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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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Latest News
First astatine-labeled compound shipped in the U.S.
The Department of Energy’s National Isotope Development Center (NIDC) on March 31 announced the successful long-distance shipment in the United States of a biologically active compound labeled with the medical radioisotope astatine-211 (At-211). Because previous shipments have included only the “bare” isotope, the NIDC has described the development as “unleashing medical innovation.”
Thomas M. Sutton
Nuclear Science and Engineering | Volume 197 | Number 2 | February 2023 | Pages 164-175
Technical Paper | doi.org/10.1080/00295639.2022.2065872
Articles are hosted by Taylor and Francis Online.
The results of neutron Monte Carlo (MC) transport calculations are subject to random fluctuations about their expected values. The term “neutron clustering” refers to situations in which these fluctuations exhibit particularly strong spatial correlations in iterated-fission-source calculations. Various idealized models of the MC process have been developed to study this phenomenon. Over time, these models have evolved to more realistically reflect the algorithms used in MC codes. This paper continues along this path by including the possibility that some neutrons will not terminate in an event that can potentially produce new neutrons and by considering an algorithm without replacement (WOR) for selecting the neutron source sites. It is shown that sampling source sites WOR versus with replacement can greatly reduce the degree of clustering.