JPH10221491A - Processor for waste liquid containing plutonium using tannin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a processor for waste liquid containing plutonium with small residue after processing the waste liquid which fulfills the drain water standards and consists of a small and single process with easy operation. SOLUTION: The process systems of a waste liquid processor are separated into a high radioactivity level waste liquid processing system and a low radioactivity level waste processing system which each are placed in a glove box 10 and a glove box 12 connected in series. In the glove box 10, the high radioactivity level waste liquid from a waste liquid receiving tank 20 is supplied in turn to an adsorption towers 30, 30b and 30c charged with insoluble tannin and passed waste liquid is supplied to a monitor tank 40a. If the waste liquid is confirmed to be specific low radioactivity level in the monitor tank 40a, this waste liquid is supplied in turn to adsorption towers 50a and 50b charged with the insoluble tannin in the glove box 12. The passed waste liquid is supplied to the monitor tank 40b to be drained if the radioactivity level in the waste liquid fulfills the drain water standards.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus for treating plutonium-containing waste liquid, and more particularly to an apparatus for treating plutonium-containing waste liquid using tannin as an adsorbent.

[0002]

2. Description of the Related Art FIG. 2 shows a process for reprocessing spent nuclear fuel. Spent nuclear fuel is used in the reprocessing process.
After dissolving in a nitric acid solution to form a nitrate, an actinoid-based element such as uranium (U) and plutonium (Pu) is separated and collected as a nitrate using an organic solvent (S101).
Thereafter, in the conversion step, the solutions recovered from each are mixed, and then the nitrates such as U and Pu in the mixed solution are denitrated, and the obtained powder composed of UO ₂ and PuO ₂ is roughly pulverized and further roasted. By baking, a powder composed of U ₃ O ₈ and PuO ₂ is obtained, and this powder is further reduced to obtain UO ₂ , PuO ₂
(S102). Further, in the fuel production process, the MOX powder is formed into a pellet by press working or the like to produce a MOX fuel body (S103).

At the time of pellet formation in the above fuel production process, there are cases where pellets are formed or pellets contain impurities. Such pellets are collected as scrap (S104). Then, the scrap is again dissolved in a nitric acid solution, solvent extraction is performed, and impurities are removed. Then, the scrap is returned to the fuel manufacturing process again, and becomes a raw material of the MOX fuel body.

[0004] In the reprocessing of spent nuclear fuel as described above, the waste liquid containing plutonium and the like is mainly generated during the solvent extraction in the scrap collecting step (S104). Plutonium has a specific activity per unit weight of about 3 to 4 orders of magnitude higher than uranium. The wastewater standards are defined by the radioactivity per unit volume of wastewater, regardless of the contained substances. Therefore, in order to satisfy the drainage standard, it is necessary to reduce the allowable weight of Pu per unit volume of drainage by about 3 to 4 digits as compared with U.

