Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[zapperzero]

According to the WHO, the measured dose rate from the helicopters involved in the water dump operations was t(300m), and 87.7 milli Sv/h at 300ft (90m). As regards what could be seen from helicopters, we can get some indication from the published video sequences that were shot on March 16th. They appear to show a water surface in the pool, and steam plumes originating from areas close to the pool gates on either side of the reactor well. That was probably also what a human observer would have seen from the helicopter, only more clearly

I took the 7.5 Sv/h figure from a NRC transcript. I posted the transcript here earlier.

EDIT: The WHO numbers are for the water spraying mission on the 17th.
www.u-tokyo-rad.jp/data/whositrep.pdf

 

[MadderDoc]

I took the 7.5 Sv/h figure from a NRC transcript. I posted the transcript here earlier.

The transcript has the figure as 375 R/h actually. Quaint unit that, Roentgen per hour. Still, (assuming this is gamma) 3.75 Sv/h is a very high dose rate. which could call for a reality check.

At the time Tepco disagreed with NISA over which unit was mainly responsible for the emissions showing up as high dose rates up to 10 mSv/h at the site boundary. NISA thought it was coming from Unit 2, while Tepco thought unit 3 was the culprit. Taken at face value, the 3.75 Sv/h figure could indicate Tepco was right. The steam emission did also visually appear to be more violent from unit3.
http://192.168.168.11/fuk/20110316_0935%20satellite/20110316_0935_Digitalglobe_zoom_thumb.jpg

EDIT: The WHO numbers are for the water spraying mission on the 17th.
www.u-tokyo-rad.jp/data/whositrep.pdf

Yes, that's right. Unit 3 did not steam quite as much that day.

 

[zapperzero]

The transcript has the figure as 375 R/h actually. Quaint unit that, Roentgen per hour. Still, (assuming this is gamma) 3.75 Sv/h is a very high dose rate. which could call for a reality check.

My bad. My treacherous memory doubled it and I don't know why :P.

 

[MadderDoc]

My bad. My treacherous memory doubled it and I don't know why :P.

Oh well, 3.75 or 7.5 Sv/h, still we are in the same heavy weight league.

On the assumption that Tepco thought this was shine from exposed fuel in a drying out pool, they would necessarily also have thought that any steam from the pool would be emanating from the depth of it. In fact Tepco did state on the afternoon of March 16th, that they had found that all that steam from the building was coming from the pool, and not from the reactor.

Let's assume this was Tepco's honest appraisal of the situation, not a lie. So, what could have made Tepco come to that conclusion -- except their helicopter observations on that day, their videos of the scene. So, here is a sample crop from one of these videos, I do hope everybody can see the steam column gushing out from the depth of the water-drained pool.

"He set to work to exercise himself in crimestop. He presented himself with propositions -- 'the Party says the Earth is flat', 'the party says that ice is heavier than water' -- and trained himself in not seeing or not understanding the arguments that contradicted them. It was not easy. It needed great powers of reasoning and improvisation. The arithmetical problems raised, for instance, by such a statement as 'two and two make five' were beyond his intellectual grasp. It needed also a sort of athleticism of mind, an ability at one moment to make the most delicate use of logic and at the next to be unconscious of the crudest logical errors. Stupidity was as necessary as intelligence, and as difficult to attain." (George Orwell)

 

[SteveElbows]

Well let's face it, we know that the pools received too much attention in one way or another, for several different reasons, including the NRC guy in Japan taking time to believe it was possible for the 4 pool to exist with the outer building in the state it was. We can suggest that TEPCO might also have been keen to distract from issues of containment leakage at reactors other than 2, where the (incorrectly) presumed s/c explosion and radiation levels on that day forced them to say something. But as I recall they clung for a while to the story that containment was still intact at the other reactors. Some part of this was kind of fair enough in vague unscientific message terms since it was reasonable to get across a message that containment at the reactors was not utterly destroyed by explosions, since this had been a previous fear. But obviously they took it further than that, and even to this day we see news of containment damage released in understated fashion, and not focussed on very much in many of the lengthy official reports. They talk more of how to repair it than of the few areas of known damage we have now seen. I have to say it was surreal at times to see helicopter images showing steam escaping from some interesting places, and to have virtually no official or media commentary on what we were seeing.

