JP2013057557A - Temporary storage facility for sewage sludge containing radioactive material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a facility capable of temporarily 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 temporary storage facility for sewage sludge comprises: L-shaped retaining wall blocks 1, 2 made of precast concrete that are placed on a mounting surface in two rows so as to form a U shape in a face-up position as a whole by causing back faces to face each other and that are connected in a length direction; end panels 3, 4 made of precast concrete that seal end-face openings created at both ends of the two rows of the L-shaped retaining wall blocks 1, 2 in a connection direction; lid panels 5 made of precast concrete that seal upper-face openings created between upper ends of the two rows of the L-shaped retaining wall blocks 1, 2; and water-impervious sheets 7 laid along inner surfaces of the L-shaped retaining wall blocks 1, 2, the end panels 3, 4, and the lid panels 5.

Description

  The present invention relates to a temporary 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.

  Accordingly, an object of the present invention is to provide a facility capable of temporarily storing sewage sludge containing a radioactive substance while shielding its radiation and storing it for a long period of 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) Temporary storage facilities for sewage sludge containing radioactive substances according to the present invention are installed on the installation surface in two rows so as to form a U-shape with the back facing each other and connected in the longitudinal direction ( L-type retaining wall blocks made of pre-cast concrete, end-panels made of pre-cast concrete that block the end face openings formed at both ends in the connecting direction of the two rows of L-shaped retaining wall blocks, and two rows of L-shaped It consists of a cover panel made of precast concrete that closes the upper surface opening formed between the upper ends of the retaining wall block, and a water shielding sheet laid along the inner surface of the L retaining wall block, the end panel, and the lid panel. Features.

(2) The construction method of the temporary storage facility of the sewage sludge containing the radioactive substance according to the present invention is such that the L-shaped retaining wall blocks made of precast concrete face each other with their backs facing each other to form a U-shape on the back. Installed in two rows on the installation surface and connected in the length direction, closed the end face opening formed at one end in the connecting direction of the two rows of L-shaped retaining wall blocks with an end panel made of precast concrete, and L-shaped retaining wall A first step of laying a water shielding sheet along the inner surface of the block and the end panel;
A second step of carrying sewage sludge containing radioactive material contained in a container into an internal space formed between two rows of L-shaped retaining wall blocks;
A third step of laying a water shielding sheet on the upper surface opening formed between the upper ends of the two rows of L-shaped retaining wall blocks, and then closing the upper surface opening with a lid panel made of precast concrete;
Including a fourth step of laying a water shielding sheet on an end surface opening formed at the other end in the connecting direction of the two rows of L-shaped retaining wall blocks, and then closing the end surface opening with an end panel made of precast concrete. Features.

  In each of the above means, the dimensions of the L-type retaining wall block can be appropriately selected depending on the temporary placement amount, moving / transporting equipment, and the like. However, those having a large height are preferred for the purpose of temporary placement, and specifically those having a height of 3 to 5 m are preferred.

The bottom plate portions of the two rows of L-shaped retaining wall blocks may be abutted on the back end surfaces or may be separated from each other. By changing this distance, the distance between the back surfaces of the vertical wall portions of the two rows of L-shaped retaining wall blocks can be freely set. Any of the following three methods can be used to fill in the separated portion.
(1) Form a bottom slab with cast-in-place concrete. 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.

  Also, the concrete thickness of the L-type retaining wall block, end panel and lid panel (hereinafter simply referred to as “member thickness”) is the radiation weight attenuation performance and the block weight suitable for moving and transporting with actual mobile transport equipment. In view of the balance, it is preferably 10 to 50 cm. 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, two rows of L-shaped holders) that are close to each other (including contact). The back end surfaces of the bottom plate portion of the wall block, the adjacent surface of the L-type retaining wall block and the L-type retaining wall block connected in the length direction, the joint surface between the L-type retaining wall block and the end panel; The gap between the L-type retaining wall block and the cover panel, and the end panel and the cover panel) is all from the inner surface of the member to the outer surface so as not to be in a straight line from the inner surface to the outer surface of the member. It is preferable to bend in the middle. 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 fixture having a heat-welding material on the surface is attached to the L-type retaining wall block and the inner wall of the end panel, and a 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 sewage sludge containing radioactive substances stored in the sewage sludge temporary storage facility of the present invention is not particularly limited, and may be any of dewatered sewage sludge, incinerated ash of incinerated sewage sludge, or 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 on which the L-type retaining wall block is installed may be the ground at the storage site (including the top surface of the foundation concrete that is cast on the ground), or the L-type retaining wall block can be stored below the ground. It may be the bottom of a recess dug in the ground. In the latter case, the upper part of the sewage sludge temporary storage facility can be used as a part of the ground on the site.

