JP2017150880A - Spent fuel storage rack - Google Patents

Abstract

To prevent damage to concrete at the bottom of a pool and spent fuel storage racks themselves due to spent fuel storage racks during an earthquake. SOLUTION: A plurality of lattice-shaped cells 4 in which a spent fuel assembly 1 is accommodated, and a casing-like base member provided on a bottom surface 5 of a spent fuel pool 3 provided at a lower portion of the cells. And a preload adjusting member 8 for applying a preload to the side plate 6A or the bottom plate 6B of the base member. [Selection] Figure 2

Description

  Embodiments of the present invention relate to a spent fuel storage rack installed in a spent fuel pool of a nuclear power plant.

  In a nuclear power plant, a spent fuel assembly that has been used for a predetermined period in a reactor core is taken out of the core and then stored in a spent fuel storage rack installed in a spent fuel pool in the reactor building. The spent fuel storage rack has a function of cooling and storing the spent fuel assembly, which is a heating element, so as not to reach criticality, and is provided with means for preventing damage or overturning against an earthquake load. .

  Conventional methods for installing a spent fuel storage rack include a fixed type that is fixed to the bottom surface of a spent fuel pool with an anchor bolt and a self-supporting type that is not fixed with an anchor bolt.

  In the fixed spent fuel storage rack, a large tensile load acts on the anchor bolt due to the overturning moment at the time of the earthquake, so it is necessary to reduce this tensile load and provide sufficient margin for the concrete strength at the bottom of the pool .

  On the other hand, the self-supporting spent fuel storage rack has the advantage that there is no possibility of damage due to the tensile load of the anchor bolts and it is easy to install and remove, but because it is not fixed to the bottom of the pool, it slides and rises Alternatively, rocking or the like may occur, and the spent fuel storage racks may collide with each other or equipment in the spent fuel pool or the wall of the spent fuel pool and be damaged.

JP 2003-35794 A

  Since the conventional self-supporting spent fuel storage rack described above does not cause damage to the concrete on the bottom surface of the pool due to the tensile load of the anchor bolt, it is possible to ensure a sufficient margin of strength on the bottom surface of the spent fuel pool.

  However, at the time of an earthquake, complicated behavior such as sliding, lifting, rocking, rotation around the vertical axis and / or collision of the spent fuel storage rack occurs, and there is a problem that seismic evaluation becomes difficult.

  Further, in the conventional spent fuel storage rack, it is necessary to widen the interval between the adjacent spent fuel storage racks in consideration of the amount of displacement due to an earthquake or the like, so that the installation space of the spent fuel storage rack is increased. was there.

  The embodiment according to the present invention is made to solve the above-described problems, and can be used to prevent damage to the concrete at the bottom of the pool and the spent fuel storage rack itself due to the spent fuel storage rack during an earthquake. An object is to provide a fuel storage rack.

  In order to solve the above-described problems, a spent fuel storage rack according to an embodiment of the present invention includes a plurality of lattice-shaped cells in which fuel assemblies are accommodated, and a pool bottom surface of the fuel pool provided at the lower portion of the cells. A spent fuel storage rack comprising a housing-like base member placed between the inner wall of the pool or a structure fixed to the inner wall of the pool and a side plate or a bottom plate of the base member. And an elastic member for applying a preload to the base member, and a preload adjusting member for adjusting the preload.

  According to the embodiment of the present invention, it is possible to prevent the concrete on the bottom surface of the pool from being damaged by the spent fuel storage rack and the spent fuel storage rack itself during the earthquake.

The cross-sectional block diagram of the spent fuel storage rack which concerns on 1st Embodiment. The cross-sectional block diagram of the preload adjustment member which concerns on 1st Embodiment. The figure which shows the example of arrangement | positioning of the preload adjustment member which concerns on the modification of 1st Embodiment. The cross-sectional block diagram of the preload adjustment member which concerns on 2nd Embodiment. (A)-(d) is a figure which shows the example of arrangement | positioning of the base member which concerns on 3rd Embodiment.

