JP2013011557A - Recovery method of waste body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recovery method of a waste body which can reuse saline water.SOLUTION: In the recovery method of a waste body in which a cushioning material is collapsed by injecting a saline water solution into the cushioning material which surrounds the waste body so as to take out the waste body, a suspension liquid in which the collapsed cushioning material and the saline water solution that has collapsed the cushioning material are mixed is recovered into a primary precipitation tank and is caused to be precipitated naturally in the primary precipitation tank (steps S1 and S2), and a supernatant liquid thereof is used as the saline water solution to be injected into the cushioning material, and therefore, the saline water solution can be reused. Further, since the suspension liquid precipitated in the precipitation tank is subjected to compaction dehydration by a filter press and is recovered (step S4), the amount of the waste body hauled from an underground facility can be minimized.

Description

  The present invention relates to a method for collecting waste, and particularly to a method for collecting waste suitable for removing a cushioning material.

  In geological disposal of high-level radioactive waste, bentonite-based clay material called buffer material surrounds the waste body to buffer the earth pressure from the surrounding area and suppress the intrusion of groundwater. It is considered to suppress leakage of radioactive materials.

  As the buffer material, for example, a bentonite-based soil material in which bentonite and sand are mixed is used, and predetermined elasticity and water impermeability are exhibited by compacting the soil material. The buffer material reduces the external force applied to the waste body when an external force such as an earthquake is applied and the disposal tunnel or the disposal hole is deformed, and suppresses intrusion of groundwater and leakage of radioactive substances.

  By the way, in order to actually implement the disposal of waste, it is necessary to obtain a social agreement on the appropriateness of the disposal in consideration of ethical, political and economic factors. For this purpose, in order to ensure the reversibility of the business plan, it is necessary to secure a technology that allows the waste to be taken out and collected at any time.

  In order to take out and collect the waste body, it is necessary to remove the buffer material surrounding the waste body prior to the operation of taking out the waste body. As one of the methods, for example, an electrolyte solution (salt water) is injected. Thus, a buffer material removal method for collapsing the buffer material and taking out the slurry as a fluid has been proposed (for example, see Non-Patent Document 1).

  The method of removing the slurry of the buffer material by injecting the electrolyte solution as a fluid is easy to operate remotely, and has the merit that there is less concern about damaging the waste compared to the mechanical removal method. However, if the electrolyte solution is not reused, a large amount of slurry is generated, so the slurry is dehydrated and reduced by a centrifuge and transported as solid waste, and the salt water after solid-liquid separation is jetted. It is considered to be reused.

Nakajima Hitoshi et al. "Buffer material removal technology using salt water for waste recovery" Annual Conference of the Japan Society of Civil Engineers (CD-ROM), August 5, 2010, 65th CS7-032, p. . 63-64

  However, since bentonite has many fine particle components that cannot be separated efficiently in a short time by a centrifuge, fine clay minerals remain in the electrolyte solution to be reused. For example, FIG. 16 shows the particle size range of a solid phase contained in a suspension to which a dehydrating apparatus such as a centrifugal separator can be applied. The particle size distribution of a viscous mineral called montmorillonite, which is the main component of bentonite, is seen. In addition, since about 40% of particles having a size of 1 μm or less are contained, it is difficult to perform efficient dehydration.

  In addition, as a method for efficiently performing dehydration, there is a method of increasing the particle size by adding a flocculant to facilitate solid-liquid separation. However, since the flocculant component increases in the electrolyte solution to be reused, the electrolyte solution There is a problem in safety management that it is impossible to maintain a constant component. Thus, if possible, it is desirable to precipitate the solid phase in the electrolyte solution without adding a flocculant, further accelerate the dehydration and reduce the volume, and then carry it out from the underground tunnel to the ground.

  This invention is made | formed in view of the above, Comprising: It aims at providing the collection | recovery method of the waste body which can recycle electrolyte solution.

  In order to solve the above-described problems and achieve the object, the present invention relates to a method for recovering a waste body in which the buffer material is collapsed and the waste body is taken out by spraying an electrolyte solution onto the buffer material surrounding the waste body. In addition, the primary precipitation tank is used as an electrolyte solution for spontaneously precipitating a suspension in which a buffer material that has collapsed and an electrolyte solution that has disrupted the buffer material is mixed in a primary precipitation tank, and jetting the supernatant liquid onto the buffer material. It is characterized in that the precipitate naturally precipitated in step 1 is transferred to a secondary dewatering tank and dehydrated by a filter press.

  In the invention described above, the present invention is characterized in that the filter used in the filter press is a polymer filter having fine pores.

  Further, the present invention is characterized in that, in the above-mentioned invention, the load used for the filter press is obtained from a loaded stone or a compressed air pressure.

  Further, the present invention is characterized in that, in the above-mentioned invention, after the dehydration process is completed, the filter press device is removed, and then the secondary dehydration tank sealed with a lid is directly carried out of the facility.

  Further, the present invention is characterized in that, in the above-mentioned invention, the electrolyte solution recovered by the dehydration treatment is used as an electrolyte solution for injecting the buffer material.

  The waste body recovery method according to the present invention is used as an electrolyte solution for precipitating a suspension in which a disintegrated buffer material and an electrolyte solution in which the buffer material is disintegrated are mixed, and jetting the supernatant liquid onto the buffer material. The electrolyte solution can be reused.

