Sustainability of Nuclear Energy—A Critical Review of Closed Fuel Cycle Options

Ensuring economic supplies of secure, affordable and clean energy is a global sustainability challenge. Previous studies have shown that, on balance, nuclear energy, based on today’s dominant light water reactors with the once-through use of nuclear fuel, compares well with renewable energy technologies and so should be considered a sustainable energy source. However, the energy-producing nuclear reactor requires a complex infrastructure around it to produce the fuel and to deal with highly radioactive products. The end-to-end fuel cycle thus has significant implications when assessing the overall sustainability of nuclear energy and the “most sustainable” pathways for future nuclear energy. The simplest fuel cycle option is the Once-Through Cycle (OTC) with disposal of used nuclear fuels. More technologically complex options involve different degrees of closing the fuel cycle by recycling and reusing materials from the used fuels. This paper defines six options with different degrees of materials recycling—innovatively presenting them in the form of a “Tube Map” based on that of the London Underground system. The results of this critical review show that recycling has positive impacts on the use of natural resources, environmental footprint, management of high-level radioactive wastes, and energy security. Challenges to the acceptance of closed cycles, however, include safety, security, proliferation, and economics; but our preliminary analysis shows either that solutions exist or that they are not discriminating factors in the choice of fuel cycle. To address these issues, it is important to learn from past experience of implementing closed cycles, and this review looks at the United Kingdom as an interesting case study. Overall, it is concluded that whilst nuclear energy per se should be recognised as sustainable, when implementing the OTC, the development of closed fuel cycles should be considered as a strategic choice that can enhance the overall sustainability of the system. Lastly, an update to the “level playing field” analysis previously proposed for analysing different energy systems is made to account for the differences between different nuclear fuel cycle choices. The only factors that are worse for closed cycles than the OTC are the lower technological maturity (due to greater technological complexity) of closed cycles—particularly those with multiple recycling—and proliferation resistance and physical security (due to the separation of materials in closed cycles).