Hereinafter, embodiments of a spent fuel storage rack according to the present invention will be described with reference to the drawings.
[First Embodiment]
The spent fuel storage rack according to the first embodiment will be described with reference to FIGS. 1 to 3 and FIG. 5.

(overall structure)
As shown in FIGS. 1 and 5, the spent fuel storage rack 2 according to the first embodiment is composed of a plurality of cells 4 that are partitioned in a lattice pattern, and is arranged in the spent fuel pool 3. A spent fuel assembly 1 is accommodated in each cell 4 of the spent fuel storage rack 2, and the spent fuel assembly 1 is cooled and maintained in a subcritical state.

  Among the plurality of cells constituting the spent fuel storage rack 2, a housing-like base member 6 is provided at the lower end of a predetermined number of cells 4 a, and the spent fuel storage rack 2 is interposed via the base member 6. It is installed on the pool bottom 5. A preload adjusting member 8 is provided inside the base member 6. The arrangement configuration of the cell 4a provided with the base member 6 will be described later.

(Configuration of base member 6)
As shown in FIG. 2, the base member 6 has a housing structure in which a side plate 6A and a bottom plate 6B are connected by welding. The upper part is fixed to the lower surface of the spent fuel storage rack 2 by welding or the like, and the lower part is on the pool bottom surface 5. Is placed. Further, the bottom plate 6B is provided with a through hole 6C into which the anchor bolt 7 embedded in the bottom concrete of the spent fuel pool 3 is loosely fitted.

(Configuration of the preload adjusting member 8)
As shown in FIG. 2, the preload adjusting member 8 includes an inverted conical load receiver 9 screwed to the anchor bolt 7 and a plurality of elastic members 10 disposed between the load receiver 9 and the side plate 6A. And.
The elastic member 10 has a fitting member 10a having a conical inner peripheral surface at one end, and the other end fixed to the side plate 6A.

  The load receiver 9 has an inverted conical shape, and a screw hole that is screwed into the anchor bolt 7 is provided at the center thereof. The load receiver 9 is rotated by a known rotating jig (not shown). Thus, the load receiver 9 moves up and down. The outer peripheral surface of the load receiver 9 is slidably in contact with the fitting member 10a, and when the load receiver 9 moves up and down, the fitting member 10a moves left and right to change the spring constant of the elastic member 10. Can do. As a result, the horizontal preload on the base member 6 (side plate 6A) can be appropriately adjusted to a desired magnitude.

  Specifically, this preload is set to a value slightly larger than the horizontal load transmitted from the base member 6 to the elastic member 10 when the spent fuel storage rack 2 resonates due to the maximum seismic force assumed in design. It is desirable to do.

(Function)
In the present embodiment configured as described above, the horizontal load transmitted from the base member 6 to the elastic member 10 when the spent fuel storage rack 2 resonates exceeds the preload within the range of seismic force assumed in design. Therefore, the bottom plate 6B of the base member 6 does not slide with respect to the pool bottom surface 5. On the other hand, when an excessive seismic force is applied, since the horizontal load transmitted from the base member 6 to the elastic member 10 exceeds the preload when the spent fuel storage rack 2 resonates, the bottom plate 6B has the pool bottom surface 5B. Glide on the top.

  In general, the primary natural frequency of the spent fuel storage rack 2 is several tens of Hz, and the amount of displacement of the lower end portion of the spent fuel storage rack 2 due to sliding is about several millimeters.

(effect)
As described above, according to the present embodiment, when the preload adjusting member 8 is arranged inside the base member 6, the spent fuel storage rack 2 resonates within the range of seismic force assumed in design. When the bottom plate 6B of the base member 6 does not slide and exceeds the range of seismic force assumed in design, the spent fuel storage rack 2 slides on the pool bottom surface 5. Thereby, it can suppress that an excessive load is applied to the concrete and the spent fuel storage rack 2 of the pool bottom face 5. Further, since the spent fuel storage rack 2 becomes less slippery than the self-supporting type, and the amount of movement due to the slip is suppressed, the collision of the spent fuel storage racks 2 or the pool side wall 11 of the spent fuel pool 3 is suppressed. It is possible to suppress the occurrence of a collision with the.

