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Conference Spotlight
2025 ANS Winter Conference & Expo
November 9–12, 2025
Washington, DC|Washington Hilton
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A webinar, and a new opportunity to take ANS’s CNP Exam
Applications are now open for the fall 2025 testing period for the American Nuclear Society’s Certified Nuclear Professional (CNP) exam. Applications are being accepted through October 14, and only three testing sessions are offered per year, so it is important to apply soon. The test will be administered from November 12 through December 16. To check eligibility and schedule your exam, click here.
In addition, taking place tomorrow (September 19) from 12:00 noon to 1:00 p.m. (CDT), ANS will host a new webinar, “How to Become a Certified Nuclear Professional.” More information is available below in this article.
Jonas Berger, Alexander Mühle, Kai-Martin Haendel
Nuclear Science and Engineering | Volume 194 | Number 6 | June 2020 | Pages 415-421
Technical Paper | doi.org/10.1080/00295639.2019.1705656
Articles are hosted by Taylor and Francis Online.
During the lifetime of fuel assemblies, irradiation and fluid mechanical forces can cause a permanent deformation in the lateral direction that leads to larger interassembly water gaps in the reactor core. The standard reload safety analysis for the reactor core is developed for a uniform distribution of corewise interassembly water gaps. A nonuniform distribution of water gaps with locally larger or smaller water gaps could lead to a significant change in the positions of the hot-spot factors. Thus, such modifications could also impact boundary conditions for safety analysis or boundary conditions of the reactor core surveillance systems. To analyze the impact of a nonuniform water-gap distribution on the safety analysis and the reactor core surveillance systems, TÜV Nord EnSys is developing a new methodology that allows the incorporation of assembly bow effects in core analysis. For this methodology, functions linking the maximal relative power increase in the vicinity of the modified water gap to the fuel properties had to be derived. This was accomplished by simulating for gaps between different fuel types at selected positions in a full-core model of a generic four-loop Siemens/Kraftwerk Union pressurized water reactor using the bow model of the two-group diffusion code SIMULATE-3. The data of the maximal relative power increase were linearly correlated with the spectral indices and the coolant densities of the two gap-adjacent assemblies. Then a function was derived that provides a firsthand approximation of the maximal relative power increase using only the physical properties of the unbowed core configuration. The maximal absolute positive deviation of the function from the simulation results was 2.4%.