Nuclear Science and Engineering -- ANS / Publications / Journals / Nuclear Science and Engineering

About ANS
- ANS is committed to advancing, fostering, and promoting the development and application of nuclear sciences and technologies to benefit society.
About Nuclear
- Explore the many uses for nuclear science and its impact on energy, the environment, healthcare, food, and more.
Communities
- Division Spotlight
  Radiation Protection & Shielding
  The Radiation Protection and Shielding Division is developing and promoting radiation protection and shielding aspects of nuclear science and technology — including interaction of nuclear radiation with materials and biological systems, instruments and techniques for the measurement of nuclear radiation fields, and radiation shield design and evaluation.
Events
- Meeting Spotlight
  International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering (M&C 2025)
  April 27–30, 2025
  Denver, CO|The Westin Denver Downtown
Standards
- 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!
Publications
- Latest Magazine Issues
  Apr 2025
  Jan 2025
  Latest Journal Issues
  Nuclear Science and Engineering
  May 2025
  Nuclear Technology
  May 2025
  Fusion Science and Technology
  April 2025
- Latest News
  State legislation: Delaware delving into nuclear energy possibilities
  A bill that would create a nuclear energy task force in Delaware has passed the state Senate and is now being considered in the House of Representatives.
Search

It is well established that helium formed in stainless steel by various (n,α) processes has a pronounced effect on its mechanical and dimensional properties. The anomalous production of helium in nickel-based alloys is known to take place via the two-step process: ⁵⁸Ni(n,γ)⁵⁹Ni(n,α)⁵⁶Fe. For thermal neutrons, the ⁵⁹Ni(n,α)⁵⁶Fe cross section used to calculate the helium production differs strongly from the value obtained by the direct measurements of this cross section. In this Note, this discrepancy is discussed, and a value of 12.5 ± 1 b based on direct measurements is recommended for future calculations. For fast neutrons, the contribution due to the two-step process has been ignored in the past. It is demonstrated that this contribution is substantial, and it gains in importance as the neutron fluence increases. It is further shown that the usual practice to relate helium production data to thermal- and fast-neutron fluence is inadequate. The details of the neutron spectrum and the cross section are necessary to reliably predict the helium production rate.