There is more to this than finding someone/somewhere to build the boats and training some nuclear submariners. Routes for these things exist and there is quite possibly room in the US or UK pipelines for enough Aussie trainees.
What does not exist is an Australian nuclear Regulatory Environment, because Australia has no civil nuclear base.
It will take a good time to sort out the legislation, train the (civilian?) Staff to replicate the role of the UKAEA or its US equivalent and for it to write some rules. The new body will have zero experience at start up and will need to borrow that from others.
There are a hell of a lot of non-trivial tasks to be done. Who will be the Rickover of dunnunder?
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