SBIR-STTR Award

Fusion reactors based on the magnetic confinement of plasmas will require high speed pumping of helium, deuterium, tritium at high throughput while limiting the inventory of tritium in the pumps to a low level. Minimizing the tritium inventory of a fusion reactor is very desirable because it improves the passive safety of the reactor. A compound cryopump was selected by the Internal Thermonuclear Experimental Reactor (ITER) design team for the conceptual design of the ITER vacuum pumping system. Unfortunately, in existing designs, the cryopump must be regenerated frequently to limit the inventory of tritium in the pump. This frequent regeneration requires rapid cycling of many large vacuum and cryogenic valves and other components, compromising the reliability of the system and possibly leading to a higher tritium inventory than desirable. A continuous compound cryopump is being developed that meets the ITER performance requirements without cycling the pump, while reducing the tritium inventory in the pumping system from 400 grams to less than 100 grams. This compound cryopump requires an extension of the cryopump technology being developed for various applications; the novel untested feature is a continuous argon-frost cryosorption pump. The Phase I effort should demonstrate the feasibility of this feature and produce a conceptual design for a prototype pump for the ITER. The Phase II effort will undertake to design and construct a prototype ITER pump suitable for testing at a DOE tritium facility.Anticipated Results/Potential Commercial Applications as described by the awardee:This project should lead to a practical continuous cryosorption cryopump. This pump could be used on contemporary and future fusion reactors. The new cryopump technology may have commercial uses in pumping of sputtering chambers used in thin-film metallization, a process used in microelectronics fabrication.

Fusion reactors require highspeed pumping of helium, deuterium, and tritium while maintaining the inventory of tritium in the pumps at a low level. Cryopumping is potentially the most attractive method for this task, but existing cryopump designs require that the pump be removed from service frequently and regenerated to prevent an excessive accumulation of tritium in the pump. For example, the International Thermonuclear Experimental Reactor (ITER) conceptual design calls for a twohour operating cycle: 80 minutes for pumping and 40 minutes for regeneration. This frequent regeneration requires cycling of large vacuum valves and cryogenic components that introduces inefficiencies and places a burden on the reliability of the system. The objective of this project is to develop a continuous compound cryopump that can meet ITER performance requirements without frequent cycling for regeneration and that will greatly reduce the tritium inventory in the pumping system. In Phase I, the feasibility of such a pumpwas shown by tests with an experimental cryosorption pump that demonstrated continuous pumping of argon, copumping of argon/hydrogen mixtures, and continuous pumping and regeneration of pure hydrogen on a CO2 frost. A conceptual design was made of a continuous pumping system for ITER. In Phase II a prototype of an ITER pump will be constructed and tested that will continuously pump and regenerate a deuterium/helium/impurity mixture and produce a separate, purifiedliquid stream suitable for the production of solid pellets to be reinjected into the plasma. The prototype pump will be suitable for testing at a DOE tritium facility in Phase III.Anticipated Results /Potential Commercial Applications as described by the awardee:This work should lead to a practical continuous cryosorption cryopump. Such a pump would be useful for contemporary and future fusion reactors, especially where continuous operation and low pumpinventory are important. A potential commercial application of this technology is for pumping of sputtering chambers for thinfilm metallization, a process used in microelectronics fabrication.