Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[MadderDoc]

Is a criticality which causes its own end by rearranging the physical proximity of the supporting material still a criticality? even if it only lasts a couple of milliseconds?

I think so. There seems to be nothing in the definition of criticality that implies that the k=1 clause for criticality could not be changed into k>1(supercritical) or k<1 by something rearranging the physical proximity of the supporting material. Cf. a supercriticality might elevate the temperature such as to become critical, or selfdestruct into something subcritical. It would still have been a supercriticality until that happened.

 

[Quim]

It would still have been a supercriticality...

Next question:

Is it possible to calculate the joules of heat produced by the smallest possible self sustaining reaction - stated as Joules per millisecond?

TIA

 

[thehammer2]

I think so. There seems to be nothing in the definition of criticality that implies that the k=1 clause for criticality could not be changed into k>1(supercritical) or k<1 by something rearranging the physical proximity of the supporting material.

snip

Changing a core's surroundings can be of extreme importance. During the Manhattan project, the "demon core" that most people associate with killing Louis Slotin actually killed Harry Daghlian first.

Daghlian was doing experiments on neutron reflectors with the subcritical assembled core. He was stacking tungsten carbide bricks around it in a controlled manner and taking measurements when he accidentally dropped a brick onto the assembly. The brick gave enough reflectivity to the core's surroundings and it went critical and gave Daghlian a massive dose.

This is not to say at all that I think there are suddenly shifts in the surroundings that are making the Fukushima cores critical. This is just to say that when calculating the criticality of a core the surroundings must be considered. During the Manhattan project, if I remember correctly, one of Richard Feynmann's jobs was to maintain safety, including developing protocols for moving materials into and out of areas with consideration of what might be contained in the room next door.

In related news, during the Manhattan Project, these guys worked in the same room with and basically barehanded plutonium bomb cores regularly.

 

[MadderDoc]

Next question:

Is it possible to calculate the joules of heat produced by the smallest possible self sustaining reaction - stated as Joules per millisecond?

TIA

That would come out close to zero, I think. It is indeed a borderline case, but the smallest imaginable critical mass would have consumed fissionable material such as to become subcritical after just one 'neutron generation'.

 

[tsutsuji]

The test of the cesium absorption facility of the water decontaminating system was started with low level contaminated water at 3:45 AM this morning (June 14th). The test of the whole facility will be started on June 16th.

On the other hand, the harbour purifying system is started again with only 30% of the cesium being removed. The presence of oil in the water prevents to reach the expected 60~70%. The flow is 30 tons/hour but more units could be installed.

http://mainichi.jp/select/jiken/news/20110614ddm002040156000c.html
http://www.tv-asahi.co.jp/ann/news/web/html/210614003.html

 

[Quim]

That would come out close to zero, I think. It is indeed a borderline case, but the smallest imaginable critical mass would have consumed fissionable material such as to become subcritical after just one 'neutron generation'.

That sounds more like NUCENG's "subcritical neutron amplification."

If it become subcritical after just one neutron generation how could you consider it self-sustaining?

 

[maddog1964]

You guys do realize that there's a thread which deals specifically with the Unit 3 explosion? How about you talk about that topic over there?

could you please list the link to that thread. ty

 

[MadderDoc]

That sounds more like NUCENG's "subcritical neutron amplification."

If it become subcritical after just one neutron generation how could you consider it self-sustaining?

I did say, this is a borderline case.

 

[Bioengineer01]

@ Bioengineer01


Fine, go and do the exploration... I would suggest you first explore the possibility that there is NO inconsistency in the thermal signatures of the SFP versus the visible surface of water in the reactor vessel.
.

Absolutely agree and I am not wasting any time on conspiracy theories. That is why I am reading the thread and enjoying the discussion and trying to make sense and find an explanation to the apparent inconsistency. I've done myself lots of IR for biological reasons, it is an extremely useful tool, in my post, I was just trying to explain why people are still discussing this. Nothing less, nothing more.

 

[robinson]

http://www.tepco.co.jp/nu/f1-np/camera/index-j.html

While it would be hard to imagine a worse camera set up, even so you can still see the constant steam coming out of the buildings. Is there any plan to do anything to even find out what is happening inside building three?

Like stick some cameras in there? How long do you simply just let a nuclear pile of crap steam away? With out even knowing where the steam is coming from. or what is in it.

 

[Bioengineer01]

I note your tremendous artistic talent in replying. Thank you.

I have always thought of is as ping pong balls and bowling balls. Ping pong balls (neutrons) will bounce off of heavier atoms (bowling balls) without losing energy, but will bounce off of Hydrogen atoms and impart some of their energy to the Hydrogen. I guess eventually they can be turned around.

