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
2026 ANS Annual Conference
May 31–June 3, 2026
Denver, CO|Sheraton Denver
Latest Magazine Issues
May 2026
Jan 2026
2026
Latest Journal Issues
Nuclear Science and Engineering
June 2026
Nuclear Technology
Fusion Science and Technology
Latest News
NRC proposes changes to its rules on nuclear materials
In response to Executive Order 14300, “Ordering the Reform of the Nuclear Regulatory Commission,” the NRC is proposing sweeping changes to its rules governing the use of nuclear materials that are widely used in industry, medicine, and research. The changes would amend NRC regulations for the licensing of nuclear byproduct material, some source material, and some special nuclear material.
As published in the May 18 Federal Register, the NRC is seeking public comment on this proposed rule and draft interim guidance until July 2.
Bingjing Su, G. C. Pomraning
Nuclear Science and Engineering | Volume 120 | Number 2 | June 1995 | Pages 75-90
Technical Paper | doi.org/10.13182/NSE95-A24109
Articles are hosted by Taylor and Francis Online.
The problem of describing particle transport through a Markovian stochastic mixture of two immiscible materials is generally approximated by the so-called Levermore model, consisting of two coupled transport equations. In this paper, the P2 diffusive equations and the associated boundary conditions for this Levermore model are derived in planar geometry by using a variational principle, and numerical results comparing P2, P1, and S16 (benchmark) calculations are presented. These results demonstrate that the P2 equations are considerably more accurate than the P1 equations away from boundary layers. An asymptotic diffusion approximation to this model is also explored with several different boundary conditions, and the overall conclusion is that the asymptotic diffusion treatment is in general inferior to P2 theory, and its superiority over P1 theory is not overwhelming and not consistent.
