JP6363399B2 - Method and apparatus for treating radioactive material adsorbent - Google Patents

Description

  Embodiments described herein relate generally to a radioactive material adsorbent processing method and a processing apparatus.

  Various methods have been proposed for recovering and immobilizing radioactive materials from incinerated ash containing radioactive materials such as radioactive cesium.

  For example, radioactive cesium is recovered by using a zeolitic mineral such as mordenite as a radioactive substance adsorbent. In this case, since a large amount of zeolitic mineral is used, the cost and the amount of waste become large. For this reason, it has been tried to use ferrocyanide such as Prussian blue (bitumen (ferric ferrocyanide)) as an adsorbent for radioactive substances instead of zeolitic minerals.

Ferrocyanide can be mass-produced economically and has a small dissociation constant ( ^{K≈10 −36} ) of CN ⁻ . In addition, ferrocyanide has a high adsorbability for adsorbing radioactive substances such as radioactive cesium.

  However, ferrocyanides may release cyan at high concentrations in environments with high pH, environments exposed to ultraviolet light, and reducing atmospheres. As a final disposal of the radioactive material adsorbent, it is considered to be buried in the ground for disposal, but it may be immersed in rainwater or groundwater after being buried, and cyan may be eluted.

  As a general countermeasure against cyanide, it is known to decompose cyanide by oxidative decomposition, biodegradation and photolysis. It is also known to separate free cyanide by precipitation separation, gas layer separation, and two-layer separation using a reverse osmosis membrane. However, with these methods, it is difficult to efficiently treat the radioactive material adsorbent on which the radioactive material is adsorbed.

Japanese Patent No. 3867306 Japanese Patent No. 5024876

  The present invention relates to a radioactive substance adsorbent processing method and a radioactive substance capable of efficiently suppressing elution of cyanide and efficiently treating a radioactive substance adsorbent containing a ferrocyanide adsorbed with a radioactive substance. It is an object of the present invention to provide an adsorbent treatment apparatus.

  One aspect of the method for treating a radioactive material adsorbent of the present invention is a method of treating a radioactive material adsorbent containing a ferrocyanide adsorbed with a radioactive material, the radioactive material adsorbent and alumina as a cyan adsorbent It is characterized by comprising a mixing step of mixing an aluminum mineral or magnesium oxide mineral and an aluminum silicate salt.

  One aspect of the radioactive substance adsorbent treatment apparatus of the present invention is an apparatus for treating a radioactive substance adsorbent containing a ferrocyanide adsorbed with a radioactive substance, the radioactive substance adsorbent, the cyan adsorbent, and the aluminum silicate. A mixing unit for mixing salt, a radioactive material adsorbent adding unit for adding the radioactive material adsorbent to the mixing unit, a cyan adsorbent adding unit for adding the cyan adsorbent to the mixing unit, and the mixing unit And an aluminum silicate salt addition section for adding the aluminum silicate salt to the base.

  According to the present invention, a radioactive material adsorbent containing a ferrocyanide adsorbed with a radioactive substance can be efficiently treated by efficiently suppressing the elution of cyanide and the radioactive substance adsorbent. An apparatus for treating a radioactive material adsorbent can be provided.

The flowchart which shows the processing method of the radioactive substance adsorbent which concerns on embodiment. The figure which shows typically the processing apparatus of the radioactive substance adsorbent which concerns on embodiment. The graph which shows the result of the cyan elution test of the ferrocyanide in an Example. The graph which shows the relationship between the addition amount of each component of the molded object in the cyan | silicone elution test of an Example, and the total cyan concentration which eluted. The figure which shows the X-ray-diffraction (XRD) measurement result of the magnesium oxide type mineral used in the Example. The figure which shows the XRD measurement result of the halloysite used in the Example.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a flowchart showing a method for treating a radioactive substance adsorbent according to an embodiment. In the radioactive substance adsorbent treatment method of the present embodiment, in the mixing step S1, the radioactive substance adsorbent 1 that adsorbs the radioactive substance, the cyan adsorbent 2, the aluminum silicate salt 3, and the iron compound 5 as necessary. And add. And after mixing these, the mixture 4 is press-molded by shaping | molding process S2, and the molded object 6 is formed.

