A novel layered boron-based neutron shield design and results from neutron and gamma irradiation studies

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2022-2-18

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Muçogllava, Brunilda

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Neutron radiation is a widely used tool in medical radiotherapy, non-destructive radiography, material structural studies, and more. However, the absence of electromagnetic charge allows neutrons to easily penetrate materials and skin, causing radioactivation, ionization and displacement damage. For each of the aforementioned applications, shielding against neutrons is of utmost importance. A novel, layered boron-based shield has been designed and tested for shielding in medical applications. The design integrates high-density polyethylene to scatter low-energy neutrons, borated minerals (colemanite, ulexite and boron oxide) to capture thermal neutrons, and bismuth oxide doped polyethylene to absorb secondary gamma rays. Different layer combinations and doping percentages by weight were simulated using FLUKA Monte Carlo simulation software and compared with a commercial neutron shield. Radiation attenuation tests were carried out using 4 MeV neutrons from a PuBe source at Istanbul Technical University and up to 5 MeV secondary neutrons from Middle East Technical University Defocusing Beamline (METU-DBL), which is an anisotropic source. To test the shield at METU-DBL, a neutron moderator and a collimator was designed to provide a neutron beam with a flux of 10^6 neutrons/cm^2/s, in a radius of 5 cm. A sample holding mechanism rotates six samples to the irradiation area in one radiation session, making the comparison of samples easier and significantly reducing unwanted radiation for material studies.

Subject Keywords

borated polyethylene, low energy neutron, neutron collimator, neutron test set-up, radiation protection, shielding, Monte Carlo method

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https://hdl.handle.net/11511/96683

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

B. Muçogllava, “A novel layered boron-based neutron shield design and results from neutron and gamma irradiation studies,” M.S. - Master of Science, Middle East Technical University, 2022.