Radiation Effects on High Thermal Conductivity Fuels (Final Scientific Report)
High thermal conductivity nuclear fuels offer important potential advantages over traditional oxide-based fuels such as higher burnup, reduction in fission gas release, and better overall safety of the reactor system. One interesting approach to high thermal conductivity fuels utilizes high thermal conductivity nonfissile additives to UO2 fuel to lower the fuel operating temperature and thereby take advantage of the highly favorable radiation resistance of UO2 at lower operating temperatures. However, differential swelling between the matrix and high conductivity additive phases during high dose irradiation could lead to internal cracking and poor performance. In the current study, ceria (CeO2) and zirconia (ZrO2) surrogate matrices were used to model UO2 behavior. Al2O3 or SiC in the form of nanoscale powder or platelets, respectively, were used for the high conductivity second phase. The nuclear fuel surrogates were sintered to achieve densities greater than 93% of the ideal values. Scanning electron microscopy (SEM) imaging and X-ray diffraction confirmed the uniform distribution of the second phase and that no intermetallic second phase was formed during sintering. The thermal conductivity of the sintered samples was measured from 50°C to 900°C and revealed an important increase compared to pure CeO2 and ZrO2 pellets. Samples were irradiated with 20 MeV Ni6+ ions at midrange doses ranging from 1 to 15 displacements per atom (dpa) and temperatures from 300°C to 700°C. Post irradiation characterization revealed a good stability of the samples at low to medium doses (1 to 5 dpa) but showed a significant microstructural deterioration and decrease of the mechanical properties at 15 dpa. Although microcracking is not observed at the interface between the matrix and high conductivity phase for any investigated irradiation condition, the strength degradation at 15 dpa suggests that these high thermal conductivity fuel forms may not be suitable for high burnup applications in current or proposed fission reactors.
- Research Organization:
- Univ. of Tennessee, Knoxville, TN (United States)
- Sponsoring Organization:
- USDOE Office of Nuclear Energy (NE)
- Contributing Organization:
- Oak Ridge National Laboratory (ORNL)
- DOE Contract Number:
- NE0008419
- OSTI ID:
- 1504155
- Report Number(s):
- 15-8752; 15-8752
- Country of Publication:
- United States
- Language:
- English
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