JP2015001485A - Method and apparatus for cement solidification of boric acid-containing waste liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus for cement solidification of boric acid-containing waste liquid, enabling the boric acid-containing waste liquid to be formed into a stable cement solidified body with highly reduced volume.SOLUTION: The method for cement solidification of boric acid-containing waste liquid comprises: a volume reduction step of adding a sodium hydroxide 2 to a radioactive boric acid-containing waste liquid 1 and forming a material to be solidified by volume reduction; the first mixing step of mixing the material to be solidified, mixing water 4 and a hydraulic solidifying material 5 to form a first mixture; and the second mixing step of mixing silica sand 6 and the first mixture to form a second mixture. A weight ratio (weight of silica sand/weight of hydraulic solidifying material) of the silica sand 6 to the hydraulic solidifying material 5 is 1.5-3.0. An apparatus 10 for cement solidification of boric acid-containing waste liquid includes: a mixing machine 11; a boric acid-containing waste liquid supply device 12; a mixing water supply device 13; a hydraulic solidifying material supply device 14; and a silica sand supply device 15.

Description

  The present invention relates to a cement solidification treatment method and a cement solidification treatment apparatus for a boric acid-containing waste liquid.

  In a pressurized water nuclear power plant, a lot of boric acid-containing waste liquid used for adjusting the output of a nuclear reactor is generated. Moreover, in a boiling water nuclear power plant, boric acid water that is urgently injected into a nuclear reactor is stored, and boric acid-containing waste liquid may be generated.

  The boric acid-containing waste liquid is neutralized with sodium hydroxide or lithium hydroxide, and then solidified with cement or asphalt. Among these, in asphalt solidification, the asphalt is heated, the water in the waste liquid is evaporated by the heat, and the sodium borate component is fixed in the asphalt. In this case, however, heating is required to melt the asphalt. In addition, when radiolysis occurs on asphalt, hydrogen gas is generated or the asphalt is deteriorated, and the stability of the solidified body is lowered. In addition, asphalt solidified bodies have low nuclide confinement properties, so there are problems such as restrictions on bringing them into disposal facilities. In recent years, conversion to cement solidification has been promoted.

  Here, in cement solidification, boric acid interferes with the cementation reaction of the cement, resulting in a significant delay in setting and a decrease in strength of the solidified body. For this reason, various proposals have been made such as adding calcium hydroxide or the like as a pretreatment agent and solidifying it from the viewpoint of solidifying the boric acid-containing waste liquid while increasing volume reduction.

  For example, waste liquid containing sodium borate is heated and concentrated at 90 ° C. or higher, cooled to a temperature of 60 ° C. or lower, sodium borate is precipitated, blast furnace cement is added and kneaded, and the kneaded product is put into a drum can. A method of discharging has been proposed (see, for example, Patent Document 1).

  Moreover, the boric acid or borate solution is adjusted to pH 7 to 10, mixed with powders such as divalent or higher metal oxides, hydroxides, salts, cement, slag, etc., and slurried. A method of curing at 30% or less has been proposed (for example, see Patent Document 2).

  However, among the conventional methods for solidifying boric acid-containing waste liquid, sodium borate absorbs water in a method in which a boric acid-containing waste liquid is concentrated to supersaturation and a solidifying material such as cement or slag is added and mixed. This can produce hydrates and cause a condensation event that loses fluidity in a very short time. The same applies to cement solidification using a sodium borate waste liquid as a dry powder. In addition, in the method of concentrating boric acid-containing waste liquid, there is a problem that the concentration of the concentrate increases as the polymerization reaction or condensation reaction of boric acid progresses during the concentration process, resulting in a decrease in concentration efficiency and piping clogging. is there.

  In addition, in order to avoid delay in hardening due to borate and hydrate formation of sodium borate, after adding calcium hydroxide to radioactive boric acid-containing waste liquid to dry powder, compression solidification, solidification with resin, A method of performing cement solidification or the like has been proposed (see, for example, Patent Document 3). This method is useful for processing after stabilizing the borate, but it is possible that insoluble waste liquid components may adhere to the inside of pipes and dryers, and these attached waste liquid components are washed. There are inconveniences such as difficulty.