FIG. 1 is a conceptual diagram showing a radioactive waste burying / disposal facility adopting a vertical waste disposal system. FIG. 2 is a conceptual diagram showing a radioactive waste burying / disposal facility adopting a horizontal disposal system. FIG. 3 is a conceptual diagram showing a waste collection device. FIG. 4 is an enlarged view showing the solid-liquid separator shown in FIG. FIG. 5 is a flowchart showing a solid-liquid separation processing procedure in the solid-liquid separation apparatus. FIG. 6 is a diagram for explaining the filter press process. FIG. 7 is a conceptual diagram showing the contents and procedure of the performance confirmation experiment of the solid-liquid separator. FIG. 8 is a diagram showing the results of the performance confirmation experiment of the solid-liquid separator in numerical values. FIG. 9 is a graph showing the results of the performance confirmation experiment of the solid-liquid separator, in which the dehydration / volume reduction time is up to 30 hours. FIG. 10 is a graph showing the results of the performance confirmation experiment of the solid-liquid separator, and the dehydration / volume reduction time is up to 10 hours. FIG. 11 is a diagram showing the results of the performance confirmation experiment of the solid-liquid separator, and numerically shows the dehydration tendency of the precipitate when the filter is pressed after precipitation and the dehydration tendency when the filter is pressed without precipitation. It is a figure shown by. FIG. 12 is a diagram showing the results of the performance confirmation experiment of the solid-liquid separator, and is a graph showing the dehydration tendency of the precipitate when the filter is pressed after precipitation and the dehydration tendency when the filter is pressed without precipitation. It is a figure shown by. FIG. 13 is a conceptual diagram showing the specifications of a radioactive waste burying / disposal facility adopting a vertical waste disposal system. FIG. 14 is a diagram showing an example of a filter press that divides a precipitate into a plurality of times and puts it into a secondary dewatering tank and carry-out container. FIG. 15 is a view showing another example of a filter press that divides a precipitate into a plurality of times and puts it into a secondary dewatering tank and carry-out container. FIG. 16 is a diagram showing a particle size range of a solid phase contained in a suspension to which a dehydration device such as a centrifuge can be applied.

  Hereinafter, embodiments of a method for collecting waste according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  First, based on FIG. 1 and FIG. 2, a radioactive waste embedding disposal facility to which a waste body recovery method according to an embodiment of the present invention is applied will be described. FIG. 1 is a conceptual diagram showing a radioactive waste embedding disposal facility adopting a vertical waste disposal system, and FIG. 2 is a concept showing a radioactive waste embedding disposal facility adopting a horizontal waste disposal system. FIG.

  As shown in FIG. 1 and FIG. 2, the radioactive waste burying disposal facility is a facility for enclosing radioactive waste solidified with glass (glass solidified body) in a metal container and buried deep underground. In addition, access tunnels and communication for transporting waste materials (contained in solid metal containers or encased in thick metal overpacks) P and construction materials from ground facilities It is composed of a mine shaft, a main mine shaft A, a disposal mine shaft G for disposing a waste body P, a disposal hole H, or the like.

  The waste P is placed in a vertical arrangement method (see Fig. 1), in which the disposal holes H are drilled vertically downward from the floor of the disposal tunnel G at regular intervals, and the waste P is placed there. There are two types of waste horizontal placement methods (see FIG. 2) in which the waste P is placed directly in the mine shaft G.

  As shown in FIG. 1, the waste body vertical placement system is a system in which the inside of the disposal hole is filled with the waste body P and the buffer material B, and is buffered between the disposal hole H and the waste body P. Material B is arranged. On the other hand, as shown in FIG. 2, the waste horizontal placement system is a system in which the inside of the disposal tunnel is filled with the waste body P and the buffer material B, and is disposed between the disposal tunnel G and the waste body P. The shock absorbing material B is arrange | positioned.

  As the buffer material B, for example, a bentonite-based soil material in which bentonite and sand are mixed is used, and when the buffer material B is densified by compaction or the like, predetermined elasticity and water shielding properties are exhibited. And the buffer material B reduces the external force added to the waste body P when external force, such as an earthquake, is added and the disposal mine G and the disposal hole H deform | transform, and prevents the penetration | invasion of groundwater.

  Next, based on FIG. 3 and FIG. 4, a waste collection method according to an embodiment of the present invention will be described. FIG. 3 is a conceptual diagram showing a waste body recovery device, and FIG. 4 is an enlarged view showing the solid-liquid separation device shown in FIG.

  Here, an explanation will be given by taking as an example a waste recovery device used in a radioactive waste embedding disposal facility that employs a horizontal waste disposal system. As shown in FIG. 3, the waste body recovery device (hereinafter referred to as “recovery device”) 1 is for removing and recovering the compacted buffer material B surrounding the waste body P. The electrolyte solution Is sprayed onto the buffer material B compacted to a high density, the buffer material B compacted to a high density is collapsed, and the collapsed buffer material is removed and recovered. The electrolyte solution sprayed onto the buffer material B compacted at high density may be any of inorganic electrolyte aqueous solutions such as salt water (sodium chloride aqueous solution), potassium chloride aqueous solution, and calcium chloride aqueous solution. In this form, salt water is used.

  As described above, the recovery device 1 injects the salt water into the buffer material B compacted with high density, the traveling device 2 that travels through the disposal mine tunnel G, the nozzle head 4 to which the injection nozzle 3 is attached, A handling device 5 that is mounted between the traveling device 2 and the nozzle head 4 and moves the nozzle head 4 to an arbitrary position and tilts the nozzle head 4 in an arbitrary direction, and a discharge pump that injects salt water from the injection nozzle 3 6 and a dam plate device 7 for damming the suspension S mixed with the shock absorbing material B disintegrated in the salt water jetted from the jet nozzle 3, and the suspension S blocked by the dam plate device 7 And a solid-liquid separation device 8 for separating the components.

