Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[MadderDoc]

<..> i think Tepco's scurrying about was from a genuine lack of knowledge compounded with shock and disbelief . Probably official pressure to quell panic, too.

I assume you mean this as two distinct propositions. a) Scurrying about from a genuine lack of knowledge compounded with shock and disbelief -- and b) scurrying about due to official pressure to quell panic. It is difficult for one man to claim to be doing both of those two at the same time. I am ready to give Tepco some slack on the first one up to some limit, limiting the claimable period of shock and disbelief, and of course some limit on how ignorant one can claim to be. I have seen no evidence of outside pressure on Tepco to quell panic. I don't think there was any.

 

[jim hardy]

Fair enough on both.

]

 

[jim hardy]

OP-ed on response over there , from "Bulletin of the Atomic Scientists"

http://www.google.com/url?sa=t&rct=...v0abTBkIKcsujSVPw&sig2=pvkC7nDOXSuetJc5xW-ehw

But the biggest problem with the government's
crisis management was probably
the amateurish level of its crisis
communications. To be sure, information
was, for the most part, insufficient,
and there was little time to assess its reliability
before dissemination. Still, the
government's crisis communication
efforts often were abysmal.
When, at a press conference held on
the second day of the crisis, NISA
Deputy Director Koichiro Nakamura
acknowledged the possibility of a
core meltdown, Chief Cabinet
Secretary Yukio Edano demanded
that reactor updates only be communicated
with approval from the Prime
Minister's Office. Nakamura was dismissed
from his post later that evening,
and his assessment of a potential meltdown
was rejected. The Prime
Minister's Office then functioned as a
micromanager, only further complicating
the process. Kan personally visited
the plant, circumventing the NISA director
and directly contacting lowerranking
NISA managers with questions
about minor technical details.
Moreover, Kan's often-abrasive comments
and questions could seem like
cross-examinations; they made many
officials and advisers shrink under his
direction. In a December 17, 2011,
interview with our commission, NSC
Chairman Madarame said the prime
minister became overly excited after a
March 14 hydrogen explosion at Unit 3
that led to the injury of some SDF soldiers
on-site. For a couple of days, Kan
and other officials were driven by a fear
that public disclosures of radiation
levels would cause widespread panic.
This gave the impression that the political
leadership had fallen into a sort of
"elite panic." 10

Fair enough.
If the Prime Minister comes on site and grills folks to get first-hand knowledge, well, he's cutting through the bureaucracy. Good for him.

While that's not political pressure,
when he fires his deputy director for publicly admitting "the possibility of a core meltdown,"
it would sure make people think twice about what they say.

 

[MadderDoc]

If the Prime Minister comes on site and grills folks to get first-hand knowledge, well, he's cutting through the bureaucracy. Good for him.

Yeah. I also can't see any fault with his doing that.

While that's not political pressure,
when he fires his deputy director for publicly admitting "the possibility of a core meltdown,"
it would sure make people think twice about what they say.

The said deputy director is still in his same position at NISA, so he was not fired. Initially during the Fukushima accident, Mr Nakamura appeared as spokesman on behalf of NISA at press conferences, but for the main part thereafter Mr. Nishiyama, another deputy director at NISA, was assigned with that duty.

NISA has several deputy directors. Somebody who thought there was only one deputy director of NISA, might on hearing that Mr. Nishiyama had replaced Mr Nakamura in press conferences have made the false inference that Mr Nakamura had been replaced in his position of Deputy Director.

Perhaps a bit strange that your source document did not check its own source for this particular piece of information. Anybody with political clout would know a Prime Minister would not fire a high ranking official in a governmental safety agency in the midst of its dealings with a high profiled accident unless there was an immediate serious criminal charge to be held against that official. PMs have a high aversion of political suicide or they wouldn't be PMs.

 

[MadderDoc]

Fair enough on both.

]

Alright. On the night between March 17th and March 18th, a Tepco official expressed some satisfaction that the spraying operations had been effective to cool the fuel rods in the spent fuel pool, because, he said, they were able to observe some steam.

One is compellingly led to assume that he is implying a causal relationship: Spraying hits hot fuel, causing evaporation of water, causing observable steam plume. In effect then he says the hot fuel had little contact with liquid water when the spraying operations was initiated, and did therefore not steam, while after the spraying, some steam was observed.

(And that, we understand, is the good news, some cooling of the fuel had been achieved. The bad news would be the implied message, that the fuel is currently in a state of near complete exposure. The total message including the bad news part would not seem well suited to quell panic.)

However, steam had in fact been observable continuously for days from the building. Succinctly, it steamed just fine before as well as after the helicopter and the water cannon sprayings. There was in fact no basis to conclude from observing steam after the spraying, that it effected cooling of overheated fuel rods.

Now, this Tepco official hardly can be taken to be ignorant about the fact that the unit steamed also before the mission. He also cannot be assumed to be in a state of shock and disbelief, such that he didn't quite know what he was saying. His message was also not suitable to quell panic, it was actually rather a frightening message (Headline e.g.: "Tepco struggling with fully exposed fuel") IOW, I am struggling to explain this using your theory.

What the Tepco official happened to produce was a statement which would be known to him and other well informed persons to be absolute hokum, otoh it had some built in plausible deniability, due to its vagueness. Strictly it was not a false statement: some steam was observable. To less informed persons already with concerns about the spent fuel pool it would be an alarming message of a very serious condition of the spent fuel. To the rest of people, probably most, it just produced a vague message of some mildly good news from the plant, for a change. Soothe the many into passivity, let a few ill-informed destroy their own credibility with scare stories, get on with whatever you now have sanctity to be doing, and if you are called on the facts, 'you didn't mean it that way' Looked upon as a piece of technology propaganda, this was technically a masterpiece. Why should I think this was coincidental?

