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 Annual Conference
May 31–June 3, 2026
Denver, CO|Sheraton Denver
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
Nov 2025
Jul 2025
Latest Journal Issues
Nuclear Science and Engineering
December 2025
Nuclear Technology
November 2025
Fusion Science and Technology
Latest News
The progress so far: An update on the Reactor Pilot Program
It has been about three months since the Department of Energy named 10 companies for its new Reactor Pilot Program, which maps out how the DOE would meet the goal announced by executive order in May of having three reactors achieve criticality by July 4, 2026.
Mathieu Hursin, Fan Xia, Dimitri Rochman
Nuclear Science and Engineering | Volume 199 | Number 12 | December 2025 | Pages 1987-2000
Research Article | doi.org/10.1080/00295639.2025.2508560
Articles are hosted by Taylor and Francis Online.
The paper presents an innovative approach to quickly and efficiently test new nuclear data librairies through the combined use of open source tools (library processing and deterministic transport code) and simple depletion calculations. The use of the open source deterministic transport code Dragon together with WIMS-D Library Update Project (WLUP) and PyNjoy tools allows a fully transparent process from evaluated nuclear data librairies to reactor physics calculations. When compared to a Monte Carlo reference (Serpent2), large discrepancies in terms of k-inf and 239Pu concentrations are obtained with Dragon during pin cell depletion calculations. This is further amplified by the effects of various code-specific options (energy released by fission, resonance upscattering). However, these discrepancies are shown not to affect the conclusions of a comparison between two Dragon calculations performed with the same computational options but rather using two different nuclear data libraries. The computational time is however much reduced allowing brute force sensitivity analysis (one-at-a-time approach). The performance of various recent Joint Evaluated Fission and Fusion (JEFF) evaluated nuclear data libraries (JEFF-3.3, JEFF-4T2.2, and JEFF-4T4) are assessed using this approach. It is demonstrated in the paper that using JEFF-3.3 or JEFF-4T2.2 instead of JEFF-3.1.1 leads to large k-inf differences together with burnup-dependent trends. These issues are mainly due to the nuclear data of major actinides like 235U, 238U, and 239Pu. The issue of excessive reactivity loss with burnup appears to have been resolved in JEFF-4T4.