Deuterium to protium isotope exchange in W-D co-deposited films below 200°C

Abstract

Hydrogen isotope exchange as a method for removal of heavy hydrogen isotopes from tungsten co-deposits in fusion devices was investigated by exposing fresh W-D co-deposited films in protium atmosphere. The temperature was in the range from room temperature to 473 K (200°C), the protium pressure was 1 atm, the time of exposure was 18 hours. It was shown that the efficiency of exchange increases with temperature, and at least 99% of deuterium was removed at 473 K from 250 nm thick films. Vacuum annealing was much less efficient at all experimental conditions. Similar to polycrystalline materials, multiple occupation of traps by hydrogen isotopes is suggested to be a key mechanism of D to H exchange in the co-deposits.