JPS5948697A - Method of processing radioactive organic waste - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for treating radioactive organic solid waste by wet oxidative decomposition using hydrogen peroxide.

Wastewater containing radionuclides generated at nuclear power plants and nuclear research facilities is filtered and treated with ion exchange resins, and the treatment of the resulting radioactive filter sludge and used ion exchange resins becomes a problem.

Volume reduction treatment methods for this type of radioactive organic solid waste include dry methods such as incineration and thermal decomposition, and wet methods such as acid decomposition and Zinpro methods, but each method has its own problems and has not been put into practical use. has not yet been reached.

Since the incineration method generates a large amount of corrosive waste gas, the treatment system becomes large-scale, and there are still problems to be solved when applying it to the treatment of radioactive waste. The pyrolysis method has the advantage that waste gas treatment is easy because there is little scattering of radionuclides to the cracked gas side. The process becomes more complicated.

The acid decomposition method using concentrated sulfuric acid has the following characteristics as a wet oxidation method:
While it has the advantage that most of the radioactive material remains in the liquid and there is no problem with waste gas treatment, it has the disadvantage that the equipment is severely corroded and expensive materials such as tantalum are required. The Zinpro method has similar advantages, but in order to ensure safety while employing high temperature and high pressure operating conditions, a great deal of consideration must be taken from the equipment standpoint alone.

One of the present inventors, together with other joint researchers, has developed an oxidative decomposition process that takes advantage of the wet method in that it is easy to process waste gas, avoids restrictions on equipment materials, and has no risk of explosion. With the intention of providing a new method, we have conducted repeated research focusing on the use of hydrogen peroxide, established an effective treatment technology, and have already proposed it (Japanese Patent Application No. 171,880/1980).
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The method comprises: -4- treating radioactive organic solid waste containing one, two or three of anion exchange resin, chelate resin and organic filter sludge with iron ion and/or cation exchange in an aqueous medium; It consists of oxidative decomposition by allowing hydrogen peroxide to act in the presence of a resin. Attempts have already been made to use aqueous hydrogen peroxide to treat used cation exchange resins, taking advantage of the fact that ferric ions [e3+] act as catalysts and promote oxidative decomposition reactions. Suggestions have been made (
(Japanese Patent Publication No. 1446/1983).

The significance of the method proposed earlier is that iron ions (Fe or F
In the presence of hydrogen peroxide, organic wastes other than ion exchange resins, such as chelate resins and organic wastes, such as cellulose filter sludge, can be suitably oxidized and decomposed30. With hydrogen peroxide, the oxidative decomposition of anion exchange resin, which was thought to be difficult even in the presence of F13 ions, progresses easily with the coexistence of a small amount of cation exchange resin, and the oxidation of organic substances contained in cation exchange resin The present invention was based on the discovery that the effect of promoting the decomposition reaction also extends to the above-mentioned chelate type resin and organic filter sludge.

-5- As a result of further research, it was discovered that the above oxidative decomposition could be carried out industrially more advantageously by continuously supplying hydrogen peroxide or a decomposition product such as hydrogen peroxide to the reaction system. The present invention was achieved by determining the conditions.

The method of treating radioactive organic waste of the present invention proposed this time is to treat radioactive organic solid waste containing one, two, or three of anion exchange resin, chelate resin, and organic filter sludge in an aqueous medium. In a method for treating radioactive organic waste, which consists of oxidative decomposition by acting hydrogen peroxide in the presence of iron ions and/or cation exchange resin, hydrogen peroxide solution with a concentration of 30 to 60% heavy clouding is used. It is characterized in that it is continuously supplied in a liquid state or in a gaseous state at a rate of 2 to 40 (+)/hour per 1 (+ (dry basis)) of the decomposition material.

As mentioned above, the hydrogen peroxide solution may be added in a liquid state or in a gaseous state. H
If the concentration of water is low, there will be heat loss due to water evaporation and excess water will be generated, which will be disadvantageous, and if the temperature rises, it will become dangerous. As a compromise, a concentration in the range of 30 to 60% by weight should be used.

If the supply rate of the hydrogen peroxide solution is too low, the time required for the reaction becomes long, which is impractical. As a lower limit, about 29/hour is required for the dry weight of the decomposition material of 19.
On the other hand, if the temperature is increased too much, it will not contribute to the reaction and the rate of decomposition will increase, so it is best to stop the temperature at 400/hour.

In an embodiment in which organic waste, which is a decomposition product, is continuously supplied together with the hydrogen peroxide solution, the hydrogen peroxide solution supply rate is maintained at 1 to 20 q/hour per decomposition product 1 (1/hour). Continuously supply decomposition products. In this case,
It is preferable to select the concentration of the decomposition product in the reaction system in the range of 1 to 10% by weight. Moreover, the average residence time is about 2 to 6 hours.