  In the means of (2) above, in the second step, a container is placed in the partial space with the tent covering the upper part of the internal space from one end to the other end in the connecting direction. In the third step, the tent is moved from above the partial space toward the other end in the connecting direction, and one of the upper surface openings above the partial space is moved. After the water-impervious sheet is laid in the opening of the part, the partial opening is closed with a lid panel made of precast concrete, and the second step and the third step can be alternately performed in sequence. As a result, it is possible to prevent rain from entering the sewage sludge that has been carried in, thereby preventing the outflow of pollutants due to rainwater.

  When carrying sewage sludge containing radioactive material contained in a container into the internal space, it is the lower part of the internal space and near the center between the vertical wall portions of the two rows of L-shaped retaining wall blocks. Place the sewage sludge containing radioactive material in the container and place it in the container near the upper part of the internal space and the vertical wall of the L-type retaining wall block so as to surround the sewage sludge containing the radioactive substance. Soil that does not contain radioactive material can be placed. With this arrangement, even sewage sludge containing a high concentration of radioactive material can be shielded against radiation by the soil surrounding it, so that combined with shielding by the L-type retaining wall block, higher radiation attenuation Performance can be obtained.

  According to the present invention, sewage sludge containing a radioactive substance can be safely temporarily stored with its radiation shielded, and can 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 temporary placement site | part which excavated the groove | channel in the Example. It is a perspective view which shows the installation step of the block for L type retaining walls and one end panel in the Example. It is a perspective view which shows the completion of installation of the block for L type retaining walls in the 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 block for L type retaining walls in the Example. It is a perspective view which shows the state which carried in sewage sludge in the inside of the block for L type retaining walls in the Example. In the Example, (a) is a front view which shows the example of arrangement | positioning of sewage sludge, (b) (c) 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 temporary storage facility completed in the Example. It is a front view which shows the example of arrangement | positioning of the sewage sludge temporary storage facility and sewage sludge of another Example. The box made from the precast concrete containing a sewage sludge arrange | positioned in another Example is shown, (a) The perspective view which fractured | ruptured partially, (b) is sectional drawing.

  Temporary storage facilities for sewage sludge containing radioactive materials are L-shaped made of precast concrete that is installed in two rows on the installation surface and connected in the length direction so that the back faces face each other and form a U-shape on the back It occurred between the end panels made of precast concrete that block the opening of the end surface generated at both ends in the connecting direction of the retaining wall block, the two rows of L-shaped retaining wall blocks, and the upper end of the two rows of L-shaped retaining wall blocks. It consists of a cover panel made of precast concrete that closes the upper surface opening, and an L-shaped retaining wall block, an end panel, and a water shielding sheet laid along the inner surface of the cover panel.

The method of constructing a sewage sludge temporary storage facility containing radioactive substances is to install L-type retaining wall blocks made of precast concrete on the installation surface in two rows so that their back faces face each other and form a U-shape facing up. The end openings formed at one end in the connecting direction of the two rows of L-shaped retaining wall blocks are closed with an end panel made of precast concrete, and the inner surfaces of the L-shaped retaining wall blocks and the end panels are connected to each other. A first step of laying a water shielding sheet along,
A second step of carrying sewage sludge containing radioactive material contained in a container into an internal space formed between two rows of L-shaped retaining wall blocks;
A third step of laying a water shielding sheet on the upper surface opening formed between the upper ends of the two rows of L-shaped retaining wall blocks, and then closing the upper surface opening with a lid panel made of precast concrete;
Including a fourth step of laying a water shielding sheet on an end surface opening formed at the other end in the connecting direction of the two rows of L-shaped retaining wall blocks, and then closing the end surface opening with an end panel made of precast concrete. Features.

  An embodiment of a sewage sludge temporary storage facility and its construction method embodying the present invention will be described with reference to FIGS.

  The sewage sludge temporary storage facility of this embodiment is an L-shaped support made of precast concrete that is installed in two rows on the installation surface and connected in the length direction so that the back faces face each other and form an overall U-shape. End blocks 3 and 4 made of precast concrete for closing the end openings formed at both ends in the connecting direction of the blocks 1 and 2 for the walls, the two blocks 1 and 2 for the L-shaped retaining walls, and the two rows of the L-shaped retaining walls A precast concrete lid panel 5 that closes the upper surface opening formed between the upper ends of the blocks 1 and 2 and the L-type retaining wall blocks 1 and 2, the end panels 3 and 4, and the inner surface of the lid panel 5. And a water shielding sheet 7.