  The traveling device 2 is for traveling the disposal mine tunnel G as described above, and travels on a floor surface curved in a circular arc shape of the disposal mine shaft formed in a cylindrical shape. The traveling device 2 of the collection device 1 is a crawler-type traveling device, and can be operated in an arbitrary direction by an operation from a remote controller (not shown) or a driver's seat 21 provided in the rear area of the traveling device 2. It is possible to run at speed. Further, the traveling device 2 of the recovery device 1 can move the nozzle head 4 to an arbitrary position in the depth direction inside the disposal tunnel G by cooperating with the handling device 5 described above. The traveling device 2 is not limited to the crawler-type traveling device, and may be a wheel-type traveling device, for example.

  As described above, the injection nozzle 3 is attached to the nozzle head 4. The injection nozzle 3 is for injecting salt water onto the buffer material B compacted with high density. The salt water pumped from the discharge pump 6 increases in pressure by passing through the injection nozzle 3 and is injected from the injection nozzle 3. To do.

  The number of spray nozzles 3 to be mounted on the nozzle head 4 is not limited to one, and a plurality of spray nozzles 3 can be mounted at arbitrary positions in consideration of the removal efficiency of the buffer material B. is there.

  As described above, the handling device 5 is attached between the traveling device 2 and the nozzle head 4 to move the nozzle head 4 to an arbitrary position and tilt the nozzle head 4 in an arbitrary direction. It is constituted by an articulated type handling device.

  The handling device 5 includes a handling boom 51 and a handling arm 52. The handling boom 51 and the handling arm 52 are components for moving the nozzle head 4 to an arbitrary position. The handling boom 51 and the traveling device 2, the handling boom 51 and the handling arm 52, and the handling arm 52 and the nozzle head 4. Constitutes the joint of the handling device 5.

  That is, one end portion (base end portion) of the handling boom 51 is rotatably attached to the traveling device 2, and the other end portion (tip portion) of the handling boom 51 is the middle of the traveling device 2 and the handling boom 51. It can be moved to an arbitrary position by a hydraulic cylinder 53 installed between the two. Further, one end portion (base end portion) of the handling arm 52 is rotatably attached to the distal end portion of the handling boom 51, and the other end portion (leading end portion) of the handling arm 52 is the distal end portion of the handling boom 51. And a hydraulic cylinder 54 installed between the middle of the handling arm 52 and the handling arm 52 can be moved to an arbitrary position. Furthermore, the nozzle head 4 is rotatably attached to the tip of the handling arm 52, and the nozzle head 4 can be tilted in an arbitrary direction by an actuator (for example, a hydraulic cylinder) (not shown).

  The discharge pump 6 is for injecting salt water from the injection nozzle 3 as described above, and is installed in the main tunnel A. The discharge pump 6 includes a salt water storage tank 61 that stores salt water. The salt water stored in the salt water storage tank 61 is pumped up and injected from the injection nozzle 3.

  As described above, the weir plate device 7 is a device for damming the suspension (slurry) S in which the shock absorbing material mixed with the salt water sprayed from the spray nozzle 3 is mixed, and is attached to the front area of the traveling device 2. It is. The dam plate device 7 includes a dam plate 71 and a support arm 72 that supports the dam plate 71. The dam plate 71 is used for damming the suspension S in which the buffer material B collapsed into the salt water jetted from the jet nozzle 3 is mixed, and the floor of the disposal tunnel G formed in a cylindrical shape is curved in an arc shape. It is formed in a semi-disc shape that matches the lower half of the cross section of the disposal tunnel G so as to be in close contact with the surface.

  Further, the weir plate 71 can be moved up and down by an actuator (not shown) (for example, a hydraulic cylinder), and the recovery device 1 can travel by the traveling device 2 with the weir plate 71 raised, and the traveling device 2 stops. In this state, the weir plate 71 can be lowered. And when the weir plate 71 descend | falls, the weir plate 71 closely_contact | adheres to the floor surface of the disposal tunnel G, and the lower half of the disposal tunnel G is blocked. Thereby, the dam plate 71 dams the suspension S in which the shock absorbing material B mixed with the salt water sprayed from the spray nozzle 3 is mixed. Suspended suspension S has a solid phase concentration of 5 to 10% (moisture content ratio of 1900 to 900%), and with this state, suspension S having a weight 10 to 20 times that of buffer material B is carried out. Will have to.

  As described above, the solid-liquid separation device 8 is a device for recovering the suspension S blocked by the barrier plate device 7 and separating salt water, and is installed in the main tunnel A. The solid-liquid separation device 8 aims to reduce the volume until the water content ratio of the solid phase (soil material) after separation is 100%, that is, about twice the weight of the buffer material B to be removed and collected.

  As shown in FIG. 4, the solid-liquid separator 8 stores a sludge pump (not shown) and the suspension S collected by the sludge pump, and naturally precipitates the soil material contained in the suspension S. A primary settling tank 81 and a filter press processing apparatus (not shown) for receiving a soil material (precipitate) naturally precipitated in the primary settling tank 81 in a secondary dewatering tank / carrying-out container (filter press tank) 82 for further dehydration treatment. And.

  The sludge pump is for recovering the suspension S blocked by the dam device 7 in the primary sedimentation tank 81, and is provided between the dam plate device 7 and the primary sedimentation tank 81. The sludge pump and the primary sedimentation tank 81 are connected by a hose 81a.

