This report assesses the role that nuclear energy can play in supporting the transition to a low-carbon energy system. It begins by considering the greenhouse gas emissions from the full nuclear fuel cycle, reviewing recent studies on indirect emissions and assessing the impact that nuclear power could make in reducing greenhouse gas emissions. The report provides estimates of the construction rates that would be needed to meet the projected expansion of nuclear power foreseen by many energy scenarios published by international organisations. It then assesses the economic, technical, societal and institutional challenges represented by such an expansion to identify the most significant barriers. The capacity of nuclear power plants to operate in an electricity system with a large share of renewables, and the impact of smart grid technologies are also examined. Finally, long-term prospects for nuclear energy are discussed in terms of development of new reactor and fuel cycle technologies, non-electric applications and new operational and regulatory constraints that could arise as a consequence of climate change.