Features of Postfailure Fuel Behavior in Transient Overpower and Transient Undercooled/Overpower Tests in the Transient Reactor Test Facility

Prototypic oxide fuel was subjected to simulated, fast reactor severe accident conditions in a series of in-pile tests in the Transient Reactor Test Facility reactor. Seven experiments were performed on fresh and previously irradiated oxide fuel pins under transient overpower and transient undercooled/overpower accident conditions. For each of the tests, fuel motions were observed by the hodoscope. Hodoscope data are correlated with coolant flow, pressure, and temperature data recorded by the loop instrumentation. Data were analyzed from the onset of initial failure to a final mass distribution at the end of the test. Results of these analyses are compared to pre- and posttest accident calculations and to posttest metallographic examinations and computed tomographic reconstructions from neutron radiographs.