JP2010256057A - Radioactive material storage facility - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve stable ventilation at lower costs and to reduce workers' radiation exposure in a manned work for carrying in storage casks in a radioactive material storage facility. <P>SOLUTION: In a radioactive material storage facility which includes a storage building 1 provided with storage blocks 3 and where casks 9 for storing radioactive materials are fixed and stored in each of the storage blocks 3, movable shielding walls 7 which can shield in an intended direction against the radiation from casks fixed in the storage blocks and is made movable so that it optionally selects one from a shielding condition and a non-shielding condition are set up in the storage building 1. While the movable walls 7 is normally kept in a non-shielding condition, then, they are taken to be controlled so as to achieve a shielding condition which protects workers engaged in the carrying-in work against the radiation from the casks in the storage block in the work for carrying in the casks. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a radioactive material storage facility that stores radioactive material in a state of being stored in a radioactive material storage container such as a cask, and more specifically, to each storage block provided in a storage building in the radioactive material storage facility. The present invention relates to a technique for reducing the radiation exposure dose of a worker when carrying in a radioactive substance storage container.

  Nuclear power generation involves the storage of radioactive materials such as temporary storage of nuclear fuel before use or transient storage until reprocessing of spent fuel. A dry storage system is a typical system for storing radioactive materials associated with nuclear power generation. In the dry storage system, radioactive material (pre-use nuclear fuel or spent fuel) is stored in a state of being stored in a radioactive material storage container (hereinafter referred to as a storage container as appropriate) such as a cask (generally made of metal). . In general, a radioactive material storage facility in a dry storage system includes a storage building provided with a plurality of storage blocks that are divided and formed, and one or more storage containers are placed in each storage block. It comes to store.

  In such radioactive material storage facilities, there are important heat removal problems and exposure problems. The heat removal problem is a problem related to appropriately removing heat generated from radioactive materials as decay heat and released through the cask. More specifically, it is a problem related to the ventilation structure necessary to ensure proper ventilation in each storage block in the storage building required for heat removal and maintain the cooling performance of the cask, and it is more stable It is a problem related to the realization of a ventilation structure that enables efficient ventilation at a lower cost.

  On the other hand, the exposure problem is a problem related to reduction of radiation exposure received by workers during the carrying-in work of carrying the storage container into a predetermined storage block in the storage building and placing it. Regarding this exposure problem, for example, examples disclosed in Patent Document 1 and Patent Document 2 are known.

  Patent Document 1 discloses a technique for remotely automating a transport operation by using an air pallet transport device for transporting a storage container. According to the technique disclosed in Patent Document 1, it is possible to greatly reduce the radiation exposure of workers by remotely automating the transfer work.

  Patent Document 2 discloses a structure of a radioactive substance storage facility that enables an exposure condition that enables switching to a manual operation when trouble such as a failure occurs in an unmanned conveyance device such as an air pallet conveyance device. is doing. Specifically, a plurality of storage areas formed by partitioning with shielding walls are provided, and a building provided with a building passage that leads to each storage area is provided. For radioactive material storage facilities that are designed to transport storage containers to each storage area, a shielding means that shields radiation between the interior passage and the storage area can be opened and closed at a position where the interior passage communicates with each storage area. In the normal state, the shielding means is closed so as to shield the radiation between the building passage and the storage area, and when the storage container is transported, the shielding means is opened for the corresponding storage area. . By doing in this way, the radiation level in a passage inside a building can be reduced, and thereby work by an operator required when a trouble occurs in the automatic transfer device can be performed.

JP 2003-156594 A JP 2005-172443 A

  It can be said that the method of automating, that is, unmanned, using an air pallet conveying device as in the example disclosed in Patent Document 1 is effective as a measure for reducing exposure in a radioactive substance storage facility. However, an unmanned transfer work system using an air pallet transfer device or the like is accompanied by a significant increase in equipment cost, and it is necessary to cope with a system trouble. For this reason, the unmanned system is not necessarily general-purpose, and there are many cases in which a manned system that relies on manual operation for carrying in the storage container is adopted.