 

[jim hardy]

To the rest of people, probably most, it just produced a vague message of some mildly good news from the plant, for a change. Soothe the many into passivity, let a few ill-informed destroy their own credibility with scare stories, get on with whatever you now have sanctity to be doing, and if you are called on the facts, 'you didn't mean it that way' Looked upon as a piece of technology propaganda, this was technically a masterpiece. Why should I think this was coincidental?

now THAT i do believe went on. For whatever motives.
It's even discussed in anthropology circles:

The Tokyo Electric Power [company] issued opaque statements, which described the ongoing events in extremely sparse, technical language totally de-contextualized from the everyday lives of the citizens whose lives have been placed at risk." Button's point here is that this manipulative approach to crisis communication is the norm, rather than exception, not only in Japan but in most other nations of the world. His primary message is that the chaos in the aftermath reflects very real uncertainties as well as opportunistically shaped and manipulated notions of "truth" that help further an array of political and economic agendas. Thus, we see in the first few weeks of the disaster ample evidence of efforts to shape and spin the public message in ways that limit liability and protect economic investments. This spin cycle evolved from silencing to a cacophony of largely critical yet often conflicting voices debating every aspect of the disaster and its potential consequences.

www.sfaa.net/newsletter/may11nl.pdf page 6. The Button article she references is interesting too.

So - people will be people... "Forgive them Father they know not what they do".

ZZ wrote:

Morbius chewed me over for thinking that it's even remotely possible for a debris bed to self-arrange into a favorable geometry.

It looks to me like there's a real good chance it goes through a favorable geomety period before it becomes a debris bed.

What's just underneath that deck where the steam came out ?

 

[MadderDoc]

On March 14th, there was a spectacular explosion in the unit 3 building, and naturally that would have left everyone who saw it suspecting that the RPV or the PCV could possibly have been damaged. Although steam started rising from the building after the explosion likely already by late afternoon on March 14th and it steamed throughout the next day, March 15th was a hectic day on the plant, Unit 4 blew up, Unit 2 started steaming, there were multiple fires. so in all that confusion Tepco never got to reporting that white smoke was coming from unit 3. Consequently, the official status of the PCV integrity remained "Not damaged".

On March 16th Tepco finally reported to the authorities, that white smoke was rising from Unit 3. The official status of the PCV was promptly changed to "Damage suspected" by noon on March 16th. There was an overhanging risk that media would start asking questions, radioactivity in increasing quantities was emitted from the plant. If the PCV of Unit 3 was in fact leaking steam directly to the atmosphere it would become the likely suspect, and it would attract attention in a way distinctly abhorred by Tepco. It was in this environment the bait and switch operation to draw attention away from the PCV was conducted. The explosion of Unit 4 had conveniently raised attention about the spent fuel pools, and the media were hungry after another bad thing to happen in the plant.

Now, having a boiling pool in Unit 3 was to Tepco by far preferable to having a leaking PCV. Steam plumes from a boiling pool would not in the same way as plumes from a leaking PCV be an interesting potential source of the observed high radioactive emissions. So Tepco decided that the steam plumes from unit 3 should be coming from the spent fuel pool, and not from the PCV. In that venture Tepco was hugely successful. Already by the evening on March 16th, Tepco had the attention of everybody focused to the dangerous development of the unit 3 spent fuel pool, and any growing interest of the PCV had been quenched.

During the morning of March 17th, the breaking news were of air force helicopter dropping water on the ever steaming reactor building, and during the afternoon the water cannon artillery took over the headlines. The plumes just kept rising from the building, as if it didn't care. With shaking voices the speakers commented on the battle. Would the heavily water-armed forces be able to pacify the pool? Yes! by midnight Tepco could report -- cautiously optimistic -- that the first day of spraying had been effective in cooling the fuel rods. Some steam had been seen.

The next day, on March 18th, the official status of the PCV was changed from 'Damage Suspected' to 'Might be ”Not damaged”' I am not sure much note was taken of this status change. The difference between 'damage suspected' and 'might be "not damaged"' is subtle indeed. Some would say there is no logical difference. The weight of the latter expression nonetheless seems to lean more towards "not damaged" than the former expression. 'Damage suspected' is such an awful thing to say about a PCV. Also a bit weird to keep saying that, seeing the pool of unit 3, as everyone knew by then, was the real problem.

The PCV status in Unit 3 was now kept in limbo at the 'Might be ”Not damaged” level until the end of the war. Smoke in all colors from white to black kept rising from the building seemingly unstoppable. At one stage a Tepco official explained that black smoke for unknown reasons was rising from the south-eastern corner of the building, the location of the SFP, while a picture quite surreal showed black smoke rising from the north-eastern corner of the building. But things do get confusing during a war.

Then on March 24th, when the final water spraying by fire truck was performed, the PCV status was changed from 'Might be ”Not damaged”' to 'Not damaged'. Satellite photos showed that the plumes of steam had all but stopped. Only a slight mist remained over the spent fuel pool. Not only had the war with the pool been won -- the PCV had miraculously become undamaged in the process. Tepco could celebrate, deservedly, all operations be they white or black had gone very well. Mission accomplished.

Still, by the end of March someone felt it imprudent to say with such seemingly absolute certainty that the PCV was undamaged. So, the status of the PCV was slightly adjusted, from 'Not damaged' to 'Not damaged (estimation)'. Probably that was just to remind everyone that in science there is no absolute truth.

Thus prepared no one could be surprised, when one month later, by the end of May the status of the PCV was changed again -- from 'Not damaged (estimation)', to 'Damage and Leakage Suspected'.