The radioactive material adsorbent 1 includes, for example, a ferrocyanide such as Prussian blue (bitumen (ferric ferrocyanide)) represented by the following general formula (A).
M ⁴⁺ [Fe (II) (CN) ₆ ] ⁴⁻ (M = Fe, Co, Ni, K, Na, NH _4, etc.)
... (A)

The cyan adsorbent 2 is an inorganic adsorbent having an adsorption performance for anions, and adsorbs ferrocyanide ions ([Fe (II) (CN) ₆ ] ⁴⁻ ). As the cyan adsorbent 2, an alumina-based mineral or a magnesium oxide-based mineral can be used. An alumina type mineral or a magnesium oxide type mineral may be used individually by 1 type, and may use 2 or more types together.

  As an alumina type mineral, the hydrotalcite shown by the following general formula (B) can be used, for example.

[Mg ₆ Al ₂ (OH) ₁₆ CO ₃ .4H ₂ O] (B)

The alumina-based mineral holds an anion (particularly carbonate ion (CO ₃ ²⁻ )) between layers, and adsorbs CN ⁻ by substitution of the anion. In particular, the anion adsorption performance can be improved by performing a decarboxylation treatment by heating.

  The addition amount of the cyan adsorbent 2 is preferably 25 to 250 parts by mass with respect to 100 parts by mass of the radioactive substance adsorbent 1. When the addition amount of the cyan adsorbent 2 is less than 25 parts by mass, the elution of cyan from the molded body 6 may not be sufficiently suppressed. On the other hand, if it exceeds 250 parts by mass, there may be a problem of increased waste.

  The aluminum silicate salt 3 acts as a binding material. As the aluminum silicate salt 3, for example, halloysite represented by the following general formula (C) can be used.

Al ₂ Si ₂ O ₅ (OH) ₄ (C)

  Ferrocyanide ions are likely to be eluted from the ferrocyanide when the pH of the immersion liquid is 7 or more neutral or alkaline, and the amount of cyanide eluted tends to increase. In this embodiment, by adding the aluminum silicate salt 3 as a binding material, the pH when the molded body 6 is immersed in water can be maintained at about 4 or less. Therefore, the elution of cyan from the molded body 6 can be suppressed.

  The addition amount of the aluminum silicate salt 3 is preferably 50 to 600 parts by mass and more preferably 100 to 600 parts by mass with respect to 100 parts by mass of the radioactive substance adsorbent 1. When the addition amount of the aluminum silicate salt 3 is less than 50 parts by mass, the elution of cyan from the molded body 6 may not be sufficiently suppressed. On the other hand, when the amount exceeds 600 parts by mass, there may be a problem that the amount of waste increases.

  Moreover, you may add the iron compound 5 further by mixing process S1. The iron compound 5 reacts with ferrocyanide ions eluted from the molded body 6 in an aqueous solution to produce ferrocyanide. Therefore, by using the iron compound 5, it is possible to suppress the elution of cyanide. As the iron compound 5, if it is a compound containing iron, it will not specifically limit, 1 type may be used independently and 2 or more types may be used together.

Examples of the iron compound 5 include FeCl ₂ (iron chloride II), Fe ₃ O ₄ (iron oxide (II, III)), Fe ₂ O ₃ (iron oxide (III)), [Fe (OH) ₂ ] (hydroxide Iron (II)), [Fe (OH)] (iron hydroxide (I)), FeSO ₄ (iron sulfate (II)), Fe ₂ SO ₄ (iron sulfate (I)), and the like can be used. As the iron compound 5, an iron compound 5 containing divalent iron is preferable, and FeSO ₄ , FeCl ₂ , Fe ₃ O ₄ , and [Fe (OH) ₂ ] are more preferable from the viewpoint of excellent cyan elution suppression effect. .

  It is preferable that the addition amount of the iron compound 5 is 25-50 mass parts with respect to 100 mass parts of the radioactive substance adsorbent 1. By adding 25 parts by mass or more of the iron compound, it is possible to sufficiently obtain the effect of improving the suppression of cyanide elution. On the other hand, when it exceeds 50 mass parts, the malfunction of the amount of waste may arise.

