intentional Polonium 210 from decay chains
What do you mean "decay chains"? Po-210 decays to Pb-206 which is stable. So you mean Po-210 decay. Let's shut down the chemical industry because someone attempted to poison The Skripals. https://en.wikipedia.org/wiki/Poisoning_of_Sergei_and_Yulia_... .
medical mistakes
Spent nuclear fuel is generally not used for medical isotopes. They specially prepare samples for irradiation to not have to use reprocessing, e.g. https://en.wikipedia.org/wiki/Cobalt-60#Production .
I could have a look for you
It would be illuminating to see what you find reasonable.