shook@mcc-hi.UUCP (Rob Shook) (04/29/86)
The Cable News Network, as well as National Public Radio, have
been using the term "nuclear fire" and "graphite fire" in conjunction
with what appears to be a tragedy in the Soviet Union. I'm not
a physicist (I'm a psychologist), and am not familiar with these
terms.
What fuels a nuclear fire besides oxygen and heat? How does one
fight such a fire? Are there dangers other than the contaminated
exhaust put out by such a fire? Are there differences between a
nuclear fire and a graphite fire?
Any help would be greatly appreciated. Please email responses, or
post if you think the answer would be of general interest. Thanks.
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
{ihnp4,philabs}!ut-sally!milano!mcc-hi!shook : UUCP
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Robert E. Shook III | "What is it, Lassie? A boy fell down a mine
MCC-Human Interface | shaft and broke his ankle and is diabetic
Austin, Texas | and needs insulin? Is THAT what you're
512/834-3319 | trying to tell me?"
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =dhenson@islenet.UUCP (Donald D. Henson) (05/04/86)
> What fuels a nuclear fire besides oxygen and heat? How does one > fight such a fire? Are there dangers other than the contaminated > exhaust put out by such a fire? Are there differences between a > nuclear fire and a graphite fire? > Wellllllll, in an attempt to put a course in nuclear physics into 25 lines or so, here goes...... A nuclear fire is not really a fire in the normal sense. In the case of the Soviet Union problem, enough nuclear fuel is in close enough proximity that the fission process is producing extreme heat as well as very large levels of radiation. This heat apparently melted thru the fuel containers and caused the graphite to ignite. The graphite burns in the normal sense, i.e., it requires oxygen to continue burning and it burns at an extremely high temperature. When the graphite burns, it gives off smoke particles that, due to the fission reaction going on in the nuclear fuel, is radioactive. This is what has caused all the alarm in the non-Soviet world. The problem in putting out the fire is that graphite reacts with water to generate more heat. Water will not only not put out the fire, it will generate tremendous quantities of radioactive steam which is not a desireable product. After reading this, I realize that it is not too clear, but maybe it will help a little. Good luck on understanding the problem. Don Henson Infosys Consulting
friesen@psivax.UUCP (Stanley Friesen) (05/05/86)
In article <142@mcc-hi.UUCP> shook@mcc-hi.UUCP (Rob Shook) writes: >The Cable News Network, as well as National Public Radio, have >been using the term "nuclear fire" and "graphite fire" in conjunction >with what appears to be a tragedy in the Soviet Union. I'm not >a physicist (I'm a psychologist), and am not familiar with these >terms. To start with, "nuclear fire" is just a meaningless buzz phrase coined by the media. A graphite fire is just an ordinary fire in the form of carbon known as graphite(as opposed to the form of carbon known as diamond). Being essentially pure carbon, graphite burns *very* well when oxygen is present. > >What fuels a nuclear fire besides oxygen and heat? How does one >fight such a fire? Nothing else is needed, except of course the graphite! You would fight such a fire like any other fire, by trying to suffocate it. The problems in this case involve the fact that the graphite was in a small, enclosed space(inaccessibility), and the very high radiation levels in the vicinity of the fire(danger to fire fighters). Also, the fire may have been hot enough to evaporate water. >Are there dangers other than the contaminated >exhaust put out by such a fire? Are there differences between a >nuclear fire and a graphite fire? Well, beyond the normal dangers of a fire(smoke inhalation and the like), the contaminated exhaust is the only danger from the *fire*. However the contaminants being released into the air are not only radioactive, they are *also* toxic in thier own right, most of them are heavy metals(like Plutonium and Lead). In fact the toxic effect of heavy metals resemble those of radiation. In addition, if the melt-down of the reactor core was sufficiently extensive there is a danger of serious contamination of the ground water in the area due to radioactive material melting through the floor of the reactor.(Actually, the Russians may have used a local lake in fighting the fire and cooling the reactor, so the water may be contaminated anyway, without a complete meltdown) -- Sarima (Stanley Friesen) UUCP: {ttidca|ihnp4|sdcrdcf|quad1|nrcvax|bellcore|logico}!psivax!friesen ARPA: ??
