Year
2009
Abstract
Cadmium is increasingly difficult to use in safeguards applications because of rising cost and increased health and safety regulations. This work examines the properties of two materials produces by Ceradyne, Inc. [1] that present alternatives to cadmium for neutron shielding. The first is aluminum boron allow and the second is boron carbide power, compressed into a ceramic. Both are enriched in the 10B isotope. Two sheets of aluminum boron allow (1.1mm and 5.2mm thick) and one sheet of boron carbide (8.5mm thick) wer provided by Ceradyne for evaluation. An experiment was designed to test the neutron-absorption capabilities of thses three sheets against atwo different thicknesses of cadmium (.6mm and 1.6mm). The thinner sheet of aluminum boron alloy performed as well as the cadmium sheets at absorbing neutrons. The thicker alminum boron plate provided more shielding than the cadmium sheets and the boron carbide performed best by a relativly large margin. Monte Carlo N-Particle eXtended (MCNPX) [2] transport code modeling of the experiment was performed to provide validated computational tools for predicting the behavior of systems in which these materials may be incorporated as alternatives to cadmium. MCNPX calculations predict that approzimately 0.17 mm thickness of the boron carbide is equivalent to .6 mm thickness of cadmium. Notably, they are not malleable, requiring machining to fit any curved forms and the aluminum boron alloy nees to be thicker than cadmium to provide the same neutron absorbing capabilities.