I read early on that the salt produced by the evaporation of sea water could have a significant effect on this interaction from experts at the NRC that advised Japan to stop the seawater injection. But I never found it in written news, my assumption was that it could help form a crust around the Corium and any cracks or fissures that it may develop and make the process of heat extraction more difficult, but now I wonder if that same crust of salt would not participate in neutron slowdown and reflection. Just a thought, anybody? Can anybody add clarity to this?

 

[MadderDoc]

Absolutely agree and I am not wasting any time on conspiracy theories. That is why I am reading the thread and enjoying the discussion and trying to make sense and find an explanation to the apparent inconsistency. I've done myself lots of IR for biological reasons, it is an extremely useful tool, in my post, I was just trying to explain why people are still discussing this. Nothing less, nothing more.

I agree the heat signature from the reactor well is 'strange'. Generally this signature has had an IR measured temperature close to 30^oC, and this even on early mornings where ambient temperature has been only 0-5^oC.

Naturally under such circumstances we are unlikely to be measuring the temperature of the water surface, but rather the temperature of condensed steam hanging over it. And this would imply that the water surface must be even _warmer_ than 30^oC. I too cannot imagine how water can be kept this warm in the reactor well throughout many days during March and April, with cold nights and never a ray of sunlight hitting it. I certainly would like to know how I can keep the roof of my house cosily warm throughout winter without a considerable heat source underneath it ..

 

[Jorge Stolfi]

If it become subcritical after just one neutron generation how could you consider it self-sustaining?

By that criterion criticality is impossible, since as the fuel is consumed the value of k will decrease until the chain reaction stops.

The k parameter and the critical/subcritical distinctions are drastic simplifications of reality. If you look too closely, the k parameter is not a well-defined quantity, and criticality becomes a fuzzy concept.

On the other hand, note that some chain fissions should occur at a steady rate even if k < 1, and should boost the spontaneous neutron emission rate by the factor 1/(1 - k). For k = 0.8, for example, the total neutron production (spontaneous + fission) should be ~5 times the spontaneous rate. That is "sustained" in the sense that the fission reactions keep happening at the same rate as long as one can consider the composition of the mass constant.

I would guess that even with a boost of x5 or x20 over the spontaneous rate, the heat generated by fission will be negligible compared the normal decay heat of half-used fuel. But what about the radiation hazard?

 

[Pu239]

Conditions in the night are such that it looks steaming every day. My bet is that is mostly a matter of local weather - humidity and temperature changes. Fog clouds are moving in and out of the light, which makes the picture dramatic.

I have looked at the live feed at several occasions, never longer than just a few minutes, usually after someone raises alarm - and each time it looks the same to me.

Edit: it occurred to me that compression artifacts look like a dynamic smoke/steam cloud as well. Thats typical in low light conditions - dark, large spots with slight color gradient look like moving even if the image is still. It can look as a dynamic steam motion, even if the real situation is quite stable.

I gather nobody actually saw the large release of steam - very large - last night. We know it is steaming every day but this was far above the normal. Definitely not fog or clouds. This was a large, fast moving vertical plume of smoke coming directly from #4 - top of roof. It eventually billowed out and clouded everything - then, at that stage it was mistaken by many observers for fog or rolling cloud. Not. (Think of looking at a smoking chimney in cloudy or possibly foggy conditions - smoke is grey, fog is white).

Just before that everything was clear (but dark) with the usual lit-up reactors. The plume was studied carefully [by myself and others] as it grew from a whisp at the top of #4 to a massive all-engulfing cloud. Emergency vehicles arrived soon after, with flashing lights.

Have heard nothing since.

TEPCO LIVE CAMERA

http://www.tepco.co.jp/en/nu/f1-np/camera/index-e.html

 

[StrangeBeauty]

I just saw a white and black spotted DOG walk past the TEPCO webcam , it stopped and even looked into the cam for a sec !...

Could it be that the white spots are neutron reflectors and the black spots neutron absorbers creating a moderating field for recriticality?!

I did say, this is a borderline case.

Yes! It must have been a borderline collie!








Apologies for the physics humor. ;)

 

[robinson]

http://flyingcuttlefish.wordpress.c...-fire-right-now-live-cam-shows-lots-of-smoke/

Second video shows a time lapse where the steam.smoke is obvious. Not from last night, but still, this is a regular event at night.

 

[StrangeBeauty]

I gather nobody actually saw the large release of steam - very large - last night...

A lovely sequence of a marine fog bank rolling in with lots of video compression artifacts thrown in.

http://flyingcuttlefish.wordpress.c...-fire-right-now-live-cam-shows-lots-of-smoke/

Second video shows a time lapse where the steam.smoke is obvious. Not from last night, but still, this is a regular event at night.

Yes lots of "steam" whenever the dewpoint gets close to the air temperature (as it often does at night).

I realize that something (more) horrible could happen with SPF4 or any of the other units, but these frequent steam displays are not it. The building is not on fire. The building is not smoking. At least not now or all the other times that such has been claimed.

