Examination of Core Neutronic Data Generated with the CASL Tools and Impacts on Ex-Core Neutron Exposure Calculations

The Consortium for Advanced Simulation of Light Water Reactors (known as CASL) is A U.S. Department of Energy program initiated to develop core neutronic, thermal-hydraulic, and crud transport tools based on higher-order methods than those that currently support the operating fleet of nuclear power plants. The objective is to try to find ways to improve plant performance. Core depletion calculations modeling several operating commercial nuclear reactors have been performed with the Consortium tool suite called the Virtual Environment for Reactor Analysis, or VERA. The data from these calculations provide a basis for comparison against currently used data and outputs from existing core neutronics codes. This paper compares predictions of pin power distributions generated by VERA with predictions from nodal diffusion-based core neutronics codes that are used for production calculations and with generic pin power distributions typically used as inputs to dosimetry analyses. The resulting impacts on subsequent neutron transport calculations are provided. The consistency of the VERA-predicted pin power distributions in the axial direction is examined. Axial power distributions calculated by VERA are compared to calculations from the Westinghouse Advanced Nodal Code, and the core-averaged axial power distribution is compared to distributions computed for specific peripheral assemblies calculated by VERA. Taken together, these comparisons provide insight into the degree to which widely used methodological approximations, such as diffusion theory in the core design process, are able to generate accurate predictions of necessary input parameters for fluence and dosimetry analysis.