In response to Anonymous'comment of Feb 11, 2023.
UK military-industrial interests, including Rolls-Royce's submarine reactor division, control the "Made in UK" imperative of the submarine PWR series.
Also for US national security, commercial competition reasons and recognition of Rolls-Royce's industrial importance in the UK, the US appears unwilling to export whole US reactor designs, including the S9G. The US Government recognises the value of good relations with the UK’s Rolls-Royce given Rolls-Royce supplies many types of jet engines for US military aircraft, large UAVs and civilian aircraft.
Instead the UK and US use a halfway convention of incorporating some US S9G submarine reactor characteristics into the PWR3 "The Royal Institution of Naval Architects reported that it was likely that the UK [Rolls-Royce, the RN and MoD] was given access to the US Navy S9G reactor design used in their Virginia-class submarines".
As reactor sizes and other characteristics literally define new SSN types a new reactor for a new 2030-40s SSN using the "Astute" class name will not happen. The Rolls-Royce designed PWR3 (using some US intellectual property (IP)) is likely slightly larger in height/diameter and possibly length making for a larger SSN(R) carrying a different name.
RN sources indicate the SSN(R) will possibly be called the Victory-class "mainly from the heritage of still technically "in service"HMS Victory, of Trafalgar. "Victory" has not been re-used for a ship, or unit or our navy since before 1918. Other names are unavailable. The Dreadnought-class SSBNs are already re-using "Dreadnought, Valiant, Warspite and usingKing George VI". Re-used major names for new carriers Queen Elizabeth and Prince of Wales has already taken place".
Returning to reactors - increasing the chances a PWR3 “Core ?” version going into the SSN(R)-Victory class is that the UK is allocating huge financial resources into a slightly larger version of the PWR3 for future Dreadnought SSBNs, through to the late 2030s.
A slightly smaller version of the PWR3, able to fit into the smaller beam/diameter of the SSN(R)-Victory, will go into it from about 2040.
Anonymous is probably right in concluding the US cannot supply SSN hulls to Australia because the US is heavily committed to building Columbia SSBNs, and future Virginias [and I dare say SSN(X)s] for the USN.
Also valid is Anonymous'concern about excessive Australian reliance on SSN(R) Victory builder BAE as Australia's sole SSN supplier from 2023 into the 2050s. BAE will also be providing spares/upgrades, probably deep maintenance and Australian sovereignty defying reactor repairs until the 2080s.
Furthermore BAE is also involved in the Australia Hunter-class frigate program which is delayed and overbudget, partly owing to BAE marketing an immature Type 26 ship design.