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Dinkel, Christian ; Frisch, Michael ; Roith, Bernd ; Rieg, Frank:
Examination of heat transfer mechanisms in nuclear fuel casks by using CFD simulation.
In:
NAFEMS
(Hrsg.):
Seminar: Best Practices for Thermal Analyses and Heat Transfer. -
Bernau am Chiemsee
: NAFEMS Deutschland Österreich Schweiz GmbH
,
2014
. - S. 135-144
ISBN 978-1-874376-83-5
Abstract
Transport and storage casks for nuclear fuel elements have to assure the prevention of damage caused by heat. The heat transfer in a cylindrical annulus, which exists between the inner and the outer part of the cask, is of particular interest. Therefore, CFD simulations with the software STAR-CCM+ are performed. Two geometrical effects are examined in vertically positioned casks due to unknown manufacturing tolerances and different thermal expansion. First, the influence of the gap width is simulated. Thereby, no convection flow occurs for gap sizes smaller than 2 mm. The stream in gap sizes smaller than 5 mm can also be neglected because of very low velocities. If the gap becomes very small, heat conduction is privileged which leads to lower temperatures. Even lower temperatures occur in case of a 10 mm sized annulus because a convection flow improves the thermal transport.
Secondly, off-centered positions of the inner cask part are possible, which leads to an unequal annulus size along the circumference. In extreme cases, a contact condition arises between inner and outer cask part. As a result, the heat transfer in this point is very good and causes lower temperatures, whereas the heat transfer within the remaining, growing gap declines.
If casks in vertical and horizontal position are compared, lying fuel casks show significant higher maximum temperatures. A worse convection flow within the gap because of the contact condition and a restricted air flow around the outer surface of the cask are responsible for this temperature increase.