JP2016156716A - Spent fuel rack, nuclear power plant, and operation method of spent fuel rack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spent fuel rack, a nuclear power plant, and an operation method of the spent fuel rack, which can reduce earthquake response even to large earthquake input so as to increase reliability of earthquake resistance.SOLUTION: A dynamic vibration absorber 4 is installed in each cell 8 of a spent fuel rack 1 in order to reduce earthquake responce of the spent fuel rack 1 installed in a spent fuel pool 2. The dynamic vibration absorber 4 is a cantilever type in order to be able to be inserted into and pulled out from the arbitrary cell 8 of the spent fuel rack 1.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a highly earthquake-resistant spent fuel rack and nuclear power plant capable of ensuring further earthquake-resistant soundness and a method for operating a spent fuel rack.

  There is a spent fuel pool in the reactor building of the nuclear power plant that stores spent fuel taken out of the pressure vessel, and a spent fuel rack that stores spent fuel at the bottom of the spent fuel pool. Is placed. In order to effectively use the spent fuel pool, the fuel racks are densely arranged with a narrow gap.

  This fuel rack has a structure in which dozens of square tubes called cells for storing spent fuel are bundled, and the cross-sectional shape of the entire fuel rack is square or rectangular. The bottom of the fuel rack is bolted to the foundation of the fuel pool. The fuel pool is filled with water and the fuel rack is submerged.

  In recent years, huge earthquakes have occurred frequently, and it is an important issue to further ensure the seismic safety of nuclear power plants. Since the fuel pool described above is on the upper floor of the reactor building, the seismic acceleration applied to the fuel rack due to the vibration amplification of the building becomes larger. In particular, when fuel is stored in all the cells of the fuel rack, the mass of the fuel rack itself is the largest, and therefore, stress on the lower portion of the fuel rack and bolts may increase when subjected to a large earthquake acceleration.

  The following documents can be cited as techniques for this.

  A technique for improving the earthquake resistance by supporting the fuel rack with a damper is disclosed in Patent Document 1. In Patent Document 1, a spent fuel pool is provided with a spent fuel rack having a plurality of cells into which spent fuel can be inserted from above along the vertical direction, and a lower portion fixed to the bottom of the spent fuel pool. A damper device is provided between the wall surface and the side surface of the spent fuel rack.

  In Patent Document 2, a cell storage unit in which spent fuel can be inserted from above along the vertical direction is configured to be placed in a spent fuel pool by a plurality of legs, and a plurality of adjacent spent fuel A technique for connecting fuel racks with a plurality of damper devices is shown.

  Patent Document 3 discloses a storage structure for storing a stored item in a liquid in a storage container, and a plurality of stored items for storing the stored item are fixed on a sliding frame. In addition, a biasing means is provided between the side surface of the sliding frame and the inner wall surface of the storage container, and a flat plate configured to swing around the upper end portion is provided on each side surface of the stored item. The installed technology is shown.

  Further, Patent Document 4 includes a base body for storing a large number of rack cells in which fuel assemblies are stored, a rack main body composed of a cell storage, and a plurality of rack legs for supporting the rack main body, and is provided in the storage pit. In the spent fuel storage racks arranged in line with each other, the rack legs support the rack body so as to be slidable with respect to the floor surface of the storage pit, and at least one fuel assembly has elasticity in the vertical direction. The lower elastic member and the upper elastic member are supported by the rack main body, and the rigidity of the lower elastic member and the upper elastic member is such that the natural frequency of the fuel assembly matches the natural frequency due to the locking of the rack main body. The technology that is to be adjusted is shown.

2013-104738 2013-127432 gazette 2011-095043 2013-156044

  As described in Patent Documents 1-4 above, there is a method for reducing a seismic load by providing a damper between a fuel rack and a fuel pool side wall, connecting fuel racks together, or installing a dynamic vibration absorber. Proposed.

