Title:
Thermo-Fluids Perfromance of Helium Cooled Divertors Emphasizing Plate-Type Concepts
Thermo-Fluids Perfromance of Helium Cooled Divertors Emphasizing Plate-Type Concepts
Author(s)
Lee, Daniel Seokjun
Advisor(s)
Yoda, Minami
Abdel-Khalik, Said
Abdel-Khalik, Said
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Abstract
The magnetic fusion energy (MFE) tokamak reactor, which confines a high temperature plasma within a torus shaped chamber by means of magnetic fields, is one of the most promising and best developed concepts for making nuclear fusion energy possible. One of the challenges in current long-pulse MFE reactors is overcoming the extreme conditions at the first wall of the reactor chamber, where plasma facing surfaces are subject to very high heat fluxes. The divertor is a magnetic field configuration that enables removal of impurities and fusion products from the core plasma by impingement on solid surfaces. The solid target plates of the divertor, which are directly exposed to the plasma and very high heat fluxes of at least 10 MW/m^2, must therefore be cooled so that they do not melt and contaminate the plasma. In addition, about 20% of the total energy produced by the fusion reaction is absorbed by plasma facing surfaces including the divertor targets, and therefore it is important to have a cooling system that can recover this energy. Several designs for cooling the divertor targets have been proposed, and most use helium to cool the back side of the target plates with impinging jets. This doctoral thesis details experimental and numerical studies to estimate the cooling capabilities and required pumping power under prototypical conditions of a number of helium cooled divertor designs, specifically the helium-cooled flat plate (HCFP) divertor, helium-cooled modular divertor with multiple jets (HEMJ), and a “flat design” which is a simplified variant of the HEMJ. Experiments were performed over He mass flow rate ranging from 3 to 10 g/s in helium loops operating at the prototypical pressure of 10 MPa, and elevated helium inlet temperatures as high as 400 °C and incident heat fluxes as high as 8.1 MW/m^2. Numerical simulations using commercial software, validated by these experimental data, complement these experimental studies and are used to extrapolate the thermo-fluids performance to fully prototypical conditions. The results are used to develop “parametric design curves” to allow designers of He-cooled divertors to estimate the maximum allowable heat flux and the corresponding pumping power requirements at different coolant flow rates for a specified limit on the maximum surface temperature of the pressure boundary.
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Date Issued
2023-08-17
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Text
Resource Subtype
Dissertation