JP5322335B1 - Purification method for radioactively contaminated water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To separate and collect radioactively contaminated water into highly radioactive contaminants and purified water, recycle the collected purified water into decontamination water, and solidify and reduce the volume of highly radioactive contaminants. A water purification treatment method is provided.
By using a reaction vessel equipped with a stirrer, a heating device, and an air blowing device, radioactively contaminated water is collected in the reaction vessel, and iron salt crystals are added and dissolved while stirring to obtain radioactivity. Cesium-containing magnetic iron oxide precipitation by adding iron ions to radioactively contaminated water mixed with iron ions in contaminated water, adding alkali to the radioactively contaminated water treated with iron ions, mixing with heating and oxidizing This is a treatment method for purifying radioactively contaminated water, which consists of a cesium coprecipitation reaction treatment and a solid-liquid separation treatment that separates and recovers the cesium coprecipitation reaction treatment solution into purified water and cesium-containing magnetic iron oxide precipitates. is there.
[Selection] Figure 1

Description

  The present invention relates to a purification method for radioactively contaminated water that separates radioactively contaminated water into highly radioactive contaminants and purified water.

  The nuclear accident at TEPCO's Fukushima Daiichi NPS on March 11, 2011 contaminated a vast area with radioactivity. Decontamination treatment has become an urgent issue for the reconstruction of the affected areas. A general public call for decontamination technology was conducted by a public institution, and a demonstration test project for the adopted technology was conducted (for example, see Non-Patent Document 1).

  Non-Patent Document 1 describes 22 decontamination techniques that were publicly recruited and adopted by the Ministry of the Environment. According to this document, the present invention relates to decontamination technology that targets road surfaces, soil, bottom soil of ponds, organic matter, burgers, incineration ash and rubble. Although the decontamination techniques are various as many as the objects to be decontaminated, in many cases, a water washing process is included, and decontamination processing of radioactively contaminated water generated after decontamination is necessary.

  Since cesium is a substance with high water solubility, it is easy to think that cesium in radioactively contaminated water is dissolved in water and exists as cesium ions, so zeolites known as substances that adsorb cesium ions and A decontamination technique and material development (Non-patent Document 2) that adsorbs and removes cesium of radioactive polluted water by using ferrocyanide (Prussian blue) is also progressing.

  On the other hand, Non-Patent Document 3 is a report on decontamination verification work. The report describes the results of the decontamination technology verification test in detail for each decontamination object in terms of background, implementation details, test results and evaluation. “Background” in the chapter “(5) Water” on page 24 of the report includes the “deletion of school pool decontamination handbook compiled by JAEA (JAEA, 2011). When cesium in water is agglomerated and treated with water, the measurement data of water in which radioactivity is detected correlates with the concentration of SS (Suspended Solid) component, which is fine particles like clay. The substance is thought to be abundant in SS components in water. "

  The above background information shows the actual state of cesium contamination. However, according to daily information such as newspapers, many of the decontamination technologies that have been implemented are radioactive contamination generated by decontamination treatment. In the case of technology that uses decontamination treatment using water as it is stored in temporary storage, it is more difficult to secure temporary storage because contaminated wastewater is collected in containers and stored in temporary storage. The situation has been reported.

  In order to solve this situation, we thought that it was necessary to separate and collect radioactive polluted wastewater generated by decontamination treatment into radioactive pollutants and purified water. However, there is no description about such decontamination technology.