  Also, as a method of solidifying cement after drying radioactive boric acid containing waste liquid into dry powder, boric acid containing waste liquid is dried without pretreatment such as poor solubilization, and sodium aluminate is solidified as a cement solidification accelerator. A method has been proposed in which lithium hydroxide is added to a solidifying material as an auxiliary material and cemented by adding cement to the material (see, for example, Patent Document 4). In this method, the amount of sodium aluminate and lithium hydroxide added increases to about 35% by weight in the solidified material. And since these solidification promotion materials etc. are expensive, there also exists a subject that cost increases.

  In addition, as a method for solidifying the radioactive boric acid-containing waste liquid, after drying the boric acid-containing waste liquid into a dry powder, it is mixed with an alkali silicate binder aqueous solution, and further from an acidic curing agent, curing retarder, silica sand, etc. There has been proposed a method of mixing and solidifying an auxiliary agent (for example, see Patent Document 5). In this method, the main component of the solidifying material is water glass and does not solidify with cement as the main component.

  As a method for solidifying radioactive waste such as boric acid-containing waste liquid, a method using a solidified material containing a pulverized blast furnace slag, fly ash, silica fume and the like as a main solidified material and a dispersant has been proposed. (For example, see Patent Document 6). In this method, there is a problem that the viscosity of the kneaded product is increased due to the coexistence of the blast furnace slag and the fine powder material, and there is a possibility that hydrogen gas is generated due to radioactive decomposition of the polymer carboxylic acid compound.

JP-A-10-90490 JP-A-11-72593 JP-A-2-208600 JP 2001-97757 A Japanese Patent Publication No. 4-18640 Japanese Patent Laid-Open No. 8-179095

  Thus, the conventional method for solidifying cement with boric acid-containing waste liquid has problems such as a request for further high volume reduction.

  The present invention has been made in order to solve the above-described problems, and provides a cement solidification treatment method and a cement solidification treatment of a boric acid-containing waste liquid that can make the boric acid-containing waste liquid a highly-reduced and stable cement solidified body. An object is to provide an apparatus.

  One aspect of the method for solidifying a boric acid-containing waste liquid according to the present invention is a method for solidifying a radioactive boric acid-containing waste liquid by cement, and adding sodium hydroxide to the boric acid-containing waste liquid to reduce the volume. Volume reduction step to be a solidified material, a first kneading step to knead the material to be solidified, kneaded water and hydraulic solidified material to form a first kneaded material, silica sand and the first And a second kneading step of kneading the kneaded material with the kneaded material to form a second kneaded material, and the weight ratio of the silica sand to the weight of the hydraulic solidified material (silica sand weight / hydraulic solidified material) (Weight) is 1.5 to 3.0.

  One aspect of a cement solidification treatment apparatus for boric acid-containing waste liquid according to the present invention is an apparatus for cement solidifying a radioactive boric acid-containing waste liquid, which is a kneading machine and a solidified material to which volume is reduced by adding sodium hydroxide. A boric acid-containing waste liquid supply device for supplying the kneading machine, a kneaded water supply device for supplying kneaded water to the kneading machine, and a hydraulic solidifying material supplied to the kneading machine to supply the first kneading water. A hydraulic solidification material supply device as a smelted material and a silica sand supply device as a second kneaded material by supplying silica sand to the kneading machine, and the hydraulic solidification in the silica sand supply device The silica sand weight ratio to the material weight (silica sand weight / hydraulic solidified material weight) is 1.5 to 3.0.

  According to the present invention, a boric acid-containing waste liquid can be made into a highly solid and stable cement solidified body.

It is a flowchart which shows the process of the cement solidification processing method of the boric acid containing waste liquid which concerns on one Embodiment of this invention. It is a schematic block diagram of the cement solidification processing apparatus of the boric acid containing waste liquid which concerns on one Embodiment of this invention. It is a graph which shows the relationship between the value of S / C and the intensity | strength of a cement solid body in an Example.

  FIG. 1 is a flowchart showing the steps of a cement solidification treatment method for boric acid-containing waste liquid according to an embodiment of the present invention, and FIG. 2 is a cement solidification treatment apparatus for boric acid-containing waste liquid according to an embodiment of the present invention. It is a schematic block diagram which shows. The embodiment of the present invention will be described below with reference to FIGS.

