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Division Spotlight
Reactor Physics
The division's objectives are to promote the advancement of knowledge and understanding of the fundamental physical phenomena characterizing nuclear reactors and other nuclear systems. The division encourages research and disseminates information through meetings and publications. Areas of technical interest include nuclear data, particle interactions and transport, reactor and nuclear systems analysis, methods, design, validation and operating experience and standards. The Wigner Award heads the awards program.
Meeting Spotlight
Utility Working Conference and Vendor Technology Expo (UWC 2024)
August 4–7, 2024
Marco Island, FL|JW Marriott Marco Island
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
ARPA-E announces $40 million to develop transmutation technologies for UNF
The Department of Energy’s Advanced Research Projects Agency–Energy (ARPA-E) announced $40 million in funding to develop cutting-edge technologies to enable the transmutation of used nuclear fuel into less-radioactive substances. According to ARPA-E, the new initiative addresses one of the agency’s core goals as outlined by Congress: to provide transformative solutions to improve the management, cleanup, and disposal of radioactive waste and spent nuclear fuel.
Zoltán Perkó, Danny Lathouwers, Jan Leen Kloosterman, Tim H. J. J. van der Hagen
Nuclear Science and Engineering | Volume 180 | Number 3 | July 2015 | Pages 345-377
Technical Note | doi.org/10.13182/NSE14-17
Articles are hosted by Taylor and Francis Online.
The nuclear community relies heavily on computer codes both in research and in the operation of installations. The results of such computations are useful only if they are augmented with sensitivity and uncertainty studies. This technical note presents some theoretical considerations regarding traditional first-order sensitivity analysis and uncertainty quantification involving constrained quantities. The focus is on linear constraints, which are often encountered in reactor physics problems due to energy and angle distributions, or the correlation between the isotopic abundances of elements.
A consistent theory is given for the derivation and interpretation of constrained first-order sensitivity coefficients; covariance matrix normalization procedures; their interrelation; and the treatment of constrained inputs with polynomial chaos expansion, which was the main motivation of this research. It is shown that if the covariance matrix violates the “generic zero column and row sum” condition, normalizing it is equivalent to constraining the sensitivities, but since both can be done in many ways, different sensitivity coefficients and uncertainties can be derived. This makes results ambiguous, underlining the need for proper covariance data. Furthermore, it is highlighted that certain constraining procedures can result in biased or unphysical uncertainty estimates. To confirm our conclusions, we demonstrate the presented theory on three analytical and two numerical examples including fission spectrum, isotopic distribution, and power distribution-related uncertainties, as well as the correlation between mass, volume, and density.