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10-14-2005 04:28 AM  12 years agoPost 21
tadawson

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Lewisville, TX

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One thought though, why don't they build the reactors deep underground?
Funny, I could swear that is what the last page or so of posts have been discussing . . . . .

- Tim

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10-14-2005 04:56 AM  12 years agoPost 22
rcsoar4fun

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Boise, Idaho

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IIRC one of the major dangers of a nuke plant is a full scale melt down, in which the core melts into the ground. I don't imagine being underground would help much.

Kristopher

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10-14-2005 06:07 AM  12 years agoPost 23
Vitya

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North York, Ontario

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Funny, I could swear that is what the last page or so of posts have been discussing . . . . .
Shut up I wasn't paying attention...


Oh wait, what the hell? I double posted somehow and with a big gap in between... How did I do that? It's like a day in between posts, no way that was me...

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10-14-2005 10:24 PM  12 years agoPost 24
tadawson

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Lewisville, TX

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IIRC one of the major dangers of a nuke plant is a full scale melt down, in which the core melts into the ground.
That is more of a myth than a reality, IE "Made for TV bulls**t" . . . A running reactor puts out a lot more heat that a melted core - see above comments about losing criticality in a meltdown scenario. And even if it were hot enough to get through primary containment, ever object that melts into the core material further reduces criticality, so what you end up with (as was found under Chernobyl, but still within the structure) is a really big blob of radioactive glass . . . .

- Tim

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10-14-2005 10:26 PM  12 years agoPost 25
tadawson

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Lewisville, TX

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Oh wait, what the hell? I double posted somehow and with a big gap in between... How did I do that? It's like a day in between posts, no way that was me...
Um, sure did . . . . same spelling, puncuation, and everything. Sorry I didn't notice . . .

- Tim

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10-15-2005 11:01 PM  12 years agoPost 26
foo

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Richfield, Minnesota

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i enjoyed the kiddofspeed story, i read it a few months back. The other 2 links are new to me, some good pictures in the 2nd one. good post thanks.

Raptor 30 v2 / OS .32 / JR 8103 / GY-401+9253 | Raptor 50 V2 / OS .50 Hyper

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10-18-2005 10:04 PM  12 years agoPost 27
tadawson

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Lewisville, TX

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I thought I had squirreled away some links to the disaster at Chernobyl. For those who have been following this thread, I was mentioning the melted core material beneath the reactor. Here are the links to those pictures:

http://www.spaceman.ca/gallery/chernobyl/r4
http://www.spaceman.ca/gallery/chernobyl/fruin11m
http://www.spaceman.ca/gallery/chernobyl/sark3b
http://www.spaceman.ca/gallery/chernobyl/f451
http://www.spaceman.ca/gallery/chernobyl/f421

There are a lot of others as well - for anybody interested, this is a very good site . . .

- Tim

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10-19-2005 12:14 AM  12 years agoPost 28
Heliscat

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Dublin, CA

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In the background you can see the toxic avenger! I was trying to find chernobyl on my Google world. Does anybody know where it is?

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10-19-2005 03:05 AM  12 years agoPost 29
tadawson

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Lewisville, TX

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Try this . ...
http://maps.atlasua.net/aquariusua/...lasUA&SC=150000

And enter "Chornobyl" in the search box. Note the alternate, more "Russian" spelling . . . .

- Tim

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10-19-2005 10:41 PM  12 years agoPost 30
Yug

rrMaster

UK. Herts

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Since discovering this thread last week and spending a few late hours with a brandy, it has left a lasting impression - kind of feel haunted now.

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10-19-2005 10:59 PM  12 years agoPost 31
Yug

rrMaster

UK. Herts

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Heliscat

search for Chornobyl Ukraine in Goodle World

51'16'08.15' N
30'13'17.02' E

Unfortunately, the resolution here isn't that good.

