The 3-D time-dependent transport code TORT-TD and its coupling with the 3D thermal-hydraulic code ATTICA3D for HTGR applications

The application of the time-dependent 3-D discrete-ordinates neutron transport code TORT-TD to HTGR of pebble bed type and its coupling with the 3-D thermal-hydraulic code ATTICA3D is described. TORT-TD, developed at GRS, solves the time-dependent multi-group SN transport equation in both Cartesian and curvilinear geometry using a fully implicit time discretization scheme. To provide a detailed 3-D core model for pebble bed type HTGRs, TORT-TD has been coupled with the 3-D thermal-hydraulic code ATTICA3D which is developed at IKE, University of Stuttgart. ATTICA3D provides a 3-D modeling of heat conduction and convection using a porous media approach. In this paper, the TORT-TD/ATTICA3D coupling methodology is described. The PBMR-268 and PBMR-400 benchmark problems have been chosen as first test cases for TORT-TD and the coupled code TORT-TD/ATTICA3D. In TORT-TD, the control rods in the side reflector have been modeled both as grey curtain and spatially resolved. Results for first coupled steady-state and transient calculations of the PBMR-400 benchmark are shown.