WIMS-IST/DRAGON-IST Side-Step Calculation of Reactivity Device and Structural Material Incremental Cross Sections for Wolsong NPP Unit 1

Abstract

This paper describes the calculation of two-group incremental cross sections for all of the reactivity devices and in-core structural materials for an RFSP-IST full-core model of Wolsong NPP Unit 1, in support of the conversion of the reference plant model to two energy groups. This is of particular interest since the calculation used the new standard “side-step” approach, which is a three-dimensional supercell method that employs the Industry Standard Toolset (IST) codes DRAGON-IST and WIMS-IST with the ENDF/B-VI nuclear data library. In this technique, the macroscopic cross sections for the fuel regions and the device material specifications are first generated using the lattice code WIMS-IST with 89 energy groups. DRAGON-IST then uses this data with a standard supercell modelling approach for the three-dimensional calculations.Incremental cross sections are calculated for the stainless-steel adjuster rods (SS-ADJ), the liquid zone control units (LZCU), the shutoff rods (SOR), the mechanical control absorbers (MCA) and various structural materials, such as guide tubes, springs, locators, brackets, adjuster cables and support bars and the moderator inlet nozzle deflectors. Isotopic compositions of the Zircaloy-2, stainless steel and Inconel X-750 alloys in these items are derived from Wolsong NPP Unit 1 history dockets. Their geometrical layouts are based on applicable design drawings. Mid-burnup fuel with no moderator poison was assumed. The incremental cross sections and key aspects of the modelling are summarized in this paper.