  However, in Patent Document 1, it is necessary to fix the damper to the side wall of the fuel pool, and the building is remodeled. In Patent Document 2, it is difficult to install a damper between fuel racks in consideration of an actual gap between fuel racks. In addition, a cutout portion that opens upward is provided in the outer frame portion of the fuel rack for mounting the damper, and is configured to be attached to and detached from the fitting portion provided at the end portion of the damper. Since there is not enough plate thickness to provide a notch in the part, it is difficult to implement. Further, in Patent Document 3, since the vibration damping device made of a flat plate is installed so as to swing around the upper end portion of the outer surface of the fuel rack, the vibration damping device made of a flat plate is installed between narrow fuel racks. It is difficult. Further, in Patent Document 4, the object to be controlled is rocking vibration of a free-standing rack that does not fix the lower part of the rack, the vibration control direction is the vertical direction, the horizontal direction is not considered, and the horizontal direction It is difficult to cope with when an earthquake load is added to the.

  As described above, in the techniques described in Patent Documents 1 to 4, when the seismic load increases, there is a possibility that the stress of the lower part of the spent fuel rack or the bolt to which the bottom part is fixed and the bolt may be increased. There is a point. For this reason, it is required to further reduce the seismic response of the spent fuel rack in order to ensure further seismic reliability.

  The present invention provides a spent fuel rack, a nuclear power plant, and a method for operating a spent fuel rack that can reduce seismic response even with a large earthquake input and can increase seismic reliability.

In order to solve the above problems, for example, the configuration described in the claims is adopted.
The present invention includes a plurality of means for solving the above-mentioned problems. To give an example, the present invention is a spent fuel rack configured in a rectangular shape by a plurality of cells into which spent fuel can be inserted and removed from above. A dynamic vibration absorber configured to be able to be inserted into and removed from an arbitrary cell among the plurality of cells of the spent fuel rack. The dynamic vibration absorber has an outer frame and one end with respect to the outer frame. A fixed beam and a tip mass provided at an end of the beam opposite to the one end that is fixed to the outer frame so as not to contact the outer frame.

  According to the present invention, the seismic response of the spent fuel rack can be reduced even with a large seismic input, and seismic reliability can be increased.

It is a figure which shows an example of the outline | summary of the nuclear power plant in Example 1 of this invention. It is a top view of the highly earthquake-resistant spent fuel rack which installed the cantilever type dynamic vibration damper which can be attached in the cell of the spent fuel rack in Example 1 of this invention. It is a side view of the highly earthquake-resistant spent fuel rack which installed the cantilever type dynamic vibration damper which can be attached in the cell of the spent fuel rack in Example 1 of this invention. It is a side view of the cantilever type dynamic vibration absorber in Example 1 of the present invention. It is a top view of the highly earthquake-resistant spent fuel rack which installed the cantilever type dynamic vibration damper which can be attached in the cell of the spent fuel rack in Example 2 of this invention. It is another top view of the highly earthquake-resistant spent fuel rack which installed the cantilever type dynamic vibration damper which can be attached in the cell of the spent fuel rack in Example 2 of this invention.

  Embodiments of a spent fuel rack, a nuclear power plant, and a spent fuel rack operating method according to the present invention will be described below with reference to the drawings.

<Example 1>
A spent fuel rack, a nuclear power plant, and a spent fuel rack operating method according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 4. Here, for simplicity, the case where four fuel racks are placed in the spent fuel pool 2 will be described.

  FIG. 1 is a schematic configuration diagram of a nuclear power plant according to the present invention. FIG. 2 is a top view when the fuel rack is placed in the spent fuel pool. FIG. 3 is a side view when the fuel rack is placed in the spent fuel pool. FIG. 4 shows a side view of a cantilever type dynamic vibration absorber.

  In FIG. 1, the boiling water nuclear power plant 21 is mainly composed of a reactor building 22 and a turbine building 23.

  A reactor pressure vessel 24 (hereinafter referred to as a pressure vessel 24) exists in the center of the reactor building 22, and the pressure vessel 24 is covered with a reactor containment vessel 25.

  A turbine 26 is provided inside the turbine building 23, and a generator 27 is rotated by the rotation of the turbine 26. A condenser 28 is provided below the turbine 26.

  The pressure vessel 24 and the vicinity of the turbine 26 are connected by a main steam pipe 29. The pressure vessel 24 and the condenser 28 are connected by a return pipe 30. A seawater circulation pipe 31 is attached to the condenser 28 in order to circulate seawater. After the seawater is taken in from the intake 31a and circulated through the condenser 28, it is returned to the sea from the sprinkler 31b.

  The spent fuel pool 2 is provided on the upper side of the reactor containment vessel 25.

