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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!
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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.
J. A. Gomez, P. E. Koehler, T. E. Cutler, A. DeYoung, J. T. Goorley, J. D. Hutchinson, G. McKenzie, G. L. Morgan, S. M. Mosby, W. L. Myers, R. S. Rundberg, V. W. Yuan
Nuclear Science and Engineering | Volume 193 | Number 5 | May 2019 | Pages 537-548
Technical Paper | doi.org/10.1080/00295639.2018.1545956
Articles are hosted by Taylor and Francis Online.
Neutron diagnosed subcritical experiments (NDSEs) aim to measure the fission chain decay of subcritical test objects initiated by neutrons from an external source. The ultimate goal of future NDSEs is to make such measurements on dynamic subcritical objects as they are imploded. As a step toward that goal, we made measurements on three static subcritical assemblies containing highly enriched uranium. Specifically, we measured the die-off of both fission gamma rays and neutrons, with nanosecond resolution over several hundred microseconds, relative to the emission time of neutrons from a source in close proximity to the subcritical objects. As simulations are expected to play a key role in interpreting future NDSEs, we compared our data to detailed MCNP® calculations. There was good agreement between the data and MCNP over die-off times expected to be most important to future NDSEs, but there were significant differences at both earlier and later times. We attempted to reconcile these differences by several changes to the simulations. In particular, we found that reducing the 235U(n,n’) cross section to 80% of the current ENDF7.1 evaluation resulted in much better agreement.