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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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Deep Space: The new frontier of radiation controls
In commercial nuclear power, there has always been a deliberate tension between the regulator and the utility owner. The regulator fundamentally exists to protect the worker, and the utility, to make a profit. It is a win-win balance.
From the U.S. nuclear industry has emerged a brilliantly successful occupational nuclear safety record—largely the result of an ALARA (as low as reasonably achievable) process that has driven exposure rates down to what only a decade ago would have been considered unthinkable. In the U.S. nuclear industry, the system has accomplished an excellent, nearly seamless process that succeeds to the benefit of both employee and utility owner.
Tomio Okawa, Akio Kotani, Naoya Shimada, Isao Kataoka
Nuclear Technology | Volume 158 | Number 2 | May 2007 | Pages 304-313
Technical Paper | Nuclear Reactor Thermal Hydraulics | doi.org/10.13182/NT07-A3844
Articles are hosted by Taylor and Francis Online.
The critical heat flux in an annular two-phase flow regime is influenced significantly by an obstacle placed in a flow channel. Since the transition to critical heat flux condition in this flow regime is caused by the depletion of liquid film, it is probable that the flow obstacle has a notable influence on the rate of droplet deposition and, consequently, the film flow rate in the annular regime. Also, the obstacle's effect on the deposition rate would be important in predicting the critical heat flux in a boiling water reactor core because the grid spacer can be regarded as a flow obstacle placed in the subchannel. The obstacle effect was studied experimentally for vertical upward air-water annular flow; placing 12 small tubes of different cross sections concentrically in the test section tube one by one, the influence of obstacle geometry on the deposition rate was investigated. The rate of droplet deposition markedly increased if the present tubular obstacle was placed; the rate of increase was between ~30 and 200% and depended primarily on the obstacle shape. Using the experimental data, an empirical correlation to account for the obstacle's effect was proposed.