  When carrying-in work is manned, it is necessary to deal with exposure problems. About this, the facility structure like the example disclosed in Patent Document 2 above, that is, a shielding means that can be opened and closed, is provided so that each storage area (storage block) can be shielded against radiation from the building passage by the shielding means. The facility structure is effective. However, the heat removal problem remains in the facility structure of Patent Document 2. That is, in the facility structure of Patent Document 2, the shielding means is closed in a normal state so as to shield the radiation between the building passage and the storage block. This causes each storage block to be in a sealed state or a state close thereto when each storage block is formed by partitioning with a shielding wall (partition wall). For this purpose, a forced ventilation system using a ventilation device such as a ventilation fan is required to ensure appropriate ventilation in each storage block. However, the forced ventilation system requires countermeasures against the failure of the ventilation equipment or the stoppage of the ventilation equipment due to a power failure, resulting in a significant increase in equipment cost.

  For these reasons, it is strongly desired to realize a radioactive material storage facility that enables stable ventilation at a lower cost and that can reduce the radiation exposure of workers when carrying in the storage container by the manned method.

  The present invention has been made to meet these demands, and enables stable ventilation at a lower cost for a radioactive material storage facility, and further reduces the radiation exposure of workers when carrying in a storage container by a manned method. The challenge is to enable reduction.

  In the present invention, in order to solve the above problems, a storage building provided with a plurality of storage blocks formed by partitioning is provided, and a radioactive substance storage container storing a radioactive substance is placed on each storage block. In the radioactive substance storage facility designed to store, radiation from the radioactive substance storage container stationary on the storage block can be shielded in a target direction, and is made movable so as not to be shielded. A movable shielding wall that can be selectively shielded is provided in the storage building, and the movable shielding wall is normally unshielded while the radioactive substance storage container. In the storage block other than the storage block to be carried in, during the carrying-in work of carrying in and placing in any of the storage blocks It is characterized in that it is to take the shielding state to protect personnel of the carry work on radiation from quality container.

  In such a radioactive substance storage facility according to the present invention, a movable shielding wall is provided, and the movable shielding wall is used to shield radiation in a target direction, so that a worker carrying in the storage container can receive radiation from the storage container in the storage block. Can be protected with respect to. Therefore, it is possible to reduce the radiation exposure of the worker when carrying in the storage container by the manned method. On the other hand, in the radioactive substance storage facility according to the present invention, the movable shielding wall is normally unshielded. For this reason, even when each storage block is divided and formed by partition walls, the storage block is normally in relation to the part without the partition walls, that is, the part that is shielded by the movable shielding wall when necessary. It can be in an open state. Therefore, it is possible to ensure appropriate ventilation in each storage block only with the natural ventilation structure provided in the entire storage building. And since the natural ventilation structure requires a power source and does not substantially require ventilation equipment that is difficult to avoid, it is possible to achieve highly stable ventilation and reduce equipment costs. .

  For radioactive material storage facilities such as those described above, a structure in which a movable shielding wall is provided for each storage block and a structure in which the movable shielding wall can be shared for a plurality of storage blocks are possible depending on the storage block installation structure. It is. Therefore, in the present invention, in the radioactive substance storage facility as described above, the movable shielding wall is provided for each of the storage blocks, or the movable shielding wall is provided so as to be shared by the plurality of storage blocks. I have to.

  As described above, the radioactive substance storage facility according to the present invention is configured such that each storage block is separated from the partition wall even when each storage block is partitioned by the partition wall by making the movable shielding wall unshielded. It is possible to ensure appropriate ventilation in each storage block with only the natural ventilation structure by opening the storage building with respect to the non-existing part. Such a feature of the radioactive substance storage facility according to the present invention is particularly effective in a facility structure in which each storage block is partitioned by a partition wall. Therefore, in the present invention, the above-described radioactive substance storage facility is preferably configured such that each storage block is partitioned by a partition wall.

  According to the present invention as described above, it is possible to stably ventilate a radioactive material storage facility at a lower cost, and it is possible to reduce the radiation exposure of workers when carrying a storage container by a manned method. It becomes.