(Molding process S2)
The molding step S2 is a step of obtaining the molded body 6 by press molding the mixture 4 mixed in the mixing step S1. In the molding step S2, for example, the mixture 4 is press-molded using a compression molding machine. For example, the press molding is performed under molding conditions where the pressure is about 550 kg / cm ² and the compression time is about 10 to 15 minutes.

  As described above, according to the method for treating a radioactive substance adsorbent of the present embodiment, for a radioactive substance adsorbent containing a ferrocyanide adsorbed with a radioactive substance, it is possible to efficiently suppress cyan elution and treat the radioactive substance adsorbent efficiently. it can.

Next, an embodiment of the processing apparatus for the radioactive material adsorbent of the present invention will be described.
FIG. 2 is a schematic view showing the radioactive substance adsorbent processing apparatus 30 of the present embodiment. The radioactive substance adsorbent treatment apparatus 30 of this embodiment includes a mixing unit 31. Also, a radioactive material adsorbent addition unit 32 for adding the radioactive material adsorbent 1 to the mixing unit 31, a cyan adsorbent addition unit 33 for adding the cyan adsorbent 2 to the mixing unit 31, and an aluminum silicate salt in the mixing unit 31 3 is provided with an aluminum silicate salt addition section 34 to which 3 is added. Further, the radioactive substance adsorbent processing apparatus 30 includes an iron compound addition unit 35 that adds the iron compound 5 to the mixing unit 31 as necessary.

  In the radioactive substance adsorbent processing apparatus 30, the mixing unit 31 mixes the added radioactive substance adsorbent 1, cyan adsorbent 2, aluminum silicate salt 3, and iron compound 5 used as necessary, to form a mixture 4. To prepare. In addition, the radioactive substance adsorbent processing apparatus 30 includes a molding unit 36, and the molding unit 36 press-molds the mixture 4 to form the molded body 6.

  According to the radioactive substance adsorbent processing apparatus of this embodiment, cyanide elution can be efficiently suppressed and the radioactive substance adsorbent containing ferrocyanide adsorbed with the radioactive substance can be efficiently processed.

[Cyanide dissolution test]
For the ferrocyanide, a cyan dissolution test was performed as follows.
50 ml of pure water was added to 5 g of ferrocyanide (liquid / solid ratio: 10 mL / g), and samples were prepared with pH adjusted to 5, 7, and 12 using NaOH (sodium hydroxide) and HCl (hydrochloric acid), respectively. did. Each sample was stirred for 6 hours at 200 rpm. Then, the total cyan density | concentration in a solution was measured using the autoanalyzer (BELTEC company make, AACS IV) according to JISK0102: 2013 38.1 and 38.3. The results are shown in FIG.

  From FIG. 3, it can be seen that when the pH of the solution is 5 or less, the concentration of all cyan eluted is significantly suppressed as compared with the case where the pH of the solution is 7 or more.

(Example 1)
[Cyanide dissolution test 1 for molded products]
100 parts by mass (1 g) of the same ferrocyanide prepared in the “cyan elution test”, 200 parts by mass of magnesium oxide mineral (MgO) as a cyan adsorbent, 200 parts by mass of ordinary Portland cement, pure water Was added and mixed. Thereafter, the mixture was compressed and molded at a pressure of 550 kg / cm ² for 10 to 15 minutes to obtain a molded body No1 having a diameter of 30 mm and a thickness of 2 to 3 mm.

  Further, to 100 parts by mass of ferrocyanide, 300 parts by mass of magnesium oxide mineral, 600 parts by mass of halloysite which is an aluminum silicate salt, 200 parts by mass of pure water are added and mixed, and molded in the same manner as above. Molded body No2 was obtained.

  The molded bodies Nos. 1 and 2 were subjected to the same cyan elution test as the above “cyan elution test”. After stirring, the pH of the solution in which the molded body No1 was immersed changed to 9, and the pH of the solution in which the molded body No2 was immersed changed to 4. Table 1 shows the amount of each component added to the molded bodies Nos. 1 and 2 and the results of the cyan dissolution test. The results of the cyan dissolution test are shown in the graph of FIG. In addition, also about the molded object produced using the hydrotalcite which is an alumina type mineral as a cyan adsorbent, the result equivalent to molded object No2 was obtained about the cyan elution test. Moreover, the X-ray diffraction (XRD) measurement result of the magnesium oxide type mineral used in this test is shown in FIG. 5, and the XRD measurement result of halloysite is shown in FIG.

