Correlation between boron content and thermal neutron attenuation coefficient in borated stainless steels analyzed by neutron diffraction

The relationship between boron content and thermal neutron attenuation coefficient was examined in fifteen kinds of borated stainless steels alloyed with the weight percentage of 0.19–1.87 boron. The attenuation coefficients were measured by the ratio of the neutron intensity transmitted by the borated stainless steel to the initial intensity without transmission. The neutron intensity was analyzed by the diffraction peak with the wavelengths of 0.131, 0.146, and 0.1836 nm. The result shows that the attenuation coefficient of 1.491 cm⁻¹ increases up to 5.412 cm⁻¹, which means a significant decrease of the peak intensity, as the boron content increases from 0.19 wt% to 1.87 wt% in the borated stainless steels. It is attributed to the high areal density (g/cm²) of ¹⁰B isotope in the natural boron, which has a large neutron microscopic cross-section. The measured attenuation coefficients are comparable to the theoretically calculated ones based on the microscopic cross-sections of contained elements in each alloy. Besides, it is proportional to the neutron wavelength due to the decrease of the neutron energy. This paper provides the correlation among the boron content, specimen thickness, and transmission ratio of thermal neutrons at wavelengths in the borated stainless steels.