Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[Samy24]

That's my point.

Maybe you misunderstood me. I believe they did not measure at that time. And even if they did, i do not believe they would have published it.

 

[ascot317]

Maybe you misunderstood me. I believe they did not measure at that time. And even if they did, i do not believe they would have published it.

I'm not sure, aren't there quite a few automated counters on site? Or, aren't there any, or, since they didn't have offsite power at that time, they weren't working?

I'm not so sure, it's been a while.

 

[htf]

It's a bit confusing. Please, can somebody explain it to me that what's the difference between a reactor running on several dozen times higher power than the design parameters (which , of course, will generate an explosion) and a fission generated explosion?

Do we have a clear definition of a fission generated explosion?

The explosion of Chernobyl #4 was attributed to a hydrogen explosion. The hydrogen was generated by the overheated reactor. When they say it was "fission generated explosion" then this would mean to me that there was no hydrogen explosion. The energy came solely from an an sudden increase of the fission rate.

 

[Samy24]

I'm not sure, aren't there quite a few automated counters on site? Or, aren't there any, or, since they didn't have offsite power at that time, they weren't working?

I'm not so sure, it's been a while.

To my memory they had to check readings at the plant by "hand". Workers had to go to measuring points and look at the readings. the measurement of neutron flux ist not so easy but was indeed reported one mile away. But I do not know the point in time of that measure.

 

[default.user]

Maybe you misunderstood me. I believe they did not measure at that time. And even if they did, i do not believe they would have published it.

http://www.businessweek.com/news/2011-03-31/tepco-workers-threatened-by-heat-bursts-sea-radiation-rises.html

 

[Samy24]

http://www.businessweek.com/news/2011-03-31/tepco-workers-threatened-by-heat-bursts-sea-radiation-rises.html

What should this "light" proof? The explosion was at daylight.

 

[clancy688]

It's a bit confusing. Please, can somebody explain it to me that what's the difference between a reactor running on several dozen times higher power than the design parameters (which , of course, will generate an explosion) and a fission generated explosion?

I'd say there is no difference. Except for the generated power. A nuclear reactor uses fission to generate heat which's used to power a turbine.
A nuclear weapon uses fission to generate massive amounts of heat to forge a devastating shock wave.
It's the same reaction. It's the same output. Only the nuclear weapon uses the reaction on a far bigger scale... more fission, more neutrons, more heat, more energy. A lot more energy.

The explosion of Chernobyl #4 was attributed to a hydrogen explosion. The hydrogen was generated by the overheated reactor. When they say it was "fission generated explosion" then this would mean to me that there was no hydrogen explosion. The energy came solely from an an sudden increase of the fission rate.

I'm not so sure about the hydrogen explosion. Wikipedia states that nobody is sure what caused the big explosion. There's only the fact that the reactor went to 30 GWt and then KABOOM.
I don't think that a hydrogen explosion is very likely. I'm not a chemist, but a hydrogen explosion would mean, that the reactor must have generated enough hydrogen to destroy the building and lift the 1000 ton heavy reactor cap upwards in just a few seconds - because that's how long it took Chernobyl to change from a perfect healthy reactor into a pile of rubble.
And I don't think that such a fast reaction would be possible.Edit:
@Samy24 - Cherenkov radiation, water glows blue when radiation passes through it. But I don't think it proves anything. First, the images were enhanced to show the spot. I couldn't detect anything. And I don't think that enhancing a crappy webcam pic will show us anything. Second, it seems to be normal for SFPs, even without criticality.

 

[default.user]

What should this "light" proof? The explosion was at daylight.

It should be a proof for neutron radiation.

Accordingly, there had been partial criticality.

The image was sharpened and subsequently processed..

http://www.sueddeutsche.de/wissen/japan-nachbeben-der-staerke--1.1075927

A german newspaper. A good one. I translate with the google translator:

The operating company Tepco said on Wednesday that it had in 1.5 kilometers away from the reactor neutron beams measured a total of 13 times on the site, indicating a withdrawal of the radioactive material

http://en.wikipedia.org/wiki/Neutron_radiation#Sources

Neutrons may be emitted from nuclear fusion or nuclear fission, or from any number of different nuclear reactions such as from radioactive decay or reactions from particle interactions (such as from cosmic rays or particle accelerators). Large neutron sources are rare, and are usually limited to large-sized devices like nuclear reactors or particle accelerators (such as the Spallation Neutron Source).

