2018 | AFC ACCOMPLISHMENTS 46 Thermal conductivity of candidate ATF, burnable absorber phases: UB2 and UB4 Principal Investigator: Erofili Kardoulaki Collaborators: Darrin Byler, Ursula Carvajal Nunez, Ken McClellan – Los Alamos National Laboratory, Andy Nelson – Oak Ridge National Laboratory, TiankaiYao, Bowen Gong, Jie Lian - Rensselaer Polytechnic Institute Figure 1: Achieved densities for all UB2 and UB4 samples SPS sintered under a 5 minute hold, compared to conventionally sintered UB2 samples under a 4 hour hold. Uranium borides such as UB2 and UB4 have been shown to have high theoretical thermal conductivity (Joussou et al., 2017) and can provide the additional advantage of acting as an efficient burnable absorber when tailoring the enrich- ment ratio of 10B/11B, due to the large neutron cross-section of 10B. Despite the interesting properties of uranium borides, these materials have not been extensively studied in the literature, partly due to the difficulties associated with their fabrication using conventional techniques. Field assisted sintering (FAS) techniques describe a group of novel sintering methods that use electric field and current to provide powder densification in very short time periods (minutes compared to hours) and at low temperatures compared to conven- tional sintering. One such technique is Spark Plasma Sintering (SPS) which uses field, pulsed direct current, and uniaxial