Two-level time-dependent GET based CMFD acceleration for 3D whole core transient transport simulation using 2D/1D method

Abstract

A pin-resolved kinetics transport simulation based on the transient fixed-source problem (TFSP) using 2D/1D method has been implemented in this work. The 3D transient fixed source problem is transformed into 2D TFSP and 1D TFSP coupled by the leakage term, while the MOC method and NEM method are used to solve the 2D and 1D TFSP respectively. And a global pin-level time-dependent generalized equivalence theory (GET) based coarse mesh finite difference method (CMFD) is used to synthesize the 2D radial MOC and 1D axial NEM transient calculations, and also to accelerate the iteration convergence of 3D whole-core transient transport calculation. Even more important, an advanced yet accurate two-level time-dependent CMFD acceleration technique is proposed, in which an equivalent one-group CMFD is established to accelerate the multi-group CMFD TFSP solutions, and then to accelerate the 3D whole-core transient transport calculation efficiently. 2D TWIGL and 3D C5G7-TD benchmarks are selected to verify the accuracy and the acceleration effect of the 2D/1D method and the two-level CMFD acceleration. Numerical results indicate that acceptable accuracy of 2D/1D transient calculations and superior acceleration of TL CMFD are achieved.