JP4823180B2 - Radioactive waste granulator - Google Patents

Description

The present invention is a powder obtained from the sodium nitrate liquid waste produced in the radioactive liquid waste and nuclear fuel reprocessing generated from nuclear facilities regarding Concrete TsubuSo location of radioactive waste to pellet.

  For the treatment of radioactive liquid waste generated from nuclear facilities, the concentration of the waste liquid is increased by concentration and then mixed with cement or asphalt to solidify and stabilized, or the concentrated waste liquid is dried directly or with a dryer. A method of stabilizing and storing cement, plastic, etc. after solidifying and pulverizing by processing is used.

  In the nuclear fuel reprocessing facility, there is a process of dissolving spent nuclear fuel in nitric acid, and a large amount of recovered nitric acid waste liquid is generated. The nitric acid waste liquid is neutralized with sodium hydroxide, and the generated sodium nitrate waste liquid is stored in a tank. The sodium nitrate waste liquid stored in the tank is concentrated, dried and pulverized, and then pelletized by a granulator.

  As a method for pelletizing radioactive waste, the following Patent Document 1 discloses a method in which a concentrated waste liquid is dried with a centrifugal thin film dryer and then mixed with about 5% of fibrous activated carbon and pelletized with a tablet granulator. Is disclosed. Patent Document 2 below discloses a method for solidifying pellet waste containing powder generated from a nuclear facility.

  In general, powder granulation methods include rolling granulation, briquetting, tablet granulation, mixed stirring granulation, extrusion granulation, jetting granulation, fluidized bed granulation, emulsified flow, in liquid There are granulation, spray granulation, vacuum freezing granulation and the like. In many of these granulation methods, binders (binders) are used, but there are many types of binders, and they are appropriately selected depending on the type of powder, particle size, moisture content, and granulation method. There is a need. The selection of granulation method and binder is an important factor in granulation. Commonly used binder types and granulation mechanisms are shown below.

(1) Inorganic substances There are cement, gypsum, water glass (sodium silicate), minerals (clay, bestnite), etc. The granulation reaction by these binders is mainly hydration reaction between the binder and water.

(2) Organic matter (a) Natural product There are starch, protein, natural rubber, tar, asphalt, etc. The granulation reaction by these binders is by dehydration, cooling solidification, solvent evaporation and the like.
(B) Synthetic materials There are thermoplastic resins, thermosetting resins, elastomers, etc., and the granulation reaction by these binders is due to condensation reaction, emulsion copolymerization, or coagulation.

Sodium nitrate waste liquid generated by nuclear fuel reprocessing is dried and powdered by a vertical centrifugal thin film dryer, and then pelletized by a granulation method using a tableting system using a silica-based sol (colloid solution) as a binder. Cement is solidified.
JP-A-6-273589 JP 2000-187099 A

  The silica gel binder used for powder granulation of the sodium nitrate waste liquid generated in the nuclear fuel reprocessing facility is sprayed onto the powder from the nozzle in the mixing tank. The amount of binder sprayed is about 2% with respect to the powder. The nozzle sprayed with this silica-based gel binder, after the spraying is finished, flows air at a high flow rate to the inside and outside of the nozzle, adheres to the tip of the nozzle, or prevents and removes the binder hanging from the pipe. ing. However, when the binder cannot be completely removed, the binder is cured while adhering to the tip and side surfaces of the nozzle, and the nozzle is blocked and a new binder cannot be supplied.

  In addition, pipe joints, valves, and the like are installed in pipes that supply the gel-like binder to the mixing tank, but the gel-like binder stays in the steps of these instruments. The staying gel binder solidifies over time, and may cause a decrease in flow rate, valve passage blockage, and malfunction.

  Conventionally, a fluororesin is used as the nozzle, and the gel binder is sprayed onto the radioactive waste powder from the fluororesin nozzle by air. After spraying the gel binder, air is sprayed onto the outer cylinder of the fluororesin nozzle to prevent the gel binder from remaining. By this outer cylinder air injection, the fluororesin nozzle outlet may be worn by the dust contained in the injection air at the nozzle outlet, the nozzle may be damaged, and the gel binder may not be sprayed sufficiently.