  As described above, the primary sedimentation tank 81 is for storing the suspension S collected by the sludge pump, and for naturally sedimenting the soil material contained in the suspension S, and is limited to one. There are not a plurality of suspensions S to be collected. In the primary sedimentation tank 81, when a suspension S (water content ratio of 1900 to 900%) having a solid phase concentration of 5 to 10% is stored for about 1 hour, about half of the suspension S becomes a supernatant and the other half Becomes a precipitate (high concentration suspension). This supernatant is recovered in the salt water storage tank 61 and reused. On the other hand, the precipitate is further transferred to the secondary dehydration tank and carry-out container 82 and further dehydrated (volume reduction) by the filter press processing apparatus.

  As described above, the filter press processing apparatus is for receiving the sediment that has spontaneously settled in the secondary dewatering tank and carry-out container 82 for further dewatering treatment. And a press part (not shown) for applying

  As described above, the secondary dewatering tank and carry-out container 82 is a container for receiving the sediment that has spontaneously precipitated in the primary sedimentation tank 81, and is not limited to one, depending on the amount of the sediment to be received. Several are provided. The secondary dewatering tank / carrying container 82 has the same shape as the drum can, and is raised by a raising collar 83 having substantially the same cross section as the secondary dehydrating tank / carrying container 82. And accept the deposit.

  The filter unit is for dehydrating and reducing the sediment received in the secondary dewatering tank and carry-out container 82, and is inserted into the raising collar 83 from the upper part of the raising collar 83. The filter part is a frame (filter body) (not shown) with a filter (filter medium) (not shown) stretched, and the filter stretched on the frame is composed of a polymer pore diameter film. Prevent clogging due to sediment (soil material).

  As described above, the press portion applies a load to the filter portion, and here, a pre-prepared weight (not shown) is loaded on the filter portion.

  In the radioactive waste embedding disposal facility adopting the waste horizontal placement method described above, when the buffer material B compacted with high density is removed and collected, first, traveling with the nozzle head 4 and the handling device 5 attached thereto. The apparatus 2 is carried into the disposal tunnel G, and the discharge pump 6 and the solid-liquid separator 8 are installed in the main tunnel A. Thereafter, the recovery device 1 travels along the disposal tunnel G using the traveling device 2 and moves until the injection nozzle 3 approaches the buffer material B to be removed and recovered. Next, the collection device 1 lowers the weir plate 71 using the weir plate device 7 and blocks the lower half of the disposal mine shaft G.

  Next, the collection device 1 moves the nozzle head 4 to an arbitrary position using the handling device 5 and tilts the nozzle head 4 in an arbitrary direction. In the method for recovering the waste body P according to the embodiment of the present invention, the nozzle head 4 is moved and the nozzle head so that the salt water sprayed from the spray nozzle 3 hits the buffer material B located near the ceiling surface of the disposal tunnel G. Tilt 4

  Next, the recovery device 1 pumps the salt water from the salt water storage tank 61 using the discharge pump 6 and injects the salt water from the injection nozzle 3 toward the buffer material B. And the salt water sprayed to the buffer material B reduces the caking property of the buffer material B, and makes the buffer material B collapse. Due to the collapse of the buffer material B, a dent may be formed in the buffer material B located near the disposal tunnel G, and the suspension S in which the buffer material collapsed into salt water or salt water may accumulate. Thus, when the suspension S mixed with the salt water or the buffer material B disintegrated in the salt water is accumulated in the recess made in the buffer material B, the caking property of the buffer material B is further reduced, and the buffer material B is collapsed. Will be promoted. Then, the buffer material B is gradually collapsed from the near side toward the back side, and then the buffer material B is gradually collapsed from the upper side toward the lower side. At this time, the indented portion where the suspension S has accumulated has reduced caking properties, so that it is relatively easily disintegrated when salt water is injected.

  Then, the suspension S in which the buffer material B disintegrated in salt water is mixed is finally dammed up by the dam plate 71. The suspension S blocked by the barrier plate 71 reduces the caking property of the buffer material B that has not collapsed, and promotes the collapse of the buffer material B.

  As described above, the suspension S blocked by the barrier plate device 7 is sent to the solid-liquid separation device 8 to be separated into a liquid layer (salt water) and a solid phase (soil material).

  Based on FIG. 5 and FIG. 6, the solid-liquid separation process in the solid-liquid separation device will be specifically described. FIG. 5 is a flowchart showing a solid-liquid separation processing procedure in the solid-liquid separation device, and FIG. 6 is a diagram for explaining the filter press processing.

  The suspension S blocked by the weir plate device 7 is collected and stored in the primary sedimentation tank 81 by the sludge pump (step S1). When the suspension is stored in the primary sedimentation tank 81 for about 1 to 2 hours, about half of the suspension S becomes a supernatant and the other half is naturally precipitated (step S2). This supernatant is recovered in the salt water storage tank 61 and reused. On the other hand, the sediment naturally precipitated in the primary sedimentation tank 81 is transferred to the secondary dehydration tank and carry-out container 82 and further dehydrated by the filter press processing apparatus.

  In the filter press processing apparatus, first, the sediment D naturally precipitated in the primary sedimentation tank 81 is received in the secondary dewatering tank and carry-out container 82 raised by the raising collar 83 (step S3). Next, the filter portion 84 is inserted into the inside of the raised collar 83 from above the raised collar 83 (see FIG. 6A), and a load is applied to the filter portion 84 at the press portion 85 (see FIG. 6B). ). The press unit 85 is made of, for example, heavy stone. When a certain amount of time is loaded on the filter unit 84 and a predetermined time has elapsed, the precipitate D is dehydrated and reduced in volume as shown in FIG. The volume of D is reduced to an amount that can be accommodated in the secondary dewatering tank and carry-out container 82 (step S4). Thereby, the reduced sediment D is accommodated in the secondary dewatering tank and carry-out container 82, and the supernatant liquid (salt water) L remains in the raised collar 83 (step S5). Note that the press portion 85 may be loaded using compressed air pressure or hydraulic pressure instead of the above-described weight.

