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
Nuclear Energy Conference & Expo (NECX)
September 8–11, 2025
Atlanta, GA|Atlanta Marriott Marquis
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
Jul 2025
Jan 2025
Latest Journal Issues
Nuclear Science and Engineering
August 2025
Nuclear Technology
Fusion Science and Technology
July 2025
Latest News
DOE issues new NEPA rule and procedures—and accelerates DOME reactor testing
Meeting a deadline set in President Trump’s May 23 executive order “Reforming Nuclear Reactor Testing at the Department of Energy,” the DOE on June 30 updated information on its National Environmental Policy Act (NEPA) rulemaking and implementation procedures and published on its website an interim final rule that rescinds existing regulations alongside new implementing procedures.
Jesson Hutchinson, Timothy Valentine
Nuclear Science and Engineering | Volume 161 | Number 3 | March 2009 | Pages 357-362
Technical Paper | doi.org/10.13182/NSE161-357
Articles are hosted by Taylor and Francis Online.
Subcritical measurements were conducted with an alpha-phase plutonium sphere using the 252Cf source-driven noise analysis method. Measurements were performed with both polyethylene and acrylic reflectors. For each reflector type, five different reflector thicknesses were investigated: 0 (bare), 1.27, 2.54, 3.81, and 7.62 cm. A certain ratio of spectral quantities that depends on the fluctuations in the fission chain multiplication process was measured for each configuration. In addition, two types of Monte Carlo calculations were employed to estimate the keff and spectral ratio values of each configuration. From the measured and computed quantities, the multiplication and uncertainty of the system can be inferred. The polyethylene measurements compared well to previous measurements conducted with the same plutonium sphere and polyethylene reflector thicknesses. The acrylic measurements provide benchmark data of an alpha-phase plutonium sphere reflected by acrylic.