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Assessment of Spray System Capability to Reduce Containment Pressure and Deposit Fission Product during Large Break Loss of Coolant Accident (Lb-Loca) without Access to Active Part of Eccs System in Bushehr Nuclear Power Plant

Etemadieh, Navid | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 53795 (46)
  4. University: Sharif University of Technology
  5. Department: Energy Engineering
  6. Advisor(s): Ghofrani, Mohammad Bagher; Saghafi, Mehdi
  7. Abstract:
  8. The capability of Bushehr nuclear power plant spray system to reduce fission product and control a specified severe accident has been investigated in this study. In order to evaluate spray system in one of the worst cases for containment, we have chosen Large Break Loss of Coolant Accident (LB-LOCA) without access to active part of ECCS system. We have only simulated containment, so the leakage of various materials from core and primary circuit of nuclear power plant are considered as the boundary conditions for simulation. Following the Fukushima accident in 2011, many nuclear safety legislative groups concentrated on using mobile equipment which is essential for nuclear power plants these days. Achieving a full scenario by using portable equipment, we have used a mobile pump to revive the spray system. Calculations related to the flow mass of this pump have been performed to meet the needs of the spray system of Bushehr nuclear power plant. With the purpose of calculating the exact recovery time of the spray system, the accident was modeled without the operation of spray system. To suggest the appropriate recovery time for spray system, a safety criterion has been considered to avoid reaching the ultimate pressure of containment. For more detailed evaluation of the spray system, two different operating modes including: the activation of one spray train and the activation of both spray trains have been selected. According to the obtained results, if the spray system is revived before 4000s from the beginning of the accident in any of the mentioned modes, this system would be able to control and mitigate the accident. Moreover, without the need for any external water supply source for spray system, this system can be permanently fed from containment sump for at least 800000s after the initiation of the accident, but the relevant heat exchanger of spray system must be recovered for this period
  9. Keywords:
  10. Spray System ; Thermohydrodynamic Simulator ; Large Break Less-of-Coolant Accident (LB-LOCA) ; Core Degradation ; MELCOR Code ; Mobile Equipments ; Bushehr Nuclear Power Plant

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