Therefore, conventionally, for example, as shown in FIG.
Pu in the waste liquid is removed and adsorbed by passing the waste liquid containing Pu through coagulation sedimentation treatment and a plurality of stages of adsorption towers filled with a plurality of adsorbents, thereby reducing the amount of radioactivity in the wastewater. More specifically, the conventional waste liquid treatment apparatus is shown in FIG.
As shown in FIG. 2, two glove boxes, each of which is a closed type waste liquid treatment chamber, are connected in series. The glove box 10 is a primary treatment chamber for treating Pu in a high radioactivity level waste liquid, and the glove box 12 processes Pu in the waste liquid reduced to a low radioactivity level in the glove box 10. This is a secondary processing room. The glove box 10 is provided with a waste liquid receiving tank 20 for receiving a high radioactive level waste liquid. The high radioactive level waste liquid is supplied from the waste liquid receiving tank 20 to the coagulation sedimentation tank 60. Coagulation sedimentation tank 6
Numeral 0 is composed of three stages, and an aggregating agent (eg, ferric chloride, polymer aggregating agent) and the like and reagents are supplied to the aggregating and sedimenting tank 60, whereby plutonium is precipitated as a hydroxide (coprecipitation method). . Then, the finished liquid is supplied to the two adsorption towers filled with the activated carbon beads, and the Pu in the finished liquid is further adsorbed. The waste liquid that has passed through the activated charcoal adsorption tower 70 is supplied to the monitor tank 40a. . Then, in the monitor tank 40a, the radioactivity level is measured, and an inspection is performed as to whether or not the radioactivity can be supplied into the glove box 12, which is a low radioactivity level processing chamber in the next process. This is to prevent the waste liquid having a high radioactivity level being supplied to the glove box 12 from contaminating the inside of the glove box 12 with radioactivity and preventing the radioactivity level of the final waste liquid from reaching the target value. In the monitoring tank 40a, when it is confirmed that the waste liquid is a predetermined low-activity level waste liquid, the low-activity level waste liquid is
The glove box 12 is supplied to a zinc chloride electrodeposited activated carbon adsorption tower 80 filled with lead chloride electrodeposited activated carbon. In the four zinc chloride electrodeposited activated carbon adsorption towers 80, Pu in the waste liquid is further adsorbed, and the low radioactivity level waste liquid is further subjected to Pu adsorption treatment in the chelate resin adsorption tower 90 and supplied to the monitor tank 40b. In the monitor tank 40b, the radioactivity level in the waste liquid is measured, and is discharged if the wastewater standard is satisfied. If the effluent standards are not met,
Further, a tertiary processing chamber is provided.
Is discharged, and the amount of radioactivity in the waste liquid is reduced before being discharged.

[0006]

However, in the case of the above-mentioned treatment step, a large amount of by-product sludge comprising a hydroxide of Pu produced by coagulation precipitation, a coagulant, and the like is generated. There is a problem of how to perform final treatment and disposal of this by-product sludge.

[0007] Further, in the treatment process, the work contents such as extraction, dehydration, washing, roasting and storage of sediment are complicated, and a plurality of treatment methods and devices are required. There was a problem that would be.

[0008] In addition to the above-mentioned treatment processes, ion exchange, evaporation, microwave heating, membrane separation, and the like are employed as waste liquid treatment methods in facilities handling nuclear fuel materials. The generation of secondary by-products is inevitable,
Similar to the above-described processing steps, not only the work content becomes complicated, but also a plurality of processing methods and devices are required, and there is a problem that the waste liquid processing apparatus becomes large as a whole.

Further, in order to reduce the allowable weight of Pu per unit volume of wastewater by about three to four orders of magnitude as compared with U and satisfy the wastewater standard, it is necessary to constitute a single treatment facility with a conventional adsorbent or the like. It was difficult. For this reason, it is necessary to combine a plurality of processing methods, and there has been a problem that the processing equipment is increased in size and operation and construction costs are increased. The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to treat a plutonium-containing waste liquid having a small amount of residue after waste liquid treatment, comprising a simple single treatment process which is easy to operate while meeting drainage standards. It is to provide a device.

[0010]

Means for Solving the Problems To solve the above problems, the apparatus for treating a plutonium-containing waste liquid according to the present invention has the following features.

(1) At least two adsorption towers filled with an adsorbent composed of insoluble tannin are connected in series.

