Analysis and examination of MOX fuel from nonproliferation programs

The U.S. Department of Energy has decided to dispose of a portion of the nation's surplus plutonium by reconstituting it into mixed oxide (MOX) fuel and irradiating it in commercial power reactors. Four lead assemblies were manufactured and irradiated to a maximum fuel rod average burnup of 47.3 MWd/kg heavy metal. This was the worlds first commercial irradiation of MOX fuel with a ²⁴⁰Pu/²³⁹Pu ratio of less than 0.10. Five fuel rods with varying burnups and plutonium contents were selected from one of the assemblies and shipped to Oak Ridge National Laboratory for hot cell examination. The performance of the rods was analyzed with AREVA's next-generation fuel performance code, GALILEO. The results of the analysis confirmed that the fuel rods had performed safely and predictably, and that GALILEO is applicable to MOX fuel with a low ²⁴⁰Pu/²³⁹Pu ratio. The results are presented and compared to the global GALILEO validation and verification (V&V) database. In addition, the fuel cladding was tested to confirm that traces of gallium in the fuel pellets had not affected the mechanical properties of the cladding. The irradiated cladding was found to remain ductile at both room temperature and 350°C for both the axial and circumferential directions.