Both nuclear power and gas with carbon capture and storage (CCS) technology are vastly more expensive than solar PV on capital costs alone. The very long construction timelines for nuclear power also rule it out of a scenario that involves rapid decarbonisation of the stationary power sector.
Because variable renewables are already cheaper to build than fossil fuels and getting cheaper every year, most plausible scenarios for Australia’s future assume they will make up a much higher proportion of the generation mix. Baseload generators like nuclear power are very slow to ramp up and down and lose their owners’ money when they’re not running, making them a poor match for an electricity system with a high proportion of variable renewables. What’s needed is electricity that can be dispatched on short notice to meet peaks in demand or drops in supply and that provides the right kind of grid-stabilising services, such as batteries.
(Source: A Plan to Repower Australia)