PERFLUORINATED MATERIALS IN TRITIUM SERVICE

Various perfluorinated materials are used at the Princeton Plasma Phys ics Laboratory in support of the Deuterium-Tritium experimental progra m on the Tokamak Fusion Test Reactor (TFTR). For example, SF6 is used as a high dielectric gaseous insulator in the Neutral Beam sources, an d Krytox(R), a perfluorinated polyether, is used as a lubricant in vac uum pumping systems. Each of these materials is robust and stable in t he applications for which they are designed but may be a source of tro uble when used in tritium systems. This paper reports on the observati ons made and experience gained operating tritium systems under conditi ons which degrade these perfluorinated materials. The possible degrada tion mechanisms and products are described, and the effect on the equi pment and instrumentation is described, These observations have led to the conclusion that under certain circumstances perfluorinated materi als are not suited for tritium service because of the degradation prod ucts from tritium decay and/or process conditions.