So we still have high temperatures in the reactors.
The neutron beams were visible until Tuesday of this week.

i wrote it with the google translator.

Sorry

 

[TCups]

Question for Astronuc et al:

As I think about this, if the shape and depth of the SFP could focus the blast into a vertical mushroom, then the shape and depth of the SFP, particularly if there were water covering all or part of the spent fuel would also tend to focus the force of an explosion toward the bottom of the SFP. Might it be that either a blast from the primary containment or a blast from hydrogen + air in the service floor, "amplified" by the geometry of the SFP and efficiently transmitted by water in the SFP did indeed exert a hydrostatic, crushing force on the spent fuel assemblies?

This wouldn't be a shaped HE charge crushing two subcritical hemispheres of plutonium, but on a much larger scale, a large explosion crushing several tons of spent fuel racks -- at least in theory, the hypothesis of a sudden criticality in the SFP doesn't seem too far fetched to a lay person.

 

[Samy24]

Edit:
@Samy24 - Cherenkov radiation, water glows blue when radiation passes through it. But I don't think it proves anything. First, the images were enhanced to show the spot. I couldn't detect anything. And I don't think that enhancing a crappy webcam pic will show us anything. Second, it seems to be normal for SFPs, even without criticality.

I was responding because we talked about the posibility that the explosion on unit 3 was driven also by fission. The explosion was at daylight so the Cherenkov light (if it is) has nothing to do with it. Someone asked why they did not detect gamma and neutron bursts at the time of the explosion and so default.user kicked in.

 

[PietKuip]

I'd say there is no difference. Except for the generated power. A nuclear reactor uses fission to generate heat which's used to power a turbine.
A nuclear weapon uses fission to generate massive amounts of heat to forge a devastating shock wave.
It's the same reaction. It's the same output. Only the nuclear weapon uses the reaction on a far bigger scale... more fission, more neutrons, more heat, more energy. A lot more energy.

In a real nuclear bomb, the chain reaction occurs by fast neutrons. One needs highly enriched uranium for that, or plutonium.

In an ordinary nuclear reactor, the chain reaction proceeds because of fission induced by thermal ("slow") neutrons. One wants to keep the criticality factor below 1.006. This ensures that "delayed" neutrons are necessarry to keep the chain reaction going, so that it can be controlled by manipulating control rods.

But when k > 1.006, one has prompt criticality, and rapid exponential growth of power, too fast for control rods to limit. It is only limited by the moderator dissappearing and/or the critical mass being dispersed by the heat generated. A nuclear "fizzle" by slow neutrons, but much more violent than an Oklo-type of criticality.

 

[Samy24]

Question for Astronuc et al:

As I think about this, if the shape and depth of the SFP could focus the blast into a vertical mushroom, then the shape and depth of the SFP, particularly if there were water covering all or part of the spent fuel would also tend to focus the force of an explosion toward the bottom of the SFP. Might it be that either a blast from the primary containment or a blast from hydrogen + air in the service floor, "amplified" by the geometry of the SFP and efficiently transmitted by water in the SFP did indeed exert a hydrostatic, crushing force on the spent fuel assemblies?

This wouldn't be a shaped HE charge crushing two subcritical hemispheres of plutonium, but on a much larger scale, a large explosion crushing several tons of spent fuel racks -- at least in theory, the hypothesis of a sudden criticality in the SFP doesn't seem too far fetched to a lay person.

So I see that too. Maybe it's not very likely. But to simply say it is impossible is also not correct. No one has tried this with more the 100 tons of fuel before. (This test would be to expensive ;)

 

[default.user]

My idea is:

The corium is much larger than we think. This means that the meltdown is far greater, indicating a TEPCO.

The corium has enough mass to trigger a partial criticality. So that the temperature in the reactor increases. The benefit of a further meltdown. This means that more fuel enters the reactor bottom. This leads to continuous partial criticality.
For this I need not have studied physics. The moderator boron is not in the core of the Corium 50 tons.

http://en.wikipedia.org/wiki/Corium_(nuclear_reactor)

 

[Jorge Stolfi]

I admit, this video stutters distractingly. However, the keyframes are actually pretty good, and they depicture objects we have not had a good view of before, from a so far unseen angle, and with a resolution down to a few centimeters at its best.

I do not understand the point of making videos of what is basically a static target. I would much prefer a few high-resolution photos, from well-planned vantage points (like those invaluable pics taken by the Air Photo Service drone last month) than thousands of low-resolution frames with lots of distracting MPEG artifacts.