(Modification)
In the embodiment described above, the preload adjusting member 8 is disposed inside the base member 6 provided at the lower portion of the predetermined cell 4a. However, as shown in FIG. And the preload adjusting member 8 according to the present embodiment may be disposed between the fuel tank 3 and the pool side wall 11 of the spent fuel pool 3.

[Second Embodiment]
A spent fuel storage rack according to a second embodiment will be described with reference to FIG.
In the first embodiment, the preload adjusting member 8 applies a horizontal preload to the side plate 6A. However, in the second embodiment, the preload adjusting member 12 has a vertical preload applied to the bottom plate 6B. It is set as the structure which loads.

(Constitution)
The preload adjusting member 12 of the second embodiment includes a nut 13 screwed into the anchor bolt 7, a washer-like load receiver 15 attached to the lower surface of the nut 13, and an upper end on the lower surface of the load receiver 15. And an elastic member 14 having a lower end attached to an annular washer 14a. Of these, the washer 14a is placed on the bottom plate 6B.

  The load receiver 15 moves up and down by rotating the nut 13 with a known rotating jig (not shown), and can change the spring constant of the elastic member 14. Thereby, it becomes possible to suppress the slip of the bottom plate 6B of the base member 6 by appropriately adjusting the preload in the vertical direction with respect to the base member 6 to a desired size.

  Specifically, the preload is set to a value that is slightly larger than a value that can prevent the base member 6 from sliding when the spent fuel storage rack 2 resonates due to the maximum seismic force assumed in design. Is desirable.

(Modification)
In this modification, a friction material having a large friction coefficient is interposed between the bottom plate 6B and the pool bottom surface 5 (for example, a friction material is attached to either or both of the bottom plate 6B and the pool bottom surface 5), and the bottom plate 6B and the pool bottom surface. The spent fuel storage rack 2 is made difficult to slip by roughening any one or both of 5 and using a material having a high friction coefficient for the bottom plate 6B. Thereby, it can prevent that the baseplate 6B slips with respect to the earthquake force below design assumption. Further, the washer 14a and the bottom plate 6B may be made non-slipable by taking similar measures such as rough surface processing, adoption of a material having a high friction coefficient, or the like, in which a friction material is similarly interposed.

(Function)
In the present embodiment configured as described above, the bottom plate 6B of the base member 6 does not slide due to the vertical preload when the spent fuel storage rack 2 resonates within the range of the seismic force assumed in design. .
When excessive seismic force is applied, the bottom plate 6B slides about several millimeters on the pool bottom surface 5 when the spent fuel storage rack 2 resonates.

(effect)
According to the second embodiment, as in the first embodiment, when an excessive seismic force is applied, the spent fuel storage rack 2 slides on the pool bottom surface 5 to apply a large load. In addition, by suppressing the sliding of the spent fuel storage rack 2 to a minimum, the concrete damage on the bottom surface 5 of the pool, the collision between the spent fuel storage racks 2, or the pool side wall 11 of the spent fuel pool 3 can be prevented. Collisions can be prevented.

  Further, as shown in the modification, the degree of freedom in design can be increased by increasing the coefficient of friction between the washer 14a and the pool bottom surface 5, and the contact area between the washer 14a and the bottom plate 6B and the attachment by the elastic member 14 can be increased. Since a desired frictional force can be obtained even if the force is reduced, the washer 14a and the elastic member 14 can be downsized.

[Third Embodiment]
A spent fuel storage rack according to a third embodiment will be described with reference to FIG.
In the present embodiment, the arrangement configuration of the base member 6 described in the first and second embodiments will be described.

  The spent fuel storage rack 2 is composed of a plurality of cells 4 partitioned in a lattice pattern. Among them, examples of the arrangement of the cells 4a to which the base member 6 according to each embodiment is attached are shown in FIGS. ).

