Bulk media assay using backscattered Pu–Be neutrons

Spectral yields of elastically backscattered Pu–Be neutrons measured for graphite, water, polyethylene, liquid nitrogen, paraffin oil, SiO2, Al, Fe, and Pb slabs show a definite correlation with the energy dependence of the elastic scattering cross sections, σEL(En). The C, N and O can be identified by the different structures in their σEL(En) functions. The integrated spectral yields versus thickness exhibit saturation for each sample. The interrogated volume is limited by the presence of hydrogen in the sample.