“2011 Decontamination Technology Demonstration Project”, [online], issued in August 2012, Ministry of the Environment, [Search June 7, 2013], Internet (URL: http: //www.env.go. jp / jishin / rmp / attach / tech_gaiyo-201208.pdf) “Cesium adsorption ability is improved by Prussian blue with nano particles”, [online], announced on February 8, 2012, Independent Administrative Agency, National Institute of Advanced Industrial Science and Technology, [Search June 7, 2013], Internet ( URL: http://www.aist.go.jp/aist_j/press_release/pr2012/pr20120208/pr20120208.html) Report on Decontamination Demonstration Work in Evacuation Zones Related to Fukushima Daiichi Nuclear Power Station Accident, [online], Issued June 2012, Independent Administrative Agency, Japan Atomic Energy Agency, [Search June 7, 2013] ], Internet (URL: http://www.jaea.go.jp/fukushima/kankyoanzen/d-model_report/report_3.pdf#search='%E7%A6%8F%E5%B3%B6%E7%AC% AC% E4% B8% 80% E5% 8E% 9F% E5% AD% 90% E5% 8A% 9B% E7% 99% BA% E9% 9B% BB% E6% 89% 80% E4% BA% 8B% E6% 95% 85% E3% 81% AB% E4% BF% 82% E3% 82% 8B% E9% 81% BF% E9% 9B% A3% E5% 8C% BA% E5% 9F% 9F% E7% AD% 89% E3% 81% AB% E3% 81% 8A% E3% 81% 91% E3% 82% 8B% E9% 99% A4% E6% 9F% 93% E5% AE% 9F% E8% A8% BC% E6% A5% AD% E5% 8B% 99% E5% A0% B1% E5% 91% 8A% E6% 9B% B8% E3% 80% 82% E5% B9% B3% E6% 88% 90% EF% BC% 92% EF% BC% 94% E5% B9% B4% EF% BC% 96% E6% 9C% 88% E3% 80% 82% E7% 8B% AC% E7% AB% 8B% E8% A1% 8C% E6% 94% BF% E6% B3% 95% E4% BA% BA% E3% 83% BB% E6% 97% A5% E6% 9C% AC% E5% 8E% 9F% E5% AD% 90% E5% 8A% 9B% E7% A0% 94% E7% A9% B6% E9% 96% 8B% E7% 99% BA% E6% A9% 9F% E6% A7% 8B ')

  Therefore, the present invention separates and collects radioactive polluted water into highly radioactive pollutants and purified water, recycles the collected purified water into decontamination water, etc., and reduces the volume of highly radioactive pollutants. It is an object to provide a method for purifying contaminated water.

  The method for purifying radioactively contaminated water of the present invention includes an iron ion addition treatment in which iron ions are added to and mixed with the radioactively contaminated water, and an alkali is added to the radioactively contaminated water subjected to the iron ion addition treatment, followed by heat oxidation. A cesium coprecipitation reaction treatment for producing a cesium-containing iron oxide precipitate, and a solid-liquid separation treatment for separating the aqueous solution produced by the cesium coprecipitation reaction treatment into purified water and a cesium-containing iron oxide precipitate. It is characterized by having.

  In this case, in the iron ion addition treatment, it is preferable that the iron salt to be added is ferrous sulfate and the addition treatment amount is 0.001 to 1.000 mol / l (liter) in terms of iron ion concentration.

  In the cesium coprecipitation treatment, the alkali to be added is at least one of sodium hydroxide, calcium hydroxide, and magnesium hydroxide, and the addition amount is 0.9 equivalent or more with respect to the iron ion amount, and 1. It is preferable that the amount is less than 0 equivalent.

  In the cesium coprecipitation reaction treatment, the heating oxidation is preferably performed at a heating temperature of 50 ° C to 80 ° C.

  In the solid-liquid separation process, it is preferable to use a magnetic separation device for solid-liquid separation.

  In addition, the method for purifying radioactively contaminated water of the present invention preferably has a solidification treatment in which the separated and recovered cesium-containing iron oxide precipitate is formed and solidified with a solidifying agent. In this case, calcined gypsum and / or cement can be used as a solidifying agent in the solidification treatment.

  In addition, it is preferable that the method for purifying radioactively contaminated water of the present invention further includes a water regeneration process in which the separated purified water is regenerated as decontamination water or discharged as waste water.

  According to the method for purifying radioactively contaminated water of the present invention, the radioactively contaminated water generated by the decontamination process can be separated and recovered into purified water and highly radioactive contaminants.

  Moreover, if the separated and purified water is regenerated into decontamination water or the like, the amount of radioactively contaminated water is reduced, and the temporary storage problem can be solved and the decontamination process can be promoted. On the other hand, if the highly radioactive contaminants separated and recovered are solidified and reduced in volume, they will bring about effects such as contributing to effective utilization of the final treatment plant.

  In addition, the materials used for the cesium coprecipitation reaction treatment are inexpensive iron salts and alkalis, and are used in a very small amount, and the solidifying agents used for solidifying radioactive contaminants are inexpensive gypsum and cement materials. In addition, there is a great cost merit in, for example, regenerating the separated and purified water into decontamination water.

It is a figure which shows the flow of a series of processing processes by this invention. It is a figure which shows the structure of the Example of this invention. It is a figure which shows the process sequence of an experiment example.

