Complex sentence: Three propulsion options were considered for the successor to the UK Trident system-PWR2, PWR2b (a PWR2 derivative with improved performance), and PWR3, a new system based on a US design but using UK reactor technology.
Split into simpler sentences: Three propulsion options were considered for the successor to the UK Trident system-PWR2, PWR2b (a PWR2 derivative with improved performance), and PWR3. PWR3 a new system based on a US design but using UK reactor technology.