Monte Carlo simulation of neutron transmission of boron-alloyed steel

For material characterization, it is of specific importance to define the homogeneity distribution of strong absorbing elements within shielding materials quantitatively. Boron is the important absorber used for the production of boron-alloyed steel to serve in long-term storage of spent nuclear fuel or nuclear waste disposals. Due to the high neutron absorption of boron compared to steel, the neutron radiography is a powerful tool for the nondestructive investigation. This paper concerns quantitative estimations of secondary effects on the neutron transmission measurements through thermal neutron shielding materials such as beam hardening, background, and inhomogeneous absorber distribution within the samples, which decrease the neutron attenuation in absorber materials. Neutron transmission measurements have been performed for boron-alloyed steel plates having different thickness using thermal neutrons. The investigated samples are from the Austrian Steel Production Company Böhler Bleche GmbH, which uses natural boron in the form of boron carbide within the steel matrix. The attenuation coefficients of boron-alloyed steels were measured with neutron radiography and the special neutron transmission set-up "JEN-3", which is used for routine test measurements of shielding materials by the Austrian Steel Production Company Böhler Bleche GmbH. In addition to the transmission measurements, Monte Carlo Neutron Particle (MCNP) simulations were performed for better understanding and interpretation of the obtained experimental results. This is the first step of our study covering the estimation of some secondary effects on the neutron transmission. Further experiments will be continued using different absorber materials and homogeneity distribution in order to verify afore said factors in the transmission experiments of neutron shielding materials.