  The outline of the present invention will be described below. The present inventor considers that in order to recover the disaster-affected areas, it is necessary to thoroughly decontaminate and to reduce the volume of highly radioactive contaminants generated by the decontamination process and to strictly store them. The dyeing process was investigated. I was worried that the decontamination of radioactive contaminants was not progressing smoothly, but the cause was that there was a shortage of temporary storage for radioactive contaminated water generated in large quantities during the decontamination process. It was pointed out that there was.

  However, in order to promote the decontamination process, not only did the shortage of temporary storage spaces be resolved, but it was considered that it was necessary to study a purification method for radioactively contaminated water generated in the decontamination process.

  Separate and recover the radioactive contaminated water into radioactive contaminants and purified water, recover the collected purified water as decontamination water, and solidify and reduce the volume of highly radioactive contaminants. As a result of repeated sincerity studies, the present invention was completed as a result of thinking that it would be possible to significantly reduce the storage amount of radioactively contaminated water, eliminate the problem of temporary storage, and promote the decontamination treatment that has been stagnant.

  That is, the present invention separates and collects radioactive polluted water into radioactive pollutants and purified water, and the separated and collected purified water is recycled or discharged into decontamination water. This is a method for purifying radioactively contaminated water characterized by solidification and volume reduction.

  In FIG. 1, the method for purifying radioactive contaminated water according to the present invention comprises (1) iron ion addition treatment, (2) cesium coprecipitation reaction treatment, and (3) solid-liquid separation treatment. This can be done in order. Moreover, (4) water regeneration treatment and (5) solidification treatment can be further performed thereafter.

  In the iron ion addition process (1), iron ions are added to and mixed with radioactively contaminated water. For example, using a reaction vessel equipped with a stirrer and a heating device, after collecting radioactively contaminated water in the reaction vessel, adding ferrous sulfate crystals of iron salt, stirring and dissolving, ferrous ions And produce a mixed aqueous solution of radioactive contaminated water.

  At this time, the mixed ferrous ion forms a hydroxo ferrous complex ion composed of hexacoordinate water molecules, and the hydroxyl group (negative charge) of this iron complex ion is cesium ion (positive charge) and ion. Join. Thereby, an extremely dilute concentration of cesium ions in the contaminated water is captured, and an aqueous solution in which ferrous ions and cesium ions are intimately mixed is prepared.

  The cesium coprecipitation reaction treatment (2) is a method of generating a cesium-containing iron oxide precipitate by adding an alkali to the radioactively contaminated water treated with the addition of iron ions and oxidizing it by heating. This is a treatment consisting of iron colloid production, (2-2) GII colloid production, and (2-3) cesium-containing iron oxide precipitation production.

  (2-1) Iron hydroxide colloid generation is performed by adding less than one equivalent of alkali to iron ion to the radioactively contaminated water to which ferrous ions generated in the above treatment (1) are added and stirring and mixing. This is a treatment for producing ferrous hydroxide colloid in an aqueous solution having a pH value of 7.0 to 7.5. At this time, a so-called induced precipitation phenomenon occurs, in which a cadmium iodide type molecular structure of ferrous hydroxide colloid is formed, and at the same time, cesium ions that do not precipitate alone bind to the hydroxyl ions of ferrous hydroxide and precipitate. To do.

  (2-2) GII colloid is produced by stirring and mixing an aqueous solution of ferrous hydroxide colloid containing cesium produced in (2-1) at room temperature, so that hydroxylation can be achieved by slow oxidation of dissolved oxygen. The ferrous colloid is oxidized to produce a green last II (hereinafter referred to as GII) colloid as an intermediate oxide in an aqueous solution having a pH value of 6.0 to 6.5. At this time, since the GII colloid has a layered structure in which an equimolar phase of divalent iron and trivalent iron and a phase of hydroxyl group overlap closely, the hydroxyl ion of the GII colloid contains iron hydroxide colloid. Cesium is taken in to produce a cesium-containing GII colloid.

  (2-3) Cesium-containing iron oxide precipitates are produced by heating the aqueous solution of the cesium-containing GII colloid produced in (2-2) to a temperature of 50 ° C. or higher, and blowing in air to promote the oxidation reaction. A black-brown magnetic iron oxide precipitate is formed in an aqueous solution of 4.5-5.5. At this time, magnetic iron oxide precipitates composed of ultrafine particles take in cesium and precipitate as cesium-containing magnetic iron oxide particles.

