Novel reactor designs to burn non-fissile fuels

Intellectual Ventures is leading a private initiative to explore new approaches to nuclear power. We have used advanced computational tools and modeling technology to reexamine some of the fundamental assumptions-such as the requirement for a continuous supply of enriched fuel-that have long driven the design of fission reactor cores. Our highest goal is to simplify nuclear infrastructure in multiple ways that will help fission power meet the world's growing need for affordable and sustainable energy by directly addressing the issues of emissions, proliferation resistance, safely, and long- term fuel disposal. Our concepts build on the ideas for a 'traveling wave' reactor (TWR) first presented by Edward Teller et al. in the early 1990's'. Initial work suggested that traveling-wave reactor designs could offer several important advantages over other fission reactor designs. After startup, for example, a TWR could run for its entire design life without refueling with fissile material or alternatively, might allow for refueling without a pause in operation. A TWR plant would also require little or no enriched uranium after an initial 'ignition' phase; instead it would burn natural uranium, depleted uranium (a low-cost byproduct of uranium enrichment), or possibly even thorium for most of its life. These advantages derive from the unique way in which a TWR burns its fuel. A nuclear deflagration wave is first formed using enriched uranium or some other fissile material. The slow-moving wave front is allowed to expand into adjacent sections of the core that contain only fertile material, where it breeds its own fuel and advances at a slow and self-limiting pace. The cost of energy delivered by LWRs has been increasing due to the rapidly rising cost of enriched uranium fuel. TWRs fueled primarily by natural uranium or depleted uranium (huge stockpiles of which exist) could, if widely deployed, extend the remaining economic resources of uranium from a century to several millennia. TWRs that burn thorium fuel would tap into an essentially unlimited resource: by some estimates, thorium reserves would be sufficient with such reactors to support the global population at energy consumption levels equivalent to the current US per-capita rate/or tens of millennia. We have performed integrated physics and engineering analyses of several TWR reactor designs, including those fueled by natural uranium, depleted uranium, thorium, and combinations of these. The various reactor concepts address distinct markets and applications, and each raises interesting engineering challenges. This paper includes illustrations and numeric examples of our progress to date and highlights some of the questions still to be answered about this fundamentally new approach to nuclear energy. (authors)