This is just the same, constant steaming of the SPF made more visible by local weather conditions. I am not saying to drop vigilance in observing, but I think we're getting way too many false alarms now. I imagine that most of our esteemed thread readers and participants are just skipping over the constant stream of "fire/smoke at SPF4/#3" posts and will skip over a legitimate problem if it should arise.

 

[Morbius]

The k parameter and the critical/subcritical distinctions are drastic simplifications of reality. If you look too closely, the k parameter is not a well-defined quantity, and criticality becomes a fuzzy concept.

Jorge,

Yes - it's fuzzy when you're just hand-waving about the definition.

However, in terms of the mathematical definition of "k", the k parameter is very well defined. It is as well defined as any other eigenvalue of an eigenvalue equation which is what the critical problem really is.

Dr. Gregory Greenman

 

[robinson]

Yes lots of "steam" whenever the dewpoint gets close to the air temperature (as it often does at night).

No, when the dewpoint is right you can see it, but there is always steam/water vapor coming out of all four buildings. 24/7

If only there was a way to measure what is in it. It could give a clue as to what is happening.

 

[StrangeBeauty]

No, when the dewpoint is right you can see it, but there is always steam/water vapor coming out of all four buildings. 24/7

Of course it's 24/7. I meant it becomes more visible under those conditions and that's when people have been "crying wolf" about fires/smoke.

If only there was a way to measure what is in it. It could give a clue as to what is happening.

I completely agree with that. The compressed video is just too misleading/imprecise to tell anything definitive.

 

[Pu239]

A lovely sequence of a marine fog bank rolling in with lots of video compression artifacts thrown in.

Yes lots of "steam" whenever the dewpoint gets close to the air temperature (as it often does at night).

I realize that something (more) horrible could happen with SPF4 or any of the other units, but these frequent steam displays are not it. The building is not on fire. The building is not smoking. At least not now or all the other times that such has been claimed.

This is just the same, constant steaming of the SPF made more visible by local weather conditions. I am not saying to drop vigilance in observing, but I think we're getting way too many false alarms now. I imagine that most of our esteemed thread readers and participants are just skipping over the constant stream of "fire/smoke at SPF4/#3" posts and will skip over a legitimate problem if it should arise.

Have a look at the following videos. I'll drop this topic very shortly, but I do want some kind of corroboration, given that this board's topic is: Physics Forums > Engineering > Nuclear Engineering > Japan Earthquake: nuclear plants.

This was not

- a false alarm
- one of the many false alarms
- one of the many frequent steam displays

It was a *massive* and significant steam/vapour display that started with a clearly visible vertical emission of vapour, then blotted out all the other reactors - starting around 2:15 in the first video below. Also look at the 10 second mark in the second video. They look very much like explosions to me:

Here's the video:
2011.06.14 00:00-01:00 / 福島原発ライブカメラ (Live Fukushima Nuclear Plant Cam)
http://www.youtube.com/fuku1live#p/u/9/k-EDceWFovc

2011.06.14 01:00-02:00 / 福島原発ライブカメラ (Live Fukushima Nuclear Plant Cam)
http://www.youtube.com/fuku1live#p/u/8/fg8yGBhoLxU

 

[Pu239]

You'll notice that actually #3 and #4 are steaming in those videos.

 

[biggerten]

I think you saw three things -

1) SFP 4 steaming.
2) Followed by a fog bank rolling in.
3) The arrival of a wide load caravan with one of those oversized tanks they're bringing in at the rate of 4 or 6 per day.

 

[Pu239]

No fog that day. We checked the weather - realtime. Conditions were cloudy.

Unless fog starts inland from the top of a building and rolls out to sea?

Also, you'll see two vertical plumes - one from #3 and one from #4.

You'll also see flashes of light within those plumes - but, have to watch all of the video.

You'll also notice an explosion 10 sec in on the 2nd video from #4, or the shared spent fuel area.

I see no caravan. Or gypsies.

Time to drop this topic I guess.

 

[quark42]

I live along the central California coast. I'm very acquainted with the behavior of fog and lights at night. I also have years of photography experience (an avocation along with an engineering vocation). Also, being a pilot with com/inst ratings, I have a very good understanding of what happens when the temp/dew point spread narrows and its affect on water vapor visibility, i.e. clouds.

My opinion on the "visible vertical emission of vapor" is an illusion caused by the lighting of the exhaust tower behind forming fog. The tower is exactly behind where the column of vapor "appears".

Just my two cents worth, anyway.

It does, however, bare repeating the importance of checking the temp/dewpoint spread when considering the possibility of anomalous emmisions from the reactor buildings.

 

[Pu239]

I'm well aware of the tower and the optical illusions thereof. Yes, the vertical tower can be mistaken for a vertical plume of smoke, but this isn't what I'm talking about at all.

