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 Nonproliferation Policy
The mission of the Nuclear Nonproliferation Policy Division (NNPD) is to promote the peaceful use of nuclear technology while simultaneously preventing the diversion and misuse of nuclear material and technology through appropriate safeguards and security, and promotion of nuclear nonproliferation policies. To achieve this mission, the objectives of the NNPD are to: Promote policy that discourages the proliferation of nuclear technology and material to inappropriate entities. Provide information to ANS members, the technical community at large, opinion leaders, and decision makers to improve their understanding of nuclear nonproliferation issues. Become a recognized technical resource on nuclear nonproliferation, safeguards, and security issues. Serve as the integration and coordination body for nuclear nonproliferation activities for the ANS. Work cooperatively with other ANS divisions to achieve these objective nonproliferation policies.
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.
David J. Diamond, Sidney Yip
Nuclear Science and Engineering | Volume 40 | Number 3 | June 1970 | Pages 460-471
Technical Paper | doi.org/10.13182/NSE70-A20197
Articles are hosted by Taylor and Francis Online.
Analysis of space- and time-dependent slowing down is carried out using diffusion, P1, and B1 approximations for hydrogen and nonhydrogenous moderators. The scattering cross section is assumed to be constant, but the cross section at source neutron energy is allowed to have a different value. The calculations are primarily concerned with the first and second time moments of the flux distribution (r, v, t). The results are used to interpret the spatial variation of slowing down times. The characteristic behavior in the case of water is shown to arise from the considerably longer mean-free-path at the source energy (MeV). Time moments are also used to show that the transport approximation in P1 and B1 calculations for hydrogen can lead to a nonphysical result. Given the time moments, a simple procedure is proposed for obtaining (r, v, t). This approximation is found to be quite accurate when tested using diffusion theory moments. Comparison of theory and experiment is discussed in terms of recent measurements and Monte Carlo studies on water. So far as agreement with the available data is concerned, time-dependent diffusion theory calculations are found to be quite adequate.
