Nearly all of Australia's population centres are on the coast, Alice Springs being the most notable exception with a population of around 25k. And most of Australia's population is loosely clustered on or near the east coast, which already has a somewhat interconnected power grid (emphasis on sort of).

I'm aware of the population distribution.

Only WA+NT are not connected to the national grid.

The problem with having a nuclear power plant on the coast where there's sufficient reliable water is that nobody wants one in their back yard.

(Yes there's parts of the WA/NT/QLD/SA coastlines where population drops to bugger all, but they're generally less suitable for all sorts of reasons)

Putting them inland where they're still near major interstate grid connections runs into the water problem again.

Which is a problem Canada doesn't have.

The water is closed loop right? Can’t you pump or even deliver the water by truck?

(Sorry if this is really ignorant)

I'm not a Nuclear Power physicist, but you can Google up images of a whole lot of them.

There's at least one common feature that you see in all of them - the giant cooling towers, often pictured emitting large white fluffy steam clouds while they're operating.

They're also all on massive permanent rivers, lakes or the ocean.

Pumping/Delivering water for that purpose is basically not feasible.