Investigation of a discrete ordinates method for neutron noise simulations in the frequency domain
Doctoral thesis, 2021

During normal operations of a nuclear reactor, neutron flux measurements show small fluctuations around mean values, the so-called neutron noise. These fluctuations may be driven by a variety of perturbations, e.g., mechanical vibrations of core components. From the analysis of the neutron noise, anomalous patterns can be identified at an early stage and corrected before they escalate. For this purpose, the modelling of the reactor transfer function, which describes the core response to a possible perturbation and is based on the neutron transport equation, is often required. In this thesis a discrete ordinate method is investigated to solve the neutron noise transport equation in the frequency domain. When applying the method, two main issues need to be considered carefully, i.e., the performance of the numerical algorithm and possible numerical artifacts arising from the discretization of the equation. For an efficient numerical scheme, acceleration techniques are tested, namely, the synthetic diffusion acceleration and various forms of the coarse mesh finite difference method. To reduce the possible numerical artifacts, the impact of the order of discrete ordinates and the use of a fictitious source method are studied. These analyses serve to develop the higher-order neutron noise solver NOISE-SN. The solver is compared with different solvers and used to simulate neutron noise experiments carried out in the research reactor CROCUS (at EPFL). The solver NOISE-SN is shown to provide results that are consistent with the results obtained from other higher-order codes and can reproduce features observed in neutron noise experiments.

Deterministic neutron transport

Neutron noise

Ray effects

Numerical acceleration

Discrete ordinates method

Author

Huaiqian Yi

Subatomic, High Energy and Plasma Physics PP

Included papers

On the simulation of neutron noise using a discrete ordinates method

Annals of Nuclear Energy,;Vol. 164(2021)

Journal article

Comparison of neutron noise solvers based on numerical benchmarks in a 2-D simplified UOX fuel assembly

Proc. Int. Conf. Mathematics and Computational Methods Applied to Nuclear Science and Engineering (M&C2021),;(2021)

Paper in proceeding

Acceleration of a 2-dimensional, 2-energy group neutron noise solver based on a discrete ordinates method in the frequency domain

International Conference on Physics of Reactors: Transition to a Scalable Nuclear Future, PHYSOR 2020,;Vol. 2020-March(2020)p. 2922-2929

Paper in proceeding

A discrete ordinates solver with diffusion synthetic acceleration for simulations of 2-D and 2-energy group neutron noise problems

International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering, M and C 2019,;(2019)p. 2023-2032

Paper in proceeding

Neutron noise simulations in a heterogeneous system: A comparison between a diffusion-based and a discrete ordinates solver

International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering, M and C 2019,;(2019)p. 439-448

Paper in proceeding

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Research Project(s)

Core monitoring techniques and experimental validation and demonstration (CORTEX)

European Commission (EC) (EC/H2020/754316), 2017-09-01 -- 2021-08-31.

Categorizing

Areas of Advance

Energy

Subject Categories (SSIF 2011)

Other Physics Topics

Identifiers

ISBN

978-91-7905-606-3

Other

Series

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5072

Publisher

Chalmers

Public defence

2022-01-28 09:30 -- 13:00

PJ Lecture room, Fysik Origo, Fysikgården 2B, Chalmers University of Technology, Göteborg

Online

Opponent: Professor Jean Ragusa, Texas A&M University, Texas, United States

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Latest update

3/2/2022 1