JP2013057556A - Storage facility for sewage sludge containing radioactive material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a facility capable of storing sewage sludge containing a radioactive material in safety by shielding radiation thereof and capable of being constructed in a short construction period.SOLUTION: A storage facility for sewage sludge containing a radioactive material comprises: blocks 1 for a box culvert made of precast concrete that are placed on a mounting surface so that openings are directed to sides and that are connected in a length direction; end panels 5 made of precast concrete that seal the openings of both ends of the connected blocks 1 for the box culvert; and water-impervious sheets 7 laid along inner surfaces of the blocks 1 for the box culvert and the end panels 5.

Description

  The present invention relates to a storage facility for sewage sludge containing radioactive substances.

  The Tohoku-Pacific Ocean Earthquake that occurred on March 11, 2011, and the accompanying tsunami damaged the nuclear power generation facility at the Fukushima Daiichi Nuclear Power Station. Released outside the house and scattered around. Since then, radioactive substances have been detected one after another from sludge in sewage treatment facilities in various locations where rainwater flows.

  In general, sewage sludge discards incineration ash, uses molten slag produced by incineration at high temperature as concrete aggregate (Patent Document 1), uses dried organic matter as compost and fuel (patent) Document 2, 3). However, sewage sludge containing radioactive substances has a problem of health damage, so that the general treatment as described above is difficult. Therefore, at present, the treatment method of sewage sludge containing radioactive substances is not clear, and is temporarily stored only by a simple curing method such as sheet curing. However, in sheet curing, etc., radiation shielding effects are hardly expected, and care is required not only during storage but also during transportation.

“The concept of the immediate handling of by-products such as water and sewage treatment (註)” announced by the Nuclear Emergency Response Headquarters on June 16, 2011 (註: dewatered sludge and dewatered sludge incinerated, melted, etc. In the case of products that are reused, the following ideas were presented, but there are still many items that must be considered.
・ Store sludge with radioactive cesium concentration exceeding 100,000 Bq / kg in a facility that can shield radiation appropriately in the prefecture. We will continue to examine specific disposal methods.
・ Sludge with a radioactive cesium concentration of more than 8,000 Bq / kg and less than 100,000 Bq / kg can be temporarily placed in a managed disposal site while maintaining an appropriate distance from the residential area. After individual safety assessment and long-term management methods, it can be landfilled.
-Sludge with a radioactive cesium concentration of 8,000 Bq / kg or less can be temporarily placed in a management-type disposal site while maintaining an appropriate distance from residential areas. Can be landfilled on the premise that the site will not be used for residence.

JP-A-6-279084 JP-A-5-155678 JP-A-9-248600

  As a method of storing sewage sludge so that radiation can be shielded, it can be buried in the soil. However, this method has problems that it is difficult to control the burial depth or that there is anxiety about long-term storage. Moreover, since it is necessary to dig up when the final treatment method and the destination of the sewage sludge are moved, there is a problem that it takes time.

  Therefore, an object of the present invention is to provide a facility that can safely store sewage sludge containing radioactive substances while shielding the radiation, and can also store it for a long time if necessary. Also, it is to be able to construct a facility with the required capacity in a short construction period. Furthermore, it is to make it possible to easily move the sewage sludge at a stage where the final treatment method and the destination of the sewage sludge are determined.

(1) The storage facility for sewage sludge containing radioactive substances according to the present invention is for precast concrete box culverts that are installed on the installation surface with the openings facing sideways and connected (joined) in the length direction. It is characterized by comprising a block, an end panel made of precast concrete that closes the openings at both ends of the connected box culvert block, and a water shielding sheet laid along the inner surface of the box culvert block and the end panel. .

(2) The method for constructing a storage facility for sewage sludge containing radioactive substances according to the present invention is such that a box culvert block made of precast concrete is installed on the installation surface with the opening facing sideways and connected in the length direction. And closing the opening of one end of the connected box culvert block with an end panel made of precast concrete, and laying a water shielding sheet along the inner surface of the box culvert block and the end panel;
Carrying sewage sludge containing radioactive material contained in a container into the box culvert block;
And a step of laying a water shielding sheet in the opening at the other end of the box culvert block and closing the opening with an end panel made of precast concrete.

