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Division Spotlight
Fuel Cycle & Waste Management
Devoted to all aspects of the nuclear fuel cycle including waste management, worldwide. Division specific areas of interest and involvement include uranium conversion and enrichment; fuel fabrication, management (in-core and ex-core) and recycle; transportation; safeguards; high-level, low-level and mixed waste management and disposal; public policy and program management; decontamination and decommissioning environmental restoration; and excess weapons materials disposition.
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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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.”
Kil-Sup Um, Seok-Hee Ryu, Yong-Seog Choi, Goon-Cherl Park
Nuclear Technology | Volume 125 | Number 3 | March 1999 | Pages 305-315
Technical Paper | Thermal Hydraulics | doi.org/10.13182/NT99-A2949
Articles are hosted by Taylor and Francis Online.
Asymmetric thermal-hydraulic conditions between loops in nuclear power plants (NPPs) may produce a nonuniform temperature distribution at the core inlet if the coolant is not mixed perfectly in the lower plenum. These uneven core inlet conditions, which may be formed remarkably during a postulated steam-line-break (SLB) accident, induce a distortion in the core power distribution, which can affect the thermal margin. Thus, to estimate the thermal margin under abnormal inlet conditions, it is necessary to predict correctly thermal mixing phenomena in the lower plenum. For this purpose, reactor internals scaled down with a flow-to-area ratio are added in the lower plenum of the loop test facility, manufactured with a scaling factor of 1/710 by volume and based on a Westinghouse-type two-loop NPP in Korea. The mixing tests in the lower plenum are performed under various loop temperature imbalances at low pressures. It is found that complete mixing hardly occurs in the lower plenum at any test condition. Also, the tests are simulated by the COMMIX-1B multidimensional thermal-hydraulic code. A comparison of the simulation results with the test results shows a good agreement, and thus it is concluded that COMMIX-1B can be applied to determine the mixing patterns under the asymmetric loop conditions of a real NPP. As for applications, the temperature distributions at the core inlet under asymmetric conditions induced by the postulated SLB accident in Kori Unit 1 are determined by COMMIX-1B, and thermal margins for the SLB accident are estimated. Analyses show that the thermal margins can be improved by using more realistic core inlet temperature patterns instead of NPP design patterns.