Insoluble tannins are disclosed in JP-A-5-66291.
Uranium and transuranium elements are adsorbed very efficiently as described in Japanese Patent Application Publication No. Here, insoluble means that it does not dissolve in any of water, acid and alkali. Therefore, the adsorption tower filled with this insoluble tannin has P
If the waste liquid containing u is passed through at least two or more towers, Pu in the waste liquid is adsorbed on the insoluble tannin, and the wastewater standard can be satisfied by a single treatment process without being combined with other methods. Therefore, it is possible to provide a waste liquid treatment apparatus that is simple and easy to operate. In addition, tannin has a high Pu adsorption ability, so that the adsorption tower can be downsized. Therefore, it is possible to reduce the size of the entire device. Furthermore, since insoluble tannin is composed of carbon, hydrogen and oxygen, if the used adsorbent that has lost the ability to adsorb Pu is incinerated, the insoluble tannin, which is an adsorbent, becomes a gas such as carbon dioxide and water vapor, contaminating the outside world. It can be released without doing. On the other hand, trace amounts of U and Pu adsorbed on the insoluble tannin are oxidized to uranium oxide and plutonium oxide. These oxides can be, for example, MOX powder, and the residue after waste liquid treatment can be reduced as much as possible.

(2) The apparatus for treating a plutonium-containing waste liquid using tannin according to (1), further comprising:
The at least two adsorption towers are connected in series to at least two or more closed waste liquid treatment chambers having different levels of radioactivity treatment, and the at least two or more closed waste liquid treatment chambers are connected in series with each other. They are connected and arranged. Therefore, by dividing into at least two or more closed type waste liquid treatment chambers, it is possible to divide the treatment radioactivity level in each treatment chamber. For example, if wastewater treatment is performed only in one closed wastewater treatment chamber, the radioactive contamination of the closed wastewater treatment chamber by the high radioactivity-level wastewater will result in the radioactivity level of the final treatment liquid passing through the adsorption tower. May not be able to reach the target value. As described above, by dividing into at least two or more closed waste liquid treatment chambers, it is possible to prevent the final treatment waste liquid (that is, waste water) from being exposed to the high radioactivity level waste liquid and not meeting the waste water standards. Thereby, the drainage standard can be satisfied.
Further, since at least two or more closed-type waste liquid treatment chambers are connected to each other in series, waste liquid treatment can be performed continuously.

(3) In the apparatus for treating a plutonium-containing waste liquid using tannin according to the above (1) or (2), the closed waste liquid treatment chamber is a glove box.

By performing the waste liquid treatment in the glove box, since the operation is performed through the glove, exposure can be prevented and the operation can be performed with a simple operation. In addition, the insoluble tannin used as an adsorbent in the present invention has a high Pu adsorption ability as described above, so that the adsorption tower itself can be miniaturized. Therefore, the adsorption tower can be easily housed in a glove box having a width smaller than twice the hand length, and the waste liquid treatment apparatus can be made compact.

(4) In the apparatus for treating a wastewater containing plutonium using tannin according to the above (1) or (2), the adsorbent used for treating the wastewater having a low radioactivity level further comprises a wastewater having a high radioactivity level. The adsorption tower to be treated is refilled.

[0017] Accordingly, incineration is performed sequentially after the adsorption capacity of Pu or the like is reduced, so that the amount of insoluble tannin used can be reduced, and the amount of insoluble tannin used for incineration and residue treatment can be reduced. Can be minimized. For this reason, the exposure during treatment and the cost are improved as compared with the conventional case.

(5) In the apparatus for treating a plutonium-containing waste liquid using tannin according to any one of (1) to (3), the insoluble tannin is sealed in a cartridge made of a flammable material, and the tannin is charged into the adsorption tower. The cartridges are filled in multiple layers.

When replacing the adsorbent in the waste liquid treatment process, Pu
Can be minimized, and the waste liquid can be incinerated with the cartridge after use. Therefore, exposure during filling and disposal in the adsorption tower can be minimized.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described.

Referring to FIG. 1, an apparatus for treating plutonium-containing waste liquid using tannin according to this embodiment will be described. Note that the same components as those of the conventional apparatus for treating a plutonium-containing waste liquid are denoted by the same reference numerals, and description thereof will be omitted.

