Coupled neutron transport for HZETRN

Authors

T.C. Slaba, Old Dominion University, NorfolkFollow
S.R. Blattnig, NASA Langley Research Center
S.K. Aghara, Prairie View A&M University
L.W. Townsend, University of Tennessee
T. Handler, University of Tennessee
T.A. Gabriel, Scientific Investigation and Development
L.S. Pinsky, University of Houston
B. Reddell, University of Houston

Date of this Version

2010

Citation

Radiation Measurements 45 (2010) 173–182; doi:10.1016/j.radmeas.2010.01.005

Abstract

Exposure estimates inside space vehicles, surface habitats, and high altitude aircrafts exposed to space radiation are highly influenced by secondary neutron production. The deterministic transport code HZETRN has been identified as a reliable and efficient tool for such studies, but improvements to the underlying transport models and numerical methods are still necessary. In this paper, the forward– backward (FB) and directionally coupled forward–backward (DC) neutron transport models are derived, numerical methods for the FB model are reviewed, and a computationally efficient numerical solution is presented for the DC model. Both models are compared to the Monte Carlo codes HETC-HEDS, FLUKA, and MCNPX, and the DC model is shown to agree closely with the Monte Carlo results. Finally, it is found in the development of either model that the decoupling of low energy neutrons from the light ion transport procedure adversely affects low energy light ion fluence spectra and exposure quantities. A first order correction is presented to resolve the problem, and it is shown to be both accurate and efficient.