Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[zapperzero]

Cryptome.org posted some Japanese pdfs about the construction of Fukushima Daiichi.

It looks like there is information about the underground rock layers in it.

http://cryptome.org/0004/daiichi-build-01.pdf
http://cryptome.org/0004/daiichi-build-02.pdf

Yeah I sent those

 

[StrangeBeauty]

...
The only confirmed reports of Plutonium found so far have been at extremely low levels that could be leftover from the Fat Man bomb dropped on Nagasaki or from other atmospheric testing of plutonium weapons. ...

I'm not sure of the quality of this report:
http://search.japantimes.co.jp/cgi-bin/nn20110606x2.html
but it is echoed here and here:
http://mdn.mainichi.jp/mdnnews/news/20110606p2g00m0dm011000c.html
http://www.guardian.co.uk/world/2011/jun/07/japan-doubles-fukushima-radiation-leak-estimate

By analyzing the ratio of three types of isotopes in the plutonium, Yamamoto was able to determine that it was emitted by Fukushima No. 1 and not past bomb tests.

If true, this would be confirmation of Pu from Daiichi...?
What is the credibility of "Professor Masayoshi Yamamoto of Kanazawa University" and has there been any peer review?

See the links in the ex-skf article for more evidence...
http://ex-skf.blogspot.com/2011/06/now-they-tell-us-series-strontium-was.html

Edit: wow reading those articles via ex-skf. Which isotopes are next that they just didn't feel like announcing? Also: "The amount of hydrogen gas in Reactor 2 was 0.8 ton, and 1 ton in Reactor 3."

 

[Bodge]

http://ex-skf.blogspot.com/2011/06/now-they-tell-us-series-strontium-was.html"

Not good at all.

If people had been informed back when the measurements were taken, future leukemia risks could have been reduced.

"Where there's cesium there's strontium"?

Well I sure see a lot of caesium:
http://i.imgur.com/5uvVU.png
http://www.bfs.de/de/ion/imis/ctbto_aktivitaetskonzentrationen_caesium.gif

What does this data tell us about the temperature of the cores during the first week?

 

[zapperzero]

What does this data tell us about the temperature of the cores during the first week?

Zip. Nada. Nothing. Cesium starts to evaporate at 25 degrees Celsius iirc.

 

[Bodge]

Zip. Nada. Nothing. Cesium starts to evaporate at 25 degrees Celsius iirc.

I was actually thinking about the strontium being found 62km away:

Melting point 1050 K, 777 °C, 1431 °F
Boiling point 1655 K, 1382 °C, 2520 °F

 

[rowmag]

First found by rowmag here early this morning

He posted a similar link for the second one a short time later. Those documents are obscure enough to make it highly unlikely that cryptome and rowmag found them within a few hours of each other out of sheer coincidence. Just sayin'.

Edit: Cryptome's source for the docs confirmed on next page. Good job, zapperzero.

That may be copyrighted material. The publisher generously enough allows free downloads directly from their site, using the procedure I outlined upthread, so I would like to suggest that folks please play nice and support them.

 

[MiceAndMen]

That may be copyrighted material. The publisher generously enough allows free downloads directly from their site, using the procedure I outlined upthread, so I would like to suggest that folks please play nice and support them.

Yes, a good point. It's sad, though (and OT), how copyrights are for so long a period of time. But that's a different discussion for somewhere else.

 

[Bioengineer01]

With all respect, that theory seems to me intensely implausible.
The explosion in reactor 3 was a coarse detonation, leaving huge chunks of stuff flying through the air.
Had it tossed out bits of the fuel from the SPF, one would expect fuel rod assemblies among the debris, not microscopic traces so minute that it takes effort to distinguish them from bomb test fallout.
Imho, the scenario of vapor leaks from the molten fuel in reactor 1 fits the data much better.

Would it be plausible if it really came from the RPV of Unit 3, where the bolts holding the cap stretched and allowed the top to partially open during the explosion. This theory is the worst case scenario of somebody else, sorry don't remember whom...