  That is, the boiling water nuclear power plant 21 uses the high temperature generated when the uranium fuel undergoes fission in the pressure vessel 24 to boil water, and steam generated by the boiling is generated in the turbine building 23 through the main steam pipe 30. The turbine is fed into the turbine 26 to rotate the turbine. A generator 27 is rotated by a rotating turbine 26 to generate power.

  The steam used for the rotation of the turbine 26 is condensed by returning to the water by being cooled by the condenser 28, and returned to the pressure vessel 24 by the return pipe 29 to be used as steam.

  Now, uranium fuel used in the pressure vessel 24 is replaced as spent fuel in about four years. However, uranium fuel can be reused as uranium fuel by regenerating. Therefore, spent uranium fuel rods (hereinafter referred to as spent fuel rods) are stored in the spent fuel pool 2 for about 2 to 5 years.

  2 and 3, a plurality of (four in this embodiment) spent fuel racks 1 that are rectangularly formed by a plurality of cells 8 into which spent fuel can be inserted and removed from above are surrounded by side walls 3. The spent fuel pool 2 is fixed to the bottom (base) 3a of the spent fuel pool 2 with bolts 3b and the like, and stored in the spent fuel pool 2. The spent fuel pool 2 is filled with cooling water, and the plurality of spent fuel racks 1 are disposed so as to be completely submerged in water.

  The spent fuel rack 1 is configured by arranging a plurality of cells 8 in the vertical and horizontal directions (the horizontal and vertical directions in FIG. 2). In the spent fuel rack 1 of the present embodiment, for example, 10 cells 8 are arranged in the horizontal direction (left-right direction in FIG. 2) and 6 cells 8 are arranged in the vertical direction (up-down direction in FIG. 2). The case will be described. The number of cells 8 used in the spent fuel rack 1 is not limited to the above, and is appropriately selected according to the installation environment of the spent fuel rack 1 such as the shape and size of the spent fuel pool 2. .

  As shown in FIG. 4, the cantilever type dynamic vibration absorber 4 installed in the cells 8 at the four corners of the spent fuel rack 1 in FIG. 2 includes an outer frame 7 and the outer frame 7. A fixed horizontal plate 9, a support beam 5 fixed to the outer frame 7 by fixing one end to the horizontal plate 9, and a horizontal plate 9 of the support beam 5 so as not to contact the outer frame 7 It is comprised from the front-end | tip mass 6 provided in the edge part on the opposite side to the fixed one end. The dynamic vibration absorber 4 has substantially the same height as the spent fuel rack 1 and does not protrude from the upper end of the spent fuel rack 1.

  This cantilever type dynamic vibration absorber 4 can be inserted into an arbitrary cell 8 in the spent fuel rack 1, or can be pulled out from the inserted cell 8 and transferred to another cell 8. It has a structure.

  The cross section of the support beam 5 is rectangular as shown in FIG. 2, and the rigidity differs between the direction of the long side 5b and the direction of the short side 5a. Similarly, the spent fuel rack 1 is also rectangular and has different natural frequencies in the direction of the long side 1b and the direction of the short side 1a. The natural frequency in the direction of the long side 5b of the support beam 5 of the cantilever type dynamic vibration absorber 4 is synchronized with the natural frequency in the direction of the long side 1b of the spent fuel rack 1, and the short side 5a of the support beam 5 is The natural frequency in the direction is tuned to the natural frequency in the direction of the short side 1 a of the spent fuel rack 1. Thereby, it is possible to more efficiently dampen both the long side direction and the short side direction of the spent fuel rack 1.

  Furthermore, in order to make the dynamic vibration absorber 4 work most effectively, it is desirable to synchronize the natural frequency of the dynamic vibration absorber 4 with the natural frequency of the spent fuel rack 1. That is, the spent fuel rack 1 has the largest seismic load when the spent fuel is filled in all the cells 8, and the stress generated at the lower part of the spent fuel rack 1 and the bolt 3b becomes severe. Therefore, the natural frequency of the dynamic vibration absorber 4 is synchronized with the natural frequency of the spent fuel rack 1 when the spent fuel including the dynamic vibration absorber 4 is filled in all the cells 8. It is desirable to set.