It is a figure which shows typically the internal structure by the longitudinal cross-section of the storage building in the radioactive substance storage facility by a 1st Example. It is a figure which shows typically the principal part internal structure by the cross section of the storage building of FIG. 1 about the non-shielding state of a movable shielding wall. It is a figure which shows typically the principal part internal structure by the cross section of the storage building of FIG. 1 about the shielding state of a movable shielding wall. It is a figure which shows typically the principal part internal structure by the cross section of the storage building in the radioactive substance storage facility by 2nd Example about the non-shielding state of a movable shielding wall. It is a figure which shows typically the principal part internal structure by the cross section of the storage building in the radioactive substance storage facility by 2nd Example about the shielding state of a movable shielding wall.

  Hereinafter, modes for carrying out the present invention will be described.

  1 to 3 show a radioactive substance storage facility according to the first embodiment. FIG. 1 schematically shows the internal structure of a storage building 1 in the radioactive substance storage facility according to the first embodiment in a vertical section, and FIG. 2 shows the movable internal structure of the main part in the cross section of the storage building 1 of FIG. 3 schematically shows the non-shielding state of the shielding wall, and FIG. 3 schematically shows the internal structure of the main part of the storage building 1 in FIG. 1 with respect to the shielding state of the movable shielding wall.

  The storage building 1 of the present embodiment is used for long-term storage of radioactive substances, and is a case where a storage container containing radioactive substances is placed in a vertical position and stored, and reaches the ceiling, for example, as shown in FIG. A plurality of vertically installed storage blocks 3 formed by partitioning an indoor space with a partition wall 2 provided as a structural wall are provided. Specifically, in the case of the example in FIG. 2, eight vertically installed storage blocks 3 are provided as the storage blocks 3 a to 3 h. Further, these eight vertical stationary storage blocks 3 are provided in blocks of four so as to sandwich the conveyance path 5 leading to the loading / unloading port 4 provided in the central portion of the storage building 1. And each storage block 3 is provided for each storage block 3 while the side facing the transport path 5 is an open portion 6 and is opened toward the transport path 5 by the open portion 6. The movable shielding wall 7 allows the opening 6 to be shielded when necessary with respect to radiation (mainly gamma rays and neutron rays from radiation from the cask 9 placed in the storage block 3 as described later). ing.

  The movable shielding wall 7 is formed in a structure capable of appropriately blocking gamma rays and neutron rays, and is provided to be movable up and down by a shielding wall drive system that is driven under the control of a shielding wall control system (not shown). By the vertical movement, the shielding state and the non-shielding state with respect to the opening 6 can be selectively taken. More specifically, it is provided so that it can be stored in the shielding wall storage part 8 (FIG. 1) formed by digging the floor of the storage building 1. When the storage block 3 is opened with respect to the conveyance path 5 by the opening 6, that is, when the opening 6 is unshielded, the movable shielding wall 7 is accommodated in the shielding wall storage 8 and opened. When the part 6 is in the shielding state, the movable shielding wall 7 can be removed from the shielding wall storage part 8 to cover the opening part 6.

  Each of the storage blocks 3 as described above is formed into a radioactive substance storage container in which radioactive substances are stored, specifically, for example, a cylindrical shape having a diameter of about 2 m and a height of about 6 m, and has a weight of about 100 tons. The metal cask 9 is placed vertically, for example, as 8 pieces per block. The cask 9 is carried into each storage block 3 by a manned system using a transport device (not shown) such as the air pallet transport device disclosed in Patent Document 1 in the transport path 5. That is, the carrying-in work is performed by moving the carrying path 5 as indicated by the arrow in the drawing so that the worker is accompanied by the carrying device on which the cask 9 is placed.

