From what is available in the public domain, the Virginia’s S9G reactor was the first with “Convective Cooling” whereby the coolant fluid is able to pass through the reactor extracting heat and then rising vertically due to convection. The PWR3 is reported as having extensive technology from the S9G so it should also have this design feature. The S9G is reported to be able to generate sufficient power on Convective Cooling alone for the Virginia’s to achieve a comfortable cruising speed - higher speeds require the use of cooling pumps.
The PWR2 is an old design which doesn’t have this capability and it’s also considered to be outdated (less safe) in that it doesn’t have multiple cooling systems. For normal operations, the cooling pumps are running and, as most submarine captains want to have the ability to generate maximum power immediately, they run the reactor “hot” even when loitering at slow speed. In this situation on older submarines, the cooling pumps generate more noise than the propeller.
I have confidence that the AUKUS SSN (probably should be designated SSGN) will be a very good design utilising a lot of the technologies developed for the Dreadnought class and, with the British Government’s stated intention to accelerate the design and construction processes, this will also be a very good outcome for Australia. If the design is finalised earlier, construction at Osborne could start earlier which may mean that the acquisition of the 3rd Virginia submarine for the RAN would not be required. With what is happening around the world, we are definitely living in interesting times.
Last edited by Going Boeing; 6th June 2025 at 12:18.