Here, since the spent fuel rack 1 and the cantilever type dynamic vibration absorber 4 are in water, the spent fuel rack 1 and the cantilever type dynamic vibration absorber 4 need to consider the additional mass of water. . The cross section of the tip mass 6 of the spent fuel rack 1 and the cantilever type dynamic vibration absorber 4 is rectangular or square, and the additional mass M ₁ of the spent fuel rack ₁ and the tip of the cantilever type dynamic vibration absorber 4 The additional mass m ₁ of mass 6 is given by the following equation.

Here, ρ: density of water M: mass of the spent fuel rack 1 (a state where the maximum number of spent fuel is inserted into the cell 8 of the spent fuel rack 1)
m: Mass of the dynamic vibration absorber 4 a ₁ : Side length orthogonal to the vibration direction of the rack cross section b ₁ : Constant determined by the ratio of the vibration direction of the rack cross section and the side length orthogonal to the vibration direction L ₁ : Rack height A ₂ : Side length orthogonal to the vibration direction of the cross section of the tip mass b ₂ : Constant determined by the ratio of the vibration direction of the cross section of the tip mass and the side length orthogonal to the vibration direction L ₂ : Length of the tip mass.

  When the mass ratio between the spent fuel rack 1 and the cantilever type dynamic vibration absorber 4 is μ, μ can be obtained by the following equation (3).

  Here, the optimum tuning condition is as shown in the following equation (4):

となる。

It becomes.

The optimum damping ratio ζ _opt of the dynamic vibration absorber 4 is

となる。

It becomes.

here,
K ₁ : Rigidity in the short side direction of the fuel rack K ₂ : Rigidity in the long side direction of the fuel rack k ₁ : Rigidity in the short side direction of the beam of the dynamic vibration absorber k ₂ : Rigidity in the long side direction of the beam of the dynamic vibration absorber c ₁ : Damping coefficient in the short side direction of the dynamic vibration absorber beam c ₂ : Damping coefficient in the long side direction of the dynamic vibration absorber beam Ω _n : n-order natural frequency of the fuel rack ω _n : n-order vibration dynamic vibration absorber Natural frequency ζ _n : n-order vibration mode damping ratio of the dynamic vibration absorber.

Of these, Ω _n is obtained by equation (6), ω _n is obtained by equation (7), and ζ _n is obtained by equation (8).

  Therefore, it is desirable to set the natural frequency of the dynamic vibration absorber 4 so as to satisfy the optimum tuning condition shown in the equation (4). It is difficult to set the damping ratio of the dynamic vibration absorber 4 to the optimum damping ratio, and the damping ratio is due to viscous damping due to being in water.

  Here, since the mass ratio between the spent fuel rack 1 and the dynamic vibration absorber 4 needs to be about 5%, if this value cannot be satisfied by one mass of the dynamic vibration absorber 4, a plurality of dynamic vibration absorbers are used. 4 is required.

  When the spent fuel enters the cell 8 of the spent fuel rack 1 so as to be symmetrical with respect to the central axis in the long side direction and the short side direction, the vibration mode of the spent fuel rack 1 is the long side. The mode swings in the 1b direction or the short side 1a direction, and the torsional vibration mode does not occur. Therefore, in order to make the dynamic vibration absorber 4 work effectively, the vibration mode of the spent fuel rack 1 needs to be a mode that can swing in the long side 1b direction or the short side 1a direction. When used, it is desirable to arrange the dynamic vibration absorber 4 symmetrically with respect to the central axis in the long side direction and the short side direction of the spent fuel rack 1. FIGS. 2 and 3 show an example in which the number of necessary dynamic vibration absorbers 4 is four and the four dynamic vibration absorbers 4 are arranged at the four corners of the spent fuel rack 1.

  Next, the effect of the present embodiment will be described.

  As described above, in this embodiment, the dynamic vibration absorber 4 is installed in each cell 8 of the spent fuel rack 1 in order to reduce the seismic response of the spent fuel rack 1. The dynamic vibration absorber 4 is a cantilever type so that it can be inserted into and extracted from an arbitrary cell 8 of the spent fuel rack 1.

  Therefore, since the earthquake response can be reduced even for a large earthquake input, the stress generated in the lower part of the fuel rack 1 and the bolt 3b with the bottom fixed can be reduced, and the earthquake resistance can be increased. effective. In addition, it is possible to cope with the need for modification of the spent fuel rack 1 and the fuel pool 2, the thickness of the spent fuel rack 1, the distance between the spent fuel racks 1, and the structure of the spent fuel pool 2. In spite of this, it is possible to easily improve the earthquake resistance of the spent fuel rack 1 without incurring a large expense.

