Behavior of metallic fast-reactor fuels during extended transients

The integral fast reactor (IFR) concept being developed by Argonne National Laboratory uses a metallic driver fuel. One of the key features of metallic fuel is improved safety through lower stored energy and enhanced passive negative reactivity feedbacks during off-normal events. As a consequence of these features it is possible to avoid core damage even for circumstances where the automatic scram system fails to operate or where decay heat removal systems are severely degraded. During these extended transients, the reactor slowly heats up over tens of minutes to hours before the transient is terminated. The time scales for these events are intermediate between those of the accident transients that have been analyzed in previous saety assessments and those of the steady-state operation. Consequently, it has been necessary to validate models and computer codes (FPIN2 and LIFE-METAL) for application to analyses of metallic fuel behavior in this intermediate time regime. It is the modeling of metallic fuel behavior during long-term transients and the validation of the models using results from whole-pin furnace tests on irradiated fuel pins that is the subject of this paper