 

[NUCENG]

That may be copyrighted material. The publisher generously enough allows free downloads directly from their site, using the procedure I outlined upthread, so I would like to suggest that folks please play nice and support them.

If we post a link to original copyright owner site, is that OK? I know the PF posting guidelines recommend not quoting large portions of articles to prevent violation of copyright information.

 

[swl]

All evidence suggests that the vertical part of the #3 explosion originated in the SFP, not the containment structure, hence the source for the plutonium would be the SFP.

This is simply not the case. The fact is, we don't know what caused the vertical portion of the explosion from the #3 reactor building. Making false assertions does little to further the value of this thread.

Starting now, I for one, will attempt to avoid rehashing old issues that have been adequately covered in this thread until such time that there is something new and useful to add. It is my hope that we can avoid pushing the signal to noise ratio down to the point where the thread is irrelevant.

 

[Bioengineer01]

There are several papers on the web that describe how the ablation of concrete by corium depends heavily on the type of concrete. For limestone concrete the ablation is isotropic, while for silica concrete the ablation is anisotropic.

http://journals1.scholarsportal.info/details.xqy?uri=/03064549/unassigned/nfp_tioocwctvvts.xml

There are other papers you can find using google. Some are recent, some not so recent. A quick glance at them suggests that it would definitely be possible to detect if concrete ablation was occurring assuming, of course, you had working sensors nearby. Another reason to start preparations for probing inside the PCVs.

I read several papers on ablation and experiments trying to different methods to stop them. Conclussion is that it is hard to stop it even under controlled experimental conditions. I guess my point is that if it can be done, it is being done. But I am not sure what can be done to tack it in a reliable way. The papers I read didn't deal with this aspect. Whether they are telling the results or not, is another topic. But knowing the Japanese, I have no doubts that if they can do it, they are doing it. This is just too important for Japan.

 

[robinson]

Rehashing, especially if it's cogent and precise, would actually be quite helpful to the new people showing up. This topic seems to have become the only intelligent discourse on the internet about the reality of Fukushima.

I've read every single post, but can't remember everything at this point.

 

[MiceAndMen]

If we post a link to original copyright owner site, is that OK? I know the PF posting guidelines recommend not quoting large portions of articles to prevent violation of copyright information.

The articles in question are in Japanese, so quoting would be limited to Japanese text and asking someone to translate. We might ultimately end up with the whole article translated, which would completely be against the fair-use spirit of limited reproduction of copyrighted works. Then there is the matter of Japanese copyright law which I am totally unfamiliar with.

Being able to read the text would be nice, but my inability to read Japanese is my problem, not the author or publisher's. For the 2 articles in question, that's OK though because the diagrams and pictures convey substantial information by themselves.

I was using Google Translate to get some idea of the article text, but it's slow going. For example, first article, first section, title is

1. まえかき

which google translates as "For Example Oyster Or". I gave up soon thereafter.

 

[Bioengineer01]

http://ex-skf.blogspot.com/2011/06/now-they-tell-us-series-strontium-was.html"

Not good at all.

If people had been informed back when the measurements were taken, future leukemia risks could have been reduced.

"Where there's cesium there's strontium"?

Well I sure see a lot of caesium:
http://i.imgur.com/5uvVU.png
http://www.bfs.de/de/ion/imis/ctbto_aktivitaetskonzentrationen_caesium.gif

What does this data tell us about the temperature of the cores during the first week?

Yes, but what is even a lot more concerning to me is what does it tell us about what this data tells us (technical community and scientists) about what we are being told today... And I am not talking what the general public is being told, I am talking about what academicians and universities and official agencies are being told. It is sad to see how emails full of lies were sent from official sources to universities and departments of nuclear engineering around the world in the early stages of the tragedy. It is documented in this forum. And I am not talking here about politics, I am talking about how to interpret the data we have in front of us and go for the most likely explanation that fits most of the data, not all of it, since this data tells us that active efforts were used and most likely are being used (past behavior is the best predictor of current and future behavior) to prevent some of the data to come to light...

