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Operations & Power
Members focus on the dissemination of knowledge and information in the area of power reactors with particular application to the production of electric power and process heat. The division sponsors meetings on the coverage of applied nuclear science and engineering as related to power plants, non-power reactors, and other nuclear facilities. It encourages and assists with the dissemination of knowledge pertinent to the safe and efficient operation of nuclear facilities through professional staff development, information exchange, and supporting the generation of viable solutions to current issues.
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2024 ANS Winter Conference and Expo
November 17–21, 2024
Orlando, FL|Renaissance Orlando at SeaWorld
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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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ECA warns of delay to DOE’s interpretation of HLW
The Energy Communities Alliance (ECA), which advocates for communities adjacent to or impacted by Department of Energy sites, is asking the department to conduct an independent analysis evaluating the impacts of delaying the implementation of its statutory interpretation of high-level radioactive waste, which holds that some waste from the reprocessing of spent nuclear fuel may be classified as non-HLW.
W. S. Winters, Jr., H. Merte, Jr.
Nuclear Science and Engineering | Volume 69 | Number 3 | March 1979 | Pages 411-429
Technical Paper | doi.org/10.13182/NSE79-A19959
Articles are hosted by Taylor and Francis Online.
Phase equilibrium blowdown models are not valid for geometries having small characteristic lengths (volume-to-break-area ratios). For such geometries, the two-phase expansion is too rapid to permit adequate heat and mass transfer between liquid and vapor to maintain phase equilibrium. The two-phase expansions observed during the present pipe blowdown experiments with dichlorodifluoromethane (R-12) were found to exhibit pronounced nonequilibrium behavior. Decompression transients were characterized by a rapid drop in pressure from the initial value to levels well below the initial saturation pressure. The pressure recovery caused by delayed growth of the vapor in superheated liquid leveled off to pressure plateaus well below the initial saturation pressure. Long-term blowdown transients were not affected by the initial pressure level, but initial temperature and pipe geometry were observed to have a pronounced influence. Higher initial temperatures resulted in higher pressure plateaus and shorter blowdown times. The rapid phase expansions occurring in pipe geometries having small volume-to-break-area ratios resulted in greater departures from phase equilibrium, as evidenced by the lower pressure plateaus observed experimentally. Transient temperature measurements indicated substantial temperature differences between liquid and vapor during blowdown. Furthermore, the vapor was observed to be saturated with respect to the system pressure for most of the blowdown event. To describe this experimentally observed nonequilibrium behavior, a model was formulated that treats the expanding two-phase fluid as a pseudo-homogeneous mixture of uniformly distributed, heat transfer dominated, spherical vapor bubbles surrounded by superheated liquid. By adjusting two empirical parameters—discharge coefficient, Cd, and bubble density, N—to permit the model to simulate R-12 blowdown from one particular blowdown geometry and set of initial conditions, it was possible to use the model in predicting R-12 blowdown transients for other geometries and initial conditions as well as for pipe water blowdown. The nonequilibrium model predictions were considerably more accurate than those of the phase equilibrium model, although consistent discrepancies were observed in all model-data comparisons. It is believed that two-dimensional effects near the pipe exit, liquid inertia influences on bubble growth, and limitations in the choked flow model are primarily responsible for the discrepancies.