A number of nations over time have expressed an interest in having nuclear submarines (SSN), I was not aware Australia had such an interest. The RAN has a big problem already with manning its existing submarines, which has been in the public domain for sometime.

There a number of non-submarine components needed for an effective SSN operation, the most expensive ones being a shipyard and a waste facility. Even the UK has struggled at times, especially storing waste.

IIRC the really difficult component is recruiting, training and retaining key crew members, probably reactor operators.

Switching continent and seas for a moment Brazil has expressed an interest, if not requirement for acquiring SSN(s) and have held talks recently with the UK on what it really means.

One could argue that the opening of new basing facilities to the USA in Australia is a far better, cheaper strategic option that SSNs.