Another reason for doing something at the pools is that there weren't very many other visible things to do at that point, and given the cascading nature of events at the plant I do not blame them too much for being pro-active on these fronts. It would not surprise me if US & PR factors influenced the decision, but that's not likely the whole story. Part of it might be to do with a broader shock & realisation amongst a range of experts, politicians, managers of one sort or another, as to the potential for spent fuel pools to cause big problems in a situation like this. Woken noisily to these problems by the reactor 4 explosion , and faced with reactors that have already melted, paying more attention than was strictly necessary to the pools seems understandable.

Also I do not know if the amount of debris in reactor 3 pool would have caused some additional concern about certain possibilities despite the observation of water.

 

[MadderDoc]

<.>
I know that many months ago some attention was paid to why video of one of the firefighter missions showed someone spraying the wrong side of the building.

Actually, Steve, there is no evidence that the fire-fighters sprayed to the side of the building where the pool is, on any of their missions. It may seem strange to us, however the fire-fighters would have thought their target was somewhere there in the middle, where the steam was coming from.

I don't have a wonderful explanation for this, although I wouldn't read too much into it, especially as the ground between units 3 & 4 was not very hospitable at the time.

Yeah. Like when you drop a penny in a dark lane, then head for the nearest street light to look for it. "Because the light conditions are so much better there."

 

[SpunkyMonkey]

Actually, Steve, there is no evidence that the fire-fighters sprayed to the side of the building where the pool is, on any of their missions. It may seem strange to us, however the fire-fighters would have thought their target was somewhere there in the middle, where the steam was coming from.

Exactly, here the firemen were, reportedly watering the fuel pool.

They seemed to think it was around the NW corner or near the middle of the floor. Why were they so poorly informed? So there those fearless men were risking their health/lives to merely water debris.

Lot's o great analyses going on here, esp re the valve. Am I correct in my impression that it seems the valve was of a type that should have allowed the RPV to re-pressurize if there wasn't a hole in it already? If so, this would seem consistent with the massive RPV pressure collapse on Mar 13 as marking time of melt-through, and exactly fitting the model of Ott et al.

 

[jim hardy]

Hmmm it's interesting to look at Doc's valve drawing
https://www.physicsforums.com/attachment.php?attachmentid=46822&d=1335800918
and ask what would that device do under reverse pressure difference, as if RPV found a path to atmosphere but torus remained pressurized?

Not suggesting that happened, just want to understand what the valve would do.

Looks like with pilot in right position which is command to open , 'outlet' pressure would come up through "main valve piston vent" in lower right and pressurize top of piston driving valve smartly shut.
With pilot in left position, both sides of piston see 'inlet' pressure,
so if ( 'outlet' pressure X seat area product) exceeded 'inlet' pressure by enough to overcome spring plus weight of parts the valve would conduct fluid.

So reversing differential across valve appears to reverse its logic. It'll close when commanded open and vice versa.

Now under stress THAT would be one confusing symptom !

I might try the arithmetic early in the day but not at this hour. Please excuse the old guy, i run out of mental steam anymore.. If my logic is faulty please call me out...

old jim

 

[elektrownik]

Bad source of information but data looks legit. What could be the source of I131 ?
http://fukushima-diary.com/2012/05/iodine-131-measured-in-kawasaki-yokohama-chiba-and-gunma/
http://fukushima-diary.com/2012/05/iodine-131-measured-in-yamanashi/
http://fukushima-diary.com/2012/05/iodine-131-measured-in-tokyo/

 

[zapperzero]

if RPV found a path to atmosphere but torus remained pressurized?

Certainly an intriguing idea. It would make for a nice explanation if the hardened vent rupture disk was found to be intact, eventually.

 

[Sorai]

Bad source of information but data looks legit. What could be the source of I131 ?
http://fukushima-diary.com/2012/05/iodine-131-measured-in-kawasaki-yokohama-chiba-and-gunma/
http://fukushima-diary.com/2012/05/iodine-131-measured-in-yamanashi/
http://fukushima-diary.com/2012/05/iodine-131-measured-in-tokyo/

Probably medical waste. Iodine-131 is detected regularly in sewage sludge. Here is a paper with the concentrations detected in Tokyo between 1983 and 1994:

https://www.jstage.jst.go.jp/article/jhps1966/33/2/33_2_163/_pdf

The main text is in Japanese, but the abstract and a table with the values detected are in English. Some of the references seem to include studies conducted in other cities.

 

[MadderDoc]

Exactly, here the firemen were, reportedly watering the fuel pool.

They seemed to think it was around the NW corner or near the middle of the floor. Why were they so poorly informed? So there those fearless men were risking their health/lives to merely water debris.