In any of the above embodiments, it is recommended that the treatment = 7- be carried out while promoting stirring of the reaction system by supplying the hydrogen peroxide solution from below the apparatus for carrying out the oxidative decomposition reaction.

Other points are unchanged from those mentioned in Sagi's proposal. That is, the first representative embodiment of the treatment method of the present invention is a case where the radioactive organic solid waste to be treated contains an anion exchange resin or the same, and the radioactive organic solid waste is treated in the presence of iron ions and a cation exchange resin. The second method is when the object to be treated is a chelate type resin, organic filter sludge, or a mixture thereof, and peroxide is applied in the presence of iron ions, cation exchange resin, or both. It uses hydrogen.

The iron ions may be in the form of ferrous ions Fe, 3+ or ferric ions Fe. If the temperature is 0.01 mol/Q or more in an aqueous medium, it is effective, and if it is 0.05 mol/Q or more, it is unnecessary and the effect will be reduced.

It is already known that in this range there is almost no dependence on concentration.

As a source of iron ions, any soluble salts can be used. For example, FeSO4, (NH,)2Fe (S
04)2, FeC1z 1[e (CI5-CHOH
COO), , Fe C,o, etc. are ant, and those that give 3,000 Fe are Fez (so, >,
, Fe (NO3)3 , Fe C13, <NH4
)zFe, (80,), etc. However, from the viewpoint of equipment corrosion, those containing CI are not preferable, and ammonium salts may also cause gas generation problems. Organic salts also seem to have low activity according to experiments conducted by the present inventors, so in the end, Feso4, Fez
(SO4)3, l”e <No3)3, etc. are appropriate.

On the other hand, the influence of cation exchange resins on other organic wastes such as anion exchange resins is recognized if they are present in an amount of 1% or more by weight. A significant effect is obtained at 10% or more. In fact, wastewater treatment at nuclear facilities generates used cation exchange resins and anion exchange resins as organic waste at the same time.
All we have to do is to process all of them together.

It has been revealed that 111-1 in the reaction system has almost no effect on the reaction rate as long as it is within the range of 1 to 10. However, in reality, in order to avoid corrosion of the equipment, I)f-
11; Should be 5 or higher. If the product to be decomposed is a cation exchange resin, care must be taken since the decomposition produces -SO, which lowers the EIH.

Oxidative decomposition proceeds rapidly when carried out at a temperature of about 70°C or higher. Since it is an exothermic reaction, once it has proceeded, no further heating is required, or only very little if any. If no pressure is applied, the reaction continues near the boiling point of the aqueous medium, that is, around 100°C. Of course, it is possible to employ higher concentrations under pressure, but one of the advantages of the present invention is that it can be carried out at normal pressure, and pressurization is not advisable.

The catalytic effect of iron ions on the oxidative decomposition reaction mentioned above is
The present inventors' research has also revealed that the coexistence of a small amount of cobalt ions (for example, Co) or manganese ions (for example, Mn) can further promote this effect. Therefore, implementation in the presence of these ions also falls within the scope of the invention. C
As a salt that provides O and Mn ions, Co (C
H3Coo)z, Co Soi, 1yln (c
H3Coo)z, Mnso4, etc.

These ions, like iron ions, range from 0.01 to 0.0
It is appropriate to use it in a concentration range of about 5 mol/day.

When organic waste is oxidatively decomposed using hydrogen peroxide, the products are mainly carbon dioxide gas and water, which are completely harmless. In other words, the advantage of the wet method in that there is no problem with waste gas treatment is maximized, as has been achieved in the previously disclosed technology. In addition, the following effects can be obtained by continuous supply.

The biggest one is that hydrogen peroxide can be used effectively; the amount of hydrogen peroxide required for oxidative decomposition of the same amount of radioactive organic waste is much greater than when feeding in batches. Less is needed.

This will be clear from the examples described later.

-'11- Next, when the substance to be decomposed is a cation exchange resin, the decomposition reaction proceeds rapidly and is difficult to control, but it is easy to control using a continuous method.

From an equipment point of view, when supplying in batches, it is necessary to add a large amount of hydrogen peroxide solution at once.
Although the reactor volume becomes large, a small reactor is sufficient for continuous operation. This advantage is particularly noticeable when the decomposition products are also continuously supplied. In addition, in a preferred embodiment in which the hydrogen peroxide solution is supplied from the bottom of the reaction apparatus, bubbles of oxygen and other gas generated by the decomposition of the supplied hydrogen peroxide rise and have the effect of stirring the reaction system. , there is no need to install a stirrer inside the reactor, outside the reactor, or provide an external circulation pump for stirring. This is an important advantage in handling radioactive materials.

l”e S 04 ・7 H2,O or Fe(NO
3) Add 1 g each of powder of various -12- ion exchange resins or filter sludge to an aqueous solution containing 3.9 H, O at 50°C.
was suspended, heated to 80° C., and 35% hydrogen peroxide solution was added batchwise or continuously, with stirring in the former case and without stirring in the latter case.

