Hard Light Productions Forums
Off-Topic Discussion => General Discussion => Topic started by: Kosh on May 15, 2009, 08:14:10 pm
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After rewatching the season 1 episode 10 (the episode about the dirty bomb), I have a question. Is transporting nuclear waste casks really so dangerous to the truck drivers (when the driver turned up he had several cancerous tumors)?
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of what show?
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numbers (http://www.tv.com/dirty-bomb/episode/398600/summary.html)
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If I had to venture an educated guess, I'd have to say not at all. Sufficient amounts of lead shielding should be able to completely block gamma rays, which are the nastiest type of nuclear radiation.
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canisters for transporting readioactive and nuclear materials are remarkably robust, to the point that in my state firefighting certification course, our haz-mat team instructors told us to consider all applicably marked canisters safe unless obviously ruptured, and then we saw a video of a container being slammed head on by two trains, having a 2000lb bomb dropped on it, and then placed in burning jet fuel, and remaining intact...
something makes me remember that gamma/beta ways only go a matter of inches anyhow, so it would take a longer exposure to the alpha rays to get any sort of result
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canisters for transporting readioactive and nuclear materials are remarkably robust, to the point that in my state firefighting certification course, our haz-mat team instructors told us to consider all applicably marked canisters safe unless obviously ruptured, and then we saw a video of a container being slammed head on by two trains, having a 2000lb bomb dropped on it, and then placed in burning jet fuel, and remaining intact...
I was taught the same during my fire training - they essentially seal it in an indestructible lead tomb that not much short of the Death Star can penetrate. They're built to easily withstand any kind of train wreck, high speed (80mph) truck collision, fire, falling, etc.
You will not be getting cancer through them.
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something makes me remember that gamma/beta ways only go a matter of inches anyhow, so it would take a longer exposure to the alpha rays to get any sort of result
Actually, since gamma radiation is part of the EM spectrum, it propagates essentially infinitely through a vacuum (intensity fall-off via the inverse square law nonwithstanding), though I think just an inch or two of lead plating is enough to completely stop it. Alpha particles, which are essentially bare helium nuclei, are an incredibly damaging form of ionizing radiation...but only if they manage to get inside your body, as even something as flimsy as human skin or tissue paper is able to absorb them. Beta particles, which are high-energy electrons, can be stopped by a piece of tinfoil; they can do a moderate amount of damage, which actually makes them useful as a cancer treatment.
Isn't radiation fun? :p
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If I had to venture an educated guess, I'd have to say not at all. Sufficient amounts of lead shielding should be able to completely block gamma rays, which are the nastiest type of nuclear radiation.
In fact the most dangerous radiation is neutron radiation, which is basically unblockable by lead or other heavy elements and induces alpha radiation in water (meaning, in humans).
Gamma rays aren't really dangerous. The reason they can't be blocked that well, is that they have low interaction with matter, but that also means they won't interact with humans. Alpha rays the contrary, high interaction -> easily blocked, but deadly when an alpha radiator is incorporated.
Beta rays lie in between alpha and gamma.
Working near radioactive material always increases the risk for cancer, but only by a few percent. Iirc materials with heavy neutron radiation aren't transported, but stored in huge water pools (the only way to shield from this radiation) until this radiation has weakened significantly.
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There are three kinds of radiation that is associated with radioactive/fissile materials. First, alpha particles. They consist of a nucleus that's identical to helium, but without the electrons. It will be stopped by a sheet of paper or your clothes. Second, beta particles. These are electrons emitted from a radioactive element as it decays. It will be stopped by an inch or two of wood, or tinfoil. The third, gamma rays, are the most dangerous. They aren't a particle, so it is very difficult to stop them. Gamma rays will only be partially stopped by several centimeters of lead or several meters of concrete. Gamma rays are frequently used to kill cancer cells.
That's why those containers are so damn big. It has several dozen centimeters of lead to keep the rays from penetrating.
Neutron radiation, if you want to call it that, is not associated with any of the fissile materials those containers would possibly be transporting. It poses almost no threat to people, it is normally only capable of inciting fission is a pile of fissile material. What do you mean, "induces alpha radiation in water"? Alpha radiation is what happens when the nucleus of an atom attempts to become more stable by decreasing the neutron to proton ratio. Unless the water is already using Oxygen-17 as opposed to Oxygen-16, nothing will happen.
Gamma rays are, in fact, very dangerous. The reason that they can't be blocked that well is that they don't have a mass, not that they don't interact with matter. The rays are actually made up of very high-energy photons. Gamma rays are frequently used to kill cancer cells, because the higher metabolic rate of cancer cells makes them die more quickly, meaning that they can stop the treatment before 'good' cells start dying in large numbers.
The materials kept at the bottom of pools are spent fuel rods, stored there until they run out of room, in which case they take them somewhere else. The radiation that the water is used to protect us from is beta radiation, giving it that eerie blue glow.
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If you routinely deal in radioactive material, you have to wear a dossemter tag, and those results are supposed to follow you for life in a file at what used to be the NRC.
So at anyone one point in time, you should be able to find out what your lifetime dose has been.
