EXPERIMENTAL EVALUATION OF NEUTRON SHIELDING MATERIALS
A new proposed design of neutron shielding material-based on the commercial material Borotron UH050 with an addition of Al(OH)3-is evaluated in order to determine if its neutron and gamma shielding properties match those of a reference material, NS4FR. Neutron and gamma dosimetry measurements are performed, as well as neutron spectrometry measurements and Monte Carlo simulations. Negligible differences are found between the materials for neutron shielding, while significant differences are found for gamma shielding. The effect of Al(OH)3 addition to Borotron UH050 is to reduce neutron shielding properties while increasing gamma shielding properties. The resulting material is as efficient as NS4FR for neutron shielding but less efficient for gamma shielding-thicknesses 20% higher are required to match gamma shielding properties of NS4FR. Monte Carlo models of the materials are validated based on the performed measurements of neutron spectra and neutron and gamma ambient dose equivalent.
The potential use of boron containing resources for protection against nuclear radiation
Abstract Recognizing the large neutron capture cross section of boron, the suitability of boron containing resources are studied for protection against nuclear radiation. Experimental and simulation study for neutron (thermal and fast) and gamma-ray shielding features of six different types of boron containing natural materials, obtained from the utilization process of boron ores in Liaoning Province of China, are performed here. Shielding ability of B1-B6 for thermal neutron is mainly based on the on the absorption cross section of boron; The elements with higher content or cross section have higher contribution for the fast neutron shielding; The interactions of B1-B6 with gamma rays are different with each other because of the difference components, but the mainly are Photoelectric Absorption in the low energy region, Incoherent Scattering in the intermediate energy region and Pair Production in nuclear filed in the high energy region, the elements with higher content or high atomic number show higher contribution for the shielding performance. The neutron and gamma ray shielding show a positive correlation with the boron content and material density, respectively. Comprehensive shielding performance of the studied samples is found to be better than some commercial materials. Overall, the composites prepared by boron containing resources and epoxy resin show excellent shielding performances for neutron but poor for gamma rays. Particularly, the boron rich slag shows the greater performance for both neutron and gamma ray shielding. The obtained results show the pathway for potential use of boron containing resources as structural materials in the radiation environment, and provide protection to both radiation worker and general populace from harmful nuclear radiation.
Unidirectional hexagonal rare-earth disilicide nanowires on vicinal Si(100)-2×1
Rare-earth disilicide nanowires grown on vicinal Si(100) with a miscut of 2–2.5° toward the [110] azimuth at 600 °C were studied by scanning tunneling microscopy and compared with those grown on flat Si(001). In contrast to rare-earth disilicide nanowires grown on flat Si(100) surfaces, the nanowires grow unidirectionally along the [01̄1] direction of the vicinal Si(100) surface. Rare-earth disilicide nanowires form bundles composed of single nanowire units on both flat and vicinal surfaces. Yet, on the vicinal surface, the bundle width is comparable to the width of the terrace. The average nanowire length on the vicinal substrate is longer than that on the flat substrate. Scanning tunneling spectroscopy shows that the rare-earth disilicide nanowires have metallic properties.