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Posted: 9/16/2001 4:11:36 PM EDT
OK, I am in the Commercial Drywall business. My company does quite a bit of work in the local hospitals. Quite often, we find ourselves installing lead shielding in Xray rooms. This shielding varies from 1/16" to 1/8", and is typically installed to a height of 7'. We buy it in 4'x7' rolls. I am told the rays emitted from an XRay machine only travel in one direction, and do not bounce around. Once they hit lead, they stop in their tracks. That's the reason the lead only goes 7' high in most hospital applications. I have rougly 900 square feet of surplus lead in inventory. Enough to easily line a 12' long X 12' wide X 8' tall shelter. Roughly 50% of my inventory is 1/8" thick, while the other half is 1/16" thick. Would I be foolish in thinking that this would offer any type of worthy cover from radioactive fallout? This stuff is [b]HEAVY[/b]!, and expensive. 1/16" costs roughly $100 a roll, while 1/8" is $200 a roll. Would rather not waste it, if it wouldn't do any good. Any idea what the levels of radiation are that are emitted from an XRay machine vs. fallout from a nuclear bomb that was detonated 100 miles away? Thanks
Link Posted: 9/16/2001 4:14:44 PM EDT
[Last Edit: 9/16/2001 4:16:33 PM EDT by raf]
Link Posted: 9/16/2001 4:16:54 PM EDT
[Last Edit: 9/16/2001 4:17:06 PM EDT by Garand_Shooter]
Link Posted: 9/16/2001 4:19:33 PM EDT
Link Posted: 9/16/2001 4:25:10 PM EDT
Link Posted: 9/16/2001 4:34:02 PM EDT
Actually Gamma "Rays" are "Attenuated" in whatever shielding you use. Lead of course being the best. Best shielding without using lead would be earth, concrete, steel, etc. I don't have my notes with the formula's, but shielding depends on the density or the "thickness" of material used. Alpha & Beta particles can be stopped by thick paper if I remember right from school. Beta particles being ingested in food (fallout material) would be serious. But anyway Time, Distance and Shielding are in the equation for protection. Distance like 100 miles is the best shielding possible. Ha!!! Fallout (radioactive bomb material) depending on the type of burst and what kind of weather was present can send the cloud up into the jet stream. You'll need a "Geiger Counter" to do survey's. Ha....! Damn having "Flashback's" to my military days..... But anyway, there are only a few countries that have the proper delivery system's to hit this country. Biological and Chemical is the way they would go, you know, the "Poor Man's Atomic Bomb". That's material you could very easily bring into this country in a suitcase.
Link Posted: 9/16/2001 4:36:26 PM EDT
Link Posted: 9/16/2001 4:43:03 PM EDT
Garand_Shooter has it right. X-rays, and the far more energetic gamma rays, are penetrative electromagnetic rays. Alpha and beta radiation are far less penetrative particles. Alpha particles, in fact, pretty much have to be inhaled or swallowed to be harmful; while beta particles (which are high speed electrons) can penetrate the body on their own. After the initial burst of gamma radiation from the detonation, the lingering threat from that type of radiation hazard is relatively low. Fallout is radioactive for an awfully long time after the blast and is, IMO, the greater risk since if you are inside the blast radius you are vapor. In the NG, they taught us to dig in. Since the gamma radiation travels linearly, by digging in you allow it to pass over your head since it doesn't travel through the ground itself outward from ground zero. If you're exposed to the flash, you're exposed to the gamma radiation, in other words. That still leaves the particulate matter to deal with. That's where NBC suits and dosimeters and all that good cold-war era stuff come back into play. I'd still worry more about biologic weapons, chemical weapons, and plain old high explosives.
