A New Approximation for the Neutron Albedo

Abstract

Empirical parameters for a new fast-neutron differential dose albedo formula are presented for water, concrete, iron, and lead and for ten energy bands between 0.1 and 10.0 MeV. Data are also presented for 252 Cf spontaneous fission neutrons, 14-MeV neutrons, and thermal neutrons. The 24parameter approximation, based on modern dose units, agrees with MCNP-calculated values within 10%. Revised data are also presented for a five-parameter secondary-photon albedo formula, proposed earlier by Maerker and Muckenthaler, that is within 20% of MCNP values for the four materials. Finally, these revised albedo formulas are applied to the problem of thermal neutrons transmitted through a three-legged duct and compared to previous experimental results.

Self-Shielding Copper Substrate Neutron Supermirror Guides

“…A final myth, and perhaps the most common, espouses the ignoring of the problem entirely, relying on the idea that the fast neutron background can be discriminated in time. The underlying physics is that of albedo reflections [23] and photonuclear processes (γ → n reactions) [24] by which fast neutrons are generated, and propagate down curved guides, when no protons are illuminating the spallation target. These two effects combine to create long tailed distributions that exponentially approach a flat asymptote between 10 −2 and 10 −4 relative to the prompt p + W → n peak, as seen in operational instruments at existing spallation sources [11,25].…”