Initial irradiations of fuel elements containing UMo dispersions re­sulted in the formation of interaction layers between the UMo and Al particles and the development of porosity and distortion (pillowing). The addition of small amounts (~2 percent) silicon to the aluminum phase was

found to suppress the development of this interaction layer at burnups of up to 70 percent. However, test irradiations of this fuel material at high power (~ 500 watts per square centimeter [W/cm2]), high uranium loadings (> 8 gU/cm3), and high burnup (> 70 percent) resulted in the formation of small blisters on the fuel plates. Follow-up experiments are planned for the fall of 2011 to determine why such blistering occurs and how the fuel ele­ment can be modified to eliminate it. A bounding-case irradiation of this fuel material in BR2 is planned for 2011-2012.