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Understanding basic nuclear topics

by vaironl
Tags: basic, nuclear, topics
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Mar7-12, 08:39 PM
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I have never touched upon complicated topics of nuclear related subjects in my class(High school), except for the half life of uranium 238 and other nuclear decay subjects to find the age of rocks etc...
I was reading some of the topics in this particular category and I saw that the conversations are those of advance nuclear topics. But, wanting to understand more about nuclear power, I had to ask the following questions.

Why are most of the people including me, to my belief see the word "nuclear" as a threat of some sort?

Can nuclear waste somehow be disposed of its nuclear effects? As in people don't get affected by it [ A simple google search can answer this question, but I would like to see the forums opinion]

Is Computer Science largely used in the, nuclear field? ( This is mostly a personal question, since I'm interested in Computer Science and science in general)

Pardon me for my grammar, and if the discussion does not provide details or is ignorant
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Mar7-12, 11:39 PM
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Computer science is very much integral to nuclear work.
The basic physics of nuclear reactions are well understood, but keeping the multiple parameters involved properly sorted is exactly what computers do best.
Nuclear simulations are pretty close to the most advanced computer work done in the US.

The idea of 'nuclear wastes' is misleading, because it covers some very different items.
Most people think of spent nuclear fuel as nuclear waste, although it is only spent in terms of use within current reactor designs. The vast bulk of the energy potential is still in that fuel for future access. This is a valuable resource, not waste.
However, there is also real nuclear waste, machinery that has been contaminated, clothing and handling elements that are more or less radioactive, mining wastes and processing residues. These must be treated as the dangerous materials they are, much as we treat toxins or poisons, we remove them from human interaction.
Do note that most poisons, such as arsenic, never become less dangerous, so they have to be kept safe forever just as much as nuclear material. Nuclear gets considerable attention, but is really just another such long term danger that our civilization deals with.
Mar8-12, 06:48 AM
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Quote Quote by vaironl View Post
Why are most of the people including me, to my belief see the word "nuclear" as a threat of some sort?
The cold war and the threat of nuclear annihilation along with multiple nuclear reactor meltdowns or other incidents that has spread radioactive material over a large area. Also, there has been an almost 1 sided approach to the subject in popular films, shows, and books, which is the side that nuclear power and weapons are dangerous and can kill you and do weird things to you and all life. This has led to a severe misunderstanding about what radiation is and what it can do, and hence has led to great fear of it. (Not all of it is unreasonable fear, but I know of pretty much no one that actually knows what radiation is outside of physics people)

Can nuclear waste somehow be disposed of its nuclear effects? As in people don't get affected by it [ A simple google search can answer this question, but I would like to see the forums opinion]
Only in very specific conditions and it is very difficult to do. It pretty much isn't feasible at all.

jim hardy
Mar8-12, 08:44 AM
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Understanding basic nuclear topics

Why are most of the people including me, to my belief see the word "nuclear" as a threat of some sort?
I think because the power reactor came after the bomb not before it.

Had the bomb come second people would say instead:
"What an awful, silly, wasteful thing to do with perfectly good uranium. You can make electricity out of that stuff. "

McPhee's book "Curve of binding energy" relates this anecdote:
One of the Manhattan scientists with an ironic sense of humor took the reflector out of a flashlight and placed a cigarette in it. At next test he held it up to the glare and sure enough, he used an atom bomb to light a cigarette.

Now THERE's a statement.

old jim
Mar8-12, 12:49 PM
P: 186
As very much a 'noob' as far as nuclear physics goes when I joined this forum I have found learning about the following 3 concepts have helped very much in keeping pace with the discussions here. They are:

1. The concept that a nuclear reaction can become 'critical'. This concept helps explain how nuclear reactors provide energy to supply electricity and also how nuclear bombs work. And why they are very different. Understanding what k = 1 means is probably sufficient to keep pace on here. (This took me quite a while and some help from the experts on here).

2. The decay chain. This follows on from the half life concept but explains what happens to the half that has 'gone' from your uranium. It explains something about nuclear waste and something about decay products.

3. Decay heat. This explains why a scrammed reactor can still melt down and why we worry about the cooling of spent fuel pools still. It was a revelation to find out that the majority of the heat in the Earth's core is due to decay heat.

If you are the type to sit and watch YouTube I found the 'radiation' and 'nukes' lectures very informative (and entertaining) from the series Physics for Future Presidents by Prof Richard Muller.
Mar8-12, 07:09 PM
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With respect to critical, k = 1, that means that the fission rate in a system is constant, neither increasing or decreasing. In a nuclear reactor, plants normally operate in baseload mode, that is producing power at a constant rate. Reactors must go from zero power to full power, and they must shutdown at some point. In between they may go up and down as the need arises. To decrease power, k become < 1 (subcritical), and to increase power, k > 1 (supercritical). The difference between k and 1, ρ = k - 1, is the reactivity of the system.

Reactivity is introduced carefully and gradually, so that power changes occur slowly.

If too much reactivity is added too rapidly, the power increase might exceed allowable limits and damage fuel in the reactor core. Most reactors work with a spectrum of neutron energies, which is important for control. In thermal reactors, the plants make use of small number of delayed neutrons, in addition to the thermal neutrons that take time slowing down from fast energies.

Nuclear weapons are a different animal. To function, they go prompt supercritical, which is a domain to be avoided with power reactors.

The by-product of the fission process is the accumulation of fission products, or radionuclides (isotopes) of various elements. The fission products must be isolated from the environment since exposure to their radiation can be harmful to living things. The final disposition of radioactive material is a significant issue with respect to nuclear energy.

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