In the following months it dawned, that the war on the pool had been with an imagined enemy. The pool had in fact never boiled. The PCV had tricked us all into blaming those steam plumes on the spent fuel pool. Sneaky bastard.

 

[jim hardy]

I agree they have not shown their hand .

There is a lot riding on this "Nuclear Renaissance" .
There are forces that don't want public opinion against it.

You and I just want to know what happened. It's going to be hard to find out.

This Stolfi plot clearly shows the vessel bottom remained hot enough to steam those early days.
http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/plots/cur/out/ptmp-TCb-PCA-un3-full.png

Did they have a fire truckpumping water in? Presumably it came out as steam so with flow and pressure one could estimate size of opening and compare to say an ADS valve.. But the Stolfi plots don't have flow those first days.

I speculated at the time they were keeping temperature in the superheat region so steam leaving would be dry, it carries fewer radioactive "friends" if it has no water droplets.

Plant data was sparse and photos sparser.
That's why i am waiting on photos of head area, and that "Nova" show.

 

[zapperzero]

From a perspective of public relations, TEPCO did their utmost to avoid the appearance of the terms meltdown and melt-through for as long as possible, preferably until the crisis could be presented as largely contained.

They have succeeded in this, at the cost of using some tortuous language and a few lies of omission. Eh.

 

[MadderDoc]

<..>
There is a lot riding on this "Nuclear Renaissance" .
There are forces that don't want public opinion against it.

Yes peace be with them, and good luck.

You and I just want to know what happened. It's going to be hard to find out.

This Stolfi plot clearly shows the vessel bottom remained hot enough to steam those early days.
http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/plots/cur/out/ptmp-TCb-PCA-un3-full.png
Did they have a fire truckpumping water in? Presumably it came out as steam so with flow and pressure one could estimate size of opening and compare to say an ADS valve.. But the Stolfi plots don't have flow those first days.

I speculated at the time they were keeping temperature in the superheat region so steam leaving would be dry, it carries fewer radioactive "friends" if it has no water droplets.

Plant data was sparse and photos sparser.
That's why i am waiting on photos of head area, and that "Nova" show.

Although more data has emerged since Jorge's plots, what happened is not yet clear to me. The temperature sensors suffered collateral damage in the war with the pool, and the water injection records are a messy brew of untrustworthy measurements, best estimates and data from pump specifications.

According to Tepco's estimates, while the building top was being douched with fire trucks, they pumped water into the reactor at an impressive rate of about 50 m³/h. I can't understand that other than they were attempting to flood the PVC, and to some extent successfully, apparently enough to have the steam plumes quenched by March 24th, but according to core water level indicators, not enough to flood the core.

My best guess is that it then occurred to them, that there was leakage to a degree such that upholding the present water level in the PVC would necessitate continued massive injections that would just leak out and accumulate as radioactive water elsewhere. So they cut back the injection rate, PCV water level dropped back, and the reactor started steaming again after a few days, and kept steaming for months thereafter.

 

[MadderDoc]

So - people will be people... "Forgive them Father they know not what they do".

I don't quite know what to say to that, jim. I never really liked people, but I do sympathise with the pity expressed by that ancient quote. However this is the 21st century, people must acquiesce to what it takes to uphold the complex society they are fed by, and that includes their willingness to accept, indeed crave, that what they do is being controlled by controlling what they know. There is no other way, and that way is perhaps not even passable. Only time can tell if people can take it or they will rather blow the whole thing up in an explosion of irrationality. When I was young we read SF novels about it, but now we are in it. Welcome to Dystopia.

 

[zapperzero]

Well, that was unexpected. Anyway, from my trawling through NRC FOIA transcripts (some freedom of information, that, by the way, about half of the material is censored) the impression I get is that the NRC had no idea what was really going on - they were plugged into the Japanese PMs emergency center (from what I can gather, with very limited access) and they had no info first or second hand info, bar what various US technical assets, experts and simulations were telling them.

In the meantime the J-gov was asking them for advice - there's huge potential there for GIGO and for inattentional blindness.

It seems to me that the tactic everyone fixated onto, pretty early on, was "just keep pouring water on the damn things". This was done, enthusiastically even. So what if they were spraying the wrong corner of the building? Some of the water must surely have made it into the pool.

 

[jim hardy]

M'doc thank you for that thoughtful post. I will have to think on it for a while.

willingness to accept, indeed crave, that what they do is being controlled by controlling what they know.

i can't crave it and i don't really accept it either. But i do accept my powerlessness to do much about it. So i'll understand as much as my doddering brain can glean .
Did you guys read Golding's "Lord of the Flies" in high school? Remember Simon... truth might set one free or it might get one killed.

ZZ
As you and m'doc observe the early response was "more water". Until the sheer amount of it became problematic.

(some freedom of information, that, by the way, about half of the material is censored) the impression I get is that the NRC had no idea what was really going on - they were plugged into the Japanese PMs emergency center (from what I can gather, with very limited access) and they had no info first or second hand info, bar what various US technical assets, experts and simulations were telling them.

i agree, the unthinkable had happened and everybody was in uncharted territory.

I have to believe there was strong desire to not let potentially scary information out.
Did you notice the references in that FOI to the 'secure phone line with other information' ?
And that the expert emails went encrypted ?
And how little of the drone video footage was of unit 3? 30 seconds out of twenty minutes ?

Given the propensity in some circles to stir trouble i can sympathize with TPTB on that count at that time
but as i said earlier it's getting time for calm reflection over what went on.

impressive rate of about 50 m3/h. I can't understand that other than they were attempting to flood the PVC, and to some extent successfully, apparently enough to have the steam plumes quenched by March 24th, but according to core water level indicators, not enough to flood the core.