  The cement solidification treatment method shown in FIG. 1 includes a step of adding sodium hydroxide 2 to the boric acid-containing waste liquid 1 (S101), and drying the boric acid-containing waste liquid 1 to which sodium hydroxide 2 has been added to dry powder 3 A volume reduction step (S102), a first kneading step (S103) in which the dry powder 3, the kneaded water 4 and the hydraulic solidifying material 5 are kneaded to form a first kneaded product, A second kneading step (S104) in which the first kneaded material and the silica sand 6 are kneaded to form a second kneaded material.

  Moreover, the cement solidification processing apparatus 10 shown in FIG. 2 is a kneading machine 11 for kneading the boric acid-containing waste liquid 1 and a boric acid-containing waste liquid supply apparatus 12 for supplying a solidified material reduced in volume to the kneading machine 11. A kneaded water supply device 13 that supplies the kneaded water 4, a hydraulic solidifying material supply device 14 that supplies the hydraulic solidified material 5, and a silica sand supply device 15 that supplies the silica sand 6. The boric acid-containing waste liquid supply device 12 includes a volume reduction device (not shown) for reducing the volume of the boric acid-containing waste liquid 1 to obtain a solidified body, and the volume reduction device is the boric acid-containing waste liquid 1. Is dried by heating to obtain a dry powder 3. The silica sand supply device 15 is provided with a silica sand supply amount adjusting device 16 for adjusting the silica sand supply amount of the silica sand supply device 15 to a predetermined amount. Reference numeral 17 denotes a solidification container in which the second kneaded material kneaded by the kneading machine 11 is housed and solidified.

(First step (S101 shown in FIG. 1))
The object of cement solidification in this embodiment is a radioactive waste liquid containing boric acid (boric acid-containing waste liquid 1). The first step of the present embodiment is a step of adding sodium hydroxide 2 to the boric acid-containing waste liquid 1. As a result, sodium hydroxide 2 reacts with boron in the boric acid-containing waste liquid 1 to produce a sodium borate salt.

  The amount of sodium hydroxide 2 is such that the sodium / boron molar ratio is preferably 0.2 or more, more preferably 0.2 to 0.5, and particularly preferably 0.2 to 0.3. Thereby, the solubility with respect to the water of a sodium borate salt can be improved, and detergency, such as piping and a dryer, can be improved.

(Second step (S102 shown in FIG. 1))
The second step of this embodiment is a step of reducing the volume of the boric acid-containing waste liquid 1 in order to solidify the boric acid-containing waste liquid 1 in a large volume with a high volume reduction. In the second step of the present embodiment, the boric acid-containing waste liquid 1 is supplied to a dryer, where a drying process is performed to obtain a dry powder 3.

  From the viewpoint of reducing deposits on piping and the like, the temperature of the boric acid-containing waste liquid 1 after the addition of sodium hydroxide 2 is equal to or higher than the precipitation temperature of the sodium borate salt, preferably 60 ° C or higher, more preferably 80 ° C to 90 ° C. Supply to the dryer at about ℃ or higher. In the dryer, the boric acid-containing waste liquid 1 is preferably heated to about 80 ° C. or more, more preferably about 120 to 180 ° C., and particularly preferably about 160 ° C. for drying treatment.

  Although it does not specifically limit as a dryer, It is preferable to use a centrifugal thin film dryer. Centrifugal thin film dryers have features such as high thermal efficiency, which can reduce the size of the device, reduce the amount of powder transferred to the gas phase during the drying process, and stabilize the particle size of the resulting sodium borate powder. It is for having.

  In addition, when reducing the volume of the boric acid-containing waste liquid 1, instead of performing the above-described drying process, a concentrated waste liquid may be obtained by performing a concentration process or a sedimentation process. In the concentration treatment, for example, the boric acid-containing waste liquid 1 is heated and concentrated, and the water content in the boric acid-containing waste liquid is set to about 30% or less by weight. In the sedimentation process, sodium borate is precipitated by adding an additive to the boric acid-containing waste liquid 1. The precipitated sodium borate salt is separated into a concentrated waste liquid. In this embodiment, the same effect can be obtained regardless of which processing is performed. The dried powder 3 and the concentrated waste liquid after volume reduction may be cooled to about room temperature, or the next third step may be performed without cooling.

