Talk-Polywell.org

a discussion forum for Polywell fusion
It is currently Thu Apr 24, 2014 12:39 am

All times are UTC




Post new topic Reply to topic  [ 293 posts ]  Go to page Previous  1 ... 12, 13, 14, 15, 16, 17, 18 ... 20  Next
Author Message
 Post subject:
PostPosted: Sun Mar 27, 2011 11:59 pm 
Offline

Joined: Sun Sep 28, 2008 2:29 pm
Posts: 4834
I might be missunderstanding something, but did somebody here seriously believe that there was a nuclear explosion of some sorts?
LOL


Top
 Profile  
 
 Post subject:
PostPosted: Mon Mar 28, 2011 12:51 am 
Offline

Joined: Tue May 06, 2008 11:54 am
Posts: 1979
chrismb wrote:
hydrogen that doesn't burn with an invisible flame.
http://www.youtube.com/watch?v=MMB2VR0087w
I'm all ears.


Top
 Profile  
 
 Post subject:
PostPosted: Mon Mar 28, 2011 4:44 am 
Offline

Joined: Fri Jul 06, 2007 2:03 am
Posts: 786
Location: Metro NY
I've been looking at the list of isotopes that TEPCO started releasing from March 24th. And I have a question concerning the BA-140, LA 140 Cerium-140 decay chain.

heres the source info from the water in the turbine room @#3:

http://www.tepco.co.jp/en/press/corp-co ... 503-e.html

Image

Barium 140 half life is 12.8 days, Barium 140 decays to lanthunum 140 (half life of 40.5 hours) which then decays to the stable cerium 140.

http://energyfromthorium.com/tech/physics/decay2/

The ratio of Ba to La seems to suggest fission occurring after March 12th, roughly. But then if you look at the sample from March 26th

http://www.nisa.meti.go.jp/english/file ... 27-1-5.pdf

The ratio of Ba to La still suggests recent fission. Lets guess and say around March 14th.

If we then look at Technetium99m (Tc99m, half life of 6.02 hrs.) we see this present in samples from both the 24th and the 26th.

Does this not suggest fission as recently as 60 hrs from the time the sample was taken? If we assume that 45% of the fuel rods in Reactors #2&3 were uncovered, and 45% then "fell on the floor" of the reactors, are we talking the possibility of low level recriticality in reactors 2 & 3 ?

_________________
I like the p-B11 resonance peak at 50 KV acceleration. In2 years we'll know.


Top
 Profile  
 
 Post subject:
PostPosted: Mon Mar 28, 2011 8:11 am 
Offline

Joined: Mon Jul 07, 2008 12:48 am
Posts: 818
Skipjack wrote:
I might be missunderstanding something, but did somebody here seriously believe that there was a nuclear explosion of some sorts?
LOL


No, who said that?

What was said was that the reactor vessel had most likely popped ... as in over-pressure failure and breached containment. If you examine the video you'll see the amount of concrete debris that gets airbourne (tall, narrow, gray plume) is more than just the few roof panels that reactor1's hydrogen explosion, (white smoke), tossed around. There is also a bright orange/yellow flame deep down in the building that is not consistent with hydrogen explosion explanation.


Top
 Profile  
 
 Post subject:
PostPosted: Mon Mar 28, 2011 10:46 am 
Offline

Joined: Sun Sep 28, 2008 2:29 pm
Posts: 4834
Ok, that makes more sense.
So when the reactor vessel blows that is simply a pressure explosion. How would that explain the flames?
They still have not sent in any darn robots yet?


Top
 Profile  
 
 Post subject:
PostPosted: Mon Mar 28, 2011 11:21 am 
Offline

Joined: Sun Sep 28, 2008 3:05 pm
Posts: 5856
Location: Northern VA
skipjack wrote:
They still have not sent in any darn robots yet?
With a volume that "hot", would a robot work? Remember, the Space Shuttle main computer has processer equivalent to the old intel 286 generation because anything with smaller features is too subject to derangement by radiation.

Does any robot in Japan have features the size of a 286? Would even THAT size stand up to the radiation described in some of the publicatios (>1 Sv/hr)?

Sometime lower tech is better than higher tech, but if you have none...


Top
 Profile  
 
 Post subject:
PostPosted: Mon Mar 28, 2011 12:23 pm 
Offline

Joined: Sun Sep 28, 2008 2:29 pm
Posts: 4834
Quote:
http://jalopnik.com/#!5786275/this-is-the-scariest-tsunami-video-yet


After watching this video, I have a hole different level of appreciation for the stability of that nuclear power plant. It seems really hard to compete with forces like that...

Quote:
With a volume that "hot", would a robot work? Remember, the Space Shuttle main computer has processer equivalent to the old intel 286 generation because anything with smaller features is too subject to derangement by radiation.


