Backup Calculations for Shutdown Margin Determination for NUSAR

摘要

Part of the physics evaluations in support of the N Reactor Updated Safety Analysis Report (NUSAR) consisted of verifying sufficient shutdown margin capability using the exposure dependent rod and ball safety system strengths which were developed for NUSAR. These studies also consisted of determining the excess reactivity and the reactivity balance for various core conditions. This document describes the equations and assumptions used to determine the reactivity balance and shutdown margins used in Sections 4.3 and 15.4 of NUSAR. The reactivity balance and the shutdown margins for the rod and ball safety systems are given. It is shown how the shutdown margin varies as a function of fuel exposure for the rod and ball safety systems. The variation in rod shutdown margin during a reactor startup and ascension to full power and the rod shutdown margin at the minimum point during the power ascension are presented. (ERA citation 04:019166)