In FIG. 5A, the base member 6 according to each embodiment is provided in a plurality of cells 4 a (☆ marks) arranged at the four corners of the spent fuel storage rack 2.
In FIG. 5 (b), the base member 6 according to each embodiment is provided in a plurality of cells 4a (*) arranged at two corners on a diagonal line of the spent fuel storage rack 2, and a plurality of other two corners are provided. A conventional anchor bolt fixing means is used for the cell 4a (circle mark).

  In FIG.5 (c), the base member 6 which concerns on each embodiment is provided in the some cell 4a (* mark) arranged in one corner of the spent fuel storage rack 2, and the several cell 4a of the other three corners. A conventional anchor bolt fixing means is used for (circle).

  In FIG. 5 (d), the base member 6 according to each embodiment is provided in a plurality of cells 4 a (☆ marks) close to the center among the plurality of cells 4 a arranged at the four corners of the spent fuel storage rack 2. A conventional anchor bolt fixing means is used for the outer cells 4a (circles).

  Thus, the base member 6 according to the present embodiment can be arranged in various forms, and combined with the fixing means using the anchor bolts, the respective seismic control function and seismic isolation function are combined. The spent fuel storage rack 2 can be configured.

  In particular, in the example shown in FIG. 5 (d), the load at which the spent fuel storage rack 2 starts to slide by disposing the base member 6 according to each embodiment on the center side where the influence of the overturning moment is small and the influence of the shearing force is large. Can be adjusted with high accuracy.

  As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, combinations, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof. For example, it may be a spent fuel storage rack having both the base members of the first embodiment and the second embodiment.

DESCRIPTION OF SYMBOLS 1 ... Used fuel assembly, 2 ... Used fuel storage rack, 3 ... Used fuel pool, 4 ... Cell, 5 ... Pool bottom surface, 6 ... Base member, 6A ... Side plate, 6B ... Bottom plate, 6C ... Through-hole, DESCRIPTION OF SYMBOLS 7 ... Anchor bolt, 8 ... Preload adjustment member, 9 ... Load receiver, 10 ... Elastic member, 10a ... Fitting member, 11 ... Pool side wall, 12 ... Preload adjustment member, 13 ... Nut, 14 ... Elastic member, 14a ... Washer, 15 ... Load receiver

Claims (6)

A spent fuel storage rack comprising a plurality of lattice-shaped cells in which fuel assemblies are accommodated, and a casing-shaped base member that is provided at the bottom of the cells and is placed on the bottom surface of the fuel pool. ,
An elastic member that is interposed between the pool inner wall or a structure fixed to the pool inner wall and a side plate or a bottom plate of the base member, and applies a preload to the base member;
A spent fuel storage rack, comprising: a preload adjusting member that adjusts the preload.   The preload adjusting member includes an anchor bolt loosely fitted in a through hole provided in a bottom plate of the base member and fixed to the bottom surface of the pool, and an inverted conical load receiving member that is screwed into the anchor bolt and can move up and down. The spent fuel storage rack according to claim 1, comprising: a tool, and an elastic member provided between the load receiver and the side plate.   The preload adjusting member includes an anchor bolt loosely fitted in a through hole provided in a bottom plate of the base member and fixed to the bottom surface of the pool, a nut screwed to the anchor bolt and movable up and down, 2. The spent fuel according to claim 1, comprising a load receiving member provided on a lower surface and capable of moving up and down together with the nut, and an elastic member provided between the lower surface of the load receiving member and the bottom plate. Storage rack.   The spent fuel storage according to claim 3, wherein a washer is provided at a lower end portion of the elastic member, and a friction material is disposed between the washer and the bottom plate and / or between the bottom plate and a pool bottom surface. rack.   5. The spent fuel storage according to claim 1, wherein the base member is arranged in a plurality of cells in at least one corner among a plurality of cells in four corners of the fuel storage rack. rack.   A plurality of spent fuel storage racks are disposed in the fuel pool, and the base is disposed between the plurality of spent fuel storage racks and / or between the spent fuel storage rack and a pool side wall of the spent fuel pool. The spent fuel storage rack according to claim 1, wherein members are arranged.

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