The video you link to would be from the daytime of March 18th, the last day of the attempts to reach the steam plume with water cannons trucks, in turns, from a position in the crossroad NW of the NW corner of the building. It would have been clear to everybody involved that the ~+100 meter distance up to the plumes meant that little water could hit the target.

During the night between March 18th and 19th, the Tokyo Fire Department Hyper Rescue Unit took over, they laid out a hose from the shallow quay at the ocean NE of unit 1 all the way up to the NW corner of unit 3, where they stationed a fire truck with a high extension spray tower. From that position and with that equipment they would have been able to hit the position of the billowing steam more efficiently -- and with the hose laid out they could pump to the top of the building continuously, rather than in the refill cycles of the water cannon trucks.

I am not sure how I would go on about informing the fire department -- called in an emergency to stop a spent fuel pool from boiling dry -- that they should direct their attention to a part of the building which was not steaming.

Edit: Some of the fire-fighters participated in a press-conference after the mission. If I get it right, this firefighter had been asked the question, what was the worst thing about the mission. I think he starts out something like 'My comrades, they.. ' then, well, it speaks for it self.

Lot's o great analyses going on here, esp re the valve. Am I correct in my impression that it seems the valve was of a type that should have allowed the RPV to re-pressurize if there wasn't a hole in it already? If so, this would seem consistent with the massive RPV pressure collapse on Mar 13 as marking time of melt-through, and exactly fitting the model of Ott et al.

Well, not quite, but it was a question posed by that model, that made it seem imperative to know the function of the safety relief valve better. This valve is first of all, a safety valve, it will relieve pressure automatically such as to keep the vessel at a safe level in a pressure band at about 7-8 MPa overpressure relative to the pressure sink, the suppression chamber.

However, the same valve can also be used as a relief valve, to depressurise the vessel intentionally. In that mode, using power and compressed air, the valve is kept internally reconfigured such as to keep the vessel within a pressure band at about 0.35 MPa relative to the suppression chamber.

Ott et al. is about melt down, with following RPV damage, and thus, in principle, the unconditional depressuring of the vessel to become equal with the PCV.

Depressuring by way of relief mode, otoh, would firstly, hinge on the continuous activation of the valve to be in relief mode. (If you loose power, or you have insufficient air pressure, the valve falls back to safety mode.) And secondly, depressuring to become equal with the PCV/suppression chamber would not be the expected behaviour in relief mode, since pressure can be relieved through the valve only above a certain minimum level of overpressure.

I am sure you can see the utility of all this, to make distinctions and judgements of the status of the RVP during events. I am not sure, though, that the toolkit is sharp enough to decide whether RPV damage caused depressuring, or it was the other way around. It might have been the depressuring by relief valve that lost them the last bit of the water inventory remaining in the RPV, thus allowing melted fuel to damage the RPV.

 

[Rive]

I am not sure how I would go on about informing the fire department -- called in an emergency to stop a spent fuel pool from boiling dry -- that they should direct their attention to a part of the building which was not steaming.

By giving them the necessary data?

Sorry, I see no problem here. If there is no immediate danger then every emergency team would ask for maps, floorplans and targets first before moving even a finger.

If they have aimed the plumes then they did it for a reason.

Of course it's possible that the reason was some stupid people who had given them false data, but that's not the point of my post. Firemen are not stupid (the stupid ones dies).

 

[MadderDoc]

If they have aimed the plumes then they did it for a reason.

Yes, possibly. According to officialdom nothing really was achieved, nor could have been achieved, except for more human radiation exposure. In my book this would put the acts of the firefighters in the helpless category, and that of their superiors in the bandit-like. I must apologize if I have come over by my expression, as implying that either of them were stupid, or acting stupidly, I didn't mean to.

 

[SteveElbows]

Exactly, here the firemen were, reportedly watering the fuel pool.

They seemed to think it was around the NW corner or near the middle of the floor. Why were they so poorly informed? So there those fearless men were risking their health/lives to merely water debris.

Actually that's the one example of footage where it always looked to me like they were trying to spray the right part of the building (but mostly falling short).

I haven't seen the fireman footage of spraying the NE part of the building for ages, anyone got a link to that?

 

[MadderDoc]

Actually that's the one example of footage where it always looked to me like they were trying to spray the right part of the building (but mostly falling short).

I haven't seen the fireman footage of spraying the NE part of the building for ages, anyone got a link to that?

