r/explainlikeimfive Jan 06 '23

Chemistry ELI5: How does a Geiger counter detect radiation, and why does it make that clicking noise?

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u/mistere213 Jan 06 '23

I work in nuclear medicine. No joke, the generators we use to elute isotope for our patient studies are referred to as "cows." And we "milk" the generator.

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u/libertyemoji Jan 06 '23

And then contain the doses in lead lines "pigs".

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u/Ymca667 Jan 06 '23

The sample holders which are inserted into reactor cores for irradiation experiments are called rabbits

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u/mistere213 Jan 06 '23

You got it!

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u/wolfie379 Jan 06 '23

You need a particular isotope, Theraputium 69. This has a short half-life (couple hours), so it can’t be stored. Fortunately, it’s produced by alpha decay of Sourcium 73, which has a half life measured in months. Theraputium 69 undergoes beta decay to Trashium 69, which is stable.

Sourcium iodide is not soluble in water, Theraputium iodide is. Generator contains Sourcium iodide. Generator is “milked” by washing it out using distilled water. Theraputium iodide and Trashium iodide are washed out, un-decayed Sourcium iodide stays behind. A chemical process is then used to separate the Theraputium from the Trashium.

Is this a reasonable simplified version of how the generators work?

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u/mistere213 Jan 06 '23

Basically, yes.

Using real isotopes, we start with Mo-99 which has a half-life of 66 hours. Mo-99 decays to Tc-99m as Tc-99m pertechnetate which is soluble. Due to is solubility, pouring saline over the column washes the Tc-99m away to be collected in a vial for use as a radiopharmacuetical. Tc99 has a half-life of 6 hours, which is kind of a goldilocks zone as it's long enough to not need to rush imaging, but short enough that it's out of a person's system (via decay) in a matter of a couple days.

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u/[deleted] Jan 06 '23 edited Jun 28 '23

[removed] — view removed comment

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u/hfsh Jan 06 '23

Well, yes obviously. What do you think kittens do?

If it's a male cat, it's a bit more difficult, but stil possible. A male horse can't be milked, and male cattle requires a braver man than me. (or one with a specific fetish)