JPS6159299A - Method and device for treating radioactive 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] [Field of Application of the Invention] The present invention mainly relates to a method for disposing of radioactive waste consisting of spent ion exchange resin, and in particular to the use of adsorbed radioactive waste materials generated from nuclear power plants, etc. This invention relates to a method for treating ψ ion exchange resin and an apparatus therefor.

[Background of the invention]

Miscellaneous article in the journal of the Atomic Energy Society of Japan, “Bulk Volume Reduction Processing of Nuclear Power Plants J (Tol, 24. A10. pp770-774 (1)
According to 982)), it is described as follows (however, some additions are made regarding operating conditions, etc.).

``Radioactive waste generated from nuclear power plants is canned in drums and stored in storage within the power plant, but as the years of operation increase, storage space increases, and as a countermeasure, it is desirable to significantly reduce the volume of waste.

In response to these needs, several volume reduction and solidification processing devices are being developed, and three representative examples will be introduced below.

(1) Fluidized bed furnace (a method in which concentrated waste liquid, flammable miscellaneous solids, used ion exchange resin, waste oil, etc. are incinerated or calcined using an operating temperature of 900C. A binder is added to the recovered incineration ash and calcined products. Afterwards, it is made into pellets using a tablet press and stored.

(2) After drying and powdering concentrated waste liquid, used ion exchange resin, filter sludge, etc. using the steam temperature of the mouth heat source of the centrifugal thin film dryer (160c), the mixture is uniformly mixed with thermosetting resin and placed in a drum. Fill and solidify.

(3) After drying and powdering in the same manner as in (2), pelletize using a granulator and store. Furthermore, for final disposal, it is also possible to fill a drum with pellets and inject a solidifying material to solidify the pellets.

In both of the above methods, a wide variety of wastes are treated all at once using a single device, thereby making the device more compact and improving operational reliability. ” All of the volume reduction and solidification processing equipment mentioned above have a sufficient track record from a technical and safety point of view, and there are no problems in that respect, but their characteristics regarding the processing of used ion exchange resin Therefore, there are problems in that the capacity of the equipment must be increased or special equipment is required. Problems regarding the above-mentioned processing devices will be described below. Regarding (1), due to the characteristic that used ion exchange resin is covered with plastic, the calorific value is 10
4 days/9, which is about three times as large as combustible miscellaneous solids, and from this point of view, treatments are taken to prevent temperature runaway in the fluidized bed furnace. For example, a device is provided for mixing in radioactive waste with low calorific value such as combustible miscellaneous solids.

Regarding (2), a thermosetting resin is used as a solidifying agent, but if even a small amount of water is mixed into the thermosetting resin, the desired performance as a solidifying agent cannot be exhibited.

In other words, if moisture is introduced during solidification, the curing accelerator (cobalt heptanoate, etc.) in the thermosetting resin will be decomposed and the thermosetting resin will harden and become dangerous. This is because it remains in the state (liquid) at the time of addition.

Even if used ion exchange resin is carefully dried,
In some cases, it may not be possible to completely remove moisture.

Therefore, if a used ion exchange resin and a thermosetting resin containing even a small amount of water are mixed and solidified, a solidified product with high strength cannot be obtained.

For this reason, the powder dried in a centrifugal thin film dryer is measured with a moisture content measuring device such as a neutron moisture meter to ensure thorough moisture content control. Furthermore, regarding (3), since the dry powder of used ion exchange resin adsorbs water and changes its volume, the pellets are damaged by moisture during storage of the pellets. To prevent this, the humidity of the air in the storage tank for storing pellets is controlled. In addition, dry powder of used ion exchange resin or its pellets,
When solidifying with a hydraulic solidifying agent such as cement or a solidifying agent using an alkaline silicate solution, a large amount of water is involved in the reaction during solidification, so the dry powder or pellets of the used ion exchange resin are absorbs and causes an increase in volume. For this reason, 20
Comparing the amount of filling into a 0L drum, hydraulic solidifying agent,
For alkali silicate solidifying agents, method 110 of the above-mentioned method is used.
Only 1/2 to 1/3 of a 200 ton dry resin drum can be filled.

As mentioned above, there are several ways to dispose of used ion exchange resin.
Various drawbacks arise from the nature of ion exchange resins.

[Purpose of the invention]

The purpose of the present invention is to solidify radioactive waste mainly consisting of used ion exchange resins by a simple method with a significant volume reduction, and to obtain a solidified material with high axial compressive strength. The purpose of the present invention is to provide a method and device for processing things.

[Summary of the invention]

The first feature of the present invention is that in a method for treating radioactive waste mainly consisting of used ion exchange resin, first, by heating the radioactive waste, the ion exchange groups of the used ion exchange resin are heated. Decomposes and carbonizes. As a result, the radioactive waste has hydrophobicity and gas adsorption properties.

Next, the gas adsorbed on the radioactive waste, which is an obstacle to obtaining a high volume reduction ratio and high axial compressive strength of the solidified body finally formed, is degassed.

Finally, the degassed radioactive waste is mixed with a solidifying agent to form a solidified body with a large volume reduction ratio and high -axial compressive strength.

