Fuel plates under development for high-performance U. S. reactors con­sist of a UMo alloy foil (“U-10Mo Foil” in Figure 2-1) surrounded by a zirconium fission recoil barrier (“2X Zirconium Interlayer” in Figure 2-1) in an aluminum cladding (“Al 6061 Cladding” in Figure 2-1). The barrier is intended to prevent interactions at the interface of the fuel meat and cladding. A key issue for this fuel is the stability of this interface. Although the interface is mechanically stable, swelling of the fuel meat during irradia­tion could lead to the development of porosity at the interface and eventual delamination of the foil from the cladding. Such swelling and delamination could prove to be a life-limiting factor for this fuel system.

Qualification testing of this fuel for three high-performance research reactors (MITR, MURR, and NBSR) is currently under way. A partial fuel assembly[32] is currently being irradiated in ATR at the Idaho National Laboratory (Figure 2-2), and irradiation of ATR fuel elements is planned

to begin in 2012. Lead test assembly irradiations are planned once these irradiations are completed.

Testing of this fuel system for use in the highest-performance U. S. reactors (i. e., ATR, HFIR) is planned to begin in late 2011. Bounding- condition irradiation tests (greater than 500 W/cm2 and greater than 60 percent burnup) on a full-size fuel plate will be carried out at the ATR in late 2011. Fuel qualification testing will be initiated after these irradiation tests are completed.