Final examination and testing of the TFTR TF-coils

Abstract

In operation for nearly 15 years, the Tokamak Fusion Test Reactor (TFTR) was not only a fusion science milestone, but a milestone of achievement in engineering as well. The TFTR Decontamination and Decommissioning (D&D) program provided a rare opportunity to examine machine components that had been exposed to a unique performance environment of greater than 100,000 mechanical and thermal load cycles. In particular, the examination of the TFTR toroidal field (TF) coils, which met then exceeded the 5.2 tesla magnetic field machine specification, could supply the answers to many questions that have been asked and debated since the coils were originally designed and built. A test program conducted in parallel with the D&D effort was the chance to look inside and examine, in detail, the TFTR TF coils for the first time since they were delivered encased to PPPL. This program set aside a number of selected sections from the twenty TFTR TF coils as they were removed during D&D. These sections were cut from the coils in several different areas including the nose, back leg, water fitting and lead block regions, concentrating on those known areas whose performance was questioned during TFTR operations. The test program included documented visual inspections and photography during all phases of disassembly and testing. Physical examinations of the coils were performed to determine consistency of coil manufacturing techniques, including status of the potting compound, quality of turn-to-turn epoxy impregnation and bonding, and determination of the cause of coolant leaks during operation. Selected chemical and metallurgical analyses were conducted to determine if the composition of the materials have altered and to identify unknown materials. Multiple mechanical test samples in various orientations were cut from several magnet and case locations to check for consistency and range of material properties. This paper discusses the findings of the test program.