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Division Spotlight
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.
Meeting Spotlight
International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering (M&C 2025)
April 27–30, 2025
Denver, CO|The Westin Denver Downtown
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
Argonne’s METL gears up to test more sodium fast reactor components
Argonne National Laboratory has successfully swapped out an aging cold trap in the sodium test loop called METL (Mechanisms Engineering Test Loop), the Department of Energy announced April 23. The upgrade is the first of its kind in the United States in more than 30 years, according to the DOE, and will help test components and operations for the sodium-cooled fast reactors being developed now.
Yasushi Nomura, Yoshitaka Naito
Nuclear Technology | Volume 121 | Number 1 | January 1998 | Pages 3-13
Technical Paper | Kiyose Birthday Anniversary | doi.org/10.13182/NT98-A2814
Articles are hosted by Taylor and Francis Online.
Scenario identification, preparation of reliability data, and fault-tree construction were conducted for a criticality in a pulsed column of a typical model of a reprocessing facility to find a weak link in the system. The plant system data, the basic reliability data with the fault-tree analysis code FTL, were supplied from NUKEM GmbH, Germany. In this exercise, a low nitric acid concentration in the scrub flow to the pulsed column is initiated by failures of the reagent preparation system of the primary separation cycle, triggering plutonium accumulation, eventually exceeding the safety limit of the scrub column, and thus a criticality accident occurs. The occurrence frequency was evaluated to be 2.2 × 10-5/yr for this most conservative case of the accident scenario. The main contributor was investigated by the fault-tree branch analysis and identified to be human error relating to the sampling measurement for fresh nitric acid scrub feed. Because 2.2 × 10-5/yr is quite a high value in comparison with the generally accepted 10-6/yr, Monte Carlo uncertainty analysis assuming an error factor of 5 for each of the reliability data was conducted to predict a 90% confidence range of 1.9 × 10-6/yr to 8.25 × 10-5/yr. In addition, there might be unforeseen equipment failures related to the same criticality scenario. The additional analysis and discussion lead to the recommendation to adopt shape and dimension control in the design stage for the whole range of plutonium concentrations from a criticality safety point of view.