  As shown in FIG. 6 (d), the supernatant L remaining in the raising collar 83 is collected in the salt water storage tank 61 and reused. On the other hand, the secondary dewatering tank / carrying container 82 containing the reduced sediment D is removed from the raising collar 83 and covered with a cover tunnel from the main tunnel A, as shown in FIG. It is carried out of the facility through the tunnel (step S6). Thus, when the buffer material B is removed and collected, the waste body P is exposed and the waste body P can be collected.

  Since the recovery device 1 described above separates the suspension S into a supernatant (salt water) and a soil material (dehydrated and reduced sediment) by the solid-liquid separation device 8, the moisture contained in the soil material to be carried out. (Salt water) can be reduced. Further, since the salt water contained in the suspension S is reused, the amount of salt water that becomes waste is reduced, and the energy required for carrying out the waste can be reduced.

  Further, since the volume of the suspension S is reduced to about half in the primary precipitation tank 81, the volume of the suspension (precipitate) to be dehydrated by the filter press processing apparatus can be reduced.

  In addition, although a heavy stone is loaded on the filter unit 84 in the press unit 85 of the filter press processing apparatus, when loading a heavy stone on the filter unit 84, it is not necessary to replenish energy in order to consolidate the precipitate D, and storage. If space can be secured, it is possible to dehydrate for several hours to several days.

  Further, when the pressure applied in the press section 85 of the filter press processing apparatus is 12 kPa or more as will be described later, the water content can be reduced to about 80%.

  Moreover, since the filter of the filter part 84 of the filter press processing apparatus is composed of a polymer pore film, fine particles such as montmorillonite contained in the bentonite-based soil material can be removed. Therefore, fine particles such as montmorillonite do not remain in the separated salt water, and the viscosity of the salt water does not increase. Thereby, the efficiency of the discharge pump 6 can be maintained.

  In the filter press processing apparatus, since the supernatant liquid (salt water) L is separated from the precipitate D in the secondary dehydration tank / carrying container 82, it is necessary to provide a filter press processing tank in addition to the secondary dehydration tank / carrying container 82. There is no.

  Although the secondary dewatering tank and carry-out container 82 used in the above-described filter press processing apparatus is raised by the raising collar 83, the precipitate D is added to the amount substantially equal to the capacity of the secondary dehydration tank and carry-out container 82. If the volume is reduced, it will be easier to cover. In consideration of this, it is preferable to adopt a structure in which the lower end portion of the raising collar 83 is fitted into the secondary dewatering tank and carry-out container 82. As described above, when the lower end portion of the raising collar 83 is fitted into the secondary dewatering tank and carry-out container 82, the dehydrated and reduced sediment D overflows from the secondary dehydration tank and carry-out container 82. Can be prevented. The liquid phase (salt water) generated by the dehydration does not leak from between the secondary dewatering tank and carry-out container 82 and the raising collar 83 by vacuum drainage.

  Further, although the heavy stone is shown as an example of the press unit 85 of the filter press processing apparatus, the press unit 85 is not limited to the heavy stone, and may be a press device using compressed air or hydraulic pressure as a driving source.

  In the method for recovering the waste body P according to the above-described embodiment, when the suspension S is dehydrated with an existing filter press apparatus, the filter is clogged with the fine particles of the suspension S, and the press speed and the dehydration speed are reduced. Due to inconsistencies, the sediment may leak from between the secondary dewatering tank and carry-out container 82 and the filter unit. In consideration of this, it is required that the filter is not easily clogged with the fine particle component of the precipitate D, and that the press speed is slow so that the press speed matches the dewatering speed.

  Further, in order to eliminate the clogging of the filter, the suspension S is added with a flocculant (for example, polyaluminum chloride (PAC) [Al2 (OH) nCl6-n] m (1 ≦ n ≦ 5, m ≦ 10)). Although it is possible to add the flocculant to the salt water to be reused, thorough examination is required.

  Although it is possible to apply a centrifuge to the solid-liquid separator 8, the liquid phase (salt water) separated by the centrifuge retains montmorillonite fine particles, so that the viscosity of the liquid phase increases. The efficiency of spraying from the spray nozzle 3 is reduced. It is possible to remove the montmorillonite fine particles from the separated liquid phase by adding the flocculant to the suspension S and then dehydrating with a centrifuge, but the flocculant is mixed in the liquid phase to be reused. Therefore, sufficient examination is necessary.

  Based on the above, since the performance confirmation experiment of the solid-liquid separation apparatus mentioned above was implemented, first, the content and result of the performance confirmation experiment of a solid-liquid separation apparatus are demonstrated based on FIGS. FIG. 7 is a conceptual diagram showing the outline and procedure of the performance confirmation experiment of the solid-liquid separator. Moreover, FIGS. 8-12 is a figure which shows an experimental result.

  In this experiment, a 2000 mL graduated cylinder is used for the primary sedimentation tank. In addition, as an initial state suspension (suspension dammed to the weir plate), solid phase 100 g (bentonite (Kunigel V1): 70 g, silica sand No. 3 & No. 5: 30 g mixed material), liquid phase 900 g A mixed solution (suspension) having a water content of 900% and a solid phase concentration of 10% in the slurry is used.

