from an outsider perspective as someone not in commercial nuclear power it is amazing that this hasn't been bloodier already. This is supposition on my part, but had this happened in the navy anywhere it would have been a major incident and then some. NIS probing bodily orifi etc.
Everyone can make mistakes and then some, even the brightest people are still people, but at this point how can anyone not "know" anything. someone is not coming forward for one of 2 reasons, fear or they did it deliberate.
I usually tell nubs, that its not the first mistake you make that gets you in trouble but what you do when you or someone realizes a mistake was made that counts. honesty can cover a lot of stupidity.
I am surprised that we haven't heard about this in the navy nuclear community yet but it wouldn't surprise me to discover administrative controls on metal working (drills, grinders, welding apparatus etc.) appearing in future maintenance periods.
the potential devestation if something like this had happened on a ship or sub would have been horrible. granted the hole as i understand it wasn't found until the pipe was refilled and that just wouldn't happen on a sub or ship because we dont drain primary piping like that as a routine matter.
either way, it makes me shudder.