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Nuclear Energy Conference & Expo (NECX)
September 8–11, 2025
Atlanta, GA|Atlanta Marriott Marquis
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Latest News
Sandia and Aeva evaluate intrusion detection system
Sandia National Laboratories is collaborating with the California-based Aeva Technologies, a developer of next-generation sensing and perception systems, on the development of technology for strengthening security at U.S. nuclear reactor sites.
Annalisa Manera, Horst-Michael Prasser, Dirk Lucas
Nuclear Technology | Volume 158 | Number 2 | May 2007 | Pages 275-290
Technical Paper | Nuclear Reactor Thermal Hydraulics | doi.org/10.13182/NT07-A3842
Articles are hosted by Taylor and Francis Online.
Experiments with air-water flows have been carried out in a vertical pipe of ~194-mm diameter and 9-m length, and a wide range of superficial liquid and gas velocities has been covered. At a distance of 7.6 m from the air injection, two wire-mesh sensors are installed, located at a distance of 63.3 mm from each other. The wire-mesh sensors measure sequences of instantaneous two-dimensional gas-fraction distributions in the cross section in which they are mounted, with a spatial resolution of 3 mm and a frequency of 2500 Hz. The spatial cross-correlations of the gas-fraction signals have been evaluated, and on their basis turbulent diffusion coefficients have been estimated.It is found that for a given liquid superficial velocity, a sudden increase of the diffusion coefficient takes place when the superficial gas velocity is increased above a certain value. The abrupt increase of the diffusion coefficient occurs in correspondence of the transition from mono- to bimodal bubble size distributions.The experimental diffusion coefficients are compared with the prediction of the Sato model (experimental gas-fraction profiles and bubble size distributions are given as input). Even though this model has been developed for bubbly flow, the general trends are well captured also in the churn-turbulent regime.