Advanced Fuel Cycle Technology and Economics

  

• Nuclear Fuel Cycle
• Actinide Transmutation
• Flexible Conversion Ratio Fast Reactors

The Future of the Nuclear Fuel Cycle. MIT was the recipient of a grant from the Nuclear Energy Institute and the Electric Power Research Institute to conduct a three year study on the nuclear fuel cycle with an emphasis on what to do with the spent fuel. This study is patterned on the 2003 MIT study, "The Future of Nuclear Power," with a multi-disciplinary team across the Institute involved. The study is led by Professors Ernest Moniz and Mujid Kazimi. Other NSE faculty involved include Professors Apostolakis, Driscoll, Kadak and Golay.   Faculty members from other departments include S. Ansolabehere, S. Bowring, J. Deutch, T. Eagar, and J. Parsons. Dr. Charles Forsberg was hired as the Executive Director of the study, and Dr. Pavel Hejzlar is the staff member in charge of the fuel cycle system simulation effort. An external advisory committee with Phillip Sharp chairing has been constituted.
The objective of this multi-year study is to provide a deeper understanding of the credible options for managing the spent fuel from a growing nuclear energy deployment, considering not only reactor technologies, but also the entire fuel cycle: uranium resources; alternative fuel cycles with and without separation of various elements for recycle of fissile fuels; and waste management. The study explicitly considers a range of nuclear energy deployment rates, with a high end sufficiently large to meet a major fraction of the U.S. energy demand and address climate change concerns. The emphasis is on meeting U.S. energy needs but within a global context. Factors being considered in the study include economics, risk, nonproliferation, institutional structures, and technology readiness. The first year’s activities include a metastudy that will help frame critical questions for research in the following years.

System Analysis of Actinide Transmutation Options.  Professors Kazimi and Todreas and Dr. Hejzlar and their students are investigating thermal and fast-spectrum closed fuel cycles compared with the open fuel cycle regarding spent fuel management economics and proliferation resistance. Their work has shown that thermal reactors can be applied to reduction of actinide accumulation by transmutation of transuranics (TRUs), provided that suitable nonfertile materials are developed to host the TRU elements. The nonfertile fuel rods could replace 20 percent of an LWR assembly uranium dioxide (UO2) fuel rods, and that would lead to net destruction of transuranics. However, recycling of TRUs may need cooling intervals of about 20 years to limit the spontaneous fission neutrons during fuel manufacturing. In addition, the use of thorium hydride to host the actinides in PWRs is being investigated. The nuclear fuel cycle simulation code CAFCA has been upgraded with a more user-friendly acceptance of alternative advanced reactor options and also equipped with a more robust numerical scheme to estimate the appropriate rate of addition of advanced reactor capability. A system dynamics version was created to allow for built-in treatment of uncertainties. Work this year enlarged the number of fuel cycle options that can be simulated, including high burnup fuel, and mixed oxide recycling in LWRs as well as fast reactor with different conversion ratios. The validation of CAFCA against other system codes, such as DANNESS of ANL, VISION of INL and COSI of CEA is being pursued.

Flexible Conversion Ratio Fast Reactors. A group led by Professor Todreas and Dr. Hejzlar is developing within a DOE-sponsored project a flexible conversion ratio fast reactor system for time-dependent management of both fissile inventories and higher actinides. The focus of the design effort is on reactor core designs having two conversion ratios: (1) near zero to transmute legacy waste, and (2) near unity to operate in a sustainable closed cycle. Two liquid reactor coolant core candidates are selected for development and cross-comparison. The coolants are lead and liquid salt (as distinguished from molten salt containing molten fuel). Gas coolant core results from an ongoing MIT project and sodium results from Argonne National Laboratory work will be evaluated in comparison with the lead and liquid salt coolant core results. The feasibility of the lead-cooled reactor concept has been established for both conversion ratios, and the design of liquid salt-cooled cores is under development. The liquid salt-cooled concept was found to be more challenging to develop and required some innovative features to overcome neutronic and thermal hydraulic challenges. A patent application for the conceptual design of a liquid salt-cooled reactor that overcomes these challenges was submitted in June 2007.