Superpermeability: Critical points for applications in fusion

One of key points for the applications of superpermeable membranes in fusion is the question of the upper limit of the permeation flux density. Theoretical estimates give the maximum fluxes of ∼ 10 19 cm −2 s −1 for the V group metal membranes. The permeation fluxes of up to 3 × 10 16 and 4 × 10 17 cm −2 s −1 were achieved using Nb and thermal atomic hydrogen in the direct membrane experiments and in simulation absorption experiments respectively. Achievement of higher fluxes has been limited by the experimental equipment opportunities. Another important point is the reliability of membrane operation in the presence of chemically active gases. No negative effects of CH 4, CO and O 2 specially introduced on a superpermeable Nb membrane were detected during 3000 h of operation. Such membranes coupled with special hydrogen atomizers can be easily incorporated into the up-to-date ITER design concept. The membranes installed in every of the 24 ducts might isolate > 90% of D/T with the flux densities already reached.