SBIR-STTR Award

Fusion reactors based on magnetic confinement of plasmas require active pumping and fueling to replenish the deuterium-tritium which escapes the plasma and to remove the helium which is produced during the burn. Cryogenic pumps and frozen pellet injection are the most efficient means of pumping and refueling the tokamak plasma during the burn cycle. However, since tritium is a radioactive gas it is important to limit the total trituim inventory of the reactor to a minimum. A low inventory pumping and fueling system based on a continuous cryopump technology will be assembled and fully tested with tritium at the Los Alamos National Laboratory Tritium System Test Assembly (LANL/TSTA). The continuous cryopump fuel cycle will have reduced inventories since the system removes and directly re-injects 95% of the deuterium-tritium fuel back into the plasma as pellets. The remaining deuterium-tritium and helium will be pumped by a charcoal cryosorption pump developed at LANL/TSTA and processed through the TSTA isotope separation system. Phase I will produce a detailed design and analysis of the combined system. The design will include modifications required to integrate a charcoal cryosorption pump into the existing continuous cryopump, a layout of the system integrated into the TSTA tritium facility, and a detailed analysis of the tritium containment system. The analysis will simulate the performance of the system for design optimization and failure mode prediction.

Commercial Applications and Other Benefits as described by the awardee:
A practical low inventory tritium fuel cycle should reduce the tritium inventory in a fusion reactor by 50% and reduce the refrigeration requirements by a factor of 28 compared to current cryopump designs. This will dramatically reduce the complexity and cost of the pumping and fueling systems while enhancing reactor safety. The continuous cryopump technology could also be used to improve performance and reduce costs of conventional pumps used in micro-electronic fabrication.

Fusion reactors based on the magnetic confinement of plasmas will require active pumping and fueling to both replenish the deuterium-tritium (D/T) that escapes from the plasma and remove the helium produced during the burn cycle. Cryogenic pumps and frozen pellet injection are the most efficient means of pumping and refueling the reactor; however, it is important to minimize the amount of tritium in the reactor, since tritium is a radioactive gas. This project will utilize continuous cryopump technology to rapidly pump, purify, and return 95% of the D/T fuel back into the plasma as pellets, leading to a fuel cycle with reduced inventories. Remaining D/T and helium will be pumped by a previous developed charcoal cryosorption pump. The phase I project produced a design which integrates the charcoal cryosorption pump into the continuous cryopump. A preliminary tritium containment and failure mode analysis was conducted for the integrated system. In Phase II, a charcoal cryosorption pump stage will be constructed, installed in the cryopump, and tested with D2 and He. A series of experiments will be conducted to document and demonstrate system performance.

Commercial Applications and Other Benefits as described by the awardee:
The system should reduce the tritium inventory by 50% and reduce the refrigeration requirements by factors of 28 compared to conventional cryopump designs. This should reduce complexity and cost while enhancing reactor safety. The technology should also have applicability to micro-electronic fabrication.