Nuclear Technology / Volume 158 / Number 1 / April 2007 / Pages 36-55
Technical Paper / Best Estimate Methods
The subject of this paper is estimation of the maximum values of the heat flux at steady-state nominal operating conditions in the Belgian Material Test Reactor (BR2) at SCK-CEN in Mol. A strong variation of the fuel depletion and the heat flux with the azimuthal direction and dependence on the orientation of the fuel element in the core are obtained. The full-scale three-dimensional (3-D) MCNP&ORIGEN-S heterogeneous geometry model of BR2 with a detailed 3-D isotopic fuel depletion profile, including a detailed azimuthal fuel modeling in the annular concentric plate fuel elements, is used to evaluate the variation of the heat flux with the azimuthal direction in the hot plane. The relative azimuthal power distribution is calculated with MCNP and introduced into ORIGEN-S to evaluate the azimuthal isotopic fuel profile. The applied detailed azimuthal fuel modeling is compared with homogeneous fuel depletion in the hot plane. An increase of the maximum value of the heat flux of 5% for low burnt fuel and 20% for highly burnt fuel due to the azimuthal modeling of the fuel depletion is obtained. A strong variation of the heat flux with the orientation of the fuel element in the core, modeled with the azimuthal fuel profile, is observed. Perturbation effects in the maximum value of the heat flux of 10% for low burnt fuel and up to 40% for highly burnt fuel, correlated to different orientations of the fuel element in the core, are obtained.