Yeah, like I said, you're the master of high-level radiation. But don't discount the possibility of anything but nukes...security of sources up to 150 curies is EXTREMELY lax, yet simply touching or coming within a few inches of an unshielded source of this kind can cause radiation burns that will never completely heal.

As far as the survey meters, though, ours go up to 1R (and yes, I have seen it maxed out). I worry about people getting too complacent after reading this, though, because even extremely low doses will do serious damage over time. For instance, we are limited to 3R per year on our film badges...if we exceed that (or even get close to it), we have a hearing with the NRC, undergo blood tests, and are prohibited from working for one year. Even if we pick up a dose that maxes out our dosimeter (200mR), we are required to get a blood test. We were also taught that picking up 2R (I picked up 2.5R in 2006) equates to a shorter life expectancy by one day (but this is not proven or exact, just a general guideline). Acceptable dose (according to the NRC) for the general public is 2mr/hour.
One thing that I wanted to mention. It doesn't apply to fallout so much (where particles are spread out) but to sources where the particles are contained in a single area (a building, for example, or if a terrorist drops an isotope into a crowd of people). With inverse square law, you can calculate radiation levels at any distance from the source, as long as you have a reading from one definite distance. Radiation loses strength in this way: 2X the distance from the source, 4X less radiation. For a simple example, if you are fifty feet from a source, and getting a reading of 100mR, the level will be 25mR if you retreat to one-hundred feet. Will you use that info? Probably not, but it doesn't hurt to know.

Again, Christian, not trying to undermine your info or make myself seem more knowledgeable than you (it's too easy to sound condescending or argumentative when you don't mean to be, when working in text and not in person). I'm just trying to offer what I can to help people with preparedness.
By the way, I'm an industrial radiographer (ask your friend about it...we're the crazy guys who willingly blast ourselves with gamma rays for the sake of inspecting welds and piping).

it's too easy to sound condescending or argumentative when you don't mean to be, when working in text and not in person

you're right, i in no way meant to come across that way. you might say i'm just gunshy after years of having some people argue with me. and i am in no way the master of anything...just explaining some of the stuff i've picked up over the years.

you are absolutely right about long term exposure to low levels of radiation...i usually don't go into the difference between real radioactive materials and fallout because i'm afraid of confusing people, but that is probably fairly unlikely here. as i understand it, fallout gives off radiation quickly and loses potency quickly, but actual radioactive material gives it off slowly, but for a much longer period of time (years or even centuries). contact with it over long periods of time is the same generally as short term exposure to fallout...it will still hurt you.

but your knowledge of real radioactive material far exceeds mine. i'm not even sure how to convert from curies to roentgens (or if it is even possible). i absolutely do NOT know enough to be able to work with the stuff, my knowledge is solely based on what to do if the nukes fall.

my hope is that we can work together to help people here understand what they can do to protect themselves from all aspects of radiological dangers...if not as equals then at least as fellow preppers. i have a feeling i could learn a lot from you, please don't think i am trying to crowd you out or argue with you in any way.

Everything's alright, I just wanted to clarify so that no one is offended unintentionally. I'm actually really glad to have someone to talk to about this stuff, I don't usually have that opportunity, and it can be really interesting.
Basically, my place, as I see it, is to help with equipment advice and basic math-related stuff. I'll leave the rest to you, as you seem to be better than me at information, insofar as what actions to take.

That said, here's some more info. Depending on the type of radioactive material, the decay rate can vary drastically. Iridium-192 has a half-life of 90 days. Cobalt-60 has a half-life of a bit over five years. Half-life is how long it takes a radioactive source to decay to half of its original strength, measured in curies (example: a 150-curie source of Ir192 will decay to 75 curies in 90 days, then to 37.5 curies in another 90 days). So you can see that there's quite a bit of variation. At any rate, though, it takes a long time to decay to the point that it won't harm humans. Even a source radiating 2mR onto you (the legal civilian limit, and a miniscule amount), will yield 1440mR, or 1.440R, within a month if you have constant exposure (not calculating decay, which will be miniscule if you're talking about cobalt). If you up that figure to 20mR, the average reading that I pick up during a well-shielded exposure, if it were constant, would lead to 14,400mR (14.4R) in a month of constant exposure.
This isn't insignificant. You may not experience any symptoms, but damage can be done on the genetic level, passing genetic defects to your offspring and greatly increasing the risk of cancer later in life. Keep in mind that even 20mR is extremely low level. If an unshielded source was radiating near you without your knowledge, you could experience much higher levels. This happened to a family in Mexico back in the '70s (I have the documentation in one of my safety books, but don't have access to them right now due to the move...will post it after I get set up, along with some more charts and such). The entire family died of radiation poisoning within two months, from a small radioactive source that had been placed in one of their kitchen cabinets.