  In the solid-liquid separation process (3), the aqueous reaction solution produced in (2-3) of the above-mentioned process (2) is subjected to solid-liquid separation, thereby converting the cesium-containing magnetic iron oxide precipitate into purified water from which cesium has been removed. It is a process of separating and collecting.

  In the solidification treatment (4), the cesium-containing magnetic iron oxide precipitate, which is a highly radioactive contaminant separated and recovered in the treatment (3), is formed and solidified with a solidifying agent. As a result, the volume can be reduced, and the place for radioactive contaminants can be used effectively.

  The water regeneration process (5) is a process for reclaiming the purified water collected in the process (3) to a decontamination process water by inspecting the water quality or discharging it as waste water.

  Ferrous sulfate and ferrous chloride ferrous salts and ferric salts are used as the iron salt added in the treatment with iron ion addition of radioactively contaminated water, but ferrous sulfate is most preferable for the formation of GII colloid. The amount of iron salt added is 0.001 to 1.000 mol / l in terms of iron ion concentration. When the amount is 0.001 mol / l or less, the amount of cesium-containing magnetic iron oxide produced is small and solid-liquid separation is difficult. When the amount is 1,000,000 mol / l or more, the amount of radioactive contaminants produced is excessive. Therefore, it is not preferable. Considering that the amount of cesium ions in the radioactively contaminated water is extremely small, the preferable amount is 0.005 to 0.500 mol / l.

  The amount of alkali added in the cesium coprecipitation reaction treatment is 0.9 equivalent or more and less than 1.0 equivalent with respect to iron ions in the aqueous solution. If it is less than 0.9 equivalent, the remaining iron ions will increase. On the other hand, if it is 1.0 equivalent or more, the purified water becomes strongly alkaline and is not preferable. Preferably, it is 0.95-0.99 equivalent.

  In the cesium coprecipitation reaction treatment, the heating oxidation temperature of the aqueous solution is 50 ° C to 80 ° C. At a temperature of 50 ° C. or lower, an amorphous non-magnetic iron oxide precipitate is formed and solid-liquid separation is difficult, and a temperature of 80 ° C. or higher is not preferable because energy consumption increases. A preferred temperature is 50 ° C to 70 ° C.

  An embodiment of the present invention will be described with reference to the configuration shown in FIG. In FIG. 2, S1, S2, and S3 are measuring devices each provided with a measuring instrument and a closing valve.

  First, a cesium coprecipitation reaction treatment is performed using a reaction treatment apparatus A including a reaction vessel equipped with a stirrer, a heating device, and an air oxidation device.

A predetermined amount of radioactively contaminated water in storage tank T1 is weighed into S1 and charged into the reaction tank of reaction processing apparatus A. While stirring with a stirrer, ferrous sulfate crystal powder in storage tank T2 is weighed in S2. A predetermined amount is put into a reaction vessel and dissolved at room temperature to prepare iron ion mixed radioactively contaminated water.
Subsequently, the sodium hydroxide crystals in the storage tank T3 are weighed by S3, and a predetermined amount is put into the reaction vessel, and stirred and mixed at room temperature, so that the aqueous solution has a pH value of 7.0 to 7.5. To produce a high-viscosity ferrous hydroxide colloid.

  The resulting ferrous hydroxide colloid aqueous solution is further stirred and mixed at room temperature, so that when the aqueous solution has a pH value of 6.0 to 6.5, green last (GII), which is an intermediate oxide of ferrous hydroxide. ) Produce a colloid.

  While the temperature of the aqueous GII colloid solution produced was heated to 50 ° C. using a heating device equipped in the reaction vessel, air was blown in using an air oxidizer to oxidize the GII colloid and A dark brown magnetic iron oxide precipitate is formed at a pH value of 5.0 to 5.5. At this point, the cesium coprecipitation reaction process is completed. The aqueous reaction treatment solution is taken out and transferred to the reaction treatment liquid take-out tank T4 by a pump P4.

  Next, solid-liquid separation processing is performed using a solid-liquid separation apparatus B composed of a magnetic separator.

  The cesium-containing magnetic iron oxide precipitation aqueous solution in the reaction liquid take-out tank T4 is transferred to the magnetic separator of the solid-liquid separator B by the transfer pump P5, and the cesium-containing magnetic iron oxide precipitation (high Radioactive contaminants) are magnetically separated, and the cesium-containing magnetic iron oxide precipitate is transferred to the radioactive contaminant recovery tank T5 by the transfer pump P6. At the same time, the separated purified water is transferred to the purified water recovery tank T6 by the transfer pump P7. To do.

