Abstract
Mixed oxide (MOX) test capsules prepared with weapons-derived plutonium were irradiated to a burnup of 50 GWd/MT. The MOX fuel was fabricated at Los Alamos National Laboratory by a master-mix process and irradiated in the Advanced Test Reactor (ATR) at the Idaho National Laboratory (INL). Previous withdrawals of the same fuel have occurred at 9, 21, 30, and 40 GWd/MT. Oak Ridge National Laboratory managed this test series for the Department of Energy�s Fissile Materials Disposition Program (FMDP). This paper describes the
preparation of the MOX fuel, the equipment design, and the irradiation history of the test capsules and discussesthe significance of the more important observations of the post-irradiation examinations (PIEs). Fuel
performance has been excellent and consistent with code predictions and with existing U.S. and European experience.