A second feature of the present invention is that in a radioactive waste processing apparatus mainly made of used ion exchange resin, in order to achieve the method, a pyrolysis device that heats and carbonizes the radioactive waste; It has a degassing means for degassing the gas adsorbed on the carbonized radioactive waste, a solidifying means for solidifying the degassed radioactive waste, and the like.

[Embodiments of the invention]

The basic principle of the present invention will be explained. The inventors found that the ion exchange group of the ion exchange resin was 120C to 350tl:'.

It has been found that thermal decomposition can be carried out preferably at about 200 C to 300 C. Furthermore, we have discovered that the styrene/divinylbenzene copolymer, which is the polymer base of the ion exchange resin, is carbonized during this thermal decomposition. In addition, with the carbonization of the polymer base of the ion exchange resin due to thermal decomposition, the expansion and contraction that appeared due to water absorption and drying of the ion exchange resin before carbonization are no longer observed. It was discovered that gas adsorption phenomena such as Possible causes of this phenomenon are as follows. That is, the elastic network-like molecular structure changes to a dense molecular structure typified by graphite, and at the same time, the ion exchange group with water absorbing properties disappears, so there is no expansion or contraction. At the same time, there is no hydrophilic ion exchange group and the carbon becomes hydrophobic, making it easier to adsorb gases such as air.This will be explained below using a specific example.

Sulfonic acid group (S Os H) which is an ion exchange group
It has a cross-linked structure in which , and has a three-dimensional structure, and has the following structural formula. Also, the molecular formula is (Ct
eHtsOsS)n Hail Sarel.

CH-CH2-CH 03H On the other hand, anion exchange resin has a quaternary ammonium group (N
It has the following structural formula. Further, the molecular formula is (Czo&aON)n.

Next, the bond energy of the bond between each component of the ion exchange resin will be explained. FIG. 2 shows the skeletal structure of a cation exchange resin, which is basically the same in the case of an anion exchange resin, with the only difference being the orientation and ion exchange groups. In FIG. 2, each connecting portion 1, 2, 3, . . . between each component is shown.
The binding energies of 4 are shown in Table 1.

Table 1 When an ion exchange resin is thermally decomposed, the ion exchange group with the lowest binding energy decomposes first, then the linear chain portion of the polymer base, and finally the benzene ring portion.

Specifically, FIG. 3 shows the results of thermogravimetric analysis (TGA) of the ion exchange resin in an air atmosphere using a differential thermal balance. However, the weight loss associated with water evaporation that occurs between 70C and 110C is not shown.

The solid line shows the thermoelectric fit change of the anion exchange resin, and the dashed line shows that of the cation exchange resin. Table 2 also shows the decomposition temperatures of each bond shown in Figure 3.

According to Table 2, in the anion exchange resin, the quaternary ammonium group, which is an ion exchange group, decomposes first at 130 to 190C, the linear part decomposes at 350C or more, and the benzene ring part decomposes at 380C or more. In addition, for cation exchange resins, 200
After the sulfonic acid group, which is an ion exchange group, is decomposed at ~300C, the linear portion and benzene ring portion are decomposed in the same manner as the anion resin.

However, this decomposition characteristic changes depending on the presence or absence of oxygen. Figures 4 and 5 show the data obtained when thermogravimetric analysis was conducted in an air atmosphere containing the chemical equivalent of oxygen required to thermally decompose used resin, and in a nitrogen atmosphere containing no oxygen, respectively. (The thermogravimetric analysis shown in FIG. 3 above is data obtained when sufficiently more oxygen than the chemical equivalent was supplied).

FIG. 4 shows data when a cation exchange resin is thermally decomposed, where the solid line shows the data in an atmosphere containing a chemical equivalent of oxygen, and the broken line shows the data in a nitrogen atmosphere. It can be seen that most of the polymer substrates undergo oxidation reactions that require oxygen and are accompanied by heat generation. On the other hand, even in a nitrogen atmosphere, the ion exchange group (sulfonic acid group) is 200 to aooot
The thermal decomposition of ion exchange groups does not require the supply of oxygen and does not generate heat.

FIG. 5 shows data obtained when an anion exchange resin is thermally decomposed. Similar to FIG. 4, the solid line shows data in a chemical equivalent amount of oxygen atmosphere, and the broken line shows data in a nitrogen atmosphere. In this way, in the case of anion exchange resins as well as in the case of cation exchange resins, the ion exchange groups (quaternary ammonium groups) decompose at 130 to 190 C even in the absence of oxygen, and the polymer base is exposed to oxygen.
) It was found that oxidative decomposition occurs at 350 to 480C while generating heat.

As a result of the above thermal decomposition, the ion exchange group in the ion exchange resin can be decomposed in an inert gas atmosphere such as nitrogen without generating heat, but even if it is heated as it is, the entire polymer base will decompose. It is not possible. Therefore, we investigated the physical properties of the ion exchange resin after decomposition of the ion exchange groups.

As for the physical properties, experiments were conducted on two points: water adsorption, which is a problem in the prior art, and the swelling that accompanies it.

