UNCERTAINTY QUANTIFICATION IN STEADY STATE SIMULATIONS OF A MOLTEN SALT SYSTEM USING POLYNOMIAL CHAOS EXPANSION ANALYSIS

Mario Santanoceto,Sandra Dulla,Danny Lathouwers,Marco Tiberga,Zoltán Perkó

doi:10.1051/epjconf/202124715008

Abstract

Uncertainty Quantification (UQ) of numerical simulations is highly relevant in the study and design of complex systems. Among the various approaches available, Polynomial Chaos Expansion (PCE) analysis has recently attracted great interest. It belongs to nonintrusive spectral projection methods and consists of constructing system responses as polynomial functions of the stochastic inputs. The limited number of required model evaluations and the possibility to apply it to codes without any modification make this technique extremely attractive. In this work, we propose the use of PCE to perform UQ of complex, multi-physics models for liquid fueled reactors, addressing key design aspects of neutronics and thermal fluid dynamics. Our PCE approach uses Smolyak sparse grids designed to estimate the PCE coefficients. To test its potential, the PCE method was applied to a 2D problem representative of the Molten Salt Fast Reactor physics. An in-house multi-physics tool constitutes the reference model. The studied responses are the maximum temperature and the effective multiplication factor. Results, validated by comparison with the reference model on 103 Monte-Carlo sampled points, prove the effectiveness of our PCE approach in assessing uncertainties of complex coupled models.

Highlights

The Molten Salt Fast Reactor (MSFR) is one of the six new concept reactors proposed by the Generation IV International Forum
This paper has presented an application of a Polynomial Chaos Expansion (PCE) method to complex, multi-physics models for liquid fueled reactors, addressing key design aspects of neutronics and thermal fluid dynamics
The PCE method is based on a Non-Intrusive Spectral Projection approach and Smolyak sparse grids designed to estimate the PCE coefficients

Summary

INTRODUCTION

The Molten Salt Fast Reactor (MSFR) is one of the six new concept reactors proposed by the Generation IV International Forum. This reactor requires strong efforts in R&D, both from the experimental and the numerical point of view, due to the early stage of development In this perspective, Uncertainty Quantification (UQ) is a powerful tool to assess the sensitivity of key design aspects to the variation of intrinsically uncertain input parameters. Knowing the inputs’ statistical information, the PCE meta-model is created by choosing a set of polynomial basis vectors, and using Smolyak sparse grid based numerical integration to compute the basis coefficients [6].

POLYNOMIAL CHAOS EXPANSION METHOD

TEST PROBLEM: A SIMPLIFIED MOLTEN SALT REACTOR SYSTEM

RESULTS

Analysis of Responses

CONCLUSIONS