Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[Jorge Stolfi]

Careful with these frames, they only show an integral over what happened within 1/25 s, faster dynamics will appear washed out.]

Also note that MPEG/JPEG encoding creates complicated artifacts. The shape of any detail that is smaller than 8x8 pixels is usually mangled beyond recognition. (If the detail persists unchanged over several frames you may recover some of the lost information by aligning and averaging, but that is not the case here.)

Moreover, color information is lost for objects that are too bright: the camera will just record white.

All you can tell from that pair of frames is that there was an orange or orange-white flash on the south side of the building, probably at the SE corner, about level with or above the service floor --- which is the location of the SFP. I believe it is not possible to extract further details of the flash shape and dynamics from that video.

 

[pdObq]

similar train of thought explored on this thread, on May 7 i think, its page 314 viewed in Firefox don't know about explorer. Look for two long posts by Analog, and don't miss the videos on Borax. http://tickerforum.org/akcs-www?post=182121&page=314#new

Very interesting, thanks for that cross-link, Jim! Seems like other forums might be ahead of this one in terms of brain-storming (or speculation if one wants)...

I haven't had time to look through all the details and references in those posts by that Analog guy , but if people with hands-on experience who know what they're talking about also came up with that and consider it a possibility, I almost feel a bit like knighted .

And seriously isn't recriticality inside the RPV much much more likely than in the SFP? (If one assumes something actually did go critical.)

 

[MadderDoc]

but it is lying on top

Roofs normally do.

As regards the long ballistic object, I may have a candidate for that. It is something that clearly has come from above, and has sunk deep into the annexed building at the north side of unit 3. It must be very heavy, lots of iron. See attachments.

 

[pdObq]

Another and better explanation might turn up, until then I see heat damage.

How about the rail for the big overhead crane banged against the pillar during the explosion?
(Where is it now? I don't know.)

 

[GJBRKS]

Forgive me if this was done before, after having found the location of the camera by aligning the HV line tower with the left most stack and reactor unit 1 (https://www.physicsforums.com/showpost.php?p=3296107&postcount=6694") and the heading of the sight line being 36.04 degrees to the centre of unit 4 south wall, and taken that wall as 34 metres. We then can scale the photo of the explosion quite accurately (34 Cos 36.04 = 27.5)

As the building top is OP+55 metres making the stacks about 90 metres high from ground level.

The speed of the column rising is about 50 m/s or 1800km/hour

I also added some further dimensions, showing that the roof sheets got carried up to around 150 metres above the roof top of the reactor buildings and tried to size the black object, the two white objects are about half the size.
[PLAIN]http://k.min.us/inBoDM.jpg[/QUOTE]

Your speed and height calculation would agree with a ballistic trajectory :

http://img641.imageshack.us/img641/2843/ballisticf.jpg


(Though I think you mean 180 km/hour instead of 1800)

 

[Bandit127]

Your speed and height calculation would agree with a ballistic trajectory :

http://img641.imageshack.us/img641/2843/ballisticf.jpg


(Though I think you mean 180 km/hour instead of 1800)

So - can we assume it didn't float up on the top of clouds or ballons then? Or do I have to still consider (the equivalent of) a piano soaring atop a cumulus feasible?

 

[AntonL]

(Though I think you mean 180 km/hour instead of 1800)

Yes 180 it is - edited my post accordingly

 

[~kujala~]

TEPCO's thinking is evolving regarding the missing water of unit #1:

The utility says the leaked water is likely in the basement of the reactor building -- still a no-go zone due to concerns over high radiation levels.

http://www3.nhk.or.jp/daily/english/13_34.html

I bet it's not going to take long until they admit that a leak from the basement of the reactor building into the groundwater is also likely - a scenario that should perhaps not be possible but seems to be happening under #1 and #4.

 

[MadderDoc]

Also note that MPEG/JPEG encoding creates complicated artifacts. The shape of any detail that is smaller than 8x8 pixels is usually mangled beyond recognition. (If the detail persists unchanged over several frames you may recover some of the lost information by aligning and averaging, but that is not the case here.)