Mind you, I have not been exposed to radioactive material in probably 20 years, but that was the drill at the lab, and at the engineering company I did an internship where I had my own Cessium source in my trunk :)
The rules may have changed :)
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Scotty there are so many things wrong here...
They aren't a particle, so it is very difficult to stop them.
Gamma rays are also particles due to the wave/particle dualism, and the corresponding photons also have mass.
It poses almost no threat to people
Of course thats why military develops neutron bombs ^^
That's just plain wrong.
What do you mean, "induces alpha radiation in water"? Alpha radiation is what happens when the nucleus of an atom attempts to become more stable by decreasing the neutron to proton ratio.
The neutron from the neutron radiation get's slowed by the light weight water molecules, and will fuse with other atoms, destabilizing them and as a result producing radiation, also the most destructive alpha radiation.
Unless the water is already using Oxygen-17 as opposed to Oxygen-16, nothing will happen.
Just.. wrong.
Gamma rays are, in fact, very dangerous.
They are not harmless, but they are, compared to the other types of radiation the most harmless if not shielded against.
The reason that they can't be blocked that well is that they don't have a mass, not that they don't interact with matter.
Of course photons have mass, where did you get that from?
The rays are actually made up of very high-energy photons.
Yes, and photons have mass.
And before you answer, please read the article about neutron radiation (http://en.wikipedia.org/wiki/Neutron_radiation) on wikipedia
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Of course photons have mass, where did you get that from?
Maybe from google (http://www.google.com.au/search?q=photon+mass).
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Well, if I remember my relativity correctly, they don't have any rest mass...but they do have inertial mass.
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That's the theory at least :) I believe there is some experimental data to demonstrate inertial mass. The zero mass thing is a logical short cut that I think theoretically describes a photon at rest.
Can a photon ever be at rest?
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Yep, what matters is momentum in these cases. Photons have momentum. They do not have rest mass because they only exist as movement of electric and magnetic field, and as such when they "stop" they are destroyed*, absorbed by matter in most cases, and their momentum is conserved.
As far as dangers of radiation go, all forms of radiation can be dangerous but with proper protection, it takes a lot for it to become a threat.
Ionizing particle radiation (alpha- and beta radiation)... not a threat externally, rather damaging when the source is ingested or inhaled or concentrated into some organ like thyroid gland. From outside, they are peanuts; alpha rays are stopped by few inches of air or the dead surface layer of your skin; you could wear a ring with alpha source in it for all your life and it would hardly do any damage at all.
Beta- particles are not a threat as such either; they stop by about dozen metres of air, or a wooden wall or plexiglass... however, beta+ particles are another matter because when a positron hits an electron, it causes annihilation and consequently creates two gamma photons of 511 keV, which means that practically all beta+ sources with activity of A could be considered beta/gamma sources with activity of A+2A (one A from beta activity, two further A's by gamma radiation induced by annihilation).
Gamma radiation... penetrates well, but like already said, that also means that majority of the stream of photons passes through your body doing no damage whatsoever, which means that if you have ingested an alpha source of activity A and gamma source of same activity (decause per minute)... the exposure you get from alpha radiation is a LOT bigger because every single helium nucleus hits your tissue and ionizes stuff and causes a lot of damage, whereas only a scant percentage of gamma photons hits anything within your body, most of it passes through. For a dangerous dose of radiation resulting from exposure to gamma rays, you need a really hefty exposure at high intensity, and that kind of occasions are really rare. There's also the fact that gamma radiation like other forms of EM radiation weakens in the inverse square of distance, so when you double the distance, you get quarter the exposure, which means gamma radiation is really a concern only in the immediate vicinity of high active source.
So.
Problems with radiation arise when:
-gamma radiation source is so intense and close by that the dosage grows big enough even despite the low dosage/exposure ratio. This is usually only a problem with really high active nuclear waste, or direct exposure to nuclear reactions. In which case there are usually more pressing matters to be concerned of, like the building collapsing on top of you or the glowing sludge proceeding towards you.
-alpha- or beta sources are ingested, inhaled or otherwise introduced to your body internally. This is the main hazard of ionizing radiation because gamma ray exposures of hazardous level simply don't happen that often. A nuclear bomb explodes, releases a burst of radiation (including radio waves, microwaves, visible light, thermal radiation, X-rays and gamma rays), and then that part is over with. But the explosion also vaporizes a lot of alpha and/or beta-active nuclei, both actual daughter nuclei from the fissile material and nearby matter affected by the neutron flux. This fine mix of stuff is spread all over the place and forms the so called fallout, which causes at least as much problems as the actual material destruction since it contaminates the food and water sources and the very air you breathe and it can cause a radiation poisoning all by itself without any contact to the actual explosion, not to mention the increased risk of cancer and deformations on growing fetuses...
Now then, neutron radiation.
Is not a real threat for the same reason gamma radiation is not really something to concern yourself with; when you're in strong enough neutron flux to cause problems, you'll have other things to think about... but not for long. Neutron radiation is basically only caused by nuclear reactions, not by nuclear decay. Spontaneous fission can cause this, but that's a very rare form of decay and rather insignificant compared to alpha, beta and gamma decay, so it can be considered to only be caused by fission and fusion reactions.