Figure 6 shows the results of the immersion test. Here, the degree of swelling by water was measured using a dried granular ion exchange resin and a granular ion exchange resin thermally decomposed at 600C (hereinafter referred to as carbonized resin). In the case of dry ion exchange resins, the volume increases approximately three times upon immersion in water. On the other hand, it has been discovered that in carbonized resin, the volume once increases gradually, but then bubbles are released and the volume returns to its initial state.

As mentioned above, the phenomena that appear in dry ion exchange resins and carbonized resins are different. Figure 7 shows the phenomena that appear in each resin and their mechanisms. Swelling occurs when a dry ion exchange resin is immersed in water, and this phenomenon is generally considered as follows. The ion exchange groups of the ion exchange resin are present in the molecular structure of the styrene φ divinylbenzene copolymer network. This ion exchange group has strong polarizability, which is the main reason for the adsorption of highly polar water.

This adsorbed water spreads out the elastic network structure of the polymer substrate and penetrates into it. This causes swelling that increases the volume of the ion exchange resin.

Taking granular ion exchange resin as an example, the average particle size when dried was 400 μm, but now it is 450 to 600 μm, which is 1.2 to 3 times the volume ratio (the increase in volume is due to the increase in the ion exchange group). Although it varies depending on the ion, it is generally H4''
〉Alkali metals〉alkaline earth metals and transition metals). It is important to note here that there are two causes for the swelling of the ion exchange resin. One is that the highly polarizable ion exchange group absorbs water, and the other is that the polymer base has an elastic network structure. This is because even in resins with only polymeric bases that do not have ion exchange groups,
This is because the volume expands by about 1.2 times with water.

With carbonized resins, this situation completely changes. That is, due to carbonization, the particle size of the carbonized resin is smaller than the particle size of the dry resin, and the volume is 1/2 that of the dry resin. Along with this, the pore characteristics of about 7 to 7 people that the ion exchange resin had appear. The molecular structure is polycyclic, approaching that of graphite, and the hydrophobic nature of carbon appears, which eliminates the adsorption of water into the pores and makes it easier for gases such as air to adsorb. However, once adsorbed gas such as air is desorbed again and released as a gas in the presence of a large amount of water, ie, when immersed in water. This appears as a defoaming phenomenon, which gives the appearance that the carbonized resin has swollen. Furthermore, since the molecular structure is a dense polycyclic structure, even when water is adsorbed, the volume no longer increases as with conventional polymer substrates. This fact corresponds to the immersion time of 150 hours (approximately 6 days) in Figure 6.
This is also supported by the fact that there is no change in volume.

The above characteristics of the carbonized resin were newly discovered by the inventors. In other words, add 1 ion exchange resin in advance.
By thermally decomposing it in the range of 200 to 600000 or more, it has characteristics completely different from that of the ion exchange resin before thermal decomposition. Utilizing this characteristic, carbonized resin can be pelletized and stored to meet special requirements such as humidity control.
Intermediate storage of weak waste becomes easy without the need for equipment.

Furthermore, since carbonized resins or their pellets have hydrophobic properties as mentioned above, the solidified material formed when they are solidified with thermosetting glass, etc., which is exposed to the shadow of moisture, has high strength. becomes.

Therefore, advanced moisture management, such as conventional technology that mixes and solidifies non-carbonized ion exchange resin and thermosetting plastics? 1ilj constant becomes unnecessary.

However, when using a solidifying agent using a hydraulic substance or an alkali silicate, it is not possible to obtain a solidified body with high strength unless defoaming is performed, as will be described later in the explanation regarding FIG.

Therefore, the inventors discovered that a solidifying agent using a hydraulic substance or an alkali silicate, which does not have a hardening effect, is immersed in the liquid component of the solidifying agent to defoam it, and then hardened. I devised a method to solidify it. This idea is based on the characteristics of carbonized resin newly discovered by the inventors.

Hereinafter, the above solidification method will be described in detail using specific examples.

Here, an example will be described in which a carbonized resin obtained by carbonizing a granular ion exchange resin is homogeneously solidified using an alkaline silicate solution and a powder of silicon polyphosphate as a hardening agent.

First, a carbonized resin is immersed in an alkaline silicate solution and defoamed. After this, a curing agent was added and solidified. The relationship between the residual rate of adsorbed gas, the strength of the solidified body, and the filling jjt at this time is shown in FIG. The temperature at this time is 25C1, and the curing conditions are:
Carbonized resin 40wt%, silicate alkali solution 40wt*
, the proportion of curing agent is 20 wt%.

Further, the curing agent is not limited to silicon borate, and any weak acid may be used.

For example, inorganic phosphates such as sodium phosphate, or alkaline earth metal salts such as calcium silicate and barium carbonate are effective (for more details, see JP-A-57-197
500).

The adsorbed gas amount of the carbonized resin was 2.1 CC/g before defoaming.

