Can a smoke detector presence be detected ?

[Externet]

Hi.

Smoke detectors containing Americium...  Can some gamma sensor discern if a house has one installed from 50 metres away ?  Can instead, a single Am pellet extracted from such smoke detector be detected from a distance ?

[Carrock]

35 minutes ago, Externet said:

Hi.

Smoke detectors containing Americium...  Can some gamma sensor discern if a house has one installed from 50 metres away ?  Can instead, a single Am pellet extracted from such smoke detector be detected from a distance ?

The Americium used in smoke detectors emits alpha particles which have very short range and can be stopped by a sheet of paper so not much hope detecting their radiation from a distance.

Smoke detectors can be detected from a distance in the form of Americium contaminated runoff from landfill sites where old smoke detectors have been dumped.

I have worked with these very cheap detectors and in practise the containment is far below nuclear industry standard.

 

[Sensei]

"The amount of americium in a typical new smoke detector is 1 microcurie (37 kBq) or 0.29 microgram."

 

[Carrock]

40 minutes ago, Sensei said:

"The amount of americium in a typical new smoke detector is 1 microcurie (37 kBq) or 0.29 microgram."

 

Alternatively, the amount of americium in a typical new smoke detector is only about thirty times the maximum permissible body burden.

From https://en.wikipedia.org/wiki/Americium-241

Quote

Although α-particles can be stopped by a sheet of paper, there are serious health concerns for ingestion of α-emitters. Americium and its isotopes are also very chemically toxic as well, in the form of heavy-metal toxicity. As little as 0.03 μCi (1,110 Bq) is the maximum permissible body burden for ²⁴¹Am......

Americium-241 often enters landfills from discarded smoke detectors. The rules associated with the disposal of smoke detectors are relaxed in most jurisdictions.

From https://en.wikipedia.org/wiki/Smoke_detector

Quote

The amount of elemental americium-241 is small enough to be exempt from the regulations applied to larger sources...

Some European countries, like France,^[23] and some US states and municipalities^{[24][unreliable source?]} have banned the use of domestic ionic smoke alarms because of concerns that they are not reliable enough as compared to other technologies.^[25] Where an ionizing smoke detector has been the only detector, fires in the early stages have not always been effectively detected.

The danger in each home is negligible, but there are many million ionising smoke detectors in landfill, where containment fails and groundwater is contaminated. Optical detectors are much better for domestic fires and IIRC not much more expensive.

[Externet]

1 hour ago, Sensei said:

"The amount of americium in a typical new smoke detector is 1 microcurie (37 kBq) or 0.29 microgram."

 

Thanks.  I will take that as  "The amount of americium in a typical new smoke detector is 0.29 microgram  with an activity of 1 microcurie = 37 kilobequerels (1.0 μCi  = 37 kBq)."

So, is the Am gamma portion too weak to be detected at distance ? 

---->  https://www.sciencedaily.com/releases/2018/04/180425120132.htm

Can the gamma radiation be 'funneled' towards a detector ?  -Say a lead funnel-  Does gamma rays bounce or are absorbed by Pb ?

[swansont]

35 minutes ago, Externet said:

Thanks.  I will take that as  "The amount of americium in a typical new smoke detector is 0.29 microgram  with an activity of 1 microcurie = 37 kilobequerels (1.0 μCi  = 37 kBq)."

So, is the Am gamma portion too weak to be detected at distance ? 

---->  https://www.sciencedaily.com/releases/2018/04/180425120132.htm

From the wikipedia link Carrock gave

"The α-decay energies are 5.486 MeV for 85% of the time (the one which is widely accepted for standard α-decay energy), 5.443 MeV for 13% of the time, and 5.388 MeV for the remaining 2%.^[7] The γ-ray energy is 59.5409 keV for the most part, with little amounts of other energies such as 13.9 keV, 17.8 keV and 26.4 keV.^[8]"

So 85% of the time there is a 60 keV gamma, the rest of the time it's even lower energy. These are pretty weak gammas, more easily attenuated than higher-energy ones.

35 minutes ago, Externet said:

Can the gamma radiation be 'funneled' towards a detector ?  -Say a lead funnel-  Does gamma rays bounce or are absorbed by Pb ?

Lead is used as a shield. Lots of electrons for the gamma to interact with. Gammas don't "bounce" very well. You can concentrate such photons but it's not easy.

https://en.wikipedia.org/wiki/X-ray_optics#Focusing_optics

 

[Externet]

Thanks.

I understand then,  that lead used as a gamma shield works by absorbing much more than reflecting the radiation.  OK.  'Funneling' or 'paraboling' would take gold surfaced mirrors to concentrate reflections.

From a DoD site :

"... a 60- keV gamma ray has a typical range of a 100 meters in air and might penetrate a centimeter of aluminum."...

 

And by total coincidence, found a lead 'funnel' being used :

Edited August 20, 2018 by Externet
Added info

[John Cuthber]

That's not a funnel, is it?

[swansont]

10 hours ago, Externet said:

Thanks.

I understand then,  that lead used as a gamma shield works by absorbing much more than reflecting the radiation.  OK.  'Funneling' or 'paraboling' would take gold surfaced mirrors to concentrate reflections.

From a DoD site :

"... a 60- keV gamma ray has a typical range of a 100 meters in air and might penetrate a centimeter of aluminum."...

 

And by total coincidence, found a lead 'funnel' being used :

You should link to where you found this.

But, as it is labeled as a collimator, what the lead is likely doing is preventing off-axis photons from entering the device. Like looking through a toilet paper tube. No magnification, just limiting the field of view.

[Externet]

Thanks, thought of that rule, but being text that can be long-string-entered in the search box to yield the source, did not.

  Sites are :

3-d at ----> https://www.acq.osd.mil/ncbdp/narp/Radiation_Data/Radiation_Detection_and_Measurement.htm

Page 2 at ----> https://med.uth.edu/radiology/files/2016/03/Lab7_Thyroid_Uptake.pdf

Edited August 21, 2018 by Externet

[swansont]

1 hour ago, Externet said:

Thanks, thought of that rule, but being text that can be long-string-entered in the search box to yield the source, did not.

  Sites are :

3-d at ----> https://www.acq.osd.mil/ncbdp/narp/Radiation_Data/Radiation_Detection_and_Measurement.htm

Page 2 at ----> https://med.uth.edu/radiology/files/2016/03/Lab7_Thyroid_Uptake.pdf

That second link tells you what the lead cone is for: 

"The lead collimator is placed in front of the NaI crystal for the purpose of defining an area from which the radiations will be detected (dashed arrows). When apatient’s thyroid is placed in front of this collimated area at a fixed distance from the detector, a reproducible geometry for consistent measurements is created."

Which is basically what I had said.