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
July 2026
Fusion Science and Technology
Latest News
The deadline arrives: Checking in on the Reactor Pilot Program
On May 23, 2025, President Trump signed Executive Order 14301, “Reforming Nuclear Reactor Testing at the DOE,” which instructed the Department of Energy to create a Reactor Pilot Program (RPP)—a new system in which companies could pursue DOE authorization to build and test their first-of-a-kind nuclear technologies. EO 14301 set an ambitious goal for that program: three reactors achieving criticality by July 4, 2026.
Mark L. Williams, R. Raharjo
Nuclear Science and Engineering | Volume 126 | Number 1 | May 1997 | Pages 19-34
Technical Paper | doi.org/10.13182/NSE97-2
Articles are hosted by Taylor and Francis Online.
A new method is developed to determine space-dependent, self-shielded cross sections for resonance nuclides with no overlapping resonances, contained in an arbitrarily shaped absorber body within some general lattice configuration. The theoretical basis for the method is discussed, and analytical expressions are presented for the space-dependent flux spectrum in the vicinity of an isolated resonance and for the space-dependent variation in the shielded resonance integral and multigroup cross section. The shielded cross-section expressions contain space-dependent, “weighted escape probabilities” that correspond to the weighted average of the energy-dependent escape probability over each energy group. The method is implemented in an assembly lattice physics code, and results are compared to those obtained with a highly accurate transport theory calculation that uses pointwise cross-section data. The method gives good agreement for the radial variation in the self-shielded cross section through a boiling water reactor fuel pellet.