Remote maintenance of a combined regeneration-isolation valve for the ITER torus vacuum pumping system

A large-diameter valve suitable for high vacuum operation is under study for ITER (International Thermonuclear Experimental Reactor) torus evacuation. The valves must comply with specifications for leak-tightness, radiation resistance, dust tolerance, overpressure, and thermal gradients. Remote maintenance of the seal and valve moving parts without disturbance to the rest of the valve system is a requirement. The authors describe two methods of seal exchange by remote means. In the first method, a flask is proposed for the valve moving parts exchange in inert gas, when the machine is shut down. In the second method a novel concept is described for seal exchange while under vacuum, without having to bring the machine up to atmosphere. The advantages of this method are that scheduled remote handling operations and outages for seal replacement are not required. Also, the need for a flask is avoided