 

[Bioengineer01]

The opinion of an expert in the measurement of radiation about the Tokyo measurements

5.77 microsieverts per hour of radiation measured near Tokyo at ground level — Gov’t “is desperately trying to keep it quiet” (VIDEO)
June 7th, 2011 at 03:58 AM

http://enenews.com/5-77-microsieverts-per-hour-of-radiation-measured-near-tokyo-at-ground-level-govt-is-desperately-trying-to-keep-it-quiet-video

He says:
"The video looks legit. His whole body count isn't that high but next to that sewer/drain-off he's in the perfect spot to test for higher levels. 50x normal is most likely real. That's why I was saying that bottled and imported water is going to be huge in Japan! That Dosimeter is being used as a Geiger counter. The sensor is really small so it takes some time to ramp up to the correct reading. The water table in Japan is trashed.

I can't imagine how radioactive the water below is. It looked like most is in the Alpha and Beta range as that water is a wide line source and gamma would penetrate the ground and his meter would be detecting it from a distance.

If you can contact the guy. Try to get him to take a sample of the water without touching it (tell him to treat the water like its poison) I bet without all the Beta and Alpha being blocked by the ground. A vial of that stuff might measure 1000X background with the right meter. His meter has a 40Kev~1.5Mev Range so it's not going to pickup everything."
http://lunaticoutpost.com/Topic-Nuclear-Power-plant-Onagawa-on-fire-Fukushima-malfunctions?pid=1236881#pid1236881

 

[jim hardy]

i just can't get excited by microscopic amounts of reactor protoplasm detected anywhere downwind.

I was active at another blog in the early days. Here's what i recall from the time.

We looked into the "Neutron Beams" when news reports of them first showed up. The false positive on CL38 combined with "neutron beams" was real scary.

.. From the plant logs available then it appeared the "beams" were measured at main gate's neutron monitor 12-15 March. A resident of Japan translated the newspaper reports for us and "beams" meant more like individual 'rays' or particles than an intense beam like a searchlight. That was consistent with the English version of press release which said less than 0.02uSv/h, which isn't a lot of neutrons.

At the time i proposed it was somebody walking past the monitor with contaminated boots.

Later we found that the times on logsheets were shortly after water injection. That made it seem obvious - ever pour water on a campfire and watch how much ash goes up with the steam?
I was unaware until recently their vessel was likely already breached at that time. If so, there's the path for flyash right around the SRV's into drywell. There are plenty of occurrences of phrase "PCV vent" in the IAEA report as early as March 12,,, Adobe search works well on M&M's one piece document.

maybe NucEng knows if that "PCV Vent" term infers bypassing the torus so flyash could go right out to the stack without scrubbing in Torus.

My point is it does not startle me that when a dried out reactor core gets suddenly hit by water it might sizzle and sputter and spew some ash-like particles that get wafted out with the steam and drift away. What does amaze me is our remarkable ability to measure it in minute amounts.

Some of the atoms in that reactor ash should be Pu, and all the other stuff they found in the car air filter described over at StrangeBeauty's ExSkf link comments section:

late May: "We tested an air filter from a car in Tokyo. It full of particles of strontium, metallic zirconium and Zr alloys, iron and steel encrusted with terbium, yttrium, lanthanum, and neodymium. There are bismuth/rhenium particles. One nearly pure strontium particle is crusted with sodium chloride, a k a seawater."

One assumes it was a radionuclide analysis, he didn't say.
He didn't say whether the car had been driven near the plant either.

The Sr coated in salt might suggest it was from some incore rowdiness associated with seawater injection. But -- that claim should be made by somebody who knows more chemistry than me.

There's my second point -- rehash can be useful to tie together loose ends from early observations, but we must remain vigilant against speculation and unsupported claims..

 

[Bioengineer01]

Assuming we are not being told everything and somethings are being actively hidder. The behavior of a US air craft carrier battle group may be relevant data to consider...

"...You have to remember at the time that Fukushima was in desperate need of diesel fuel for their generators and electricity to run the plant. The United States sent the USS Reagan and it’s carrier battle group (not the whole navy fleet).

They were reported to be steaming to Fuku and about 100 miles out when #3 blew. 100 miles in an aircraft carrier is about 3-4 hours travel time. The explosion happened just before nightly news time in the US – so all the news shows had live feeds on what was going on – because they hadn’t begun covering everything up yet.