The figure shows that the dynamic compressive strength gradually decreases as the residual rate of adsorbed gas increases. In addition, as the residual rate of adsorbed gas increases, the amount of carbonized resin filled per unit volume is
It continues to decline. This corresponds to the amount of bubbles generated by the gas desorbed from the carbonized resin. Furthermore, it is clear that the decrease in axial compressive strength is due to the air bubbles. - In order for the axial compressive strength to satisfy the ocean dumping standard of 150 Kti/cm, the residual rate of adsorbed gas must be 50% or less, and filling・F]: t-200t)"y A can conversion Te, 11
In order to fill 0 with 9 or more, the residual rate of adsorbed gas is 50
% or less. Even if 50% of the adsorbed gas remains, it does not affect the strength or filling amount because all of the adsorbed gas is not replaced with water and desorbed to generate bubbles. I believe that. Therefore, it can be seen that even if a part of the adsorbed gas is immersed in water etc., it is desorbed and no bubbles are produced. From the above, it is sufficient to desorb 50 g of the gas adsorbed on the carbonized resin, and the required immersion time of the carbonized resin in the alkaline silicate solution for this purpose was determined. FIG. 9 shows the results of the residual rate of adsorbed gas when immersed in an alkali silicate solution.

The experiment was conducted by selecting three immersion conditions: no stirring, with stirring, and stirring + heating. As a result, in either case, the amount of adsorbed gas decreases over time.

However, the decrease increases in the order of no stirring, stirring, and stirring + heating. As shown in FIG. 8, within 2 hours with stirring and stirring + heating, and within 3 hours with no stirring, the residual rate of adsorbed gas that satisfies the filling amount and strength is 50 cm or less, as shown in FIG. Also, ultra-old wave irradiation has the same effect as stirring.
C spring. The reason why the degree of decrease in adsorbed gas changes depending on the conditions during immersion can be explained as follows. That is, in the absence of stirring, the carbonized resin is destroyed by the desorbed gas, which inhibits water from being adsorbed by the carbonized resin, making it difficult for the gas to desorb. On the other hand, when stirring is added, the gas that covers the carbonized light resin is removed, so that the gas is desorbed more quickly. moreover,
When a heating operation is added to the stirring operation, gas desorption becomes faster, and this is thought to be because the rate at which water becomes water vapor and diffuses into the carbonized resin increases.

From the above results, 50 or more of the gases adsorbed by immersing carbonized 111 fat in an alkaline silicate solution are
By adding a curing agent to the solidified material and curing it, a solidified material with a high filling amount and high strength can be obtained. Furthermore, the gas desorption rate can be reduced by adding operations such as stirring and heating.

The above example is a case in which a granular ion exchange resin is carbonized, but when a powdered ion exchange resin is carbonized, defoaming can be similarly performed for pellets obtained by compressing and granulating the carbonized resin.

Figure 10 shows the results. In the same figure, the temperature is 25C
The particle size of one particle of ion exchange resin is about 30 μm. The pellets are cylindrical in shape and about 20 shoulders in height and diameter. For pellets, approximately 4 hours are required to achieve 50% residual adsorbed gas. Carbonized powdered ion-exchange resins can be defoamed in a shorter time than carbonized granular ion-exchange resins. For pellets, stirring alone may not be sufficient for degassing. Therefore, for pellets, by vacuum suctioning the gas adsorbed on the carbonized resin and then pouring in a mixture of an alkaline silicate solution and a curing agent, the residual rate of adsorbed gas becomes 20- or less, and the filling amount is large and the strength is increased. A high solidified product can be obtained.

As mentioned above, by pre-immersing the carbonized resin of powdered ion exchange resin and granular ion exchange resin in an alkaline silicate solution, the adsorbed gas is removed, and the filling amount of the carbonized resin is large and the strength is increased. A solidified product with high alkali silicate content can be obtained. Additionally, pellets can be more effectively degassed by vacuum degassing.
A solidified body of alkali silicate with a large filling amount and high strength can be obtained.

Although the above examples all use an alkali silicate solution, similar effects can be obtained using a hydraulic substance such as cement. A specific example of cement, which is a hydraulic solidifying agent, will be explained below. The cement used is usually Portland cement, which hardens when mixed with water.

In this case, since the cement is powdered, it is soaked in water in advance to remove the gas adsorbed on the carbonized resin. 1st
Figure 1 shows the change over time in the residual rate of adsorbed gas for the carbonized resin of the granular ion exchange resin.

Here, as in FIG. 9, experiments were conducted under three conditions: no stirring, with stirring, and stirring + heating. As a result, the time required for defoaming is shorter than in the case of alkaline silicate solution, and in both cases, the residual rate of adsorbed gas is reduced to 50% within 2 hours.
% or less. Cement is added to the carbonized resin which has been defoamed in this way, and is hardened and solidified. This L'') was first degassed by immersing 40 parts of the carbonized resin in 20 parts of water.
By adding cement 40 to this, cement 4
It is possible to create a solidified body containing 0wt% water, 2Qwt% water, and 40wt% carbonized resin. In this solidified body, the relationship between the residual rate of adsorbed gas in the carbonized resin, the unconfined compressive strength, and the filling amount is the same as that shown in FIG. Therefore, in cement as well, a solidified body with a high filling amount and high strength can be obtained.

In the above example, an example was described in which the carbonized resin of the granular ion exchange resin is solidified with cement, but the same effect can be achieved with the towing resin of the powdered ion exchange resin and the pelletized carbonized resin.

