Localization of a Postulated Noise in VVER-1000 Reactor Core Using Neutron Noise Analysis Methods

Malmir, Hessam | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40250 (46)
  4. University: Sharif University of Technology
  5. Department: Energy Engineering
  6. Advisor(s): Vosoughi, Naser
  7. Abstract:
  8. In this thesis, localization of a postulated noise from limited neutron detectors sparsely distributed throughout the core of a typical VVER-1000 reactor is investigated. For this purpose, developing a 2-D neutron noise simulator for hexagonal geometries based on the 2-group diffusion approximation, the reactor dynamic transfer function is calculated. The box-scheme finite difference method is first developed for hexagonal geometries, to be used for spatial discretisation of both 2-D 2-group static and noise diffusion equations. Using the discretised static equations, a 2-D 2-group static simulator (HEXDIF-2) is developed which its results are benchmarked against the well-known CITATION computer code. The required group constants in different cases are calculated by the WIMSD computer code. Furthermore, the dynamic state is assumed in the frequency domain which leads to discarding of the time disrcetisation. Using the discretised noise equations, a 2-D 2-group neutron noise simulator (HEXDYN-2) is developed which calculates both the discretised forward and the adjoint reactor transfer function between a point-like source and its induced neutron noise. Although, only an “absorber of variable strength” type of noise source is considered here, the neutron noise induced by a “vibrating absorber” type of noise source may also be modeled using the calculated transfer function. Benchmarking of the mentioned neutron noise simulator revealed that it works satisfactorily. Finally, by using the inversion method of reconstruction, the location and values of a noise source of the type absorber of variable strength (or reactor oscillator) in a typical VVER-1000 reactor core are determined. Accuracy of this method is highly acceptable
  9. Keywords:
  10. Finite Difference Method ; Neutron Noise ; Box Scheme ; Hexagonal Geometries ; Adjoint Calculations ; Localization Noise

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