In the waste liquid treatment apparatus of the present embodiment, two glove boxes 10, 12 which are closed waste liquid treatment chambers are connected in series. The glove box 10 is a primary treatment chamber for adsorbing Pu in the high-activity level waste liquid, and the glove box 12 is configured to store the Pu in the waste liquid reduced to a low activity level in the glove box 10.
This is a secondary processing chamber for adsorbing water. The glove box 10 contains a high-activity level waste liquid (for example, α-ray emission concentration: 10
^A waste liquid receiving tank 20 for receiving ⁵ to 10 ⁶ Bq / ml) is provided, and the high-activity-level waste liquid from the waste liquid receiving tank 20 is supplied to an adsorption tower 30 filled with insoluble tannin. In the present embodiment, three adsorption towers 30 are arranged in series. The waste liquid that has passed through the adsorption towers 30a, 30b, and 30c is supplied to a monitor tank 40a, in which the radioactivity level is measured, and is supplied into the glove box 12 that is a low radioactivity level processing chamber in the next process. A check is made as to whether or not it is acceptable. This prevents the glove box 12 from being supplied with a high-level radioactive liquid waste and the glove box 12 from being radioactively contaminated (so-called cross-contamination) so that the radioactive level of the final waste liquid cannot reach the target value. That's why. In the monitor tank 40a, when it is confirmed that the waste liquid is a predetermined low radioactivity level waste liquid (for example, α-ray radiation concentration: 5.6 Bq / ml), the low radioactivity level waste liquid is filled with the insoluble tannin in the glove box 12. The adsorbed tower 50 is supplied. In the two adsorption towers 50a and 50b, Pu in the waste liquid is further adsorbed, and the final waste liquid is supplied to the monitor tank 40b. In the monitor tank 40b, the radioactivity level in the waste liquid is measured, and the effluent standard (for example, α-ray radiation concentration: 5.6 × 10 ^-2)
(Bq / ml) is discharged.

If the effluent standard is not satisfied, a tertiary treatment chamber is further provided. In this tertiary treatment chamber, Pu in the waste liquid is adsorbed by passing through an adsorption tower filled with insoluble tannin, and the waste liquid is treated. It is discharged after reducing the amount of radioactivity in it.

In the present embodiment, the waste liquid treatment is performed by dividing the radioactivity level into two stages. However, the present invention is not limited to this.
Depending on the radiation concentration of the waste liquid, the amount of the waste liquid to be treated, etc., the radioactivity level may be divided into a plurality of stages, and a plurality of glove boxes, which are closed type waste liquid treatment chambers, may be arranged in series to perform the waste liquid treatment.

According to this embodiment, the coagulation settling tank and the activated carbon adsorption tower of the conventional equipment as shown in FIG. 3 are not used in combination. Therefore, there is no need to perform the withdrawal, dehydration, washing, roasting, further canning treatment and storage work of the coagulated sediment slurry from the coagulated sedimentation tank, and the operation can be greatly simplified, and the operation is simplified. Become. Further, since a reagent adding operation or the like is not required, the processing operation is further simplified. Further, the insoluble tannin used as the adsorbent in the present embodiment has a structure as shown in the following chemical formula 1, so that it can be decomposed into carbon dioxide and water vapor by thermal decomposition (incineration), and only a very small amount of adsorbed substances such as plutonium can be decomposed. Is recovered as an oxide. For this reason, secondary waste can be reduced.

[0026]

Embedded image When the insoluble tannin used in the present embodiment is processed into a metal element adsorbent, for example, a production method described in JP-A-5-66291 may be used. That is, a condensation type tannin powder is dissolved in aqueous ammonia, and an aldehyde aqueous solution is mixed with the solution to form a gel composition, and the gel composition is aged at room temperature or stabilized by heating to form a gel. Adsorbents in the form of a solid may be produced.

The insoluble tannin used in this embodiment is Pu
Is presumed to be as shown in Chemical formula 2.

[0028]

Embedded image Further, in this embodiment, the adsorbent for treating the low-activity level waste liquid filled in the adsorption tower 50 is refilled in the adsorption tower 30 for further processing the high-activity level waste liquid. Therefore, Pu
Since the adsorbent whose adsorption capacity has been reduced is incinerated sequentially, the amount of insoluble tannin used can be reduced. For this reason, the incineration of used insoluble tannin and the amount of residue treatment are minimized, and the exposure and cost during treatment are improved as compared with the conventional case.

