EFFECT OF THE UNIFORM FISSION SOURCE METHOD ON LOCAL POWER VARIANCE IN FULL CORE SERPENT CALCULATION

Yurii Bilodid,Jaakko Leppänen,M Margulis,P Blaise

doi:10.1051/epjconf/202124704024

Abstract

One of challenges of the Monte Carlo full core simulations is to obtain acceptable statistical variance of local parameters throughout the whole reactor core at a reasonable computation cost. The statistical variance tends to be larger in low-power regions. To tackle this problem, the Uniform-Fission-Site method was implemented in Monte Carlo code MC21 and its effectiveness was demonstrated on NEA Monte Carlo performance benchmark. The very similar method is also implemented in Monte Carlo code Serpent under the name Uniform Fission Source (UFS) method. In this work the effect of UFS method implemented in Serpent is studied on the BEAVRS benchmark which is based on a real PWR core with relatively flat radial power distribution and also on 3x3 PWR mini-core simulated with thermo-hydraulic and thermo-mechanic feedbacks. It is shown that the application of the Uniform Fission Source method has no significant effect on radial power variance but equalizes axial distribution of variance of local power.

Highlights

The Monte Carlo codes, often coupled with depletion, thermal-hydraulic and thermal-mechanic solvers, are increasingly applied for full core reactor simulations
The geometry and material specification for a test case could be found in the BEAVRS benchmark definition [6]
The Uniform Fission Source (UFS) method implemented in Serpent redistributes fission source to equalize variance of the local tallies thought the reactor core

Summary

INTRODUCTION

The Monte Carlo codes, often coupled with depletion, thermal-hydraulic and thermal-mechanic solvers, are increasingly applied for full core reactor simulations. The relative error tends to be larger in low-power regions as compared to high-power regions. To tackle this problem, the Uniform-Fission-Site method [1] was implemented in Monte Carlo code MC21 [2] and its effectiveness was demonstrated on NEA Monte Carlo performance benchmark [3]. The very similar method is implemented in Monte Carlo code Serpent [4] under the name Uniform Fission Source (UFS) method [5]. This work describes the implementation of UFS in combination with fission source convergence acceleration (SCA) method [7] in Serpent and investigates the effect of UFS method on the BEAVRS benchmark [6], based on realistic PWR core

UFS IMPLEMENTATION IN SERPENT

BEAVRS hot zero power test

CONCLUSIONS