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Investigating the Propagation of Thermal-hydraulic Noise in PWRs in Two phases

Naghavi Dizaji, Davod | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51227 (46)
  4. University: Sharif University of Technology
  5. Department: Energy Engineering
  6. Advisor(s): Vosoughi, Naser
  7. Abstract:
  8. The core behaviour of a nuclear reactor might be fluctuated (deviations from the normal operating conditions) in operating conditions due to various reasons. Control rod vibrations and the alterations of coolant temperature and velocity could be the main reasons for the fluctuations. These fluctuations lead to neutronic flux noise and subsequently power noise. The main objective of the current thesis was to study the thermal-hydraulic noise of the PWRs in two-phase with the emphasis on VVER-1000, which is similar to the Bushehr-1 nuclear reactor. By considering the possibility of existing two-phase flow (maximum allowable quality is about 14%) in hot channel of the PWRs, thermal-hydraulic noise was investigated in two-phase condition. Thermal-hydraulic noise sources in the core of PWRs are classified to three main types: inlet coolant temperature fluctuations, inlet coolant velocity (or mass flow rate) fluctuations and reactivity fluctuations (these disturbances should be small enough to be considered as the noise source). To simulate the thermal-hydraulic noise propagation in two-phase flow, a computational program was developed for the two-phase thermal-hydraulic analysis in the steady state condition based on mass, momentum and energy conservation equations. So, the specifications of the hot channel in steady state condition was specified and then the program was developed to study the thermal-hydraulic noise in both single and two-phase flows. Furthermore, the simulation of the neutronic noise was applied based on point-kinetic approximation. Finally, coupling of the thermal-hydraulic and neutronic noise was investigated. Using the steady state solution, the thermal-hydraulic important parameters were investigated for single-phase and two-phase channels according to different power peaking factors. The magnitude and phase of some parameters were analysed in single-phase and two-phase conditions as well. Comparison of single-phase and two-phase thermal-hydraulic noise showed that the magnitude of coolant and clad surfaces’ temperature noise decrease from single-phase to two-phase and the phase diagrams deviate from the linear mode
  9. Keywords:
  10. Single Phase Flow ; Two Phase Flow ; Propagation Noise ; Pressurized Water Reactor (PWR,WWER) ; Neutron Noise ; Single-Phose Thermal- Hydraulic Noise ; Two-Phase Thermal-Hydraulic Noise

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