2018 | ANNUAL REPORT 113 Figure 1. Schematic diagram of the U9807 assembly and its relationship to the EBR-II fueled core. The core is 30 cm tall so Block 3 is the only one fully within the elevation range of the core. Also shown are the two blocks chosen for extensive evaluation at Westinghouse—Block 3 below and above—with the first stage of destructive examination being the production of hex-coins with thicknesses of either 1.2 or 2.5 cm. The mid-block exposures of 3 and 5 were ~30 dpa and ~2.5 dpa, respectively. These AISI 304 materials were retrieved from the Idaho National Laboratory (INL) Experimental Breeder Reactor II (EBR-II) near Idaho Falls.As shown in Figure 1, the EBR-II fast reactor Row 8 reflector assembly designated U9807 comprised a stack of six hexagonal cross-section blocks (hex-blocks), with sodium flowing outside the wrapper duct (hex-can) and also flowing in the gaps between the outer surface of the hex-blocks and the inner surfaces of the hex-can. There are both radial and axial variations in temperature and neutron exposure in these blocks, determined by ambient coolant temperature and gradients in gamma heating within the block.