This study on transitioning from thermal to fast neutron nuclear systems was carried out under the auspices of the Committee for Technical and Economic Studies on Nuclear Development and the Fuel Cycle (NDC). It benefitted from previous and ongoing activities on scientific and technical aspects of transition scenarios undertaken under the leadership of the Nuclear Science Committee. Its main objectives were to provide insights on strategic and policy issues raised by the transition, and to draw findings, conclusions and recommendations for consideration by decision makers on the opportunities and challenges associated with the introduction of fast neutron systems in a fleet of thermal neutron reactors.

This chapter provides background information on the overall context of transition scenario design and implementation. The first section gives illustrative scenarios to serve as a backdrop for assessing the relevance of transition scenarios in a global energy supply perspective. The second section is a short overview on nuclear reactor and fuel cycle technology developments expected in the coming decades, indicating the types of nuclear systems which could be implemented when transitioning from thermal to fast neutron reactors.

According to the scenarios introduced in Chapter 2, nuclear power is likely to contribute significantly to energy supply in the world during the 21st century. Rising energy demand in developing countries, security of supply concerns in OECD countries, and, last but not least, increasing awareness of the need to alleviate the risk of global climate change will provide strong incentive to policy makers for considering the nuclear option. 

When evaluating alternative routes for nuclear energy development in the long term, policy makers should take into account the requirements for human resources, raw materials and services, R&D support and industrial facilities associated with each option considered. The transition from thermal to fast neutron nuclear systems raises policy issues to be identified at the early stage of designing scenarios for its implementation. Those issues have to be assessed during all phases of the transition period and when the fleet of nuclear reactors and fuel cycle facilities has reached the status targeted by the policy. This chapter reviews key topics deserving attention and aims at drawing findings on the best approaches to support decisions to implement or not transition scenarios and to do it successfully. It includes a short overview on relevant international initiatives highlighting their potential impact on facilitating the implementation of transition scenarios.

This chapter provides the key findings from illustrative scenarios developed and analysed in various studies, highlighting their respective goals, expected achievements and lessons learnt from the results in terms of strategic approaches and policy issues. 

Nuclear power provides a significant share (around 15%) of the world electricity supply today and will remain an important energy source for decades, irrespective of individual country decisions to phase out nuclear programmes or to increase the role of nuclear energy in their national policies. The fleet of nuclear units in operation at present is reliable and globally has very good safety and economic performance. Most plants built in the 1980s and 1990s are expected to have lifetimes exceeding 50 years. Simultaneously, new, advanced nuclear reactors and fuel cycles – most of which are based on fast neutron reactors operated in closed fuel cycles – are being developed with the objective of enhancing the safety, economics, sustainability, and proliferation resistance and physical protection of future nuclear systems.