  In the case of such a manned method for carrying in the storage container, it is necessary to take measures for reducing the exposure of the worker to the radiation from the cask 9 already placed in the storage block 3. This is dealt with by shielding the opening 6. This will be described below with reference to FIG. In the example of FIG. 3, a new cask 9n is carried into the storage block 3a. In this case, the destination of the new cask 9n is determined in advance from the viewpoint of storage management. Information about the destination is recorded in an information recording medium that enables remote reading, such as an RFID (Radio Frequency Identification) tag attached to the cask 9n. When passing through the loading / unloading port 4, it is read by an information recording medium reader installed at the loading / unloading port 4. The read-in destination information is provided to the shielding wall control system as information for controlling the state of the movable shielding wall 7 prior to the carrying-in operation. The shielding wall control system that has received the delivery destination information controls the driving of the movable shielding wall 7 of each storage block 3 based on the delivery destination information. In the case of the example in FIG. 3, the movable shielding wall 7 of the storage block 3a that is the destination of the cask 9n is kept in the shielding wall storage portion 8 so as to be unshielded, and the other storage blocks 3b to 3 are stored. The movable shielding wall 7 of each block 3h is brought into a shielding state by being removed from the shielding wall storage portion 8 and covering the opening portion 6. For this reason, the radiation from the stationary cask 9 can be shielded from the conveyance path 5 in each of the storage blocks 3b to 3h during the carrying-in work, thereby reducing the radiation exposure of the workers during the carrying-in work. it can.

  Here, it is desirable that the worker can confirm the shielding state and non-shielding state of the movable shielding wall 7 in each of the storage block 3a to the storage block 3h when entering the conveyance path 5 from the carry-in / out port 4. For this purpose, for example, an appropriate monitor device is provided in the vicinity of the loading / unloading port 4 so that the state of the movable shielding wall 7 can be displayed on the monitor device.

  In the state where the storage container is not carried in as described above, that is, in a normal state, the movable shielding wall 7 is unshielded for all the storage blocks 3, and all the storage blocks 3 are connected to the transport path 5 by the opening 6. It is made to be in an open state. In this way, the storage block 3 is opened with respect to the transport path 5 only by the natural ventilation structure in the storage building 1 as will be described later, and appropriate ventilation in each storage block 3, that is, the cask 9 in each storage block 3. This is to ensure the ventilation required to maintain the cooling performance of the.

  As shown in FIG. 1, the natural ventilation structure in the storage building 1 includes an exhaust tower 11 provided at an appropriate height in the center of the ceiling of the storage building 1 and an outside air inflow portion 12 provided in the side wall of the storage building 1. A negative pressure is formed in the storage building 1 by the exhaust force due to the chimney effect of the exhaust tower 11, and outside air is caused to flow in from the outside air inflow portion 12 by the negative pressure, as shown by block arrows in the drawing. It is made to circulate in a state, and appropriate ventilation can be secured to each storage block 3 by this outside air circulation. In such a natural ventilation structure, each storage block 3 needs to be opened to the outside air circulation, but this necessary opening is ensured by opening each storage block 3 to the conveyance path 5. Therefore, appropriate ventilation in each storage block 3 can be ensured only by the natural ventilation structure. Here, the exhaust tower 11 is provided with a radiation shield 13, and the radiation shield 13 can appropriately prevent radiation from being emitted to the outside due to exhaust from the exhaust tower 11.

  4 and 5 show a radioactive substance storage facility according to the second embodiment. 4 and 5 schematically show the internal structure of the main part of the storage building 21 in the radioactive substance storage facility according to the second embodiment, and FIG. 4 shows the unshielded state of the movable shielding wall. FIG. 5 shows the shielding state of the movable shielding wall.

  The storage building 21 of this embodiment is used for storing radioactive materials for a short period of time, and is a case where a storage container storing radioactive materials, specifically, a cask 9 as described above is placed horizontally, and a structural wall A plurality of horizontally installed storage blocks 23 formed by partitioning the interior with a partition wall 22 provided as a unit are provided. Specifically, in the case of the example in FIG. 4, four horizontal stationary storage blocks 23 are provided as the storage blocks 23 a to 23 d. Each of these storage blocks 23 is individually provided with a loading / unloading port 24 and is divided into two sub-blocks. One horizontal cask 9 is placed in each sub-block, and two caskes 9 are fixed. It has been made possible. That is, each storage block 23 is divided into a back side sub-block 25 on the back side and a front side sub-block 26 on the front side with reference to the loading / unloading port 24, and the back side sub-block 25 and the front side sub-block 25. A total of two casks 9 can be placed in each of the blocks 26. And each storage block 23 selectively shields between the back side subblock 25 and the near side subblock 26 in each storage block 23 by the movable shielding wall 27 provided so that it can share with respect to each storage block 23. It has been made possible.

