High-altitude neutral-particle transport using the Monte Carlo simulation code MCNP with variable density atmosphere. Master's thesis
Technical Report
·
OSTI ID:6134349
The Monte Carlo transport code, MCNP was modified for purposes of two dimensional neutron-photon transport modelling in a variable density atmosphere. Calculations were performed using cylindrical (r, z) geometry and a point isotropic neutron-photon source at an elevation of 40 kilometers. Neutron and photon fluence results were computed using ring detectors for field points at constant range versus source elevation angle and for field points at constant altitude versus radius. Comparisons between the modified and unmodified versions of MCNP showed a decrease in run time by a factor of two was possible. Only a fraction of the spatial cells previously required were used. Results showed streaming of the neutron and photon radiation at very close ranges. Buildup from multiple scattering contributions proved to be the dominant effect at intermediate ranges. Attenuation from successive downscatter in energy was shown to be the dominant effect at ranges greater than about 60 kilometers. Results obtained with MCNP were compared to those obtained with the computer code SMAUG-II, which uses the mass-integral scaling approximation. The comparison showed SMAUG-II to be accurate at points close to the source, but serious errors were encountered at ranges exceeding 9 kilometers as the mass range increased.
- Research Organization:
- Air Force Inst. of Tech., Wright-Patterson AFB, OH (United States). School of Engineering
- OSTI ID:
- 6134349
- Report Number(s):
- AD-A-238738/9/XAB
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
663610* -- Neutron Physics-- (1992-)
663620 -- Physics of Radiations Other Than Neutrons-- (1992-)
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ALTITUDE
ATTENUATION
BARYONS
BOSONS
COMPUTER CODES
DENSITY
DISTANCE
DISTRIBUTION
EARTH ATMOSPHERE
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
FERMIONS
HADRONS
M CODES
MASS
MASSLESS PARTICLES
MATHEMATICAL MODELS
MONTE CARLO METHOD
NEUTRAL-PARTICLE TRANSPORT
NEUTRON FLUENCE
NEUTRON TRANSPORT
NEUTRONS
NUCLEONS
PHOTON TRANSPORT
PHOTONS
PHYSICAL PROPERTIES
RADIATION TRANSPORT
RADIATIONS
RINGS
S CODES
SCATTERING
SPATIAL DISTRIBUTION
663620 -- Physics of Radiations Other Than Neutrons-- (1992-)
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ALTITUDE
ATTENUATION
BARYONS
BOSONS
COMPUTER CODES
DENSITY
DISTANCE
DISTRIBUTION
EARTH ATMOSPHERE
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
FERMIONS
HADRONS
M CODES
MASS
MASSLESS PARTICLES
MATHEMATICAL MODELS
MONTE CARLO METHOD
NEUTRAL-PARTICLE TRANSPORT
NEUTRON FLUENCE
NEUTRON TRANSPORT
NEUTRONS
NUCLEONS
PHOTON TRANSPORT
PHOTONS
PHYSICAL PROPERTIES
RADIATION TRANSPORT
RADIATIONS
RINGS
S CODES
SCATTERING
SPATIAL DISTRIBUTION