Neutron Thermalization Calculations for a Heterogeneous Lattice Containing Uranium and Plutonium Fuel in Water
Journal Article
·
· Nuclear Science and Engineering
OSTI ID:4221252
- General Electric Co., San Jose, CA (United States)
In a low-enrichment reactor at sufficiently high temperature that the P239 absorption cross section departs appreciably from 1/v. plutonium build- up increases the sensitivity of the calculated thermal cross sections to the thermalization techniques used. Thermal neutron spectra are compared for two thermalization models in a heterogeneous lattice of a low-enrichment 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 U235 and U238 yielding almost pure l/v absorption and also for the case of appreciable Pu239 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 sigmas 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 (Wigner-Wilkins or Wilkins), from changing xi sigmas, or as a result of plutonium build-up, are evaluated in terms of isotopic cross sections averaged over the spectrum in each case.
- Research Organization:
- General Electric Co., San Jose, CA (United States)
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA), Nuclear Criticality Safety Program (NCSP); US Atomic Energy Commission (AEC)
- NSA Number:
- NSA-13-019702
- OSTI ID:
- 4221252
- Journal Information:
- Nuclear Science and Engineering, Journal Name: Nuclear Science and Engineering Vol. 6; ISSN 0029-5639
- Publisher:
- Taylor & Francis
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
22 GENERAL STUDIES OF NUCLEAR REACTORS
BREEDING-- HYDROGEN-- NEUTRONS-- NUMERICALS-- PLUTONIUM 239-- REACTORS-- SLOWDOWN-- URANIUM-- WATER MODERATOR-- WIGNER-WILKINS MODEL-- WILKINS EQUATION
DISTRIBUTION-- ENERGY-- HYDROGEN-- NEUTRONS-- NUMERICALS-- REACTORS-- SENSITIVITY-- SLOWDOWN-- THERMAL NEUTRONS-- URANIUM-- WATER MODERATOR-- WIGNER-WILKINS MODEL-- WILKINS EQUATION
Nuclear Criticality Safety Program (NCSP)
BREEDING-- HYDROGEN-- NEUTRONS-- NUMERICALS-- PLUTONIUM 239-- REACTORS-- SLOWDOWN-- URANIUM-- WATER MODERATOR-- WIGNER-WILKINS MODEL-- WILKINS EQUATION
DISTRIBUTION-- ENERGY-- HYDROGEN-- NEUTRONS-- NUMERICALS-- REACTORS-- SENSITIVITY-- SLOWDOWN-- THERMAL NEUTRONS-- URANIUM-- WATER MODERATOR-- WIGNER-WILKINS MODEL-- WILKINS EQUATION
Nuclear Criticality Safety Program (NCSP)