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10-19-2005 11:09 PM  12 years agoPost 32
A. Bundy

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Aurora,IL. 30W/SW of Chicago

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Fascinating read and pics.

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10-20-2005 03:36 AM  12 years agoPost 33
Heliscat

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Dublin, CA

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Cool, thank you Guy!

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10-21-2005 03:04 AM  12 years agoPost 34
Vitya

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North York, Ontario

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Awesome pics from the inside Some of the guys were saying how this would never happen in the US, did they never hear of three mile island? That was close enough in my opinion.

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10-21-2005 08:24 PM  12 years agoPost 35
tadawson

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Lewisville, TX

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Well, technically what happened at Chernobyl can't happen to a US reactor, since the runaway at Chernobyl and resultant graphite fire was a result primarily of a fundamental problem with that reactor design, coupled with the Soviet's failure to build a containment structure as US reactors have. Considering that the reactor design at Chernobyl is considered unsafe by US standards, and has never been build in the US . . . . you can't have the same problem!

Yes, TMI had a problem, and a bit of core melting, but the readiation released was barely above background levels . . . . containment worked exactly as designed. The primary issue (at least to me) is not so much the question of "do accidents happen", but rather "does containment work". If an accident is pretty much guaranteed to be contained, with no release of dangerous radioactive material, do we really care that there was an accident or internal failure in the plant? Statistically speaking, you can never get to the perfect, zero accident condition, but can get darn close. But that one time is enough . . . . . so you need to go down the containment route as well. Between the two approaches, then the chance of a dangerous release like Chernobyl becomes pretty negligible . . . .

- Tim

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10-23-2005 09:43 PM  12 years agoPost 36
Vitya

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North York, Ontario

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Do you know by any chance what happened to the TMI core? I would think disposing of any of the materials would be an interesting feat.

Also, despite doing a lot of reading, I don't quite understand why the reaction happens in the core when they lower the fuel rods. Where do the neutrons come from? Are the fuel rods suspended in coolant? Also is there enough radiation to kill you if you stand next to the core while running?

I seriously wish someone would make a nice site to describe how a nuclear core works down to the smallest detail, with graphics of course I'm a visual guy.

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10-23-2005 09:47 PM  12 years agoPost 37
Vitya

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North York, Ontario

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Also, what does it feel like to get a lethal dose of radiation? Do you get headaches or perhaps feel like throwing up instantly upon exposure?

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10-23-2005 10:03 PM  12 years agoPost 38
Augusto

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US

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Looks like the whole ghost town on a bike story was mostly an embellishment of a simple tour:

http://maisonbisson.com/blog/post/10300/

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10-24-2005 09:36 PM  12 years agoPost 39
tadawson

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Lewisville, TX

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Do you know by any chance what happened to the TMI core? I would think disposing of any of the materials would be an interesting feat.

Also, despite doing a lot of reading, I don't quite understand why the reaction happens in the core when they lower the fuel rods. Where do the neutrons come from? Are the fuel rods suspended in coolant? Also is there enough radiation to kill you if you stand next to the core while running?

I seriously wish someone would make a nice site to describe how a nuclear core works down to the smallest detail, with graphics of course I'm a visual guy.
Well, my recollection on the TMI core is that the major incident was a result of a coolant loop failure, and then the operators goofed and ended up getting a steam bubble in the core vessel, and thus could not get cooling water into it, and it had a partial melt. Nothing escaped the reactor vessel, and if my memory serves me correctly, the melted material is a solid mass in the bottom of the reactor vessel.

I honestly can't say that I recall what (if anything) they have done with the TMI core remains, but other than the factor of scale, the most likely solution would be to remove the primary pressure vessel intact, and bury it whole . . . . . . . or haul it off to a facility where the remaining fuel assemblies that may be intact can be recovered. Not sure of the size of the TMI vessel though, and considering it's location, it may be more "politically correct" to just let it sit inside primary containment. I know that Naval reactors are frequently pulled out intact - sadly, there is a location in Russia where the USSR used to just dump their "mistakes" in the ocean . . . . not good . . . . . .

