A Monte Carlo study of the influence of the geometry arrangements and structural materials on a PGNAA system performance for cement raw material analysis

The MCNP-4A code, running on a Pentium PC, was used to simulate a conveyor belt system for on-line cement raw material analysis, namely the determination of calcium, silicon, iron and aluminium contents. The influence of different system and sample parameters (overall system geometry, neutron moderator/reflector composition and thickness, neutron absorber lining of detector shields, sample bulk density and water content) on the background count rate originating from structural materials was studied. A configuration has been obtained which corresponds to a lower background due to structural materials and a relative higher contribution from γ-rays produced in (n, γ) reactions in the bulk raw material. In this configuration, the dependence of the count rate on the sample density and water content is different in the lower and upper detectors. In the upper detectors, the count rate from inelastic reactions in lead surrounding the neutron source is shown to decrease exponentially with increasing density values, thus enabling density measurements to be made.