Dual Coolant Liquid Metal Divertor Development
The goal of the Phase I was to identify a dual coolant thermal protection system for divertors, consisting of a renewable lithium surface layer and an internal cooling system using helium microchannels. This approach represented a significant advance in the state of the art due to use of helium microchannels and the potential for reducing the scale of lithium trenches to further improve thermal performance. The secondary goals of the Phase I were to develop molybdenum diffusion bonding methods, to assess the potential for corrosion problems with bonded structures, and to evaluate wetting issues with extremely small trenches. There were several key accomplishments of the Phase I program. A helium microchannel cooling design capable of accommodating heat fluxes greater than 30 MW/m2 with low helium pressure losses was identified. An initial round of molybdenum diffusion bonding experiments was completed, and the details of the most promising approach for a second round of molybdenum diffusion bonding experiments was identified for a future effort. Corrosion experiments exposing diffusion bonded molybdenum samples to liquid lithium was completed with three samples tested at 300 °C for 100 hours and optimum test conditions for a second test under a future effort were identified. The wetting of narrow molybdenum trenches of two sizes by liquid lithium was evaluated. Sporadic wicking into the trenches was observed up to 500 °C, although more substantial wicking may require wider trenches. A design was generated for a prototype test article for entry into the UIUC Solid/Liquid Lithium Divertor Experiment (SLiDE) test facility, and fabrication of the prototype test article was initiated. An extensive set of calculations was performed to evaluate the thermal response of two designs during the Phase I program: the first design was the milli-LiMIT, with a 0.125 mm x 0.2 mm lithium trench design. The second represented a modest reduction in size from an existing 2 mm x 0.5 mm design to 1.5 mm x 0.375 mm. The Phase I results showed that even the larger trench design is capable of meeting the thermal performance goal of 30 MW/m2, and with significant margin. The larger trenches can reduce or eliminate many of the issues of the milli-LiMIT design, including fouling susceptibility, lithium corrosion, molybdenum diffusion bonding, manifold complexity, and freezing issues. They are considered a near-term solution for divertor thermal protection. The Phase I results also showed that smaller milli-LiMIT trenches are actually capable of operating at heat fluxes up to 40 MW/m2, a capability which may be important for future commercial reactors. This design will require additional work in corrosion and wetting/wicking, though the initial results in these areas suggest that both are potentially tractable. Finally, the Phase I study succeeded in showing the feasibility of using helium microchannel cooling to dissipate large heat fluxes from divertor structures. It also identified the advantages and disadvantages of large trench/single pass designs compared to small trench/multi-loop designs. This provides a spectrum of solutions for reactor designers. The Phase I approach may represent an enabling technology for divertors, and perhaps first wall structures, increasing reactor lifetime and allowing for future growth in heat dissipation requirements. It relies on proven technologies applied in an innovative way, reducing risk and maximizing the potential benefit to world energy production.
- Research Organization:
- Micro Cooling Concepts, Huntington Beach, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- SC0020685
- OSTI ID:
- 1818199
- Type / Phase:
- SBIR (Phase I)
- Report Number(s):
- DOE-MC2-20685
- Country of Publication:
- United States
- Language:
- English
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