Asymmetric thermal-hydraulic conditions among primary loops during a postulated steam line break (SLB) induce a non-uniform temperature distribution at a core inlet. When coolant of lower temperature intrudes into a part of core, it leads to a reactivity insertion and a local power increase. Therefore, an appropriate model for the core inlet temperature distribution is required for a realistic SLB analysis. In this study, numerical experiments were conducted to examine the core inlet temperature distribution under the asymmetric thermal-hydraulic coolant conditions among primary loops. 3D steady-state calculations were carried out for Japanese standard Pressurized Water Reactor (PWR) such as 2, 3, 4 loop types and an advanced PWR. Since the flow in a reactor vessel involves time-dependent velocity fluctuations due to a high Reynolds number condition and a complicated geometry of flow path, the turbulent mixing might be enhanced. Hence, the turbulent thermal diffusivity for the steady-state calculation was examined based on experimental results and another transient calculation. As a result, it was confirmed that (1) the turbulent mixing in a downcomer and a lower plenum were enhanced due to time-dependent velocity fluctuations and therefore the turbulent thermal diffusivity for steady-state calculation was specified to be greater, (2) the core inlet temperature distribution predicted by a steady-state calculation reasonably agreed with a experimental data, (3) the patterns of core inlet temperature distribution were comprehended to be dependent on the plant type, i.e. the number of primary loop and (4) under a low flow rate condition, the coolant of lower temperature appeared on the opposite side of the affected loop due to the effect of a natural convection.
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14th International Conference on Nuclear Engineering
July 17–20, 2006
Miami, Florida, USA
Conference Sponsors:
- Nuclear Engineering Division
ISBN:
0-7918-4245-2
PROCEEDINGS PAPER
Numerical Experiments of Coolant Mixing in a Lower Plenum of PWR Under Asymmetric Thermal- Hydraulics Conditions
Masanori Ohtani,
Masanori Ohtani
Kansai Electric Power Company, Inc., Fukui, Japan
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Akito Kozuru,
Akito Kozuru
Kyushu Electric Power Company, Inc., Fukuoka, Japan
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Yasuyuki Kashimoto,
Yasuyuki Kashimoto
Shikoku Electric Power Company, Inc., Takamatsu, Japan
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Mitsuto Montani,
Mitsuto Montani
Japan Atomic Power Company, Tokyo, Japan
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Koutaro Takeda,
Koutaro Takeda
Hokkaido Electric Power Company, Inc., Sapporo, Japan
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Yasushi Makino
Yasushi Makino
Mitsubishi Heavy Industries, Ltd., Yokohama, Japan
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Masanori Ohtani
Kansai Electric Power Company, Inc., Fukui, Japan
Akito Kozuru
Kyushu Electric Power Company, Inc., Fukuoka, Japan
Yasuyuki Kashimoto
Shikoku Electric Power Company, Inc., Takamatsu, Japan
Mitsuto Montani
Japan Atomic Power Company, Tokyo, Japan
Koutaro Takeda
Hokkaido Electric Power Company, Inc., Sapporo, Japan
Yasushi Makino
Mitsubishi Heavy Industries, Ltd., Yokohama, Japan
Paper No:
ICONE14-89447, pp. 209-215; 7 pages
Published Online:
September 17, 2008
Citation
Ohtani, M, Kozuru, A, Kashimoto, Y, Montani, M, Takeda, K, & Makino, Y. "Numerical Experiments of Coolant Mixing in a Lower Plenum of PWR Under Asymmetric Thermal- Hydraulics Conditions." Proceedings of the 14th International Conference on Nuclear Engineering. Volume 4: Computational Fluid Dynamics, Neutronics Methods and Coupled Codes; Student Paper Competition. Miami, Florida, USA. July 17–20, 2006. pp. 209-215. ASME. https://doi.org/10.1115/ICONE14-89447
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