Construction of Dynamic Model of Planar and Rocking Motion for Free Standing Spent Fuel Rack

2017 ◽  
Author(s):  
Kazuya Sakamoto ◽  
Ryosuke Kan ◽  
Akihiro Takai ◽  
Shigehiko Kaneko
Keyword(s):  
Friction Coefficient ◽  
Dynamic Model ◽  
Friction Force ◽  
Spent Nuclear Fuel ◽  
Inertial Force ◽  
Spent Fuel ◽  
Free Standing ◽  
Fluid Force ◽  
Rocking Motion ◽  
Spent Fuel Pool

Spent nuclear fuel is settled in racks and stored in spent fuel pool. A free standing rack (FS rack) is a type of a spent fuel rack, which is not fixed to walls unlike conventional ones. For this characteristic, movement of an FS rack during an earthquake can be reduced by fluid force and friction force. However, 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 FS racks is constructed considering seismic inertial force, friction force and fluid force. This model consists of two sub-models: translation model, which simulates planar translational and rotational motion; and rocking model, which simulates rocking motion. Moreover, we developed two kinds of rocking model: slide-rocking considered model, which considers the equations of both slide-rocking motion and non-slide-rocking motion; and non-slide-rocking model, which considers only the equation of non-slide-rocking motion. Then, simulations with sinusoidal inertial force input were conducted, changing values of friction coefficient. To validate this dynamic model, a miniature experiment was conducted. It is found that the non-slide-rocking model simulates movement of an FS rack well and better than the slide-rocking considered model in the aspect of translational and rocking movement. However, planar rotational movement is not simulated well with either model. Through this research, the knowledge is acquired that friction force plays a significant role in motion of an FS rack so that estimating and controlling friction coefficient is important in designing an FS rack.

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

2017 ◽  
Vol 12 (6) ◽  
Author(s):  
Kazuya Sakamoto ◽  
Ryosuke Kan ◽  
Akihiro Takai ◽  
Shigehiko Kaneko
Keyword(s):  
Friction Coefficient ◽  
Dynamic Model ◽  
Friction Force ◽  
Spent Nuclear Fuel ◽  
Inertial Force ◽  
Seismic Excitation ◽  
Free Standing ◽  
Fluid Force ◽  
Translational Movement ◽  
Rocking Motion

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.

Influence of Gap Size on Added Mass for Spent Fuel Storage Rack

2018 ◽  
Author(s):  
Daogang Lu ◽  
Yu Liu ◽  
Shu Zheng
Keyword(s):  
Vibration Frequency ◽  
Input Parameter ◽  
Added Mass ◽  
Water Tank ◽  
Spent Fuel ◽  
Free Standing ◽  
Fluid Force ◽  
Spent Fuel Storage ◽  
Fuel Storage ◽  
Spent Fuel Pool

Free standing spent fuel storage racks are submerged in water contained with spent fuel pool. During a postulated earthquake, the water surrounding the racks is accelerated and the so-called fluid-structure interaction (FSI) is significantly induced between water, racks and the pool walls[1]. The added mass is an important input parameter for the dynamic structural analysis of the spent fuel storage rack under earthquake[2]. The spent fuel storage rack is different even for the same vendors. Some rack are designed as the honeycomb construction, others are designed as the end-tube-connection construction. Therefore, the added mass for those racks have to be measured for the new rack’s design. More importantly, the added mass is influenced by the layout of the rack in the spent fuel pool. In this paper, an experiment is carried out to measure the added mass by free vibration test. The measured fluid force of the rack is analyzed by Fourier analysis to derive its vibration frequency. The added mass is then evaluated by the vibration frequency in the air and water. Moreover, a two dimensional CFD model of the spent fuel rack immersed in the water tank is built. The fluid force is obtained by a transient analysis with the help of dynamics mesh method.

scholarly journals Temperature conditions in the RBMK spent fuel pool in the event of disturbances in its cooling mode

2021 ◽  
Vol 7 (1) ◽  
pp. 9-13
Author(s):  
David A. Hakobyan ◽  
Victor I. Slobodchuk
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Spent Nuclear Fuel ◽  
Maximum Temperature ◽  
Spent Fuel ◽  
Cooling Mode ◽  
Temperature Conditions ◽  
Fuel Assemblies ◽  
Spent Fuel Pool

