Monte Carlo calculation of epithermal neutron resonance self-shielding factors in foils of different materials

Epithermal neutron resonance self-shielding factors in foils of materials used as activation detectors or as targets for radionuclide production have been calculated using the MCNP code. Two irradiation conditions have been considered: (a) foils immersed into an isotropic neutron flux and (b) foils submitted to a collimated neutron beam. The self-shielding factors, G(res)(t), for gold. indium. manganese and cobalt have been compared with available published values. The self-shielding factor depends on various physical and nuclear parameters. However, it is shown that for the isotropic case and for high absorber elements submitted to a collimated beam. a dimensionless variable could be adopted that describes the self-shielding factors of different materials by quasi "universal curves". G(res)(t) for the collimated beam are always higher than those for the isotropic case. (C) 2002 Elsevier Science Ltd, All rights reserved.