Hastelioy X wire wood has been has been considered by the Architect Engineer for exterior thermal insulation of some pipe sections of the ATR gas loop. Heat transfer studies were made simulating gas loop operating conditions. This report describes the apparatus used and the resultant data. The insulation (manufactured by a commercial supplier) is of interest because of its corrosion resistance, strength, and ability to withstand impact and abrasion. Also, it is not a source of chlorides. The insulation is produced in cylindrical sections and consists of Hastelloy X wire wool compressed and sintered to a given density and sinter bonded to a thin Inconel outer sheath.