Properties of Candidate ITER Vacuum Impregnation Insulation Systems
Composite insulation systems to be used in the International Thermonuclear Experimental Reactor (ITER) must meet demanding design requirements, including combined shear and compressive stresses, performance at cryogenic temperatures, and continued mechanical and electrical performance after exposure to high levels of neutron and gamma radiation. Several polymeric insulation systems that are reinforced with boron-free glass fabric and are suitable for the vacuum-pressure impregnation (VPI) method of fabrication were screened at 76 K using the short-beam-shear (SBS) test, with the leading candidates then tested in combined shear/compression at cryogenic temperatures. The shear/compression specimens were comprised of two, 12.7.mm diameter, stainless steel chips bonded together by the composite insulation, allowing characterization of its adhesive and cohesive properties. Using the shear/compression test at different ratios of shear to compression, a shear/compression failure envelope for each insulation system can be determined. Production variables of the shear/compression specimens, including molding techniques, were also investigated. The effects of desizing (4 h at 400°C) and heat treating (50 h at 700°C) the glass fabric to simulate the heat treatment of Nb3Sn superconductor, prior to vacuum impregnation, were also examined.
KeywordsCryogenic Temperature Glass Fabric Resin System Failure Envelope International Thermonuclear Experimental Reactor
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