To your second question, in a reactor core, the fuel rods are stationary, and are arranged basically in a grid with channels throughout into which control rods are inserted. The entire core assembly (at least in US reactors) is in the center of a very large and strong steel pressure vessel, and is flooded with cooling water from the primary coolant loop. This, in turn, is insite the large concrete containment structures that you see in typical photos of power plants. Regarding the source of neutrons to produce fission, well, that is pretty much the definition of radioactivity - the atomic structure is breaking down, and releasing particles, including neutrons as it does so. When a neutron hits another atom of the fissionable material, it causes that one to break down as well - at a rate higher than normal rate of decay of the material. So, for each neutron emitted which hits another molecule, you get two, and so on, and so on . . . in powers of two, which gets really large really fast, plus the release of energy which is a part of the fission reaction (E-mc^2 and all . . . ). (This is the underlying process in a nuclear explosion. The trick is to keep it from blowing itself apart before you get the energy release desired in an explosion . . . ) So, now lets introduct the control rods. They are made of a lot of things, but a fair amount if carbon . . . and thier purpose is to absorb neutrons. So, if you have the control rods in the core, enough neutrons are absorbed, that you no longer have enough free neutrons to sustain fission, and the reaction stops. Pull them out a lot, and the reaction will grow (excess of neutrons), or at a midpoint, the reaction will sustain (same number of free neutrons as needed to sustain fission). Geometry also plays a factor here, and that is where the concept of critical mass comes in - basically, if you don't have enough fuel material, or the right geometry, the emitted neutrons excape the core without hitting other atoms, and fission cannot occur. Since reactor fuel is typically only 2% Uranium or so (very low percentage, if I am not exact) vs. the pretty much pure material used in weapons, structure is very critical to sustaining fission. This gets back to a comment that I made earlier about a melted core not being able to sustain fission - if anything, the melted material is a LOWER percentage of Uranium than the intact core (all the other internal plumbing, structures, etc. that melt in) and the shape is now flat and wide in the bottom of the vessel - and it cools and hardens, as could be seen in the pictures from Chernobyl as well.

Regarding "Can you stand next to the core while it is running, or is it dangerous?" - well, in power reactors, the core, as I said, is in a containment vessel, submerged in water, so you really can't get "Next to it" per-se. I DO believe that maintenance personnel can be in the room with the vessel though with minimal risk. They definitely cannot have the cover open for refueling under power, but it is done regularly when shut down. I personally have viewed a running research reactor that ran in an open water pool (water is a good moderator, and the 10 feet of depth shielded this one fine) and was able to take photos of the core running with the only source of light being the radiation glow emitted by the core. One of the more amazing things I have ever seen, and somthing that I don't think many folks will ever get to see . . . . . .

While I cannot think of any sites that would present visuals offhand, I did a quick search and found these. Maybe a bit simplistic, but at least a start:

http://www.ida.liu.se/~her/npp/demo.html
http://people.howstuffworks.com/nuclear-power.htm
http://www.kernenergie.net/datf/en/...ive/reactor.php

- Tim

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10-26-2005 08:26 AM  12 years agoPost 40
Vitya

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North York, Ontario

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Thank you for the detailed post, that explained the generation of neutrons well and it makes sense now I know about the pool reactors as I've been reading like mad on all things nuclear (it all fascinates me) and I would love to see one in operation. I was curious about something but I just researched it now, I thought only lead was good enough to stop gamma radiation but apparently water works as well, I should have thought of that when looking at pool waste storage.

Thanks for the links by the way, I will check them out. For anyone interested, apparently a russian liquidator who helped clean chernobyl said the massive dose of radiation gave a metal taste as well as felt like millions of needles in the face.

I guess for me, the fascination lies in the danger. Something invisible killing you, thats something to wonder at.

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