The CO is going to get Scrammed I'm pretty sure of that much. Of course, there's bound to be a catalog of errors about, starting with getting so close to shore, sounding equipment either not being checked or not working. There's a hundred different failures that could have accumulated to create this incident...but at the end of the day, HMS Astute is an SSN, SSNs aren't exactly good at shallow water ops, even in friendly territory. I've heard that a personnel transfer exercise had taken place just before she caught her rudder, so that explains why she was close to shore, probably practicing SBS deployment and recovery, but there's close and then there's too close, and the two are measured by success or failure...and in this case it was a very embarrassing failure.
In regards to radiologics, since she was a distance from the shore (close but not right in) I should imagine that anyone at the shore would have only received a very low dosage, particularly since only a third or so of the side was exposed. The tugs nearby might have got a bigger dosage but since they didn't really move in close until the tide was up, they might be alright, furthermore it's possible they scrammed the reactor and are running on diesels now. They certainly had the diesels on when stuck.
The latest reports indicate that she's able to make her own way back to Faslane, (again, probably on diesels) I'm not sure if Faslane has a drydock, I think it does but it's undercover (for the Vanguards) but I wouldn't be surprised if she spends at least the rest of the year in there undergoing strict hull testing.
Not exactly the shining start for our new attack sub, let's hope that Ambush does a bit better when she's finished next year.