The problems of reprocessing and long-term storage of spent nuclear fuel (SNF) at nuclear power plants with RBMK reactors have not been fully resolved so far. For this reason, nuclear power plants are forced to search for new options for the disposal of spent fuel, which can provide at least temporary SNF storage. One of the possible solutions to this problem is to switch to compacted SNF storage in reactor spent fuel pools (SFPs). As the number of spent fuel assemblies (SFAs) in SFPs increases, a greater amount of heat is released. In addition, no less important is the fact that a place for emergency FA discharging should be provided in SFPs. The paper presents the results of a numerical simulation of the temperature conditions in SFPs both for compacted SNF storage and for emergency FA discharging. Several types of disturbances in normal SFP cooling mode are considered, including partial loss of cooling water and exposure of SFAs. The simulation was performed using the ANSYS CFX software tool. Estimates were made of the time for heating water to the boiling point, as well as the time for heating the cladding of the fuel elements to a temperature of 650 °С. The most critical conditions are observed in the emergency FA discharging compartment. The results obtained make it possible to estimate the time that the personnel have to restore normal cooling mode of the spent fuel pool until the maximum temperature for water and spent fuel assemblies is reached.

Air Cooling Temperature Analysis of Spent Fuel

2005 ◽  
Author(s):  
A. L. Laursen ◽  
F. J. Moody ◽  
J. C. Law
Keyword(s):  
Nuclear Reactor ◽  
Spent Nuclear Fuel ◽  
Natural Circulation ◽  
Maximum Temperature ◽  
Air Cooling ◽  
Spent Fuel ◽  
Decay Heat ◽  
Spent Fuel Pool ◽  
Large Water ◽  
The Relationship

Spent nuclear fuel is currently being stored at nuclear reactor sites. The spent fuel removed from the reactor is first placed in a large water pool to remove the initial decay heat. After several years, when the decay heat has dropped below a set level, the fuel is moved into concrete storage casks where natural circulation continues the cooling process. The purpose of this report is to predict, using a simplified analysis, how hot the fuel rods get when cooled by air in the cask. The increase in temperature and the decrease in density cause a chimney effect in the cask. This paper presents an analytical method of obtaining maximum fuel clad temperature in the cask. A non-dimensional model is derived, which is used to calculate the entrance and exit air velocities of the cask. The relationship between these velocities and the temperature used to obtain the maximum fuel clad temperature. A numerical scheme used to predict the maximum temperature is presented here and the results are compared to the analytical model. Both methods yielded corroborating results for fuel placed in the casks after spending similar amounts of time in a spent fuel pool.

Assessment of Free Standing Body in Dry and Submerged Condition and Under Seismic Loading

2019 ◽  
Author(s):  
Beniamino Rovagnati ◽  
Phuong H. Hoang
Keyword(s):  
Three Dimensional ◽  
Nuclear Industry ◽  
Spent Fuel ◽  
Free Standing ◽  
Transient Model ◽  
Dimensional Finite Element ◽  
Rocking Motion ◽  
Free Body ◽  
The Stability ◽  
Three Dimensional Finite Element

Abstract A free standing, slender body may experience rocking motion followed by overturning when it is subject to strong seismic motions. When the free body is submerged in water, it will also be subject to lateral forces acting along the side of the free body as a result of water sloshing. This highly non-linear situation is of particular interest to engineers in the nuclear industry in need to assess the stability of transfer casks containing spent fuel and submerged in a confined pit or pool. In this work, a three-dimensional finite element dynamic transient model of a free standing cask is developed and analyzed using ANSYS. Both dry and submerged conditions are considered. Cask to floor friction, buoyancy force, and sloshing are accounted for in the assessment. The model is validated against well-accepted contributions on sloshing and rocking provided by G.W. Housner.

