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Experimental Study of LOFA, LOHA and Natural Circulation Performance of the TTL-2 Thermal Hydraulic Test Loop and Modeling With RELAP5 System Code

Arabnezhad, Hadi | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40418 (46)
  4. University: Sharif University of Technology
  5. Department: Energy Engineering
  6. Advisor(s): Ghofrani, Mohammad Bagher; Jafari, Jalil
  7. Abstract:
  8. In this survey the TTL-1 thermal hydraulic test loop in Nuclear Science and Technology Research Institute (NSTRI) has been modified to study thermal hydraulic phenomenon in research reactor thermal condition. These modifications include: replacing the test section containing a single heating rod by a group of 31 rods in a triangular array, relocating the pressurizer from the cold leg to the hot leg and improving piping of the test loop. In order to measure the time dependant flowrate of the coolant, a rotameter flowmeter is added. Three level meter measure the water level in pressurizer, test section and the primary loop drain tank and a 3-phase AC inverter controls the rotational speed of the circulation pump. By implementing the frequency inverter, a wide range of mass flowrate could be obtained in steady state condition and simulation of the pump coast-down with flywheel in a nuclear plant is possible. With above modifications, experimental study of the LOFA, LOHS and natural circulation performance of the thermal hydraulic loop, development and validation of the nuclear codes by the experimental data is feasible. The new test facility named TTL-2 is simulated by the RELAP5/MOD3.2 and the code is verified in steady state and transient condition by the experimental data of the loop. This code is provided by the IDAHO laboratory as a request of the U.S. regulatory body to simulate the power reactors. So it could not be applied for research reactors unless with care and precise investigation. By comparing the experimental data and the code results it has been shown that this code could estimate the natural circulation performance and the behavior of the thermal hydraulic loops in steady state and transient condition in loss of flow accident and loss of heat sink accident appropriately. By analyzing the test loop in loss of flow accident condition, it is concluded that the natural circulation flow is sufficient to remove the residual decay heat and the heat produced in the test section in loss of heat sink condition could be accumulated on the coolant thermal capacity safely.

  9. Keywords:
  10. Thermohydraulics ; Natural Circulation Phenomenon ; RELAP5 Code ; Thermohydraulic Test Loop-2 ; Small Break Less-of-Coolant-Accident (SB-LOCA) ; Loss of Heat Sink (LOHS)

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