Well if that's how the Navy is, then that's how it is. I was MOS 55R in the army and that's not how how we do it. Then again I was not a 55G which (was) the nuke guys. Maybe they have excessive rules, maybe not.
As for n activation of (pure) water that either the O which is harmless or the H which is almost too obvious or playing games with contaminants. Nobody uses pure water as a coolant other than maybe training/experimental/university reactors, so there's the chemical shim system (and its inevitable contaminants). Or simple mechanical contamination like household dust essentially. Or corrosion (however slow) of non-bulk parts of the reactor, iron, carbon, and chromium from the walls are irrelevant but copper ions from slowly corroding cabling or something. Good luck being nearby the ocean and not having detectable chloride ion concentration, however low. Or dissolved nitrogen from the air, argon etc from the air. Sealing/gasketing material incredibly slowly corroding away. There's more to stainless steel than just Fe/C/Cr so if you corrode enough of it... Not much other options, its a pretty highly controlled area.
I'm not trying to be cloak and dagger, otherwise I wouldn't have mentioned that a civilian trained nuclear physicist can tell you the exact answer.
However I do not have CG-RN Rev 3 completely memorized and I no longer have access to it, so unless I know for sure something is not NNPI or otherwise protected by the Atomic Energy Act then I don't discuss it. Not that I don't agree that it's pretty crazy that someone who's never been in the Navy could go and look at Wikipedia and discuss it with someone else and be just fine but that the person who's been in the nuclear Navy cannot... but then I've never attributed "common sense" to the military.
With all that said, you haven't hit on exactly what I'm talking about (not that oxygen activation isn't cool). I will say the actual answer is pretty mundane, not at all cloak-and-daggery.