Link Posted: 9/16/2001 5:00:11 PM EDT
Link Posted: 9/16/2001 7:06:20 PM EDT
Most of the advice here is excellent, IMHO. I'll try to run down the particles for you. Some atomic nuclei are unstable and prone to decay. For the most part the further you get from an equal number of protons and neutrons in a nucleus the more unstable it is. Nuclei can decay into alpha or beta radiation, neutrons or gamma rays. Xrays are given off when the heavier particles have a change in energy(due to conservation of energy). ALPHA -- 2 protons and 2 Neutrons. Essentially a Helium nucleus. The kicker is it has a 2+ charge due to the fact that there are no electrons with it. This makes it extremely reactive-ripping off electrons as it passes through matter. Those atoms, hence stripped of their electrons react with other atoms settin up a chain reaction(the basis of fission reactions and the atomic bomb). It is also very heavy and causes damage in that manner as well due to its kinetic energy. It won't penetrate matter well because it is so reactive. So externally is not to bad. Internally, is a totally different story. You don't actually ingest the alpha or beta particles of course but the unstable atoms which decay to form them internally. Bad juju inside your cells. Most heavy nuclei get taken up into bone but can be found elsewhere as well. BETA -- these are just electrons. Far lighter in weight- about 1/2000th of a proton or neutron but they are charged(1-) and hence very reactive but not as much so as alpha particles.They will penetrate farther but once again are not to bad outside the body. Inside are bad. NEUTRONS--No charge but weight of one atomic mass unit. Penetrate almost infinitely compared to others but due to mass will still rip other particles from atoms and cause damage-it can be pretty bad even from outside the body. PHOTONS--Same properties as light but the ones we are dealing with here have higher energies and shorter wavelength. Not terribly reactive and no mass or charge but very penetrative and can cause elctrons to be removed from atoms. gamma--high energy photons from nuclear decay. Xrays--high energy photons from changes in energy and momentum of electrons For all intents and purpose gamma and Xrays are the same and affect tissue the same way. Nuclear decay can cause any combination of the above particles to be given off depending on the nucleus which decays and most unstable isotopes decay in predictable manners with measured half-lives into other isotopes which further decay,etc, etc until a stable isotope is obtained with approx equal numbers of protons and electrons. Many that decay into Alpha particles have very long half-lives up to billions of yrs. BELIEVE IT OR NOT.
Link Posted: 9/16/2001 7:22:50 PM EDT
FWIW, Lead will shield from photons best as noted previosly by garand shooter. Inconsequential for alpha. Shielding BETA with lead can actually be dangerous because when the electron passes these heavy lead nuclei their paths are affected which causes a change in momentum(and energy) and as such some of that energy is released(conservation of momentum and energy) as photons(xrays). So shield for Beta with paraffin,etc(less dense) then shield around that with lead to pick up the lower energy x-rays. As for distance I'd say off the top of my head that the numbers given you are pretty accurate. All radiation, sound, any wave adheres to the inverse square law. As distance increases the intensity of the wave decreases as the square of the distance. remember the equation for the area of a circle: A=pi times (radius)squared. Hence doubling the distance decreases the intensity 4 times, etc. Distance is very important as a result.
Link Posted: 10/10/2001 10:38:15 PM EDT
Man, you are really stirring the cobwebs. Radiation shielding is really specific to the radiation you are trying to protect against. In light water cooled reactors, the really damaging radiation comes from Nitrogen-16 - a high energy gamma radiation. The nuclear fuel is heavily sheilded by the coolant, internal vessel sheilding, the reactor vessel itself, coolant piping, etc. At least this is the case with naval reactors. The rule of thumb in this case was that 2" of lead attenuated 90% of incoming radiation, 24" of water did the same, steel was somewhere in between. Essentially, hydrogen molecules are best at attenuating neutron rays, such as plastic or water. Also, Very heavy masses such as uranium or lead are best at attenuating gamma radiation. A sheet of paper is sufficient to stop alpha rays.
