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
August 2026
Nuclear Technology
Fusion Science and Technology
Latest News
Aalo Atomics achieves criticality on July 4
Executive Order 14301 set an ambitious goal for at least three test reactors to achieve criticality by July 4. Two private companies participating in the Department of Energy’s Reactor Pilot Program—Antares and Valar Atomics—reached this stage earlier in June, and Deployable Energy—participating in the DOE's Nuclear Energy Launch Pad—became the third last week.
In the last few weeks, reports indicated that Aalo would be next, reaching criticality at Idaho National Laboratory with a low-enriched uranium–fueled, sodium-cooled reactor on or near the target date set forth by President Trump’s EO 14301. In the early hours of July 4, Aalo’s critical test reactor—a full-scale zero-power version of its planned 10-MWe Aalo-X—did just that, becoming the fourth DOE-authorized reactor to hit the milestone.
Jingshang Zhang
Nuclear Science and Engineering | Volume 114 | Number 1 | May 1993 | Pages 55-63
Technical Paper | doi.org/10.13182/NSE93-3
Articles are hosted by Taylor and Francis Online.
The master equation theory of precompound and compound nuclear reactions has been generalized to include the conservation of angular momentum and parity. Based on this improved semi-classical theory, the UNF code has been developed as a tool for calculating nucleon-induced reaction cross sections and double-differential cross sections at incident neutron energies below 20 MeV. It is demonstrated that the code contains the Hauser-Feshbach model and the exciton models as the limiting cases. The unified treatment of equilibrium and pre-equilibrium reaction processes includes the introduction of composite particle formation factors in calculations of pickup-type composite particle emissions. A method to calculate the double-differential cross sections for all kinds of particles is proposed based on the leading particle model.
