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Reconstruction of Noise Sources in VVER-1000 Reactors by Using Wavelet Analysis

Saberian, Sorush | 2014

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 45903 (46)
  4. University: Sharif University of Technology
  5. Department: Energy Engineering
  6. Advisor(s): Vossoughi, Nasser
  7. Abstract:
  8. Noise phenomena, which is considered as a nuisance factor, always acts as a barrier to achieve optimal performance in all systems. In Nuclear power reactors, noise can occur due to mechanical problems such as fluctuation in control rods, failure in placing Fuel assembly in their locations properly or other factors such as creation of small bubbles in moderator. Regardless of its cause, noise leaves its impact on cross section area of material within the reactor core. Change in material cross section area shows its effect in neutron flux. Although noise is a small disturbance and may not have much impact on the reactor momentarily performance itself, in case of continuity, it can leave irreversible damages on reactor core. Due to the great importance of safety issues in nuclear power reactors, identification the noise source can play a key role in reactor safety improvement. In this thesis wavelet analysis is used to reconstruct the noise source. Wavelet analysis is a new branch of pure mathematics, which in last 20 years has been more applicable and has been used in many sciences. So that it is considered as a more powerful tool than Fourier transform in signal processing and image processing issues. One application of this tool is solving integral equations, since the equation of noise sources in power reactor is the first kind of Fredholm equation, these mathematical tools are selected to be used in this project. For this purpose, among the well-known wavelet systems, Chebyshev wavelets are used. Reconstruction of noise source is investigated in two cases: first one-dimensional case, which reconstruction was performed with high accuracy under this situation, and then in two-dimensional case, that the reconstruction phase was performed with higher accuracy than other solving methods of Fredholm equation
  9. Keywords:
  10. Noise ; Wavelet Analysis ; Fredholm Integral Equation ; Vodo-Vodyanoi Energetichesky (VVER)1000 ; Source Noise ; Chebyshev Wavelets

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