Thermal properties evaluation of UF6 cylinder overpack insulation

A phenolic foam is incorporated into the design and construction of UF6 cylinder shipping containers known as overpacks. The overpack provides mechanical and thermal protection to UF6 product cylinders during transport. The phenolic foam is utilized for thermal insulation. An important criterion in overpack design is to limit temperature excursions of the product cylinder below the triple point of UF6, preventing possible overpressurization of the cylinder. A current requirement is that the product cylinder wall temperature be maintained below the UF6 triple point with the outer surfaces of the overpack exposed to 14750F for thirty minutes. A possible heat source is the close proximity of a fire. Overpack thermal protection design requires thermal properties data for the materials of construction, particularly for the phenolic foam insulation which provides the primary thermal resistance. Thermal conductivity and heat capacity data for the phenolic foam are limited in the literature. Accurate heat transfer models of the overpack require thermal properties spanning the range from room temperature to 14750F. An experimental program was devised to measure the thermal conductivity and heat capacity of the insulating foam over the temperature span of interest