The program proposed would expose candidate advanced ceramic PWR fuel clad materials in a PWR loop at the MITR to levels of exposure expected in service. These materials are in the form of “triplex” SiC/SiC composites consisting of an inner SiC monolith acting as a gas barrier layer, a SiC fiber/SiC matrix composite layer for desirable mechanical properties and a SiC environmental barrier layer for enhanced corrosion resistance. Some tube samples have exhibited satisfactory behavior for up to 12months of exposure at PWR conditions in the MITR loop. Several of these samples would continue to be irradiated together with newly manufactured samples that are expected to have improved characteristics. The exposure conditions are very close to those in a commercial PWR and several years of exposure will be accumulated for some samples. Post irradiation examination will consist of weight loss measurements, visual inspection, mechanical property testing (tube burst tests), SEM examination of surfaces and crosssections and possible thermal conductivity measurements. The data generated will fill a gap in data that is necessary to ascertain and understand the behavior of advanced ceramic fuel cladding. Information will be used to determine characteristics of the triplex material under irradiation and to benchmark modeling efforts for SiC/SiC composite in preparation for integrated testing of fuel segments in a test reactor. Thehigh temperature strength and chemical stability of ceramic clads give them the potential for improving response under accident conditions compared to Zircaloy fuel cladding. Ceramic clad fuel may also offer higher burnup capability than is possible with current materials. Very little irradiation data on ceramic composites of this nature is currently available and this program would results in a significant addition to the database.