  As shown in FIG. 2 and the like, the L-type retaining wall blocks 1 and 2 made of precast concrete used in this embodiment are composed of horizontal bottom plate portions 1a and 2a and vertical vertical wall portions 1b and 2b. Reinforcing bars (not shown) are embedded in the bottom plate portions 1a and 2a and the vertical wall portions 1b and 2b. The dimensions of the L-type retaining wall block 1 are exemplified by a height of 5 m, a longitudinal length of 3.25 m, a length of 1 m in the connecting direction, and the thickness of the bottom plate portions 1 a and 2 a gradually decreasing from 35 cm on the front end side. The thickness of the vertical wall portions 1b and 2b is gradually reduced from 35 cm on the lower end side to 12 cm on the upper end side. Therefore, the minimum thickness of the L-type retaining wall blocks 1 and 2 is 12 cm, and the radiation dose can be attenuated by about 75% at that location.

  In the present embodiment, the bottom end portions 1a and 2a of the two rows of L-shaped retaining wall blocks 1 and 2 are abutted on the back end surfaces.

  As shown in FIGS. 2, 8, 9, etc., the end panels 3, 4 used in this embodiment have a rectangular shape with a size that can block the openings at both ends of the L-type retaining wall blocks 1, 2. It is formed into a horizontally-divided strip shape that is divided into a plurality of parts (for example, 5 parts) vertically, and the thickness is the same as the minimum thickness of the L-type retaining wall blocks 1 and 2 (12 cm). The end panels 3 and 4 are connected to the end L-shaped retaining wall blocks 1 and 2 and stacked from the bottom to the top to close the opening.

  The lid panel 5 used in the present embodiment has a rectangular shape having a horizontal length that is the same as the width of the L-type retaining wall blocks 1 and 2 and a private length that can close the upper surface opening, as shown in FIGS. The thickness is the same as the minimum thickness of the L-type retaining wall blocks 1 and 2 (12 cm).

  As shown in FIGS. 7B and 7C, adjacent surfaces F (specifically, bottom plate portions of the L-type retaining wall blocks 1 and 2 in two rows) that are close to each other when joining the precast concrete members. 1a and 2a, L-type retaining wall blocks 1 and 2 and L-shaped retaining wall blocks 1 and 2 connected in the lengthwise direction, L-type retaining wall blocks 1 and 2 and ends The gap G formed between the adjacent surfaces of the panels 3 and 4, the adjacent surfaces of the L-type retaining wall blocks 1 and 2 and the lid panel 5, and the adjacent surfaces of the end panels 3 and 4 and the lid panel 5 are all In order to avoid a straight line from the inner surface to the outer surface of the member, it is bent, for example, by fitting of irregularities in the middle 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 provided with a metal disk 11 and a heat welding material 12 attached to the surface of the anchor 13 made of, for example, an internal thread, embedded in a key portion of the inner surfaces of the L-type retaining wall blocks 1 and 2. The fixture 10 is fixed by, for example, bolts 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 temporary storage facility of the present embodiment is constructed by a method comprising the following steps.

(1) As shown in FIG. 1, the ground 20 of the storage site is excavated shallowly and the foundation concrete 21 is cast in the field, and on the foundation concrete 21 just outside the L-type retaining wall blocks 1 and 2 to be installed later. Two rows of rails 22 are laid.

(2) As shown in FIG. 2, the L-type retaining wall blocks 1 and 2 are placed in two rows on the foundation concrete 21 as the installation surface so that the back faces of the blocks 1 and 2 are opposed to each other. After installation, the back end surfaces of the bottom plate portions 1a and 2a are brought into contact with each other and connected by a known connecting tool (not shown). Further, the L-type retaining wall blocks 1 and 2 are installed and connected (joined) in the length direction with a known connecting tool (not shown).
An end panel 3 closes an end face opening generated at one end in the connecting direction of the two rows of L-shaped retaining wall blocks 1 and 2.

(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 heat welding material 12 is welded and fixed, and laid along the inner surfaces of the L-type retaining wall block 1 and the end panel 3. The water shielding sheets 7 are laid in a watertight manner by welding overlapping portions.

