Tritium removal by isotopic exchange

This paper discusses how isotopic replacement is effective to remove tritium retained in the plasma facing surface in a DT reactor based on our recent studies on retention of hydrogen isotopes (H, D, and T) in plasma facing carbon tiles used in JT-60U. The isotope ratio of D and H in hydrogen retained near surface layers of the plasma facing wall is easily equilibrated with the flux ratio of hydrogen isotopes impinging the surface. Therefore DD discharges after DT discharges would effectively remove T retained in the surface layers during DT discharges. The efficiency of the replacement is higher and deeper for higher temperatures.