As a general remark I totally agree, and there are indeed many very poor videos of these explosions, horribly re-compressed and color-releveled. The details we are looking at in this video is far, far larger than 8x8 pixels. A high quality HD source video was carefully selected for the exposee of the explosion at unit 3. While we should take care not to put too much trust in the images we see, we should also take care not to take them on as less trustworthy than they are.

Moreover, color information is lost for objects that are too bright: the camera will just record white.

True. However when we see a flash of fire first being almost white aka very bright, and the next frames show the flame turning through shades of yellow to red, we can be pretty sure that what we see, is the effect of decreasing temperature of the flame.

 

[jim hardy]

""""I almost feel a bit like knighted .

And seriously isn't recriticality inside the RPV much much more likely than in the SFP? (If one assumes something actually did go critical.) """""

well check the references. It must be deemed possible by somebody in academia.

The idea falls apart if the pressure readings after event are real, unless one can hypothesize either a leak that healed itself or claim they were pressure difference across the leak as steam exited through it.

It will play out and somebody will be right. thanks for looking. i too feel vindicated.

 

[MadderDoc]

How about the rail for the big overhead crane banged against the pillar during the explosion?
(Where is it now? I don't know.)

On a scale from 1 to 10, how likely would you say that a collision with the rail of the big overhead crane would have left the pillar standing?

Edit: I have wondered myself where that rail has gone, I've seen indications that it may have been hammered down in the service floor, at the inside of the pillars.

 

[TheMundun]

There has been some discussion today about whether the Drywell breached and hot gases escaped into the Service Floor triggering another explosion. I hope this post will contribute more evidence to what exactly took place.
As I can run the sound track of Unit 3 in slow motion using VLC Media Player, I managed today to find some software that enabled me to see the changes in the frequency spectrum as the track played and so carry out further analysis of the frequencies and sounds. I took screen grabs at various points through the sound track, putting them into a pdf, see attached.
One of my discoveries is that the main harmonic frequency of the reactor /primary containment seems to be 1227.06 Hz.
More importantly, what I also found today was that around 0.4 seconds after the first explosion there is a quiet hiss with a peak frequency of around 2842Hz and then again 0.4 seconds after the 2nd explosion started and before the metallic sound starts, there is a much louder and clearer hiss with a peak of around 2850Hz. Interpreting these hisses, they appear to indicate that there were two escapes of gas from somewhere following the two explosions, both presumably originating in a vessel that breached. Whether it was the same vessel or two different vessels, I cannot say.
What I find bizarre is that the start of the track, the main sound centres around the harmonic frequency mentioned above yet just before the 1st explosion and between the 1st and 2nd explosions, the whole complex went practically dead quiet. Any ideas why?
See attached for the screen grabs. On opening, please rotate the slides to landscape (I did try saving them as landscape but...).

Geoff

 

[pdObq]

On a scale from 1 to 10, how likely would you say that a collision with the rail of the big overhead crane would have left the pillar standing?

Edit: I have wondered myself where that rail has gone, I've seen indications that it may have been hammered down in the service floor, at the inside of the pillars.

Well, that would depend on the type of collision and the speed of that rail, so I don't really know. It could also have been part of the roof trusses bumping onto the pillar while flying through the air...

 

[ElliotLake]

Forgive me if this was done before, after having found the location of the camera by aligning the HV line tower with the left most stack and reactor unit 1 (https://www.physicsforums.com/showpost.php?p=3296107&postcount=6694") and the heading of the sight line being 36.04 degrees to the centre of unit 4 south wall, and taken that wall as 34 metres. We then can scale the photo of the explosion quite accurately (34 Cos 36.04 = 27.5)

As the building top is OP+55 metres making the stacks about 90 metres high from ground level.

The speed of the column rising is about 50 m/s or 180km/hour

I also added some further dimensions, showing that the roof sheets got carried up to around 150 metres above the roof top of the reactor buildings and tried to size the black object, the two white objects are about half the size.
[PLAIN]http://k.min.us/inBoDM.jpg[/QUOTE]
Thanks for this.
If that black object is is roof sheeting though, it must have something substantial attached to it, as it neither looks nor moves like heavy metal sheeting I have seen peel off roofs in high winds.
Those move more the way leaves do, twirling and shearing sideways. Like flying blades, not blocky objects.
I would expect metal sheeting lofted by this explosion to not come down anywhere near vertically. The crumpled sheeting seen on the reactor grounds on the other hand, does look like what happens to free flying metal sheeting, not something still attached to framing.