The present invention has been made to solve the above problems, a concrete TsubuSo location of radioactive waste which can be sprayed stably for a long period of time the binder for granulating a powder of radioactive waste The purpose is to provide.

In order to achieve the above object, the radioactive waste granulation apparatus of the present invention comprises a mixing tank into which powdered radioactive waste is fed, a liquid binder attached to the mixing tank and attached to the powdered radioactive waste. A spraying nozzle, a granulator for granulating radioactive waste mixed with a binder in the mixing tank, and a vibration means for intermittently impacting the nozzle, the nozzle being made of metal And an innermost pipe made of a fluororesin provided inside the inner pipe, and a compressed air flow path is formed between the outer pipe and the inner pipe, and the innermost pipe It is set as the structure by which the binder flow path is formed inside .

According to the present invention, it is possible to provide a granulated TsubuSo location of radioactive waste which can be sprayed stably for a long period of time the binder for granulating a powder of radioactive waste.

Hereinafter, three embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 is a configuration diagram of a radioactive waste granulation apparatus according to a first embodiment of the present invention, wherein 1 is a liquid binder tank, 2 is a feed metering pump, 3 is compressed air, and 4 is a spray of binder. Nozzle, 5 is an air hammer, 6 is a powder hopper, 7 is a screw feeder, 8 is a mixing tank, 9 is a mixing stirrer, 10 is a screw feeder, and 11 is a granulator.

  A method for pelletizing the concentrated waste liquid dry powder generated from the nuclear fuel reprocessing step with a silica-based sol-like binder will be described with reference to FIG.

(Comparative example)
The liquid binder tank 1 is filled with a silica gel binder as a binder. The concentrated waste liquid is dried and pulverized to fill the powder hopper 6 with the concentrated waste liquid powder (main component: sodium nitrate). The concentrated waste liquid powder is transferred from the powder hopper 6 to the mixing tank 8 through the screw feeder 7. The mixing stirrer 9 is operated and stirring of the powder in the mixing tank 8 is started. The feed liquid metering pump 2 is driven, the binder of the liquid binder tank 1 is supplied to the mixing tank 8, the mixing agitator 9 is operated, the compressed air 3 is supplied to the binder spray nozzle 4, and the liquid binder is concentrated. Spray to waste liquid powder and mix with concentrated waste liquid dry powder. The concentrated waste liquid powder mixed with the binder is supplied to the granulator 11 by the screw feeder 10 to granulate the concentrated waste liquid powder by a tableting method.

  The above operation was performed 18 times a day for 5 consecutive days, and the operation was repeated 90 times in total. When the operation was performed again after a predetermined period (2 days), the silica-based gel binder from the binder spray nozzle 4 could not be sprayed. As a result of opening the mixing tank 8 for inspection, the silica gel-like substance adhered and hardened on the entire outlet of the binder spray nozzle 4, and the outlet was blocked. The binder adhered and hardened at the nozzle outlet was peeled off with a chisel.

Example 1
The liquid binder tank 1 is filled with a silica gel binder as a binder. The concentrated waste liquid is dried and pulverized to fill the powder hopper 6 with the concentrated waste liquid powder (main component: sodium nitrate). The concentrated waste liquid powder is transferred from the powder hopper 6 to the mixing tank 8 through the screw feeder 7. The mixing stirrer 9 is operated and stirring of the powder in the mixing tank 8 is started. The feed liquid metering pump 2 is driven, the binder in the liquid binder tank 1 is supplied from the binder spray nozzle 4 to the mixing tank 8, the mixing agitator 9 is operated, and the compressed air 3 is supplied to the binder spray nozzle 4. Then, the liquid binder is sprayed onto the concentrated waste liquid powder and mixed with the concentrated waste liquid dry powder. At this time, an air hammer 5 (Seishin company, trade name Eleknocker, model SEK-3, impact force 10.8 N · m / S) is attached to the upper part of the nozzle 4, and the nozzle 4 is intermittently once every 5 seconds. The impact was applied to the binder spray nozzle 4 by hitting. Then, the concentrated waste liquid powder mixed with the binder by the screw feeder 10 was supplied to the granulator 11, and the concentrated waste liquid powder was granulated by a tableting method.