In this embodiment, the insoluble tannin is sealed in a cartridge made of a flammable material, and the adsorption towers 30 and 50 are filled.
The cartridge is filled in multiple layers. Therefore,
By filling the cartridge with insoluble tannin,
It is possible to minimize the scattering of Pu when the adsorbent is replaced in the waste liquid treatment step. Further, by using a cartridge made of a flammable material, the entire cartridge can be incinerated after use. Therefore, exposure during filling and disposal in the adsorption tower can be minimized.

[0030]

Next, the present invention will be described specifically with reference to examples. The waste liquid treatment apparatus used in the example has the configuration shown in FIG. 1, and the operation is the same as described above.

Embodiment 1 (1) Target value of waste liquid treatment α-ray emission concentration after primary treatment: 5.6 Bq / ml or less α-ray emission concentration after secondary treatment: 5.6 × 10 ^-2 Bq / ml
The following (2) Processing conditions The amount of insoluble tannin used; In the glove box 10 for primary treatment: 50 liters x 2
Group (adsorption towers 30b, 30c) + 10 liters x 1 group (adsorption tower 30a) In glove box 12 for secondary treatment: 50 liters x 2
Group (adsorption towers 50a, 50b) α-ray emission concentration in waste liquid before treatment: 2.7 × 10 ⁵ Bq /
ml pH: adjusted to 6.8 using aqueous ammonia Flow rate: about 7 liters / hr. Waste liquid treatment volume: 200 liters (3) Treatment results (average of multiple experiments is shown below) α-ray emission concentration of primary treatment solution: 5.0 × 10 ^-1 Bq / ml after secondary treatment α-ray radiation concentration: 2.0 × 10 ⁻² Bq / ml From the above, the waste liquid with a high radioactivity concentration could be reduced to the target radiation concentration by using the adsorption tower of insoluble tannin alone.

Embodiment 2 FIG. (1) Treatment conditions in the glove box 12 for secondary treatment (low radioactivity level) and adsorption amount until replacement of the adsorbent; Insoluble tannin used amount: 50 liter Waste liquid treatment amount: 1,500 liter α ray of the processing solution Average emission concentration: 5 Bq / ml Average α-ray emission concentration of the treated liquid: 2.0 × 10 ⁻² Bq / ml
The radioactivity adsorbed in ml is as shown in the following formula 1.

[0033]

## EQU1 ## 5Bq / ml × (1,500 × 1,000) −
2.0 × 10 ^-2 Bq / ml × (1,500 × 1,000
0) = 7.47 × 10 ⁶ Bq The amount of Pu per liter of the adsorbent is calculated assuming that the specific activity per 1 g of Pu is 1.0 × 10 ¹⁰ Bq, as shown in the following Equation 2.

[0034]

## EQU2 ## (7.47 × 10 ⁶ Bq) / (1.0 × 10 ¹⁰
(Bq / g) /50=1.5×10 ⁻⁵ g (2) Treatment conditions in the glove box 12 in the secondary treatment (low radioactivity level) and the amount of adsorption until the adsorbent is replaced; the amount of insoluble tannin used: 39.2 ml Waste liquid treatment amount: 800 ml Average of α-ray emission concentration of treatment liquid: 1.2 × 10 ⁴ Bq /
ml Average of α-ray emission concentration of treated liquid: 5 Bq / ml (α-ray emission concentration of treated liquid after 800 ml treatment: 5.6
(Bq / ml) The adsorbed radioactivity is as shown in Formula 3 below.

[0035]

## EQU3 ## (1.2 × 10 ⁴ Bq / ml × 800) − (5
(Bq / ml × 800) = 9.596 × 10 ⁶ Bq The amount of Pu per liter of adsorbent is calculated assuming that the specific activity per 1 g of Pu is 1.0 × 10 ¹⁰ Bq, as shown in the following Equation 4.