That would be a LOT of steam. Any idea how much heat it takes to make that all into steam and how it compares to decay heat ? I did that calc last year on another forum but don't remember result. Seems to me it was a good match, though. I did not calculate the area required to vent that much steam at reported pressure because at that time i thought RPV was wide open and the pressure readings were wrong . Might try it this evening.

Gotta tend to some chores now -

later,

old jim

 

[Bandit127]

I don't quite know what to say to that, jim. I never really liked people, but I do sympathise with the pity expressed by that ancient quote. However this is the 21st century, people must acquiesce to what it takes to uphold the complex society they are fed by, and that includes their willingness to accept, indeed crave, that what they do is being controlled by controlling what they know. There is no other way, and that way is perhaps not even passable. Only time can tell if people can take it or they will rather blow the whole thing up in an explosion of irrationality. When I was young we read SF novels about it, but now we are in it. Welcome to Dystopia.

Sorry, but you lost me completely there.

 

[MadderDoc]

<..>
I speculated at the time they were keeping temperature in the superheat region so steam leaving would be dry, it carries fewer radioactive "friends" if it has no water droplets.

I don't think there is evidence that they did such a thing intentionally, but the measured water injection rates were actually close to nil for several days, so it would seem to be a valid interpretation of data that the reactor boiled dry during this period. It would also seem to better explain the black smoke event which preceded the pause of steam evolution on March 24th. In this scenario steaming would have started again, when effective water injection was re-established.

 

[MadderDoc]

<..> So what if they were spraying the wrong corner of the building? Some of the water must surely have made it into the pool.

I am not sure what you are saying there zz. That it was -- worth it?

 

[MadderDoc]

<..>
That would be a LOT of steam. Any idea how much heat it takes to make that all into steam and how it compares to decay heat ?

Yeah. You'd need about 35 MW to boil away 50 cubic meters per hour. :-) That's why, if that injection rate was intended it couldn't have been just for cooling. As I said in another post the actually measured injection rates were very low, and insufficient for cooling. Only later Tepco argued that the measurements had been wrong, and replaced them with much higher estimated values. This happened in connection with Tepco's argumentation for why emission from unit 3 couldn't have cause the observed increase in dose rate in Ibaraki, and other places on around March 21.

 

[MadderDoc]

<..>
i can't crave it and i don't really accept it either.

:-) If you don't crave or accept the control and withholding of information, how would you suggest society should avoid those dreadful tabloid headlines you wouldn't like us to have until time had passed and everybody was ready for the NOVA show. Censorship? See. there is the problem, you can't have that. People want to live in a society with at least an illusion of freedom and democracy.

And how can a hi tech society make the right technological decisions for everybody? Dictatorship? Again, you can't have that. Seminars where everybody learned about all those complex choices and technology before deciding together carefully on the subject matter? That's no good either, eh? So how about carefully crafted and dosed information, benevolently making people feel like making the 'right decisions' 'all by themselves' or accept it be done by experts?

 

[zapperzero]

I am not sure what you are saying there zz. That it was -- worth it?

To deciders within TEPCO and the J-gov, at the time, viewed through the "fog of war" which they themselves had (ironically, at least partly, with help from their USian... friends? minders?) helped create, yes, I believe it must have seemed that way.

 

[zapperzero]

Yeah. You'd need about 35 MW to boil away 50 cubic meters per hour. :-) That's why, if that injection rate was intended it couldn't have been just for cooling. As I said in another post the actually measured injection rates were very low, and insufficient for cooling. Only later Tepco argued that the measurements had been wrong, and replaced them with much higher estimated values. This happened in connection with Tepco's argumentation for why emission from unit 3 couldn't have cause the observed increase in dose rate in Ibaraki, and other places on around March 21.

Wait, wait. now you're talking of them cooking the books. This is in a different league than omissions and deletions and selective disclosure.

 

[MadderDoc]

Wait, wait. now you're talking of them cooking the books. This is in a different league than omissions and deletions and selective disclosure.

No,no, and no. I don't know how you come to make that inference, lol. I have no idea whether this is a case of them cooking the books or not.

It is in the nature of corporate science, if it is to give you any information, you'll have to take the 'trust hat' on, so to speak, at the entry, that the data you are presented with is correct and the work has been done properly. Then, it becomes more a question of 'weighing' up the total evidence, what of it seems reasonable, how well-founded does it seem etcetera, and in the end make your own conclusions, which may or may not coincide with that of the author. The situation is different than what exists with normal science. One could say normal science is hard core science, whereas corporate science is softer, more malleable and fuzzy. That's not to say some or most of it is not top notch science.

I'd be interested in reading your evaluation of the documents we are looking at.

 

[MadderDoc]

From a perspective of public relations, TEPCO did their utmost to avoid the appearance of the terms meltdown and melt-through for as long as possible, preferably until the crisis could be presented as largely contained.

That may not be fair, consider what Tepco has to say about that particular criticism.

 

[zapperzero]

I'd be interested in reading your evaluation of the documents we are looking at.

login gremlin ate my post.

I will summarize.

In http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110909_04-e.pdf
I think we are seeing, on 3/21, the dropping of fuel from the RPV and the start of a core-concrete reaction (grey smoke confirmed, 3/21 15:55, spike in on- AND off-site radiation readings).

Naturally, afterwards (until 3/26 approximately) a lot of hot gas rushes past the RPV flange temp sensor and, although there isn't much water being pumped in, the RPV bottom doesn't get all that hot and in fact starts to cool off after a while, because there isn't much left in it to heat it up.

