Solving coupled problems of lumped parameter models in a platform for severe accidents in nuclear reactors

TL;DR

This paper investigates explicit and implicit coupling strategies for lumped parameter models in nuclear reactor accident simulations, aiming to improve stability and accuracy while maintaining computational efficiency.

Contribution

It introduces and analyzes new implicit coupling schemes tailored for lumped parameter models, enhancing stability and accuracy over traditional explicit methods.

Findings

Implicit schemes offer better stability than explicit ones.

The proposed schemes improve accuracy in coupled heat conduction problems.

Numerical results demonstrate the efficiency of the new coupling methods.

Abstract

This paper focuses on solving coupled problems of lumped parameter models. Such problems are of interest for the simulation of severe accidents in nuclear reactors~: these coarse-grained models allow for fast calculations for statistical analysis used for risk assessment and solutions of large problems when considering the whole severe accident scenario. However, this modeling approach has several numerical flaws. Besides, in this industrial context, computational efficiency is of great importance leading to various numerical constraints. The objective of this research is to analyze the applicability of explicit coupling strategies to solve such coupled problems and to design implicit coupling schemes allowing stable and accurate computations. The proposed schemes are theoretically analyzed and tested within CEA's procor platform on a problem of heat conduction solved with coupled lumped parameter models and coupled 1D models. Numerical results are discussed and allow us to emphasize the benefits of using the designed coupling schemes instead of the usual explicit coupling schemes.