Non-destructive 10B analysis in neutron transmission experiments

Boron alloyed stainless-steel sheets are predominantly used in nuclear engineering as neutron shielding for radioactive waste disposal equipment. The neutron absorption depends strongly on the amount and the distribution of the 10B isotope. A systematic transmission study of 10B enriched steel plates by means of neutron time-of-flight and neutron radiography experiments was performed. The 10B content was analyzed with accuracy up to 5×10−3 wt% using monochromatic beams and a linear increase of the macroscopic cross section with the 10B content was found even for strong absorbers. Then we extended the transmission analysis to “white” thermal neutron beams where large deviations from the exponential transmission law are observed. The influence of the spectral width is discussed in more detail because beam hardening causes an elevation of the effective transmission through strong absorbing materials, an effect which is crucial for the design of neutron shielding.