 

[biffvernon]

Wouldn't we be seeing a neutron and gamma spike at the moment of the explosion then?

Maybe there was a spike:

On two occasions radiation levels at Dai-Ichi reached 1 sievert an hour. Thirty minutes of exposure to that dose would trigger nausea. Contamination for four hours might lead to death within four months, according to the U.S. Environmental Protection Agency.

Five kilometers away at the nuclear safety agency’s offsite center, Yokota said radiation levels set off a constant warning ping at detectors in the office, so he put on his DuPont Co. Tyvek protective suit and a face mask.

From http://www.bloomberg.com/news/2011-04-25/japan-s-terrifying-day-saw-unprecedented-exposed-fuel-rods.html

 

[elektrownik]

About explosions, I am not expert, I write only on base of observations: #1 explosion, big pressure in reactor building from venting then small, centered hydrogen explosion. #3 explosion, yest we can see it on video, first fireball from SFP location, then big explosion going up, but I don't think that it was from recriticality in SFP, I think that first explosion in SFP damaged drywell and reactor vessel so there was big release of pressure and maybe hydrogen explosion. If there would be so big explosion from SFP then there would be more very hight radioactive pieces of fuel rods, but they found only 300 and 900 mSv/h mayby from reactor cap... Also the big "up" explosion appear to be from center of building/core location not from sfp like fireball...

 

[ascot317]

[...]If there would be so big explosion from SFP then there would be more very hight radioactive pieces of fuel rods, but they found only 300 and 900 mSv/h mayby from reactor cap... Also the big "up" explosion appear to be from center of building/core location not from sfp like fireball...

Yeah, although they apparently haven't done a complete search of the area yet (otherwise they wouldn't accidently find debris more than a month later).

What puzzles me about a "fuel-fizzle" is, the SFP is in one of the least damaged corner of the building.

Maybe there was a spike:


From http://www.bloomberg.com/news/2011-04-25/japan-s-terrifying-day-saw-unprecedented-exposed-fuel-rods.html

He shuttled between the offsite and the Dai-Ichi bunker. When the No. 3 reactor housing exploded on the morning of March 14, levels inside the bunker jumped as much as 12-fold, he said, checking dates and times in a pocket diary.

"Inside the bunker", yeah, gamma spike.

 

[Rive]

Thanks for the ideas about fission/not fission difference.

About explosion/recriticality: IMHO every explosion were hydrogen explosion and maybe containment damage, but none of them were originated directly from any SFP. It would scatter at least some fuel, and scattered/damaged fuel rods would cause much more serious contamination nearby than the actually observed. It would end in Chernobyl-style radiation zones around the affected unit (with much stronger Uranium and Plutonium presence).

However low scale pulsing recriticality by Tokaimura-style cannot be excluded. But: it cannot be proved too. IMHO.

About the picture of blue flash: fresh spent fuel is glowing even without recriticality, so without further observations it proves nothing. Is the glowing still visible? Has it happened any more times? Any similar observations from satellites, maybe?

 

[elektrownik]

The idea of "nuclear explosion" or I should say massive recricitality is interesting, also in case of Chernobyl and Fukushima. For example we have research reactor in Poland, science many years it was runing on 80% enriched uranium, from the last refuling they change it to 36%, I think that 80% wouldn't be safe in case of accident... 80% is enought for nuclear bomb

 

[Samy24]

The idea of "nuclear explosion" or I should say massive recricitality is interesting, also in case of Chernobyl and Fukushima. For example we have research reactor in Poland, science many years it was runing on 80% enriched uranium, from the last refuling they change it to 20%, I think that 80% wouldn't be safe in case of accident... 80% is enought for nuclear bomb

It is terrible to hear what experiments are done in europe. Who will take the responsibility if something happens? Is this military or private stuff?

 

[elektrownik]

I don't think that fuel was ejected from SFPs. It would give very hight radiation, not 300 or 900mSv, and for example, if there is ~1500 fuel racks in #4 sfp, (or #3) then for example if only 10% fuel would be ejected it would give us 150 fuel racks so they would be everywhere, we could see them on thermal images and also radiation from them would kill workers very fast.

