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I'm kind of surprised that something this radioactive isn't pretty easy to hone in on with a good Geiger counter. Someone with better physics want to enlighten

I'm kind of surprised that something this radioactive isn't pretty easy to hone in on with a good Geiger counter. Someone with better physics want to enlighten me about ranges and sensitivity?

pfdietz 4y ago
You wouldn't use a Geiger counter, you'd want to use a gamma ray spectrometer. For example, a sodium iodide crystal doped with thallium (acting as a scintillator, connected to a photon detector) or semiconductor detector (large crystal of Si, Ge, or other materials, preferably of high atomic number.) The Geiger counter is filled with gas and will not effectively interact with gamma ray photons; the solid state detectors interact much more strongly with them, and (particularly the semiconductor detectors) have very good energy resolution, to spot the particular energy of photons from this particular radioisotope.
- skissane 4y ago
  One of these? https://georesults.com.au/product/radiation-solutions-rs-125-nai-gamma-ray-spectrometer-handheld/ https://georesults.com.au/product/radiation-solutions-rs-125... Or maybe even https://georesults.com.au/product/rs-350-backpack-human-portable-radiation-detector/ https://georesults.com.au/product/rs-350-backpack-human-port... I imagine they are both rather expensive.
  - car 4y ago
    Radiascan makes an affordable scintillation counter, the RadiaCode 101. https://radiascan.com/ https://radiascan.com/ A good intro to what it can be used for: https://www.youtube.com/watch?v=x1UZdLVlBXg https://www.youtube.com/watch?v=x1UZdLVlBXg
    - skissane 4y ago
      Link to their actual product page: https://radiascan.com/products/detector-of-ionising-radiation-gamma-spectrometer-radiacode-101-works-with-android-google-maps/ https://radiascan.com/products/detector-of-ionising-radiatio...
remus 4y ago
I guess it's one of those things where the intensity of the radiation is proportional to 1/d^2. If you're holding it in your hand it emits enough radiation to be very unhealthy, but as soon as you put some distance between you and it then it becomes very hard to detect.
- MengerSponge 4y ago
  That's why it's still lost. Cs-137 has a clear gamma emmision spectrum (which is to say it glows a unique color of high-energy photons), so you can scan and pick it up with a scintillation detector. Unfortunately, Cs-137 is one of the bits of waste generated as fallout from nuclear testing, and its half-life is 30 years, so ambient levels are generally not identically zero.
  - wkat4242 4y ago
    And South Australia (pretty close to the bidder is Western Australia) has seen nuclear testing at woomera missile range so it's pretty likely to have some contamination indeed.
    - Schroedingersat 4y ago
      There was also that time britain nuked just off the coast of WA without checking the fallout zone for people or warning the locals.
paranoidrobot 4y ago
Take a tictac candy. Now find a road that's about 1400KM (870mi) long and pick some random point on there to drop it. Wait a week for other passing traffic to disturb it, maybe get caught in a tire and sent even further astray. Now go find it, remembering that even with sensitive equipment, you might need to be a few tens of meters away to pick it up out of the background radiation.

I'm kind of surprised that something this radioactive isn't pretty easy to hone in on with a good Geiger counter. Someone with better physics want to enlighten me about ranges and sensitivity?

pfdietz 4y ago

You wouldn't use a Geiger counter, you'd want to use a gamma ray spectrometer. For example, a sodium iodide crystal doped with thallium (acting as a scintillator, connected to a photon detector) or semiconductor detector (large crystal of Si, Ge, or other materials, preferably of high atomic number.) The Geiger counter is filled with gas and will not effectively interact with gamma ray photons; the solid state detectors interact much more strongly with them, and (particularly the semiconductor detectors) have very good energy resolution, to spot the particular energy of photons from this particular radioisotope.

skissane 4y ago
One of these? https://georesults.com.au/product/radiation-solutions-rs-125-nai-gamma-ray-spectrometer-handheld/ https://georesults.com.au/product/radiation-solutions-rs-125... Or maybe even https://georesults.com.au/product/rs-350-backpack-human-portable-radiation-detector/ https://georesults.com.au/product/rs-350-backpack-human-port... I imagine they are both rather expensive.
- car 4y ago
  Radiascan makes an affordable scintillation counter, the RadiaCode 101. https://radiascan.com/ https://radiascan.com/ A good intro to what it can be used for: https://www.youtube.com/watch?v=x1UZdLVlBXg https://www.youtube.com/watch?v=x1UZdLVlBXg
  - skissane 4y ago
    Link to their actual product page: https://radiascan.com/products/detector-of-ionising-radiation-gamma-spectrometer-radiacode-101-works-with-android-google-maps/ https://radiascan.com/products/detector-of-ionising-radiatio...

remus 4y ago

I guess it's one of those things where the intensity of the radiation is proportional to 1/d^2. If you're holding it in your hand it emits enough radiation to be very unhealthy, but as soon as you put some distance between you and it then it becomes very hard to detect.

MengerSponge 4y ago
That's why it's still lost. Cs-137 has a clear gamma emmision spectrum (which is to say it glows a unique color of high-energy photons), so you can scan and pick it up with a scintillation detector. Unfortunately, Cs-137 is one of the bits of waste generated as fallout from nuclear testing, and its half-life is 30 years, so ambient levels are generally not identically zero.
- wkat4242 4y ago
  And South Australia (pretty close to the bidder is Western Australia) has seen nuclear testing at woomera missile range so it's pretty likely to have some contamination indeed.
  - Schroedingersat 4y ago
    There was also that time britain nuked just off the coast of WA without checking the fallout zone for people or warning the locals.

paranoidrobot 4y ago

Take a tictac candy. Now find a road that's about 1400KM (870mi) long and pick some random point on there to drop it. Wait a week for other passing traffic to disturb it, maybe get caught in a tire and sent even further astray. Now go find it, remembering that even with sensitive equipment, you might need to be a few tens of meters away to pick it up out of the background radiation.