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Design and Construction of PE/W/LiF Composites as the Shield of Neutron-gamma in Mixed Fields

Mirazimi, Samaneh | 2015

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 46830 (46)
  4. University: Sharif University of Technology
  5. Department: Energy Engineering
  6. Advisor(s): Vossoughi, Nasser; Asadi, Skandar
  7. Abstract:
  8. In a nuclear reaction, particles such as gamma, neutron, alpha beta, etc. May be emitted. Environment and humans could be damaged severely if these radiations are not properly shielded. One of the main goals of this project is manufacture proper shields for neutron and gamma attenuation and absorption in mixed fields, benefiting the particular properties of composites. In preliminary stage of this project, with comprehensive studies, primary materials were selected. These materials are Tungsten, Polyethylene and Lithium Fluoride selected as Gamma absorber, thermalizer and thermalized neutron absorber respectively. In the next step, weight fractions of each material and thicknesses of composite layers required to shield a 1Ci Am-Be source were calculated using MCNP code. According to the simulation results, a two layer shield was registered. The first layer comprised of PE/LiF with weight fractions equal to 77.5% and 22.5% respectively and thickness of 16 cm. Second layer was made of 60% tungsten and 40% polyethylene with a total thickness of 5 cm. These values were calculated regarding that the distance between source and detector is equal to 80 cm. The more the distance between the detector and the source, the less shield thickness is needed. In the end, shields with sizes of 16×9×1 cm^3 were made and nuclear characterizations were performed for neutron shields and gamma shields with Am-Be source and BF3 detector and 100 mCi 137Cs source and NaI(Tl) detector respectively. There was a good agreement between simulation results and experiments
  9. Keywords:
  10. Composite ; Neutron Shielding ; Gamma Shielding ; Composite Shields

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