Postirradiation Ductility Demonstration Tests of Weapons-Derived MOX Fuel Cladding

Abstract

The U.S. Department of Energy (DOE) Fissile Materials Disposition Program (FMDP) is pursuing reactor irradiation of mixed uranium-plutonium oxide (MOX) fuel for disposal of surplus weapons-usable plutonium. Since most of the MOX fuel utilization experience has been with reactor-grade plutonium, it is desired to demonstrate that the unique properties of the surplus weapons-derived or weapons-grade (WG) plutonium do not compromise the applicability of this MOX experience base. A related question to be addressed for weapons-derived MOX fuel is that of ductility loss of the cladding. While irradiation induced loss of ductility has long been known and quantified for many cladding materials, the potential synergistic effects of irradiation and the unique constituents (i.e., gallium) of weapons-derived MOX fuel are not known. As part of an extensive fuel qualification research program conducted by Oak Ridge National Laboratory (ORNL), a new test method was developed and validated to measure the room temperature ductility and hoop tensile properties of MOX fuel cladding. The cladding material is a zirconium alloy designated as Zr-4 manufactured by Sandvick Corporation. This paper is a summary of the test method developed and of demonstration test results obtained for MOX cladding irradiated to 21 GWd/MT [7 × 1020 n/cm2 (E > 1 MeV)].