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Division Spotlight
Accelerator Applications
The division was organized to promote the advancement of knowledge of the use of particle accelerator technologies for nuclear and other applications. It focuses on production of neutrons and other particles, utilization of these particles for scientific or industrial purposes, such as the production or destruction of radionuclides significant to energy, medicine, defense or other endeavors, as well as imaging and diagnostics.
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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Nuclear Science and Engineering
August 2024
Nuclear Technology
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Latest News
Vogtle-3 shuts down for valve issue
One of the new Vogtle units in Georgia was shut down unexpectedly on Monday last week for a valve issue that has since been investigated and repaired. According to multiple local news outlets, Georgia Power reported on July 17 that Unit 3 was back in service.
Southern Company spokesperson Jacob Hawkins confirmed that Vogtle-3 went off line at 9:25 p.m. local time on July 8 “due to lowering water levels in the steam generators caused by a valve issue on one of the three main feedwater pumps.”
Enzo Curti, Matthias Krack, Daniel Grolimund (Paul Scherrer Inst), Sergey V. Churakov (Paul Scherrer Inst/Univ of Bern)
Proceedings | 16th International High-Level Radioactive Waste Management Conference (IHLRWM 2017) | Charlotte, NC, April 9-13, 2017 | Pages 281-285
The long-lived nuclide 79Se plays a key role in safety assessments for underground radioactive waste repositories. In general, Se is assumed to diffuse out of the fuel grains and to migrate toward the periphery of fuel pellets due to the high thermal gradient during LWR reactor operation, similarly to the volatile elements I and Cs. According to this model, a significant part of the 79Se inventory in spent fuel would be readily accessible to leaching after water ingress in the repository. However, contrary to these expectations, leach experiments did not show measurable Se release after exposing spent UO2 fuel samples to aqueous solutions during up to one year.
In order to explain this result, X-ray absorption near edge structure (XANES) spectra were measured on microsamples of high-burnup UO2 spent fuel from two light water reactors. The results indicate that Se occurs in the fuel as sparingly soluble, almost immobile Se(-II) ion (selenide). The occurrence of soluble oxidized forms of Se could be ruled out. Theoretical XANES calculations proved to be consistent with Se occupying oxygen sites in the UO2 crystal structure.
From these results we conclude that the release of 79Se from UO2 spent fuel in an underground repository will be controlled by the slow dissolution of the fuel matrix and not by early short-term release. Our spectroscopic data thus explain why dissolved Se was not detected in the leach experiments. Moreover, they are essential to reliably define critical source term parameters, specifically the "Instant Release Fraction" (IRF), in performance assessment calculations.