I know only of a short sequence from past noon on March 19th which I have previously interpreted as the fire engine's spraying to the NE corner, but on later reconsideration I've come to think I was fooled by the perspective, and that the direction of that spraying too was to about center of the building. The short sequence is at the very end of the video here.

The initial water cannon truck attempts 17-18 March were made from about position A, then from the night 18-19 March and on, the spraying was done from a stationed fire engine at position B, the thin red line indicates the route of the hose that was laid by the fire fighters to feed the fire engine. The spent fuel pool is marked at position C. The photo is from about noon on March 19th.

 

[MadderDoc]

Funny how something can elude you completely then suddenly flip to become obvious. I'd figured vaguely last time I saw the firefighter video, this could be a doorway of unit 3 with something written on it, but of course it is not. The correct interpretation also explains why swift walking is subsequently heard.

 

[SpunkyMonkey]

Here are some thoughts on the Unit 3 1st floor PVC shield plug being moved from Genn Saji, former Secretariat of Nuclear Safety Commission, Japan:

II. First photo inside of an equipment hatch of 1F3 PCV

In order to check the situation of water leakage from the equipment hatch of PCV at the northeast on the first floor, an image scope inspection at the floor of the equipment hatch was performed on April 19. A gap opening between the shield plug and the reactor building has been confirmed in the past video. This motivated TEPCO towards inspection of the situation of water leakage from the flange of the equipment hatch, by inserting an image scope into the gap opening between the shield plug and the reactor building. A short summary was released by: http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120419_03-e.pdf

Since the leak tightness of the PCV is tested each time before reactor startup, the existence of the gap-opening should indicate an overpressure event inside of the PCV beyond the design pressure. As a matter of fact, there are at least four peak pressure recorded above 0.4 MPa inside of the dry-well between March 12 to 15, ranging from 0,4 to 0.65 MPa (design pressure is 3.92 kg/cm2). However, it is strange that the PCV did not have a safety margin of withstanding to this level of over pressure. In some model PCV test, a safety margin as high as a factor of 3 was shown, if I remember correctly in a PWR containment vessel model test. There is a high possibility that the over-pressure event is related with the "spontaneous venting." Since the pressure surges events were showing peaks, I suspect an occurrence of a series of hydrogen ignition (slow burning) events. Let me attach a previous TEPCO's graph (DoseRate-PressD-W1.jpg), showing variation of the dry well pressure and dose rates measure by radiation monitoring cars and a survey meter.

 

[SpunkyMonkey]

Actually that's the one example of footage where it always looked to me like they were trying to spray the right part of the building (but mostly falling short).

Possibly the high-dose rate on the south side (imo prob caused by the stack-vent bursting on the south side and releasing lots of cesium-vapor residue) which should have been detectable by the first Geiger counter in the scene made them opt to try to reach the pool from the NW corner.

 

[SpunkyMonkey]

I am not sure how I would go on about informing the fire department -- called in an emergency to stop a spent fuel pool from boiling dry -- that they should direct their attention to a part of the building which was not steaming.

At the time, it may not have been clear from the helicopter footage that the pool wasn't largely empty. It's only with the data gained over the following weeks that we could thereafter determine that there were roof girders / materials in the pool that were obscured by water on the 16th. But on the 16th they didn't have that information about debris in the pool.

Although U3 pool didn't seem to be steaming at that time, whereas U4 pool was steaming vigorously. Perhaps that invoked fear that U3 pool was a deep dark hole with no water left to boil.

Thanks for the overview of the valve analysis!

 

[MadderDoc]

At the time, it may not have been clear <..>

That is simply not credible. Tepco shot more video footage than we've been shown, and of better quality, and they had an employee on board the helicopters sent there with the specific assignment by combined Tepco and Japanese Government order to assess the water levels of the pools.

 

[MadderDoc]

Here are some thoughts on the Unit 3 1st floor PVC shield plug being moved from Genn Saji, former Secretariat of Nuclear Safety Commission, Japan:

I would like to see it in context. "Spontaneous venting" ?

 

[MadderDoc]

<..>
Although U3 pool didn't seem to be steaming at that time, whereas U4 pool was steaming vigorously. Perhaps that invoked fear that U3 pool was a deep dark hole with no water left to boil.

Iffy. Tepco said on the press conference that day that the steam from the Unit 3 building had been found to be coming from the pool, not the reactor.

 

[SpunkyMonkey]

I would like to see it in context. "Spontaneous venting" ?

