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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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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
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 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. 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.”
D. Guzonas, F. Brosseau, P. Tremaine, J. Meesungnoen, J.-P. Jay-Gerin
Nuclear Technology | Volume 179 | Number 2 | August 2012 | Pages 205-219
Technical Paper | Nuclear Plant Operations and Control | doi.org/10.13182/NT12-A14093
Articles are hosted by Taylor and Francis Online.
The long-term viability of a supercritical water-cooled reactor (SCWR) will depend on the ability of designers and operators to control and maintain water chemistry conditions that will minimize corrosion and the transport of both corrosion products and radionuclides, at a pressure of 25 MPa and temperatures from 300°C to 625°C. To achieve this goal, the behavior of low concentrations of impurities such as transition metal corrosion products, chemistry control agents, impurities in the feedwater, and radionuclides (fission and activation products) in subcritical and supercritical water must be understood. A second key aspect of SCWR water chemistry control will be mitigation of the effects of water radiolysis. Preliminary studies suggest markedly different behavior than that predicted by extrapolating conventional water-cooled reactor behavior. The principal challenge in predicting corrosion and fission product transport is the lack of thermochemical and kinetic data above 300°C. Calculations with extrapolated data show that the formation of neutral complexes increases with temperature and can become important under near-critical and supercritical conditions. The most important region is from 300°C to 450°C, where the properties of water change dramatically and solvent compressibility effects exert a huge influence on solvation. The potential for increased transport and deposition of corrosion products (radioactive and inactive), leading to increased deposition on fuel cladding surfaces and increased out-of-core radiation fields and worker dose, must be assessed. The commonly used strategy of adding excess hydrogen at concentrations sufficient to suppress the net radiolytic production of primary oxidizing species may not be effective in an SCWR. Because direct measurement of the chemistry under such extreme conditions of temperature, pressure, and radiation fields is difficult, the most promising approach involves a combination of theoretical calculations, chemical models, and experimental work.