(Third step (S103 shown in FIG. 1))
The 3rd process of this embodiment is a process of kneading dry powder 3, kneading water 4, and hydraulic solidification material 5 using a kneading machine, and making it the 1st kneaded material.

  The sodium borate salt contained in the dry powder 3 has the property of absorbing water and becoming a hydrated salt. Therefore, when the dry powder 3 is kneaded with a mixture of cement and kneaded water as in a normal cement kneading procedure, the viscosity of the cement kneaded material is extremely increased by the hydrated salt, resulting in kneading failure and suspicion. May cause condensation. Therefore, in the third step, the dry powder 3 and the kneaded water 4 are first mixed and stirred, and during this time, a hydrated salt is generated in advance, and the water-curable solidifying material 5 such as cement is kneaded therein. It is preferable. Specifically, it is preferable to knead the dry powder 3 and the kneaded water 4 for, for example, 10 minutes or longer in consideration of the generation time of the hydrated salt.

  Although it does not specifically limit as the hydraulic solidification material 5, It is preferable to use Portland cement. When the boric acid-containing waste liquid 1 is cemented, the calcium in the cement tends to decrease due to the binding of calcium in the cement with boric acid. Therefore, Portland cement having a large amount of calcium in the hydraulic solidifying material 5 can be suitably used. As the hydraulic solidifying material 5, a mixture of Portland cement and blast furnace slag, a mixture of Portland cement and fly ash, or the like may be used.

(Fourth step (S104 shown in FIG. 1))
The fourth step of the present embodiment is a step of kneading the first kneaded product obtained in the third step and the silica sand 6 to form a second kneaded product.

  Boric acid contained in the boric acid-containing waste liquid 1 has a function of significantly delaying the hardening of the cement and a function of reducing the strength of the cement solidified body 8. When calcium hydroxide is added to prevent these, there is a problem that calcium borate salt is deposited in the piping or dryer. In the present embodiment, cement sand 6 is kneaded into the first kneaded material in the fourth step, thereby suppressing the hardening delay of cement without using calcium, and finally the cement solidified body obtained. The strength of 8 can be improved.

  The amount of silica sand 6 kneaded in the fourth step is such that the weight ratio indicated by silica sand 6 / hydraulic solidified material 5 (hereinafter referred to as S / C) is in the range of 1.5 to 3.0. The amount to be. S / C is preferably 1.7 to 2.6, and particularly preferably about 2.3. By making S / C to be 1.5 to 3.0, the strength of the cement solidified body 8 can be improved, and the cement solidified body 8 having good solidification characteristics can be obtained.

  The silica sand 6 preferably has a median diameter of about 0.026 to 1.18 mm.

  Moreover, in this embodiment, when mixing the silica sand 6 in a 4th process, it is preferable to substitute the zeolite 7 for a part of the total weight of the silica sand 6 added. Zeolite 7 is a solid acid and has high radionuclide adsorption performance. Therefore, the addition of zeolite 7 at a predetermined ratio dramatically improves the radioactivity confinement (radionuclide distribution coefficient) of cement solidified body 8. Can be improved. Furthermore, since the zeolite 7 adsorbs boron ions and boron compounds that inhibit the progress of cement solidification, the strength of the cement solidified body 8 can be improved. Boron ions and boron compounds are more likely to be eluted under alkaline conditions, but by adding a predetermined amount of zeolite 7, this adsorbs alkali and increases the pH of the second kneaded product or cement solidified body 8. Suppress. Therefore, elution of boron ions can be suppressed, and the cement solidified body 8 having good solidification characteristics can be obtained.

  The amount of zeolite 7 mixed is such that the weight ratio of zeolite 7 to the total weight of zeolite 7 and silica sand 6 (7 zeolite weight / total weight of zeolite 7 and silica sand 6) is 0.05 to 0.40. Is more preferable, 0.05 to 0.25 is more preferable, and 0.10 to 0.20 is particularly preferable. By mixing the zeolite 7 in this way, the strength and radioactivity confinement of the cement solidified body 8 can be improved. In this case, in the above S / C, the value of S is the total weight of the silica sand 6 and the zeolite 7.