mwg@petrus.UUCP (Mark Garrett) (05/07/86)
++ C'mon guys, let's get real about some things: > To start with, "nuclear fire" is just a meaningless buzz > phrase coined by the media. A graphite fire is just an ordinary fire > in the form of carbon known as graphite... I wouldn't call it meaningless. The news uses the term "nuclear fire" to emphasize that the fire is not ordinary. It has a radioactive pile as its source of heat, which means that it is VERY HOT, and will continue to get hotter until it melts down and spreads out, increasing its surface area enough to dissipate the heat it is generating. It also means that everything about it (smoke, steam, residue and the general area) is highly contaminated. > Being essentially pure carbon, graphite > burns *very* well when oxygen is present. Graphite doesn't burn at temperatures lower than a couple thousand degrees (C or F, I'm not sure). > ... Also, the fire may have been hot enough to evaporate water. Any fire that isn't hot enough to evaporate water isn't worth worrying about. > In fact the toxic effect of heavy metals resemble those of radiation. There are two aspects of Plutonium toxicity (as far as I understand). As a chemical, Plutonium Oxide is deadly in minute quantities in a very short time. As a radiation source Plutonium (with or without oxide) will give you radiation sickness which is longer term (days to years), involving all kinds of things (not just chemical poisoning). I don't think lead poisoning has the same multiplicity of effects. > ...(Actually, the Russians may have used a local lake > in fighting the fire and cooling the reactor, so the water may be > contaminated anyway, without a complete meltdown) They used wet sand to smother the fire (it's not clear if it's even out yet). Water would result in a lot of radioactive steam and possibly a hydrogen explosion (as someone pointed out in a previous posting). > Sarima (Stanley Friesen) -Mark Garrett
pmk@prometheus.UUCP (Paul M Koloc) (05/08/86)
>>The Cable News Network, as well as National Public Radio, have >>been using the term "nuclear fire" and "graphite fire" in conjunction >>with what appears to be a tragedy in the Soviet Union. In article <1144@psivax.UUCP> friesen@psivax.UUCP (Stanley Friesen) writes: >In article <142@mcc-hi.UUCP> shook@mcc-hi.UUCP (Rob Shook) writes: > To start with, "nuclear fire" is just a meaningless buzz >.. graphite [is a] form of carbon .. burns *very* well ..oxygen The graphite reactors run hotter than do the water bath variety here. In this incident the following scenario is more or less likely. The reactor had been running for a long time so that many short lived radioisotopes had been built up and these can be tricky when the graphite moderators are removed to replace spent fuel cells or the moderator rods themselves. They continue to generate heat so that the water cooling lines to the reactor could have been damaged. Without adequate water cooling the reactor fuel could melt down, quite quickly unless the moderator rods were SCRAMmed within a few moments. After the moderators have essentially stopped the nuclear chain reaction by isolating the fuel cells, the reactor nevertheless continued to melt down due to the energy of the radioisotope decay, and the lack of coolant. The graphite can reach temperatures of 4000 degrees before melting, but as it gets to very high temperatures it will burn first with oxygen and can even make reactive cyanide like chemicals with the atmospheric nitrogen and water. At normal temperatures this would not happen. Therefore the term "nuclear [driven] fire". Graphite itself is difficult to ignite, but once ignited in the presence of a lot of oxygen can burn very vigorously. In this case nuclear energy heating caused it to generate reactive gases which were probably "too toxic chemically" so they were vented. The introduction of fresh oxygen then mixed with the gases and they exploded, taking off the top of the large bay building. Then there was ample oxygen, so the graphite fire burst into an inferno. The slowly melting fuel began to coalesce to generate a chain reaction. The consequence of the additional nuclear and chemical heat was a boiling and chemical vaporization away of the volatile isotopes and chemicals. A few days later the Russians dumped sand and boron on the burning reactor pile using helicopters. After a couple more days it was covered and the fire was smothered and put out. The chain reaction quieted down, and some diminishing steam was generated by the cooling of the hot graphite blocks by the wet sand. Every thing is wonderful for 4 more days and then... Yippee (Phonetic for the appropriate Russian word), the sand is dry (it's a good insulator) ... the fuel begins to re-heat, ever so slowly it begins to melt, ... and consolidate and react faster and faster and then.. ... it pushes the fiery hot graphite base right through and into the molten supporting concrete floor. Meanwhile, back top side, a little powdery smoke and more noticeable radioactivity levels begin to steadily increase at an accelerating rate. The fire is out, Mayday is over, and the GRIM REAPER prepares to cut another swath. Gone are the farmers who were preparing the soil only a day or two before in the fertile Ukrainian soil for the view of the camera and the political ministers of farming. As the train rumbles away with its last load of survivors, the first shudder is felt for surrounding miles, as contact is made with the underground water table. Steam pressure builds; uranium, nearly one hundred tons of it, begins its lethal breeding frenzy into ... .... . . Plutonium. Some weeks later the molten fuel continues to melt and super-pressurize as it burrows deeper into through subsoils and limestone, away from the fickle human consciousness. You could almost hear this vengeful infant of Jupiter babbling to itself like a small boy playing in the sandbox and clawing his hand deeper and deeper into a mound of sand. . .. You can't catch me now, you can't, you can't stop me now, you can't, you can never, never get me again, .. but I'm gonna get you, I am I am. Then on the seventh day it blew up. The satellite pictures were really great. It remains there to become the mankind's last and only volcano. . ... The cloud's not got here yet. . People just didn't seem to care, it was all over,. ... and they just actually came out and sat on the porch, and waited for it. When it did come it was at night. I was in my bedroom. I saw a blue flash! There was not light outside... . And I saw it when I had my eyelids tightly closed. It was beautiful .. . but I can't .. remember .. what is beauty. Support your local fusion shop! +---------------------------------------------------------+--------+ | Paul M. Koloc, President: (301) 445-1075 | FUSION | | Prometheus II, Ltd.; College Park, MD 20740-0222 | this | | {umcp-cs | seismo}!prometheus!pmk; pmk@prometheus.UUCP | decade | +---------------------------------------------------------+--------+