NEUTRON THERMALIZATION CALCULATIONS FOR A HETEROGENEOUS LATTICE CONSISTING OF RODS OF URANIUM AND PLUTONIUM FUEL IN WATER. PROCEEDINGS OF THE NEUTRON THERMALIZATION CONFERENCE, APRIL 28-30, 1958, GATLINBURG, TENNESSEE

Technical Report · Sat Oct 31 04:00:00 EST 1959

OSTI ID:4205164

Greebler, P

Calculated temperature and steam void coeffieients of reactivity are highly sensitive to the techniques employed to obtain thermal cross sections, especially with the eresence of a strongly non-1/v absorber such as Pu/sup 239/ . Thermal neutron spectra are calculated for a heterogeneous lattice of a low enrichment boiling water 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 fiux 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 236/ 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 depanture from 1/v absorption. Sensitivity of the calculated spectrum to the effective mass of the hydrogen is tested by allowing wide variatioas of the xi of values for water at low energies in several applications of the Wilkins equation. Variations in the thermal-neutron spectra resulting from the choice of the thermalization equation, from changing xi sigma /sub s/, or as a result of plutonium buildup are evaluated in terms of isotopic and total cross sections averaged over the spectrum in each case. (auth)

• Research Organization: General Electric Co. Vallecitos Atomic Lab. , San Jose, Calif.
• NSA Number: NSA-13-020343
• OSTI ID: 4205164
• Report Number(s): ORNL-2739(Paper IV-A)
• Country of Publication: United States
• Language: English

Related Subjects

ABSORPTION
BLACKNESS THEORY
BOILING
CROSS SECTIONS
FUEL ELEMENTS
HYDROGEN
NEUTRONS
NUMERICALS
PHYSICS AND MATHEMATICS
PLUTONIUM
RADIATIONS
REACTIVITY
REACTORS
RODS
SLOWDOWN
STEAM
TEMPERATURE
THERMAL NEUTRONS
URANIUM
URANIUM 235
URANIUM 238
WATER MODERATOR
WIGNER-WILKINS MODEL