Moreover, a polymer filter membrane (microporous polypropylene film filter paper) is used for the filter used in the filter portion of the filter press apparatus. The polymer filter membrane used here has a film thickness of 25 μm, an area factor of 0.0852 m ² / g, a porosity of 45%, a density of 0.49 Mg / m ³ , and a pore diameter of 0.04 μm × 0.4 μm. belongs to.

  Moreover, the press part of the filter press apparatus uses a heavy stone, and applies a load of 30N or 60N.

  In the experiment, the suspension that spontaneously precipitated by storing in the primary sedimentation tank (measuring cylinder) for 1 hour or 2 hours is transferred to the secondary dehydration tank and carry-out container for 2 batches, and then 30N or 60N of cobble stones in the filter section. The load is loaded and separated into a liquid phase (salt water) and a solid phase (soil material).

  In the experimental procedure shown in FIG. 7, first, two suspensions (slurries) with a water content of 900% are prepared. As described above, the solid phase material constituting the suspension is a mixed material of 70% bentonite (Kunigel V1) and 30% silica sand, and the liquid phase material is 4 wt% salt water. A suspension is prepared by mechanically stirring 100 g of the solid phase and 900 g of the liquid phase for 1 minute.

  This suspension is naturally precipitated in a primary sedimentation tank (measuring cylinder) as a suspension generated by salt water injection (a suspension suspended by a weir plate). There are two cases of spontaneous precipitation (standby time): 1 hour and 2 hours. If the inner diameter of the primary sedimentation tank (measuring cylinder) is 88 mm, the liquid depth of the suspension is 155 mm.

  After 1 hour, the suspension spontaneously settles to about half, so the supernatant (brine) is removed. When the time for natural precipitation is 2 hours, the supernatant liquid (salt water) is removed in two steps, after 1 hour and after 2 hours.

  The precipitate (suspension) from which the supernatant has been removed in this way becomes a high-concentration suspension.

  Next, the sediment (high-concentration suspension) that naturally settled in the primary sedimentation tank (measuring cylinder) is transferred to the secondary dehydration tank and carry-out container (filter press tank), and the filter press (consolidation) is performed at a constant pressure. To do. The constant pressure is two cases of 6 kPa and 12 kPa. Then, the liquid (salt water) separated on the filter is removed when a certain time has elapsed, and the weight of the suspension is measured. If the inner diameter of the secondary dewatering tank and carry-out container (filter press tank) is 80 mm, the liquid depth of the suspension with a water content of 300% is about 13 cm, and the liquid depth of the suspension with a water content of 250% is about 12 cm.

  As shown in FIG. 8, when the suspension is naturally precipitated in the primary sedimentation tank, the suspension having an initial water content ratio of 900% is reduced to a water content ratio of 300% after 1 hour. The volume is reduced to 250% over time. From this, it can be seen that the time required for natural precipitation (precipitation time) is sufficient for one hour, and about half of the injected salt water can be reused within one hour.

  The precipitate (high-concentration suspension) naturally precipitated in the primary precipitation tank for 1 hour or 2 hours is in a slurry state having fluidity. Thereby, a deposit can be moved from a primary sedimentation tank to a secondary dehydration tank and carry-out container (filter press tank).

  As shown in FIG. 9, when the precipitate (high concentration suspension) naturally precipitated for 1 to 2 hours in the primary sedimentation tank is filter-pressed, the volume reduction rate is higher than the continuous natural precipitation in the primary sedimentation tank. Get faster. For example, if the natural precipitation is continued in the primary sedimentation tank, the volume is reduced to a water content ratio of 155% after 20 hours. , 12 kPa), the volume is reduced to the same water content in 3 to 4 hours (see FIG. 8).

  In addition, as shown in FIG. 10, in the range where the total volume reduction time is within 6 hours, paying attention to the time until the predetermined water content is reached, the settling time in the primary settling tank is 2 hours compared to 1 hour. It takes longer in the case of. Therefore, it is preferable to transfer the sediment which has been naturally precipitated by setting the sedimentation time in the primary sedimentation tank to about 1 hour to the secondary dehydration tank and carry-out container (filter press tank).

  As shown in FIG. 9, when the pressure of the filter press is 12 ka, the water content ratio is about 80% in 8 hours. This volume reduction is a degree of dehydration equivalent to the degree of dehydration by a centrifuge, and is smaller than a standard water content ratio of 100%.

  Moreover, as shown in FIG. 11 and FIG. 12, the dehydration tendency of the precipitate when filter-pressed after naturally precipitating for 2 hours in the primary sedimentation tank and the same degree of precipitate as the natural sediment for 2 hours in the primary sedimentation tank The dehydration tendencies of the suspensions were compared when the suspensions were directly filtered without causing the water content suspensions to spontaneously settle in the primary sedimentation tank. In the examples shown in FIG. 11 and FIG. 12, the water content ratio of the precipitate and the water content ratio of the suspension do not completely match, so a simple comparison cannot be made. In this case, the dehydration rate tends to be faster.

  The cause is considered to be that fine particles remain in the supernatant liquid after spontaneous precipitation, and the presence or absence of the fine particles affected subsequent clogging of the filter. If it thinks so, dehydration efficiency will be better to carry out the filter press after carrying out the natural precipitation in a primary settling tank rather than carrying out the filter press directly without carrying out the natural precipitation in a primary settling tank.

  On the other hand, if fine particles remain in the supernatant after spontaneous precipitation, there is a concern that by repeatedly using the supernatant, the solid phase components (fine particles) of the supernatant (brine) gradually increase and the viscosity increases. Therefore, the supernatant was repeatedly used 10 times, and the supernatant was sampled each time, but there was no tendency to increase the concentration of the solid phase (fine particles). Therefore, it is not necessary to consider that the viscosity of the supernatant liquid (salt water) increases due to repeated use of the supernatant liquid and the viscosity increases.

