MONTE-CARLO SIMULATION OF PROMPT GAMMA-NEUTRON-ACTIVATION ANALYSIS USING MCNP CODE

Prompt gamma neutron activation analysis (PGNAA) is the most direct me thod of measuring total-body nitrogen. In combination with internal hy drogen standardisation, it is possible to reduce the dependence on bod y habitus. The uniformity of activation and detection, however, cannot be optimised sufficiently to eliminate the dependence entirely, and s o further corrections are essential. The availability of the powerful Monte Carlo code MCNP(4A) has allowed a more accurate analysis of the activation facility, and yields corrections for body habitus and super ficial fat layers. The accuracy of the correction is retained as the s ource-to-skin distance is reduced, although the activation uniformity is thereby degraded. This allows the use of a Cf-252 source with lower activity and hence reduces the running cost of the facility. (C) 1998 Elsevier Science Ltd. All rights reserved.