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.
Explore membership for yourself or for your organization.
Conference Spotlight
Nuclear Energy Conference & Expo (NECX)
September 8–11, 2025
Atlanta, GA|Atlanta Marriott Marquis
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
Jul 2025
Jan 2025
Latest Journal Issues
Nuclear Science and Engineering
August 2025
Nuclear Technology
Fusion Science and Technology
July 2025
Latest News
Hash Hashemian: Visionary leadership
As Dr. Hashem M. “Hash” Hashemian prepares to step into his term as President of the American Nuclear Society, he is clear that he wants to make the most of this unique moment.
A groundswell in public approval of nuclear is finding a home in growing governmental support that is backed by a tailwind of technological innovation. “Now is a good time to be in nuclear,” Hashemian said, as he explained the criticality of this moment and what he hoped to accomplish as president.
J. J. Volpe, J. Hardy, Jr., D. Klein
Nuclear Science and Engineering | Volume 40 | Number 1 | April 1970 | Pages 116-127
Technical Paper | doi.org/10.13182/NSE70-A18883
Articles are hosted by Taylor and Francis Online.
Thermal disadvantage factors and spectral indexes have been measured in a variety of light-water-moderated lattices. One series contained slightly enriched uranium rods in hexagonal geometry and another series used natural-uranium fuel in slab geometry. The detectors used were 164Dy, 176Lu, and 239Pu. Full energy range (0 to 10 MeV) Monte Carlo calculations with explicit cell-geometry representations were performed using the RECAP program. In addition, thermal energy range (0 to 0.625 eV) calculations were obtained with the Monte Carlo program MARC as well as with the integral transport-theory-code THERMOS. The purpose of these investigations was to test the adequacy of the various water scattering kernels—Nelkin, Koppel, and Haywood—for a broad range of thermal-flux characteristics: from a soft moderator spectrum with a steep spatial gradient to a very hard spectrum which was relatively flat as a function of position. The conclusions obtained were as follows. Calculated spectral indexes using the Haywood kernel were 2 to 3% higher than experiment, on the average, in the fuel region of these cells. Use of the Koppel kernel removed most of this disagreement in the case of 176Lu but the comparison for 239Pu remained unchanged. On the basis of these results, the thermal-flux spectrum obtained with the Haywood model appears to be slightly too hard. With regard to the disadvantage factors, good agreement was generally obtained between theory and measurement except for the tightest lattices. The calculated disadvantage factors were found to be insensitive to the kernel model selected. The effects from including thermal-scattering-pattern treatments above P1 as well as a spatially dependent and anisotropic source-to-thermal description were found to be small in these cells, < 2%.