The stuff about dose rates in Ibaraki and Tokyo tracking precipitation levels is funny, because they actually don't.

 

[zapperzero]

That may not be fair, consider what Tepco has to say about that particular criticism.

However, there is no established definition for the term “core meltdown” (core melt) in respect of the specific status represented by such term, and each person understands this term differently. Therefore, TEPCO has used the terms “fuel damage” and “fuel breakage" to explain the status of the core,

Why not use the term "core melt accident" then? It has an official definition.
http://www.nrc.gov/reading-rm/basic-ref/glossary/core-melt-accident.html

The phrase "core melt" itself is also well used and understood in the technical community and is present in many NRC documents.

 

[MadderDoc]

In http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110909_04-e.pdf
I think we are seeing, on 3/21, the dropping of fuel from the RPV and the start of a core-concrete reaction (grey smoke confirmed, 3/21 15:55, spike in on- AND off-site radiation readings).

That would seem to me a reasonable interpretation. Further support for that interpretation (not included in Tepco's digram) is the data from the DW HVH return duct,
which we find at 126.3 deg C before the (uncommented!) 35 hour data hiatus and at 403.4 deg C after it.

Tepco's conclusion, otoh, that the temperature data shows that the reactor was being stably cooled is utterly unconvincing . Tepco's conclusion that one can read out from the similarly trending RPV and PCV pressure data that water injection could not have been largely reduced is a crude non sequitur.

It is not mentioned by Tepco that the system never again after this period showed any signs of being able to hold pressure.

It is also not mentioned that the period of interest is generally characterised by grossly unstable readings from the temperature sensors. Only the readings of two selected sensors have been included, and standing alone they do appear to be OK, however the existence of many other unstable sensors at the same time should raise suspicion that the readings of the selected sensors might too be inaccurate.

All in all I would evaluate this to be a particularly crude piece of corporate science. In a regulatory situation it would likely after reading, with a little smile, be landed in the document tray marked 'useless'.

The stuff about dose rates in Ibaraki and Tokyo tracking precipitation levels is funny, because they actually don't.

No, you are right. This is also not too convincing. Note though Tepco's remark that even when the diagram has 0 mm precipitation that does not mean it didn't rain just a little bit, lol.

 

[MadderDoc]

I hope you enjoyed the reading. As you can see the language use in relation to melting of fuel in the core of the Fukushima reactors has been the subject of considerable deliberation and controversy :-) The use of 'melt' was apparently rejected because 'melt' could mean different things to different people. So they thought fuel damage was better. Oh well.

Why not use the term "core melt accident" then? It has an official definition.
http://www.nrc.gov/reading-rm/basic-ref/glossary/core-melt-accident.html

Bravo! It doesn't really mean that much what one calls it as long as the term is well defined, not liable to be confused with other conditions, and consistently used. The first occurrence of Tepco's reporting of a core melt accident would then be in May 2011, in relation to the evaluation of the core status of Unit 1. Although the term 'core melt accident' itself was not used, there are words in the evaluation to determine that the situation in Unit 1 matched the definition.

The phrase "core melt" itself is also well used and understood in the technical community and is present in many NRC documents.

Inded when there is a definition of 'core melt accident' it would seem implied for reasons of language consistency, that 'core melt' is what has happened in a core melt accident.

 

[NUCENG]

I started the thread on TEPCO and Government Performance to talk about the poor communications and apparently incompetent company and regulatory environment that led to this accident (ignoring the real tsunami threat in the country that gave us the word "tsunami." The idea was to keep this thread focused on technical topics.

If I were a betting man, I'd predict lots of books and studies will try to figure out who knew, what they knew, when they knew, what they did with the knowledge (even if it was erroneous), and the big question "WHY". I really believe this is as important a topic as the search for causes and lessons learned. But can we please try to get back on topic here?

 

[MadderDoc]

Temperature sensors Unit3

>As regards the junction box which you pointed to in our discussion of the temperature readings of unit 3 during March 20+, I wonder if there is per design only one junction box for temperature sensors in a BWR? Some of the temperature sensors from which there are available readings _appear_ to have come through quite unscathed, while other sensors went totally bananas. (Edit: if it may be a clue, I am thinking particularly of the readings of the Safety relief valve Leakage points). Another question, would there be possible failure modes, with perhaps some unintended electrical interconnection within such a junction box, that could concertedly send the readings of some sensors downscale and others upscale?

Additional question, what voltage would correspond to readings at about minus 130 deg C give or take some. Conspicuously many of the obviously faulty readings are in that range.

 

[zapperzero]

Meta-talk

I think the discussion about terminology does belong in the political thread. I do NOT believe that the stuff about "what were they thinking" belongs in the management and government performance thread. What the crisis managers thought had real consequences on the engineering front and moreover interpreting the data is kinda what we do here.

I would also like to extend, again, an appeal to all of you to please use the Title: box.

 

[zapperzero]

Tepco's conclusion, otoh, that the temperature data shows that the reactor was being stably cooled is utterly unconvincing.

Quite.

Tepco's conclusion that one can read out from the similarly trending RPV and PCV pressure data that water injection could not have been largely reduced is a crude non sequitur.

I can't seem to recall exactly what line they were using to inject water at that time. Do you remember?

It is not mentioned by Tepco that the system never again after this period showed any signs of being able to hold pressure.

