An experimental evaluation of a small fusion fuel cleanup system

Small tritium-burning experimental tokamaks will require some means of handling the fuel after a burn. This paper presents an experimental evaluation of a scheme that would provide for the removal of the impurities produced in the fuel during the burn and delivery of the purified fuel for a subsequent burn in the machine. The fuel, simulated in this work by a hydrogen-impurity mixture, is taken from the machine, diluted to 25% with helium and passed through a uranium metal bed at 250C, where the hydrogen is trapped reversibly and several of the impurities are irreversibly absorbed. The results showed complete removal of O/sub 2/, CO, CO/sub 2/, H/sub 2/O and N/sub 2/O at room temperature. Removal of CH/sub 4/ and NH/sub 3/ required the uranium to be heated to approximately 4000C. At 4000C the hydrogen is released from the uranium metal, so the cleanup scheme requires circulation of the gas through two uranium beds, one at room temperature and one at near 4000C. When all the impurities are reacted the low temperature uranium bed is heated to 4000C to release the hydrogen back into the system in preparation for reinjection into the machine. An apparatus, simulating a small fusion fuel cleanup system, was built and demonstrated