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GeneralAmericium 241

30th Oct 2016 20:15 UTCEls Srn

Hi everyone!

I like to experiment with old gieger counters that I buy online.

For test them I use a small source (smoke detector) of Americium 241. For the last year I kept it in a sealed plastic box covered in aluminium foil. When closed, I could measure around 0.150 uSv/h (on top of the background radiation) only when the pancake detector was directly on the box, raising it 10cm or more and it would detect only background. Also in the room where I keep the box there is no change in radiation levels. I did a 24 hours CPM count.

I read online that the alluminium foil isn't necessary; alpha particles are easily stopped by air or just plastic. I also read that the alpha radiation creates neutrons when striking alluminium and this got me worried. Did I get a dangerous dose of neutrons??

Can someone clear this up?

Thanks!

31st Oct 2016 09:52 UTCŁukasz Kruszewski Expert

Hi. 0.15 mSv/h is OK. As far as I remember, the dose allowed for, lets say, "geology workers", is even more than 2. What is important here is the amount of americium - it is extremely tiny; also, these americium-bearing detectors are for house-hold use and they simply can't be dangerous (unless you collect some kilos of those, as the famous "Radioactive Boy" :-)); the most dangerous radiation is the alpha radiation, which is indeed stopped by both aluminium and even a paper sheet. Aluminium is indeed not the best cover for radiation, but again the amount is very tiny.

31st Oct 2016 10:35 UTCDavid Hospital

Hi Lukasz,

Only by curiosity, do you know how much it is "a very tiny amount" in an Americium smoke detector ? Is in the order of mg Am or maybe at microgram Am levels ?

Many thanks

David

31st Oct 2016 13:46 UTCSteve Hardinger 🌟 Expert

If the isotope was potentially dangerous in smoke detector quantity do you think smoke detector would be readily available?

31st Oct 2016 17:40 UTCRay Ladbury

The Am-241 in a typical smoke detector is well under 1 microgram. And yes, the doses you note are probably safe. However, the goal should be keep doses ALARA (As Low As Reasonably Achievable). Also, there is a huge difference if somehow you ingest the radioactive isotope--particularly into your lungs.

31st Oct 2016 18:06 UTCŁukasz Kruszewski Expert

I think is is even given in picograms (or micrograms), but I am not an expert here; but definitely not mg

31st Oct 2016 18:14 UTCŁukasz Kruszewski Expert

OK, checked; Wiki says: 0.29 microgram; that is very tiny amount....

31st Oct 2016 18:42 UTCEls Srn

Hi guys,

Thanks for the answers.

My concern was only about the eventual neutrons production by the alpha particles hitting the alluminum foil.

31st Oct 2016 19:58 UTCRonald J. Pellar Expert

Sine your aluminum foil was outside the plastic, the alpha particles never got to it!

1st Nov 2016 08:42 UTCDavid Hospital

Hi Ray and Lukasz,

Many thanks for your answers !.

David

1st Nov 2016 12:07 UTCŁukasz Kruszewski Expert

No problem (-;

1st Nov 2016 16:08 UTCEls Srn

Ronald J. Pellar Wrote:

-------------------------------------------------------

> Sine your aluminum foil was outside the plastic,

> the alpha particles never got to it!

The alluminum foil was inside the box. On top of the button of Am-241 there was a thin amount of adhesive putty (the one you use on walls for stick photos) and on top of that a big chunk of folded alluminum sheets.

1st Nov 2016 19:59 UTCŁukasz Kruszewski Expert

I think this is still a matter of the tiny amount of Am.

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