b'Figure 3. Photograph (top) ofthe engraved channel box specimen; (left and middle, respectively)This is the first neutron irradiation of a SiC/SiC composite closer views of the engravedchannel box to evaluate the extent of lateral bowing under markers and (right) a processed image of a single marker a fast neutron flux gradient to ensure that bowing of a SiC/SiC BWR channel box would not interfere with control blade movements during commercial reactor operation.Accomplishments: core) of the 30 mm square channel Detailed three-dimensional Montebox specimen results in a calculated Carlo neutronic calculations weredifferential radiation-induced swelling performed to determine the spatialof 0.55 vol % after two irradiation variations in dose rate throughout thecycles. The resulting bowing is calcu-entire sample geometry. These doselated to be 1.02 mm (Figure 2) at rates were used as inputs to structuralthe end of the two-cycle irradiation. finite element simulations along withCalculated normal stresses are on the swelling correlations that were previ- order of megapascals and less than 13 ously established in the literature toMPa for all evaluated cases. In addi-predict the deformation of the speci- tion to typical dimensional inspec-mens due to spatial variations in dose.tions (length, width, depth, and wall The ~35% reduction in dose rate fromthickness), the channel box specimen the front face (facing toward the core)was engraved with fine markers for to the back face (facing away from themapping local strains (Figure 3) and 70 2021|AFC ACCOMPLISHMENTS'