Destructive Examinations of a Regenerated Large Cold Trap

A large cold trap with sodium inventory of ∼1.0 m³, which had been regenerated at high temperatures (i.e., 450 to 600°C) 16 times during its 6-yr life, was subjected to destructive examinations. Emphasis was placed on determination of material damage to the mesh wires and the compositional material due to the multi-time high temperature regenerations. With regard to the mesh wires, the results of examinations revealed that mechanical strength was significantly reduced due to selective leaching of metal elements such as nickel and chromium. Before the examination, formation of a crack or defect that could have been caused by stress corrosion was suspected in the stainless steel structural material. But no such crack or defect was found.