Numerical Experiments of Coolant Mixing in a Lower Plenum of PWR Under Asymmetric Thermal- Hydraulics Conditions

Conference · Sat Jul 01 04:00:00 EDT 2006

OSTI ID:20995481

Ohtani, Masanori ^[1]; Kozuru, Akito ^[2]; Kashimoto, Yasuyuki ^[3]; Montani, Mitsuto ^[4]; Takeda, Koutaro ^[5]; Makino, Yasushi ^[6]

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1. Kansai Electric Power Company, Inc. (Japan)
2. Kyushu Electric Power Company, Inc. (Japan)
3. Shikoku Electric Power Company, Inc. (Japan)
4. Japan Atomic Power Company (Japan)
5. Hokkaido Electric Power Company, Inc. (Japan)
6. Mitsubishi Heavy Industries, Ltd. (Japan)

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. (authors)

• Research Organization: The ASME Foundation, Inc., Three Park Avenue, New York, NY 10016-5990 (United States)
• OSTI ID: 20995481
• Country of Publication: United States
• Language: English

Related Subjects

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
ASYMMETRY
COOLANTS
FLOW RATE
FLUCTUATIONS
MIXING
NATURAL CONVECTION
PWR TYPE REACTORS
REACTIVITY INSERTIONS
REACTOR VESSELS
REYNOLDS NUMBER
STEADY-STATE CONDITIONS
STEAM LINES
TEMPERATURE DISTRIBUTION
THERMAL DIFFUSIVITY
THERMAL HYDRAULICS
TIME DEPENDENCE
VELOCITY