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Fusion Science and Technology
Latest News
Norway’s Halden reactor takes first step toward decommissioning
The government of Norway has granted the transfer of the Halden research reactor from the Institute for Energy Technology (IFE) to the state agency Norwegian Nuclear Decommissioning (NND). The 25-MWt Halden boiling water reactor operated from 1958 to 2018 and was used in the research of nuclear fuel, reactor internals, plant procedures and monitoring, and human factors.
Dennis L. Youchison, Alex M. Melin, Arnold Lumsdaine, Charles R. Schaich, Gregory R. Hanson
Fusion Science and Technology | Volume 72 | Number 3 | October 2017 | Pages 324-330
Technical Paper | doi.org/10.1080/15361055.2017.1333855
Articles are hosted by Taylor and Francis Online.
The electron cyclotron heating system (ECH) on ITER uses 24 evacuated microwave transmission lines carrying up to 1.4 MW of power each at 170 GHz to provide resonance heating of electrons in the ITER plasma and to enable plasma current drive. A critically important component in this system is the microwave switch that allows the microwaves to be directed from the gyrotrons to either dummy loads or between launchers in the upper and equatorial ports of the ITER tokamak while maintaining the vacuum integrity of the transmission lines. A moveable, water-cooled CuCrZr mirror is used to redirect the microwave transmission between two orthogonal waveguides.
In this article we describe the optimized design of the mirror cooling passages produced by computational fluid dynamics analysis using ANSYS CFX with k-ε and k-ω shear stress transport turbulence models, and verify that the design parameters for mass flow rate, inlet temperature and pressure are adequate for good thermomechanical performance. Non-uniform heating of the mirror face from the incident microwaves induces deflections that should be less than 25 microns to meet the integrated transmission line efficiency specification. In the current 1.4 MW switch design, 0.03 kg/s of 36°C water at 10 bar inlet pressure can remove the 2660 W of ohmic heating in the mirror produced by the elliptical polarization power and maintain the surface temperature below 150°C. The water delta-T is 21°C with a 0.5 bar pressure drop in the mirror. The maximum predicted displacement in the center of the mirror face is less than 25 μm.