I'm sure lots of people know about this, but I only learned about it today, and on reflection it makes sense.
Apparently, there is some kind of medical scan which entails having some kind of radio-isotype ingested into your body. The pictures/scans are then taken and you go to sit in a waiting room.
Now, presumably for elf 'n safety reasons, you can't leave until you have passed this radioactivity out of your body. Fortunately, it comes out in pee.
BUT it does mean sitting around for a bit, feeling groggy, and peeing in a particular loo which is regularly checked to see how radioactive it is.
Now ladies, of course, generally sit down to pee, so they tend to get it into the bowl.
Men, on the other hand, seem to have an overwhelming urge to spray all over the place, even when aiming straight into the bowl.
So on the days when that loo is in use for its de-radioactivity duties, it is geiger-counted, swabbed out, and the remains put into a special safe.
Now I'm not sure what exactly happens to the safe, but I assume it is taken away and dealt with and a new one put in it's place.
All I can say is I don't want to be the one to open it.