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.
L. L. Briggs, W. F. Miller, Jr., E. E. Lewis
Nuclear Science and Engineering | Volume 57 | Number 3 | July 1975 | Pages 205-217
Technical Paper | doi.org/10.13182/NSE75-A26752
Articles are hosted by Taylor and Francis Online.
A generalization is made of a previous phase-space finite element approximation of the second-order form of the one-group, two-dimensional neutron transport equation in x-y geometry. Three angular approximations are formulated and compared: continuous piecewise bilinear finite element, piecewise constant finite element, and discrete ordinate. These are incorporated into a unified formalism of discrete ordinate-like equations, enabling the spatial variables to be treated identically using piecewise linear or bilinear finite elements. The resulting equations are solved iteratively by a weighted conjugate gradient method in an improved version of the computer code FENT. Numerical and analytical comparisons of the angular approximations are made, and it is found that both piecewise bilinear and piecewise constant approximations in angle substantially mitigate ray effects. The mitigation is shown to be associated closely with transformation of the hyperbolic discrete ordinate equations to the elliptic operators of the discrete ordinatelike finite element approximations. This transformation is accompanied by the disappearance of the characteristics along the discrete lines of neutron travel, and, hence, by the appearance of physically artificial derivative terms normal to the lines of neutron streaming. These terms grow with the subdomains of the angular finite elements.