Borehole parametric study for neutron induced capture gamma-ray spectrometry using the MCNP code

The MCNP Monte Carlo code has been used to simulate neutron transport from an Am-Be source into a granite formation surrounding a borehole. The effect s of the moisture and the neutron poison on the thermal neutron flux distri bution and the capture by the absorbing elements has been calculated. Therm al and nonthermal captures for certain absorbers having resonance structure s in the epithermal and fast energy regions such as W and Si were performed . It is shown that for those absorbers having large resonances in the epith ermal regions when they are present in dry formation or when accompanied by neutron poisons the resonance captures may be significant compared to the thermal captures. (C) 2000 Elsevier Science Ltd. All rights reserved.