 

[AntonL]

I would like to see a proper english translation of http://www.asahi.com/special/10005/TKY201105120706.html

By what I can make out it discusses un-published internal reports and documents by TEPCO that asahi claim now to have in their possession, more than 100 pages listing many parameters, trends, work groups etc. These documents reveal that on 13th March high radioactivity in or around Unit 3 were measured and observation of steam with high probability of hydrogen escaping into the building. (Unit 3 exploded on the 14th a day later)

If my interpretation of the machine translation is true, then Tepco have not only leaks in reactors.

 

[pdObq]

Thanks for this.
If that black object is is roof sheeting though, it must have something substantial attached to it, as it neither looks nor moves like heavy metal sheeting I have seen peel off roofs in high winds.
Those move more the way leaves do, twirling and shearing sideways. Like flying blades, not blocky objects.
I would expect metal sheeting lofted by this explosion to not come down anywhere near vertically. The crumpled sheeting seen on the reactor grounds on the other hand, does look like what happens to free flying metal sheeting, not something still attached to framing.

Were the concrete shield plugs on top of the dryer-separator storage pool? Could they be those flying "blades"? Where are they stored when they are not in place, possibly in the NW corner?? (I should really look at that service floor NRC document with the weights and stuff at some point...)

PS: The big chunk leaves a trail of dust when falling, I think that's one reason I think it might be something like concrete.

 

[NUCENG]

The EPA's RADNET site recently spiffed up their user interface, but they provide no guidance on interpreting the gamma graph's energy ranges. If anyone on the forum can associate isotopes with energy ranges that would shed some light. http://www.epa.gov/radiation/rert/radnet-data-map.html

For those of us in the SF Bay Area, a tip of the hat to UC Berkeley's Nuclear Engineering Dept. They've been monitoring air, rainwater, tap water, grass, soil, milk and food since mid March. They're running on student labor so the reports are updated only a few times a week http://www.nuc.berkeley.edu/UCBAirSampling

For detailed information on isotope decay see
http://atom.kaeri.re.kr/index.html

For direct conversion of dose from a radioisotope see FGR 11, 12
http://www.epa.gov/radiation/federal/techdocs.html

 

[MadderDoc]

<..>
PS: The big chunk leaves a trail of dust when falling, I think that's one reason I think it might be something like concrete.

Dust would seem to be to a concrete chunk that has been hurled 100s of meter in the air, like moss to a rolling stone. Could it be something hot, smoking? Several of the objects falling out of the cloud leave dust/smoke trails.

 

[Borek]

Also note that MPEG/JPEG encoding creates complicated artifacts. The shape of any detail that is smaller than 8x8 pixels is usually mangled beyond recognition. (If the detail persists unchanged over several frames you may recover some of the lost information by aligning and averaging, but that is not the case here.)

We've been through that eons ago, I would like to remind you all this quote:

I have known a couple of photo recon interpreters who told me it is hard not to see things after looking at a photo too long or too hard. I have spent a lot of time in BWR reactorbuildings and I don't recognize very much in the wreckage. We've already heard that there was a body in one photo. Next thing is likely to be somebody spotting bin Laden.

 

[Borek]

As I can run the sound track of Unit 3

Please search the thread - it is not clear (at least to some) whether the sound is really part of the recording and whether it was not added from some other source.

 

[MadderDoc]

We've been through that eons ago, I would like to remind you all this quote:

I'm afraid I don't get the message. Do you think this quote is memorable?

 

[MiceAndMen]

TEPCO's thinking is evolving regarding the missing water of unit #1:

http://www3.nhk.or.jp/daily/english/13_34.html

I bet it's not going to take long until they admit that a leak from the basement of the reactor building into the groundwater is also likely - a scenario that should perhaps not be possible but seems to be happening under #1 and #4.

What do they mean by reactor building "basement"? Are they referring to the excavated space where the torus is located underground? Are there additional subsurface rooms or spaces?

 

[Borek]

Well, it introduced Bin Laden to the thread.