Uhm, no. I dont know where you are getting these ideas from.
People constantly bring their laptops, ipods and other computers to the ISS with them.
The Space Shuttle computers were updated several times during the lifetime of the Shuttles. The last update brought a full glass cockpit. You think that you can run that on 286 CPUs? I doubt it.
I heard that until recently many systems were using 486 CPUs, because they are very robust and still onyl require passive cooling, but 286? I am sure not.
Also, there are actually robots that were specifically developed to work in nuclear power plants in case of an accident. If anything, you should be able to shield them sufficiently.


Top
 Profile  
 
 Post subject:
PostPosted: Mon Mar 28, 2011 4:08 pm 
Offline

Joined: Thu Jun 26, 2008 6:52 am
Posts: 2237
Criticality would imply nuclear explosion- at least on a tiny scale- that is what is happening in a normal active nuclear reactor. . Under the proper conditions this could result in a lot of steam pressure building up and result in an explosion, or at least contribute to an ongoing chemical explosion.Certainly a similar steam explosion could occur from the decaying fuel rods after shutdown. There would not be any direct color from this steam explosion. If some pieces of fuel rod were pulverized, at a temperature of ~ 1200 degrees C they would probably be glowing ~ yellow. But they would not be part of the explosion unless some remarkable brief conditions were met that led to nuclear fission. I suspect this would be extremely difficult at uranium concentrations of less than 5 percent. If they were MOX fuel rods though, I have no idea how the plutonium would respond.
But, my point is that the yellow glow at the base of the explosion has many possible explanations without needing participation by the core or core steel container. Again, the radiation surge would have been huge and persistent if the core was disrupted and dispersed. I would be more suspicious that the spent fuel rod storage tank could have been disrupted than the 6 inch(?) thick stainless steel reactor vessel. If so, there should be spent fuel rods scattered around the floor of the containment building and once again the radiation readings would tell the story.

The differential decay ratios mentioned above are interesting, though I'm not sure how many scenarios could result in the ratios. I do wonder about the shutdown design of the reactor. If the fuel rods are reaching temperatures of ~ 1200 degrees C, then the aluminum alloy(?) control rods would possibly be melting and slumping to the base of the reactor. Would this allow the fixed fuel rods to start active (at least on a low but significant level) neutron driven fission? This seems an obvious design consideration, but surely it was addressed in the design!. Boron injection might mitigate this, but only if the solution covered the rods (or if the fuel rods also melted and pooled in the base of the reactor and mixed with the boron left behind as the solution evaporated.

Dan Tibbets

_________________
To error is human... and I'm very human.


Top
 Profile  
 
 Post subject:
PostPosted: Mon Mar 28, 2011 6:15 pm 
Offline

Joined: Sun Sep 28, 2008 3:05 pm
Posts: 5856
Location: Northern VA
D Tibbets wrote:
Criticality would imply nuclear explosion- at least on a tiny scale- that is what is happening in a normal active nuclear reactor.
I think "criticality" in a powerplant merely means a sustained nuclear reaction while in an nuclear bomb it means a run-away nuclear reaction. Same basic reaction, different rates, by MANY orders of magnitude! I suspect that if the core COULD go bomb-type critical, they wouldn't have to worry about evacuating the nearest 20 km because the plant would have already evacuated that region for them. :?


Top
 Profile  
 
 Post subject:
PostPosted: Mon Mar 28, 2011 7:24 pm 
Offline

Joined: Sat Dec 13, 2008 6:00 pm
Posts: 3161
http://en.wikipedia.org/wiki/Criticality_accident

Can it go up like a bomb? Let's see, now. Lots of molten heavy isotopes around, more than critical mass, heavy ones sink, light ones float. Will a critical mass find itself in proximity to some moderator (water?). Best to hope that this combination doesn't happen. Can it go up like a bomb? If fissile material is out of control and melting whichever way it wants to, why might it not go up like a bomb? 'All you have to do' is accumulate a 50kg lump of U235. A core in melt down might do that for you, no?


Quote:
"Tokyo Electric Power Co. said Wednesday it is considering spraying boric acid by helicopter to prevent spent nuclear fuel rods from reaching criticality again, restarting a chain reaction, at the troubled No. 4 reactor of its quake-hit Fukushima No. 1 nuclear power plant. "The possibility of recriticality is not zero," TEPCO said as it announced the envisaged step against a possible fall in water levels in a pool storing the rods that would leave them exposed."


Top
 Profile  
 
 Post subject:
PostPosted: Mon Mar 28, 2011 7:57 pm 
Offline

Joined: Sat May 01, 2010 6:43 am
Posts: 585
D Tibbets wrote:
Does boron burn with a yellow- orange flame?

