Microstructure of the irradiated U3Si2/Al silicide dispersion fuel

The silicide dispersion fuel of U3Si2/Al is recognized as the best performance fuel for many nuclear research and test reactors with up to 4.8 gU/cm3 fuel loading. An irradiated U3Si2/Al dispersion fuel (235U ∼ 75%) from the high-flux side of a fuel plate (U0R040) from the Reduced Enrichment for Research and Test Reactors (RERTR)-8 test was characterized using transmission electron microscopy (TEM). The fuel was irradiated in the Advanced Test Reactor (ATR) for 105 days. The average irradiation temperature and fission density of the U3Si2 fuel particles for the TEM sample are estimated to be approximately 110 °C and 5.4 × 1027 f/m3. The characterization was performed using a 200-kV TEM. The U/Si ratio for the fuel particle and (Si + Al)/U for the fuel–matrix-interaction layer are approximately 1.1 and 4–10, respectively. The estimated average diameter, number density and volume fraction for small bubbles (<1 μm) in the fuel particle are ∼94 nm, 1.05 × 1020 m−3 and ∼11%, respectively. The results and their implication on the performance of the U3Si2/Al silicide dispersion fuel are discussed.

► We performed TEM characterization of an irradiated U3Si2/Al dispersion fuel plate.
► The U3Si2 fuel particles become amorphous as a result of irradiation at 110 °C.
► For bubbles less than 1 μm, the estimated volume fraction in the fuel is ∼11%.
► Bubble interlinkage was not identified at the fission density of 5.4 × 1027 f/m3.