CANNING GRAPHITE FOR GAS-COOLED REACTORS

A preliminary investigation was made of techniques and materials for canning graphite to protect it for use at high temperatures in a nitrogen--oxygen atmosphere. Fabrication techniques for cladding bare and copper--plated graphite cores either in Type 316 stainless steel or Inconel X were developed. Specimens of the various combinations of core and cladding materials were subjected to simulatedservice conditions and evaluated. In all cases the Type 316 stainless steel-clad specimens failed by carburization and subsequent oxidation in relatively short periods of time. Although considerable trouble was experienced with rupture in the vicinity of the cladding welds during thermal cycling of the Inconel X-clad specimens, this material appeared to be satisfactory in other respects and is considered promising. A specimen of silicon-coated graphite eiad with Type 316 stainless steel was tested by heat treating for 624 hr at 1800 deg F. The silicon coating alloyed with the cladding material, formed a high-silicon diifusion zone, but prevented carburization of the stainless steel. (auth