Table 1 compares the amount of 35% hydrogen peroxide required for complete dissolution of the resin between batch supply (all at once) and continuous supply (feed rate is 23.7 g/hour). Shown below.
It is clear that the continuous method requires less hydrogen peroxide consumption than the batch method.

-13- No. 1 Table 35% hydrogen peroxide water amount Fat (-) L square cation exchange resin Powdex PCH820 7 Nhalite r R-120B 7 15
Diaion 5KII-11530 Amberlite 200C1530 (Anion exchange resin) Boudex PA0 18 〉100 Amberlite IRA-40027>100 Diaion 5AN-
115>100 Amberlite IRA-90017>100 (chelate resin) UNISEREC UR-5030>100 (filter sludge) KC Flock 25 >100 TSUKA FLOCK 42 >100- 14
- Add granular ion exchange resin (Diaion 5
A Fe catalyst was added to a slurry containing 2 g of K1B 29 and 2 g of 5A10A at a temperature of 0.
Added so that it becomes OIM.

A basic reactor is prepared, and the above slurry is fed at 35 m1/hour.
A 35% hydrogen peroxide solution was continuously supplied at a rate of 14 ml/hour, and oxidative decomposition was carried out under conditions of a humidity of 100° C. and an average i residence time of 5 hours. A reaction rate of 98% was obtained.

1i Breast cation exchange resin IR-120B and anion exchange resin I
In a system in which 1 g of each RA-400 was suspended in 50 ml of water, the FeZt catalyst was brought to zero temperature and 2M, and the initial pH was adjusted to
Adjust to various values and add 60ml of 35% hydrogen peroxide solution.
It was fed continuously at a rate of l/h.

The results of examining the conversion rate over time for each pto1 are shown in Table 2.
It can be seen that -1 has almost no effect.

-15- Second table conversion rate (%) 1 bean 11H-□ 471 car 50 84 94, 9489 60 87 96 9694 90 91 99 9997 120 93 99 9998 150 9510010099 Tue L [(Cation exchange resin IR-120 B's A suspension of 10g in 10 times the amount of water was treated with 35% hydrogen peroxide to cause oxidation and decomposition.The volume of the reactor was set to ensure safety against foaming that occurs rapidly during the reaction. In contrast, 400 to 600 ml was required in the batch-type hydrogen peroxide solution supply, whereas 200 ml was sufficient in the continuous method.

Discount 19 [Organic filter sludge KO flock 20! + water 5
Disperse in 0ml and add 35% hydrogen peroxide solution to -1
Brewing and decomposition were carried out by continuously feeding at a rate of 6 to 160 ml/hour. When comparing the TOC reduction rate after 2 hours and 30 minutes with and without mechanical stirring, the former had a value of 98% and the latter had a value of 93%.

Patent applicant: JGC Corporation Agent: Patent Attorney: Souo Suga -17- Continuation of page 1 0 shots Akihiro Yamanaka 2-16-60 Wakabadai, Asahi-ku, Yokohama [Phase] Founder: Hiroshi Kuribayashi Yamato type Tsukimino 7-18-11

Claims (1)

[Scope of Claims] (1) Radioactive organic solid waste containing one, two, or three of anion exchange resin, chelate resin, and organic filter sludge is treated in an aqueous medium with iron ions and/or In a method for treating radioactive organic waste, which involves oxidative decomposition of hydrogen peroxide in the presence of a cationic father-converting resin, aqueous hydrogen peroxide with a concentration of 30 to 60% by weight is used in a liquid state or as a gas. A method characterized by continuously supplying the hydrogen peroxide solution at a rate of 2 to 40 F/hour per 1 g of decomposed material (dry basis). (2) Adjust the supply rate of hydrogen peroxide solution per 1 g of decomposed material The method according to claim 1, wherein the decomposition product is continuously supplied and treated while maintaining the concentration of the decomposition product at 1 to 20 g/hour. The method according to claim 2, wherein the organic solid waste is an anion exchange resin, and the organic solid waste is an anion exchange resin.
The method according to claim 1 or 2, wherein the oxidative decomposition is carried out in the presence of iron ions and a cation exchange resin. (5) The method according to claim 1 or 2, wherein the organic solid waste is a chelate type resin or an organic filter sludge, and the oxidative decomposition is performed in the presence of iron ions, a cation exchange resin, or both. (6) The method according to claim 1 or 2, wherein the oxidative decomposition is carried out in the pH range of 1.5 to 1o in the aqueous medium. (7) The method according to claim 1 or 2, wherein oxidative decomposition is carried out while agitation of the reaction system is promoted by supplying hydrogen peroxide solution from below the reaction apparatus. -2-