  Swift and deep decarbonisation of electricity generation is central to
enabling a timely transition to net-zero emission energy systems. While future
power systems will likely be dominated by variable renewables (VRE), studies
have identified a need for low-carbon dispatchable power such as nuclear. We
use a cost-optimising power system model to examine the technoeconomic case for
investment in new nuclear capacity in the UK's net-zero emissions energy system
and consider four sensitivity dimensions: the capital cost of new nuclear, the
availability of competing technologies, the expansion of interconnection and
weather conditions. We conclude that new nuclear capacity is only
cost-effective if ambitious cost and construction times are assumed, competing
technologies are unavailable and interconnector expansion is not permitted. We
find that BECCS and long-term storage could reduce electricity system costs by
5-21% and that synchronous condensers can provide cost-effective inertia in
highly renewable systems with low amounts of synchronous generation. We show
that a nearly 100% variable renewable system with very little fossil fuels, no
new build nuclear and facilitated by long-term storage is the most
cost-effective system design. This suggests that the current favourable UK
Government policy towards nuclear is becoming increasingly difficult to
justify.