FIG. 12 shows the degree of defoaming of these carbonized resins and pellets. Note that the temperature in the figure is 25C. Carbonized powdered ion-exchange resins can be immersed and defoamed in a shorter time than granular ion-exchange resins. On the other hand, for pellets, it takes about 3 hours to reach a residual rate of 50% of adhering gas, but stirring alone may not be sufficient to degas the cement. For this reason, it is desirable to use a method in which the gas adsorbed on the carbonized resin is vacuum-suctioned, and then a mixture of cement and water is completely poured into the carbonized resin. As a result, the residual ratio of adsorbed gas in the carbonized resin is 20 or less, and a solidified body with a large filling amount and high strength can be obtained.

As mentioned above, by soaking powdered ion exchange resin and granular ion exchange resin in water in advance, adsorbed gas can be removed, and a solidified cement with a large amount of carbonized resin and high strength can be obtained. It will be done. In addition, the pellets can be more effectively degassed by vacuum degassing, and a solidified cement with a large filling amount and a strong If can be obtained.

In the above example, the hydraulic substance was chemical (1), but the solidifying agent consisting of alkali silicate powder and hardening agent powder is also a hydraulic substance that hardens by adding water. The same effect as in the above cement example can be obtained even if the cement is used.

Below, an effective device flow for carrying out the present invention is shown,
Examples of the present invention will be specifically described.

Example 1 In this example, a powdery ion exchange resin generated from a condensate purifier of a boiling water reactor is converted into a carbonized resin by thermal decomposition, and then this is treated with an alkali silicate as a solidifying agent. Fig. 1 shows a system diagram of the processing system used in this example.

Used powdered ion exchange resin (hereinafter abbreviated as powdered resin)
51 is discarded from the condensate demineralizer through a backwashing operation, so it becomes a slurry, which is stored in a waste resin tank 52. The powdered resin 51 in the waste resin tank 52 is approximately 1
The 0% slurry is supplied to the dehydrator 54 via the pulp 53, where it is centrifugally dehydrated to a water content of about 50%. Thereafter, a predetermined amount (approximately 200 dry weight) of the dehydrated powdered resin 51 is supplied to the pyrolysis apparatus via the knife gate valve 55. The pyrolysis equipment has an internal height of approximately 1m.”
It consists of a batch type fixed bed reactor 56 and a heating device 57. The powdered resin 51#'i supplied to the reactor 56 was heated at 300 C for about 4 hours by the heating device 57 to become a carbonized resin 58.

Incidentally, a cine active gas (for example, nitrogen gas) is supplied to the reactor 56 from an inert gas supply pipe 80 through the pulp 81t.

Thereby, the thermal decomposition of the ion exchange resin is carried out in an inert gas.

Therefore, even if the heating temperature of the ion exchange resin is raised to about -1600C, the ion exchange resin will not burn and generate heat and temperature will not run out of control, unlike in the case of heating in an oxygen atmosphere (see FIGS. 4 and 5).

Therefore, in the thermal decomposition operation of an ion exchange resin in an inert gas, there is no need for equipment to prevent heat generation due to combustion and temperature runaway.

During this time, HzS, SOx, NHs, etc., which are decomposition products of the ion exchange groups, become exhaust gas together with the moisture in the powdered resin, and this exhaust gas is led to the exhaust gas treatment device 60 via the pulp 59 and treated. On the other hand, carbonized resin 58 was supplied to drum can 62 via knife gate valve 61 . The weight of the carbonized resin 58 at this time is about 120 times 9 of the initial powder resin type t 200 Kp (dry weight).
It had decreased to After confirming that the temperature of the carbonized resin 58 filled in the drum can 62 was cooled to 100 C or less, 72 kg of water from the added water tank 63 was supplied to the drum can 62, and defoaming of the carbonized resin was started. At this time, stirring was performed using a stirring blade 64 to promote defoaming. Stirring continued for about 1 hour. After defoaming, a total of 108 kg of a powdered inorganic phosphoric acid compound was supplied through the solidifying agent hopper 65, a powdered alkali silicate hardening agent hopper 66, and the stirring blade In Step 64, the carbonized resin, water, solidifying agent, and hardening agent were uniformly mixed to form a solidified body.

Thereafter, this was left to cure, and the characteristics of the solidified material obtained after one month were investigated. The results are shown below. FIG. 13 shows a cross-sectional view of the obtained solidified body and an enlarged view thereof. As can be seen from FIG. 13, the solidifying agent 67 and the carbonized resin 58 are extremely homogeneously dispersed, and no air bubbles are observed in the solidified material due to the defoaming effect. In addition, the unconfined compressive strength of the obtained solidified product was 150 Kq/Crn" or more, confirming that it had sufficient strength. From the above results, in this example, 120 kg of carbonized resin and silica were combined in a 200 t drum. By uniformly mixing 9 with acid-alkaline solidifying agent (containing hardening agent and water) 180, there are no bubbles as shown in Fig. 13.
It was also found that a strong solidified body could be obtained.