(Example 2)
[Cyanide dissolution test 2]
Pure water was added to 100 parts by mass (1 g) of ferrocyanide similar to that prepared in the “cyan elution test”, and further, halloysite as a binding material was added at a mass ratio shown in Table 2, respectively. In the same manner, moldings Nos. 3 to 8 were obtained.
For molded bodies Nos. 3 to 8, a cyan elution test was conducted in the same manner as in Example 1. Table 2 shows the amount of each component added and the results of the cyan dissolution test in the molded bodies Nos. 3 to 8.

(Example 3)
[Cyanide dissolution test 3]
In 100 parts by mass (1 g) of the same ferrocyanide prepared in the “cyanide dissolution test”, the same magnesium oxide-based mineral, halloysite, and FeSO ₄ (iron sulfate) as in Example 1 were used in the mass proportions shown in Table 3. Then, molded bodies No. 9 and 10 were obtained in the same manner as in Example 1.

  For molded bodies Nos. 9 and 10, a cyan elution test was performed in the same manner as in Example 1. Table 3 shows the amount of each component added and the results of the cyan elution test for molded bodies Nos. 9 and 10.

  From Table 1, the molded body No2 produced by adding magnesium oxide mineral and halloysite to ferrocyanide becomes acidic with a pH of about 4 or less, and normal portland cement is used instead of halloysite. It can be seen that, compared to the molded body No. 1, the total cyanide concentration that was eluted could be greatly suppressed. Moreover, from Table 2, it can be seen that, for molded bodies Nos. 4 to 8 produced by adding magnesium oxide-based minerals and halloysite to ferrocyanide, the total cyanide concentration eluted can be significantly suppressed. Moreover, it can be seen from Table 3 that, in the molded bodies No. 9 and 10 produced by adding iron sulfate, the total cyan concentration eluted is further suppressed than the molded bodies No. 4 to 8.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the 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 1 ... Radioactive material adsorption agent, 2 ... Cyan adsorption agent, 3 ... Aluminum silicate salt, 4 ... Mixture, 5 ... Iron compound, 6 ... Molded object, 30 ... Processing apparatus of radioactive material adsorption agent, 31 ... Mixing part, 32 ... Radioactive material adsorbent addition part, 33 ... Cyan adsorbent addition part, 34 ... Aluminum silicate addition part, 35 ... Iron compound addition part, 36 ... Molding part, S1 ... Mixing process, S2 ... Molding process.

Claims (7)

A method for treating a radioactive material adsorbent containing ferrocyanide adsorbed with a radioactive material, comprising:
A method for treating a radioactive substance adsorbent comprising a mixing step of mixing the radioactive substance adsorbent, an alumina mineral or magnesium oxide mineral as a cyan adsorbent, and an aluminum silicate salt.   The method for treating a radioactive substance adsorbent according to claim 1, further comprising mixing an iron compound in the mixing step.   The method for treating a radioactive material adsorbent according to claim 2, wherein the iron compound is iron (II) sulfate.   The radioactive substance adsorbent according to any one of claims 1 to 3, wherein the addition amount of the aluminum silicate salt is 50 to 600 parts by mass with respect to 100 parts by mass of the radioactive substance adsorbent. Processing method. The additive amount of the cyan adsorbent, before Symbol radioactive material adsorbent according to any one of claims 1 to 4, characterized in that 25 to 250 parts by weight per 100 parts by weight radioactive material adsorbent Processing method.   The method for treating a radioactive substance adsorbent according to any one of claims 1 to 5, further comprising a molding step of pressing the mixture obtained in the mixing step to obtain a molded body. An apparatus for treating a radioactive material adsorbent containing ferrocyanide adsorbed with a radioactive material,
A mixing part for mixing the radioactive substance adsorbent, the cyan adsorbent and the aluminum silicate salt;
A radioactive substance adsorbent addition part for adding the radioactive substance adsorbent to the mixing part;
A cyan adsorbent addition unit for adding the cyan adsorbent to the mixing unit;
An apparatus for treating a radioactive material adsorbent, comprising: an aluminum silicate salt addition unit that adds the aluminum silicate salt to the mixing unit.

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