Serpent 2 Validation for Radiation Shielding Applications

This paper provides a contribution to the validation of photon transport and coupled neutron-photon transport routines in Serpent 2. The validation is performed by calculating two benchmarks ALARM-CF-FE-SHIELD-001 and ALARM-CF-PB-SHIELD-001. In the benchmarks neutrons and photons originating from a Cf-252 source are transported through different
sized iron and lead spheres and the neutron and photon flux is tallied over a surface at a distance of 3R from the centre of the sphere, where R is the sphere radius. Three lead spheres with radius 10, 20 and 30 cm and six iron spheres with radius 10, 15, 20, 25, 30 and 35 cm were calculated with Serpent 2 and MCNP6.2. The Serpent results were compared to MCNP6.2 and measurement results. In all cases the Serpent calculated neutron and photon spectra followed
the measured spectra fairly well. For the iron spheres, differences between Serpent and MCNP6.2 calculated neutron spectra were mostly below 2 % at neutron energies below 4 MeV. Differences between photon spectra through the iron spheres was mostly below 3 %. For the lead spheres, differences in the calculated neutron spectra were mostly below 1.5 % in the energy range 0.04-4.0 MeV. Differences between photon spectra through the 10 cm lead sphere
was mostly below 5 % and for the larger spheres below 10 % except at higher photon energies above 6.5 MeV.