Radiation shielding calculations by means of MCNPX
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Date
2006
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Abstract
Monte Carlo radiation transport calculations were performed to re-evaluate the configuration of the horizontal target bombardment station of the ra-dionuclide production at iThemba LABS. Calculated neutron and photon dose attenuation factors for this shield were compared with those previously obtained by means of the multigroup discrete ordinate code. Isotropic and anisotropic source terms were assumed. Furthermore, two geometries were considered, namely, spherical and cylindrical
The neutron and photon total dose rates and dose attenuation factors were calculated at 1.5 m from the center of the target for a shield config¬uration composed of a combination of homogeneous materials such as iron, paraffin wax containing boron carbide for the attenuation of neutrons, and lastly, lead as an outer photon shield layer. The thickness of lead necessary to attenuate photons transmitted from the neutron capture reactions and those from the decay of the residual nuclei was about 4 cm. The amount of boron carbide needed to mix with paraffin wax was determined by adding. by weight percent, small increments of boron carbide into paraffin wax until about 10% of the boron carbide was eventually added into the wax. The thickness of iron and wax needed to attenuate fast neutrons to thermal neu¬trons was determined by fixing the total thickness of the shield 60 cm and the position of iron, with respect to iron/wax interface was determined by mov¬ing iron across the shield configuration. Where available, the results obtained by means of MCXPX were compared with those previously published.
Description
A thesis submitted in partial fulfilment of the requirements
for the degree of Master of Science
in the Department of Physics and Engineering,
University of Zululand, 2006.
Keywords
Radiation shielding