NEUTRON THERMALIZATION CALCULATIONS FOR A HETEROGENEOUS LATTICE CONTAINING URANIUM AND PLUTONIUM FUEL IN WATER

Technical Report · Mon Apr 14 04:00:00 EST 1958

OSTI ID:4274053

Greebler, P; Harker, W H; Harriman, J M

Plutonium buildup in a low enrichment reactor at sufficiently high temperature that the Pu/sup 239/ absorption cross section departs appreciably from 1/v increases the sensitivity of the calculated thermal cross sections to the thermalization techniques used. Thermal neutron spectra are calculated for a heterogeneous lattice of a low enrichrnent water-moderated reactor. Using blackness theory, equivalent homogeneous, monoenergetic cross sections for the lattice are computed at closely spaced energy intervals over the thermal energy range. The energy distribution of the thermal neutron flux is then obtained using both the Wigner-Wilkins and the Wilkins thermalization equations. Calculations are made with the fuel elements assumed to contain only U/sup 235/ and U/sup 238/ yielding almost pure 1/v absorption, and also for the case of appreciable Pu/sup 239/ present in addition to the uranium, resulting in a significant departure from 1/v absorption. Sensitivity of the calculated spectrum to the effective mass of the hydrogen is tested by allowing wide variations of the xi sigma /sub 5/ values for water at low energies in several applicatioas of the Wilkins equation. Variations in the thermal neutron spectra resulting from the choice of the thermalization equation, from changing xi sigma /sub 5/, or as a result of plutonium buildup are evaluated in terms of isotopic cross sections averaged over the spectrum in each case. (auth)

• Research Organization: General Electric Co. Vallecitos Atomic Lab., Pleasanton, Calif.
• NSA Number: NSA-13-005920
• OSTI ID: 4274053
• Report Number(s): VAL-67; GEAP-3001
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

ABSORPTION
CONFIGURATION
CONVERSION
CROSS SECTIONS
DISTRIBUTION
EFFICIENCY
ENERGY
ENERGY RANGE
ENRICHMENT
EQUATIONS
ERRORS
FAST NEUTRONS
FUEL ELEMENTS
FUELS
HIGH TEMPERATURE
HYDROGEN
INTERACTIONS
ISOTOPES
MASS
MATHEMATICS
NEUTRON FLUX
NEUTRONS
NUMERICALS
PLUTONIUM
PLUTONIUM 239
PRODUCTION
REACTOR CORE
REACTORS
RESONANCE ESCAPE PROBABILITY
SLOWDOWN
SPECTRA
STANDARDS
THERMAL NEUTRONS
THERMAL UTILIZATION
TRANSPORT THEORY
URANIUM
URANIUM 235
URANIUM 238
WATER
WATER MODERATOR
WIGNER-WILKINS MODEL
ZONES