Development of Super 100-MGy Radiation-Durable Motor and Study of Radiation Resistance Mechanism

A super radiation-resistant motor was developed for ITER, consisting of high radiation-durable organic insulation materials, such as poly(benzimidazole), poly-liquid-crystal (VECRUS¯, VECTRA¯), and poly(phenyl ether)/urea grease. The motor was subjected to irradiation tests carried out by -ray at room temperature, and its radiation resistance was confirmed to be more than 100 MGy, which is 50 times of that of an ordinary radiation durable motor. The key factor for attaining high radiation resistance was the application of aluminum (Al) thin leaves (thickness: 0.2 m) mainly having ≪100≫ faces. In a -rays irradiation test conducted on VECRUS¯ paper containing Al leaves and overcoated by a silicon layer, an average absorption cross section for the Compton effect was found to decrease by 20% from the theoretical value calculated by the formula of Klein and Nishina. These results show that a secondary electron beam generated from a -ray can easily pass through VECRUS¯ paper coated by a silicon layer including the dispersing Al leaf, by means of the channeling effect through the crystal lattice, thereby avoiding a close single collision and reducing serious damage.