Neutron field characteristics of Ciemat's Neutron Standards Laboratory.

Abstract Monte Carlo calculations were carried out to characterize the neutron field produced by the calibration neutron sources of the Neutron Standards Laboratory at the Research Center for Energy, Environment, and Technology (CIEMAT) in Spain. For 241 AmBe and 252 Cf neutron sources, the neutron spectra, the ambient dose equivalent rates and the total neutron fluence rates were estimated. In the calibration hall, there are several items that modify the neutron field. To evaluate their effects different cases were used, from point-like source in vacuum up to the full model. Additionally, using the full model, the neutron spectra were estimated to different distances along the bench; with these spectra, the total neutron fluence and the ambient dose equivalent rates were calculated. The hall walls induce the largest changes in the neutron spectra and the respective integral quantities. The free-field neutron spectrum is modified due the room return effect.