“…The interdiffusion that may occur between the two materials at reactor operating temperatures has been discussed previously, in connection with the Core I development, by Walter and Kelman.1,2 The present investigation directed attention to the determination of certain aspects of the out-of-reactor compatibility of the two materials that are of interest in the development of the Mark-II fuel element. These include: (1) the compatibility of the fuel-cladding combination during annealing for times up to 104 hr at temperatures to 650°C, (2) the temperature, T at rn, which the materials interact to form a liquid phase, (3) the influence of silicon and aluminum additions to the fuel alloy on the compatibility of the fuel and cladding materials, and (4) the comparative compatibility of Types 304L and 316 stainless steel with the uranium-fissium alloy.…”