Development of a plasma driven permeation experiment for TPE

Abstract

Experiments on retention of hydrogen isotopes (including tritium) at temperatures less than 800°C have been carried out in the Tritium Plasma Experiment (TPE) at Idaho National Laboratory [1,2]. To provide a direct measurement of plasma driven permeation in plasma facing materials at temperatures reaching 1000°C, a new TPE membrane holder has been built to hold test specimens (≤1mm in thickness) at high temperature while measuring tritium permeating through the membrane from the plasma facing side. This measurement is accomplished by employing a carrier gas that transports the permeating tritium from the backside of the membrane to ion chambers giving a direct measurement of the plasma driven tritium permeation rate. Isolation of the membrane cooling and sweep gases from TPE's vacuum chamber has been demonstrated by sealing tests performed up to 1000°C of a membrane holder design that provides easy change out of membrane specimens between tests. Simulations of the helium carrier gas which transports tritium to the ion chamber indicate a very small pressure drop (∼700Pa) with good flow uniformity (at 1000sccm). Thermal transport simulations indicate that temperatures up to 1000°C are expected at the highest TPE fluxes.