Measurement of the Doppler effect in uranium-238. [24 and 144 keV, 38 to 1100 K]
- EG and G Idaho, Inc., Idaho Falls
The Doppler effect of /sup 238/U metal and /sup 238/U in U/sub 3/O/sub 8/ was studied by using beams of filtered neutrons at 24 +- 0.9 keV and 144 +- 12 keV from the University of Missouri Research Reactor (MURR) Facility. The Doppler effect is the broadening of the widths of the nuclear resonances in the total cross section due to the thermal motion of the nuclei. The effective average total cross sections (EATCS) for both kinds of samples were measured with good geometry transmission measurements as functions of sample thickness and temperature to show the Doppler effect. The temperature of the samples ranged from 38 to 1100 K. Temperature-related density effects were removed by simultaneously measuring the attenuation of gamma rays passing through the samples. The EATCS data as function of sample thickness at room temperature were fit with a nuclear cross section calculated from a ladder of resonances in the center-of-mass system. This ladder was generated from a set of synthesized nuclear parameters. The best fits to the cross sections when extrapolated to zero thickness, give 13.5 +- 0.2 b at 24 keV and 11.9 +- 0.2 b at 144 keV. The value at 24 keV agrees with the ENDF/B-IV, while the value at 144 keV is approx. 4% greater.An ideal gas model including an effective mass, M/sub eff/, and an effective temperature, T/sub eff/, was used to Doppler broaden the calculated nuclear cross sections. With this model, good agreement was obtained with the EATCS data for all sample thickness at all temperatures with an M/sub eff/ of 238 amu for the /sup 238/U metal and 400 amu for /sup 238/U in U/sub 3/O/sub 8/. The temperature dependence of t/sub eff/ was determined by calculating the total energy by use of Debye frequency theta/sub v/ distributions. In these calculations, the Debye temperatures, theta/sub D/, that provided the best fits were theta/sub D/ = 260 K for the metal and theta/sub D/ = 545 K for U/sub 3/O/sub 8/. 9 figures, 1 table.
- OSTI ID:
- 5575705
- Journal Information:
- Nucl. Sci. Eng.; (United States), Vol. 72:1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
NEUTRON REACTIONS
TOTAL CROSS SECTIONS
URANIUM 238 TARGET
DOPPLER EFFECT
EXPERIMENTAL DATA
FAST NEUTRONS
GRAPHS
HIGH TEMPERATURE
INTERMEDIATE NEUTRONS
KEV RANGE 10-100
KEV RANGE 100-1000
LINE BROADENING
LOW TEMPERATURE
MEDIUM TEMPERATURE
RESONANCE
TEMPERATURE DEPENDENCE
THEORETICAL DATA
THICKNESS
URANIUM OXIDES U3O8
VERY HIGH TEMPERATURE
VERY LOW TEMPERATURE
ACTINIDE COMPOUNDS
BARYON REACTIONS
BARYONS
CHALCOGENIDES
CROSS SECTIONS
DATA
DATA FORMS
DIMENSIONS
ELEMENTARY PARTICLES
ENERGY RANGE
FERMIONS
HADRON REACTIONS
HADRONS
INFORMATION
KEV RANGE
NEUTRONS
NUCLEAR REACTIONS
NUCLEON REACTIONS
NUCLEONS
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
TARGETS
URANIUM COMPOUNDS
URANIUM OXIDES
652025* - Nuclear Properties & Reactions
A=220 & above
Experimental- Nuclear Reactions & Scattering- (-1987)