So if HEU rods will be returned to the UK - what other waste is there to dispose of?
Low and intermediate waste, as per my link 2 above. For ILW you’re talking about the reactor pressure vessel and associated steam pipe work etc.
If the promises to the IAEA are observed, then the reactors will - as a minimum - have to be defuelled in the USA/UK. It would then be possible to transport the boats back to Australia for long term storage and dismantling.
https://www.gov.uk/guidance/submarin...ntling-project
“….UK submarines are powered by nuclear reactors. During submarine operations, nuclear reactions cause radioactive substances to be generated in the pipework and components within the reactor compartment. This requires managing after the submarine leaves service.….
Once the nuclear fuel is removed and transported to Sellafield for storage the submarine can formally enter the SDP
.…
The three-stage dismantling method allows the less hazardous parts of a submarine’s nuclear reactor core, known as Low-Level Radioactive Waste (LLW
) to be removed first, followed by removal of the Reactor Pressure Vessel which is classed as Intermediate Level Radioactive Waste (ILW).”