Link Posted: 10/11/2001 3:34:59 AM EDT
If I recall correctly, here are the half value thicknesses (HVTs) for the following materials: Lead: 1/2" Steel: 3/4" concrete: 2.2" dirt/sand: 3.3" water: 6" wood: 8" A HVT is the thickness needed to reduce incoming high energy radiation (i.e. gamma rays from fallout) by one half. Therefore, to reduce the radiation by 1000 (actually 2xE10 = 1024), you would need 10 times the material (lead = 5", steel 7.5", concrete = 22", dirt = 33" etc.). This is why they recommend 3 feet (36") of dirt over bomb and fallout shelters. In other words, 1/16" or 1/8" of lead sheeting is not going to provide much in the way of effective shielding. You'd be much better off with 8" concrete block filled with concrete or gravel or sand. I hope this helps. Merlin
Link Posted: 10/11/2001 3:47:26 AM EDT
My head is spinning... If the SHTF then you can always melt down the lead and make bullets. [:D]
Link Posted: 10/11/2001 3:50:10 AM EDT
[Last Edit: 10/11/2001 3:47:25 AM EDT by AC_Doctor]
How about using some of those 1/16th" rolls, and making us some special, industrial strength, lead -lined tin foil hats for some of our " out there " AR-15.com members.
Link Posted: 10/11/2001 4:10:14 AM EDT
I dont know about Medical X-rays, like for chest rays and such... but Dental Radiographs use very little x-ray energy. The lead shielding is not for the Patient's protection, its for the Dr's and Assistant's protection against cumulative exposure. The little lead apron that they put on patients is just to show "we care"... A full mouth radiograph set + Panorex consists of approximately 20 radiographs... You actually receive more radiation from sitting in Sunlight at the beach for an afternoon than from an exposure to such Dental Radiographs. I would tend to think that fall out from a Nuke is higher in radiation... Did you ever see the movie "The Day After"? From what I recall in the movie, Fallout Radiation is BAD, but the radiation energy emitted from it only travels a very short distance... in the movie, people huddled in thier basements to put as much distance from the stuff on the surface as possible. With that said, it seems that IF you're concerned about fallout, an underground shelter may be your best bet and it doesnt necessarily have to be lined with "X" thickness of lead dependent upon depth of the shelter? M.
Link Posted: 10/11/2001 5:55:45 AM EDT
The lead shielding in an X-ray room is primarily to prevent scatter not a primary beam. The 7' height would depend upon state regulations. In a typical commercial building with lots of concrete in the flooring there would be no need to shield above and below. If this equipment was installed in a private clinic with std. wood flooring then if the areas above and below the room were occupied then the floor and ceiling would have to be shieled also.
Link Posted: 10/11/2001 6:47:33 AM EDT
Lets see. Dusting out the cobwebs. If you had 4 cookies emitting the four different types of radiation, and you could throw one away, what would you do with the other three. Alpha you hold in your hand because the skin will protect you. It cannot go past the outer layer of skin. It is however one of the worst damaging to internal organs if ingested or inhaled. Beta you put in your pocket because your layer of clothing with protect you. Gamma, you eat. Because it is so energetic, it will probably get out of your body anyway so no reason to do anything else. The slowing down length of a gamma even in water is very long, and it will still leave without doing damage. The neutron emitter you throw away. This is because it will do damage while slowing down. The hydrogen in water is an equivalent weight to the neutron, and will therefore absorb some of the neutron's energy to help slow it down. Thus causing damage where this energy is absorbed. Pogo is correct on the thicknesses of material to be equivalent, but I think he is wrong on how much it stops. It is only half again on what it stops. Distance and shielding are the two that reduce it. As a point source, the radiation falls off rapidly. It goes down by the square root for every foot. drjarhead is mistaken, it is the neutron particals that generate more radiaton as they pass through lead, as the beta would have been stopped by just the drywall. That is why there are layers of shielding to prevent the newly generated radation from getting through.
