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LAN_403

Conundrum

Sun Apr 20 2008, 11:57AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062

OK, here goes.

I obtained the cheapest, nastiest B&Q El Crapola (tm) camera I could find. First tested it to make sure it worked :) then after determining it had the open sensor format inside a hermetic case, removed the bare PCB. Under the lens (accessible using screws) I found a bare sensor attached with wires.

Sealed up the edges of the sensor with epoxy to prevent damage and provide a mounting surface (you can skip this step if you like), then epoxied a piece of the thinnest mica I could find over it. Retested to see if it worked, then silver painted the mica to elliminate light and allow alpha particles through. Sealed up rest of camera PCB in opaque epoxy although a box would also work here (even the light leaking through the PCB caused issues!)

You may have more success with a piece of pyrolytic graphite, haven't tried this but it should work just as well and be mechanically tougher.

I hooked up a basic particle counter using my 'scope and observed peaks when alphas and gammas hit the sensor. With an opamp or simple buffer and a sync separator (or else you get pulses at 50Hz and 15625 Hz) it would make a basic low power Geiger counter, providing both spectrographic information (alphas give a different pulse "height" than gammas) and direction/position information.

See

Dragon64

Wed Apr 23 2008, 01:04AM

Registered Member #1438 Joined: Sat Apr 12 2008, 12:57AM
Location: Canada
Posts: 218

I've just noticed that my Geiger Counter detects Photon rays and hard beta-rays. I have been working with Americium 241 which mainly releases Gamma Rays for several days now. I tested the Am 241 with my Geiger Counter and thought it was safe to study after observing that there were a few Micro RÃ¶etgen. I have so far handled the Am using a steel tweezer.

Im afraid that the gamma rays had been invisible to my Geiger Counter and need advice on what to do.

Backyard Skunkworks

Wed Apr 23 2008, 01:17AM

Registered Member #1262 Joined: Fri Jan 25 2008, 05:22AM
Location: Maryland, USA
Posts: 451

"Americium-241 emits alpha particles and low energy gamma rays (60 keV, giving a dose at 1 metre of 0.0011 mSv/yr). The alpha particles are absorbed within the detector, while most of the gamma rays escape harmlessly. The americium is present in oxide form in the detector."

Dragon64

Wed Apr 23 2008, 01:42AM

Registered Member #1438 Joined: Sat Apr 12 2008, 12:57AM
Location: Canada
Posts: 218

Thanks, Backyard Skunkworks. I was a bit scared about being irradiated. It even said that eating it wont pose much danger since the body cant absorb it.

PS. $1500 per gram for Am 241? They said they produce several kilo per year totals up to $ 1 500 000 per kilogram. Wow thats a lot of money.

Backyard Skunkworks

Wed Apr 23 2008, 05:37AM

Registered Member #1262 Joined: Fri Jan 25 2008, 05:22AM
Location: Maryland, USA
Posts: 451

I still wouldnt be treating the Am-241 as totally safe, I'm just saying don't be freaked out just because there is some radiation. Just don't eat it

And I donno when bombarding Plutonium is gonna get cheap, whoever does it must have a real corner on the market.

EEYORE

Wed Apr 23 2008, 05:43AM

Registered Member #99 Joined: Thu Feb 09 2006, 06:10PM
Location: florida, usa
Posts: 637

hydraliskdragon wrote ...

Thanks, Backyard Skunkworks. I was a bit scared about being irradiated. It even said that eating it wont pose much danger since the body cant absorb it.

PS. $1500 per gram for Am 241? They said they produce several kilo per year totals up to $ 1 500 000 per kilogram. Wow thats a lot of money.