  The radioactive contamination in the recovery tank T5 is transferred to the kneading machine 15 by the transfer pump P8, and then the calcined gypsum powder in the solid material storage tank T7 is put into the kneading machine 15 and mixed and kneaded. Volume of radioactive contaminants is reduced by pouring into a frame (not shown) and solidifying.

  On the other hand, the purified water in the recovery tank T6 is transferred to the decontamination water tank T8 by the transfer pump P10 and regenerated into purified water for the decontamination process. Or it transfers to the discharge tank T9 with the transfer pump P11, performs a water quality inspection according to the discharge standard of waste water, and discharges it after confirming that it is within the reference value.

(Experimental example)
Next, an experimental example will be described with reference to FIG.
In FIG. 3, a glass beaker having a volume of 1000 ml was used as the reaction tank 1, and a water bath was used as the heater 3. Further, a permanent magnet was used as the magnetic separation device 9, a 300 ml glass beaker and a glass rod were used as the kneading and molding device 15, and a 50 ml plastic container was used as the mold, and the kneaded material was poured into this and solidified.

  Radioactive contaminated water is water in which non-radioactive cesium 133 carbonate is dissolved in ion-exchanged water.

The solution was simulated radio-polluted water. 1000 ml of simulated contaminated water A having a cesium concentration of 780 mg / l (liter) was prepared and prepared.

  The raw materials used in the experiment were cesium carbonate, ferrous sulfate heptahydrate and sodium hydroxide, and reagent grade products were used, and water was ion-exchanged water. Commercially available calcined gypsum was used as the solidifying agent.

  The precipitate was analyzed using an X-ray diffractometer, and cesium was analyzed using an atomic absorption analyzer (manufactured by VARIAN, AA240FS).

(Experimental example 1)
The effect of cesium ion precipitation removal in cesium coprecipitation treatment is confirmed.

Experimental conditions;
1000 ml of the simulated radioactive contaminated water A (hereinafter referred to as contaminated water A) prepared in advance was weighed 600 ml in the contaminated water measuring tank 6, and the contaminated water charging cock 21 was opened and charged into the reaction tank 1. Next, while stirring the contaminated water A using the stirrer 2, 25 g of ferrous sulfate heptahydrate crystal powder is measured with the iron salt measuring container 7, and the iron salt charging cock 22 is opened and charged into the reaction tank 1. Then, it was dissolved at room temperature to prepare a mixed water of contaminated water A and ferrous ions.

  After stirring for 30 minutes, 6.5 g of granular sodium hydroxide is weighed with an alkali metering vessel 8, the alkali charging cock 23 is opened and charged into the reaction vessel 1, and stirred and mixed at room temperature, a bluish white colloid in the aqueous solution Generated. The aqueous solution at this time had a temperature of 20 ° C. and a pH value of 7.4 by the pH meter 4. 20 ml of this bluish white colloid aqueous solution was collected for analysis in a 20 ml graduated cylinder, and the sample number was (SA-1).

  When the blue-white colloid aqueous solution having a pH value of 7.4 was further stirred at room temperature, the color of the colloid changed to dark green after 60 minutes. The dark green colloid aqueous solution at this time had a temperature of 20 ° C. and a pH value of 6.5 by the pH meter 4. 20 ml of this dark green colloid aqueous solution was collected for analysis in a 20 ml graduated cylinder, and the sample number was (SA-2).

  While stirring the dark green colloid aqueous solution having a pH value of 6.5, the aqueous solution temperature was heated to 50 ° C. by the heater 3, and air was blown by the air blowing device 5 at a speed of 50 ml / min. After 60 minutes from the start of air blowing, the pH value of the aqueous solution decreased from 6.5 to 4.5 by the pH meter 4, the GII colloid changed to a black precipitate, and the oxidation reaction of the GII colloid was completed. The produced reaction treatment liquid was 560 ml. 20 ml of this black precipitate-dispersed aqueous solution was collected in a 20 ml cylinder for analysis, and the sample number was (SA-3).

Experimental result;
Sedimentation characteristics according to sedimentation volume after 24 hours of each sample of (SA-1), (SA-2) and (SA-3), test of filtration characteristics using analytical filter paper, and cesium content of the collected supernatant Each amount was measured. The measurement results are shown in Table 1.