Seriously, at about the time NUCENG posted his comment it was becoming obvious that blowing up images of dubious quality, with compression artifacts, with unknown white balance and so on, yields more problems than answers. I just wanted to remind you all about that.

 

[turbo]

Tough job Borek. Thanks.

 

[MadderDoc]

<..>blowing up images of dubious quality, with compression artifacts, with unknown white balance and so on, yields more problems than answers. I just wanted to remind you all about that.

Do you want us to stop looking at photos and videos and discussing what we see, such as to not cause any more of these 'problems'??

 

[Astronuc]

Do you want us to stop looking at photos and videos and discussing what we see, such as to not cause any more of these 'problems'??

If a photo is analyzed on a sound technical basis, then there is no problem. If a photo is analyzed with some wild speculation, then besides violating the guidelines, it is just a waste of space and our time.

The intent of the thread is for thoughtful discussion and sound technical content, not spurious or specious speculation. The failures of TEPCO are self-evident - they blew it big time - and all criticism (or disparagement in some cases) is not going to change the past. All we can do is learn and move on.

I would like those posting to provide good quality content with a sound technical basis, partly because there appear to folks in Japan looking for answers that are not forthcoming from sources in Japan, and secondly, the thoughtful commentary and sound technical basis is what sets PF apart from the noise out there on the internet.

 

[mikefj40]

For direct conversion of dose from a radioisotope see FGR 11, 12
http://www.epa.gov/radiation/federal/techdocs.htm

Thanks NUCENG. Unfortunately the EPA link is broken.

 

[Astronuc]

Thanks NUCENG. Unfortunately the EPA link is broken.

Link is fixed. It should be .html, rather than .htm

 

[MadderDoc]

If a photo is analyzed on a sound technical basis, then there is no problem. If a photo is analyzed with some wild speculation, then besides violating the guidelines, it is just a waste of space and our time.

Yes of course, one should be completely unreasonable not to agree with that. Thanks for the clarification.

 

[MadderDoc]

What do they mean by reactor building "basement"? Are they referring to the excavated space where the torus is located underground? Are there additional subsurface rooms or spaces?

I'd rather not speculate what they mean by the singular 'basement', but I have seen Tepco use the expression 'second basement floor' in some of their releases relating to unit 1. This would imply that in the eyes of Tepco there is in that reactor building at least two basement floors.

 

[mikefj40]

Link is fixed. It should be .html, rather than .htm

"Limiting Values of Radionuclide Intake and Air Concentration and Dose Conversion Factors for Ingestion, Inhalation and Submersion" is interesting in itself but doesn't answer the question of which isotopes are associated with each energy band on the RADNET graph. http://www.epa.gov/radiation/rert/radnet-reno-bg.html

Is there a better thread for this topic?

 

[swl]

...yet just before the 1st explosion and between the 1st and 2nd explosions, the whole complex went practically dead quiet. Any ideas why?

Could the silence be caused by automatic gain control on the sound recording unit?

 

[ernal_student]

I would like to see a proper english translation of http://www.asahi.com/special/10005/TKY201105120706.html

By what I can make out it discusses un-published internal reports and documents by TEPCO that asahi claim now to have in their possession, more than 100 pages listing many parameters, trends, work groups etc. These documents reveal that on 13th March high radioactivity in or around Unit 3 were measured and observation of steam with high probability of hydrogen escaping into the building. (Unit 3 exploded on the 14th a day later)

That is correct. Let me translate those important points here:
"High radiation, not reported by TEPCO - Reactor 3, understanding the "before" of the hydrogen explosion" (This is the headline: it is not proper English, but I hesitate to smooth it out because that might give a twist to the meaning that is not intended)
"[...] inspite of having a picture of high radiation the day before [the explosion], [the data] was not made public."
"[This] has been confirmed from internal TEPCO documents."
"Asahi Newspaper has obtained documents covering the period from April 11 to April 30, a total of about 100 pages."
"concerning reactor 3, since the 13th high radiation data in the reactor building and likelihood of hydrogen buildup [are being/have been] described/mentioned/recorded"

 

[rowmag]

