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Investigation and Simulation of Rapid Changes in NPPs Power using System Codes (Case Study of Bushehr power plant)

Asgari, Elham | 2024

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 57236 (46)
  4. University: Sharif University of Technology
  5. Department: Energy Engineering
  6. Advisor(s): Ghaffari, Mohsen
  7. Abstract:
  8. Among nuclear power plants, it is no secret that PWRs are extremely popular due to their high power density. Among the prominent features of this type of power plants is the mutual influence of the thermal characteristics of the first and second circuits on each other. Also, due to the existence of thermal feedbacks in the heart and the influence of neutronic power on it, it will not be possible to change the power as easily as in other thermal power plants. A change in the thermal characteristics of the power plant occurs in normal, start-up and accident conditions and can cause a change in the control algorithm of the power plant. During start-up, performing relevant tests and operation, it has been observed that some incidents are associated with rapid power change transients. Investigating the power plant's behavior in transitions that are associated with rapid power changes and the origin of which is the second circuit requires an efficient model. Using an efficient model can play an essential role in identifying the general behavior of systems and equipment. In the mentioned model, a significant part of the turbine control system, reactor and the entire power plant should be modeled efficiently. In the previous actions surrounding the simulation of such transitions, the main attention was focused on the changes of the first circuit and the operational role of the steam pipeline and its safety valves was neglected. In this project, an attempt has been made to correct the shortcomings of the faculty model by correctly simulating the safety valves and paying attention to the operational role of the steam pipeline when such incidents occur. In order to measure the accuracy of the modeling of the steam pipeline and safety valves, a "SB-LOCA" design basis accident and a "power turbine load reduction" start-up test have been used. Due to the short time interval of power change, only the RELAP code has a short execution time among the system codes. Therefore, this code has been used for modeling. After modeling the safety valves and common steam line, the SB-LOCA accident and power turbine load reduction start-up test have been used to validate the model. Examining the results of modeling with Bushehr power plant safety documents and the practical data of the start-up test shows that the objectives of these transitions have been successfully implemented. In the end, the transition of rapid power change is modeled and the results of this modeling show that such transitions can be simulated by using the RELAP code, and by coupling this code with a neutronic code such as PARCS, the accuracy of the results can be increased
  9. Keywords:
  10. Bushehr Nuclear Power Plant ; Load Reduction Test ; RELAP5 Code ; SB-LOCA Accident ; Rapid Power Change Transition ; Safety Valves

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