  This operation was performed 10 times a day for 5 consecutive days, and the operation was repeated 50 times in total. As a result of opening and checking the mixing tank 8 after a predetermined period (2 days), there was no liquid silica gel binder and no hardened binder at the outlet of the binder spray nozzle 4.

(Example 2)
The position of the air hammer 5 was changed from the upper part of the nozzle 4 to the central part and attached, and the same operation as in Example 1 was performed 10 times a day for 5 consecutive days, and the operation was repeated 50 times in total. As a result of inspection after opening the mixing tank after a predetermined period (2 days), a liquid silica gel-like binder and a hardened binder are present at the outlet of the binder spray nozzle 4 as in Example 1. There was no existence.

(Example 3)
The position of the air hammer 5 was changed from the upper part to the lower part of the nozzle 4 and attached, and the same operation as in Example 1 was performed 10 times a day for 5 consecutive days, and the operation was repeated 50 times in total. As a result of inspection after opening the mixing tank 8 after a lapse of a predetermined period (2 days), a liquid silica-based gel binder and a hardened bond are present at the outlet of the binder spray nozzle 4 as in Example 1. There was no agent present.

Example 4
The air hammer 5 is returned to the upper part of the nozzle 4 at the same position as in Example 1, and the nozzle is intermittently hit in a case once every 10 seconds and once every 3 seconds when the air hammer 5 is hit. An impact force was applied to the spray nozzle. The same operation as in Example 1 was performed 10 times a day for 5 consecutive days, and the operation was repeated 50 times in total. As a result of opening the mixing tank 8 after a predetermined period (2 days) and inspecting it, liquid silica gel-like binder and hardened at the outlet of the binder spray nozzle 4 as in (Example 1). There was no binder present.

(Example 5)
The air hammer 5 was attached to the upper part, the central part, and the lower part of the nozzle 4, and the same operation as in Example 1 was continuously performed 10 times a day for 5 days, and the operation was repeated 50 times in total. As a result of inspection after opening the mixing tank after a predetermined period (2 days), a liquid silica gel-like binder and a hardened bond are formed at the outlet of the binder spray nozzle 4 as in Example 1. There was no agent present.

(effect)
Comparing the above (Comparative Example) and (Example 1) to (Example 5), it is caused by the residual adhesion and curing phenomenon of the liquid binder due to the blow of the air hammer 5 in the first embodiment of the present invention. The effect of preventing clogging of nozzles and pipes is as follows.

  In the method of (Comparative Example), the liquid binder accumulates on the tip and side surfaces of the nozzle 4 due to the dripping of the liquid binder remaining in the pipe and the like after spraying the liquid binder. These liquid binders cannot be sufficiently removed by air purge, and gradually lose moisture as time elapses, and gradually dry, accumulate at the tip of the nozzle 4 and so on, and eventually harden and deposit a cured product. And the nozzle 4 will be obstruct | occluded by hardening of a liquid binder.

  According to (Embodiment 1) to (Embodiment 5), the nozzle 4 is intermittently hit with the air hammer 5 to provide the following effects. First, the binder adhering to and remaining on the nozzle or the like is dropped by striking the air hammer 5. Secondly, even if the adhering and remaining binder is hardened at an early stage, the hardened material is peeled off from the nozzle 4 by the impact of the air hammer 5 and the hardened material falls. Further, it can be seen from (Example 5) that one air hammer 5 is sufficient. The nozzle 4 may be blown by the air hammer 5 at an appropriate time interval during the spraying of the liquid binder or during the rest period.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG.
FIG. 2 is a view showing a flange joint portion of the pipe 13 (see FIG. 1) for transferring the liquid binder. That is, fluororesin ring-shaped packings 15 are provided on both end faces of the fluororesin pipes 13a and 13b, and the fluororesin ring-shaped packings 15 are welded and integrated with the fluororesin pipes 13a and 13b. It is a thing. When the both end faces of the pipes 13a and 13b are joined by the flanges 14a and 14b, the joints are not uneven. For this reason, the gel-like binder does not remain in the flange joint portion after the end of the final process and is not cured.