That is correct. Let me translate those important points here:
"High radiation, not reported by TEPCO - Reactor 3, understanding the "before" of the hydrogen explosion" (This is the headline: it is not proper English, but I hesitate to smooth it out because that might give a twist to the meaning that is not intended)
"[...] inspite of having a picture of high radiation the day before [the explosion], [the data] was not made public."
"[This] has been confirmed from internal TEPCO documents."
"Asahi Newspaper has obtained documents covering the period from April 11 to April 30, a total of about 100 pages."
"concerning reactor 3, since the 13th high radiation data in the reactor building and likelihood of hydrogen buildup [are being/have been] described/mentioned/recorded"

See also my post with a few highlights from those TEPCO documents:

Ok, here is some information you may be interested in. Apparently TEPCO has released some previously-unreleased internal notes on what was happening in the early days. Fascinating reading, published in today's Asahi Shimbun (paper edition). A couple highlights (bolding mine):

"3/12 10:17 Unit 1 venting starts." Has to be done manually, because can't get electricity working in time. One worker takes over 100 mSv in the operation.

"3/12 11:31 Unit 1 water level drops to 1 m below top of fuel."

Followed by some confusion about whether the venting actually worked or not, then...

"3/12 15:36 Sound of explosion at Unit 1"

"3/12 15:45 1 mSv/h measured at 1st floor of seismic bunker, 180 micro-Sv/h inside, several people injured."

"3/12 18:30 0.07 micro-Sv/h neutrons confirmed between North Gate and West Gate (possibility of criticality accident)"

Also, they were planning to open the blow-out panel on Unit 2, but then discovered that it had already happened by itself.

Would be interesting to find the whole thing. Not posted on Asahi website that I see.

Add: Someone has posted a photo of the story printed in the paper:
http://www.geocities.jp/swingi70/_gl_images_/P1020249toudenn.jpg

(Note: my bolding was to highlight things PietKuip might have been interested in. That post was in reply to one of his.)

 

[NUCENG]

"Limiting Values of Radionuclide Intake and Air Concentration and Dose Conversion Factors for Ingestion, Inhalation and Submersion" is interesting in itself but doesn't answer the question of which isotopes are associated with each energy band on the RADNET graph. http://www.epa.gov/radiation/rert/radnet-reno-bg.html

Is there a better thread for this topic?

Depending on energy state each isotope decay produces a beta particle with a variable kinetic energy and discrete photon energy releases from the decay energy to the ground state. The different photon energy possibilities are listed in the nuclide table. Other types of decays are also listed in the nuclide table with a description of the energy levels. just click on the decay type and it will give you the decay energy diagrams.

http://atom.kaeri.re.kr/index.html

 

[ernal_student]

Apparently TEPCO has released some previously-unreleased internal notes on what was happening in the early days.

The only (perhaps in this context irrelevant) unclear point may be to what extent the documents have been "released" or whether they have been "obtained" in other ways. The wording of the related passages in the Asahi Newspaper article make me think that the second interpretation would be justified.

 

[rowmag]

The only (perhaps in this context irrelevant) unclear point may be to what extent the documents have been "released" or whether they have been "obtained" in other ways. The wording of the related passages in the Asahi Newspaper article make me think that the second interpretation would be justified.

Good point. I didn't read the front-page article carefully, just dove straight into the juicy bits.

I see it mentions that a TEPCO PR guy now says they "want to present an organized summary" at some point. I think the raw real-time notes are likely to be more informative, though. They let us know what they were thinking at the time, rather than what they think now (which may still not be correct). And if they edit it now, they are likely to leave out details that they currently think are irrelevant or mistaken, but which at some later date may prove significant after all.

 

[Azby]

It looks like TEPCO is moving forward with it's plan to cover Unit 1 in a steel frame covered with polyethelene sheets. This news item doesn't give an expected date of completion, but I seem to recall September being bandied about previously.

http://www3.nhk.or.jp/daily/english/14_02.html
http://english.kyodonews.jp/photos/2011/05/90962.html

Also a news item reporting that the NISA says there's (probably?) no need to fill unit 1 RPV with water.

http://www3.nhk.or.jp/daily/english/13_26.html

 

[Jorge Stolfi]

PS: The big chunk leaves a trail of dust when falling, I think that's one reason I think it might be something like concrete.