So somebody on live TV revealed that the navy had detected “low level” radiation in the cloud and Reagan was diverting. This was met with surprise on the news, but accepted as normal. For those of us with military experience though, it meant much more. The Navy doesn’t divert an aircraft carrier on a mission. Those things are made to take on anything – (except for a MOX cloud I guess)..."

Reader comment: James2
June 8, 2011 at 7:38 am
http://enenews.com/govt-report-suggests-situation-worse-meltdown-worst-possibility-nuclear-accident
https://www.physicsforums.com/attachment.php?attachmentid=36260&stc=1&d=1307587734

 

[etudiant]

The Asahi Shimbun coverage of the TEPCO culture continues with segment 2.
http://www.asahi.com/english/TKY201106080182.html

It suggests that a long period of success and a strong desire to avoid creating any concerns had a debilitating effect on the flexibility of the operators, as well as on their detailed understanding of their systems under non standard conditions.

 

[Atomfritz]

Questions:

1. Where is the Japan CTBTO sensor? Are the peaks in CTBTO data correlated with wind direction to the sensor from the Fukushima site?

2. Have the peaks been checked for increases in other short half life isotopes?

3. If the peaks are due to short recriticalities shouldn't the increase be followed by an exponential decay from the new peak? It looks like they drop right back to the decay trend that was in place before the short peaks.

4. Shouldn't the Unit 1 drywell radiation detectors show some time delay to the CTBTO sensor unless that sensor is on site.

Regarding questions #1/2 see Bodge's post https://www.physicsforums.com/showpost.php?p=3342625&postcount=9081".

Regarding question 2: All these measurements have been and are being done, but no exact details published by Tepco (usually only I and Cs, as you know). Unless these are published one cannot rule out the possibility that there is something going on.

Regarding question 3: It would require relevant production of new FPs to make a relevant difference to a "background radiation" approaching 250 Sv. So can the absence of a decay ramp really be a proof that there is no oscillating recriticality in a small core part in the RB or CV?
Wouldn't this send out intensive radiation during reaction until dying out, and after that go unnoticed like an recently used, but now inactive "Slotin toy" probably would in this really big nuclear mess?

Regarding question 4: The distance of the sensors (100/200km) will, depending on the weather, eventually cause some phase and amplitude shift with the measurements on site (that usually are not published en detail). If I consider this there I cannot deny that to me there seem to be some coincidencies.

So how does plutonium get out of a nuclear reactor? Or spent fuel pond? It's not like the airborne isotopes, wafting about in the air, the steam, the smoke. Right?

It doesn't float or escape in a cloud of steam. Does it?

Yes, but not that easily like Iodine, Cesium or even noble gases for instance.
As Plutonium is very heavy and reactive, most of it usually clings to other material, making "hot particles".
Most of them fall down in a range of around 30 km, but some are distributed worldwide.

This btw is lesson learned from old russian nuclear mishap experience, so the 30km zone around Chernobyl.
Experience from many accidents/"experiments" has shown that more than 9/10 of the emitted plutonium goes down in a radius of 30km.

I have heard that soil chemistry is complicated.

It is, indeed. So the behavior of the various elements which we worry about some isotopes. In fact there has been much research. Just google "soil nuclide distribution" or such.

There could be hot spots of iodine on the debris/in the ground and then depending on how water is flowing/diluting we could see some sudden changes in the relative amount of cesium/iodine although this would not necessarily prove re-criticality.

Afaik iodine is one of the most volatile non-gaseous nuclear contaminants and mostly is present in ion form, I don't think that there are to be expected hot spots/hot particles like those of Plutonium, Strontium etc. So I doubt this a bit.

Interesting why they are installing this not in center of SFP, sfp is weakest there ?, the point where they are installing it is strongest I think (because of drywell thick): http://www.tepco.co.jp/en/news/110311/images/110607_1f_2.pdf

The spot marked in green on the bottom left diagram is where the steel support pillars will be - under the middle of the pool.