 

[bytepirate]

About the picture of blue flash: fresh spent fuel is glowing even without recriticality, so without further observations it proves nothing. Is the glowing still visible? Has it happened any more times? Any similar observations from satellites, maybe?

the cherenkov light is still visible (a faint blue shadow on the webcam pics).
this is the normal glow of a (outdoor) spent fuel pool. i would worry, if it is NOT visible (that could mean, the pool is dry)

 

[elektrownik]

It is terrible to hear what experiments are done in europe. Who will take the responsibility if something happens? Is this military or private stuff?

The reactor (only one in Poland) is old (from 70s) and it is research reactor, it have small power (30MW) but it generate 80% more neutrons than normal reactor. It is not military or private, it owner is government. Also this reactor is only 30km from Warsaw (capital of Poland)... Good that they change this fuel from 80 to 36%, they fuel is from Russia...
You can see some pictures here: http://iea.cyf.gov.pl/nowa/index.php?option=com_wmtsimpleflashgallery&Itemid=93
And here video:

 

[Rive]

It is terrible to hear what experiments are done in europe. Who will take the responsibility if something happens? Is this military or private stuff?

Low power research and/or training reactors (up to dozen megawatts) are 'common', even in the US. If you google 'TRIGA' or 'TRIGA flash' you can see some really nice vids about them.

80% enrichment is unusual, but such fuels are being withdrawn for now and used only special military or scientific reactors AFAIK.

 

[mikefj40]

the cherenkov light is still visible (a faint blue shadow on the webcam pics).
this is the normal glow of a (outdoor) spent fuel pool. i would worry, if it is NOT visible (that could mean, the pool is dry)

This is from the evening of April 1. Play 00:42 to 00:45 and you'll see the glow in the dark spot. http://www.youtube.com/watch?v=CtgRBpgbZww&feature=related. I believe it's been visible on a few other occasions. Is that the SW corner of #4?

 

[mikefj40]

Evening glow from April 2 - 4: http://www.youtube.com/watch?v=7vhI86uYquc&feature=related

 

[Samy24]

Low power research and/or training reactors (up to dozen megawatts) are 'common', even in the US. If you google 'TRIGA' or 'TRIGA flash' you can see some really nice vids about them.

80% enrichment is unusual, but such fuels are being withdrawn for now and used only special military or scientific reactors AFAIK.

Maybe it is a research breeder reactor? 20% Plutonium and 80 % Uranium is normal. Many countries experiment with this. So it must be safe.

 

[Borek]

It is terrible to hear what experiments are done in europe. Who will take the responsibility if something happens? Is this military or private stuff?

http://www.iea.cyf.gov.pl/index_ang.html

http://www.iea.cyf.gov.pl/historia_ang.html

 

[elektrownik]

Maybe it is a research breeder reactor? 20% Plutonium and 80 % Uranium is normal. Many countries experiment with this. So it must be safe.

No, there is no plutonium, only uranium.

 

[M. Bachmeier]

I hate the sort of headlines such stories generate, talking about 'rising levels'. Without knowing whether the robot(s) visited exactly the same locations at reactor 1 as they did on their first visit, we don't know if anything has risen, or whether the robots just stumbled upon a more contaminated area this time.

Either way its not a good number, but numbers even higher than this would not surprise me as they slowly explore further.

These sorts of numbers are also a reason not to stretch the complaints of PR and coverups too far. In theory there may be plenty we are not being told but they have also released plenty of info that was not good news by any stretch of the imagination. The explosions somewhat reduced the temptation to do a complete and utter coverup, and although I am not overjoyed with the quality of data that is available to us, its a lot more than I might have imagined we would get.

"The explosions somewhat reduced the temptation to do a complete and utter coverup, and although I am not overjoyed with the quality of data that is available to us, its a lot more than I might have imagined we would get."

I don't think a 'cover-up' is the way most Japanese would perceive selective information dissemination. I think that most would either believe, or like to believe that information is controlled in the best interests of workers, people displaced, long term economic factors and the desire not to bring nuclear contamination shame to those exposed.

There are many Japanese who never reported suspected radiological effects upon they're children (Hiroshima, Nagasaki) because of stigma. There are some in Japan who might believe these events to be punishment for arrogance.

If there are errors in the degree of timely reporting of events, it most likely has to do with what (persons in the position of responsibility) feel is the path of least harm. TEPCO has no financial future, so no motive to be irresponsible. Their employees, however, are aware of their future financial difficulties and never forget that almost all have suffered personal loss. If errors did not occur in this situation I would wonder if they (TEPCO personnel) were human.

I make no criticism of you Steve, but thought that we all could apply some perspective to our analysis'. Many errors are made when one faces enemies on multiple fronts...