"Why did they only consider SMR?" is being asked by several people, so I'll paste this here:

2.4.4 Perceived inconsistency between high nuclear SMR capital costs and low-cost nuclear electricity overseas

Based on information to date, current nuclear SMR capital costs are significantly higher than any other technology included in GenCost. This result appears out of step with overseas experience where some countries enjoy low cost nuclear generation. There are two reasons for this seemingly inconsistent result.

GenCost has been advised by stakeholders that small modular reactors are the appropriate size nuclear technology for Australia. Australia’s state electricity grids are relatively small compared to the rest of the world and planned maintenance or unplanned outages of large scale nuclear generation would create a large contingent event of a gigawatt or more that other plant would find challenging to address. In the present system, it would take two or more generation units to provide that role. As such, large-scale nuclear plants which are currently lower cost than nuclear SMR, may not be an option for Australia, unless rolled out as a fleet that supports each other - which represents a much larger investment proposition.

The second issue is that observations of low cost nuclear overseas may in some cases be referring to projects which were either originally funded by governments or whose capital costs have already been recovered. Either of these circumstances could mean that those existing nuclear plants are charging lower than the electricity price that would be required to recover the costs of new commercial nuclear deployment. Such prices will not be available to countries that do not have existing nuclear generation such as Australia.

In summary, given overseas nuclear electricity costs may be referring to technology that is not appropriate for Australia, or assets that are not seeking to recover costs equivalent to a commercial new-build nuclear plant, there may be no meaningful comparison that can be made to Australia’s circumstances which is the focus of GenCost.

Source: The actual report, section 2.4.4 . Thankyou @fine_sandy_bottom@aussie.zone for the reference.