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Neutronic Simulation of Pebble Bed Reactors

Abedi, Amin | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42745 (46)
  4. University: Sharif University of Technology
  5. Department: Energy Engineering
  6. Advisor(s): Vossoughi, Nasser
  7. Abstract:
  8. The Very-High Temperature Reactor (VHTR) design is one of the six candidates for the Generation IV nuclear reactors. The reactor core type of the VHTR design is either prismatic or pebble-bed. In pebble bed reactors, the core is filled of thousands of graphite and fuel pebbles. Fuel pebbles in these reactors consist of TRISO particles, which are embedded in a graphite matrix stochastically. The reactor core is also stochastically filled up of fuel and dummy pebbles with an unequal ratio. These two stochastic geometries are the so-called double heterogeneous of this type of reactors. In the current study, a pebble bed reactor, HTR-10, considering the above mentioned stochastic phenomena is modeled using MCNP5 Monte Carlo code and MATLAB programing. First, 8335 TRISO particles using expanded FILL and LATTICE features of MCNP code and MATLAB generated random numbers are distributed randomly in a pebble and are considered as a UNIVERSE. To fill the core, both regular crystal and stochastic structures are used. In crystal structures, fuel and dummy pebbles are arranged stochastically in a regular structure, while in the stochastic structure, centers of pebbles are generated stochastically and uniformly and transferred into the MCNPinput file as centers of spherical surfaces. In the second model, there is no approximation of actual geometry. In other words, in addition to considering the above double heterogeneity nature, there are no truncated pebbles in the core and the fuel to moderator ratio, active core height and packing fraction are exactly identical with the real case. Finally, for validation of the recent model, the benchmark problems of IAEA are used. Very high compliance of our results with available experimental data is quite evident
  9. Keywords:
  10. Stochastic Geometry ; Pebble Bed Reactor ; Monte Carlo N-Particle (MCNP)Code ; Double Heterogeneity ; High Temperature Reactor-10 (HTR-10)

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