July 05, 2022, 11:58:06 PM
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Topic: gamma rays from various isotopes as a forensic tool  (Read 1311 times)

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Offline Babcock_Hall

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gamma rays from various isotopes as a forensic tool
« on: November 09, 2021, 10:32:51 AM »
https://doi.org/10.1073/pnas.1903481116

I teach a little bit of basic nuclear chemistry as it relates to forensic chemistry.  My textbook mentioned that the ratio of cesium-134 (at 605 and796 KeV)  to cesium-137 (662 KeV) and the ratio of iodine-133 to iodine-131 can be used to determine whether the cause of radioactivity was a nuclear bomb or the meltdown of a nuclear reactor.  It also mentioned that there was a handheld device that could be plugged into a cell phone that could be used in this regard but gave almost no specifics.  I did a quick search that turned up the paper above.  It deals with cesium-137 years after nuclear tests were done.

I am looking for a source of basic information that deals with how one identifies and quantitates various radioactive isotopes, especially these four; it seems plausible that the energy of emission is a characteristic property.  If the reading were too advanced for my class, I might be able to summarize it for them.

Offline Corribus

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Re: gamma rays from various isotopes as a forensic tool
« Reply #1 on: November 09, 2021, 11:14:05 AM »
I guess ICP-MS is gradually replacing traditional spectrometric methods of detecting fission products.

E.g., https://pubs.rsc.org/en/content/articlehtml/2017/ja/c6ja00334f , https://pubmed.ncbi.nlm.nih.gov/19542689/ , https://pubs.rsc.org/en/content/articlelanding/2014/ja/c3ja50291k etc.
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

Offline marquis

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Re: gamma rays from various isotopes as a forensic tool
« Reply #2 on: December 14, 2021, 08:47:37 PM »
From the look of it, they are using a wavelength dispersive XRF (WDXRF).  I've used many EDXRF and they don't have the resolution needed to tell the difference between the energies of different atoms ( ie 137 Cs vs any other Cs). It's been a while since I used a WD XRF,too.  But according to Wiki, their resolution has improved greatly over the last few years.

Offline Babcock_Hall

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Re: gamma rays from various isotopes as a forensic tool
« Reply #3 on: December 15, 2021, 08:16:48 AM »
marquis, Thank you.  I will look into this more.

Offline kriggy

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Re: gamma rays from various isotopes as a forensic tool
« Reply #4 on: February 21, 2022, 10:30:03 AM »
First, Im not convinced there is a "phone based" device for that. In my lab we have handheld radiation detectors with solid scintilator which are able to detect and measure around 7 various isotopes and price of one is around 10 000 USD. And they are size of clothes iron.

Im not 100% sure how the intrument they used works but looks like a portable gamma spectroscope. Im not really versed in how those work but they are able to detect the radiation with specific energies (which are given for each isotope)

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