Development of a filled resin system for the TF coils of ITER

The final step in assembly of the ITER TF coils will be the insertion of the Winding Pack (WP) into the TF Coil Casing (TFCC). In order to facilitate mounting of the WP within the TFCC the design is made with clearance gaps of 7–10 mm to allow for manufacturing tolerances and WP adjustment during mounting. It will be essential to fill these gaps as the last step of the insertion operation. The fill process is a critical part of the operation; it completes the geometric location of the WP with respect to the casing and must provide for a uniform force transfer between the WP and casing. The properties and specification of the filler material are therefore driven by these two requirements. Two process options may be considered; direct fill by vacuum impregnation using a filled epoxy; or, pre-fill of the inter-space with dry particles (fibres or beads or powder) followed by vacuum impregnation with a low viscosity (unfilled) epoxy. aper reports on experimental studies of both process options. The properties of a trifunctional epoxy resin system (TGPAP) filled with wollastonite, dolomite and milled glass fibres have been studied. Studies of flow and particle settling are reported. The same epoxy system has been used to impregnate samples pre-filled with dry particles, soda glass and alumina. Thermal contraction and mechanical strength measurements at 77 K are reported for both systems.