Abstract: A modular assembly for a bulk material includes container modules defining at least one radiation source cavity, at least one radiation detector channel and a passageway disposed for enabling passage of the conveyor belt through an activation region; and radiation shielding material disposed within the container means. A lower primary module contains a first portion of the radiation shielding material and defines either the radiation source cavity or the radiation detector channel. An upper primary module contains a second portion of radiation shielding material and defines the other of either the radiation source cavity or the radiation detector channel. A set of replaceable side modules contain additional portions of the radiation shielding material.

Abstract: In a bulk material analyzer in which bulk material is received in an activation region between a pair of neutron sources laterally disposed on one side of the activation region for emitting neutrons for bombarding the bulk material within the activation region to cause gamma-rays to be emitted from the bombarded bulk material and a pair of gamma-ray detectors laterally disposed on an opposite side of the activation region for detecting gamma-rays emitted from the bulk material, and in which a neutron moderator is disposed between the neutron sources and the activation region for reducing the velocity of the emitted neutrons such that the neutrons entering the activation region include thermal neutrons and faster neutrons, the uniformity of sensitivity of the bulk material analyzer to materials at different positions in a sample of the bulk material being analyzed is enhanced by controlling the proportions of thermal neutron at different positions within the sample being analyzed.