Now, neutrons aren't too bad by themselves. They are heavy, they have a varying amount of momentum depending on the source reaction (slow neutrons and fast neutrons), but they have no charge at all so they don't easily interact with negative electrons or positive nuclei. So they have a reasonably good penetration. The best shielding would be a material with as high nucleus density as possible. Lead is pretty good for this purpose. They also have a half time (or average life span) of about three ten minutes. The problems arise when they happen to hit some nuclei, because that basically converts the nucleus into another isotope which may or may not be unstable, and that means you end up with alpha/beta/gamma sources within your body.
It also is the reason why nuclear reactor parts end up radioactive, as well as some changes structural integrity as, for example, Fe-56 nucleus gains three neutrons it changes into Fe-59 which is an unstable isotope with half life of 44 and a half days, and decays into cobalt, which has different mechanical properties than steel. Of course if Fe-56 happens to gain four neutrons it will decay into Co-60, which further decays into nickel...
So yeah, all forms of radiation are dangerous, but all in different ways, and they can be dealt with in a way that largely neutralizes the threat from them.
The biggest exposure you'll likely get is from bad ventilation on regions with a lot of radon released from the soil... and background radiation in general.
*This is a fundamental interpretation of Maxwell's field equations - electromagnetic wave motion can not exist in frozen state; it is also the logical basement on which Einstein laid the Specific Theory of Relativity (speed of light is always observed constant).
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Of course thats why military develops neutron bombs ^^
That's just plain wrong.
Would you say that a tree poses a threat to people, just by being there? I wouldn't. But then, if you take a branch and start attacking people with it, it does. It all has to do with application. Naturally, neutrons are not all that dangerous to people.
please read the article about neutron radiation on wikipedia
I did. I disagree with your argument becuase of two things:
1) It's a wiki, and therefore, credibility is suspect, compounded by:
2) It doesn't have a single citation on the entire page.
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The science articles on Wikipedia are considered some of the best, and they're generally more reliable than those on Encyclopedia Britannica (or even in some textbooks.) I can't vouch for this particular article, since it does need citations, but it's trustworthy.
...and in any case, Herra is pretty much the final word.
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The science articles on Wikipedia are considered some of the best, and they're generally more reliable than those on Encyclopedia Britannica (or even in some textbooks.) I can't vouch for this particular article, since it does need citations, but it's trustworthy.
The one benefit inherent to science articles on Wiki is that, in a general sense, the only people who'd go out of their way to write and/or edit them are people who actually know what they're talking about. For even more guaranteed reliability, there are a few sites out there like Citizendium (http://en.citizendium.org/wiki/Welcome_to_Citizendium) that rely on actual experts in a particular field to maintain its articles.
...and in any case, Herra is pretty much the final word.
Very much so. He's been making me feel incredibly inadequate in my chosen field of study for some time now. :p That was a great sum-up.
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The materials kept at the bottom of pools are spent fuel rods, stored there until they run out of room, in which case they take them somewhere else. The radiation that the water is used to protect us from is beta radiation, giving it that eerie blue glow.
Oh and by the way, the glow is caused by phenomenon called Cherenkov radiation, which is essentially caused by charged particles exceeding the phase velocity of electromagnetic radiation in that electrically insulating medium. So basically when electrons from the reactor move faster than ~0.75c, it causes a sort of electromagnetic shockwave (not unlike what happens when you exceed the sound barrier), which disrupts the electron balance of the water molecules and when the electrons lower back to their minimum energy levels they emit a continuous spectrum of light (peak is at ultraviolet wavelengths) and it makes for a really cool light show when the original radiation particles are energetic enough. ;7
The water pool also does reduce the gamma radiation output; an 11.34 metres thick layer of water causes roughly the same level of gamma ray attenuation as one metre layer of lead.
Although the attenuation of gamma rays is slightly more complex and although it mainly depends on the penetrated mass, it's also somewhat affected by the matter of the medium... but density is the most influencial thing in it, so lead being 11.34 times denser than water means pretty literally that it's about 11 times better gamma stopper than water as far as thickness is considered.
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@Herra
Thx for the more detailed summary, but I still have to disagree on the part of lead being a good protection against neutron radiation:
As I learned (and it seems plausible) neutron radiuation doesn't interact with other nuclei at first because they are fast, so they are only a short time in the vicinity of the other nuclei. Lead (and other heavy elements) however don't slow them down very much, so that's why they can pass through there nearly unhindered. Only light nuclei, like hydrogen , lithium etc slow them down significantly.
Again, the wiki agrees, but I also learned it that way in school and when I visited a particle accelerator.
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Well, it sort of depends of the neutron energy doesn't it?
This (http://en.wikipedia.org/wiki/Control_rod#Materials_used) gives a pretty good idea about what materials have the best suitability for neutron capture. My memory of lead having high neutron capture cross-section was apparently not correct, and it appears that the density of the material has relatively little correspondence to it's neutron capture ability.
Here's (http://) a list of elements sorted in order of thermal neutron capture cross-section.