Take another look at your "fog". This is the third hour of the event:

2011.06.14 03:00-04:00 / 福島原発ライブカメラ (Live Fukushima Nuclear Plant Cam)
http://www.youtube.com/fuku1live#p/u/6/vThV0k3IZEc

I'm also interested in the explosions within that "fog". They occur in several places, e.g. 10 sec in on hour 01:00-02:00.

Otherwise, it seems I'm beating a dead horse here, no takers. Over to video forensics I guess.

 

[robinson]

Fog does not start up high like we see in the videos. It also doesn't just come in at one location. If it was fog, which we can see in other videos, it looks completely different than those events.

 

[quark42]

Well, I do see puffs of coming out of the reactor buildings, but they don't look to me like explosions. Just warm water vapor. But like you say, the ex-horse has been well beaten.

 

[Jorge Stolfi]

Jorge, Yes - it's fuzzy when you're just hand-waving about the definition.

However, in terms of the mathematical definition of "k", the k parameter is very well defined. It is as well defined as any other eigenvalue of an eigenvalue equation which is what the critical problem really is.

The k parameter of the differential equation is defined with matematical precision of course.

The drastic simplification is in the modeling of the 3D physical situation (with spatially variable distributions of materials and neutrons, multiple neutron energies and directions, compressibility and material flow, etc.) by that single ordinary first-order single-valued linear differential equation. The fuzziness surfaces when one tries to explain what that single variable stands for. All the best,

 

[Jorge Stolfi]

2011.06.14 00:00-01:00 / 福島原発ライブカメラ (Live Fukushima Nuclear Plant Cam)
http://www.youtube.com/fuku1live#p/u/9/k-EDceWFovc

2011.06.14 01:00-02:00 / 福島原発ライブカメラ (Live Fukushima Nuclear Plant Cam)
http://www.youtube.com/fuku1live#p/u/8/fg8yGBhoLxU

2011.06.14 03:00-04:00 / 福島原発ライブカメラ (Live Fukushima Nuclear Plant Cam)
http://www.youtube.com/fuku1live#p/u/6/vThV0k3IZEc

My two cents: it is tantalizing, but not quite convincing.

I believe that much of the shivering and "boiling" motion we see in the large "steam" cloud, for example on the North side of #2, is just camera noise (which gets more severe in the darkest part of the night, when the camera gain gets automatically pushed all the way up); compounded by MPEG compression artifacts (curs'd be he who invented that format!). Notice that the shivering disappears completely when sunlight begings to increase again at the end of the third video.

My brain cannot easily filter out that shivering noise, but I suspect that without it the big cloud would be largely static, and the movie would look very much like an ordinary fog bank gradually coming in from the sea and engulfing the steam plumes from the reactors. Note that he fog would be invisible until it gets above the reactors, where it becomes lighted by the spotlights.

As for the "explosion" at 03:10, its location does not match any of the reactors. It looks like someone swung the beam of a spotlight (or a strong headlight) acoss the webcam.

 

[Pu239]

A+.

You got it.

 

[Pu239]

Fog does not start up high like we see in the videos. It also doesn't just come in at one location. If it was fog, which we can see in other videos, it looks completely different than those events.

A+, with honours.

:D

 

[clancy688]

could you please list the link to that thread. ty

https://www.physicsforums.com/showthread.php?t=505630

----

Why don't you guys make a "Where's Wally?" thread about Unit 4. There you can point out what you're seeing or not seeing or what you think you're seeing at Unit 4 all you like.

 

[Borek]

Take another look at your "fog". This is the third hour of the event:

Note one important thing: in all cases it starts with a buildings steaming (they do it all the time) but then they are covered with a huge cloud of fog that comes from the outside - it is not that buildings "puff" a large cloud from the inside, cloud appears first high above the buildings and then covers them as it moves in the direction of the land (obviously it comes from the sea).

And I agree with Jorge that those flashes are just a light scattering by the fog - could be something like flashlight or headlight, but some look just like cloud of fog entering the beam from the street lamp or reflector. You don't see the beam, so you think the place is dark, but when fog comes in the beam it becomes source of scattered light - and it looks like if some light source appeared out of nothing.

In the place where I live fog is nothing unusual - and knowing how it looks here, I don't see anything unusual on these videos.

 

[SteveElbows]

The webcam did look a bit more interesting than usual during this time period, but when all is said and done it looked extremely likely to be a weather event to me. There was rain in the area around this time, according to online rain radar, and in later footage we can actually see some water in the foreground drying up over time.

As for 'explosions', most nights there are a variety of flashes, some of which seem most likely to be caused by vehicle headlights.

According to information on planned operations, there would have been unit 4 pool spraying for many hours during the afternoon and evening before this footage.

I suppose we have to be careful not to become complacent, but at this point its all been false alarms and a failure to take weather into account.