# Radiation detectors



## tweederlee (Oct 16, 2013)

Does anyone have experience with any type so Geiger counter's or radiation detectors. Looking for recommendations. new or used. Brands etc.....


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## bacpacker (Jul 15, 2011)

I will look for some model numbers and brands to post. Hopefully I can locate some vendors as well.


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## tweederlee (Oct 16, 2013)

Awesome. Thanks. 


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## Tweto (Nov 26, 2011)

There are some very informative youtube videos available. Antiprotons is one channel that has numerous radiation detector consumer reports.


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## GrinnanBarrett (Aug 31, 2012)

Geiger Counters are very different from the traditional Civil Defense radiation meters you see advertised. I use the V-717 Civil Defense model. It has a remote wired base to read levels without going outside. The key to buying one is buy from a dealer who has had the unit calibrated and tested. I bought my last ones from JRH out of Georgia. I have known Robert for years and trust him to do me right. Be careful about sites selling surplus where the units may or may not even work. Calibration is a key element. Most of those use D cells for power. 

I have not priced them lately because I have had mine for years. 

A Geiger counter is a very expensive tool. The tube on the handle you use to check the potential radiation source is extremely expensive to replace.


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## bacpacker (Jul 15, 2011)

We used bicron units to check equipment and ourselves when exiting rad areas at work. You use a bear claw detector to look for Alphas, a smaller round detector for Beta-Gammas. They arent as useful for just a general area detector to alert you when something is around.

The Bicrons have been replaced with newer instruments now so there should a decebt used market available. They are built well and can take a beating. Calibrations are not to hard with the right equipment. Although, they tend to hold cal very well if you dont beat them to death. 

Still tryin to find a more area detector.


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## jeff47041 (Jan 5, 2013)

This is probably a stupid question. A few years ago, I was at a place looking at Geiger counters among other things. the guy had this straw looking thing that you're supposed to look through, and if it is calibrated and charged (?) it's supposed to tell you something. 

I can't for the life of me remember what it does or how it works. I can (and plan to) talk to him again this coming June. Figured you guys would know what I'm confused about...Anyone?


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## bacpacker (Jul 15, 2011)

That is a pocket dosimeter. It will show you how much exposure you have gotten. Work well, but have to be reset at some point or replaced. Old tech, new ones are electronic and keep Track of more stuff. Old ones work well and are pretty inexpensive.


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## bunkerbob (Sep 29, 2009)

*Rad meter*

I have several for different applications. The best for the price is the Radex 1503+, very accurate and easy to use and set-up. Use it to verify the other units also. I keep a pocket dosimeter in each car to monitor exposure, a recharger both battery operated and battery-less military grade units. For the shelter, a calibrated remote CD V-717 for exterior measurement and a CD V-700 a low level gamma detector with hand held mueller tube.
I use the discarded guts from a smoke detector to check meters, it contains Americium.
It's important when buying surplus survey meters that they have been recently calibrated.

A good source... http://www.radmeters4u.com/


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## LincTex (Apr 1, 2011)

Someone please correct me if I am mistaken...

But isn't a lot of math involved to use any of these devices correctly?

Some people "fixate" on the amount and/or level of radiation, but ignore time of exposure.

I'll need to do some more reading....

conversion calc: http://www.easysurf.cc/cnver24.htm

http://en.wikipedia.org/wiki/Roentgen_equivalent_man
is an older, CGS, unit of equivalent dose, effective dose, and committed dose. Quantities measured in rem are designed to represent the stochastic biological effects of ionizing radiation, primarily radiation-induced cancer. These quantities are a complex weighted average of absorbed dose, which is a clear physical quantity measured in rads. There is no universally applicable conversion constant from rad to rem.

The conventional units for dose rate is mrem/h

http://en.wikipedia.org/wiki/Sievert
It is a measure of the health effect of low levels of ionizing radiation on the human body.

Doses greater than 1 sievert received over a short time period are likely to cause radiation poisoning, possibly leading to death within weeks.

One sievert equals 100 rem. The rem is an older, non-SI unit of measurement.


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## xsquidgator (Dec 21, 2014)

*Health Physics for Preppers*

All right, something I can talk about. My background is ex-USN nuclear operator and current medical (radiation) physicist.