Its actually pretty cheap. A kg of that stuff is a HUGE amount! Would also be extemely dangerous. There were some auctions online selling 75uC of Am 241 for about 60$.
Did anyone mention brazil nuts?They are radioactive...Slightly. Radon is also present in the home, but likely wont be detected by your meter unless it has built up over a few days. Some older lantern mantles are also radioactive by a good bit! They are thorium doped.
Matt
Matt

Bjørn

Wed Apr 23 2008, 07:35AM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

Americium-241 emits alpha, beta and gamma radiation. The alpha radiation is not muct to worry about it since it does not really penetrate your skin. So unless you inhale it as dust or manage to keep it in your body it does not do much damage. The beta radiation will penetrate your skin and damage cells and DNA. My not very efficient CCD detector registers about 3 events a second which means that there is not a lot of beta particles escaping but there are some. The gamma radiation will pass through all practical shields so you just have to accept it but luckily the energy is low enough not to be of much concern.

As long as the button is undamaged you can consider it safe. It is common sense to store it safely at least a metre away from where people normally stay. This is quite important if you don't know exactly how much radiation your source emits.

Seoul_lasers

Sun Aug 17 2008, 04:07AM

Registered Member #1630 Joined: Sat Aug 09 2008, 11:36AM
Location: Seoul Korea
Posts: 115

BjÃ¸rn wrote ...

Americium-241 emits alpha, beta and gamma radiation. The alpha radiation is not muct to worry about it since it does not really penetrate your skin. So unless you inhale it as dust or manage to keep it in your body it does not do much damage. The beta radiation will penetrate your skin and damage cells and DNA. My not very efficient CCD detector registers about 3 events a second which means that there is not a lot of beta particles escaping but there are some. The gamma radiation will pass through all practical shields so you just have to accept it but luckily the energy is low enough not to be of much concern.

As long as the button is undamaged you can consider it safe. It is common sense to store it safely at least a metre away from where people normally stay. This is quite important if you don't know exactly how much radiation your source emits.

Having HAZMAT training and knowledge about Radioactive materials and storage, Americium(241) an Isotope of Plutonium 241. IT IS an Alpha and Gamma emitter ([u]not beta[/u]). MOST of it's radiation is highly ionizing Alpha particles, there are then 4 or so bands of Gamma photons which are ranging mid-high energy.
The amount of Am241 in a smoke detector is approx 0.2ug or 37 Kbqs of activity. It is also in a relatively inert oxide form on the source in the smoke detector. I personally own a few 10uCi test sources for my custom geiger counter/scintillation detector - 2 in one unit.

I have handled sources that are MUCH MUCH larger for metallurgical testing in the military, (hull/armor testing) and trust me those are pure and up to several mCis. When I handled it was stored in a 100kg "lead pig" the outside was clearly marked DANGER RADIOACTIVE MATERIAL (Class 7 RADIOACTIVE III)... even on the outside of the pig the gamma was over 1 mR/hr even at over 1 Meter away. I cannot imagine how many CPMs of Alpha would be present but I would guess Billions of CPM.

Large Am241 sources can also be found in soil moisture density meters which are strictly licensed by the NRC.

Seoul_lasers

Sun Aug 17 2008, 04:30AM

Registered Member #1630 Joined: Sat Aug 09 2008, 11:36AM
Location: Seoul Korea
Posts: 115

hydraliskdragon wrote ...

I hope that I put this thread in the right spot.

Well yesterday, my Kvarts DRSB-88 Geiger Counter finally came. When I turned it on, its been acting strange so I went online to look for a good household item that emits a fair bit of Microroentgen to test out the counter. I went to dozens of websites but said that the only source of household radiation was :
Radon Painted watches
glass containing Uranium Oxide
and an Americium fire detectors.

I dont have this so im looking for others sources. Help?

The other source was Thorium for camping lantern mantles, which are still around. Coleman and a few other companies still produce them. These are quite radioactive. 1-2mR/hr each Beta(eqv)

Your counter will click every so often due to background radiation this is normal geiger counter activity. If you have turned it on and it sounds like a rainstorm, you either have a damaged counter (tube??) or you are in trouble.
Depending on where you live you will have low or high CPMs up 40CPM can be normal. higher than that and you are looking at radon from soil. Many places in the mid west US and southern England have VERY high % of Uranium in the soil and this makes for more CPMs

aonomus

Sun Aug 17 2008, 04:39AM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

I would imagine a whole kg of am-241 would be damned radioactive, at that point you *must* be getting some sub-critical reaction of some sorts, if not worse -.-

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