ACTIVE CONTROL OF HYDROGEN RECYCLING BY THE PERMEATION AND ABSORPTION TECHNIQUES

摘要

Thy potential barrier of hydrogen dissociative absorption plays an outstanding role in the interaction of energetic hydrogen with solid. The surface barrier does not impede the implantation of suprathermal hydrogen particles of an energy higher than ～1 eV, but it drastically impedes the thermal reemission of absorbed atoms. As a result, the presence of a surface barrier results in a dramatic increase of the absorption and permeation of supralhermal hydrogen. At definite conditions, the permeation reaches its conceivable limit when virtually the whole incident flux passes through the solid membrane irrespective of its temperature and thickness (the superpermeation). Thin (monolayer and even submonolayer) films of nonmetallic impurities are responsible for the barrier on the surface of transient metals, and the surface covered by a monolayer nonmetallic film is the usual state of a metal surface in vacuum (the "real" surface). Two implications important for fusion follow from that. First, the properties of PFM that govern reemission, absorption and permeation depend on physico-chemical environment. Thus the PFM behavior in fuel recycling and tritium inventory/permeation may he dramatically changed during the operation, and such an evolution is not easily predictable. Second, the superpermeation and enhanced absorption can be specially employed for a short-way separation of D/T from He [4] and for an active particle control in fusion devices.