ANS is committed to advancing, fostering, and promoting the development and application of nuclear sciences and technologies to benefit society.
Explore the many uses for nuclear science and its impact on energy, the environment, healthcare, food, and more.
Division Spotlight
Nuclear Criticality Safety
NCSD provides communication among nuclear criticality safety professionals through the development of standards, the evolution of training methods and materials, the presentation of technical data and procedures, and the creation of specialty publications. In these ways, the division furthers the exchange of technical information on nuclear criticality safety with the ultimate goal of promoting the safe handling of fissionable materials outside reactors.
Meeting Spotlight
ANS Student Conference 2025
April 3–5, 2025
Albuquerque, NM|The University of New Mexico
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!
Latest Magazine Issues
Apr 2025
Jan 2025
Latest Journal Issues
Nuclear Science and Engineering
May 2025
Nuclear Technology
April 2025
Fusion Science and Technology
Latest News
Norway’s Halden reactor takes first step toward decommissioning
The government of Norway has granted the transfer of the Halden research reactor from the Institute for Energy Technology (IFE) to the state agency Norwegian Nuclear Decommissioning (NND). The 25-MWt Halden boiling water reactor operated from 1958 to 2018 and was used in the research of nuclear fuel, reactor internals, plant procedures and monitoring, and human factors.
Rizwan-uddin, J. J. Doming
Nuclear Science and Engineering | Volume 100 | Number 4 | December 1988 | Pages 393-404
Technical Paper | doi.org/10.13182/NSE88-A23572
Articles are hosted by Taylor and Francis Online.
Motivated by the enhancement of heat transfer under oscillating flow conditions in single-phase heated channels and by stability problems in two-phase systems such as those in boiling water reactors, density-wave oscillations have been analyzed by numerically solving the nonlinear, variable delay, functional, ordinary integrodifferential equations that result from integrating the nonlinear partial differential equations for the single- and two-phase heated channel regions along characteristics and along channel length for axially uniform heat fluxes. The cases of constant pressure drop ΔPex across the channel (steady-state feed pump operation), exponentially decaying ΔPex (feed pump coastdown), and periodic ΔPex (feed pump oscillations) were studied. In the constant ΔPex case, the system undergoes a supercritical Hopf bifurcation from a stable fixed point to a stable limit cycle as the parameters are moved into the linearly unstable region. In the exponentially decaying ΔPex case, depending on the initial and final pressures, the system travels along a hysteresis curve, jumps at the first turning point to another stable branch, and eventually evolves to a stable limit cycle. In the periodic ΔPex case when the system is in the linearly unstable region, it usually evolves asymptotically to one of several different attracting sets, depending on the frequency of ΔPex: stable period-N limit cycles, stable invariant tori, and a chaotic (or strange) attractor. The nature of the strange attractor was analyzed quantitatively by calculating its correlation dimension —an estimate of its fractal dimension—and the dimension of the phase space in which it can be embedded. These calculations indicate that the strange attractor is indeed a fractal object of fractional dimension 2.048 ± 0.003 and embedding dimension 6. The results of these numerical studies suggest that the heated channel model can operate safely in the linearly unstable region in a dynamically stable mode without excessively large excursions when driven at many frequencies; however, at many other frequencies it cannot. The trajectories that do remain in bounded regions of phase space can be, depending on the forcing frequency, periodic with a short or very long period, very near periodic, or completely aperiodic or chaotic. Hence, it is possible to enhance heat transfer while maintaining safety in two-phase flow systems by operating them in an oscillatory mode.