A simple Geiger counter aka Geiger-Mueller (GM) counter can be made to serve most emergency radiation surveying needs. FWIW, radiation emergencies are at the bottom of my priority list compared to civil unrest, zombie attacks, forest fires, hurricanes etc. (I live in Florida - I'd feel at home in a nuclear accident situation since I'm trained for that, but, in Florida, I think all that other stuff is much more likely than a radiation accident). 
GM counters are the simplest and least expensive ionizing radiation detectors I can think of. If you work with radiation on medicine or the industrial sides, there are other more exotic, more capable, and more expensive detectors available, but a GM as far as I'm concerned could give you an idea of most of what you care about: what's the general area radiation level, is there airborne radioactivity (particles of fallout) outside, how much is there, is the dose rate going up down or staying the same?

The person who said "there's math involved" is correct, or rather, as a minimum you have to interpret the results of the readings you take with your GM counter. I haven't bought one of these in a long time, since at work, the ones we have last and last and last and we haven't needed to replace or even repair them. If you buy one, you should probably send it off to be calibrated at least once (we're required to get them recalibrated every two years, when they're used for work). The handheld "survey meters" that you carry around aren't high-precision lab instruments imo, they're intended for field use and for telling if you have a problem or not.
A discussion of how to use one is going to be a bit involved... pm me or ask here if you have questions and I'll tell you my opinion on how to do what you want.

One other thing that's a personal axe of mine to grind: how much radiation is enough for you to worry about? That's a controversial question and not all the experts agree. But, I'll be glad to pass on some rules of thumb that are in the middle of the range of professional opinion and that most experts would agree are reasonable.

So, first assumption and some simple math: Dose = Doserate x time
Using the old school (not SI) units of radiation exposure and dose of Roentgens (R) and rads (no abbreviation).
Roentgens apply to x-rays and gamma rays only, and 1 R is the amount of x-ray/gamma rays needed to create 1 esu (electrostatic unit) of charge in 1 kg of dry air at STP. So, that's 1 Roentgen (R) of x-ray or gamma ray radiation.

The rad is a unit of radiation dose, whereas the Roentgen is a unit of x-ray/gamma ray "exposure". 1 rad is 1 erg per kg deposited energy. For our purposes, assume 1 rad of electrons (beta rays) or x-rays or gamma rays is equivalent to 1 Roentgen. That's not exactly true but it's accurate to within about 15% which is good enough for our purposes, ie determining if it's safe to go outside after something radioactive happened.

So, back to dose = doserate x time.
If you stood in a radiation field of 1 Roentgen per hour for one hour, you'd receive 1 R. From the preceeding paragraph, that would be equivalent to 1 rad, also. If you stood there for two hours, you'd get 2 Roentgen (2 R) or 2 rads. Half an hour, 0.5 R or 0.5 rads. With us so far?

The basic GM handheld survey meter we're talking about, which is pretty much the least expensive instrument you can get, reads out in terms of either "counts per minute" (CPM) or "Roentgens per hour". Remember your Greek prefixes, 0.001 R per hour is 1 mR per hour.
For most GM counters, about 300 counts per minute is 0.1 mR per hour (plus or minus a lot, which is why you get these things calibrated at a lab so that you can believe the readings it gives you).

So, dose = doserate x time.
What you want is to minimize your dose, if there's radiation outside or inside. You minimize your dose with time, distance, and shielding. Minimize the time you spend in an area with high or higher-than-desirable radiation levels, maximize your distance from the source of the radiation, and maximize the amount of radiation shielding between you and the source of radiation. Time-distance-shielding or TDS.

Assuming some sort of nuclear attack on a nearby city or a nuclear accident at a nearby nuclear reactor, your best way to use TDS is to leave. Don't put several feet or yards between you and the plume of radioactive fallout, put many miles between it and you! Failing that, if you can't leave or you're stuck at home or whatever, turn off your A/C unit and try to go to the deepest inside part of your house. Middle of the basement is best, use the earth itself as additional shielding from above-ground radiation.

I'm oversimplifying a number of things but time-distance-shielding is the main concept so far, that, and dose = doserate x time.

