2014 Workshop on SiC Modeling Techniques

Organized by the MIT Center for Advanced Nuclear Energy Systems (CANES), the 2014 Workshop on SiC Modeling Techniques brought together US industrial leaders in the development of Silicon Carbide (SiC) multilayer composite cladding, including Westinghouse, General Atomics and Ceramic Tubular Products, as well as the US national laboratory leaders: Oak Ridge National Laboratory and Idaho National Laboratory, to discuss the latest SiC modeling developments and challenges.

A 2D axi-symmetric diagram of two layer SiC cladding with an inner monolith and outer composite layer at PWR operating conditions.  A heat  flux is applied in the inner surface representing the heat generation from the fuel.  The thermal gradient across the radial thickness of the gap along with the pressure differential between the inner and outer surfaces result in both thermal and mechanical stresses.  The top and bottom of the cladding are subjected to coolant side pressure.

Replacing the Zircaloy cladding of currently operating reactors with SiC cladding is one of the options being investigated by Department of Energy as part of the Accident Tolerant Fuel (ATF) program. The goal of the ATF program is to design a new fuel that is more tolerant to severe accident conditions while still maintaining similar reliability and economic performance. Of all the options considered, SiC cladding is perhaps the option with the most potential to meet such goals. 

At the same time, due to completely different material performance under pro-typical reactor conditions compared to Zircaloy, high degree of uncertainty is associated with SiC cladding performance.  The first day of the workshop consisted of sharing the latest models, methods and material properties used by each entity. Specifically, the workshop started by discussing the result of a benchmark study comparing a two-layer SiC cladding mechanical performance with assumed properties and boundary conditions as inputs.  All entities calculated similar results, implying that the large discrepancies in the reported performance of SiC cladding among the different entity is due to differences in the inputs.  Other notable discussions, included treatment of fiber-to-matrix and matrix-to-monolithic SiC bond strength, as all current analysis assumes perfect bonding between the SIC layers.

In the workshop, MIT showed its modeling capability to both extend to high fidelity 3D fuel performance simulations of MOOSE-BISON as well as extension to fuel analysis of every pin in the core via in-house code Redtail, to better quantify SiC cladding performance under LWR operating and transient conditions.

Finally, the meeting highlighted the need for more experimental data involving the multilayer cladding samples as well as the discussion on the design of such experiment by ORNL, which dominated the second day talks.  

See all CANES SiC reports: https://canes.mit.edu/publications?f[keyword]=10