If they are scheduled to do a major retrofit, it might be that the reactor is due to be replaced anyway. The area of subs I worked in was under the sail. It is kind of amazing how they can cut a huge hole in the pressure hull to move equipment in and out and then weld the piece back like nothing happened.
Used to be (on slightly older reactors for the S6G power plant), you replaced the core every other major overhaul.
This much damage?
I'd use use her for a new reactor training boat. Keep it pierside.