ANS is committed to advancing, fostering, and promoting the development and application of nuclear sciences and technologies to benefit society.
Explore the many uses for nuclear science and its impact on energy, the environment, healthcare, food, and more.
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
ANS Student Conference 2025
April 3–5, 2025
Albuquerque, NM|The University of New Mexico
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!
Latest Magazine Issues
Mar 2025
Jul 2024
Latest Journal Issues
Nuclear Science and Engineering
March 2025
Nuclear Technology
Fusion Science and Technology
April 2025
Latest News
Nuclear News 40 Under 40 discuss the future of nuclear
Seven members of the inaugural Nuclear News 40 Under 40 came together on March 4 to discuss the current state of nuclear energy and what the future might hold for science, industry, and the public in terms of nuclear development.
To hear more insights from this talented group of young professionals, watch the “40 Under 40 Roundtable: Perspectives from Nuclear’s Rising Stars” on the ANS website.
James J. Barker, Robert F. Benenati
Nuclear Science and Engineering | Volume 21 | Number 3 | March 1965 | Pages 319-324
Technical Paper | doi.org/10.13182/NSE65-A20035
Articles are hosted by Taylor and Francis Online.
To assess diffusion's importance, the temperature distribution in a cylindrical reactor is derived for a coolant with uniform properties and velocity, taking into account both radial and axial diffusion, for a cosine-J0 power distribution. The fractional temperature rise of the coolant is found to be where Ε(z) = [sin(z) + sin(Ζ)]/2 sin(Ζ), z= π x/2Η′, x is the axial distance from the core center, -Η and Η′ are the core half-height and extrapolated half-height, -Η≤x≤Η; Fn = 1/J0(Pn)·[(Pn/2.405P)2-10, J1(Pn) = 0, P= R/R′ = core radius/extrapolated radius, ρ = r/R, r = radial distance from axis, 0≤r≤R;an = = βnH/Z, 2 Αβn + 1 =[1+4ΑΒ(Pn/R)2]½ , Α = axial diffusivity /u, Β = radial diffusivity /u, u = coolant axial velocity, and The expression is evaluated for a variety of values for all the parameters, and the results are discussed analytically and presented in tables and graphs. The effect is dependent upon the relative size of the diffusion eddies in comparison with the dimensions of the reactor. The eddy diffusivity is proportional to the size of the particles in the bed and is about ten times larger axially than radially. A small core with large fuel particles will be affected by eddy diffusion, thereby reducing hot spots, but a large core with small particles will not. For a core 8 ft in diameter cooled by sodium flowing at 2 ft/sec, the effect is perceptible with 2-in. particles, but not with 0.2-in. particles.