(Example)
A ring-shaped packing 15 made of fluororesin is attached to the flange joints of the pipes 13a and 13b, which are a part of the pipe 13, so that there are no steps or gaps. Filled with gel-based binder. The concentrated waste liquid is dried and pulverized to fill the powder hopper 6 with the concentrated waste liquid powder (main component: sodium nitrate). The concentrated waste liquid powder is transferred from the powder hopper 6 to the mixing tank 8 by the screw feeder 7. The mixing stirrer 9 is operated and stirring of the powder in the mixing tank 8 is started. The feed liquid metering pump 2 is driven, the binder in the liquid binder tank 1 is supplied from the binder spray nozzle 4 to the mixing tank 8, and the compressed air 3 is supplied to the binder spray nozzle 4 while operating the mixing agitator 9. The liquid binder was sprayed onto the concentrated waste liquid powder and mixed with the concentrated waste liquid dry powder.

  The operation was repeated 10 times a day for 5 consecutive days, and the operation was repeated 50 times in total. After a predetermined period (2 days) elapsed, the pipe joint part was opened, and the residual state of the liquid binder at the joint part was visually observed. Since the pipe joint portion was smoothed by applying the ring-shaped packing 15, it was confirmed that the liquid binder did not adhere and remain.

(Comparative example)
A similar test was carried out using a ring-shaped packing made of an inorganic material commonly used for a pipe joint at the flange joint of the pipe 13. The liquid binder tank 1 of FIG. 1 is filled with a silica-based sol binder as a binder. The concentrated waste liquid is dried and pulverized to fill the powder hopper 6 with the concentrated waste liquid powder (main component: sodium nitrate). The concentrated waste liquid powder is transferred from the powder hopper 6 to the mixing tank 8 by the screw feeder 7. The mixing stirrer 9 is operated and stirring of the powder in the mixing tank 8 is started. The feed liquid metering pump 2 is driven, the binder in the liquid binder tank 1 is supplied from the binder spray nozzle 4 to the mixing tank 8, and the compressed air 3 is supplied to the binder spray nozzle 4 while operating the mixing agitator 9. The liquid binder was sprayed onto the concentrated waste liquid powder and mixed with the concentrated waste liquid dry powder.

  The operation was repeated 10 times a day for 5 consecutive days, and the operation was repeated 50 times in total. After a predetermined period (2 days) elapsed, the pipe joint part was opened, and the residual state of the liquid binder at the joint part was visually observed. The liquid binder remaining on the stepped portion of the pipe joint packing exhibited a dripping state and was dried and cured.

(effect)
According to the present embodiment, by using the ring-shaped packing 15 made of fluororesin, the stepless structure inside the transfer pipe 13, and the flange integrated line, the step of the pipe joint can be eliminated, and the liquid binder remains. The pipe is not blocked by the liquid binder curing at the pipe joint.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIG.
FIG. 3 is a longitudinal sectional view of the nozzle 4 (see FIG. 1) for spraying the liquid binder. The nozzle in the present embodiment includes a metal (stainless steel) outer tube 17 and an inner tube 18, and an innermost tube 19 made of a fluororesin that is provided in close contact with the inner side of the inner tube 18. A compressed air flow path 20 is formed between the inner pipe 18 and the inner pipe 18, and the inner side of the innermost pipe 19 is a liquid binder flow path.

(Example)
In this example, the nozzle shown in FIG. 3 was used. The liquid binder tank 1 of FIG. 1 is filled with a silica-based sol binder as a binder. The concentrated waste liquid is dried and pulverized to fill the powder hopper 6 with the concentrated waste liquid powder (main component: sodium nitrate). The concentrated waste liquid powder is transferred from the powder hopper 6 to the mixing tank 8 by the screw feeder 7. The mixing stirrer 9 is operated and stirring of the powder in the mixing tank 8 is started. While the feed liquid metering pump 2 is driven and the binder in the liquid binder tank 1 is supplied from the binder spray nozzle 4 to the mixing tank 8, the mixing agitator 9 is operated and the compressed air 3 is supplied to the binder spray nozzle 4. The liquid binder was sprayed onto the concentrated waste liquid powder and mixed with the concentrated waste liquid dry powder.

  The operation was repeated 10 times a day for 5 consecutive days, and the operation was repeated 50 times in total. After a predetermined period (2 days), the nozzle 4 was removed from the test apparatus, the weight of the nozzle 4 was measured, and the abrasion of the innermost tube 19 made of a fluororesin was examined by weight measurement and a micrograph. There was no weight reduction, and no abrasion of the nozzle 4 was observed even by observation with a photomicrograph.

