PRELIMINARY STUDIES ON LARGE METAL-SEALED GATE VALVES FOR THE INTERNATIONAL THERMONUCLEAR EXPERIMENTAL REACTOR (ITER)

摘要

D-T burning will stimulate plasma chemical/physical reactions, radiation damage by fast neutrons and high energy gamma rays, tritium inventory, and ingress of carbon dust. Under such harsh conditions valves are required with metal seals of large aperture (a rectangular opening of 3m in height and 1.2m in width and a circular one of diameter 2m), which have never been constructed before, and must operate robustly for more than 10(4) open/close cycles. Preliminary studies on the valve covered: (1) conceptual design studies on the basis of ''soft on hard'' type of seal structure and major features are proposed to clarify geometries in design bf the valves; (2) development of two key components, seat surface coated with plasma-sprayed WC-Co and Helicoflex-type gasket with double liners; and (3) sealing performance. A 176mm diameter gasket successfully achieved a seal force lower than 200 kgf/cm, repeated over more than 10(4) closures, lower than 1 x 10(-9) Pa m(3)/s. The sealing mechanism with succesive tightenings and the feasibility for scaling up to a full size model are discussed. Copyright (C) 1996 Elsevier Science Ltd. [References: 11]