Rolls-Royce PWR

The Rolls-Royce pressurised water reactor (PWR) series has powered the Royal Navy's nuclear submarines since the Valiant class, commissioned in 1966.

[2] The United Kingdom's first nuclear-powered submarine HMS Dreadnought, commissioned in 1963, was powered by an American Westinghouse S5W reactor, provided to Britain under the 1958 US-UK Mutual Defence Agreement.

[10][11] Rolls-Royce Marine Power Operations at Derby was the centre for design and manufacture of the UK's submarine reactors, and remains so today.

[13][15] In January 2012 radiation was detected in the PWR2 test reactor's coolant water, caused by a microscopic breach in fuel cladding.

[16][17] In February 2013, the Ministry of Defence (MoD) awarded Rolls-Royce a £800 million ten year "foundation" contract to "deliver and maintain" the reactors of the Astute-class and the Vanguard-class replacement the Successor.

[18][19] In February 2019, the MoD awarded Rolls-Royce a £235 million three year contract for Nuclear Propulsion Lifetime Management for the Trafalgar, Vanguard and Astute classes.

[22][23] The Royal Institution of Naval Architects reported that it was likely that the UK was given access to the US Navy S9G reactor design used in their Virginia-class submarines.

[30] In June 2012, the MoD awarded Rolls-Royce a £600 million contract to produce reactors for the Dreadnought-class and also for the final boat of the Astute-class HMS Agincourt.

[32][33] In 2025, the MoD awarded Rolls-Royce a £9 billion eight-year contract, named Unity, covering research, design, manufacture, and support for Royal Navy nuclear submarine reactors.