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Division Spotlight
Fusion Energy
This division promotes the development and timely introduction of fusion energy as a sustainable energy source with favorable economic, environmental, and safety attributes. The division cooperates with other organizations on common issues of multidisciplinary fusion science and technology, conducts professional meetings, and disseminates technical information in support of these goals. Members focus on the assessment and resolution of critical developmental issues for practical fusion energy applications.
Meeting Spotlight
Conference on Nuclear Training and Education: A Biennial International Forum (CONTE 2025)
February 3–6, 2025
Amelia Island, FL|Omni Amelia Island Resort
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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Christmas Night
Twas the night before Christmas when all through the houseNo electrons were flowing through even my mouse.
All devices were plugged in by the chimney with careWith the hope that St. Nikola Tesla would share.
Michael Y. Hua, Jesson D. Hutchinson, George E. McKenzie, Tony H. Shin, Shaun D. Clarke, Sara A. Pozzi
Nuclear Science and Engineering | Volume 194 | Number 1 | January 2020 | Pages 56-68
Technical Paper | doi.org/10.1080/00295639.2019.1654327
Articles are hosted by Taylor and Francis Online.
Rossi-alpha measurements of fissionable assemblies are used to estimate the prompt neutron decay constant α. Reactivity can be inferred from α if the values of the neutron generation time and effective delayed neutron fraction are assumed. If multiple measurements are performed on an assembly near delayed critical, one can determine α at delayed critical and directly infer reactivity (without needing to assume values for the neutron generation time or effective delayed neutron fraction). Previous works have demonstrated that two-exponential fits for Rossi-alpha measurements of reflected assemblies have better fit metrics than those of one-exponential fits; however, the two-exponential probability density function that is needed to obtain α from the fit parameters has not been derived. This paper derives the two-exponential fit based on a two-region point kinetics model for Rossi-alpha measurements of reflected assemblies, a generalization of the current, one-region model (one-exponential fit). The new model is validated for shielded assemblies, a special case of reflected assemblies where the reflector-to-core leakage is negligibly small. The validation is performed using shielded, fissionable assemblies (highly enriched uranium with keff ≈ 0.95 and weapons-grade plutonium with keff > 0.77). The results show that the two-exponential model can (1) predict the constant α within two standard deviations, and (2) deconvolve α and the time a neutron spends in the reflector region, neither of which is possible with the one-exponential model.