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
Nuclear Criticality Safety
NCSD provides communication among nuclear criticality safety professionals through the development of standards, the evolution of training methods and materials, the presentation of technical data and procedures, and the creation of specialty publications. In these ways, the division furthers the exchange of technical information on nuclear criticality safety with the ultimate goal of promoting the safe handling of fissionable materials outside reactors.
Meeting Spotlight
2024 ANS Winter Conference and Expo
November 17–21, 2024
Orlando, FL|Renaissance Orlando at SeaWorld
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
Aug 2024
Jan 2024
Latest Journal Issues
Nuclear Science and Engineering
October 2024
Nuclear Technology
Fusion Science and Technology
August 2024
Latest News
New laws offer nuclear industry incentives for existing power plant uprates
This year, the U.S. nuclear industry received a much-needed economic boost that could help preserve operating nuclear power plants and incentivize upgrades that extend their lifespan and power output.
Signed into law in 2022, the Inflation Reduction Act offers production tax credits (PTCs) for existing nuclear power plants and either PTCs or investment tax credits (ITCs) for new carbon-free generation. These credits could make power uprates—increasing the maximum power level at which a commercial plant may operate—a much more appealing option for utilities.
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%.