[0036]

## EQU4 ## (9.596 × 10 ⁶ Bq) / (1.0 × 10
¹⁰ Bq / g) /39.2×10 ³ = 2.45 × 10 ⁻² g The above calculation result shows that the insoluble tannin used in the low-level processing step can be reused in the high-level processing step. did.

[0037]

As described above, according to the apparatus for treating a plutonium-containing waste liquid using tannin according to the present invention, insoluble tannin adsorbs uranium and transuranium elements extremely efficiently. Therefore, if the waste liquid containing Pu is passed through at least two or more towers through the adsorption tower filled with the insoluble tannin, Pu in the waste liquid is adsorbed on the insoluble tannin,
Effluent standards can be met by a single treatment process without any combination with other methods. Therefore, it is possible to provide a waste liquid treatment apparatus that is simple and easy to operate. As described above, tannin has a high ability to adsorb Pu, so that the size of the adsorption tower can be reduced. As a result, the entire waste liquid treatment apparatus can be significantly reduced in size as compared with the related art. Furthermore, since insoluble tannin is composed of carbon, hydrogen and oxygen, if the used adsorbent that has lost the ability to adsorb Pu is incinerated, the insoluble tannin becomes gas such as carbon dioxide gas and water vapor, thus polluting the outside world. Can be released without On the other hand, trace amounts of U and Pu adsorbed on the insoluble tannin are oxidized to uranium oxide and plutonium oxide. These oxides can be, for example, MOX powder, and the residue after waste liquid treatment can be reduced as much as possible.

[Brief description of the drawings]

FIG. 1 is a view showing a configuration of a treatment device for a plutonium-containing waste liquid using tannin according to the present invention.

FIG. 2 is a flow chart until a MOX fuel body is manufactured from spent nuclear fuel.

FIG. 3 is a diagram showing a configuration of a conventional apparatus for treating a plutonium-containing waste liquid.

[Explanation of symbols]

10, 12 glove box, 20 waste liquid receiving tank, 3
0, 30a, 30b, 30c, 50, 50a, 50b
Adsorption tower, 40a, 40b Monitor tank.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Shoichi Kubo, Inventor 622-1 Funashikawa, Tokai-mura, Naka-gun, Ibaraki Pref. 622-1 Mitsubishi Nuclear Fuel Co., Ltd. Tokai Works

Claims (5)

[Claims] 1. An apparatus for treating a plutonium-containing waste liquid using tannin, wherein at least two adsorption towers filled with an adsorbent made of insoluble tannin are connected in series. 2. The apparatus for treating a plutonium-containing waste liquid using tannin according to claim 1, further comprising: at least two or more adsorption towers each having at least two or more closed-type waste liquid treatment chambers having different radioactivity treatment levels. The plutonium-containing waste liquid treating apparatus using tannin, wherein the at least two or more closed type waste liquid treatment chambers are connected and arranged in series with each other. 3. The apparatus for treating a plutonium-containing waste liquid using tannin according to claim 1 or 2, wherein the closed waste liquid treatment chamber is a glove box, wherein the plutonium-containing waste liquid using tannin is used. Waste liquid treatment equipment. 4. The apparatus for treating a plutonium-containing waste liquid using tannin according to claim 1 or 2, wherein the adsorbent used for the treatment of the low-activity level waste liquid further treats the high-activity level waste liquid. An apparatus for treating plutonium-containing waste liquid using tannin, which is refilled in an adsorption tower. 5. The apparatus for treating a plutonium-containing waste liquid using tannin according to any one of claims 1 to 3, wherein the insoluble tannin is sealed in a cartridge made of a combustible material, and the cartridge is placed in the adsorption tower. An apparatus for treating plutonium-containing waste liquid using tannin, characterized by being filled in multiple stages.