http://photo.tepco.co.jp/library/170330_01/170330_07.jpg

 

[MadderDoc]

are these broken tubes of some sort ?

.
2X snip from Sotan's picture , http://photo.tepco.co.jp/library/170330_01/170330_07.jpg

We are in unit 2. The right arrow, that would be very likely a radiation artefact. Left arrow points, little doubt, to the end of a broken or cut tube.

Below is a blow up from an unmasked-enhanced image, in which the end of the same broken tube can be located close to bottom right of center. It is hanging down from above, bordering to a section of the overhanging structure (bottom left corner of image), inside which Tepco says several tubes to the control rod position and the local power range readouts, tubes that should be visible, are not.

full view of the enhanced image http://gyldengrisgaard.dk/fuku_docs/170330_04.jpg, original at Tepco

 

[MadderDoc]

I see lots of 'stuff' that appears to have run down from above. No clue whether it came through vessel bottom or down outside of vessel from above, running along underneath the insulation.
No clue what it is.
Looks a lot like sea salt , maybe some boric acid too, but that's just a visual interpretation of course prejudiced because i know they injected both.

I reckon one could look at it as a scene from the 'sewer' of unit 2. There has been coming water down and past here for a long time transporting stuff from above, and further on downwards. So, we are looking at something which has been changing over time, it was once spotless clean, then something happened and this drainage path was established, with many processes physical, chemical and who knows, biological, going on since then such as to produce the image that we can look at right now. It will continue to develop over time albeit surely slowly from now on. It is difficult to say, what composition is the deposits we see have built up on the hanging structures, or indeed the 'goo' on the remnants of the platform. I find it immediately interesting, that we don't see blobs of rusty aggregations of material on steel structures, which very much catch the eye in the videos from the corresponding area under the unit 3 RPV. Perhaps it lies in the difference, that the structures in the case of unit 3 have formed while being flooded in 'standing water', while those structures in unit 2 are being formed while continually being wetted in air, by streaming water from above.

 

[Hiddencamper]

How automatic depressurization system works:

Low level 1 (typically 1 foot above the fuel), low level 3 (2 feet below normal operating level as a confirmation signal this also triggers a scram), plus a high drywell signal (1.6-2.0 psig-ish), plus a detected high discharge pressure on an ECCS pump, plus a 105 second timer.

All signals were met except for the ECCS pump permissive. Follow up data reviews identified that wetwell pressure was so high that it raised ECCS pump suction pressure above the ADS set point, tricking the logic into thinking LPCI was operating and initiating an ADS blowdown.

The logic is 1/2 twice. Also some plants remove the high drywell pressure permissive, and other plants put an override timer in the event you have a sustained low water level for more than a few minutes with no high drywell pressure.

 

[MadderDoc]

How automatic depressurization system works

Thank you for explaining this, Hiddencamper. Do you know, once an ADS blow-down has been initiated, how or when is it triggered to end, meaning, is there some automatic to release the SRVs to come back closed again dependant on changing signals of water level/pressure? They would by design, I believe, come back closed passively, when/if power has run out to open/keep them actuated in the open position -- but besides that, assuming there is enough power, I wonder if there is some logic to actively trigger them to come back closed.

 

[Hiddencamper]

Thank you for explaining this, Hiddencamper. Do you know, once an ADS blow-down has been initiated, how or when is it triggered to end, meaning, is there some automatic to release the SRVs to come back closed again dependant on changing signals of water level/pressure? They would by design, I believe, come back closed passively, when/if power has run out to open/keep them actuated in the open position -- but besides that, assuming there is enough power, I wonder if there is some logic to actively trigger them to come back closed.

Once ADS initiates the safety function is to hold the valves open. If they went shut in the middle of the transient this can result in a loss of steam cooling to the core which is likely uncovered prior to core spray or LPCI cutting in. The ADS logic seals in once it activates and remains sealed in. It can be manually reset (which also resets the 105 second delay timer), and if the initiating signal doesn't clear you have to reset it every 105 seconds to keep the delay timer from activating the logic again.

Many plants have an ADS inhibit switch to block the logic. It's only used in an ATWS (scram failure) and many plants use it in Level control contingency 1 when they are planning on steam cooling the reactor or are trying to take advantage of any additional time below Level 1 to try and restore a high pressure injection system. The NRC doesn't like that though and a number of plants stopped inhibiting ADS outside of ATWS situations where water level is intentionally lowered to reduce natural circulation and power generation and a spurious blowdown can significiantlg challenge the safety of the core.

