2018 | AFC ACCOMPLISHMENTS 71 This project evaluates the performance of advanced fuel/ATF options for LWRs, and identifies whether the options have at least equivalent performance and safety characteristics relative to current uranium dioxide (UO2) fuel and zirconium alloy (Zr) cladding, as well as offering potential performance and/or safety benefits under nominal conditions and in accident scenarios. fuel phases, such as U3Si2, and UN have been proposed by Los Alamos National Laboratory (LANL). Initial modelling of these options with the TRITON neutronic lattice physics code to provide an initial estimate of the impacts on reactor performance and safety characteristics are underway. Figure 1 shows K-infinity vs. burnup for 20 µm coatings of Zr-metal, ZrB2, Y2SiO5, Cr-10Al, and AlN on UN. The analyses all assumed the standard Westinghouse 17x17 assembly geometry and fuel pellet OR and Zircaloy cladding IR/OR; therefore, the gap was reduced by the thickness of the coating.The nitrogen for all cases was “natural” as was the boron in the Zirc-diboride. The burnups for the different coatings are all essentially the same, and only slightly lower than for the “reference” UO2-Zr case. The reactivity and control coefficients (fuel and moderator temperature coefficients, and soluble boron and control rod worths) are effectively the same for all the coatings for the 20 µm thickness. Analyses for a 40 µm thickness coating and for U3Si2 fuel are underway. Transient analyses of ATF concepts with theTRACE systems analysis code continued. As a result of a benchmark effort theTRACE 3-loop PWR plant model was updated with emergency core cooling systems (ECCS) injection characteristics that are prototypic of 3-loop plants. Using this updated model a large-break loss-of-coolant accident (LB-LOCA) was analyzed. The analyses used a version ofTRACE version 5 Patch 5 modified by MIT to include FeCrAl and several other metals as build-in materials.The MIT modification includes metal/ water reaction models for these new build-in materials.Two cases were analyzed for a core consisted of UO2 fuel rods cladded in FeCrAl, a mitigated case and an unmitigated case.The mitigated case assumed availability of the full complement of ECCS while the unmitigated case assumed no ECCS activation. Results for the peak cladding temperature and the maximum equivalent clad reacted (ECR) are shown in Figures 2 and 3 for the peak cladding temperature (PCT), and ECR, respectively. For the hot rod in the unmitigated case the FeCrAl cladding reached the melting temperature of 1800 K at 286 second and the corresponding ECR at incipient melting was 8.6%.The mitigated case did not result in significant clad heatup and there was no clad reaction.