Last thing here before we take a break: how much radiation exposure is so much that you have to worry about it? 
An average person in the U.S. receives about 300 mrad per year just sitting around doing nothing, from cosmic rays, natural background radiation, and from x-rays and other radiation received as part of medical procedures. That's an average. Round that off and it's basically 1 mR or 1 mrad per day (we're assuming 300 mrad is about the same as 365 mrad or 365 mR. That's 0.365 R per year).

So, most of us get about 1 mrad per day.
US Federal and most US states regulate radiation exposure to the public to 100 mrad per year, or 0.1 rad/R. That's a regulation on how much radiation the linear accelerators and x-ray tubes I work with put out, you're not supposed to get more than that amount from them. You get 3x that amount from natural background radiation but we can't do anything about that...

Radiation workers, such as medical people who work with radiation, nuclear power workers, and other such people, are allowed to receive 5000 mR or mrad each year. That's about 10 mrad (mR) per week for 50 weeks a year.

So, member of the public may get up to 0.1 R per year. Radiation worker may get up to 5 R per year. Those are conservative, that is very very safe, figures. You're not supposed to get more than that unless you're receiving radiation therapy for cancer, but you could get a lot more than that and still probably be ok.

How much more could you get? Here's what we know using all of our experience since the Manhattan Project. (for further reading and details, lookup the BEIR-VII report, BEIR = Biological Effects of Ionizing Radiation report).

If you're whole body got a sudden dose of radiation (in a few seconds, minutes, or even a couple of hours) of...
10 rads, a medical lab could examine you and probably couldn't tell anything had happened to you.

25 rads, a medical lab could examine your blood work and would just possibly start seeing a reduction in some of your blood constituents, from damage your body took from the radiation exposure. You'd feel fine, and wouldn't know anything had happened to you, but the lab could just start to tell.

100 rads - this is enough dose (a sudden blast of dose to your whole body) that you'd begin to suffer "radiation sickness" within a few days, aka "acute radiation syndrome". You'd get diarrhea probably, from the damage your gut took, and your blood cell counts would drop as the bone marrow (which replaces blood cells) took some damage too. You'd get sick for a bit. If you get medical care, and especially if you're the only person this happened to and the hospital could focus it's care on you, you'd probably recover in 1-3 weeks and be fine afterwards. If you're younger/stronger/healthier, you'll probably shake it off faster. If you're old and/or already sick with something else, this might get a lot worst or even push you over the edge (like getting two different illnesses at the same time can).

450 rads - this is starting to be a lot of dose. We call this level of dose "LD50/30", that is, it's lethal to 50% of the people who get it, within 30 days. If you got this dose, you'd be even sicker than with just the 100 rads. If you're young, strong and healthy, your chances of shaking this off are better than 50%. If you're old or not health, not so much.

1000 rads - this IS a lot of dose. Basically 100% fatal within usually a few days to a week or so. There have been radiation accidents since the Manhattan Project where people got this much or more, and hardly any of them lived, even with the best possible medical care. If you get this much in a disaster situation, that's almost certainly it because the hospitals are all going to be busy with other problems.

So, back to your handheld GM counter. If it reads 1 rad per hour and you stood there for an hour, you'd get 1 rad. If you stood there for 1 day, you'd get about 24 rads. See where that is in the heirarchy of biological effects of various levels of radiation dose?

1 rad per hour is a LOT. If you took your calibrated radiation meter out into your backyard right now, it would read a lot less than 1 mrad (1 mR) per hour, in fact it probably read more like 5 or so micro-R per hour (0.005 mR per hour, if your detector could go that low which most GM counters can't).
You can get localized areas of increased radiation exposure near naturally-occurring sources of radiation, like granite countertops, fiesta plates, and even many ceramic tiles.
(anecdote - in the Navy on the submarine I was on, we did radiation surveys all the time just to make sure we had all the radioactivity from the power plant contained. The showers we used had these little square tiles that had naturally-occurring uranium and thorium in them, like the fiestaware plates, and you'd get quite a bit more than background radiation levels if you put the detector probe up against them. Doesn't mean it's dangerous, because the levels fall off very rapidly as you get even a few inches away from the tiles. Pretty cool, though.)

So, things to think about: dose = doserate x time. Time-distance-shielding. We talked about how to measure external radiation levels with a meter, and how to interpret the results with what would happen to you if you got X amount of dose.