  The particle diameter of zeolite 7 is preferably about 770 μm in terms of median diameter. The ion exchange capacity of zeolite 7 is preferably about 10 to 200 (meq) / 100 (g).

  The method for mixing the silica sand 6 and the zeolite 7 is not particularly limited. The silica sand 6 and the zeolite 7 may be mixed in advance, and this mixture may be mixed with the first kneaded material. 7 may be mixed separately in the first kneaded product. When the silica sand 6 and the zeolite 7 are mixed separately, either the silica sand 6 and the zeolite 7 may be mixed first or at the same time.

  The second kneaded product thus obtained has good viscosity characteristics. Therefore, the second kneaded product can be accommodated in the solidification container 17 such as a drum can from the kneader by the outdrum mixing method to obtain the cement solidified body 8 having good solidification characteristics.

  Moreover, you may perform the cement solidification processing method of this embodiment by the in-drum mixing method. That is, the dry powder 3, the kneaded water 4, the hydraulic solidifying material 5, the silica sand 6 and the zeolite 7 are all kneaded in the radioactive waste solidification container, and the second kneaded product obtained is the radioactive waste. You may solidify as it is in a solidification container. In this case, equipment cost and operation cost can be further reduced.

  As mentioned above, since the 2nd kneaded material has a favorable viscosity characteristic, the cement solidification processing method of this embodiment is excellent in workability | operativity. Furthermore, since calcium is not used, there is no problem of adhesion of waste liquid components to piping or the like. Moreover, according to the cement solidification processing method of this embodiment, the cement solidified body 8 with improved solidification characteristics with improved strength can be obtained by mixing the silica sand 6 at a predetermined ratio.

Example 1
Hereinafter, based on the process shown in FIG. 1, the result of having carried out the cement solidification test of the boric acid-containing waste liquid will be described.
First, sodium hydroxide was added to a 12% by weight aqueous solution of boric acid heated to about 60 ° C., and the Na / B molar ratio was adjusted to 0.25 to obtain an aqueous solution of sodium borate (see FIG. 1). S101). This sodium borate aqueous solution was used as a simulated waste liquid and quantitatively supplied to a centrifugal thin film dryer set at a heating temperature of about 160 ° C. to obtain a sodium borate dry powder (S102 shown in FIG. 1).

  Next, 392 g of kneaded water and then 315 g of the dried sodium borate powder prepared above were charged into a 1 L polycup and stirred for about 60 minutes with a table stirrer to obtain a slurry.

  The obtained slurry was mixed with 375 g of ordinary Portland cement, stirred for about 10 minutes and kneaded to obtain a first kneaded product (S103 shown in FIG. 1). Next, 650 g of silica sand was mixed (S / C = 1.73), and further stirred for about 60 minutes to knead to obtain a second kneaded product (S104 shown in FIG. 1). The physical properties of this second kneaded product were measured, and then poured into a 50 mmφ × 100 mmH mold to obtain a solidified cement.

  The characteristics of the second kneaded product were good flow characteristics with a viscosity of 9 dPa · s and a packing density of 1.99. The cement solidified body had a breathing rate of 0 vol% after 24 hours and a uniaxial compressive strength of 8.9 MPa at a material age of 7 days, and good solidification characteristics were also obtained.

(Example 2)
In the same manner as in Example 1, the mixing amount of each component in Example 1 was 392 g of kneaded water, 375 g of ordinary Portland cement, 315 g of sodium borate dry powder, and 750 g of silica sand (S / C = 2.00). A kneaded product was obtained. Thereafter, a cement solidified body was obtained in the same manner as in Example 1. Further, the physical properties of the second kneaded product and the cement solidified body were evaluated in the same manner as in Example 1.

  The properties of the second kneaded product were good flow properties, with a viscosity of 10 dPa · s and a packing density of 2.02. The cement solidified body had a breathing rate of 0 vol% after 24 hours and a uniaxial compressive strength of 9.6 MPa at a material age of 7 days, and good solidification characteristics were also obtained.

Example 3
In the same manner as in Example 1, the mixing amount of each component in Example 1 was 392 g of kneaded water, 375 g of ordinary Portland cement, 315 g of sodium borate dry powder, and 850 g of silica sand (S / C = 2.27). A kneaded product was obtained. Thereafter, a cement solidified body was obtained in the same manner as in Example 1. Further, the physical properties of the second kneaded product and the cement solidified body were evaluated in the same manner as in Example 1.