  Next, the practicality of the solid-liquid separator is verified based on the experimental results of the performance confirmation experiment of the solid-liquid separator described above.

  The secondary dewatering tank and carry-out container (filter press tank) actually used is assumed to have an inner diameter of 600 mm and a depth of 1500 mm. When filter pressing is performed in the secondary dewatering tank and carry-out container, it is assumed that the time required for volume reduction becomes longer. However, since it is possible to prepare multiple secondary dewatering tanks and carry-out containers and perform filter presses in parallel, the time required for volume reduction does not become a big problem. If this is the case, the advantage of ensuring that the water content is 100% or less is greater.

  Based on FIG. 13, the amount of cushioning material actually assumed is considered. FIG. 13 is a conceptual diagram showing the specifications of a radioactive waste burying / disposal facility adopting a vertical waste disposal system. As shown in FIG. 13, the amount of the cushioning material to be removed and collected is about 24 tons in terms of dry weight. This is calculated | required by the volume of the buffer material which surrounds a waste body and a waste body, the volume of a waste body, and a dry density.

The volume V1 of the cushioning material surrounding the waste and the waste is
V1 = 1.11 × 1.11 × 3.1415 × 4.13 = 15.99 m ³ and
The volume V2 of the waste body is
V2 = 0.41 × 0.41 × 3.1415 × 1.73 = 0.91 m ³ (volume of waste).
And the amount of cushioning material to be removed and recovered is
It is (15.9-0.91) * 1.6 = 24.128 ton (dry weight).

Moreover, it is 164 when converted into the actual number of secondary dewatering tanks and carry-out containers (200 L drums).
This is converted at a moisture content of 100%.
The dry density ρ of a buffer material (dehydrated cake) with a water content of 100% is
ρ = 1 / (1 / 2.778 + 1/1) = 0.735 kg / L,
The weight W of the cushioning material carried out by the secondary dewatering tank and carry-out container (200 L drum can) is:
W = 200 × 0.735 = 147 kg / book.
And the number of necessary secondary dehydration tank and carry-out containers (200L drums) is
24128 kg ÷ 147 kg = 164.

It takes a long time to remove 24 tons of buffer material by salt water injection. For example, assuming that the removal rate of the buffer material is 10 kg / min, about 5 days are required.
24128 kg / 10 kg / min = 2413 min = 40 hours = 8 hours / day × 5 days

  Thus, since it takes about one week to remove the buffer material, it is considered that there is no problem if 164 secondary dewatering tanks and carry-out containers (drums) are left in the main tunnel for about one week. . Therefore, it becomes a standard to dehydrate the buffer material in 5 days.

  Furthermore, in order to reduce the volume of the precipitate (solid phase) in a short time, it is conceivable to perform filter press while replenishing the precipitate in stages. The liquid layer (salt water) separated from the precipitate by the filter press passes through the filter and becomes a supernatant. As a result, the volume of sediment (dehydrated cake) decreased as the volume decreased, and the density of the precipitate (dehydrated cake) increased, so the permeability (separability) of the liquid layer (salt water) was geometric. It becomes smaller in series. As a result, the dehydration rate becomes slow, but improvement is possible by adopting the following two items.

  The first is to prevent the entry of the precipitate (bentonite-based soil material) into the filter and clogging by using a polymer pore diameter film for the filter. The polymer thin film is effective in that it is less likely to be clogged than a fiber material such as a nonwoven fabric. Moreover, when a polymer pore size film is used, the precipitate (dehydrated cake) does not adhere to the filter, and the filter is removed from the precipitate (dehydrated cake) that has been dehydrated and increased in density simply by raising the filter part. Can be separated. In addition, if a filter made of a polymer film with a pore size that can remove fine particles such as montmorillonite is used, fine viscosity minerals (montmorillonite) will not remain in the liquid layer (brine), so the liquid layer (brine ) Does not increase, and the liquid layer (salt water) can be easily reused.

  The second is to divide the precipitate to be put into the secondary dewatering tank and carry-out container (filter press tank) into small portions and to add it in multiple times. If the precipitate is divided into small portions and charged in a plurality of times, the depth of the precipitate to be charged at one time becomes shallow, so that the filter press can be efficiently dehydrated. Even if the precipitate is divided into a plurality of times, the secondary dehydration tank and the carry-out container can be filled up by repeating the charging and the filter press.

  Next, the case where the precipitate is divided into small portions and put into the secondary dewatering tank and carry-out container (filter press tank) in a plurality of times has been verified on an experimental scale, and the verification result will be described.

  If the precipitate (solid phase) used in the experiment has a dry weight of 200 g and a water content of about 300%, the volume is 200 / 2.778 + 200 × 300/100 = 672 mL. When the inner diameter of the secondary dewatering tank and carry-out container (filter press tank) used in the experiment is 80 mm, the liquid depth of the precipitate is 672 ÷ (4 × 4 × 3.1415) = 134 mm.

  Assuming that the water content of the precipitate (dehydrated cake) after volume reduction is 100%, the volume is 200 / 2.778 + 200 × 100/100 = 272 mL. The liquid depth (height) of the precipitate (dehydrated cake) after volume reduction is 272 / (4 × 4 × 3.1415) = 54 mm.

  Considering the above, in order to store the 820 mm precipitate (dehydrated cake) in the secondary dewatering tank and carry-out container (drum can), it is necessary to 820 ÷ 54 ≒ 15, that is, it is necessary to divide into 15 layers. It becomes.

