Since the 2004 Energy Act, nuclear fission has rapidly grown, and continues to grow, in significance in the UK's Energy and Net Zero Strategies. Government's Nuclear Industrial Strategy states clearly that the nuclear sector is integral to increasing productivity, driving growth across the country and meeting our Net Zero target. Nuclear is, and will continue to be, a vital part of our energy mix, providing low carbon power now and into the future, and the safe and efficient decommissioning of our nuclear legacy is an area of world-leading expertise. In order for this to be possible we need to underpin the skill base. The primary aim of SATURN is to provide high quality research training in the science and engineering underpinning nuclear fission technology, focussed on three broad themes: Current Nuclear Programmes. Decommissioning and cleanup; spent fuel and nuclear materials management; geological disposal; current operating reactors (AGRs, Sizewell B, propulsion); new build reactors (Hinkley C, Sizewell C, possibly Wylfa Newydd; Future Nuclear Energy: Advanced nuclear reactors (light water reactors, including PWR3, gas cooled reactors, liquid metal cooled reactors, other concepts); advanced fuel cycles; fusion (remote handling, tritium); Nuclear Energy in a Wider Context: Economics and finance; societal issues; management; regulation; technology transfer (e.g. robotics, sensors); manufacturing; interaction of infrastructure and environment; systems engineering. It has become clear that skills are very likely to limit the UK's nuclear capacity, with over half of the civil nuclear workforce and 70% of Subject Matter Experts due to retire by 2025. High level R&D skills are therefore on the critical path for all the UK's nuclear ambitions and, because of the 10-15 year lead time needed to address this shortage, urgent action is needed now. SATURN is a collaborative CDT involving the Universities of Manchester, Lancaster, Leeds, Liverpool, Sheffield and Strathclyde, which aims to develop the next generation of nuclear research leaders and deliver underpinning (Technology Readiness Level (TRL) 1-3), long term science and engineering to meet the national priorities identified in Government's Nuclear Industrial Vision. SATURN also provides a pathway for mid technology level research (TRL 4-6) to be carried out by allowing projects to be based partly or entirely in an industrial setting. The consortium partners have been instrumental in a series of highly successful CDTs, Nuclear FiRST (2009-2013), NGN (Next Generation Nuclear, 2013-2018) and GREEN (Growing skills for Reliable, Economic Energy from Nuclear, 2018-2023). In collaboration with an expanded group of key nuclear industry partners SATURN will create a step-change in PhD training to deliver a high-quality PhD programme tailored to student needs; high profile, high impact outreach; and adventurous doctoral research which underpins real industry challenges.