TRITIUM PROOF-OF-PRINCIPLE PELLET INJECTOR - PHASE-II

As part of the International Thermonuclear Engineering Reactor (ITER) plasma fueling development program, Oak Ridge National Laboratory (ORN L) has fabricated a pellet injection system to test the mechanical and thermal properties of extruded tritium. This repeating, single-stage, pneumatic injector, called the Tritium-Proof-of-Principle Phase II (T POP-II) Pellet Injector, has a piston-driven mechanical extruder and i s designed to extrude hydrogenic pellets sized for the ITER device. Th e TPOP-II program has the following development goals: evaluate the fe asibility of extruding tritium and deuterium-tritium (D-T) mixtures fo r use in future pellet injection systems; determine the mechanical and thermal properties of tritium and D-T extrusions; integrate, test, an d evaluate the extruder in a repeating, single-stage light gas Sun tha t is sized for the ITER application (pellet diameter similar to 7 to 8 mm); evaluate options for recycling propellant and extruder exhaust g as; evaluate operability and reliability of ITER prototypical fueling systems in an environment of significant tritium inventory that requir es secondary and room containment systems. In initial tests with deute rium feed at ORNL, up to 13 pellets have been extruded at rates up to 1 Hz and accelerated to speeds of 1.0 to 1.1 km/s, using hydrogen prop ellant gas at a supply pressure of 65 bar. The pellets, typically 7.4 mm in diameter and up to 11 mm in length, are the largest cryogenic pe llets produced by the fusion program to date. These pellets: represent about a 11% density perturbation to ITER. Hydrogenic pellets will be used in ITER to sustain the fusion power in the plasma core and may be crucial in reducing first-wall tritium inventories by a process calle d isotopic fueling in which tritium-rich pellets fuel the burning plas ma core and deuterium gas fuels the edge.