  Further, assuming that the time required for dehydration and volume reduction to a water content ratio of 100% is 6 hours from the results of FIG. 10, 6 hours × 15 layers = 90 hours <4 days.

The results of the above review are organized as follows:
(1) The dry weight of the buffer material per disposal hole is about 24 tons, and 164 drum cans are required if it is loaded into a 200 L drum can with a moisture content of 100% (dry weight 147 kg / piece).
(2) If the drum can be dehydrated and reduced in 15 layers to a depth of 820 mm, 4 days are required if the time required for reducing the water content to 100% is 6 hours.
(3) For this reason, it is necessary to leave 164 drums for 4 days or more in the main tunnel near the disposal tunnel, but if it is sequentially transported, it is not necessary to place 164 drums.

  FIG. 14 is a view showing an example of a filter press that divides the precipitate into a plurality of times and puts it into the secondary dewatering tank and carry-out container. In the example shown in FIG. 14, the precipitate D is divided into 15 times and charged into the secondary dehydration tank / carrying container (filter press tank) 82, and the supernatant L is vacuum drained each time.

  Moreover, FIG. 15 is a figure which shows the example of the filter press which divides | segments a deposit and divides into multiple times and throws into a secondary dehydration tank and carry-out container. In the example shown in FIG. 15, the tube connected to the filter portion has a core-sheath structure, and the sediment D is introduced from the tube serving as the core, while the supernatant L is drained from between the tube serving as the core and the tube serving as the sheath. . According to this example, it is possible to efficiently execute a series of processes such as depositing a precipitate, filter press (dehydration), and draining a supernatant liquid (vacuum drainage).

Incidentally, the following load is necessary to apply a press pressure of 12 kPa to the cross-sectional area (diameter 567 mm) of the drum.
(1) When using the weight of a heavy stone 12kPa × (0.28 × 0.28 × 3.1415) m2 = 2.95kN = 2.95 × 1000 ÷ 9.80665≈300kg
(2) When using air pressure 12kPa ≒ 0.12atm
When air pressure is used, it is easy to increase the press pressure by about 5 times.

In summary,
(1) The volume of the suspension can be reduced to less than half in a relatively short time by the primary precipitation process, so the volume of the secondary dehydration tank and carry-out container (filter press processing tank) that becomes the secondary volume reduction tank is small. Can be a thing. Moreover, about half of the salt water sprayed in about 1 hour can be reused.
(2) If the press pressure is 12 kPa or more in the secondary dehydration tank (filter press processing tank), the water content can be reduced to about 80%.
(3) By making the filter into a polymer film having fine pores, clogging of the filter by fine particles in the slurry can be suppressed. Thereby, the efficiency of a filter press process can be improved.
(4) Since the volume reduction process by the filter press method is performed and the secondary dehydration tank is also used as a carry-out container, the volume can be efficiently reduced and carried out of the facility together with the container. Moreover, even if the recovered slurry is contaminated with radioactive substances, it can be carried out in a sealed state without recontaminating the surroundings.
(5) If the press pressure of the filter press processing tank is given by the weight, the energy can be processed under the minimum conditions.
(6) The dry weight of the cushioning material per disposal hole is about 24 tons, and if it is loaded in a 200 L drum can with a water content of 100% (dry weight 147 kg / piece), 164 drum cans are required. If a drum can be divided into 15 layers up to a depth of 820 mm and dehydrated and reduced, it takes 4 days if the time required to reduce the water content to 100% is 6 hours. Although it is necessary to place 164 drums in the main tunnel near the disposal tunnel for more than 4 days, the storage space does not become enormous because the drums can be actually carried out sequentially.
(7) The calculation of the working time this time was based on experimental data at a press pressure of 12 kPa. However, when using air pressure, it is considered easy to increase the press pressure to about 5 times. In that case, the time required for dehydration can be shortened.

DESCRIPTION OF SYMBOLS 1 Recovery apparatus 2 Traveling apparatus 3 Injection nozzle 4 Nozzle head 5 Handling apparatus 6 Discharge pump 61 Salt water storage tank 7 Weir plate apparatus 71 Dam plate 72 Support arm 8 Solid-liquid separation apparatus 81 Primary sedimentation tank 81a Hose 82 Secondary dehydration tank and carrying-out container (Filter press tank)
83 Raised collar 84 Filter part 85 Press part A Main tunnel G Disposal tunnel H Disposal hole P Waste B Buffer material S Suspension D Precipitate L Supernatant

Claims (5)

In the method for recovering a waste body, the buffer material is collapsed by ejecting the electrolyte solution onto the buffer material surrounding the waste body, and the waste body is taken out.
While the suspension containing the collapsed buffer material and the electrolyte solution that disrupts the buffer material is naturally precipitated in the primary sedimentation tank, the supernatant is used as an electrolyte solution that is sprayed onto the buffer material,
A method for recovering a waste material, comprising depositing a natural precipitate in the primary sedimentation tank to a secondary dehydration tank and performing a dehydration treatment with a filter press.   The waste collection method according to claim 1, wherein the filter used in the filter press is a polymer filter having fine pores.   The method for recovering a waste body according to claim 1 or 2, wherein a load used for the filter press is obtained from a loaded stone or compressed air pressure.   The waste body according to any one of claims 1 to 3, wherein after the dehydration process is finished, the filter press device is removed, and then the secondary dewatering tank sealed with a lid is taken out of the facility as it is. Recovery method.   The method for recovering a waste body according to any one of claims 1 to 4, wherein the electrolyte solution recovered by the dehydration treatment is used as an electrolyte solution that is sprayed onto the buffer material.

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