There is another picture worth painting. At this time, TEPCO performed another high-volume dousing of the pool, doubled the water injection pressure (and so, perhaps, the volume too), moved monitoring to the emergency center and instituted a partial evacuation of the site:
http://www.csmonitor.com/World/Asia...kers-evacuated-from-Japan-nuclear-plant-again
They sampled seawater and reported finding cesium and iodine.
Also on 21.03.2011, food distribution restrictions were put in effect in the Fukushima prefecture, in areas beyond the 20 km radius:
http://www.mx.emb-japan.go.jp/alimentosjp/1.2AlimenEdoAct120911.pdf

 

[MadderDoc]

I think the discussion about terminology does belong in the political thread. I do NOT believe that the stuff about "what were they thinking" belongs in the management and government performance thread. What the crisis managers thought had real consequences on the engineering front and moreover interpreting the data is kinda what we do here.

I would also like to extend, again, an appeal to all of you to please use the Title: box.

Just to add a snippet from an IAEA OSART mission to a Japanese NPP, indicating the technical aspects relating to the plant which were examined by the IAEA. Note item 4.

"MAIN CONCLUSIONS
The OSART team concluded that the managers and staff at [name omitted] NPP are
very enthusiastic in their commitment to improve the operational safety of the plant. The
team found good areas of performance, including the following:
- Open, professional and productive approach to the OSART mission and willingness to
learn and improve
- Excellent material condition and housekeeping of the plant
- Cooperation with contractors and long term partnership
- Respect for the public and region and comprehensive programme to improve public
confidence
- Training facilities including simulator exercise reviews
- Very good comprehensive emergency exercise with involvement of both on-site and off-
site organizations"

 

[MadderDoc]

Unit 3 water injection early days (was Re: Japan ..)

I can't seem to recall exactly what line they were using to inject water at that time. Do you remember?

That's a very good question. The line, the injection point, the feed source of water. I remember being frustrated by some lack of data last time I looked into it. I'd better check, rather than taking this from memory.

Edit: Hum. This is going to take some time, zz.

 

[zapperzero]

Edit: Hum. This is going to take some time, zz.

Sorry. I'd have checked myself otherwise. I am swamped with work.

 

[MadderDoc]

Sorry. I'd have checked myself otherwise. I am swamped with work.

No worries, I'm not hung up and actually enjoy digging into it.

 

[tsutsuji]

http://www.tepco.co.jp/cc/press/betu12_j/images/120512j0101.pdf Establishment of an Implementation Plan on Reliability Improvement Measures at Fukushima Daiichi Nuclear Power Station (275 pages, Japanese)

Just a glimpse:

page 89/275

page 90/275

 

[MadderDoc]

I can't seem to recall exactly what line they were using to inject water at that time. Do you remember?

Water injection to the Unit 3 RPV would have been to the Fire Extinguisher System Line (FESL). As regards _unit 3_ until March 28th pumping would still have been by fire trucks, configured similarly to the setup by the evening of March 14th. (Edit: until March 26th, when fire trucks started injecting fresh water) Here's a schematic of that configuration cropped from http://icanps.go.jp/eng/120224Siryo04Eng.pdf :

 

[tsutsuji]

http://www.tepco.co.jp/nu/fukushima-np/images/handouts_120516_07-j.pdf Soundness of unit 4 reactor building (Government-Tepco mid-long term meeting, May 2012) (22 pages, Japanese)

 

[jim hardy]

would there be possible failure modes, with perhaps some unintended electrical interconnection within such a junction box, that could concertedly send the readings of some sensors downscale and others upscale?

Yes, moisture can do that.
The thermocouple effect produces tens of microvolts per degree so you translate signals of a few DC millivolts into temperature.
Should the wires get wetted by water that's conductive it makes a battery via galvanic cell action - different metals in presence of an electrolyte.
One of the metals would be one of the theromocouple wires and the other metal might be the other thermocouple wire or it might be nearby metal like the inside of conduit or junction box.
Galvanic cells make tens if not hundreds of millivolts , hundreds of times more than the meager millivolts you get from thermocouple effect.
So the temperature signal gets drowned out. :(
and can give you either polarity depending on the chemistry at the wet spot.

So wet thermocouples are not reliable.

what voltage would correspond to readings at about minus 130 deg C give or take some. Conspicuously many of the obviously faulty readings are in that range.

negative four to six millivolts DC.
I don't reemember which type thermocouples those were, for some reason i thought iron-constantan. Tsutsuji posted it once and i remember thinking "I'll never forget that" but i have.

Anyhow Omega teaches most engineers about thermocouples via their excellent books.

Here's their thermocouple intro page
http://www.omega.com/techref/thermcolorcodes.html

and millivolt vs temperature tables are accessible here
http://www.omega.com/thermocouples.html

clicking iron constantan opens a pdf table
type J(iron-constantan) is -5.8++ millivolts at -130 degreesC
similarly type T (copper constantan) is -4.2++.

as you see it's low millivolts irrespective of thermocouple type.

The TEPCO technicians went to great lengths to correct readings for damaged leadwires
but only they know how much faith to put in their results.
I had some luck with damaged thermocouples that were wetted right at their sensing end
but never with ones wetted midway.
Probably those guys were better than me. Certainly i never worked under the pressure they did..

hope this helps.

old jim

PS possible reason for lots of ~-130 degrees readings

it is common practice to interpose a device called transducer that translates a peculiar signal into a standard range. That allows use of a cheaper computer front-end(ADC) and kmakes things easier for the programmers.
A common range has max to min ratio of five, like is 1 to 5 volts or 4 to 20 milliamps or 10 to 50 .
So a bunch of thermocouples might be handed to the plant computer with 1 to 5 volts representing zero to 500 degrees ( just random pick, i have no idea how GE computer is scaled) .
When power is lost to the transducers they all go to zero volts which (with linear conversion) would represent -125 degrees . Computer probably adjusts for non-linearity of thermocouple so -130 degrees is a quite possible reading for thermocouples with expected range of ~500 degrees that are reporting maximum downscale temperature.
The five to one turndown is intentional so that a failed transducer or one that's lost power drives the indication 25% below bottom of scale.
You wouldn't want a loss of power to your instruments to put all your meters midscale - you'd want them downscale so it's obvious what happened. That's why zero center meters are rare in control boards.

