Abstract

Accident Tolerant Fuel, ATF , is defined as fuel that can tolerate loss of active cooling, in a severe accident scenario, for a longer time than current standard products. This gives operators more time to react and mitigate the accident before core meltdown. The extra time is often called the “Grace Time”, and should be at least hours, preferably days, to be meaningful. The new fuel will be backfitted into existing light water reactors. Therefore, in addition to providing an enhanced accident tolerance, it must be compatible with current products with respect to, e.g., geometry, and perform at least as good under normal operation and anticipated transients. Key ingredients are fuel cladding tubes with high corrosion resistance in steam at elevated temperatures, up to 1700° C, and fuel pellets with enhanced metal density compared to ordinary UO2 . There is a major, global effort to develop ATF , in collaboration between industry, universities and laboratories.