JP2012088234A - Nuclear fuel storage rack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent rocking in case of an earthquake which acts vertically and horizontally at the same time.SOLUTION: The nuclear fuel storage rack comprises: a body part 2 for storing nuclear fuel assembly; and paired seismic isolation means 6, 6A for supporting the body part 2 and base-isolating vibrations in a vertical direction. The seismic isolation means 6 comprises: a piston 10 including a piston rod 13 on a top face of which the body part 2 is placed; and a casing 9 in which the piston 10 is reciprocatingly stored and which is vertically partitioned into first space 15 and second space 16 by the piston 10. The first space 15 of one of the paired seismic isolation means 6, 6A is connected to the second space 16A of the other of the seismic isolation means 6, 6A, and the second space 16 of the one of the seismic isolation means 6, 6A is connected to the first space 15A of the other of the seismic isolation means 6, 6A, via pipes 19, 20.

Description

  The present invention relates to a nuclear fuel storage rack that is stored in a state where a nuclear fuel assembly is housed in water in a storage pit of a nuclear fuel storage facility.

  For example, spent nuclear fuel (used nuclear fuel rods) generated at a nuclear power plant is stored and stored in a nuclear fuel storage facility. At this time, spent nuclear fuel is stored in a vertical cell of a nuclear fuel storage rack in a state of being stored in a square tube as a nuclear fuel assembly and stored in a storage pit of the nuclear fuel storage facility. Water is stored in the storage pit. By storing the nuclear fuel storage rack and the nuclear fuel assembly in the water, the decay heat is cooled and kept below the criticality, and radiation is shielded. .

  Conventionally, a nuclear fuel storage rack is fixed to a side wall of a storage pit via a support and stored in a state of being supported by the support and the storage pit (see, for example, Patent Document 1). When the nuclear fuel storage rack is fixed to the storage pit in this way, it is possible to obtain a seismic isolation effect to some extent by the water-added damping effect of water when an earthquake occurs. However, if the support load increases during a major earthquake, the nuclear fuel storage rack may not be supported.

  On the other hand, a nuclear fuel storage rack that is not fixed to the side wall or bottom of the storage pit has been proposed and put into practical use (see, for example, Patent Document 2). In this nuclear fuel storage rack, the nuclear fuel storage rack is slidably mounted on the bottom surface of the storage pit, and the horizontal force acting at the time of the earthquake is generated by sliding the nuclear fuel storage rack together with the fluid added damping effect of water. So that it can be absorbed.

Japanese Patent Laid-Open No. 62-190494 JP 2003-75581 A

However, in the conventional nuclear fuel storage rack, when an earthquake in which vertical vibrations simultaneously act in addition to the horizontal direction occurs, a rocking response tends to occur in the nuclear fuel storage rack. This may increase the possibility that the nuclear fuel storage rack will fall.
In addition, when the current storage pool and nuclear fuel storage rack with seismic structure are transferred to one with a seismic isolation structure, if the bottom surface of the storage pool is uneven, Since the self-weight support load cannot be made uniform, the acting load on the support member accompanying the sliding slide is unevenly distributed, and there remains a problem on the strength of the support member.

  In order to achieve the above object, the present invention provides the following means.

  A nuclear fuel storage rack according to the present invention is a nuclear fuel storage rack installed in water in a storage pit in a state in which a nuclear fuel assembly is stored, and a main body portion that stores the nuclear fuel assembly, and supports the main body portion And a pair of seismic isolation means for isolating vibrations in the vertical direction. The seismic isolation means includes a piston provided with a piston rod on which the main body is placed on an upper surface, and the piston reciprocates inside. A casing that is movably accommodated and that is vertically divided into a first space and a second space in the piston, the first space of the one seismic isolation means and the second space of the other seismic isolation means, And the 2nd space of one seismic isolation means and the 1st space of the other seismic isolation means are connected via piping.

  In the present invention, one first space of the seismic isolation device and the other second space, and one second space and the other first space are connected via a pipe. When the piston is pressed so that the main body of the rack tilts and the pressure in one first space of the seismic isolation device increases, the pressure in the other second space increases and the other seismic isolation The piston of the device moves downward. As a result, the left and right balance of the main body is maintained, so that locking is less likely to occur.

  In the nuclear fuel storage rack according to the present invention, it is preferable that the seismic isolation means is slidably supported with respect to the storage pit floor.

  In the present invention, when an earthquake occurs, the vibration in the horizontal direction can be absorbed by the sliding action between the seismic isolation means and the storage pit.

  In the nuclear fuel storage rack of the present invention, it is desirable that an accumulator is connected to the first space or the second space of the seismic isolation means.

  In the present invention, for example, even when an impact load is applied to the piston due to abrupt vibration and the pressure in the first space or the second space suddenly changes, the piston is enclosed in an accumulator connected to the first space or the second space. The action of alleviating the impact works by contraction of the pressurized gas.

