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Division Spotlight
Thermal Hydraulics
The division provides a forum for focused technical dialogue on thermal hydraulic technology in the nuclear industry. Specifically, this will include heat transfer and fluid mechanics involved in the utilization of nuclear energy. It is intended to attract the highest quality of theoretical and experimental work to ANS, including research on basic phenomena and application to nuclear system design.
Meeting Spotlight
International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering (M&C 2025)
April 27–30, 2025
Denver, CO|The Westin Denver Downtown
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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May 2025
Latest News
Ariz. governor vetoes “fast track” bill for nuclear
Gov. Katie Hobbs put the brakes on legislation that would have eliminated some of Arizona’s regulations and oversight of small modular reactors, technology that is largely under consideration by data centers and heavy industrial power users.
U. Hansen, E. Teuchert
Nuclear Science and Engineering | Volume 44 | Number 1 | April 1971 | Pages 12-17
Technical Paper | doi.org/10.13182/NSE44-12
Articles are hosted by Taylor and Francis Online.
The heterogeneity due to lumping the fuel in coated particles affects the thermal-neutron spectrum. A calculational model is discussed which, apart from some simplifying assumptions about the statistical distribution, allows a rigorous computation of effective cross sections for all nuclides of the heterogeneous medium. It is based on an exact computation of the neutron-penetration probability through coating and kernel. The model is incorporated in a THERMOS code providing a double heterogeneous cell calculation that can be repeated automatically at different time steps in the depletion code system MAFIA-V.S.O.P. A discussion of the effects of the coated-particle structure is given by a comparison of calculations for heterogeneous and homogeneous fuel zones in pebble bed reactor elements. This is performed for enriched UO2 fuel and for a ThO2-PuO2 mixture in the grains. Depending on the energy-dependent total sigmas in the kernels, the changes of the cross sections range from 0.1 up to 45%. The influence on the spectrum-averaged sigmas of the nuclides in the fresh UO2 fuel is lower than 1%. For the emerging 240Pu it increases up to 3.3% during irradiation. For the ThO2-PuO2 fuel, the averaged sigmas of the isotopes vary from 0.5 to 5.7% depending on the state of irradiation. Correspondingly, there is an influence on the plutonium isotopic composition, on breeding ratios, and on the tilt of keff during burnup which will be discussed in detail.
