INVESTIGATIONS OF NEUTRON FIELDS USED IN ELEMENTAL ANALYSIS OF BULK SAMPLES

Flux density distributions of thermal and primary 14 MeV neutrons have been measured in different configurations of bulk samples consisting of graphite, water and coal. Analytical expressions are given for the calculations of the absolute flux values of neutrons in various modera tor-sample-reflector geometries. Attenuation characteristics of water, graphite and coal were determined for Cf-252, Pu-239-Be and 14 MeV ne utrons. Relative fractions of neutrons above the (n, n'gamma) reaction thresholds for Si-28, C-12 and O-16 isotopes vs sample thickness are also given. Total hydrogen contents have been determined by neutron re flection method for coals of different origin.