Further, using the processing apparatus shown in FIG. 1, a solidified body was produced by omitting only the defoaming operation. In this case, as in the above example, even if 120 KIi of carbonized resin and 180 kg of solidifying agent are uniformly mixed in a 200 ton drum, the solidified material swells during the curing process, and some of it falls outside the drum. It jumped out. Therefore, when 60 kg of carbonized resin and 90 kg of solidifying agent were uniformly mixed in a 200 t drum with a reduced amount, the solidified material shown in FIG. 14 was obtained. That is, it was found that when the defoaming operation was omitted, the solidified material contained many air bubbles 68 together with the carbonized resin 58 and the solidifying agent 67. The unconfined compressive strength of the solidified material is also 50 Kg/an
” was a low value.

As described above, a comparison between the case where defoaming is performed and the case where defoaming is omitted in this example is as follows.

(1) With the defoaming cloth, no air bubbles are generated in the solidified material.

As a result, the unconfined compressive strength of the solidified product was over xsoK9/i, and the amount of carbonized resin filled in a 200t drum was 120K.
p or more (9 in 200 or more in terms of dry weight of powdered resin before thermal decomposition).

(2) On the other hand, without defoaming, bubbles are generated in the solidified material, so the unconfined compressive strength of the solidified material is 50 to 9/crII! degree f
, the amount of carbonized resin filled into a 200t drum is 60 to 9.
It will be about.

Example 2 In this example, as in Example 1, after the powdered resin is thermally decomposed, uniform fR solidification is performed using an alkali silicate, but the thermal decomposition equipment and solidification method are different. FIG. 15 shows a system diagram of the processing system used in this example.

The powdered resin 51 in the waste resin tank 52 is pumped into the slurry pump 69 in a state of about 10 ml of slurry, and then transferred to the pyrolysis device 7.
A fixed amount is supplied to 0. The thermal decomposition device 70 is a continuous processing type rotary kill device, and the temperature is maintained at 200 to 400C. The slurry-like powdered resin supplied here is simultaneously dried and thermally decomposed to become a carbonized resin 58.

Note that an inert gas (for example, nitrogen gas) is supplied to the pyrolysis device 1f70 from an inert gas supply pipe 80 via a pulp 81.

Thereby, the thermal decomposition of the ion exchange resin is carried out in an inert gas.

Further, the exhaust gas generated at this time is treated by the exhaust gas treatment device 60 via the pulp 59, as in the first embodiment.

The obtained carbonized resin 58 is temporarily stored in a powder hopper 71. After that, the carbonized resin 58 in the powder hopper 71
A fixed amount (600 kg) of 9 was supplied to the mixer 72, and at the same time, 9 was supplied as a solidifying agent to liquid alkali silicate 400 containing no hardening agent from the solidifying agent tank 73. Thereafter, defoaming was carried out in the mixer 72, but since the liquid alkali silicate takes time to defoam compared to water, it was stirred with the stirring blades 64 and was attached to the kneader 72. Vibration was applied to the ultrasonic oscillator 74 to promote defoaming.

As a result, defoaming was completed in about 2 hours, and after that, 200 Kq of powdered inorganic phosphoric acid compound was poured into the curing agent hopper 66.
was supplied to the mixer 72 and uniformly mixed with the mixture of carbonized resin 58 and alkali silicate. After mixing, valve 7
5f: Approximately 300 yen each in 62 drums.
- Injected to form a solidified product.

The solidified material obtained as above has no air bubbles in the solidified material as in Example 1, and also has an axial compressive strength of 150 to 9/c.
The filling amount of henocarbonized resin in a 200 t drum was also 120 kg.

As is clear from Examples 1 and 2, the pyrolysis equipment can be a batch system such as a fixed bed furnace or a rotary kiln.
A continuous method such as a multistage furnace may be used, and the method of mixing the carbonized resin and the solidifying agent may be the in-drum method of Example 1 or the out-drum method of Example 2. The degassing method may be a simple static method or There are methods that use a combination of stirring, a method that uses ultrasonic waves, a method that uses vacuum degassing, or a method that combines a plurality of these methods. Therefore, in configuring the processing device, any combination of the thermal decomposition device, the mixing method of the carbonized resin and the solidifying agent, and the defoaming method can be used. Further, in Examples 1 and 2, powdered ion exchange resin was treated, but it is obvious that the same method can be applied to particulate ion exchange resin.

Example 3 In this example, granular ion exchange resin (hereinafter abbreviated as granular resin) generated from the reactor water purification system of a pressurized water reactor was converted into carbonized resin by pyrolysis and then molded into pellets. This was solidified in a citram can using an alkali silicate as a solidifying agent. FIG. 16 shows a system diagram of the processing system used in this example.

The used granular resin 76 in the waste resin tank 51 is centrifugally dehydrated in the dehydrator 54 in the same way as in Example 1, and then supplied to the reactor 56 and heated by the heating device 57 to bao.

It was thermally decomposed at C for about 4 hours to become carbonized resin 58.

Incidentally, a cine active gas (for example, nitrogen gas) is supplied to the reactor 56 from an inert gas supply pipe 80 via a pulp 81.

Thereby, the thermal decomposition of the ion exchange resin is carried out in an inert gas.

Carbonized resin 58 was supplied to powder mixer 77 via knife gate valve 61 . On the other hand, the binder 79 from the binder hopper 78 is about 20K for the carbonized resin 100.
q was added. The binder 79 is added to improve the strength of the pellets obtained by the granulator 80. 10 μm 1 length approximately 300
Cellulose fibers of μm were used.