Oh, I know the answer to this one:

http://www.youtube.com/watch?v=JzqdHkpXuy4


Top
 Profile  
 
 Post subject:
PostPosted: Mon Mar 28, 2011 8:21 pm 
Offline

Joined: Sun Sep 28, 2008 2:29 pm
Posts: 4834
I dont think it can go up like a bomb. Remember, building nuclear bombs is hard. The iranians have been trying for years without success. The North Koreans have not had much either.


Top
 Profile  
 
 Post subject:
PostPosted: Mon Mar 28, 2011 8:28 pm 
Offline

Joined: Thu Sep 17, 2009 11:18 pm
Posts: 4527
Location: North East Coast
D Tibbets wrote:
Criticality would imply nuclear explosion- at least on a tiny scale- that is what is happening in a normal active nuclear reactor. . Under the proper conditions this could result in a lot of steam pressure building up and result in an explosion, or at least contribute to an ongoing chemical explosion.Certainly a similar steam explosion could occur from the decaying fuel rods after shutdown. There would not be any direct color from this steam explosion. If some pieces of fuel rod were pulverized, at a temperature of ~ 1200 degrees C they would probably be glowing ~ yellow. But they would not be part of the explosion unless some remarkable brief conditions were met that led to nuclear fission. I suspect this would be extremely difficult at uranium concentrations of less than 5 percent. If they were MOX fuel rods though, I have no idea how the plutonium would respond.
But, my point is that the yellow glow at the base of the explosion has many possible explanations without needing participation by the core or core steel container. Again, the radiation surge would have been huge and persistent if the core was disrupted and dispersed. I would be more suspicious that the spent fuel rod storage tank could have been disrupted than the 6 inch(?) thick stainless steel reactor vessel. If so, there should be spent fuel rods scattered around the floor of the containment building and once again the radiation readings would tell the story.

The differential decay ratios mentioned above are interesting, though I'm not sure how many scenarios could result in the ratios. I do wonder about the shutdown design of the reactor. If the fuel rods are reaching temperatures of ~ 1200 degrees C, then the aluminum alloy(?) control rods would possibly be melting and slumping to the base of the reactor. Would this allow the fixed fuel rods to start active (at least on a low but significant level) neutron driven fission? This seems an obvious design consideration, but surely it was addressed in the design!. Boron injection might mitigate this, but only if the solution covered the rods (or if the fuel rods also melted and pooled in the base of the reactor and mixed with the boron left behind as the solution evaporated.

Dan Tibbets


Dan,
I am not sure what you mean in the lead sentence. Criticality would imply a neutron induced self sustaining balanced power reaction. Not growing (supercritical) or declining (sub-critical).


Top
 Profile  
 
 Post subject:
PostPosted: Mon Mar 28, 2011 8:31 pm 
Offline

Joined: Thu Sep 17, 2009 11:18 pm
Posts: 4527
Location: North East Coast
Skipjack wrote:
I dont think it can go up like a bomb. Remember, building nuclear bombs is hard. The iranians have been trying for years without success. The North Koreans have not had much either.


Wrong fuel type and wrong geometry. Power plants use slow fuels, hence the need for moderators. Weapons use fast fuel, and have dense geometry. Two different animals.


Top
 Profile  
 
 Post subject:
PostPosted: Mon Mar 28, 2011 8:37 pm 
Offline

Joined: Thu Sep 17, 2009 11:18 pm
Posts: 4527
Location: North East Coast
KitemanSA wrote:
D Tibbets wrote:
Criticality would imply nuclear explosion- at least on a tiny scale- that is what is happening in a normal active nuclear reactor.
I think "criticality" in a powerplant merely means a sustained nuclear reaction while in an nuclear bomb it means a run-away nuclear reaction. Same basic reaction, different rates, by MANY orders of magnitude! I suspect that if the core COULD go bomb-type critical, they wouldn't have to worry about evacuating the nearest 20 km because the plant would have already evacuated that region for them. :?


A weapon is a fast neutron induced supercritical event in a fast fuel. The closest thing to it in a slow fuel plant is called "prompt criticality". Going prompt can induce a pressure transient explosion if there is a mechanical failure of the containment (vessel or components).
When a slow fuel core slags, and loses geometry, it can be setup for a prompt critical event. Reactor vessel designs are inclusive of prompt criticality events. The envisioned (and days of old tested event) was the ejection of control rods. When a core slags, it loses geometry controls, and thus can lose neutron damping and power up. In extreme cases you could go prompt. Loss of geometry is a BAD thing, it has no rules other than no control.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 293 posts ]  Go to page Previous  1 ... 12, 13, 14, 15, 16, 17, 18 ... 20  Next

All times are UTC


Who is online

Users browsing this forum: No registered users and 0 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group