Postirradiation examination on metallic fuel in the AFC-2 irradiation test series

Abstract Irradiation experiments on metallic fuel alloys containing rare earth additions to simulate potential carry-over from pyro-metallurgical reprocessing and minor actinide additions were performed in the Idaho National Laboratory Advanced Test Reactor. These tests were designated AFC-2A and AFC-2B. Additionally irradiation experiments were also performed on metallic fuel alloys containing minor actinide additions that were fabricated by different techniques. These tests were designated AFC-2E. These pins were removed from the reactor after achieving burnups between 6 and 11% fission per initial heave metal atom. Examination of these pins revealed that they were unintentionally operated beyond their desired power and temperature conditions. Highlights from the postirradiation examination of these experiments is discussed. A variety of issue contributed to the poor performance of these irradiation tests including capsule design, reactor power variations and fabrication issues. While all the issues contributed, the major issue was determined to be unanticipated variations in reactor power. Through comparisons between these experiments and historical off-normal experiments, it was possible to conclude bound the operating temperatures of these experiments. There likely was some in-pile melting in the rare earth addition experiments (AFC-2A, AFC-2B), but it is not likely that there was in-pile melting in the fabrication technique experiments (AFC-2E).