I suspect refurbishing decades old PWR reactors would be far more expensive than just building new ones, for example a SpaceX Merlin engine costs $1 million and a Blue Origin BE-4 costs $15 million. Nasa argued it would be 'cheaper' to reuse Shuttle components for the Space Launch System (SLS). Refurbishing Shuttle RS-25 engines has cost Nasa $50 million dollars per engine, restarting a production line is costing $100 million for each new RS-25 engine.
Wikipedia lists all 12 subs as having Rolls Royce Pressured Water Reactors.
Your PWR reuse idea is is kind of where Rolls Royce is looking to go with Small Modular Reactors (https://www.rolls-royce.com/innovation/small-modular-reactors.aspx).
I suspect refurbishing decades old PWR reactors would be far more expensive than just building new ones, for example a SpaceX Merlin engine costs $1 million and a Blue Origin BE-4 costs $15 million. Nasa argued it would be 'cheaper' to reuse Shuttle components for the Space Launch System (SLS). Refurbishing Shuttle RS-25 engines has cost Nasa $50 million dollars per engine, restarting a production line is costing $100 million for each new RS-25 engine.
Thanks