  Further, the cross-sectional shape of the support beam 5 is rectangular, and the natural frequency in the two horizontal directions of the dynamic vibration absorber 4 is synchronized with the natural frequency in the horizontal direction of the long side 1b and the short side 1a of the spent fuel rack 1. As a result, vibrations in the two horizontal directions of the long side 1b and the short side 1a of the spent fuel rack 1 can be more efficiently reduced, and the seismic reliability can be more reliably increased.

<Example 2>
Embodiment 2 of the spent fuel rack and the spent fuel rack operation method of the present invention will be described with reference to FIGS. The same components as those in FIGS. 1 to 4 are denoted by the same reference numerals, and description thereof is omitted. The same applies to the following embodiments.

  FIGS. 5 and 6 are top views when four fuel racks 1 of another embodiment for carrying out the present invention are placed in the spent fuel pool 2.

  In the case where the number of the dynamic vibration absorbers is four, as shown in FIGS. 5 and 6, the long side 1 b direction and the short side 1 a direction of the spent fuel rack 1 are not the four corners of the spent fuel rack 1. The dynamic vibration absorber 4 can be arranged so as to be symmetric with respect to the central axis.

  As described above, the above-described spent fuel rack and spent fuel can also be arranged by arranging the dynamic vibration absorber 4 so as to be symmetric with respect to the central axis in the long side 1b direction and the short side 1a direction of the spent fuel rack 1. The same effects as those in the first embodiment of the rack operation method can be obtained.

  Even if the number of the dynamic vibration absorbers 4 is two or four or more, the same effect can be obtained by arranging the dynamic vibration absorbers 4 in the same way as described above.

<Example 3>
Embodiment 3 of the spent fuel rack and the spent fuel rack operation method of the present invention will be described.

  As described in the first embodiment, as the spent fuel rack 1 has a larger number of stored spent fuels, the mass of the spent fuel rack 1 as a whole increases. Therefore, the greater the mass, the greater the load when subjected to seismic inertial force. When the lower part of the spent fuel rack 1 is fixed, the stress on the lower part of the spent fuel rack 1 and the bolt 3b becomes severe.

  In the case where the vibration in the horizontal direction of the spent fuel rack 1 is damped using the dynamic vibration absorber 4 as described in the above-described embodiment, the natural vibration of the dynamic vibration absorber 4 is increased to the natural frequency of the spent fuel rack 1. Although it is desirable to synchronize the numbers, the natural frequency of the spent fuel rack 1 differs depending on the number of spent fuels stored in the spent fuel rack 1.

  For this reason, when the dynamic vibration absorber 4 is used, it is desirable that the number of spent fuels stored in one spent fuel rack 1 be the same as much as possible regardless of the state.

  Here, since the stress of the lower part of the spent fuel rack 1 and the bolt 3b becomes severer when the number of stored spent fuel is larger, the maximum number of spent fuel including the dynamic vibration absorber 4 is used as much as possible. The fuel rack 1 is used for storage.

  In addition, as described above, the spent fuel and the dynamic vibration absorber 4 are arranged in the long side direction so that the vibration mode of the spent fuel rack 1 is clearly divided into the long side direction and the short side direction and the torsional vibration mode does not occur. It is desirable to arrange so that it becomes object with respect to the central axis of a short side direction.

  In consideration of these matters, when storing spent fuel using a plurality of spent fuel racks 1, the spent fuel is managed to be stored in the spent fuel rack 1 as much as possible, and surplus spent fuel is stored. It is desirable to operate so that a small amount is stored in another spent fuel rack 1. That is, as much spent fuel as possible is inserted into a certain spent fuel rack 1 without evenly arranging the spent fuel in the plurality of spent fuel racks 1 and all the cells 8 are filled, the next spent spent. The spent fuel is stored so that the spent fuel is inserted into the cell 8 of the fuel rack 1.

  In the spent fuel rack 1 in which the number of spent fuels to be stored is small, the dynamic vibration absorber 4 is not always necessary because the load caused by the earthquake is small.

  In the third embodiment of the spent fuel rack and the spent fuel rack operation method of the present invention, the same effects as those of the spent fuel rack and the spent fuel rack operation method described above in the first embodiment can be obtained.

