[qjh]

Obligatory not a nuclear safety or health physics person, but I am a particle physicist and I deal with radiation. CPM is a rather annoying unit because it doesn't convert to dose very well. If you have external 300 cpm (eg. hair), but all of that is in the form of alpha radiation, your actual dose is essentially zero.

It's worth noting that humans are typically radioactive to the level of 3 kBq, or 3000 disintegrations per second, so if I ever realised I had 300 cpm of radiation on my skin as measured by a device that is sensitive to alpha, beta, and gamma, I probably would just shrug and wash it off. Where it might be a problem is if I am dealing with only alpha and beta isotopes, and I'm getting 300 cpm on a gamma-sensitive detector, meaning that the _secondary radiation alone_ is 300 cpm.

(Realistically, I and the radiation safety officer overseeing whatever I was doing would be in serious trouble and have a ton of paperwork, but I just mean it in the abstract)

I mean, 10 grams of potassium has ~300 Bq (that is 300 disintegrations per second) of radiation, so I think I should be able to get my hair far more radioactive than 300 cpm on a beta-sensitive geiger counter if I just slather myself in low-sodium salt from the grocery salt. The salt might be bad for my scalp, I don't know, but the radiation is fine. My point here, though, is that I don't know what equipment the 300 cpm is measured with, what the thresholds are and what the window material is, and that can change things greatly, but my non-professional opinion as the wrong kind of doctor is that it's...probably not a big deal.

We've actually used KCl as a low-level radiation source before, and we joked that when the experiment is done we can just take it home and use it to season dinner.

[Brian_K_White]

Much more useful comment. Thanks buddy.