Abstract:
Utilization of neutron sources requires careful safety precaution because neutrons have no electric charge and have high penetrating power. Therefore, the use of neutron shielding material is one of the methods to effectively prevent neutron radiation hazard. In this research work, neutron shielding materials were designed using the Monte Carlo N-Particle (MCNP) code in order to select proper materials and dimensions for neutron shielding. Thicknesses of 1 cm and 10 cm were chosen for shielding thermal neutron (10-8 - 10-2 MeV) and neutron in the entire energy spectrum (10-8 - 100 MeV), respectively. Simulation results indicated that the best shielding material for thermal neutron composed of natural rubber (NR) and SBR rubber blend in the 1:1 ratio with 60 part per hundred rubber (phr) diboron trioxide (B2O3), which can reduce the neutron dose from the Am-Be source by 53.91% with the total macroscopic cross section of 0.076 cm-1. For shielding neutron in the entire energy spectrum, the best shielding material was four alternating layers of NR with 100 phr iron (III) oxide (Fe2O3) and of NR and SBR blend in the 1:1 ratio with 10 phr diboron trioxide (B2O3), each layer having 2.5 cm in thickness. This shielding material can reduce the neutron dose by 72.56%. Addition of 1 mm cadmium sheets on the front and back sides offered the most additional neutron shielding performance. Comparison of the cubical, cylindrical and spherical shapes of the neutron shielding material with the same volume revealed that the spherical shape offered the best shielding performance for neutron in the entire energy spectrum. The optimal neutron shielding materials were fabricated and neutron radiography was performed to determine the homogeneity of the absorbing and scattering materials added to the rubber matrix. Result revealed good homogeneity throughout the shielding materials. Assessment of the produced secondary gamma ray by Prompt Gamma Neutron Activation Analysis (PGNAA) revealed a low-dose 478 keV gamma ray. Therefore, the designed shielding material can be utilized to effectively shield against neutrons.
