NEW EXTRUDER-BASED DEUTERIUM FEED SYSTEM FOR CENTRIFUGE PELLET INJECTION

The pellet injection systems for the next-generation fusion devices (s uch as the International Thermonuclear Experimental Reactor) and futur e fusion reactors will have to provide deuterium-tritium fueling for m uch loner pulse lengths (up to approximate to 1000 s) than present app lications (typically limited to less than several seconds). Thus, a pr ototype pellet feed system for centrifuge pellet injection has been de veloped and used in long-pulse (> 100 s) tests at the Oak Ridge Nation al Laboratory (ORNL). The new apparatus has two key components: (1) a cryogenic deuterium extruder and (2) an electromagnetic pellet punch m echanism. For maximum testing flexibility, the prototype is equipped w ith several other active components that allow remote adjustments, inc luding precise positioning of the punch and the capability to index th rough eight different pellet lengths. The new feed system was designed to mate with an existing centrifuge accelerator facility at ORNL, and experiments in the facility were carried out to document the performa nce and reliability of the new feed system. With 2.3-mm-diam deuterium pellets and a catenary-shaped accelerator (approximate to 1.2 m diam) , the prototype feed system was found to be capable of placing up to a pproximate to 90% of the punched pellets in the proper time/space wind ow for pickup and acceleration by the high-speed rotating (approximate to 50 Hz) arbor. For these operating parameters, the pellet nominal s peed was approximate to 430 m/s, and maximum pellet feed rates of 10 p ellets/s and greater were tested. 18 this article the equipment is bri efly described, and the experimental test results are summarized. Also , issues affecting overall pellet delivery efficiency are discussed. ( C) 1997 American Institute of Physics.