＊汚染水Ａのセシウム濃度；７８０（mg／l）

* Cesium concentration in contaminated water A: 780 (mg / l)

  As a result of X-ray analysis of the precipitate of each sample, SA-1 was ferrous hydroxide, SA-2 was green last G-II, and SA-3 was magnetic iron oxide magnetite. The sedimentation volume was excellent for SA-3, and the other two samples were poor. Filterability was poor in all three samples, and solid-liquid separation seemed difficult. However, only the magnetic (SA-3) could be solid-liquid separated by a magnetic separation apparatus described later. From these results, it was confirmed that all three samples had a cesium coprecipitation reaction treatment effect. Thereby, it was confirmed that the cesium coprecipitation treatment was completed by performing the reaction (SA-3).

Discussion of experimental results;
From the results in Table 1, all three samples have a cesium coprecipitation reaction effect, because any product has an anionic hydroxyl group, and has a function of attracting and adsorbing cationic cesium ions. The ultrafine iron hydroxide colloidal particles and magnetic iron oxide precipitation are thought to be due to the increased contact opportunities with cesium ions. Furthermore, solid particles can be separated even with fine particles that leak through the filter paper for chemical analysis. Magnetic separation is possible because the ultrafine particles generated by the cesium coprecipitation reaction process are magnetic iron oxide precipitates. It depends on what you did.

(Experimental example 2)
Confirm the effect of magnetic separation in solid-liquid separation process.

Experimental conditions;
While stirring 540 ml of the reaction treatment liquid of Experimental Example 1 from the reaction vessel 1 with the stirrer 2, the reaction treatment liquid transfer pump 20 takes out the reaction treatment liquid as a magnetic separator 9 into a 1000 ml glass beaker with a permanent magnet attached to the bottom of the beaker. Magnetic separation treatment was performed.

Experimental result;
The black precipitation-dispersed aqueous solution taken out into a glass beaker with a permanent magnet attached to the bottom was left after being taken out. When 5 minutes had passed after standing, black precipitates were magnetically aggregated at the bottom of the beaker. Therefore, solid-liquid separation was performed by the gradient method. The black sedimentary mud obtained by separation by magnetic agglomeration is transferred to a 300 ml glass beaker as a radioactive pollutant recovery tank 13 by a recovery mud contaminant transfer pump 27, and purified water is purified by a transfer pump 24. The water storage tank 10 was transferred to a 1000 ml glass beaker. In each case, 30 ml of muddy black magnetic iron oxide precipitate and 510 ml of purified water were obtained.

  As a result, it was confirmed that the magnetic separation treatment by the permanent magnet has an effect of performing the solid-liquid separation treatment by capturing the dispersed ultrafine particles with a magnetic force and magnetically aggregating them within a short time of 5 minutes.

Discussion of experimental results;
The reason why magnetic aggregation occurs in a short time is considered that the magnetized fine particles themselves form a magnetic gradient while increasing the number of magnetized particles to form a magnetic aggregation structure.

(Experimental example 3)
Check the degree of purification of reclaimed water in the water reclamation process.

Experimental conditions;
510 ml of purified water stored in the storage tank 10 of Experimental Example 2 was transferred to the reclaimed water storage tank 11 by the purified water transfer pump 26 and regenerated into decontamination water.

Experimental result;
As a result of analyzing this regenerated water, the cesium concentration was 5 mg / l and the pH value was 4.8.

  It was confirmed that the cesium concentration in the reclaimed water was purified water obtained by removing 99% of cesium ions in the contaminated water A.

Discussion of experimental results;
This indicates that cesium in the contaminated water can be removed by magnetically aggregating the ultrafine magnetic iron oxide particles adsorbed with cesium and separating them into solid and liquid.

(Experimental example 4)
Confirm the effect of reducing the volume of radioactive contaminants in the solidification process.

Experimental conditions;
As a result of analyzing the components of 30 ml of a muddy black precipitate contained in the radioactive contaminant collection tank 13 of Experimental Example 2, it was a muddy substance consisting of 21 g of cesium-containing iron oxide precipitate and 27 g of water content. This black mud is transferred to a 300 ml glass beaker as a kneading and forming device 15 by means of a transfer pump 28, while 145 g of calcined gypsum powder as a solidifying agent is measured by a solidifying agent measuring device 14, 29 is opened and put into a 300 ml glass beaker as the kneading and forming apparatus 15, and the black mud and calcined gypsum powder are kneaded using a glass rod as a kneading machine, and the kneaded product is 50 ml (20H × 50W × 50L) And poured into a plastic case (not shown).