  Further, the spent fuel is not evenly arranged in the plurality of spent fuel racks 1, and after the maximum number of spent fuels is inserted into the spent fuel rack 1, the spent fuel is used in the cell 8 of the next spent fuel rack 1. By storing the spent fuel so as to insert the fuel, the seismic response can be reduced even for a large seismic input, and the seismic reliability can be increased while maximizing the effect of the dynamic vibration absorber 4.

<Others>
In addition, this invention is not limited to said Example, Various modifications are included. The above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of a certain embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of a certain embodiment. Moreover, it is also possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

  For example, in the first and second embodiments, the case where the number of cells of the spent fuel rack is an even number in the long side direction and the short side direction has been described. However, even if the number of cells is an odd number, the long side of the spent fuel rack 1 is It is desirable to insert / remove the dynamic vibration absorber 4 so as to be symmetric with respect to the central axis in the 1b direction and symmetrical with respect to the central axis in the direction of the short side 1a.

  Even if the spent fuel rack is square, the natural frequency of the side of the support beam 5 is tuned to the natural frequency of the side of the spent fuel rack 1 as in the case of the first and second embodiments. In addition, it is desirable to insert / remove the dynamic vibration absorber 4 so as to be axially symmetric with respect to the central axis of each side of the spent fuel rack 1.

1 ... spent fuel rack,
1a: The short side of the spent fuel rack,
1b: long side of spent fuel rack,
2 ... spent fuel pool,
3 ... Fuel pool side wall,
3a ... bottom (basic),
3b ... bolts,
4 ... Cantilever type dynamic vibration absorber,
5 ... Support beam,
5a ... The short side of the beam,
5b ... Long side of beam,
6 ... tip mass,
7 ... Outer frame,
8 ... cell,
9 ... Horizontal plate,
21 ... Boiling water nuclear power plant.

Claims (9)

A spent fuel rack configured in a rectangular shape by a plurality of cells into which spent fuel can be inserted and removed from above,
A dynamic vibration absorber configured to be inserted / removed into / from an arbitrary cell among the plurality of cells of the spent fuel rack;
The dynamic vibration absorber includes an outer frame, a beam having one end fixed to the outer frame, and an end opposite to the one end fixed to the outer frame so as not to contact the outer frame. A spent fuel rack characterized by having a tip mass provided in the section. The spent fuel rack according to claim 1,
When the spent fuel rack is rectangular, the horizontal section of the beam is rectangular. The spent fuel rack according to claim 2,
The natural frequency in the long side direction of the beam is tuned to the natural frequency in the long side direction of the spent fuel rack, and the natural frequency in the short side direction of the beam is adjusted to the natural frequency in the short side direction of the spent fuel rack. A spent fuel rack that is tuned to the frequency. The spent fuel rack according to claim 1,
The spent fuel rack, wherein the dynamic vibration absorber is inserted and removed so that the spent fuel is symmetrical with respect to a central axis of each side of the spent fuel rack. The spent fuel rack according to claim 1,
The spent fuel rack, wherein a natural frequency of the beam is tuned to a natural frequency in a state where a maximum number of the spent fuel is inserted into the cell of the spent fuel rack. A nuclear power plant comprising the spent fuel rack according to claim 1. A method for operating a spent fuel rack configured in a rectangular shape by a plurality of cells in which spent fuel can be inserted and removed from above,
The dynamic vibration absorber includes an outer frame, a beam having one end fixed to the outer frame, and an end portion of the beam opposite to the one end fixed to the outer frame so as not to contact the outer frame. A method for operating a spent fuel rack, comprising: inserting and removing a dynamic vibration absorber having a tip mass provided in a plurality of cells of the spent fuel rack into an arbitrary cell. The method for operating a spent fuel rack according to claim 7,
A method of operating a spent fuel rack, wherein the natural frequency of the beam is tuned to a natural frequency of a state in which a maximum number of the spent fuel is inserted into the cell of the spent fuel rack. The method for operating a spent fuel rack according to claim 8,
When storing the spent fuel by using a plurality of the spent fuel racks, a maximum number of spent fuel is not disposed in the spent fuel racks evenly. A method for operating a spent fuel rack, comprising inserting spent fuel into the next spent fuel rack after inserting

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