Furthermore, as the binder, other than cellulose fibers, fibrous materials such as metal fibers and carbon fibers, or thermoplastic or thermosetting resins commonly used as adhesives can be used to obtain the same effect. The mixture of carbonized resin 58 and binder 79 thoroughly mixed in powder mixer 77 was sent to granulator 80 via knife gate valve 81 . Here, the granulator 80 uses what is generally called a tabletting machine to compress the powder into pellets at a pressure of about 5 tons/cm. The mixture of polymerized resin and binder was formed into a cylindrical pellet 82 (both height and diameter approximately 20 van), and was supplied to a drum 62 via a chute pipe 83. Here, the drum 62 was placed in a vacuum housing 84. After confirming that the drum 62 is filled with pellets 82,
The inside of the vacuum housing 8j was evacuated by the vacuum pump 85. As a result, vacuum defoaming of the carbonized resin was completed. after that,.

80 kg of a mixture of alkali silicate (solidifying agent) and inorganic phosphoric acid compound (hardening agent) was supplied from the solidifying agent supply tank 86 to the drum can 62 through the valve 87 while maintaining the vacuum state, and the preparation of the solidified product was completed.

Thereafter, the inside of the vacuum housing 84 was brought to normal pressure using the leak pulp 88, and then the drum 62 was taken out and left to cure. As a result of examining the properties of the solidified material obtained after about one month, it was confirmed that the gaps between the pellets were completely filled with the solidifying agent due to the defoaming effect, and that there were no air bubbles. Also, the unconfined compressive strength of the solidified product is 150 K9/crn”
That was it. Furthermore, since the carbonized resin was compression molded into gold pellets 82, it was possible to fill one 200 t drum with carbonized resin up to 150 Kp.

In this example, a tabletting machine was used as the granulator, but it is of course possible to use a briquerating machine, a Nickstruder (extrusion granulator), or the like.

In this example, the pelletized carbonized resin was immediately solidified in a drum, but the obtained pellets 82 were stored as they were for a certain period of time (usually 5 to 10 years) in a human storage hinoki to remove radioactivity. Of course, it is also possible to attenuate and then solidify into a drum or the like as required.

Such a method is generally called intermediate storage and has the following advantages.

In other words, if the ion exchange resin is dried and then removed, as mentioned above, since the ion exchange resin has high water absorption, the pellets will adsorb moisture in the air during storage, and this will cause the pellets to dry. swells and reduces pellet strength. On the other hand, when making pellets of carbonized resin from which ion exchange 2s has been removed, carbonized resin is hydrophobic, so it does not adsorb moisture in the air during storage, so it is This provides an excellent effect of not reducing pellet strength. Figure 817 shows a comparison of pellet strength when untreated resin pellets and carbonized resin pellets are stored intermediately.
Although the pellet strength decreases by half every year, it can be seen that the pellet strength of carbonized resin pellets hardly decreases even after 10 years from the start of storage. However, the data in Figure 17 is based on the actual storage conditions (20C1 temperature 40C) by setting the pellet storage conditions t-40C and temperature 80C.
%), which was subjected to an accelerated test approximately 10 times faster than that of
The intermediate storage period on the horizontal axis is a rough estimate.

This kind of intermediate storage of carbonized resin xft) 1
It was confirmed that if solidification treatment is performed in the drum after defoaming in the same manner as in the above embodiment, the amount filled into the drum can be increased by the attenuation of radioactivity.

In Examples 1 to 3, alkali silicate was used as the solidifying agent, but it is of course possible to use hydraulic substances such as cement, plaster, etc.

Using the processing apparatus of Example 1, we compared the strength of solidified bodies when alkali silicate, high sulfate slag cement, alumina cement, Portland cement, and calcined gypsum were used as solidifying agents. In salt slag cement, alumina cement, and portland cement, it was found that alkali silicate was the most suitable solidifying agent.

High sulfate slag cement, alumina cement, Portland cement, calcined gypsum, etc. are called hydraulic solidifying agents because they have the property of solidifying when they react with water.