In each of the above means, the size of the box culvert block is not particularly limited. However, in terms of a large amount of storage, those having a large inner cross-sectional area are preferable, and specifically, those having an inner cross-sectional area of 40 to 80 m ² . preferable. Further, a split type box culvert block capable of easily forming such a large one is preferable. Examples of the divided box culvert block include the following.
(A) A U-shaped bottom slab member composed of a horizontal bottom slab part and two vertical side wall parts, and an overlying U-shaped top slab member composed of a horizontal top slab part and two vertical side wall parts; And are joined in a box shape (see FIG. 10).
(A) a U-shaped bottom slab member composed of a horizontal bottom plate part and two vertical side wall parts, and an overlying U-shaped top plate member composed of a horizontal top plate part and two vertical side wall parts; The first side wall member on the left side and the second side wall member on the right side are divided into four parts, and these are joined in a box shape (see FIG. 11).
(C) an L-shaped first sidewall member comprising a horizontal partial bottom plate portion and a vertical sidewall portion; an L-shaped second sidewall member comprising a horizontal partial bottom plate portion and a vertical sidewall portion; It is divided into three parts, a plate-shaped top plate member consisting of a plate part and two vertical side wall parts, and these are joined in a box shape (see FIG. 2 etc.).

  Although the concrete thickness of the box culvert block and the end panel is not particularly limited, it is 10 to 50 cm in view of the balance between the attenuation performance of the radiation dose and the block weight suitable for moving and transporting with an actual mobile transport facility. It is preferable. If it is less than 10 cm, the radiation dose attenuation performance is low, and if it exceeds 50 cm, the radiation dose attenuation performance is not so high, but becomes heavy. For example, when the thickness is 12 cm, the radiation dose can be attenuated by about 75%, when the thickness is 15 cm, the radiation dose can be attenuated by about 80%, and when the thickness is 20 cm, the radiation dose is reduced. It can be attenuated by about 90%, and when the thickness is 40 cm, the radiation dose can be attenuated by about 99%.

  When joining the members made of precast concrete, adjacent surfaces (for example, connected in the length direction) that are close to each other (including contact). Between the adjacent surface between the box culvert block and the box culvert block, the adjacent surface between the divided members of the split-type box culvert block, and the adjacent surface between the box culvert block and the end panel). It is preferable that all the voids bend in the middle from the inner surface to the outer surface of the member so as not to be in a straight line from the inner surface to the outer surface of the member. The radiation radiated from the radioactive material of sewage sludge has the property of going straight, and if the gap is in a straight line from the inner surface to the outer surface, there is a risk of leaking outside through the gap. This is because if it is not in a straight line from the outer surface to the outer surface, it will surely pass through the concrete part and attenuate.

  Although it does not specifically limit as a water-impervious sheet, The sheet | seat consisting of elastomers, such as sheets, such as polyethylene resin and polyvinyl chloride, and polyethylene-type elastomer, can be illustrated. Moreover, what formed the clay mineral (bentonite) which has waterproof performance and adsorption | suction performance in the sheet form can also be used as a water-impervious sheet.

  It is preferable that a sheet fixing tool having a heat welding material on the surface is attached to the inner wall of the box culvert block and the end panel, and the water shielding sheet is welded and fixed to the heat welding material. This is because displacement and peeling of the water shielding sheet are prevented.

  The state of the sewage sludge containing radioactive substances stored in the sewage sludge storage facility of the present invention is not particularly limited, and may be any of dewatered sewage sludge, incinerated ash of incinerated sewage sludge, and molten slag of incinerated sewage sludge. Further, the sewage sludge may be in a bare state, but it is preferable that the sewage sludge is placed in a container from the viewpoint of ease of transfer. Although it does not specifically limit as a container which puts a sewage sludge, A bag (A ton bag, a sandbag bag, etc.) and a box (A wooden box, a resin box, a box made from precast concrete, etc.) can be illustrated.

