NuFuel & MMSNF 2015

First Workshop on Research into Nuclear Fuel in Europe
and Materials Modeling and Simulation for Nuclear Fuels Workshop
Karlsruhe, Germany, November 16th to 18th, 2015

Updated: Tue 08 Dec 2015, 14:27

Talk 4.1: Thermodynamic Evaluation of a Matrix of High Density, Composite, and Accident Tolerant Fuels

Theodore M. Besmann and Mark J. Noordhoek
  • University of South Carolina


Alternative compositions of light water reactor (LWR) fuels are being considered to replace solely UO2 pellet fuel to either improve performance or to be more accident tolerant. Any alteration in fuel behavior will have a cascade effect on reactor operation such as expected thermal performance, choice of cladding, and fission product behavior. An important consideration is the thermodynamic stability of these fuel forms, whether inter-compatibility of composite fuel components, potential interactions with cladding, and behavior during generation of fission products. The addition of secondary phases to either UO2 or high density fuel forms may result in potentially problematic property changes such as lower melting temperatures than the primary phase, which can result in reactor safety concerns, as well as lead to enhanced diffusion of fission products. Thus, an understanding of the phase stability as a function of both fuel phases and their relative ratios is important.

The fuel phases of current interest are urania, uranium borides, uranium mononitride, and uranium silicides. The phase equilibria of various combinations of these phases are expected to be designed to meet improved fuel performance and safety, and these systems have been preliminarily evaluated. As a result, phase regions of concern have been identified, and areas of insufficient knowledge and understanding delineated. This report reviews the matrix of high density and composite fuel options under consideration and provides a thermochemical understanding based on newly developed as well as available fundamental information.

This research was sponsored by the U.S. Department of Energy through the Office of Nuclear Energy–Fuel Cycle R&D.