Sorry for digression. But it's important to know what an instrument is really saying . They seldom lie we just misunderstand them.

 

[MadderDoc]

<..>Sorry for digression. But it's important to know what an instrument is really saying . They seldom lie we just misunderstand them.

Thank you jim, that was very helpful, and not least the last bit, which rings true, looking at data. In unit 3 it appears to be the case, that somewhere around March 20th something started interfering with readings, and under circumstances such that wetting of leads or junction seems likely.. This resulted in a period in gross instability of readings, and indeed readings which would seem physically impossible under the circumstances After that, there was a period of apparent gradual revival of sensors, i.e. readings wandered within the range of the possible to stay there albeit still with huge variations up and down.

From what you have told me this would seem to me to be true statements:

a) we have reason to believe the readings until the period of interference were still reasonably well calibrated.
b) during the period of interference, we can have no confidence that readings are accurate
c) during the period of gradual revival, we can have no confidence that readings are accurate
d) during the period after revival, we can have no confidence that readings are accurate
e) during the period of gradual revival we can have no confidence that the trends up or down in readings reflect reality
f) during the period after revival, we can have some confidence that trends up or down in readings reflect reality.
g) there would have been no way of recalibrating the sensors during the accident.
h) there would be no way -- later -- to assess the magnitude and direction of inaccuracy of the readings recorded during the accident.
i) the magnitude of inaccuracy we would be looking at might be in the XXXXXL league.

 

[zapperzero]

Water injection to the Unit 3 RPV would have been to the Fire Extinguisher System Line (FESL).

Thank you!

 

[MadderDoc]

<..>
PS possible reason for lots of ~-130 degrees readings

it is common practice to interpose a device called transducer that translates a peculiar signal into a standard range. That allows use of a cheaper computer front-end(ADC) and kmakes things easier for the programmers.
A common range has max to min ratio of five, like is 1 to 5 volts or 4 to 20 milliamps or 10 to 50 .
So a bunch of thermocouples might be handed to the plant computer with 1 to 5 volts representing zero to 500 degrees ( just random pick, i have no idea how GE computer is scaled) .
When power is lost to the transducers they all go to zero volts which (with linear conversion) would represent -125 degrees . Computer probably adjusts for non-linearity of thermocouple so -130 degrees is a quite possible reading for thermocouples with expected range of ~500 degrees that are reporting maximum downscale temperature.
The five to one turndown is intentional so that a failed transducer or one that's lost power drives the indication 25% below bottom of scale.
You wouldn't want a loss of power to your instruments to put all your meters midscale - you'd want them downscale so it's obvious what happened. That's why zero center meters are rare in control boards. <..>

My understanding is that under normal operation they would have the signal leads from the temperature sensors connected to a set of multi-channel recorders. The output would come on paper, in the form of differently colored pen traces. The paper would be scaled, for each group of sensors with a convenient scale for that group of sensors, say 0-500^oC.
The recorder would be equipped to do the necessary signal conversion, perhaps including transduction, offset calibration, linearity correction. you can probably think of more.

The data set I am looking at though, is from after all that functionality was lost after the tsunami on March 14th, with the power to the recorders, and these data represent the first temperature measurements emerging from Unit 3 after all the explosions at the plant. The earliest data are from March 19th. The output appears as discrete measurements, and indicate much more of a human hand was involved in the production of it. From looking at the data set I get an impression of men with notebooks at irregular intervals reading sets of signals, with those signals then on the spot or with some delay converted by some method to a temperature value. There is a 36 hour gap in data from about noon on March 21st, as if the men with notebooks during that period were otherwise engaged, or were not able to be at the spot where the signals could be read. I would think the signals would have been most likely read from the disconnected leads from the sensors, at the recorders in the Unit3+4 Main control room.

I am trying to imagine what the conversion from signal to final output in this scenario would involve, and would appreciate your thoughts on it.

 

[jim hardy]

There is a 36 hour gap in data from about noon on March 21st, as if the men with notebooks during that period were otherwise engaged, or were not able to be at the spot where the signals could be read. I would think the signals would have been most likely read from the disconnected leads from the sensors, at the recorders in the Unit3+4 Main control room.

I am trying to imagine what the conversion from signal to final output in this scenario would involve, and would appreciate your thoughts on it.

does that gap align with the temporary evacuation?

If the wires they accessed are thermocouple wire they can be read directly with a hand held multimeter. Better ones will accept thermocouple wire and do the conversion to temperature for you.

If there is an interposing transducer they would have had to power it up (probably with car batteries?) and read its output with a DMM and convert to temperature. That's an easy sliderule , well nowadays pocket calculator, operation. But in early days working in respirators and maybe double gloves with flashlights - it's unimaginable.

I am tying to remember the details of those drawing Tsutsuji posted, specifically whether there was a remote "reference junction" where the wires transition from TC to copper. If so that's one more calculation but instrument technicians are well versed in it. Will go back and look for Tsutsuji's remarkable finds on that subject.

So the readings are not difficult to get, in concept.
Fortunately thermocouples are extremely rugged devices. Wet insulation is their achilles heel.

Electronic transducers are good until they've gotten probably a few tens of thousands of rads (hundreds of sieverts) . If there are any they must be outside the worst radiation areas.

old jim

 

[MadderDoc]

does that gap align with the temporary evacuation?