Development of Seismic Design Method for Free Standing Rack

2013 ◽  
Author(s):  
Akihisa Iwasaki ◽  
Yoshitsugu Nekomoto ◽  
Hideyuki Morita ◽  
Katsuhiko Taniguchi ◽  
Daisaku Okuno ◽  
...  
Keyword(s):  
Seismic Design ◽  
Seismic Analysis ◽  
Design Method ◽  
Spent Fuel ◽  
Free Standing ◽  
Highly Nonlinear ◽  
Spent Fuel Pool ◽  
Vibration Tests ◽  
Seismic Design Method ◽  
Complex Phenomena

For high earthquake resistance and ease of installation, free standing racks which are not anchored to the pool floor or walls has been adopted in many countries. Under the earthquake, the response of the free standing rack is highly nonlinear and involves a complex combination of motions (sliding, rocking, twisting, and turning) and impacts between the fuel assemblies and the fuel cell walls, rack-to-rack, and the pit floor and the rack pedestals. To obtain an accurate simulation of the free standing rack, the seismic analysis requires careful considerations of these complex phenomena (sliding, rocking, twisting, and turning), fluid coupling effects and frictional effects. The important evaluation items while applying the free standing rack to the actual nuclear plants are maximum sliding displacement of the rack, maximum rocking displacement and maximum leg load under earthquake. When the sliding displacement increases, the rack may collide against the spent fuel pool wall. In addition, the free standing rack should not exhibit tilt sufficient to cause to the rack to overturn. The vibration tests were conducted in order to predict the rack behavior under earthquake, and the analysis method was validated by comparison to tests results. Furthermore, we developed the seismic design method to obtain the margin of safety for free standing rack.

Construction of Dynamic Model for Free Standing Spent Fuel Rack Under Seismic Excitations

2015 ◽  
Author(s):  
Shigehiko Kaneko ◽  
Hironao Shirai
Keyword(s):  
Dynamic Model ◽  
Nuclear Power ◽  
Scale Model ◽  
Spent Fuel ◽  
Seismic Excitations ◽  
Power Station ◽  
Free Standing ◽  
Method Of Calculation ◽  
Gap Flow ◽  
Real Size

Free standing rack designed for storing spent fuel at nuclear power station has an advantage to earthquake excitations because both fluid force and friction force can reduce the movement of a rack. However, there are various motions of FS rack such as parallel, rotational and rocking which should be taken into consideration when it is subjected to earthquake excitations. Therefore, the motion of FS rack must be precisely figured out in order to apply FS rack design concept. In this research, to investigate the motion of FS rack, 2-dimensional dynamic model considering pressure loss of gap flow was constructed. In addition, an experiment with a 1/16 scale model was conducted to validate the dynamic model. From numerical results based on the proposed dynamic model, some important features for the design of FS rack were found. Finally, case studies by real size free standing rack under the excitation of actually observed earthquake wave like The Great East Japan earthquake and The Niigata-ken Chuetsu-Oki earthquake were conducted based on the proposed method of calculation.

Fundamental Study on Mitigation of Rocking Motion of a Cask System by a Gyro System

2013 ◽  
Author(s):  
Tomohiro Ito ◽  
Yasumasa Ishikawa ◽  
Atsuhiko Shintani ◽  
Chihiro Nakagawa
Keyword(s):  
Structural Integrity ◽  
Shaking Table ◽  
System Model ◽  
Spent Fuel ◽  
Free Standing ◽  
Fundamental Study ◽  
Worst Case ◽  
Gyro System ◽  
Rocking Motion ◽  
Basic Characteristics

In Japan, ensuring the structural integrity of cask systems during seismic events is becoming increasingly important. Cask systems, which are free-standing cylindrical structures that contain spent fuel assemblies, are believed to exhibit rocking motions under strong seismic excitations. Thus far, analytical studies conducted by the authors have indicated that cask systems subjected to strong seismic motions, undergo large rocking motions, and, in the worst case, may overturn and collapse. Therefore, reducing the rocking motions of casks to avoid overturning and consequent contamination of radioactive substances is critical. To suppress rocking motions for heavy free-standing structures such as cask systems, we propose a rocking motion suppression system that employs a gyro system. This system is installed in the free-standing structure. A previous analytical study showed that this system largely mitigates rocking motion. In the present study, we fabricated a fundamental cask system model and a gyro system. By using the cask system model without a gyro system, free vibration tests and shaking table tests were conducted to understand the basic characteristics of rocking motion and responses under base excitations. Analyses were also conducted to confirm the validity of the analytical model for rocking motion comparing with the experimental data. Moreover, analyses for the cask system with the gyro system were conducted. From these results, we evaluated the ability of the gyro system to mitigate rocking motion.

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