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Publication . Doctoral thesis . Thesis . Other literature type . 2020

A neutron noise solver based on a discrete ordinates method.

Yi, Huaiqian;
Open Access
Published: 01 Apr 2020
Publisher: Zenodo
Country: Sweden

A neutron noise transport modelling tool is presented in this thesis. The simulator allows to determine the static solution of a critical system and the neutron noise induced by a prescribed perturbation of the critical system. The simulator is based on the neutron balance equations in the frequency domain and for two-dimensional systems. The discrete ordinates method is used for the angular discretization and the diamond finite difference method for the treatment of the spatial variable. The energy dependence is modelled with two neutron energy groups. The conventional inner-outer iterative scheme is employed for solving the discretized neutron transport equations. For the acceleration of the iterative scheme, the diffusion synthetic acceleration is implemented. The convergence rate of the accelerated and unaccelerated versions of the simulator is studied for the case of a perturbed infinite homogeneous system. The theoretical behavior predicted by the Fourier convergence analysis agrees well with the numerical performance of the simulator. The diffusion synthetic acceleration decreases significantly the number of numerical iterations, but its convergence rate is still slow, especially for perturbations at low frequencies. The simulator is further tested on neutron noise problems in more realistic, heterogeneous systems and compared with the diffusion-based solver. The diffusion synthetic acceleration leads to a reduction of the computational burden by a factor of 20. In addition, the simulator shows results that are consistent with the diffusion-based approximation. However, discrepancies are found because of the local effects of the neutron noise source and the strong variations of material properties in the system, which are expected to be better reproduced by a higher-order transport method such as the one used in the new solver.


Neutron noise, nuclear reactor modelling, Deterministic neutron transport methods, Discrete ordinates, Diffusion synthetic acceleration, Convergence analysis, Other Engineering and Technologies not elsewhere specified, Other Physics Topics, diffusion synthetic acceleration, nuclear reactor modelling, deterministic neutron transport methods, neutron noise, convergence analysis, discrete ordinates

Related Organizations
Funded by
Core monitoring techniques and experimental validation and demonstration
  • Funder: European Commission (EC)
  • Project Code: 754316
  • Funding stream: H2020 | RIA
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Chalmers Research
Doctoral thesis . 2020