Looks like they'll also build a concrete wall at the red spot next to the dry well wall.

This worries me. The photos reveal interesting things.

1. It is interesting that the floor and ceiling of the room is not shown in the photos.
Are they already cracked? Is there danger of other cracks extending?
If not so, why then the support?

2. The support bars do not have diagonal reinforcement bars, as would be necessary to avoid deformation under load.
Instead they show mounting plates for mounting something like metal grouting forms.
This indicates they will probably mount steel plates as rebar and concrete form onto the pillars and pour in concrete, else the SFP support would probably not be very earthquake resistent.

How will they vibrate/compress the concrete correctly with that dangling SFP above them?
Or even drill/hammer out mounting holes in the floor, walls and ceilings etc?

Really scary construction site!

3. If the assumption is correct that they just fill the inner half of the room below the SFP with concrete this could make bad things even worse.
The walls are covered with thick epoxy painting, what makes up a very strong insulation. The concrete will not stick well to the wall, until this insulating paint cover is removed with demolition hammers, sanding etc.
There is no rebar connection to keep this heavy blob of concrete in place in case of a new heavy quake, as it does not adhere with the walls/floors.
So this loose giant thing will put heavy additional loads onto the already-weakened structure on the next big quake.

This kind of "support reinforcement" could finally pry open, crack and leak the still-intact SFP walls!

If Tepco is really so desperate doing such then I wonder what surprises this haunted plant still has for us what we have not been shown yet...

 

[razzz]

Since while replacing the shroud and rearranging the spent fuel pool to carry the load of at least two cores worth of assemblies and it didn't fail during a 9+ quake with aftershocks, I'd say the chances are good of propping up the pool to withstand the next great quake. Appearing dry and clean it amazes me that they can actually work in there.

 

[westfield]

Interesting why they are installing this not in center of SFP, sfp is weakest there ?, the point where they are installing it is strongest I think (because of drywell thick): http://www.tepco.co.jp/en/news/110311/images/110607_1f_2.pdf

Perhaps their concern is the fuel handling machine falling into the pool of RB #4?

And\ or, yes as you have noticed, perhaps another reason is that particular place has the best support from below, ie, the concrete to be poured will largely place load on the super strong containment structure itself, rather than the less strong reinfoced concrete framework & floor of the surrounding RB.

Or some other reason that is nothing at all to do with the above.

 

[rowmag]

If we post a link to original copyright owner site, is that OK? I know the PF posting guidelines recommend not quoting large portions of articles to prevent violation of copyright information.

They don't have fixed links to articles on their site. You have to sign up for a "trial mail," wherein they send you a temporary link to an article, in exchange for the right to send you notices -- presumably enticements to sign up for a full subscription so you can keep up with the latest developments in Japanese civil engineering. Who knows, you might become addicted. Even if you don't, by going through the publisher-approved route to get the paper, you will have at least boosted their click/circulation numbers, which they may appreciate. And the clean conscience is yours to keep for free.

Let me recap the proper process.

To download a paper on TEPCO's civil engineering for the Fukushima Daiichi site, which was published in the journal "Civil Engineering Technology" in 1967, click here:

Part 1: http://www.doboku-g.com/DownloadPDF.aspx?TocID=6608
Part 2: http://www.doboku-g.com/DownloadPDF.aspx?TocID=6637

In the middle of the page that shows up, there is a blue box, inside of which you have to provide a mail address twice (and not an obviously free mail address), check a box to the lower left agreeing to let the journal send you notices now and then, and click on the button in the lower right. With this you will be mailed a URL from which to download the PDF file.

 

[razzz]

If remember right, Japan failed to inform the US Navy Unit 3 just had vented itself.
Nuclear fallout plays havoc with a nuke carrier's sensors, bet they were looking for an on-board nuke leak first or at least their instruments alerted them to high concentrations. Of course being somewhat educated, they left the area.

 

[westfield]

This worries me. The photos reveal interesting things.

1. It is interesting that the floor and ceiling of the room is not shown in the photos.
Are they already cracked? Is there danger of other cracks extending?
If not so, why then the support?

