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.
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.
2024 ANS Annual Conference
June 16–19, 2024
Las Vegas, NV|Mandalay Bay Resort and Casino
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
Latest Journal Issues
Nuclear Science and Engineering
Fusion Science and Technology
What is involved in radiation protection at accelerator facilities?
Particle accelerators have evolved from exotic machines probing hadron interactions to understand the fundamentals of our world to widely used instruments in research and for medical and industrial use. For research purposes, high-power machines are employed, often producing secondary particle beams through primary beam interaction with a target material involving many meters of shielding. The charged beam interacts with the surrounding structures, producing both prompt radiation and secondary radiation from activated materials. After beam termination, some parts of the facility remain radioactive and potentially can become radiation hazards over time. Radiation protection for accelerator facilities involves a range of actions for operation within safe boundaries (an accelerator safety envelope). Each facility establishes fundamental safety principles, requirements, and measures to control radiation exposure to people and the release of radioactive material in the environment.
David Reger, Elia Merzari, Paolo Balestra, Sebastian Schunert, Yassin Hassan, Haomin Yuan, Yu-Hsiang Lan, Paul Fischer, Misun Min
Nuclear Technology | Volume 209 | Number 1 | January 2023 | Pages 90-104
Technical Paper | doi.org/10.1080/00295450.2022.2108688
Articles are hosted by Taylor and Francis Online.
Packed beds play an important role in many engineering fields, with their applications in nuclear energy being driven by the development of next-generation reactors utilizing pebble fuel. The random nature of a packed pebble bed creates a flow field that is complex and difficult to predict. Porous media models are an attractive option for modeling pebble-bed reactors (PBRs), as they provide intermediate fidelity results and are computationally efficient. Porous media models, however, rely on the use of correlations to estimate the effect of complicated flow features on the pressure drop and heat transfer in the system. Existing correlations were developed to predict the average behavior of the bed, but they are inaccurate in the near-wall region where the presence of the wall affects the pebble packing.
This work aims to investigate the accuracy of a porous media model using the Kerntechnischer Ausschuss (KTA) correlation, the most common pressure drop correlation for PBRs compared to the high-fidelity large eddy simulation (LES). A bed of 1568 pebbles is investigated at Reynolds numbers from 625 to 10 000. The bed is divided into five concentric subdomains to compare the average velocity, friction losses, and form losses between the porous media and LES codes. The comparison between the LES simulation and the KTA correlation revealed that the KTA correlation largely underpredicts the form losses in the near-wall region, leading to an overprediction of the velocity near the wall by nearly 30%. An investigation of the form losses across the range of Reynolds numbers in the LES results provided additional insight into how the KTA correlation may be improved to better predict these spatial effects in a pebble bed. These data suggest that the form coefficient near the wall must be increased by 48% while decreasing the form coefficient of the inner bulk region of the bed by 15%. The implementation of these improvements to the KTA correlation in a porous media model produced a radial velocity profile that saw significantly improved agreement with the LES results.