  According to the nuclear fuel storage rack of the present invention, when an earthquake occurs, the right and left balance of the main body of the nuclear fuel storage rack is maintained, so that locking is less likely to occur.

It is sectional drawing which shows the rack for nuclear fuel storage which concerns on 1st Embodiment of this invention. It is sectional drawing which follows the AA line of FIG. It is an expanded sectional view showing a seismic isolation device of a nuclear fuel storage rack concerning a 1st embodiment of the present invention. It is an expanded sectional view which shows the seismic isolation apparatus of the nuclear fuel storage rack which concerns on 2nd Embodiment of this invention. It is an expanded sectional view which shows the seismic isolation apparatus of the nuclear fuel storage rack which concerns on 3rd Embodiment of this invention.

(First embodiment)
Hereinafter, a nuclear fuel storage rack according to a first embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the nuclear fuel storage facility 100 of the present embodiment includes a storage pit 3 in which water W is stored and the nuclear fuel storage rack 1 is stored in water.

  The nuclear fuel storage rack 1 includes a first sliding member 4 installed on the floor surface 3 a of the storage pit 3 and four seismic isolation device units 5 ( FIG. 1 shows only one seismic isolation device unit 5) and a main body 2 supported by the seismic isolation device unit 5 and containing spent nuclear fuel rods (not shown). The first sliding member 4 has a square shape in plan view, and is formed using a low friction sliding member. The seismic isolation device unit 5 includes two seismic isolation devices 6 and 6 </ b> A, each of which supports the main body 2. The seismic isolation device 6 and the seismic isolation device 6A have substantially the same configuration.

  The four seismic isolation device units 5 support the bottom surface 2 a of the main body 2. As shown in FIG. 2, two seismic isolation devices 6 and 6A are disposed in the vicinity of both ends of one side of the bottom surface 2a having a substantially square shape. Is arranged.

As shown in FIG. 3, the seismic isolation device 6 constituting the seismic isolation device unit 5 includes a rectangular plate-like second sliding member 7 and a cylindrical support base joined to the upper surface of the second sliding member 7. 8, a cylindrical casing 9 joined to the upper surface of the support base 8, a piston portion 10 disposed inside the casing 9, and an accumulator 11 connected to the internal space of the casing 9.
The second sliding member 7 is formed by using a low friction sliding member similarly to the first sliding member 4, and the first sliding member 4 and the second sliding member 7 cooperate to slide. A mechanism 26 is configured.

The casing 9 and the piston portion 10 have a function as a so-called air spring by cooperating, and air is sealed inside the casing 9.
The piston portion 10 includes a disc-shaped piston main body 12 and a piston rod 13 joined to the upper surface of the piston main body 12. The outer periphery of the piston main body 12 is slidably inserted on the cylindrical inner surface of the casing 9. Yes. A through hole 14 through which the piston rod 9 passes is formed on the upper surface of the casing 9, and the upper surface of the piston rod 9 is a mounting surface 27 of the nuclear fuel storage rack 2.

  The interior of the casing 9 is partitioned into a first space 15 and a second space 16 by a piston body 12. A lower portion of the piston body 12 is defined as a first space 15 and an upper portion is defined as a second space 16. The volumes of the first space 15 and the second space 16 change as the piston portion 10 moves up and down.

  An accumulator 11 is connected to the first space 15 via a pipe 17. A retractable container 18 filled with nitrogen gas is incorporated in the upper part of the accumulator 11.

  As described above, the seismic isolation device 6 </ b> A has substantially the same configuration as the seismic isolation device 6, and is installed at a predetermined interval from the seismic isolation device 6. The casing 9A of the seismic isolation device 6A is partitioned by the piston body 12 into a first space 15A and a second space 16A.

  The first space 15 of the first seismic isolation device 6 and the second space 16A of the second seismic isolation device 6A are connected by a pipe 19. Similarly, the second space 16 of the first seismic isolation device 6 and the first space 15A of the second seismic isolation device 6A are connected by a pipe 20. That is, as shown in FIG. 3, the two spaces 15, 16, 15A, 16A included in the seismic isolation devices 6, 6A are connected in a cross state.

  According to the above embodiment, when the mounting surface 27 of the piston rod 13 of the first seismic isolation device 6 is pressed by an earthquake that acts simultaneously in the vertical and horizontal directions, the piston portion 10 moves downward. The pressure inside the first space 15 of the seismic isolation device 6 increases. Since the first space 15 of the first seismic isolation device 6 and the second space 16A of the second seismic isolation device 6A are connected, when the pressure inside the first space 15 rises, the second seismic isolation device The pressure inside the 6A second space 16A increases. As the pressure in the second space 16A of the second seismic isolation device 6A increases, the piston portion 10A of the second seismic isolation device 6A moves downward. Thereby, since the balance of the left and right mounting surfaces 27 and 27 is maintained, locking is less likely to occur.

  Further, the horizontal vibration can be absorbed by the occurrence of slippage between the first sliding member 4 and the second sliding member 7.

