Invited Paper IPF-MoA6
Sustainable Nuclear Energy Production and Nuclear Waste Management

Monday, October 15, 2007, 3:40 pm, Room 602/603

The world energy demand is increasing at a rapid pace. In order to satisfy the demand and protect the environment for future generations, future energy sources must evolve from the current dominance of fossil fuels to a more balanced, sustainable approach to energy production. The future approach must be based on abundant, clean, and economical energy sources. Therefore, because of the growing worldwide demand for energy and need to minimize greenhouse gas emissions, there is a vital and urgent need to establish safe, clean, and secure energy sources for the future. Nuclear energy is already a reliable, abundant, and carbon-free source of electricity for the U.S. and the world. In addition to future electricity production, nuclear energy could be a critical resource for “fueling” the transportation sector (e.g., process heat for hydrogen and synthetic fuels production; electricity for plug-in hybrid and electric vehicles) and for desalinated water. Nuclear energy must experience significant growth to achieve the goals of our future energy system. The most significant technical challenge that must be addressed to allow the necessary expansion is safe, secure, and sustainable nuclear waste management. The nuclear fuel cycle is a key concept when discussing a sustainable future for nuclear energy. The nuclear fuel cycle is a cradle-to-grave concept starting from uranium mining to fuel fabrication to energy production to nuclear waste management. At first order, there are two approaches to the nuclear fuel cycle. An open (or once-through) fuel cycle, as currently planned by the United States, involves treating spent nuclear fuel (SNF) as waste with ultimate disposition in a geologic repository. In contrast, a closed (or recycle) fuel cycle, as currently planned by other countries (e.g., France, Russia, Japan), involves treating SNF as a resource whereby separations and recycling of transuranics (TRU’s) in reactors work with geologic disposal. Open fuel cycles require multiple geologic repositories whereas closed fuel cycles can reduce the volume and toxicity of waste, conserve uranium resources, and provide additional energy. Nuclear waste management and lack of a closed fuel cycle are principal impediments to the future viability of the nuclear energy option. In the advanced, closed fuel cycles that are currently being developed in France, Russia, Japan, the United States, China, and India, SNF would be sent to a reprocessing plant where its major constituents are separated into several streams: a TRU stream, to be recycled, and several other streams, including a “clean” uranium waste stream (note that this uranium could be recycled as part of future nuclear fuels), and waste streams containing the fission products. The TRU’s are fabricated as fresh nuclear fuel, to be irradiated again in a fission reactor, ideally a fast-neutron system. Approximately 30% of the TRU’s are fissioned each time the fuel is irradiated in a low conversion-ratio fast reactor. The remaining 70% stay in the cycle until they are fully fissioned. Even a closed fuel cycle requires a geologic repository to dispose of long-lived fission products and potentially very small amounts of TRU’s, the latter being from minor separations process losses. The volume and toxicity of waste requiring geologic disposal is reduced significantly in a closed fuel cycle; however, the doses from the encased radionuclides still require long-term isolation in durable waste forms in geologic repositories. Engineering and technology development will improve the reliability and cost effectiveness of nuclear energy and closed fuel cycle approaches. However, the rapid expansion of nuclear energy technologies required to satisfy the needs of the future will require breakthroughs that will only be possible through a coupling of applied and basic science and engineering. In particular, advanced modeling and simulation tools and approaches integrated with engineering and facilities design will be the avenue for using basic science insights to further the prospects for sustainable nuclear energy and nuclear waste management.