(4) A wheel (not shown) of the tent 23 is placed on the rail 22 so that the tent 23 can be moved in the connecting direction.
As shown in FIG. 3, a tent 23 extends above a partial space from one end to the other end in the connecting direction in the internal space generated between the two rows of L-shaped retaining wall blocks 1 and 2. In the covered state, the sewage sludge 25 placed in a container such as a ton bag is carried into the partial space by using a transport device 28 such as a forklift, and arranged and stacked.
As shown in FIG. 5, the tent 23 is moved from the upper part of the partial space toward the other end in the front coupling direction, and the upper surface opening formed between the upper ends of the two rows of L-shaped retaining wall blocks 1 and 2 After the water shielding sheet 7 is laid in a partial opening above the partial space, the partial opening is closed with a lid panel 5 made of precast concrete.
By alternately performing the steps in FIG. 3 and the steps in FIG. 5 sequentially, as shown in FIG. 6, the sewage sludge 25 can be carried into the other end of the connecting direction in the internal space. According to this procedure, it is possible to prevent rain on the sewage sludge 25 that has been carried in, and thus prevent the pollutant from flowing out due to rain water.

(5) As shown in FIG. 7, the rail 22 and the tent 23 are removed, and as shown in FIGS. 8 and 9, a water shielding sheet is formed at the end face opening generated at the other ends of the L-type retaining wall blocks 1 and 2. 7 is laid and the end face is closed by the end panel 4.

According to the present embodiment described above, the following operational effects can be obtained.
(A) Using the L-type retaining wall blocks 1 and 2, the end panels 3 and 4, and the lid panel 5, only the foundation concrete 21 is required to be cast in the field. Possible and low cost.
(B) By using the L-type retaining wall blocks 1 and 2 having a large height, a sufficient internal capacity can be secured.
(C) Since the radiation dose can be attenuated by the attenuation performance corresponding to the thickness by the L-type retaining wall blocks 1 and 2, the end panels 3 and 4, and the lid panel 5 as described above, sewage containing radioactive substances Sludge can be safely stored with its radiation shielded. As described above, since the gap is bent at a location close to the bonding, radiation can be reliably shielded. Moreover, since the L-type retaining wall blocks 1 and 2, the end panels 3 and 4, and the lid panel 5 are robust, sewage sludge containing a radioactive material 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 L-type retaining wall blocks 1 and 2, the end panels 3 and 4, and the lid panel 5 protect the water shielding sheet 7, the water shielding sheet 7 is hardly cracked even in the event of an earthquake or the like. 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, For example, it can also be suitably changed and embodied as follows in the range which does not deviate from the meaning of invention.
(1) As shown in FIG. 10, the back end surfaces of the bottom plate portions 1 a and 2 a of the two rows of L-shaped retaining wall blocks 1 and 2 are separated from each other, and the bottom plate 9 is formed with cast-in-place concrete at the separated portion. .

(2) As shown in FIG. 10, when the sewage sludge 25 contained in a container such as a ton bag is carried into the internal space, it is the lower part of the internal space and two rows of L-shaped retaining walls The sewage sludge 25 containing the radioactive substance is arranged near the center between the vertical wall portions of the blocks 1 and 2 and the upper part of the internal space and the L-shaped retaining wall so as to surround the sewage sludge 25 containing the radioactive substance The soil 26 which does not contain the radioactive substance put in the bag can be arrange | positioned near the vertical wall part of the block for work. Further, as shown in FIGS. 10 and 11, a box 30 made of precast concrete is formed in the lower part of the internal space and in the center between the vertical wall portions of the two rows of L-shaped retaining wall blocks 1 and 2. It is also possible to arrange the sewage sludge 27 so as to surround the sewage sludge 27 by arranging the sewage sludge 27 containing a high concentration radioactive substance. By these arrangement methods, higher radiation attenuation performance can be obtained as described above.

DESCRIPTION OF SYMBOLS 1 Block for L type retaining wall 1a Bottom plate part 1b Vertical wall part 2 Block for L type retaining wall 2a Bottom plate part 2b Vertical wall part 3 End panel 4 End panel 5 Lid panel 7 Water shielding sheet 9 Bottom plate 10 Sheet fixture 20 Ground 21 Basic concrete 22 Rail 23 Tent 24 Ground material 25 Sewage sludge 26 Soil without radioactive material 27 Sewage sludge 30 Box

Claims (1)

  L-type retaining wall blocks made of precast concrete that are installed on the installation surface and connected in the length direction in two rows so that the back faces face each other to form a U-shape on the back, and two rows of L-type supports An end panel made of precast concrete that closes the end face openings generated at both ends of the connecting direction of the wall block, and a lid panel made of precast concrete that closes the upper face opening formed between the upper ends of the two rows of L-shaped retaining wall blocks; Temporary storage facility for sewage sludge containing radioactive material comprising a block for L-shaped retaining wall, a water shielding sheet laid along the inner surface of the end panel and the lid panel.

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