  The characteristics of the second kneaded product were good flow characteristics with a viscosity of 12 dPa · s and a packing density of 2.04. The cement solidified body had a breathing rate of 0 vol% after 24 hours, a uniaxial compressive strength of 7 days of age of 12.2 MPa, and good solidification characteristics were also obtained.

Example 4
In the same manner as in Example 1, the mixing amount of each component in Example 1 was 392 g of kneaded water, 375 g of ordinary Portland cement, 315 g of sodium borate dry powder, and 950 g of silica sand (S / C = 2.53). A kneaded product was obtained. Thereafter, a cement solidified body was obtained in the same manner as in Example 1. Further, the physical properties of the second kneaded product and the cement solidified body were evaluated in the same manner as in Example 1.

  The characteristics of the second kneaded product were good flow characteristics with a viscosity of 100 dPa · s and a packing density of 2.07. The cement solidified body had a breathing rate of 0 vol% after 24 hours, a uniaxial compressive strength of 7 days of age of 11.9 MPa, and good solidification characteristics were also obtained.

(Example 5)
In the same manner as in Example 1, the mixing amount of each component in Example 1 was 392 g of kneaded water, 375 g of ordinary Portland cement, 315 g of sodium borate dry powder, and 1125 g of silica sand (S / C = 3.00). A kneaded product was obtained. Thereafter, a cement solidified body was obtained in the same manner as in Example 1. Further, the physical properties of the second kneaded product and the cement solidified body were evaluated in the same manner as in Example 1.

  The properties of the second kneaded product were good flow properties with a viscosity of 100 dPa · s and a packing density of 2.09. The cement solidified body had a breathing rate of 0 vol% after 24 hours and a uniaxial compressive strength of 8.7 MPa at a material age of 7 days, and good solidification characteristics were also obtained.

  In the above Examples 1 to 5, the relationship between the S / C value and the uniaxial compressive strength is shown in the graph of FIG. 3, the S / C value is shown on the horizontal axis, and the uniaxial compressive strength is shown on the vertical axis.

  From FIG. 3, it was found that a good strength was obtained when S / C was 1.5 to 3, and the strength was highest at 2.27. Therefore, in Examples 6 and 7 below, in order to further improve the radioactive confinement property of the cement solidified body with this S / C = 2.27, a part of silica sand is replaced with zeolite, and the cement solidified body at this time The physical properties of were evaluated.

(Example 6)
The mixing amount of each component in Example 4 was 390 g of kneaded water, 375 g of ordinary Portland cement, 312 g of sodium borate dry powder, 680 g of silica sand, 170 g of zeolite (S / C = 2.27, zeolite weight / silica sand weight = 20/80), a second kneaded product was obtained in the same manner as in Example 1. Thereafter, a cement solidified body was obtained in the same manner as in Example 1. Further, the physical properties of the second kneaded product and the cement solidified body were evaluated in the same manner as in Example 1.

  The characteristics of the second kneaded product were good flow characteristics with a viscosity of 70 dPa · s and a packing density of 2.0. The cement solidified body has a breathing rate of 0 vol% after 24 hours, has a uniaxial compressive strength of 9.6 MPa at a material age of 7 days and a uniaxial compressive strength of a material at 28 days of age of 12 MPa, and also has good solidification characteristics. It was.

(Example 7)
The mixing amount of silica sand and zeolite in Example 6 was set to 765 g of silica sand and 85 g of zeolite (S / C = 2.27, zeolite weight / silica sand weight = 10/90). A wrought product was produced, and its physical properties were evaluated as a cement solidified body as in Example 1.

  The cement solidified body had a uniaxial compressive strength of 8.9 MPa at an age of 28 days, and good solidification characteristics could be obtained.

(Comparative Example 1)
In Example 1, a kneaded material was manufactured without mixing silica sand. That is, a kneaded product was obtained in the same manner as in Example 1 as 392 g of kneaded water, 750 g of ordinary Portland cement, and 315 g of sodium borate dry powder. After measuring the physical properties of the kneaded material, the physical properties were evaluated as a cement solidified body as in Example 1.

