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Division Spotlight
Reactor Physics
The division's objectives are to promote the advancement of knowledge and understanding of the fundamental physical phenomena characterizing nuclear reactors and other nuclear systems. The division encourages research and disseminates information through meetings and publications. Areas of technical interest include nuclear data, particle interactions and transport, reactor and nuclear systems analysis, methods, design, validation and operating experience and standards. The Wigner Award heads the awards program.
Meeting Spotlight
International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering (M&C 2025)
April 27–30, 2025
Denver, CO|The Westin Denver Downtown
Standards Program
The Standards Committee is responsible for the development and maintenance of voluntary consensus standards that address the design, analysis, and operation of components, systems, and facilities related to the application of nuclear science and technology. Find out What’s New, check out the Standards Store, or Get Involved today!
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Argonne’s METL gears up to test more sodium fast reactor components
Argonne National Laboratory has successfully swapped out an aging cold trap in the sodium test loop called METL (Mechanisms Engineering Test Loop), the Department of Energy announced April 23. The upgrade is the first of its kind in the United States in more than 30 years, according to the DOE, and will help test components and operations for the sodium-cooled fast reactors being developed now.
A. Alapour, R. A. Karam
Nuclear Science and Engineering | Volume 79 | Number 3 | November 1981 | Pages 278-298
Technical Paper | doi.org/10.13182/NSE81-A19405
Articles are hosted by Taylor and Francis Online.
It is commonly accepted that the resonance reaction rate of any material increases when the temperature is raised. Using an exact Doppler-broadening kernel based on the Maxwellian distribution of nuclear velocities and an accurate integral transport method, we have shown that in a nuclear reactor the increase in resonance reaction rates with temperature at relatively high energy shifts the fine structure neutron spectrum in such a way that a net decrease in the neutron flux results at lower energies. In fast reactors, the decrease in the neutron flux at lower energy becomes more than the decrease in the self-shielding due to Doppler broadening and the net effect is a decrease in the resonance reaction rates. The quantification of the various components of the Doppler coefficient, T(dk/dT), in the liquid-metal fast breeder reactor benchmark (zero power reactor-6 Assembly 7) reveals that the spectral shift induced primarily by the broadening of 238U resonances causes the fissile material, 239Pu, to have a large negative (not positive) Doppler effect, which is 38% of the total. This prompt negative feedback indicates that prorating the Doppler signal by summing the Doppler contribution from each isotope based on first-order perturbation can lead to an error in the transient analysis. Calculation of the natural UO2 sample Doppler worth in this assembly, in which the spectral shift effects are included, gives good agreement with the measured value.
