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Division Spotlight
Young Members Group
The Young Members Group works to encourage and enable all young professional members to be actively involved in the efforts and endeavors of the Society at all levels (Professional Divisions, ANS Governance, Local Sections, etc.) as they transition from the role of a student to the role of a professional. It sponsors non-technical workshops and meetings that provide professional development and networking opportunities for young professionals, collaborates with other Divisions and Groups in developing technical and non-technical content for topical and national meetings, encourages its members to participate in the activities of the Groups and Divisions that are closely related to their professional interests as well as in their local sections, introduces young members to the rules and governance structure of the Society, and nominates young professionals for awards and leadership opportunities available to members.
Meeting Spotlight
Nuclear Energy Conference & Expo (NECX)
September 8–11, 2025
Atlanta, GA|Atlanta Marriott Marquis
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!
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Latest News
Report: New York state adding 1 GW of nuclear to fleet
New York Gov. Kathy Hochul has instructed the state’s public electric utility to add at least 1 gigawatt of new nuclear by building a large-scale nuclear plant or a collection of smaller modular reactors, according to the Wall Street Journal.
Jordan Cox, Brian Woods (Oregon State Univ)
Proceedings | 2018 International Congress on Advances in Nuclear Power Plants (ICAPP 2018) | Charlotte, NC, April 8-11, 2018 | Pages 94-102
The pebble bed reactor (PBR) is generation IV reactor design that is highly efficient and passively safe. The core of a PBR consists of a silo full of graphite pebbles filled with tristructural-isotropic fuel. This fuel acts as both a moderator and radiation isotope containment preventing the release of fission biproducts. The fuel elements are first piled in the core until criticality is reached. As burnup occur, the fuel elements are recycled from the bottom of the core and replaced at the top of the core. With each pass the fuel is measured for burnup. If it is below the burnup limit, and has not received significant structural damage, it is recycled. If not, it will be placed directly in dry casks for storage. Because of its inert nature, there is no need for cutting or processing before storage. A fuel element is designed to stay in the core for roughly 3 years.
Both the fuel elements, and core structure material are composed mostly of graphite. This graphite will experience significant property changes based on both the thermal expansion, and the neutron irradiation. These changes include the Young’s modulus, Poisson’s ratio, density and swelling, and coefficient of thermal conductivity. The effects of irradiation on the core structure material, and the resulting core behavior, has been well studied. Previously the effect of dynamic properties of the graphite fuel pebbles due to irradiation has been assumed negligible.
With advances in computing power, it has become feasible to model graphite fuel element property changes and their effect on the core geometry and maximum pebble temperatures. This modelling can be accomplished using the discrete element method (DEM). In this paper the discrete element method is described. Previous research on graphite property changes based on temperature and irradiation dose is summarized. This previous research was used to augment the discrete element method with dynamic graphite pebble properties. The core was simulated over a three-year period with graphite pebble property changes. In this study the forces are examined. It was shown that the dynamic property changes lead to unsafe changes in pebble forces. These estimates are consistent with previous reactors and show that dynamic property changes could be better used to model the PBR core.
