Development of deterministic transport methods for low energy neutrons for shielding in space. Final report

Technical Report · Wed Sep 01 00:00:00 EDT 1993

OSTI ID:5928112

Ganapol, B

Transport of low energy neutrons associated with the galactic cosmic ray cascade is analyzed in this dissertation. A benchmark quality analytical algorithm is demonstrated for use with BRYNTRN, a computer program written by the High Energy Physics Division of NASA Langley Research Center, which is used to design and analyze shielding against the radiation created by the cascade. BRYNTRN uses numerical methods to solve the integral transport equations for baryons with the straight-ahead approximation, and numerical and empirical methods to generate the interaction probabilities. The straight-ahead approximation is adequate for charged particles, but not for neutrons. As NASA Langley improves BRYNTRN to include low energy neutrons, a benchmark quality solution is needed for comparison. The neutron transport algorithm demonstrated in this dissertation uses the closed-form Green's function solution to the galactic cosmic ray cascade transport equations to generate a source of neutrons. A basis function expansion for finite heterogeneous and semi-infinite homogeneous slabs with multiple energy groups and isotropic scattering is used to generate neutron fluxes resulting from the cascade. This method, called the FN method, is used to solve the neutral particle linear Boltzmann transport equation. As a demonstration of the algorithm coded in the programs MGSLAB and MGSEMI, neutron and ion fluxes are shown for a beam of fluorine ions at 1000 MeV per nucleon incident on semi-infinite and finite aluminum slabs. Also, to demonstrate that the shielding effectiveness against the radiation from the galactic cosmic ray cascade is not directly proportional to shield thickness, a graph of transmitted total neutron scalar flux versus slab thickness is shown. A simple model based on the nuclear liquid drop assumption is used to generate cross sections for the galactic cosmic ray cascade.

• Research Organization: Arizona Univ., Tucson, AZ (United States). Water Resources Research Center
• OSTI ID: 5928112
• Report Number(s): N-94-11199; NASA-CR-194172; NAS-1.26:194172; CNN: NAG1-1041
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
COSMIC SHOWERS
BIOLOGICAL SHIELDING
NEUTRONS
TRANSPORT THEORY
B CODES
BOLTZMANN EQUATION
CHARGED PARTICLES
COMPUTER CODES
COSMIC RADIATION
ENERGY TRANSFER
GREEN FUNCTION
INTEGRAL EQUATIONS
M CODES
RADIATION PROTECTION
BARYONS
DIFFERENTIAL EQUATIONS
ELEMENTARY PARTICLES
EQUATIONS
FERMIONS
FUNCTIONS
HADRONS
IONIZING RADIATIONS
NUCLEONS
PARTIAL DIFFERENTIAL EQUATIONS
RADIATIONS
SECONDARY COSMIC RADIATION
SHIELDING
SHOWERS
663610* - Neutron Physics- (1992-)
990200 - Mathematics & Computers