Reactor Physics Progress Report: May, 1955 - December, 1956
- North American Aviation, Inc., Canoga Park, CA (United States). Atomics International Div.
The disadvantage factors have been measured for one-inch-diameter thorium rods inserted in a lattice of one-inch-diameter 0.9-per cent enriched uranium rods in graphite. Similar measurements were made for rods of thorium alloyed to 2, 3, and 4 per cent with uranium-235. The elementary "age" theory of the slowing down of neutrons has been improved by estimating the energy at which slowing-down ceases and at which the neutron may be considered to make the transition to a thermal distribution. This has been accomplished by means of a comparison with slowing-down theories which take into account the thermal motion of the moderator. The comparison must be made with respect to a single parameter; this may be either the migration area of thermal neutrons, the migration area to absorption, or the mean number of collisions before absorption. A straightforward comparison theory used at first differed from the elementary theory only in that the mean energy loss was made proportional to E-2kT, rather than to E; later, however, the Wilkins theory of slowing-down was applied. Using this theory, and basing the comparison on the mean number of collisions before absorption, the transition energy was found to be five times thermal.
- 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-11-008174
- OSTI ID:
- 4373565
- Report Number(s):
- NAA-SR--1864
- 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
ABSORPTION-- CAPTURE-- COLLISIONS-- DIFFERENTIAL EQUATIONS-- DISTRIBUTION-- FERMI AGE-- FUEL ELEMENTS-- GRAPHITE MODERATOR-- LIFETIME-- MEASURED VALUES-- MODERATORS-- MOTION-- NEUTRON FLUX-- REACTOR CORE-- REACTORS-- RODS-- SLOWDOWN-- THORIUM-- THORIUM ALLOYS-- URANIUM ALLOYS
COMPUTERS- - ENERGY-- NUMERICALS-- QUANTUM MECHANICS-- RESONANCE-- RESONANCE ESCAPE PROBABILITY-- RESONANCE NEUTRONS-- THERMAL NEUTRONS-- WILKINS EQUATION-- WKB APPROXIMATION
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ABSORPTION-- CAPTURE-- COLLISIONS-- DIFFERENTIAL EQUATIONS-- DISTRIBUTION-- FERMI AGE-- FUEL ELEMENTS-- GRAPHITE MODERATOR-- LIFETIME-- MEASURED VALUES-- MODERATORS-- MOTION-- NEUTRON FLUX-- REACTOR CORE-- REACTORS-- RODS-- SLOWDOWN-- THORIUM-- THORIUM ALLOYS-- URANIUM ALLOYS
COMPUTERS- - ENERGY-- NUMERICALS-- QUANTUM MECHANICS-- RESONANCE-- RESONANCE ESCAPE PROBABILITY-- RESONANCE NEUTRONS-- THERMAL NEUTRONS-- WILKINS EQUATION-- WKB APPROXIMATION