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International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering (M&C 2025)
April 27–30, 2025
Denver, CO|The Westin Denver Downtown
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Sam Altman steps down as Oklo board chair
Advanced nuclear company Oklo Inc. has new leadership for its board of directors as billionaire Sam Altman is stepping down from the position he has held since 2015. The move is meant to open new partnership opportunities with OpenAI, where Altman is CEO, and other artificial intelligence companies.
Michael L. Lanahan, Said I. Abdel-Khalik, Minami Yoda
Fusion Science and Technology | Volume 80 | Number 1 | January 2024 | Pages 108-116
Research Article | doi.org/10.1080/15361055.2023.2198046
Articles are hosted by Taylor and Francis Online.
Several studies at the Georgia Institute of Technology have evaluated the thermal and fluids performance of the helium-cooled modular divertor with multiple jets (HEMJ) over the past decade. This finger-type divertor was studied both experimentally at nearly prototypical conditions and numerically at fully prototypical operating conditions using experimentally validated simulations. Recently, supercritical carbon dioxide (sCO2) has been studied as the primary coolant in power cycles and other applications in various systems, in part because CO2 achieves the high densities typical of supercritical fluids at relatively low temperatures and pressures, with a critical point of (7.38 MPa, 31°C). This density makes it possible to realize very compact and efficient sCO2 power cycles. The feasibility of sCO2 as a coolant for plasma-facing components, specifically the divertor, was therefore evaluated as part of the Fusion Energy System Studies design study activities. This work compares the thermal-fluid performance of helium and sCO2 in the HEMJ divertor geometry using numerical simulations at prototypical conditions: inlet temperatures Ti = 600°C to 700°C, pressures p ≈ 10 MPa, and steady-state incident heat fluxes on the tile q″ < 17 MW/m2. The performance is quantified here as the maximum heat flux that can be accommodated by the plasma-facing tile, the pumping power fraction, defined as the ratio of the coolant pumping power to the incident thermal power, and the operating stress limits based on ASME pressure vessel criteria. As expected, helium requires lower mass flow rates and pumping power fractions within imposed maximum temperature limits for the HEMJ pressure boundary. However, it also appears that neither helium nor sCO2 can remove 10 MW/m2 of incident heat flux while meeting ASME pressure vessel criteria. Finally, the numerical modeling reveals that sCO2 may remove slightly higher incident heat fluxes than helium due to the imposed stress limits due to the sCO2 coolant resulting in smaller local temperature gradients, albeit at a considerably higher pumping power fraction.