〔Effect of the invention〕

According to the present invention, radioactive waste mainly consisting of used ion exchange resin can be solidified with a significant reduction in volume by a simple method, and moreover, can be made into a solidified material with high -axial compressive strength.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the flow of an example of a series of effective thermal decomposition and solidification systems that can carry out the present invention, Figure 2 is a skeletal diagram of an ion exchange resin, and Figure 3 is an air flow diagram of an ion exchange resin. Figure 4 shows the thermogravimetric analysis results of cation exchange resin in the atmosphere. Figure 4 shows the thermogravimetric analysis of cation exchange resin for 1 gB rice and shows the atmosphere dependence during thermal decomposition. Figure 5 shows the thermogravimetric analysis of anion exchange resin. Figure 6 shows the analysis results and shows the atmospheric dependence during thermal decomposition. Figure 6 shows the volume change of the dry ion exchange resin and the carbonized resin of the present invention when immersed in water. Figure 7 shows the relationship between both resins. Fig. 8 is a diagram showing the relationship between the amount of adsorbed gas remaining in the carbonized resin, the solidified body strength, and the carbonized resin filling amount. Figure 10 is a diagram showing the defoaming state of carbonized resin of granular ion exchange resin when immersed in an alkaline solution. Figure 11 is a diagram showing the defoaming state of carbonized resin of granular ion exchange resin when immersed in water, Figure 12 is a diagram showing the defoaming state of carbonized resin of different shapes when immersed in water, and Figure 13 14 is a diagram showing a cross section of a solidified body produced by the present invention, FIG. 14 is a diagram showing a cross section of a solidified body produced by a conventional method, and FIG. 15 is a diagram showing a cross section of a solidified body produced by the conventional method. Figure 16 is a diagram showing the flow of another example of a series of thermal decomposition and solidification systems, Figure 16 is a diagram showing the flow of another example effective for carrying out the present invention, and Figure 17 is a diagram showing the flow of another example of a dry ion exchange system. A diagram showing the strength mineralization of resin pellets and carbonized resin pellets during long-term storage. 51... Powdered ion exchange resin, 52... Waste resin tank, 56... Reactor, 57... Heating device, 58...
・Carbonized resin, 60...Exhaust gas treatment device, 62...
Drum can, 63... Added water tank, 64... Stirring blade, 65... Solidifying agent hopper 1.66... Curing agent hopper, 80... Inert gas supply piping, 81... pulp.

Claims (1)

[Scope of Claims] 1. A method for treating radioactive waste mainly consisting of a used ion exchange resin, in which the radioactive waste is heated to thermally decompose the ion exchange groups of the used ion exchange resin; A method for disposing of radioactive waste, comprising carbonizing the radioactive waste, degassing the gas adsorbed to the radioactive waste, and then solidifying the radioactive waste. 2. A method for treating radioactive waste according to claim 1, wherein the thermal decomposition is carried out in an inert gas. 3. The method according to claim 1, wherein the deaeration is performed by immersing the radioactive waste in a liquid. 4. A radioactive waste treatment method according to claim 3, wherein the liquid is water. 5. The method according to claim 4, wherein the solidification is performed by mixing the radioactive waste, the water, and cement, which is a hydraulic solidifying agent. Method. 6. A method for treating radioactive waste as set forth in claim 4, characterized in that solidification is performed by mixing the radioactive waste, the water, an alkali silicate powder, and a hardening agent. . 7. A method for treating radioactive waste according to claim 3, wherein the liquid is an alkaline silicate solution. 8. The method of claim 7, wherein the solidification is performed by mixing the radioactive waste, the alkaline silicate solution, and a curing agent. 9. In the method according to claim 1, the radioactive waste is degassed by introducing the radioactive waste into a vacuum housing and vacuuming the inside of the vacuum housing. processing method. 10. The method according to claim 9, wherein the solidification is carried out by mixing the radioactive waste, water, and cement, which is a hydraulic solidifying agent. . 11. The method according to claim 9, wherein the solidification is performed by mixing the radioactive waste, an alkaline silicate solution, and a hardening agent. 12. The method according to claim 9, wherein the solidification is performed by mixing the radioactive waste, an alkali silicate powder, a hardening agent, and water. 13. In the method according to claim 6, 8, 11, or 12, the curing agent contains any one of silicon polyphosphate, alkaline earth metal salt, and inorganic phosphoric acid. A method for disposing of radioactive waste, characterized in that it is used. 14. A radioactive waste treatment device mainly made of used ion exchange resin includes a pyrolysis device that heats and carbonizes the radioactive waste, and a pyrolysis device that collects gas generated within the pyrolysis device outside the pyrolysis device. an exhaust gas treatment device for discharging and treating the radioactive waste; a deaeration means for deaeration of gas adsorbed on the carbonized radioactive waste; and a solidification means for solidifying the radioactive waste after deaeration. A radioactive waste processing device characterized by having: 15. The radioactive waste processing apparatus according to claim 14, wherein the pyrolysis apparatus includes an inert gas supply device for supplying inert gas into the apparatus. 16. The radioactive waste processing apparatus according to claim 14, wherein the degassing means has a defoaming container filled with a liquid for degassing. 17. The radioactive waste processing apparatus according to claim 14, wherein the degassing means has a vacuum housing for vacuum degassing. 18. In claim 14, the degassing means has a solidifying agent supply device for supplying a solidifying agent solution for defoaming the radioactive waste to the means, and the solidifying means has a solidifying agent supply device for supplying a solidifying agent solution to the means for defoaming the radioactive waste. A radioactive waste processing apparatus comprising a curing agent supply device that supplies a curing agent for solidifying the radioactive waste. 19. A radioactive waste processing device mainly made of used ion exchange resin, including a pyrolysis device that heats the radioactive waste and carbonizes it, and a pyrolysis device that converts the gas generated in the pyrolysis device into the pyrolysis device. An exhaust gas treatment device for discharging and processing the waste, a granulator for pelletizing the carbonized radioactive waste, and a degassing device for degassing the gas adsorbed on the pelletized radioactive waste. 1. A radioactive waste processing apparatus comprising an air means and a solidification means for solidifying the pelletized radioactive waste after deaeration.