Large, all‐metal‐sealed, vacuum gate valve for fusion application

Abstract

Two large (30 cm and 1 m in diameter), innovative, fusion‐reactor‐compatible, vacuum gate valves have been developed which should contribute significantly to the vacuum hardware needs of the next‐generation, tritium‐burning fusion devices. Because no organic materials are used, the valves are tritium‐compatible and radiation‐hardened as well as compatible with toxic gases. These valves should also find applications in semiconductor manufacturing and in similar industries that have requirements for large, all‐metal vacuum valves. We have designed, built, and successfully tested a 30‐cm‐diam valve, and we have designed and are fabricating a 1‐m‐diam valve that we plan to assemble and test in 1992. This work makes use of the all‐metal‐sealed, radially directed, fluid‐pressure‐loaded seal design that was developed under a Department of Energy contract at the Lawrence Livermore National Laboratory. This seal, due to its radially directed loading, is easily scaled to larger diameters, and scales with the atmospheric loading of the gates, rather than with the seal loading. The valves are designed for high reliability: the 30‐cm‐diam valve utilizes double gates to provide two seals, and differential pumping; the 1‐m‐diam valve has a single gate with a double metal seal, and differential pumping. These valves are relatively light weight due to the unique radial seal. Typically, leak‐tight closures are obtained on every operation without differential pumping at pressures of 500–1000 psi applied to the radially sealing diaphragm. The seal components are fabricated from 304 stainless steel, but can also be made from aluminum.