He's also taken the view that there was a PCV overpressure event(s) accounting for the ajar hatch plug. As much as that happily fits with my theory, how do we explain the small lightweight objects in the hatch passageway? I'd expect they should have been blown out of the passage had a huge impulse blasted through it. Or maybe they were dropped during an earlier but recent inspection of the passageway. We probably shouldn't expect to find them in the passageway anyway if when the plug is closed it fits with perfect tightness.

But something certainly made the first floor a mess, exactly matching a hurricane-like wind blowing through it. So everything fits for an overpressure blowing through, minus those two tiny objects in the purported blow path.

ADD: I think by "spontaneous venting" he means caused by a series of small explosions(?) in the PCV. It seems a bit of a stretch to correlate the radiation readings on campus to these hypothetical events in Unit 3, but it also seems like an interesting idea.

Tepco shot more video footage than we've been shown, and of better quality,

Is that known or assumed? I'd suspect so myself, but I don't know so. We're taking about around April 16, 2011 of course.

What is it that you're getting at, if anything, with this line of inquiry? Are their plausible motives to mislead the public that they were worried about pool 3 being dry?

 

[LabratSR]

I didnt see this posted yet. Sorry if it has been already.


April 23 Fukushima Unit 4 Walkthrough
http://youtu.be/qZOqyEzhGGQ

 

[MadderDoc]

<..>
Is that known or assumed? I'd suspect so myself, but I don't know so. We're taking about around April 16, 2011 of course.

I assume you meant to write March. The press kit from March 16 included a reasonable quality still from a non-published video sequence.

What is it that you're getting at, if anything, with this line of inquiry? Are their plausible motives to mislead the public that they were worried about pool 3 being dry?

The latter question would seem to be OT. My inquiry is directed at finding Tepco's technical rationale for letting people risk their lives to splash some water onto unit 3.

 

[jim hardy]

Tepco said on the press conference that day that the steam from the Unit 3 building had been found to be coming from the pool, not the reactor.

which led me to assume pool was low on water. If full it should have considerable thermal capacity and be not steaming yet ?
Per m'doc's post 13115 two pages back its decay heat load was only ~half megawatt.


Cross section, probably a generic drawing, looking toward ocean and pool appears on right

drawing looking West (toward land), pool appears on left side as in helicopter video

Cracks in the pool wall on reactor side (from PCV flexing ? ) would leak pool water into basement ?
That's the pool that got 4800 tons of water.
Almost 4X as much as unit 4 got(1278). But 4's pool has 5X the heat load of 3's.

As you said - i should look for something that destroys that hypothesis not supports it.

old jim

 

[MadderDoc]

Cracks in the pool wall on reactor side (from PCV flexing ? ) would leak pool water into basement ?
That's the pool that got 4800 tons of water.
Almost 4X as much as unit 4 got(1278). But 4's pool has 5X the heat load of 3's.

As you said - i should look for something that destroys that hypothesis not supports it.

old jim

On SFPs, tsutsuji posted a while back, a translation of a part, and a link to the original document:
https://www.physicsforums.com/showpost.php?p=3813126&postcount=12587

I did a quick BOE reality check of the data given there of the refill demand rate of SFP3 during concrete pump injection, and fwiw found it to be consistent with the decay heat of the pool.

 

[SpunkyMonkey]

I assume you meant to write March. The press kit from March 16 included a reasonable quality still from a non-published video sequence.

Right, I meant March. Could it be a photo (not video frame) you refer to? I think for safety the helicopter avoided a direct flyover, so I'm not sure they got much closer than we've seen.

The latter question would seem to be OT. My inquiry is directed at finding Tepco's technical rationale for letting people risk their lives to splash some water onto unit 3.

But you seem to be arguing that they had to know the pool wasn't dried out or close thereto, and yet to the contrary were saying that's what they thought. Btw, I'm not against considering if Tepco's been less than honest. There's a well-known history of coverups and evasion in Japanese nuclear industry that includes Tepco. The level of public scrutiny they're under now is probably the best deterrent, but we shouldn't assume it's an ironclad safeguard.

 

[jim hardy]

As the full water level was reached when half the predicted quantity of water had been used, it was confirmed that the predictions of evaporated quantities made until then had been conservative, and that more water had been injected than the needed quantities. Among the quantities that were injected until then, it is thought that the surplus overflowed. After the water injections that were inferred as having generated overflows, although the causal relationship is unclear, a phenomenon where the temperature in parts such as the bellows seal, rises and declines within a short time was observed.

Thanks doc i had missed that one.