2018 | AFC ACCOMPLISHMENTS 166 Figure 2. 2D calculation showing temperature and porosity contours in a restructured fuel pellet in an offset (a, b) and position relative to the cladding. The as-fabricated porosity was 15%. Power was ramped from 0 to 37 kW/m in 104 seconds. Cladding exterior was held at 600 K. The pellet and cladding were thermally coupled using a meshless contact approach. For the offset case, the contour plot shows the peak temperature and porosity is offset from the geometric center, which is expected due to the offset fuel pellet within in the cladding. The offset position of the fuel pellet creates a gap that is larger on one side, resulting in correspondingly higher temperatures in the direction of the larger gap. Also note the elliptic shape of the central void with the major axis orthogonal to the thermal gradient. The offset and shape of this void is qualitatively similar to the micrograph shown in Figure 3. for LHGR of 20 to 50 kW/m in 5 kW/m increments. Results of these calculations are shown in Figure 2b. It was found that BISON has reproduced the trend of increasing central void with an increase of LHGR. Future work will be focused on extensive modeling of fast reactor oxide fuel irradiation experiments and comparing measured central void diameter with that calculated using BISON. Results for the offset case are shown in Figure 2.The contour plot shows the peak temperature and porosity is offset from the geometric center, which is expected due to the offset fuel pellet within in the cladding. The offset position of the fuel pellet creates a gap that is larger on one side, resulting in correspondingly higher temperatures in the direction of the larger gap.Also note the elliptic shape of the central void with the major axis orthogonal to the thermal gradient. The offset and shape of this void is qualitatively similar to the micrograph shown in Figure 3.