2. The support bars do not have diagonal reinforcement bars, as would be necessary to avoid deformation under load.
Instead they show mounting plates for mounting something like metal grouting forms.
This indicates they will probably mount steel plates as rebar and concrete form onto the pillars and pour in concrete, else the SFP support would probably not be very earthquake resistent.

How will they vibrate/compress the concrete correctly with that dangling SFP above them?
Or even drill/hammer out mounting holes in the floor, walls and ceilings etc?

Really scary construction site!

3. If the assumption is correct that they just fill the inner half of the room below the SFP with concrete this could make bad things even worse.
The walls are covered with thick epoxy painting, what makes up a very strong insulation. The concrete will not stick well to the wall, until this insulating paint cover is removed with demolition hammers, sanding etc.
There is no rebar connection to keep this heavy blob of concrete in place in case of a new heavy quake, as it does not adhere with the walls/floors.
So this loose giant thing will put heavy additional loads onto the already-weakened structure on the next big quake.

This kind of "support reinforcement" could finally pry open, crack and leak the still-intact SFP walls!

If Tepco is really so desperate doing such then I wonder what surprises this haunted plant still has for us what we have not been shown yet...

re 1. - Perhaps their concern is the fuel handling machine falling into the pool.

re 2. - formwork doesn't need diagonals as the face of the formwork itself when fitted braces the formwork. re setting the concrete, vibration would be fine and finishing with an expanding grout would be the norm in any situation where new concrete structure is required to "pick up" existing load.

re 3 - It would be no problem to fix steelwork to the existing concrete structure. Even if the epoxy coating was removed as you suggest, there would be no proper bond of any strength between old and new concrete. If they have that concern then it's easily negated by fixing steel before the pour.

imho, in the scheme of things there is nothing wrong with the pool as such at the moment but there is a concern about the fuel handling machine or other heavy item falling in the pool and overloading its floor. I have no evidence whatsoever to back up that idea.

 

[NUCENG]

The source says it exceeds 100 Sv/h at that stage, so the number is >100 Sv/h.



I suppose an expert could do a better job than I, otoh since in the context it is more a question of producing a rough order of magnitude estimation.. :-)

If the spent fuel after ten years in the pool is at >100 Sv/h, I'd expect it to be at >1000 Sv/h after one year in the pool, and plausibly at >10000 Sv/h at the time of removal from the core, i.e when the fuel has been fully spent. So, doing simple interpolation I'd find it plausible that half spent fuel could have an activity of >5000 Sv/h, give or take one order of magnitude.

I did some rough calculations to get estimates of dose rates due to fresh fuel being ejected. I used a simplifying assumption that gamma and beta radiation of all energies have the same effective dose rate. As a result I believe the results are probably within one order of magnitude of a more detailed calculation. It only considers external dose and neglects neutron and alpha radiation effects.

A complete bundle at the instant of shutdown near end of useful life will produce about 9000 Sv/hr at 1 m distance.

An average fuel pellet at shutdown at 1 m will produce a dose rate of about 500 mSv/hr at 1 m and a contact reading of 500 Sv/sec on contact,

The decay rate will follow the fractional trend as follows:

1 sec 30 min 1 hour 8 hours 1 day 4 days 30 days 90 days 180 days
9.92E-01 5.48E-01 4.53E-01 2.46E-01 1.85E-01 1.20E-01 4.66E-02 2.31E-02 1.24E-02

1 year 3 years
5.82E-03 2.40E-03

 

[elektrownik]

Can someone look at my post about unit 5 here: https://www.physicsforums.com/showpost.php?p=3346232&postcount=9333
I don't understand still what they were doing there, if the reactor was at 7MPa it must be on ? I don't remember information about scram in unit 5, it was reported always as cold shutdown

 

[sp2]

Since while replacing the shroud and rearranging the spent fuel pool to carry the load of at least two cores worth of assemblies and it didn't fail during a 9+ quake with aftershocks, I'd say the chances are good of propping up the pool to withstand the next great quake. Appearing dry and clean it amazes me that they can actually work in there.

I have to say, I'd draw the opposite conclusion.

