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 Nuclear Energy Conference & Expo (NECX)
August 24–27, 2026
Dallas, TX|Hilton Anatole
Latest Magazine Issues
Jul 2026
Jan 2026
2026
Latest Journal Issues
Nuclear Science and Engineering
September 2026
Nuclear Technology
August 2026
Fusion Science and Technology
Latest News
In transition: Commercializing fusion power
Commercial fusion power is closer than ever. There are now around 30 U.S. fusion companies, several of which claim to be on track to connect to the grid as early as the 2030s.
Tokamak and laser inertial confinement approaches benefit from decades of research at facilities such as the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory and ITER, with alternative concepts including stellarator, magnetic mirror, and Z-pinch confinement also making notable progress as private and government funding for fusion increases.
M. Segev
Nuclear Science and Engineering | Volume 67 | Number 2 | August 1978 | Pages 221-234
Technical Paper | doi.org/10.13182/NSE78-A15437
Articles are hosted by Taylor and Francis Online.
The Adler-Adler cross-section formalism with energy-dependent parameters is a practical approximation to the R-Matrix formalism, based on the smallness of the s-wave neutron width in fissile elements. Attempts have been made to represent experimental cross sections by the Adler-Adler formulas through an initial representation by the Reich-Moore approximation of R-Matrix and a subsequent conversion of the Reich-Moore formulas to the Adler-Adler formulas. Adler and Adler had foreseen difficulties in associating their formulas with approximate R-Matrix theories such as those of Reich-Moore. Indeed, it is shown that due to the nonunitarity of the Adler-Adler formalism on the one hand and the unitarity, by definition, of the Reich-Moore formalism on the other hand, the conversion from the latter to the former is ambiguous. Examples are shown to demonstrate that this ambiguity results in numerical inaccuracies, sometimes very large ones, for neutron widths that are not extremely small. Improved Adler-Adler-type formulas have been derived from the R-Matrix formalism. In these formulas, the multipliers of the Breit-Wigner resonance lines exhibit more explicit energy dependence than their original counterparts, mainly in the form of additional terms in the formula for the total cross section. The conversion from Reich-Moore cross sections to the improved resonance formulas is shown to be much less ambiguous and to produce very accurate cross sections. In particular, the inaccuracies encountered with the Reich-Moore-Adler-Adler conversion are eliminated. A computer code, PEDRA, was written to perform the conversion from a given set of Reich-Moore parameters to the parameters required in the improved formulas. The numerical algorithm of this code is based on an adaptation with modifications of the numerical approach of de Saussure-Perez in the POLLA code, which converts Reich-Moore parameters to Adler-Adler parameters.