  Similar to the movable shielding wall 7 described above, the movable shielding wall 27 is formed to have a structure capable of appropriately blocking gamma rays and neutron rays, and the boundary between the back sub-block 25 and the front sub-block 26 of each storage block 23. The vehicle travels on the traveling rail 28 by a shielding wall drive system that is driven under the control of a shielding wall control system (not shown). Thus, the storage block 23 can be shared. More specifically, it is provided so as to be housed in a shielding wall housing portion 29 formed so as to protrude outward from the side wall of the storage building 21. When any of the storage block 23a to the storage block 23d is in a shielding state between the back side sub-block 25 and the front side sub-block 26, the movable shielding wall 27 is pulled out from the shielding wall storage portion 8 to store the storage block 23a. ~ Located at the boundary between the back sub-block 25 and the front sub-block 26 in any one of the storage blocks 23d, and the storage block 23a to the storage block 23d are located between the back-side sub block 25 and the front sub-block 26. When the non-shielding state is established, that is, when the communication state is established, the movable shielding wall 27 is accommodated in the shielding wall storage portion 29.

  The cask 9 is normally carried into the storage block 3 by, for example, being directly lowered from the truck that has transported the cask 9 and placed on the back side sub-block 25 or the front side sub-block 26. This carry-in work is performed in a manned manner that is attended by workers.

  Also in the work of loading the storage container by such a manned method, the worker is exposed to radiation from the cask 9 already placed in the storage block 23. In the storage building 21, this is dealt with by shielding between the back side sub-block 25 and the front side sub-block 26 by the movable shielding wall 27. This will be described below with reference to FIG. In the example of FIG. 5, a new cask 9 n is carried into the front sub-block 26 of the storage block 23 a where the cask 9 is already placed in the back sub-block 25. It is the same as in the case of the first embodiment that the new destination information of the cask 9n is provided to the shielding wall control system through the information recording medium attached to the cask 9n. The shielding wall control system that has received the delivery destination information drives the movable shielding wall 27 based on the delivery destination information to be positioned in the storage block 23a, and the rear side sub-block 25 and the front side sub-block in the storage block 23a. 26 is shielded. For this reason, the radiation from the cask 9 stationary on the back side sub-block 25 can be shielded from the near-side sub-block 26 during the carry-in work, thereby reducing the radiation exposure of workers during the carry-in work. .

  On the other hand, at the normal time when the storage container is not carried in as described above, the movable shielding wall 27 is accommodated in the shielding wall housing portion 29, and the back side subblock 25 and the front side subblock 26 are mutually connected in all the storage blocks 23. It is in an open state. For this reason, appropriate ventilation in each storage block 23 can be ensured only by the natural ventilation structure as described above.

  In the horizontal stationary storage building 21, the cask 9 is usually carried in and out at a high frequency, and when the cask 9 is carried out at a high frequency, the worker receives radioactivity in the same manner as at the time of the carry-in. However, this can also be dealt with by shielding the back side sub-block 25 and the front side sub-block 26 by the movable shielding wall 27.

  As mentioned above, although the form for implementing this invention was demonstrated, this is only a representative example and this invention can be implemented with various forms in the range which does not deviate from the meaning.

1,21 Storage building 2,22 Partition wall 3,23 Storage block 7,27 Movable shielding wall 9 Cask (radioactive substance storage container)

Claims (2)

In a radioactive material storage facility comprising a storage building provided with a plurality of storage blocks formed by partitioning, and storing radioactive material storage containers storing radioactive materials in the respective storage blocks ,
In addition to being able to shield the radiation from the radioactive substance storage container stationary on the storage block in a target direction, it is possible to selectively take a shielded state and a non-shielded state by being movable. The movable shielding wall is provided in the storage building, and the movable shielding wall is normally in a non-shielding state, while the radioactive substance storage container is carried in and placed in one of the storage blocks. In carrying-in work, a shielded state is taken so as to protect workers of the carry-in work with respect to radiation from the radioactive substance storage container in the storage block other than the storage block to be carried in, A radioactive material storage facility.   The radioactive substance storage according to claim 1, wherein the movable shielding wall is provided for each of the storage blocks, or the movable shielding wall is provided so as to be shared by the plurality of storage blocks. Facilities.

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