08 Thermal neutron self-shielding factors

08 2003 Thermal neutron self-shielding factors in foils – A universal curve

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 parameters: the thermal neutron self-shielding factor, Gth, and the resonance neutron self-shielding factor, Gres. In recent works, the authors established an universal curve of Gres for isolated resonances and various geometries. The present paper deals with the description of Gth in foils by means of an universal curve on the basis of a dimensionless variable which includes the physical, nuclear and geometrical properties of the sample. The universal curve is in very good agreement with experimental and calculated values obtained from the literature. The study of other geometries (spheres, wires and cylinders) is in progress.

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