We can talk about later here, if there's interest, in how to evaluate what radiation dose you'd get from eating/drinking/breathing food or water or air, respectively, that was contaminated with radioactive material. That's even more complicated if you want to calculate numbers, but there are some handy rules of thumb you can use to get an idea of how much radioactivity you need to be concerned about. Remember, you never ever get to zero radiation level, we're sitting in a background level of radiation right now from cosmic rays, naturally occuring uranium in the dirt under your feet, and even naturally-occurring Potassium-40 dose from the potassium in your very own bones!

PS - The assumption is made in the above text that 1 mR = 1 mrad. There is yet another unit of radiation dose called the "rem" or "Roentgen equivalent man". The correct term is that the rem is a unit of 'dose equivalent', which tries to account for differences in the biological effect of different types of radiation like protons, neutrons, gamma rays, electrons, and others. For our purposes, for gamma and x-rays, and for beta rays (electrons), 1 mR is about the same as 1 mrad which is about the same as 1 mrem.
Or, 1R ~ 1 rad ~ 1 rem. 1 mR ~ 1 mrad ~ 1 mrem.
Don't worry about the exact definitions of these, they're not identical but they're "close enough" for most purposes. Government regulations until about 20 years ago were written in terms of rem or mrem, making this assumption of 1 R = 1 rad = 1 rem.

PSS- The SI unit of radiation dose is the Gray (Gy). 1 Gray = 100 rads.
The SI unit of dose equivalent is the Sievert (Sv). 1 Sievert = 100 rem.
If you're watching news coverage of things like Fukushima, they usually report the SI units so you'll see things like mSv/hr rather than mR/hr or mrem/hr. Use the conversion factors above to determine the radiation levels in rads/hr or rem/hr.


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## bacpacker (Jul 15, 2011)

XSG, Very good discussion of radiation and how every thing relates. Best I've seen outside of work and yours is more understandable. Thanks


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## labotomi (Feb 14, 2010)

xsquidgator said:


> My background is ex-USN nuclear operator


F'in Nuke


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## xsquidgator (Dec 21, 2014)

*Correction on radiation units*

Correction to what I wrote above - the post above incorrectly states the definition of the radiation unit "rad".
One rad is 100 ergs of energy deposited per gram.
100 rads is still 1 Gray (Gy), and 1 Gy is still 1 Joule/kg.
(I was going by memory and eventually realized I mis-spoke)

Merry Christmas to all!


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## Jason (Jul 25, 2009)

Here's a little radiological humor:


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## xsquidgator (Dec 21, 2014)

labotomi said:


> F'in Nuke


I wore the f'in nuc badge with pride!
Only two types of men on this boat, the nukes and the pukes. Which one are you? I don't see a CaF TLD on you, so you must be a puke!


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## labotomi (Feb 14, 2010)

xsquidgator said:


> I wore the f'in nuc badge with pride!
> Only two types of men on this boat, the nukes and the pukes. Which one are you? I don't see a CaF TLD on you, so you must be a puke!


Two things you should learn on this forum is not to make assumptions about anyone (you'll be wrong more often than right) and to not be easily offended (especially at good natured ribbing)

Turned in my TLD in 99 after 9 years of service.


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## xsquidgator (Dec 21, 2014)

labotomi said:


> Two things you should learn on this forum is not to make assumptions about anyone (you'll be wrong more often than right) and to not be easily offended (especially at good natured ribbing)
> 
> Turned in my TLD in 99 after 9 years of service.


It was only meant as good-natured ribbing, didn't mean it any other way. I spent 1/2 my time up forward. :laugh:
One of my hardcore nuc buds used to say that in a DI tone of voice and that's what I was thinking of when I typed it out.


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## labotomi (Feb 14, 2010)

xsquidgator said:


> It was only meant as good-natured ribbing, didn't mean it any other way. I spent 1/2 my time up forward. :laugh:
> One of my hardcore nuc buds used to say that in a DI tone of voice and that's what I was thinking of when I typed it out.


It's all good. 
The term "forward" leads me to ask, SSN or SSBN?


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## Jason (Jul 25, 2009)

My career has allowed me to cross paths with a few active duty USN submariners. A couple of them are at sea right now, through Christmas. I never served myself. In short, thanks for serving, fellas.


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