I don't know how you would go about converting curies to Roentgens...Someone once told me approximately how many R were equal to one curie, but I don't remember and don't even know if it was accurate. I can tell you that the curie is actually not used that much, at least not in determining activity levels...for that, it's usually gigabecquerels (GBq, 1GBq = 27 millicuries). Or it can be measured in megabecquerels or terabecquerels.
Beyond this, I start to get in over my head, because you'll get into measurements for mass, weight, and the like (sieverts, grays, and coulombs, etc.). Plus I'm getting tired and my mind doesn't want to do much more calculation. I'll try to clarify tomorrow when I'm more coherent.
Hope that helps in some way (it may have just confused more). Like I said, when I have access to my books again, I'll have a reference to answer a lot more of these questions that I don't deal with in my line of work.

ok, i am familiar with the decay rate of some of the various elements and i can understand the measurement in curies, though i don't have a frame of reference i can apply to real life. i also know about half-life, especially as it relates (again) to fallout. that said, everything you wrote in the last couple of paragraphs is greek to me...over my head.

i'm not sure i accept genetic damage leading to birth defects in future children...as far as i know the only time genetic damage has resulted in a birth defect was when the developing fetus was exposed itself. of course i could be wrong and it should be a moot point anyway as no one in their right mind would put it to the test.

one of the situations we will have to deal with post nuclear war is the fact that alpha and beta particles decay at a slower rate than gamma. these particles don't require much to shield against them but direct contact is a bad thing, especially things like breathing them in or eating something with them on it. so yes, i understand the danger of prolonged contact with radiological materials, even if the dosage is less than what would normally be required to cause general radiation sickness.

Yeah, that's the problem with this...so much is theoretical, estimated by some scientist with a $20-million supercomputer and forty years of education in nuclear science. They're still studying Chernobyl, for crying out loud.
Basically, us regular Joe Sixpacks can rely on the formula "radiation = bad, avoid if possible". Regardless of what levels are supposed to be "safe", I'm sure going to avoid it to whatever extent that I can, as I don't want to be the one to prove whether their calculations were correct or not.

amen. as i show concerning fallout shielding, while 2-3 feet of dirt is supposed to be enough, i recommend 6-10 feet and i intend to cover my home (underground house) witk 12-15 feet. and this area is one of the few places in the country unlikely to see ANY fallout.

Yeah, I'd go with as much shielding as humanly possible, as well.

We have a piece of equipment at work called a "collimator":


It's made out of tungsten, and provides shielding equivalent to five half-value layers. It works extremely well when you use it right, considering how small it is (about three inches end to end, maybe a little smaller). You get used to having that extra protection, and you'll sometimes get in a hurry and forget that the rounded side has to be pointing toward you before you expose...if not that, then sometimes it's impossible to have it set up optimally, if your workspace isn't ideal or the part you're x-raying is odd-shaped. Then you'll blast yourself with a couple Rs.
Anyway, my point is that if you take away that tungsten collimator, even if there's two inches of carbon steel between you and the source, you pick up a lot. Radiation is a lot harder to block than anyone would imagine.

You could always line your bunker with several inches of lead...

actually, a foot of lead equals 16 inches of steel, 4 feet of concrete or 6 feet of packed dirt...of them all dirt is MUCH easier to work with and by far the cheapest. i'd use steel for the blast door and possibly lead for the vents, but simply placing a couple 90 degree bends in the pipes several feet apart works much better.

something most people don't realize...a foot of air is enough shielding to reduce alpha and beta radiation by a factor of a thousand and a mile of air will do the same for gamma. so, if you build a straight tunnel shelter you won't have to seal the ends as long as the opening is a mile from where you're staying.

that collimator IS cool though...

You're right about that...like I said, double the distance from the source, and you'll decrease the radiation level fourfold. When I was doing the practical training for my job, the guy teaching me said, "If something ever goes wrong, don't bother trying to hide behind some metal...just get your ass away from there."

That's another thing I have in my safety books, is info on the shielding properties of a bunch of different materials, but I don't know them offhand. Dirt IS very good at shielding...when I inspect pipelines that are already in a ditch, just going around the corner at a 90-degree fitting virtually eliminates all radiation.

Bruce Beach (many of you are already familiar with the name) operates Ark II
http://www.ki4u.com/nuclearsurvival/index.htm


And for nuclear war survival skills this site is worth a bookmark

http://www.oism.org/nwss/index.htm