PLNGS Training Simulator Reflector Model Corrections

Abstract

An additional guaranteed shutdown state, Rod-Based Guaranteed Shutdown State (RBGSS) had been proposed at Point Lepreau Generating Station (PLNGS). RBGSS is implemented by locking all solid rods in-core and provides significant safety benefits such as decreased time required to become critical and decreased doses to the workers. The most reactive states for RBGSS in PLNGS have been determined and assessed by reactivity balance calculations for the planned outage in 2017. PLNGS decided to use RBGSS for stable sub-critical state. The PLNGS full-scope real-time training simulator core model uses nodal expansion based on diffusion theory and the reflector model is not sophisticated enough for highly absorbing subcritical core response. In order to deliver the necessary just-in-time training to Certified Operating staff, corrections to the reflector model were required. Specifically, modifications were required to model the process of establishing and removing RBGSS during which the best measure of the reactor power is the ion chamber readings located outside the core. This paper discusses the modifications to the existing PLNGS training simulator reflector model to obtain a high fidelity response for a deeply subcritical core.