After a blowdown you want to keep the core depressurized. The steam gets dumped into the suppression pool which is likely to be at or over the HCTL (heat capacity temperature limit), and you may have a number of other "EMERGENCY DEPRESSURIZATION IS REQUIRED" actions in the EOPs keeping you there. At a minimum you want the minimum number of SRVs for decay heat removal open.

Some exceptions of course are during situations where you only have steam powered injection systems (RCIC/HPCI) and you need to prolong their operating time however you had a leak or containment challenge that requires depressurization. In this case you initiate ADS and lower pressure to the minimum acceptable RCIC/HPCI operating pressure then reset and inhibit the system using SRVs to maintain pressure in the RCIC/HPCI control band. Future revisions of the EOPs are also going to have you partially blowdown in scram failure ATWS situations where adequate core cooling can be maintained without a full depressurization, as we are learning that the reactor can exhibit chaotic behavior at low pressure / high power conditions.

 

[MadderDoc]

The ADS logic seals in once it activates and remains sealed in.

Thank you. That is interesting. So, if the ADS of unit 3 triggered in the morning of March 13th, opening 6-8 release valves to pass steam from the main steam line outlet of the RPV to the suppression pool, those release valves might have stayed open throughout the events that followed, and indeed ever since? (In that case no wonder the RPV and the PCV pressures henceforth appeared to be coupled.)

 

[Hiddencamper]

They would eventually fail closed if pneumatic air supply wasn't restored, or if drywell temperature caused failure. ADS for my unit using similar SRVs is only qualified to 340 degF. But for quite a while they would appear somewhat coupled until the eventual vessel breach.

 

[MadderDoc]

Now I wonder when Tepco think the vessel eventually was breached.

 

[Hiddencamper]

Now I wonder when Tepco think the vessel eventually was breached.

ADS consumes about 80-100 inches of vessel inventory or so when starting from high level. It likely completely uncovered the fuel. Time from fuel uncovery to vessel breach is likely a couple hours at that point. Very dependent on decay heat and injection.

 

[MadderDoc]

Tepco would think, it seems, that the vessel was breached already by about noon on the same day, not long after the temperature in the core had risen to set off the Zr-water reaction, such as to add even more heat. Past noon they started injection of sea water, it is not clear really how much, that went on until the morning on March 14, the next day, when the backwash pool ran out of seawater.

There was a hiatus of water injection then again, for several hours, until some time into the afternoon. In the meantime, there had been a hydrogen explosion in the building, apparently accompanied by a grand hiccup of steam from the PCV. The next several days, steam was seen coming out vigorously from the top of the building; there had apparently by then been achieved good contact between fuel and injected water..

Tepco writes somewhere, that hydrogen from a molten fuel-concrete interaction could possibly have contributed hydrogen to the explosions in unit 3 on March 14, and in unit 4 the next day, although Tepco also notes, that there may have been accumulated water in the basement of the PCV, already from a drywell spraying operation in the morning on March 13 ( which might have quenched the interaction). That is a bit confusing -- if Tepco thinks the vessel was breached by noon, injected sea water from that point in time on would also accumulate in the PCV basement.

 

[jim hardy]

Sorry - these detailed pictures i haven't yet learned which goes with which unit. So i'll make mistakes - and promptly admit them.

Tepco would think, it seems, that the vessel was breached already by about noon

Lest the phrase "vessel... breached" spark China Syndrome speculation,
"Breach" can be just incore instrument tubes failing up high in the core as it uncovers . That'd make many small leaks of whatever gas mixture is above the water level , presumably mostly steam and hydrogen.
That's benign compared to vessel melt through which if it happens at all would be much later.
In my plant we had fifty tubes of approximately 1/4 inch diameter for movable incores, the PWR equivalent of BWR TIP system.. I understand BWR's have a lot more incore instrumentation. old jim

 

[MadderDoc]

Yeah. Sometimes I wonder how they manage to make room for enough water in the vessel between those zillions of tubes of all kinds coming up :-) I guess what I am trying to figure out, is -- now that Tepco have seen the actual state of affairs in the area under the RPV vessel bottom -- when do Tepco think things came to end up to be like that? The report from Tepco with evaluations of the three units, which we've been looking into, cannot have been influenced by the result of the pedestal investigation, seeing that report was finished one month before the investigation was done.

 

[MadderDoc]

i haven't yet learned which goes with which unit.

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.

 

[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.