  The installation surface for installing the box culvert block may be the ground at the storage site (including the bottom of the groove excavated in the ground so that the bottom plate of the block fits), or the box culvert block is stored under the ground. It may be the bottom of a recess dug in the ground so that it can. In the latter case, the upper part of the sewage sludge storage facility can be used as a part of the ground on the site.

  According to the present invention, sewage sludge containing a radioactive substance can be stored safely while shielding its radiation, and can also be stored for a long time if necessary. In addition, a facility with the required capacity can be constructed in a short construction period. Furthermore, it is possible to easily move the sewage sludge at a stage where the final treatment method and the destination of the sewage sludge are determined.

It is a perspective view which shows the ground of the storage field which excavated the groove | channel in Example 1. FIG. It is a perspective view which shows the installation step of the block for box culverts and one end panel in the Example. It is a perspective view which shows the completion of installation of the box culvert block in the same Example. The step which lays a water-impervious sheet in the same Example is shown, (a) is a perspective view which shows the method of welding fixation of the water-impervious sheet, (b) is a sectional view. It is a perspective view which shows the middle of carrying in sewage sludge to the inside of the box culvert block in the Example. In the same Example, (a) is a front view which shows the state which carried in sewage sludge in the inside of a box culvert block, (b) is sectional drawing of a junction part. It is a perspective view which shows the installation step of the other end panel in the Example. It is a perspective view which shows the sewage sludge storage facility completed in the Example. It is a perspective view which shows the sewage sludge storage facility of Example 2. FIG. It is a perspective view which shows the block for box culverts of Example 3, and its installation step. It is a perspective view which shows the block for box culverts of Example 4, and its installation step.

  The storage facility for sewage sludge containing radioactive material is a precast concrete box culvert block that is installed on the installation surface with the opening facing sideways and connected in the length direction, and the connected box culvert block And an end panel made of precast concrete that closes the openings at both ends of the frame, and a water shielding sheet laid along the inner surface of the box culvert block and the end panel.

For the construction method of the storage facility for sewage sludge containing radioactive substances, the box culvert block made of precast concrete is installed on the installation surface with the opening facing sideways and connected in the length direction. Closing the opening at one end of the block with an end panel made of precast concrete, and laying a water shielding sheet along the inner surface of the box culvert block and the end panel;
Carrying sewage sludge containing radioactive material contained in a container into the box culvert block;
And a step of laying a water shielding sheet in the opening at the other end of the box culvert block and closing the opening with an end panel made of precast concrete.

  A first embodiment of a sewage sludge storage facility and its construction method embodying the present invention will be described with reference to FIGS. The sewage sludge storage facility of the present embodiment has a box culvert block 1 made of precast concrete that is installed on the installation surface and connected in the length direction with the opening facing sideways, and the box culvert block that is connected. 1 is composed of end panels 5 and 6 made of precast concrete that close the openings at both ends of 1, and a water shielding sheet 7 laid along the inner surface of the box culvert block 1 and the end panels 5 and 6.

As shown in FIG. 2 and the like, the precast concrete box culvert block 1 used in the first embodiment includes an L-shaped first side wall member 2 composed of a horizontal partial bottom plate portion 2a and a vertical side wall portion 2b, and a horizontal An L-shaped second side wall member 3 composed of a partial bottom plate portion 3a and a vertical side wall portion 3b, and an overlying U-shaped top plate member 4 composed of a horizontal top plate portion 4a and vertical side wall portions 4b and 4c. And is divided into three, and these are joined in a box shape.
Reinforcing bars (not shown) are embedded in the side wall members 2 and 3, and in particular, prestress in the vertical direction is introduced into the side wall portions 2b and 3b by a PC steel material (not shown).
Reinforcing bars (not shown) are embedded in the top plate member 4, and in particular, prestress in the horizontal direction is introduced into the top plate portion 4a by a PC steel material (not shown).
Examples of the dimensions of the box culvert block 1 include a length direction (connection direction) length of 100 cm, an inner width of 10 to 13 m, an inner height of 5 to 6 m, a top plate portion 4a thickness of 40 to 60 cm, and a partial bottom plate portion. 2a, 3a thickness 45-75 cm, side wall portions 2b, 3b, 4b, 4c thickness 40-55cm, side wall portions 2b, 3b projecting length 100cm from the inner surface of the side walls 2b, 3b, top The protruding length of the side wall portions 4b and 4c from the lower surface of the plate portion 4a is 100 cm.

