Thermal Analysis to Calculate the Vessel Temperature and Stress in Alcator C-Mod Due to the Divertor Upgrade
Authors: Han Zhang, Peter H. Titus, Robert Ellis, Soren Harrison and Rui Vieira
Abstract:
Alcator C-Mod is planning an upgrade to its outer
divertor. The upgrade is intended to correct the existing
outer divertor alignment with the plasma, and to operate
at elevated temperatures. Higher temperature operation
will allow study of edge physics behavior at reactor
relevant temperatures. The outer divertor and tiles will be
capable of operating at 600oC. Longer pulse length,
together with the plasma and RF heat of 9MW, and the
inclusion of heater elements within the outer divertor
produces radiative energy which makes the sustained
operation much more difficult than before. An ANSYS
model based on ref. 1 was built for the global thermal
analysis of C-Mod. It models the radiative surfaces inside
the vessel and between the components, and also includes
plasma energy deposition. Different geometries have been
simulated and compared. Results show that steady state
operation with the divertor at 600oC is possible with no
damage to major vessel internal components. The
differential temperature between inner divertor structure,
or "girdle" and inner vessel wall is ~70oC. This
differential temperature is limited by the capacity of the
studs that hold the inner divertor backing plates to the
vessel wall. At a 70oC temperature differential the stress
on the studs is within allowable limits. The thermal model
was then used for a stress pass to quantify vessel shell
stresses where thermal gradients are significant.
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Submitted to: ANS Journal, Fusion Science and Technology (August 2012) and 20th Topical Meeting on the Technology of Fusion Energyy, Nashville, TN (Aug. 27-31, 2012)
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Download PPPL-4802 (pdf 3.42 MB 5 pp)
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