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Research Papers

Dynamic Model for Free-Standing Fuel Racks Under Seismic Excitation Considering Planar and Nonslide Rocking Motion

[+] Author and Article Information
Kazuya Sakamoto

Department of Mechanical Engineering,
The University of Tokyo,
7-3-1 Bunkyo-ku, Hongo,
Tokyo 113-8656, Japan
e-mail: ksakamoto@fiv.t.u-tokyo.ac.jp

Ryosuke Kan

Department of Mechanical Engineering,
The University of Tokyo,
7-3-1 Bunkyo-ku, Hongo,
Tokyo 113-8656, Japan
e-mail: rkan@iis.u-tokyo.ac.jp

Akihiro Takai

Department of Mechanical Engineering,
The University of Tokyo,
7-3-1 Bunkyo-ku, Hongo,
Tokyo 113-8656, Japan
e-mail: atakai@fiv.t.u-tokyo.ac.jp

Shigehiko Kaneko

Mem. ASME
Department of Mechanical Engineering,
The University of Tokyo,
7-3-1 Bunkyo-ku, Hongo,
Tokyo 113-8656, Japan
e-mail: kaneko@mech.t.u-tokyo.ac.jp

Contributed by the Design Engineering Division of ASME for publication in the JOURNAL OF COMPUTATIONAL AND NONLINEAR DYNAMICS. Manuscript received November 30, 2016; final manuscript received February 11, 2017; published online September 7, 2017. Assoc. Editor: Stefano Lenci.

J. Comput. Nonlinear Dynam 12(6), 061012 (Sep 07, 2017) (9 pages) Paper No: CND-16-1591; doi: 10.1115/1.4036115 History: Received November 30, 2016; Revised February 11, 2017

A free-standing (FS) rack is a type of a spent nuclear fuel rack, which is just placed on a floor of a pool. For this characteristic, seismic loads can be reduced by fluid force and friction force, but a collision between a rack and another rack or a wall must be avoided. Therefore, it is necessary for designing an FS rack to figure out how it moves under seismic excitation. In this research, a dynamic model of an FS rack is developed considering seismic inertial force, friction force, and fluid force. This model consists of two submodels: a translation model, which simulates planar translational and rotational motion, and a rocking model, which simulates nonslide rocking motion. First, simulations with sinusoidal inertial force were conducted, changing values of a friction coefficient. Next, to validate this dynamic model, a miniature experiment was conducted. Finally, the model is applied to a real-size FS rack and actually observed seismic acceleration. It is found that translational movement of a rack varies depending on the value of friction coefficient in the simulation with sinusoidal and actual acceleration. Also, simulation results are similar to the experimental results in the aspects of translational and rocking motion provided friction coefficient is selected properly. Through this research, the knowledge is acquired that friction force plays a significant role in a motion of FS rack so that estimating and controlling a friction coefficient is important in designing an FS rack.

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Figures

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Fig. 1

Fixed rack (a) and free-standing rack (b). The rack is placed in a spent fuel pool, which is filled with water.

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Fig. 2

Two submodels composing the model developed in this research

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Fig. 3

Coordinates of FS racks

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Fig. 4

Coordinates of clearance-flow

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Fig. 5

Coordinates of rocking motion (a) side view and (b) top view

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Fig. 6

Flowchart of integrated model

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Fig. 7

Experimental equipment

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Fig. 8

Comparison with experiment and simulation results when excitation frequency is 8 Hz. (a) Displacement X, (b) planar rotation θ, and (c) rocking angle ϕ. Simulation results are delayed 0.8 s to adjust start time of movement. Note that five lines of simulation data completely lap over with each other in (b).

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Fig. 9

Simulation results when excitation frequency is 10 Hz

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Fig. 10

Simulated fluid force versus translational acceleration X¨: (a) f=10,μk= 0.3 and (b) f=10,μk=0.6

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Fig. 11

Seismic acceleration actually observed in Japan during The 2011 Off the Pacific Coast of Tohoku Earthquake

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Fig. 12

Simulation results of displacement of a rack under actual seismic excitation. Square markers mean the maximal displacement of each friction coefficient.

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