Experimental result;
Three hours after the kneaded material was poured into the plastic case, the kneaded material was solidified. Then, a molded body having a weight of 190 g and a volume of 40 ml was obtained. This result indicated that 540 ml of contaminated water A had a 93% volume reduction to 40 ml solids. This confirmed that the solidification treatment had a large volume reduction effect.
Discussion of experimental results;
This means that a cesium-containing magnetic iron oxide precipitate is produced by a cesium coprecipitation reaction treatment, and this reaction product is subjected to solid-liquid separation treatment by a magnetic separation device, and muddy radioactive contaminants and purified water are collected and recovered. This is the effect of volume reduction obtained by solidifying the muddy material to form a solid. This effect also contributes to the solution of the radioactive contamination storage problem.

The present invention separates and recovers contaminated water generated by decontamination treatment into purified water and cesium-containing contaminants, recycles the purified water as decontamination treatment water, solidifies the cesium-containing contaminants, and performs radioactivity. This is a method for purifying radioactively contaminated water to reduce the volume of pollutants. This eliminates the problem that currently impedes the most important decontamination process in radioactively contaminated areas, that is, the problem of insufficient storage space for radioactively polluted wastewater generated as a result of the decontamination process. The dyeing process can be promoted.
In implementation, no special equipment is required, and materials used for processing are also available at a low cost, enabling energy-saving and ecological implementation.

1 Reaction tank 2 Stirrer
3 Heating heater 4 pH meter and electrode 5 Air blowing device 6 Contaminated water measuring tank 7 Iron salt measuring container 8 Alkali measuring container 9 Magnetic separation device 10 Purified water storage tank 11 Reclaimed water storage tank 12 Discharge drainage tank 13 Radioactive contaminant recovery Tank 14 Solidifying agent measuring container
15 Kneading and Forming Device 16 Storage Station for Radioactive Contaminants 20 Reaction Treatment Liquid Transfer Pump 21 Contaminated Water Input Cock 22 Iron Salt Input Cock 23 Alkali Input Cock 24 Recovery Purified Water Transfer Pump 25 Drainage Discharge Pump 26 Purified Water Transfer Pump 27 Collected Mud Contaminant Transfer Pump 28 Collected Mud Contaminant Input Cock 29 Solidifying Agent Input Cock

Claims (8)

A method for purifying radioactively contaminated water,
Iron ion addition treatment for adding and mixing iron ions into the radioactively contaminated water,
Addition of alkali to the radioactively contaminated water subjected to the iron ion addition treatment, and heat oxidation to produce a cesium-containing iron oxide precipitate, cesium coprecipitation reaction treatment,
A solid-liquid separation treatment for separating the aqueous solution produced by the cesium coprecipitation reaction treatment into purified water and a cesium-containing iron oxide precipitate;
A method for purifying radioactively contaminated water, comprising:   The iron salt to be added in the iron ion addition treatment is ferrous sulfate, and the addition treatment amount is 0.001 to 1.000 mol / l (liter) in terms of iron ion concentration. Purification method for radioactively contaminated water.   In the cesium coprecipitation treatment, the alkali to be added is at least one of sodium hydroxide, calcium hydroxide, and magnesium hydroxide, and the addition amount is 0.9 equivalents or more and 1.0 equivalents with respect to the iron ion amount. The method for purifying radioactively contaminated water according to claim 1 or 2, characterized in that the amount is less.   In the said cesium coprecipitation reaction process, heating oxidation is the heating temperature of 50 to 80 degreeC, The purification processing method of the radioactive contamination water in any one of Claim 1 thru | or 3 characterized by the above-mentioned.   The method for purifying radioactively contaminated water according to any one of claims 1 to 4, wherein in the solid-liquid separation treatment, a magnetic separation device is used for solid-liquid separation.   6. The purification treatment method according to claim 1, further comprising a solidification treatment in which the separated and recovered cesium-containing iron oxide precipitate is formed and solidified with a solidifying agent.   The method for purifying radioactively contaminated water according to claim 6, wherein calcined gypsum and / or cement is used as a solidifying agent in the solidification treatment.   The purification treatment method according to any one of claims 1 to 7, further comprising a water regeneration treatment for regenerating the separated purified water as decontamination treatment water or discharging it as waste water.

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