  The kneaded product had a viscosity of 150 dPa · s and a packing density of 1.95. The cement solidified body had a breathing rate of 0 vol% after 24 hours, but the uniaxial compressive strength of the material 7 days old was about 2.9 MPa, and it was found that the strength was insufficient.

Table 1 shows the conditions and measurement results of Examples 1 to 7 and Comparative Example 1 described above.

  As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 101 ... 1st process, 102 ... 2nd process, 103 ... 3rd process, 104 ... 4th process, 1 ... Boric acid containing waste liquid, 2 ... Sodium hydroxide, 3 ... Dry powder, 4 ... Kneading water, 5 DESCRIPTION OF SYMBOLS ... Hydraulic solidification material, 6 ... Silica sand, 7 ... Zeolite, 8 ... Cement solidification body, 10 ... Cement solidification processing device, 11 ... Kneading machine, 12 ... Boric acid containing waste liquid supply device, 13 ... Kneading water supply device , 14 ... Hydraulic solidifying material supply device, 15 ... Silica sand supply device, 16 ... Silica sand supply amount adjusting device, 17 ... Solidification container.

Claims (10)

A method for solidifying a radioactive boric acid-containing waste liquid into cement,
A volume reduction step of adding sodium hydroxide to the boric acid-containing waste liquid to reduce the volume to be solidified;
A first kneading step of kneading the solidified material, kneaded water, and hydraulic solidified material into a first kneaded product;
A second kneading step of kneading silica sand and the first kneaded product to form a second kneaded product,
The cement solidification method of boric acid-containing waste liquid, wherein the weight ratio of the silica sand to the weight of the hydraulic solidification material (silica sand weight / hydraulic solidification material weight) is 1.5 to 3.0. Further mixing zeolite in the second kneading step,
The ratio of the total weight of the zeolite and the silica sand to the weight of the hydraulic solidification material (total weight of zeolite and silica sand / weight of the hydraulic solidification material) is 1.5 to 3.0. The cement solidification processing method of boric acid containing waste liquid of 1 description.   3. The method for solidifying a boric acid-containing waste liquid according to claim 1, wherein the silica sand has a median diameter of 0.026 to 1.12 mm.   4. The method of solidifying a boric acid-containing waste liquid according to claim 2, wherein the zeolite has a median diameter of 770 [mu] m and the zeolite has an ion exchange capacity of 10 to 200 meq / 100 g.   The zeolite weight ratio (zeolite weight / total weight of silica sand and zeolite) with respect to the total weight of the silica sand and the zeolite is 0.05 to 0.40. A method for solidifying cement in a boric acid-containing waste liquid as described in the item.   The method of mixing the silica sand and the zeolite and the first kneaded product in the second kneading step is to mix the silica sand and the zeolite previously mixed in the first kneaded product, or 6. The method for solidifying a boric acid-containing waste liquid according to claim 2, wherein the silica sand and the zeolite are separately mixed in one kneaded product.   The cement solidification treatment method for boric acid-containing waste liquid according to any one of claims 1 to 6, wherein the method is performed by an in-drum mixing method or an out-drum mixing method.   The solidified material is a dry powder obtained by drying the boric acid-containing waste liquid, or a concentrated waste liquid obtained by concentrating the boric acid-containing waste liquid or by precipitating the sodium borate salt. The cement solidification processing method of the boric-acid containing waste liquid of any one of these.   The method for solidifying cement in a boric acid-containing waste liquid according to any one of claims 1 to 8, wherein the temperature of the solidified material in the volume reduction step is normal temperature to 100 ° C. An apparatus for cementing radioactive boric acid-containing waste liquid,
Kneading machine,
A boric acid-containing waste liquid supply device for adding sodium hydroxide and supplying the reduced solidified material to the kneader;
A kneading water supply device for supplying kneading water to the kneading machine;
A hydraulic solidification material supply device that supplies hydraulic solidification material to the kneading machine to form a first kneaded product;
A silica sand supply device for supplying silica sand to the kneading machine as a second kneaded product,
The boric acid-containing waste liquid cement, wherein the weight ratio of the silica sand to the weight of the hydraulic solidification material (silica sand weight / hydraulic solidification material weight) in the silica sand supply device is 1.5 to 3.0. Solidification processing equipment.

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