Nuclear propulsion

Early submarines used petrol engines and later diesel engines to charge their batteries. The arrival of nuclear power in the 1950s, requiring no air to operate, freed submarines from the oceans surface enabling them to operate independently and unseen in their true environment.

The submariners ability to live submerged for long periods and the food that could be carried became the new limits on a submarines endurance.


  • Has supported continuous at sea deterrent since April 1968
  • Long-life core lasts the entire life of the submarine eliminating costly mid-life refuelling
  • Designed by Rolls-Royce on behalf of the MoD
  • Allows submarines to operate for long periods submerged only restricted by food on board
  • Each generation of reactor plant has seen improvement in stealth for the submarine
  • Two submarine types - Ship Submersible Nuclear (SSN) and Ship Submersible Ballistic Nuclear (SSBN)

Pressurised Water Reactor (PWR)1 - was the first reactor plant designed and manufactured by Rolls-Royce for the British nuclear submarine programme. Through its life it was regularly updated in the quest for improved performance with quieter operation. The design evolution spanned three reactor core designs, all designed and manufactured in Derby. The first core based on an American design was fitted to Valiant and Resolution classes of nuclear submarines.

PWR2 - The larger PWR2 plant was designed to meet the operational requirements of the larger Vanguard class submarines. The steady evolution in reactor design has culminated in the long-life core, which began shore based testing in 2002. The latest core has over six times the energy output and over four times the service life of the original PWR1 core. Long-life cores are fitted in the latest Astute class submarines - and there is a programme of back-fitting for the Vanguard class submarines.

PWR3 - This reactor design is being developed as part of the Successor programme to replace the existing Vanguard class of submarine. The PWR3 plant will a deliver huge improvement in terms of safety, integrity and availability, while at the same time reducing the through-life costs; a major part of the SEPP commitments made by Rolls-Royce.

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