Space–time convergence analysis on BWR stability using TRACE/PARCS

Unstable behavior of Boiling Water Reactors (BWRs) is known to occur during operation at certain power and flow conditions. Even though BWR instability is not a severe safety concern, it could cause reactor scram and significantly decrease the economic performance of the plant. This paper aims to (a) quantify TRACE/PARCS space–time discretization error for simulation of BWR stability, (b) establish space (nodalization) and time discretization necessary for space–time converged model and (c) show that the space–time converged model gives more reliable results for both stable and unstable reactor. The space–time converged model is obtained when further refinement of numerical discretization parameters (nodalization and time step) has negligible effect on the solution. The study is significant because performing a space–time convergence analysis is a necessary step of qualification of the TRACE/PARCS model, and use of the space–time converged model increases confidence in the prediction of BWR stability.

► Quantify TRACE/PARCS space–time discretization error for BWR stability prediction.
► Establish space and time discretization necessary for space–time converged models.
► Show that the space–time converged model gives more reliable results for both stable and unstable reactor.
► Use of the space–time converged model increases confidence in the prediction of BWR stability.