I wouldn't say align, but the gap does include an event with black smoke coming out of the reactor during the afternoon/evening of March 21st, when most employees were temporarily evacuated to a safe place, leaving only a minimal crew at the site. However the gap continues for most of the next day, until late evening on March 22nd.

I am tying to remember the details of those drawing Tsutsuji posted, specifically whether there was a remote "reference junction" where the wires transition from TC to copper. If so that's one more calculation but instrument technicians are well versed in it. Will go back and look for Tsutsuji's remarkable finds on that subject.

I think this is the post you are looking for:
https://www.physicsforums.com/showpost.php?p=3765763&postcount=12381

 

[MadderDoc]

Unit 3 steam outlets and hotspots

The thermographic image below was taken by SDF in the morning of March 20th 2011 during the SFP3 brouhaha. It is likely still after all those months the best evidence available to us, to show the location of steam outlets and hotspots of the top of the building of Unit 3. It was with evidence like this in hand Tepco maintained before the public their estimate that the steam plumes coming from the building was all coming from the pool, and not from the reactor.

I have outlined the approximate extent of the spent fuel pool to the left in the image. The measured apparent temperature of the pool was 62^oC (144^oF) at the time, according to the source.

The white arrows point to the two main steam outlets from around the reactor area, one outlet is close to the gate to the spent fuel pool, and another source at the opposite side of the reactor area, at the gate to the equipment pool. This latter source had an apparent temperature of 128^oC (262^oF). These two steam outlets from the reactors were in fact in the main responsible for the observed twin steam plumes from the building at the time. However the image shows also other interesting steam outlets and hotspots outside the area of the spent fuel pool, some of which probably contributed to the plumes.

Source: The Evaluation Status of Reactor Core Damage at Fukushima Daiichi Nuclear Power Station Units 1 to 3

 

[jim hardy]

I think this is the post you are looking for:
https://www.physicsforums.com/showpos...ostcount=12381

That's it ! THANK YOU

Signal arrives on Copper-Constantan.. type T. I have bookmarked the link.

they can read directly in degrees with a good DMM.

Here's the T millivolt table. http://www.omega.com/temperature/Z/pdf/z207.pdf

If you only have an ordinary DMM that doesn't handle thermocouples,
then you must compensate for "cold junction" and convert from millivolts to temperature:
Measure the incomiing millivolts,
look up millivolts for temperature of your connection point to the TC wire(room temperature),
add that to measured millivolts,
find in table temperature corresponding to that sum.
Sounds harder than it is, it quickly becomes second nature.

Thanks again

old jim (absent minded)

 

[MadderDoc]

<..>
If you only have an ordinary DMM that doesn't handle thermocouples,
then you must compensate for "cold junction" <..>
Sounds harder than it is, it quickly becomes second nature.

compensate for "cold junction" .. because the mere connection of the DMM to the sensor leads creates two additional metal-metal junctions? (say, Cu/Ni and constantan/Ni, if the grips of my DMM are Ni-plated)

 

[jim hardy]

compensate for "cold junction" .. because the mere connection of the DMM to the sensor leads creates two additional metal-metal junctions? (say, Cu/Ni and constantan/Ni, if the grips of my DMM are Ni-plated)

Yes, that's right.

When you get right down to it a thermocouple is a differential device.
It reports the difference between its hot and cold ends.

It is natural to assume the EMF is developed at the hot tip but that's not so.
The EMF is developed along the wire in regions where there's a temperature gradient.

Here's my oversimplification of it:
Because the different metals have different 'affinity' for electrons, a temperature gradient shakes charge toward the cold ends of the two wires with different EMF's. So equal ΔT produces unequal ΔV in the two wires. You read that difference.

If you place a thermocouple on the bench and connect a meter you get no millivolts.
When you change the temperature of either end a voltage appears.

Here's Omega's introduction:
the text around figure 4 describes what you said.

http://www.omega.com/temperature/z/pdf/z021-032.pdf

again sorry for the digression.

 

[MadderDoc]

<..>
Here's Omega's introduction:
the text around figure 4 describes what you said.

http://www.omega.com/temperature/z/pdf/z021-032.pdf

again sorry for the digression.

Nah, it is great! (I'll head straight for my messy-box, should I have a piece of constantan wire somewhere I can play with, heh :-)

 

[jim hardy]

Page 93 of those DAEC drawings has a sketch, albeit not detailed, of that deck.

The passage way to dryer pool is as you'd expect wider than the one to SFP.

I couldn't make a lot out of trying to overlay them mentally.

I am curious how main steam piping is routed out of vessel and where are safety valves relative to your steam plumes.. for they don't quite line up with those passageways to pools.
The DAEC drawing pages 4 and 5 is so crowded it's hard to read.

 

[tsutsuji]

http://www.tepco.co.jp/nu/fukushima-np/images/handouts_120516_07-j.pdf Soundness of unit 4 reactor building (Government-Tepco mid-long term meeting, May 2012) (22 pages, Japanese)

An English pdf is provided on the same date on the same topic, but the contents, although overlapping for some part, are not the same:

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120516_05-e.pdf Soundness Verification of Unit 4 Reactor Building at Fukushima Daiichi Nuclear Power Station (9 pages only)

http://www.tepco.co.jp/nu/fukushima-np/images/handouts_120516_07-j.pdf page 19/22 links to http://www.nisa.meti.go.jp/shingikai/800/25/003/3-3-4.pdf dated 28 October 2011, which is a presentation about the JNES studies completed in May and in July to cross-check the Tepco studies on the earthquake resistance of units 3 and 4.

Edit: The English pdf mentioned above is a translation of yet another Japanese pdf, that one : http://www.tepco.co.jp/nu/fukushima-np/images/handouts_120516_06-j.pdf (9 pages)