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Radiation Sources

Posted: 22 Mar 2017, 04:06
by sgt_bear

I want to aquire radioactive excempt sources. I was looking and found "spectrum techniques" which seems to be a major supplier to a lot of hobbisty.

What i noticed, that they sadly do not have a "pure gamma" isotope.

Their page says Na-22 only emits gamma and xray ... sodium-22/

But if looking here, Na-22 does emit beta too ... NA&unc=nds

What informations is correct?
Is there a difference between beta,beta-,beta+ when talking about gm tubes, or do cause both types the same amount of clicks?

I want to aquire a set of sources for benchmarking GM tubes so i need alpha beta and gamma
For the alpha i have a smoke alarm
For beta i would get CD-109 (since it is the only short-lived isotope that emits mainly beta)

Re: Radiation Sources

Posted: 22 Mar 2017, 15:13
by Steven Sesselmann
Usually one uses Cs137 as a calibration source, it has a long half life so you don't have to recalculate the activity all the time.

Cs137 emits beta and gamma, but the beta particles will not go through a geiger counter unless it has a mica window, and if you want to stop the beta you just use a bit of plastic or metal foil.

Apart from the gamma at 662 KeV there are also the 32 keV x-rays and these can be stopped also with a thin sheet of lead.

Na22 can be a bit tricky, because it emits positrons which instantly annihilate and produce two diametric gamma rays at 511 keV, once again if you block the beta particles Na22 is a gamma emitter, but it's half life is shorter and the activity will fall over time.


Re: Radiation Sources

Posted: 22 Mar 2017, 19:18
by sgt_bear
I know about Cs-137.

Problem 1:

Sadly in Switzerland (where i live) things are very different. The exempt value of sources have two parts
LA - Quantity you can own without any paperwork (eg. 19uCi Cs-137)
LE - Quantity you can dispose legally into trash. (eg. 20 n! Ci of Cs-137)

So for long living isotopes, i would have to dispose the source into a rad-waste facility. For a 1" Disk, they would charge around 300-500$ :'(

With short-living isotopes, after 20 years or so, LE is reached by decay and the source can be wander into trash, that's why i cant use Cs-137

Problem 2
The Package must be not UN2910, since UN2910 will not transported by swiss post because it requires transport papers and must stay in a single vehicle. The IAEA for Cs-137 is 0.27 uCi, over that value it is UN2910.

If there are more isotopes than one in a package, the sum has to be calculated

activity1 / max activity1 + activity2 / max activity2
Mn54 10uCi/27uCi + Cs-137 0.25uCi/0.27uCi = 0.37 + 0.92 = 1.225 (Which is UN910 if greater 1.00).

Its very complicated tho... :(

So currently i possibly want to get the following:

Tl-204 - 0.1 uCi - Beta - Factor 0.37
Po-210 - 0.05uCi - alpha - Factor 0.18
Eu-152 - 0.1 uCi - Factor 0.095
Na-22 - 1uCi - Factor 0.037
Mn-54 - 5uCi - beta gamma - Factor 0.18
Cd-109 - 1uCi - beta low gamma - Factor 0.037
Co-60 - 0.25uCi - beta gamma - Factor 0.092

This would get a sum of 1.00, which is not UN2910
What do you thing of this selection?

Re: Radiation Sources

Posted: 22 Mar 2017, 20:46
by Steven Sesselmann

It is indeed very complicated, in fact most countries have crazy laws when it comes to radiation, many of these laws are cold war relics and make no sense from a health and safety point of view. At some point you have to make your own judgement and decide if you think owning a 1 µCi. calibration sample of Cs137 in the name of science, makes you a criminal.

One may be a criminal in the eyes of the state, but are they going to press charges?

I think these laws have to be understood in the right context. If you were manufacturing smoke detectors with 1 µCi. Cs137 sources, one could understand the 1 nCi rule, because that's about the minimum detectable amount.

Anyway it seems you have found a workable solution, which is good.


Re: Radiation Sources

Posted: 23 Mar 2017, 00:00
by sgt_bear
Actually the law about radiation isn't a big part of the problem, more the other factors.

I can totally legally own 19uCi of Cs-137 - but its about the price.


Disk Price - 150$
Shipping - 60$

Would make 210$ for a neat source ... but

Since our postal service does not transport any dangerous material (flammable etc)
I would have to organize a transport by a transport company from the airport to me

Transport Cost - at least 500$
Cost for Storing the packet till pickup : 50$

So in case the source needs to be disposed

Transport Cost to Waste Site : 500$
Waste site fees to put my source into a barrel with other sources: 300$

So in the worst case, the price of the source can stack up from 210$ to 1550$

My main problem here is the UN2910.
I would instantly buy a 10uCi Cs-137 if the IAEA Value be >10uCi instead of 0.27uCi. The source would have never to be disposed since it can just stay in my house all my life.
But over 0.27uCi it becomes IAEA rated UN2910 and transport trouble starts!

Re: Radiation Sources

Posted: 24 Mar 2017, 10:22
by Steven Sesselmann

Every time I ordered sources from Spectrum Techniques they package the source professionally so it complies with international shipping regulations for sending radioactive materials. The source is packaged inside a box centred inside another larger box, so that the exposure on the outside is below the set limit. Attached to the box is also compliance documentation showing what it contains etc. This is why the shipping is a bit higher I guess.

Why do you need a strong source?

1 µCi. is plenty to calibrate a gamma detector.


Re: Radiation Sources

Posted: 25 Mar 2017, 20:48
by sgt_bear
For Cs-137 i might get a vacuum tube containg it, since this is a "commercial item" it do not falls under laws.

About the strenght, i would like to have one strong source for rating GM tubes and study their dead-time error at high levels.

Re: Radiation Sources

Posted: 30 Mar 2017, 06:09
by Boris
Hi Jonathan,

Any special reason to use a beta source?
Many everyday household sources can be used to calibrate.

I personally use a watch and a smoke detector for calibration, as we are not allowed to have any radioactive material.
one other suggestion could come from some German gieger counters that have a internal C14 source DDR leger Type: TTL 6109A
It is an aluminium plate that measures about 2 x 2 cm, take care not to damage the foil of the source

I think you can buy the geiger counter for about 50 euro ;)

Cheers, Boris.