Westinghouse Electric Company (referred to as “Westinghouse” in the rest of this paper) is
proposing a "back-to-front" approach to overcome the stalemate on nuclear waste management
in the US. In this approach, requirements to further the societal acceptance of nuclear waste are
such that the ultimate health hazard resulting from the waste package is “as low as reasonably
achievable”. Societal acceptability of nuclear waste can be enhanced by reducing the long-term
radiotoxicity of the waste, which is currently driven primarily by the protracted radiotoxicity of the
transuranic (TRU) isotopes. Therefore, a transition to a more benign radioactive waste can be
accomplished by a fuel cycle capable of consuming the stockpile of TRU “legacy” waste
contained in the LWR Used Nuclear Fuel (UNF) while generating waste which is significantly
less radiotoxic than that produced by the current open U-based fuel cycle (once through and
variations thereof).
Investigation of a fast reactor (FR) operating on a thorium-based fuel cycle, as opposed to the
traditional uranium-based is performed. Due to a combination between its neutronic properties
and its low position in the actinide chain, thorium not only burns the legacy TRU waste, but it
does so with a minimal production of “new” TRUs. The effectiveness of a thorium-based fast
reactor to burn legacy TRU and its flexibility to incorporate various fuels and recycle schemes
according to the evolving needs of the transmutation scenario have been investigated.
Specifically, the potential for a high TRU burning rate, high U-233 generation rate if so desired
and low concurrent production of TRU have been used as metrics for the examined cycles.
Core physics simulations of a fast reactor core running on thorium-based fuels and burning an
external TRU feed supply have been carried out over multiple cycles of irradiation, separation
and reprocessing. The TRU burning capability as well as the core isotopic content have been
characterized. Results will be presented showing the potential for thorium to reach a high TRU
transmutation rate over a wide variety of fuel types (oxide, metal, nitride and carbide) and
transmutation schemes (recycle or partition of in-bred U-233). In addition, a sustainable scheme
has been devised to burn the TRU accumulated in the core inventory once the legacy TRU
supply has been exhausted, thereby achieving long-term virtually TRU-free.