(Comparative example)
In FIG. 3, a nozzle having no inner tube 18 was used. A silica-based gel binder is filled in the liquid binder tank 1 of FIG. The concentrated waste liquid is dried and pulverized to fill the powder hopper 6 with the concentrated waste liquid powder (main component: sodium nitrate). The concentrated waste liquid powder is transferred from the powder hopper 6 to the mixing tank 8 by the screw feeder 7. The mixing stirrer 9 is operated and stirring of the powder in the mixing tank 8 is started. The feed liquid metering pump 2 is driven, the binder in the liquid binder tank 1 is supplied from the binder spray nozzle 4 to the mixing tank 8, and the compressed air 3 is supplied to the binder spray nozzle 4 while operating the mixing agitator 9. The liquid binder was sprayed onto the concentrated waste liquid powder and mixed with the concentrated waste liquid dry powder.

The operation was repeated 10 times a day for 5 consecutive days, and the operation was repeated 50 times in total. After a predetermined period (2 days), the nozzle 4 was removed from the test apparatus, the weight of the nozzle 4 was measured, and the abrasion of the innermost tube 19 made of fluororesin was examined by weight measurement and microscopic observation.
The weight of the innermost tube 19 made of fluororesin was reduced by 2% from the weight at the start of the test, and as a result of observing the surface with a micrograph, many streak-like scratches due to wear were observed.

(effect)
In the present embodiment, the binder spray nozzle 4 is configured such that the innermost pipe 19 made of fluororesin is attached to the inner side of the metal inner pipe 18, so that the nozzle by the compressed air at the time of spraying the liquid binder is used. Abrasion can be prevented.

The block diagram which shows the structure of the granulation apparatus of the radioactive waste of the 1st Embodiment of this invention. Sectional drawing which shows the structure of the flange joint part of piping of the 2nd Embodiment of this invention. Sectional drawing which shows the structure of the binder spraying nozzle of the 3rd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Liquid binder tank, 2 ... Liquid supply metering pump, 3 ... Compressed air, 4 ... Binder spray nozzle, 5 ... Air hammer, 6 ... Powder hopper, 7 ... Screw feeder, 8 ... Mixing tank, 9 ... Mixing Stirrer, 10 ... screw feeder, 11 ... granulator, 13, 13a, 13b ... piping, 14a, 14b ... flange, 15 ... ring packing, 17 ... outer tube, 18 ... inner tube, 19 ... innermost tube, 20 ... compressed air flow path, 21 ... liquid binder flow path.

Claims (3)

A mixing tank into which powdered radioactive waste is fed, a nozzle attached to the mixing tank for spraying a liquid binder onto the powdered radioactive waste, and a radioactive waste mixed with the binder in the mixing tank A granulator and a vibration means for giving an intermittent impact to the nozzle ,
The nozzle includes a metal outer tube and an inner tube, and an innermost tube made of a fluororesin provided inside the inner tube, and a compressed air flow path is formed between the outer tube and the inner tube. A radioactive waste granulation apparatus , wherein a binder flow path is formed inside the innermost tube . A mixing tank into which powdered radioactive waste is fed, a nozzle attached to the mixing tank for spraying a liquid binder onto the powdered radioactive waste, and a radioactive waste mixed with the binder in the mixing tank A granulator and a vibration means for giving an intermittent impact to the nozzle,
Granulating device wherein the connecting portion of the pipe for supplying binding agent to the nozzle, you characterized in that it comprises a packing made of fluororesin radioactive waste. A mixing tank into which powdered radioactive waste is fed, a nozzle attached to the mixing tank for spraying a liquid binder onto the powdered radioactive waste, and a radioactive waste mixed with the binder in the mixing tank A granulator and a vibration means for giving an intermittent impact to the nozzle,
The nozzle includes a metal outer tube and an inner tube, and an innermost tube made of a fluororesin provided inside the inner tube, and a compressed air flow path is formed between the outer tube and the inner tube. A binder flow path is formed inside the innermost tube,
A radioactive waste granulating apparatus, wherein a connecting portion of a pipe for supplying a binder to the nozzle is provided with a packing made of fluororesin.

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