When unit #4 exploded, most of the roof's concrete (or some similar material) was apparently lifted as a unit, and then fell at an angle into the roof steelwork near the north wall. Part of it is still sticking out of the roof. The part that is below the roof can be glimpsed in this photo

http://www.flickr.com/photos/xtcbz/5705937712/in/set-72157626687253144

It is the dark grey "drape" in the background. As others have observed, the "groves" or "folds" visible on that thing are probably the impressions of metal roof panels that supported it.

Seems possible that some of the large objects that were lifted by the explosion of #3 may have been similar to this sheet.

 

[StrangeBeauty]

FYI 6.2 quake not that far away (but 37.6 km (23.4 miles) deep).

http://earthquake.usgs.gov/earthquakes/recenteqsww/Quakes/usc0003etn.php#details

Should give things a least a bit of jiggle there.

 

[swl]

FYI 6.2 quake not that far away (but 37.6 km (23.4 miles) deep).

http://earthquake.usgs.gov/earthquakes/recenteqsww/Quakes/usc0003etn.php#details

Should give things a least a bit of jiggle there.

It was rated at Magnitude 5.7 and Shindo 4 near the plant.

200 kilometers south of the plant, my house and computer desk were shaking audibly but gently.

 

[jlduh]

I would like to see a proper english translation of http://www.asahi.com/special/10005/TKY201105120706.html

By what I can make out it discusses un-published internal reports and documents by TEPCO that asahi claim now to have in their possession, more than 100 pages listing many parameters, trends, work groups etc. These documents reveal that on 13th March high radioactivity in or around Unit 3 were measured and observation of steam with high probability of hydrogen escaping into the building. (Unit 3 exploded on the 14th a day later)

If my interpretation of the machine translation is true, then Tepco have not only leaks in reactors.

Well, in my opinion, Tepco knows much more than us about what happened in their reactors. A probable way through which we will get these infos will be some wikileaks or equivalent distribution...

Don't expect this nuke industry to reveal all critical infos to stupid citizens like us, that's not the common culture in place there. We could be scared, or even angry. Just don't tell em...

But for sure, leaks will come...

 

[rowmag]

It was rated at Magnitude 5.7 and Shindo 4 near the plant.

Shindo 4 shouldn't do much.

 

[etudiant]

Should there not be more recognition of the role of the salt in the reactors?
There were estimates for the volume of salt left behind in the reactors from the emergency cooling, it was appreciable relative to the overall RPV volume.
So is it possible the fuel pellets freed up by the loss of the cladding would not collect at the bottom of the reactor, but rather be caught in the salt, like raisins in a cake. That would prevent the fuel from coalescing and overheating, which might explain the low temperature at the bottom of reactor 1.
Is this a plausible possibility or is there some obvious fact that makes this an invalid idea?

 

[razzz]

When unit #4 exploded, most of the roof's concrete (or some similar material) was apparently lifted as a unit, and then fell at an angle into the roof steelwork near the north wall. Part of it is still sticking out of the roof. The part that is below the roof can be glimpsed in this photo

http://www.flickr.com/photos/xtcbz/5705937712/in/set-72157626687253144

It is the dark grey "drape" in the background. As others have observed, the "groves" or "folds" visible on that thing are probably the impressions of metal roof panels that supported it.

Seems possible that some of the large objects that were lifted by the explosion of #3 may have been similar to this sheet.

These roof panels that are long and narrow and overlapping or interlocking when attached to the joists and ribbing that make up the roof appear to my eye to be made to scatter to relieve pressure whether there is lightweight concrete poured over them then roofing material applied or some other type of roofing (system) to complete the roof.

Unit 4 looks like the blast (type??) came from the lower floors so didn't disengage the entire roof like a 'normal' hydrogen explosion would and even forced the parapet and its associated pivoting wall inward during the blast just pushing or sliding the roof section that remained inward until it folded the framework. Either that or the forces at work are/were pulling down on a weaken structure i.e. pool's dead weight...I don't know and neither do they.

 

[NUCENG]

I'd rather not speculate what they mean by the singular 'basement', but I have seen Tepco use the expression 'second basement floor' in some of their releases relating to unit 1. This would imply that in the eyes of Tepco there is in that reactor building at least two basement floors.

