Use of thermal neutron reflection method for chemical analysis of bulk samples

Microscopic, σβ, and macroscopic, Σβ, reflection cross-sections of thermal neutrons averaged over bulk samples as a function of thickness (z) are given. The σβ values are additive even for bulk samples in the z=0.5–8 cm interval and so the σβmol(z) function could be given for hydrogenous substances, including some illicit drugs, explosives and hiding materials of ~1000 cm3 dimensions. The calculated excess counts agree with the measured R(z) values. For the identification of concealed objects and chemical analysis of bulky samples, different neutron methods need to be used simultaneously.