Going_Boeing,
As I understand the original PWR2 reactor is no longer in production and has rep been replaced with the PWR3 based around S9G with thirty percent fewer parts as planned for use in the Dreadnaught class - and the last of the currently planned Astute.
And, of course, the SSNR…
https://www.navalnews.com/event-news...ack-submarine/
https://en.wikipedia.org/wiki/Rolls-Royce_PWR#PWR3