Further, for example, even when an impact load is applied to the piston portion 10 due to sudden vibration and the pressure in the first space 15 changes suddenly, the container 18 of the accumulator 11 connected to the first space 15 contracts to cause an impact. The mitigating action works.
Further, by providing the accumulator 11, the pressure inside the casing 9 can be adjusted. Furthermore, the height of the piston part 10 can be easily changed.

  Moreover, it is possible to prevent the piston main body 12 of the piston portion 10 from being fixed to the casing 9 by applying an uneven load to the main body portion 2 periodically, for example, once a year.

  In the present embodiment, the first sliding member 4 and the second sliding member 7 are formed using a low friction sliding member. For example, the first sliding member 4 and the second sliding member are used. The first sliding member 4 and the second sliding member 7 may constitute the sliding mechanism 26 by performing a low friction process only on the contact surface 7.

In the present embodiment, a gas such as air is sealed inside the casing 9, but a working fluid such as oil or an aqueous glycerin solution may be sealed inside the casing 9.
Further, the accumulator 11 may be connected not only to the first space 15 but also to the second space 16.

(Second Embodiment)
Next, 2nd Embodiment of this invention is described based on drawing. In this embodiment, the basic structure in which the main body 2 in which the spent nuclear fuel rods are accommodated is supported by the seismic isolation unit 5 is the same as that of the first embodiment. Is omitted.
The nuclear fuel storage rack of this embodiment employs a sliding mechanism by rolling steel balls, so-called ball casters and ball rollers, as an alternative to the first sliding member 4 and the second sliding member 7 of the first embodiment. It is characterized by being.

As shown in FIG. 4, a steel plate 21 having a predetermined thickness is placed on the floor surface 3a of the storage pit 3 of the present embodiment. As for the seismic isolation apparatus 6B which comprises the seismic isolation unit 5B, the casing 9 is supported by the ball caster part 22. FIG.
The ball caster portion 22 includes a cylindrical caster main body portion 23, a base portion 24 joined to the lower portion of the main body portion 23, and a ball portion that is stored inside the main body portion 23 and is partially exposed from the opening of the base portion. 25 and supports the seismic isolation device 6 so as to be movable in an arbitrary direction.

  According to the embodiment, the horizontal vibration can be absorbed by the ball portion 25 rolling on the steel plate 21. Since the reaction force in the horizontal direction at the time of rolling is 1/5 to 1/10 as compared with the sliding mechanism 26 of the first embodiment, in addition to the effect of the first embodiment, it further acts in the horizontal direction due to an earthquake. The load can be reduced.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to the drawings. Also in this embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.
The nuclear fuel storage rack of this embodiment is a modification of the nuclear fuel storage rack of the second embodiment, and adopts a pedestal having a concave spherical recess as an alternative to the steel plate 21 of the nuclear fuel storage rack 1B. It is characterized by being.

  As shown in FIG. 5, a pedestal 29 with a recess is placed on the floor surface 3a of the storage pit 3 of the present embodiment. A recess 28 corresponding to the positions of the casing 9 and the piston portion 10 of the seismic isolation device 6 </ b> C is formed on the base 29 with the recess. At least a part of the recess 28 has a curved surface shape so that the height from the floor surface 3a gradually increases from the center to the outer periphery. As described above, since the recesses 28 are formed at positions corresponding to the ball portions 25 of the respective seismic isolation devices 6, eight recesses 28 are formed on the pedestal 29 with the recesses of the present embodiment. .

  According to the above-described embodiment, in addition to the effects of the second embodiment, an earthquake occurs and the nuclear fuel storage rack 1 responds greatly, slides on the recess 28, and then is guided by the inclination of the recess 28, thereby storing it. It is possible to return to the normal position on the floor surface 3a of the pit 3, that is, the origin.

1: nuclear fuel storage rack, 2: main body, 3: storage pit, 6, 6A: seismic isolation device (seismic isolation means), 9: casing, 10: piston part (piston), 11: accumulator, 13: piston rod , 15: first space, 16: second space, 19: piping, 20: piping

Claims (3)

A nuclear fuel storage rack installed in the water in the storage pit with the nuclear fuel assembly stored therein,
A main body for storing the nuclear fuel assembly;
Comprising a seismic isolation means for supporting the main body and making a pair for isolating vibrations in the vertical direction;
The seismic isolation means includes a piston provided with a piston rod on which the main body portion is placed;
The piston is housed in a reciprocating manner inside, and the piston has a casing partitioned vertically into a first space and a second space,
The first space of the one seismic isolation means and the second space of the other seismic isolation means, and the second space of one seismic isolation means and the first space of the other seismic isolation means are connected via a pipe. A nuclear fuel storage rack characterized by comprising: The nuclear fuel storage rack according to claim 1,
The nuclear fuel storage rack, wherein the seismic isolation means is slidably supported with respect to the storage pit floor. The nuclear fuel storage rack according to claim 1 or 2,
The nuclear fuel storage rack, wherein an accumulator is connected to the first space or the second space of the seismic isolation means.