They didn't have a 9 at Fukushima, they had a 9 a hundred miles out to sea.
What they got at the plant (if I remember correctly) was more like a 6.8, or something in that ballpark.
And that was *still* enough to give them some shakes that actually *exceeded* their design limits.
Similarly, the big 7+ after-shake a month later was enough to shake some meters at Onagawa beyond *its* rated limits.

Clearly, whatever the level of Dai-ichi-4's shake-resistance now, it's got to be lower than before (and possibly a *lot* lower).

The combination of these simple facts should be enough to scare the crap out of any objective analyst, and to convince us that a large after-shock in the near vicinity of Dai-ichi is entirely capable of bringing something down.

Since the seismological theory holds that very-large quakes are capable of producing after-shocks as big as 1 point below their initial magnitude, we can probably conclude that there's still *plenty* of reason for concern.

 

[NUCENG]

Regarding questions #1/2 see Bodge's post https://www.physicsforums.com/showpost.php?p=3342625&postcount=9081".

Regarding question 2: All these measurements have been and are being done, but no exact details published by Tepco (usually only I and Cs, as you know). Unless these are published one cannot rule out the possibility that there is something going on.

Regarding question 3: It would require relevant production of new FPs to make a relevant difference to a "background radiation" approaching 250 Sv. So can the absence of a decay ramp really be a proof that there is no oscillating recriticality in a small core part in the RB or CV?
Wouldn't this send out intensive radiation during reaction until dying out, and after that go unnoticed like an recently used, but now inactive "Slotin toy" probably would in this really big nuclear mess?

Regarding question 4: The distance of the sensors (100/200km) will, depending on the weather, eventually cause some phase and amplitude shift with the measurements on site (that usually are not published en detail). If I consider this there I cannot deny that to me there seem to be some coincidencies.
..

I don't find a wind direction correlation, but the met data is only for Fukushima and you may need to know what the wind direction was at the transport time before the measured reading at the CTBTO sensor.

Question 3 is about the graph which shows I-131. The base decay rate is about a half life of 8 daya. The individual peaks are about a factor of 10 and if they aren't due to wind I would expect that they would decay from the new peaks at about an 8 day half life. Inmstead the drop back an order of magnitude in as little as one day. That now seems to confirm what I was trying to find in questions 1 and 2.

Question 4 The problem with the met data provided is that it is an average direction and windspeed for a 24 hour period. If the wind speed is less than 10 km/hr there will be nearly a full day time shift from the peak at Fukushima to a sensor 200 km away. The peaks that seem to corelate seem to have no time shift.

 

[razzz]

Can someone look at my post about unit 5 here: https://www.physicsforums.com/showpost.php?p=3346232&postcount=9333
I don't understand still what they were doing there, if the reactor was at 7MPa it must be on ? I don't remember information about scram in unit 5, it was reported always as cold shutdown

Decay heat? Assemblies need constant water circulation to remove the heat, can't be left alone unattended unless they can be committed to air cooling.

 

[razzz]

I have to say, I'd draw the opposite conclusion.

They didn't have a 9 at Fukushima, they had a 9 a hundred miles out to sea.
What they got at the plant (if I remember correctly) was more like a 6.8, or something in that ballpark.
And that was *still* enough to give them some shakes that actually *exceeded* their design limits.
Similarly, the big 7+ after-shake a month later was enough to shake some meters at Onagawa beyond *its* rated limits.

Clearly, whatever the level of Dai-ichi-4's shake-resistance now, it's got to be lower than before (and possibly a *lot* lower).

The combination of these simple facts should be enough to scare the crap out of any objective analyst, and to convince us that a large after-shock in the near vicinity of Dai-ichi is entirely capable of bringing something down.

Since the seismological theory holds that very-large quakes are capable of producing after-shocks as big as 1 point below their initial magnitude, we can probably conclude that there's still *plenty* of reason for concern.

I get what you are saying but is there a better plan for Unit 4 at the moment? It is just like not letting basements overflow with contaminated cooling water or the site itself will become 'hot,' pumping contaminated water out to sea while sad is the only option until storage is completed.