Approximate Three-Dimensional Correction Factors in Two-Dimensional Reactor Calculations

Three-dimensional (3D) correction factors designed to take into account the heterogeneity effects of the missing dimension in two-dimensional (2D) reactor computation are rigorously defined. An approximate method for computing the 3D correction factors is proposed by introducing simplified model cores. For verification of the proposed method, 2D and 3D ROCS code computations are performed for the first three cycles of the Yonggwang Unit 2 pressurized water reactor. The utility of the proposed method is then discussed by demonstrating that the 2D ROCS results with the use of the approximate 3D correction factors agree well with the 3D ROCS results in the letdown behavior of the critical soluble boron concentration and the core power distribution.