Parametric Study of Different Perturbations on Ringhals Stability Benchmark With RELAP5/PARCS Coupled Code

Abstract

The analysis of power instabilities were tackled many years ago developing new methodologies to model this phenomena. The mechanisms underlying the causes of the power oscillations in BWR are still under study, but its consequences are well known. The simulation of the instabilities using best-estimate codes is the aim of this work.Three dimensional time domain BWR stability analysis has been performed in Ringhals 1 NPP, using the coupled code RELAP5-MOD3.3/PARCS v2.7. In the simulation of instabilities, it is necessary to introduce some perturbations that make the power oscillate. In this work, the instabilities are induced by means of density perturbations using a new capability introduced in the neutronic code. The applied perturbation is based on the Lambda modes and their amplitudes.This new option permits the user to perturb the moderator density in each node at each time step. Using different amplitudes for the perturbation signal the user is able to perform a complete stability analysis studying the resulting power oscillations.