The ground level floor is the area where the scram headers are located. Below ground level is the torus room and corner rooms where RHR and Core Spray system pumps are located. In BWR4s the HPCI and RCIC systems may also be on this level. There is a mezzanine level in the corner rooms that may be what is being referenced.

 

[jim hardy]

Rowmag

that timespan you mention is interesting .. there was something going on not long after they started seawater injection but I've never been able to tie times together.

There's this article, probably you guys saw it too but for refresher:

"""Neutron beam observed 13 times at crippled Fukushima nuke plant

TOKYO, March 23, Kyodo

Tokyo Electric Power Co. said Wednesday it has observed a neutron beam, a kind of radioactive ray, 13 times on the premises of the Fukushima Daiichi nuclear plant after it was crippled by the massive March 11 quake-tsunami disaster.

TEPCO, the operator of the nuclear plant, said the neutron beam measured about 1.5 kilometers southwest of the plant's No. 1 and 2 reactors over three days from March 13 and is equivalent to 0.01 to 0.02 microsieverts per hour and that this is not a dangerous level.

The utility firm said it will measure uranium and plutonium, which could emit a neutron beam, as well.

In the 1999 criticality accident at a nuclear fuel processing plant run by JCO Co. in Tokaimura, Ibaraki Prefecture, uranium broke apart continually in nuclear fission, causing a massive amount of neutron beams.

In the latest case at the Fukushima Daiichi nuclear plant, such a criticality accident has yet to happen.

But the measured neutron beam may be evidence that uranium and plutonium leaked from the plant's nuclear reactors and spent nuclear fuels have discharged a small amount of neutron beams through nuclear fission.

==Kyodo""

http://english.kyodonews.jp/news/2011/03/80539.html

We got somebody to translate from Japanese newspaper and "beam" meant slight radiation as in miniscule rays, not intense beam as in a searchlight.

At the time i attributed it to some unlucky plant guy walking around with contaminated shoes and passing by the monitors.
Will stay tuned to your board here.

 

[rowmag]

Should there not be more recognition of the role of the salt in the reactors?
There were estimates for the volume of salt left behind in the reactors from the emergency cooling, it was appreciable relative to the overall RPV volume.
So is it possible the fuel pellets freed up by the loss of the cladding would not collect at the bottom of the reactor, but rather be caught in the salt, like raisins in a cake. That would prevent the fuel from coalescing and overheating, which might explain the low temperature at the bottom of reactor 1.
Is this a plausible possibility or is there some obvious fact that makes this an invalid idea?

The cores were exposed by between 1 m and 1.6 m for 7 hours before they started pumping in borated seawater at 20:45 on the 12th. So a good fraction of the fuel pellets may have fallen to the bottom of the RPV before salt could accumulate. But maybe the later ones could be diluted like that, if the water gauge was correct (for a while -- we know at some point it went bad) and it didn't all go empty right away?

 

[rowmag]

Rowmag

that timespan you mention is interesting .. there was something going on not long after they started seawater injection but I've never been able to tie times together.

There's this article, probably you guys saw it too but for refresher:

http://english.kyodonews.jp/news/2011/03/80539.html

We got somebody to translate from Japanese newspaper and "beam" meant slight radiation as in miniscule rays, not intense beam as in a searchlight.

At the time i attributed it to some unlucky plant guy walking around with contaminated shoes and passing by the monitors.
Will stay tuned to your board here.

Not clear yet what it really was. These are real-time notes or log entries from the height of the crisis, so I doubt TEPCO had much chance to analyze it at the time. Somebody probably just said, "Neutrons? Hmm, better consider the possibility of criticality," and we don't have notes from after that (in the paper, at least) to explain what they may have found out or figured out about it later.

The main thing I find interesting about it is that TEPCO themselves had immediately flagged it as a possibility, which makes me inclined to be a little more forgiving of the folks who later jumped on the bad-translation "neutron beams" phrase to come up with the same idea. Fog of war.

If the rest of those leaked notes get published, perhaps someone can piece it all together.

 

[NUCENG]

Thanks NUCENG. Unfortunately the EPA link is broken.

Keep trying. The documents are public domain. If you still can't get to them PM me and I'll upload them.