Any of the following three types is possible between the partial bottom plate portion 2a and the partial bottom plate portion 3a.
(1) The bottom slab 9 is formed of on-site concrete. The illustrated example employs this. Although it takes time to cast and cure the concrete, it is preferable in terms of radiation shielding.
(2) Connect bottom plate members made of precast concrete. Although it is difficult to cope with the change of the interval, it is preferable in terms of rapid construction and radiation shielding.
(3) Ground material (earth and stone) on site. Although it is inferior in terms of radiation shielding, it is preferable in terms of rapid construction and cost reduction.

  As shown in FIGS. 2 and 7, etc., the end panels 5 and 6 used in this embodiment divide a rectangular shape having a size capable of closing the openings at both ends of the box culvert block 1 into a plurality of pieces (for example, 5) and the thickness is the same as that of the side walls 2b, 2c, 4b, 4c (40 to 55 cm). The end panels 5 and 6 are connected to the end box culvert block 1 and stacked from the bottom to close the opening.

  As shown in FIG. 6B, when the precast concrete members are joined to each other, adjacent surfaces F adjacent to each other (specifically, the box culvert block 1 and the box culvert block 1 connected in the length direction). The adjacent surface between the members 1, 2, 3 and the members 1, 2, 3 of the split type box culvert block, the adjacent surface between the box culvert block 1 and the end panels 5, 6) All the gaps G formed between are bent by, for example, fitting of irregularities, in the middle from the inner surface to the outer surface of the member so as not to be in a straight line from the inner surface to the outer surface of the member. As a result, as described above, even if the radiation R is applied to the gap G, it always passes through the concrete portion C and attenuates.

  The water-impervious sheet 7 of the present embodiment is stretched using a sheet fixture 10 as shown in FIGS. That is, a sheet fixture 10 having a metal disk 11 and a heat welding material 12 attached to the surface thereof is anchored to an anchor 13 made of, for example, an internal thread, embedded in a key portion of the inner surface of the box culvert block 1. For example, it is fixed by a bolt 14. As the sheet fixture 10, for example, a trade name “IH disk” manufactured by Akiyamade can be used. The water shielding sheet 7 is welded and fixed to the heat welding material 12.

  The sewage sludge storage facility of the present embodiment is constructed by a method comprising the following steps.

(1) As shown in FIG. 1, the ground 17 at the storage site is excavated, and grooves 18 having the same depth as the thickness of the partial bottom plate portions 2a and 3a are formed at predetermined intervals. In the present embodiment, the bottom surface of the groove 18 is an installation surface.

(2) As shown in FIG. 2, the first side wall member 2 is installed so that the partial bottom plate portion 2a fits into the groove 18, and the second side wall member 3 is installed so that the partial bottom plate portion 3a fits in the same manner. To do. The upper surfaces of the partial bottom plate portions 2 a and 3 a are at the same level as the ground 17. The top plate member 4 is placed on the first side wall member 2 and the second side wall member 3, the side wall portion 4 b is placed on the side wall portion 2 b, and the side wall portion 4 c is placed on the side wall portion 3 b with a known joint (not shown). Join. Thus, one box culvert block 1 can be installed on the installation surface such that the opening faces sideways.
Then, the next box culvert blocks 1 are sequentially arranged in the length direction and installed and assembled in the same manner, and the blocks 1 are connected (joined) in the length direction with a known connector (not shown).
Between the partial bottom plate portion 2a and the partial bottom plate portion 3a, the bottom plate 9 is formed of cast-in-place concrete.
An opening at one end of the connected box culvert block 1 is closed with an end panel 5.

(3) As shown in FIG. 3 and FIG. 4, the sheet fixture 10 in which the water shielding sheet 7 is melted by electromagnetic induction heating performed by pressing the high frequency electromagnetic induction heater 15 through the water shielding sheet 7 for a predetermined time. The box culvert block 1 and the end panel 5 are laid along the inner surface of the heat welding material 12. The water shielding sheets 7 are laid in a watertight manner by welding overlapping portions.

