Transport of Accelerator Produced Neutrons in a Concrete Room

The production of photoneutrons by electron accelerators is an unavoidable process at operating energies above about 10 MeV. These photoneutrons create problems in shielding, personnel protection, and induced radioactivity. This paper attempts to describe the neutron field spectral and intensity distributions. The initial spectrum and modifying effects of photon shielding materials and concrete room shielding are considered. The relative yields of neutrons and photons as a function of the primary electron energy are described. Both experimental and Monte Carlo results are presented. It is shown that the average energy of the neutron spectrum is a useful parameter for shielding calculations, fluence-to-dose equivalent conversions, and spectral degradation calculations.