Reactor Physics Quarterly Progress Report for January-March 1957
- North American Aviation, Inc., Canoga Park, CA (United States). Atomics International Div.
A series of exponential experiments with one-inch diameter uranium rods in diphenyl has been started. Initial measurements have been made to determine the height of thermal column and amount of external shielding needed. Fuel enrichments of 0.5, 0.7, and 0.9 per cent U235 will be used with one-inch diameter rods at lattice spacings varying from 1.5 to 2.5 inches. New techniques for making flux distribution measurements are being developed in order to overcome the problems which have arisen because of the use of diphenyl as a moderating material for the experiments. By application of the age-diffusion theory approximation, the non-leakage probability of neutrons from a spherical medium containing a centrally-located fast source is shown, for large sphere radius, to be proportional to exp (-π2M2/3R2), where R is the radius of the sphere and M2 the migration area of the neutrons in the medium. This functional dependence was verified by experimental measurement of the non-leakage probabilities of neutrons from fast sources contained in spheres of water, titanium hydride, and calcium hydride. For a mock-fission source, analysis of the data leads to values of 43 ± 2, 24 ± 2, and 100 ± 10 cm2 for the migration areas in these materials, respectively. An effort was made to relax two approximations upon which the Wilkins equation rests. The one condition, i.e., no chemical binding, has been relaxed in an approximate way involving the use of a judiciously chosen three-parameter approximation for the center-of-mass scattering cross section, which was introduced by Brown and St. John. A differential equation analogous to the Wilkins equation but involving this approximation was obtained and is now being coded for IBM 704 solution. An attempt was made to relax the second condition, i.e., heavy moderator mass, and it became clear that more refined approximations to the Wigner-Wilkins kernel would not lead to further simplification.
- Research Organization:
- North American Aviation, Inc., Canoga Park, CA (United States). Atomics International Div.
- Sponsoring Organization:
- US Atomic Energy Commission (AEC)
- DOE Contract Number:
- AT(11-1)-GEN-8
- NSA Number:
- NSA-12-000457
- OSTI ID:
- 4331611
- Report Number(s):
- NAA-SR--1974
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
22 GENERAL STUDIES OF NUCLEAR REACTORS
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
BINDING ENERGY-- COMPUTERS-- CROSS SECTIONS-- DIFFERENTIAL EQUATIONS-- EQUATIONS-- HYDROGEN-- MASS-- MODERATORS-- NEUTRONS-- NUMERICALS-- PROGRAMMING-- REACTORS-- SCATTERING-- SLOWDOWN-- WIGNER-WILKINS MODEL-- WILKINS EQUATION
DIPHENYLS-- DISTRIBUTION-- ENRICHMENT-- FUELS-- LATTICES-- MEASURED VALUES-- MODERATORS-- NEUTRON FLUX-- ORGANIC COMPOUNDS-- ORGANIC MODERATOR-- PHENYL RADICALS-- REACTORS-- RODS-- SHIELDING-- THERMAL COLUMN-- URANIUM-- URANIUM 235
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
BINDING ENERGY-- COMPUTERS-- CROSS SECTIONS-- DIFFERENTIAL EQUATIONS-- EQUATIONS-- HYDROGEN-- MASS-- MODERATORS-- NEUTRONS-- NUMERICALS-- PROGRAMMING-- REACTORS-- SCATTERING-- SLOWDOWN-- WIGNER-WILKINS MODEL-- WILKINS EQUATION
DIPHENYLS-- DISTRIBUTION-- ENRICHMENT-- FUELS-- LATTICES-- MEASURED VALUES-- MODERATORS-- NEUTRON FLUX-- ORGANIC COMPOUNDS-- ORGANIC MODERATOR-- PHENYL RADICALS-- REACTORS-- RODS-- SHIELDING-- THERMAL COLUMN-- URANIUM-- URANIUM 235