(4) As shown in FIGS. 5 and 6, sewage sludge 25 containing radioactive material contained in a container such as a ton bag is carried into the box culvert block 1 using a transport device 28 such as a forklift. Line up and stack.
(5) As shown in FIGS. 7 and 8, the water shielding sheet 7 is laid in the opening at the other end of the box culvert block 1 and the opening is closed by the end panel 6.

According to Example 1 demonstrated above, the following effect is obtained.
(A) Since the box culvert block 1 and the end panels 5 and 6 are used, it is not necessary to place the concrete on-site, it does not require equipment and labor, and can be constructed in a short construction period, and the cost is low. .
(B) By using the large divided box culvert block 1, the internal capacity can be sufficiently secured.
(C) Since the box culvert block 1 and the end panels 5 and 6 can attenuate the radiation dose with the attenuation performance according to the thickness as described above, sewage sludge containing radioactive substances is shielded from the radiation. Can be stored safely. As described above, since the gap is bent at a location close to the bonding, radiation can be reliably shielded. Moreover, since the box culvert block 1 and the end panels 5 and 6 are robust, sewage sludge containing a radioactive substance can be stored for a long period of time if necessary.
(D) The water-impervious sheet 7 can be separated from the external environment in a watertight manner, and leakage of sewage can be prevented.
(E) Since the box culvert block 1 and the end panels 5 and 6 protect the water shielding sheet 7, even if there is an earthquake or the like, the water shielding sheet 7 is hardly cracked, and the water shielding is maintained.
(F) Since the water-impervious sheet 7 is welded and fixed to the heat welding material 12 of the sheet fixture 10, the water-impervious sheet 7 is not displaced or peeled off even in the event of an earthquake or the like, and is highly reliable.
(G) It is also possible to easily move the sewage sludge at the stage where the final treatment method and the destination of the sewage sludge have been determined.

In addition, this invention is not limited to the structure of the said Example 1, For example, as follows, it can also be changed and embodied suitably in the range which does not deviate from the meaning of invention.
(1) In Example 2 shown in FIG. 9, a box culvert block 1 or the like is installed on the bottom surface of a recess dug in the ground 17 to store a sewage sludge storage facility below the ground, and backfill the soil. It is different from the first embodiment in that a greening layer such as turf is laid so that the upper part of the sewage sludge storage facility can be used as a part of the ground on the site. Others are the same as the first embodiment. It is.

(2) In Embodiment 3 shown in FIG. 10, instead of the box culvert block 1, a U-shaped bottom slab member 22 which is composed of a horizontal bottom slab 22a and two vertical side walls 22b and 22c; A box culvert block 21 is used, which is divided into two in the form of a flat U-shaped top plate member 23 consisting of a horizontal top plate portion 23a and two vertical side wall portions 23b, 23c, which are joined in a box shape. In this respect, the second embodiment is different from the first embodiment, and the others are the same as the first embodiment.

(3) In Example 4 shown in FIG. 11, instead of the box culvert block 1, a U-shaped bottom slab member 32 having a horizontal bottom slab portion 32a and two vertical side wall portions 32b and 32c; The top plate member 33 is formed of a horizontal top plate portion 33a and two vertical side wall portions 33b and 33c. The top plate member 33 is divided into a first side wall member 34 on the left side and a second side wall member 35 on the right side. However, it is different from the first embodiment in that the box culvert block 31 for joining them in a box shape is used, and the rest is the same as the first embodiment.

DESCRIPTION OF SYMBOLS 1 Box culvert block 5 End panel 6 End panel 7 Water shielding sheet 9 Bottom plate 10 Sheet fixture 17 Ground 18 Groove 19 Groove 21 Box culvert block 31 Box culvert block

Claims (1)

  Precast concrete box culvert blocks installed on the installation surface with the openings facing sideways and connected in the length direction, and precast concrete ends closing the openings at both ends of the connected box culvert blocks A facility for storing sewage sludge containing radioactive material, comprising a panel, a box culvert block, and a water shielding sheet laid along the inner surface of the end panel.

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