Calculations of anisotropy factors for radionuclide neutron sources due to scattering from source encapsulation and support structures

ESTIMATION OF THE ANISOTROPY EMISSION OF LPN/CIEMAT NEUTRON SOURCES: EFFECT OF HEAVY CAPSULE HOLDERS

In order to estimate the anisotropy emission of 241Am-Be and 252Cf neutron sources from the Spanish Neutron Standards Laboratory (LPN/CIEMAT) detailed models of sources capsules and capsule holders were designed with the MCNPX code. Simulations of the sources inside the capsules without the capsule holders were done to validate the MC model by comparison with experimental results provided by other authors. After that, the capsule holders were incorporated to the simulation. In general, a good agreement has been found between measurements and our calculations. Results show the additional encapsulations have significant influence on anisotropy factors, energy spectra and dose rates.

An attempt to decrease anisotropic emissions of neutrons from a cylindrical 241Am-Be-encapsulation source

An attempt to decrease the anisotropic emissions of neutrons from a cylindrical (241)Am-Be-encapsulated X3 source was conducted with Monte Carlo calculations and experiments. The influence of metal materials and shapes of the external casing to the anisotropy factor were focussed on. Results obtained by calculations using MCNP4C implied that a light and spherical-shaped external casing decreases the anisotropic emission of neutrons. Experimental results using the spherical-shaped aluminium protection case also revealed that the anisotropy factor was close to 1.0 with wide zenith angle ranges.