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Conference Spotlight
Nuclear Energy Conference & Expo (NECX)
September 8–11, 2025
Atlanta, GA|Atlanta Marriott Marquis
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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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DOE issues new NEPA rule and procedures—and accelerates DOME reactor testing
Meeting a deadline set in President Trump’s May 23 executive order “Reforming Nuclear Reactor Testing at the Department of Energy,” the DOE on June 30 updated information on its National Environmental Policy Act (NEPA) rulemaking and implementation procedures and published on its website an interim final rule that rescinds existing regulations alongside new implementing procedures.
H. K. Cho, B. J. Yun, C.-H. Song, G. C. Park
Nuclear Science and Engineering | Volume 156 | Number 1 | May 2007 | Pages 40-54
Technical Paper | doi.org/10.13182/NSE07-A2683
Articles are hosted by Taylor and Francis Online.
In a nuclear reactor vessel downcomer incorporating the safety feature of direct vessel injection (DVI), the direct bypass of emergency core coolant (ECC) is activated during the reflood phase of a large-break loss-of-coolant accident due to momentum transfer between the downward liquid film and transverse gas. Direct ECC bypass is reportedly the major bypass mechanism of ECC, and various experiments have been performed to obtain detailed information about the ECC bypass in a DVI downcomer. In the present study, a model of the direct ECC bypass was developed based on two-dimensional two-fluid equations for the adiabatic two-phase flow to predict the ECC bypass flow rate. The direct ECC bypass fractions were calculated with various interfacial friction factor correlations, and the results were compared with the available experimental data. The values predicted by the current model showed reasonably good agreement with the experimental data at bypass fractions >40% when applying the interfacial friction factor model developed in a countercurrent flow condition. However, when the bypass fraction was <40%, models incorporating cocurrent annular flow provided better results than those with countercurrent flow. These results suggest that a transition occurs from a smooth film to a rough film as the gas flow rate increases, and hence, interfacial friction factor models that adequately incorporate this transition are necessary to predict the direct ECC bypass phenomenon.