Link Posted: 10/11/2001 6:54:17 AM EDT
Go find you a book from the 50's or 60's concerning building your own fallout shelter. I think they will probably be government issue. Gamma is by far the most penetrating. I heard 10 feet of concrete somewhere. What you have to watch out for is this. Multi MegaTonnage plus fallout in local vicinity. Highly radioactive "SNOW", Which is basically ash, but with alpha,beta,gamma components. Plus the initial pulse, which is gamma in at least megawatt output. But get this. After 50 generations of neutrons in an atomic detonation the primary is developing over 10 BILLION BILLION WATTS or power. If their is a secondary or booster then they will be higher. This is highly penatrative, I don't know if over a foot of concrete is enough. Benjamin
Link Posted: 10/11/2001 8:26:16 AM EDT
Everything you never wanted to know about surviving a nuclear mishap is in the DOE publication Nuclear War Survival Skills, available online at [URL]http://www.oism.org/nwss/[/URL] Ingredients required for a nifty blast and radiation proof temporary dwelling: unfrozen ground with suitable drainage if possible, 24 hours, an ax, a shovel, and IMO also a blower with battery power and HEPA filter so as to pressurize the hole & prevent infiltration of radioactive dust. If you've got a front end loader the designs in the book can be completed in an hour.
Link Posted: 10/11/2001 8:33:59 AM EDT
Originally Posted By 7: My head is spinning... If the SHTF then you can always melt down the lead and make bullets. [:D]
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I seconf that idea.
Link Posted: 10/11/2001 9:02:52 AM EDT
I have come to the conclusion that I may as well stick my head between my legs and kiss my a$$ goodbye! Red
Link Posted: 10/11/2001 12:23:15 PM EDT
Originally Posted By Andrewh: Lets see. Dusting out the cobwebs. If you had 4 cookies emitting the four different types of radiation, and you could throw one away, what would you do with the other three. Alpha you hold in your hand because the skin will protect you. It cannot go past the outer layer of skin. It is however one of the worst damaging to internal organs if ingested or inhaled. Beta you put in your pocket because your layer of clothing with protect you. Gamma, you eat. Because it is so energetic, it will probably get out of your body anyway so no reason to do anything else. The slowing down length of a gamma even in water is very long, and it will still leave without doing damage. The neutron emitter you throw away. This is because it will do damage while slowing down. The hydrogen in water is an equivalent weight to the neutron, and will therefore absorb some of the neutron's energy to help slow it down. Thus causing damage where this energy is absorbed. Pogo is correct on the thicknesses of material to be equivalent, but I think he is wrong on how much it stops. It is only half again on what it stops. Distance and shielding are the two that reduce it. As a point source, the radiation falls off rapidly. It goes down by the square root for every foot. drjarhead is mistaken, it is the neutron particals that generate more radiaton as they pass through lead, as the beta would have been stopped by just the drywall. That is why there are layers of shielding to prevent the newly generated radation from getting through.
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No Dr jarhead is not mistaken. Xrays are a result of changes in energy and momentum of electrons. When an electron passes a heavy neucleus its path is altered and a photon or Xray is released. I Believe in this case it is called a Brehmstrahlung Xray(unsure of exact spelling-did look for it, though)
Link Posted: 10/11/2001 12:49:44 PM EDT
Red - Not sure what your envisioning, but- Wondering if you have a basement? If so its a good start. Check around. If you want a blast shelter, you got a lot of work to do. If your concerned about non-fission release of radioactive materials or secondary radiation from fallout, then its easier. Plenty of info around. Hell and all those shelter manufacturers went belly up due to the "peace benefits" of the closing of the cold war. Non-nuclear EMP would be more of a pisser. Anyone know if you could make a Faraday Room out of that lead? Line your garage and you'd have the only running vehicle in your town. Luck Alac
Link Posted: 10/11/2001 11:37:52 PM EDT
What I still resent in Naval Nuclear Power School class 8405 is being docked 2 points on a test for spelling "bremstrallung" wrong. However it is spelled.
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