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Nuclear Criticality Safety
NCSD provides communication among nuclear criticality safety professionals through the development of standards, the evolution of training methods and materials, the presentation of technical data and procedures, and the creation of specialty publications. In these ways, the division furthers the exchange of technical information on nuclear criticality safety with the ultimate goal of promoting the safe handling of fissionable materials outside reactors.
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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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A look inside NIST’s work to optimize cancer treatment and radiation dosimetry
In an article just published by the Taking Measure blog of the National Institute of Standards and Technology, Stephen Russek—who leads the Imaging Physics Project in the Magnetic Imaging Group at NIST and codirects the MRI Biomarker Measurement Service—describes his team’s work using phantom stand-ins for human tissue.
Per Seltborg, Jan Wallenius
Nuclear Science and Engineering | Volume 154 | Number 2 | October 2006 | Pages 202-214
Technical Paper | doi.org/10.13182/NSE06-A2626
Articles are hosted by Taylor and Francis Online.
The distribution of actinides in the core of an accelerator-driven system loaded with plutonium, americium, and curium has been studied in order to optimize the proton source efficiency *. The optimization of * was performed by keeping some important characteristics of the system, e.g., the radial power profile and the reactivity of the core, constant. One of the basic assumptions of the study, that the magnitude of * is sensitive primarily to the composition of actinides in the inner part of the core, whereas only marginally to that in the outer part, has been confirmed. It has been shown that the odd-N nuclides (those nuclides with an even number of neutrons) in general and 241Am and 244Cm in particular have favorable properties with respect to improving * if they are placed in the innermost part of the core. The underlying reason for this phenomenon is that the energy spectrum of the source neutrons in the inner part of the core is harder than that of the average fission neutrons. Moreover, it has been shown that loading the inner part of the core with only curium increases * by ~7%. Plutonium, on the other hand, in particular high-quality plutonium consisting mainly of 239Pu and 241Pu, was found to be a comparatively source inefficient element and is preferably located in the outer part of the core. The differences in * are due to combined effects from relative changes in the average fission and capture cross sections and in the average fission neutron yield.