Nuclear Instruments and Methods

The presence of a sample in the neutron field of a nuclear reactor creates a perturbation of the local neutron fluxes. In general, the interpretation of the sample activation due to thermal and epithermal neutrons requires the knowledge of two corrective parameters: the thermal neutron self-shielding factor, Gth, and the resonance neutron self-shielding factor, Gres. Thermal neutron self-shielding factors in different materials (Al, Au, Cd, Co, Cu, Eu, Gd, In, Ir, Mo, Ni, Pt, Pb, Rh, Sc, Sm and Ta) and different geometries (foils, wires, spheres and) have been calculated by using the MCNP code.