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Neutron Noise Calculation Using High order Nodal Expansion Method

Kolali, Ali | 2019

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 52277 (46)
  4. University: Sharif University of Technology
  5. Department: Energy Engineering
  6. Advisor(s): Vosoughi, Naser
  7. Abstract:
  8. This study consists of two parts: steady state calculations and neutron noise calculations in the frequency domain for two rectangular and hexagonal geometries. In the steady state calculation, the neutron diffusion and its adjoint equations are approximated by two-dimensional coordinates in two-group energy and are solved using the average current nodal expansion method. Then, by considering the node size in the dimensions of a fuel assembly, different orders of flux expansion are investigated. For verification purposes, the calculations have been performed by power iteration method for two test problems of BIBLIS-2D and IAEA-2D. For rectangular geometry with increasing flux expansion order from zero to one and then two, the average power distribution relative error from 9.67% improved to 0.58% and for hexagonal geometry with increasing flux expansion order from zero to one, mean error of 11.36% improved to 3.52%. By comparing the results with the values reported in valid references, the accuracy of the calculations is confirmed so led to the development of S3-HACNEM software to solve the steady state neutron diffusion equation based on the high-order nodal expansion method. In the second part, the SD-HACNEM neutron noise simulator is developed based on the high-order nodal expansion method in frequency domain to solve the time-dependent neutron diffusion equation and neutron noise calculations have been done for two types of noise sources including absorber with variable strength and Inadvertent Loading and Operation of a Fuel Assembly in an Improper Position (ILOFAIP). In the neutron noise calculations, the perturbation is considered as changes in the macroscopic cross sections while changes in neutron diffusion coefficient are not considered. Neutron noise calculation validation has been done by three methods of calculating zero frequency, adjoint noise and comparison with valid references and in finally, steady state and neutron noise calculations were performed for the reactor core of bushehr VVER-1000 with S3-HACNEM and SD-HACNEM software, respectively
  9. Keywords:
  10. Nodal Expansion Method ; High Order Nodal Expansion ; Neutron Diffusion Equation ; Neutron Noise Simulator ; Hexagonal Geometries ; Rectangular Geometries

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