APEC-based nodal methodology for consistent and accurate CANDU core analysis

Abstract

This thesis is concerned with an improved two-step methodology based on the nodal equivalence theory for more accurate and consistent CANDU reactor analysis. In addition, the albedo-corrected parameterized equivalence constants (APEC) method is introduced to achieve further improvement of the nodal solution by correcting the burnup-dependent cross sections (XSs) and discontinuity factors (DFs). The APEC algorithm is incorporated into an in-house nodal expansion method (NEM) code in conjunction with the partial-current based CMFD (p-CMFD) acceleration. Color-set calculations are performed to obtain physically meaningful leakage information of the fuel lattice, which is subsequently used for generating the burnup dependent APEC functions to correct the group XSs. Using the color-set solutions, NEM-equivalent DFs are calculated for a coarse-mesh (1×1 mesh per fuel assembly) and they are used for the generation of APEC functions for the DF correction. A separate set of burnup-dependent APEC functions are generated for the fuel lattice loaded with a reactivity device. Both position- and burnup-dependent APEC functions for XSs and DFs are applied for accurate CANDU core analysis. A 2-D CANDU whole core nodal analysis is performed to show the performance of the APEC-assisted nodal analysis of CANDU core. Moreover, various core configurations are also analyzed with the same APEC functions to show the generality of the APEC functions. In addition, nodal calculation of a realistic CANDU core with reactivity device is performed with the APEC method to obtain the nodal equivalence. The nodal analyses showed that the APEC-based two-step nodal methodology can provide an accurate and consistent CANDU analysis.