Pretreatment method for supercritical water oxidation of radioactive waste resin

Abstract

A pretreatment method for supercritical water oxidation of radioactive waste resin, the method comprising: pulverizing the radioactive waste resin to obtain waste resin particles of a first size; adding water to a rubber mill and starting the rubber mill; adding the waste resin particles of the first size to the rubber mill and performing a first rubber milling on the waste resin particles of the first size; adding a dispersant to the rubber mill; and performing a second rubber milling on the waste resin particles to obtain a waste resin rubber mill slurry with good fluidity. According to the pretreatment method of the present invention, water is added to the radioactive waste resin, and a mixture of the radioactive waste resin and water is rubber milled into a resin rubber mill slurry by rubber milling, and a dispersant is added during the rubber milling process, so that the added water can be wrapped around the periphery of the resin rubber mill particles in a very stable form, thereby allowing the resin rubber mill slurry to be stored in a stable slurry state for a long time, which is convenient for continuous pumping of the slurry by a peristaltic pump.

Description

Technical Field

[0001] The invention relates to the field of nuclear waste treatment, and in particular to a method for treating radioactive resin produced during the operation of a nuclear power plant by using supercritical water oxidation technology. Background Art

[0002] Waste resin is one of the common radioactive wastes produced in pressurized water reactor nuclear power plants. It has high radioactivity and can usually reach a moderate radioactivity level. The main component of waste resin is a three-dimensional network structure of styrene resin with a cross-linked polymer of styrene and divinylbenzene as the skeleton, which has been sulfonated or aminated. Its structure is stable and its physical and chemical form is difficult to change. If the radioactive waste resin is not inorganically treated, there is a risk of radioactivity during its long-term storage, and there is a risk of producing flammable gas during the decomposition process. The safety and reliability of long-term storage cannot be guaranteed. Therefore, the harmless treatment of waste resin is a major issue that needs to be solved in nuclear power plants.

[0003] Supercritical water oxidation is a new type of wet oxidation technology. It utilizes the fact that organic waste, water, and oxygen are completely miscible in a supercritical water system to oxidize and decompose organic matter into gases such as water and carbon dioxide, and the radioactive nuclides enter into inorganic salts, thereby completing the inorganic treatment of organic waste.

[0004] The supercritical water oxidation treatment of waste resin is divided into three processes: resin degradation, dissolution and oxidation. Among them, the degradation of resin under supercritical conditions takes a long time (generally several minutes to tens of minutes). Once the resin degradation is completed, the dissolution and oxidation reactions can be completed quickly. Therefore, it is required that the waste resin feed cannot enter the reactor in large flow or large quantities. In addition, the feed pump is generally a high-pressure plunger pump, which is not suitable for conveying media with particulate matter. Under low flow rate conditions, the resin is easy to precipitate on the feed pipeline, which eventually leads to blockage of the entire feed pipeline and even causes overpressure of the entire supercritical water oxidation device, posing an industrial safety risk. Summary of the invention

[0005] In view of the above problems, the present invention is proposed to provide a pre-treatment method for supercritical water oxidation of radioactive waste resin that overcomes the above problems or at least partially solves the above problems.

[0006] According to one aspect of the present invention, a pretreatment method for supercritical water oxidation of radioactive waste resin is provided, the pretreatment method comprising the following steps:

[0007] The radioactive waste resin is pulverized to obtain waste resin particles of a first size;

[0008] Adding water into the rubber mill and starting the rubber mill;

[0009] adding the first-sized waste resin particles into the rubber mill and performing a first rubber grinding on the first-sized waste resin particles;

[0010] adding a dispersant to the rubber mill; and

[0011] The waste resin particles are subjected to a second grinding to obtain a waste resin grinding slurry with good fluidity.

[0012] According to the pretreatment method for supercritical water oxidation of radioactive waste resin of the present invention, water is added to the radioactive waste resin, a mixture of the radioactive waste resin and water is grinded into a resin grinding slurry by a grinder, and a dispersant is added during the grinding process, so that the added water can be wrapped around the periphery of the resin grinding particles in a very stable form, thereby allowing the resin grinding slurry to be stored in a stable slurry state for a long time, so that the slurry can be continuously pumped by a peristaltic pump without precipitation and agglomeration in the peristaltic pump, so that the resin grinding slurry can be smoothly and continuously transported to the supercritical water oxidation equipment, so as to perform supercritical water oxidation treatment on the waste resin.

[0013] According to another aspect of the present invention, there is also provided a method for supercritical water oxidation of radioactive waste resin, the method comprising:

[0014] Pre-treating the radioactive waste resin; and

[0015] The radioactive waste resin that has undergone the pretreatment is pumped into a supercritical water oxidation device to perform supercritical water oxidation treatment on the radioactive resin.

[0016] Wherein, the radioactive waste resin is pre-treated according to the pre-treatment method as described above.

[0017] According to the method for supercritical water oxidation of radioactive waste resin of the present invention, a stable slurry is formed by adding a certain dispersant to resin gel grinding, and then transported by a peristaltic pump. The waste resin slurry transported to the supercritical water oxidation equipment reacts fully with oxygen and water under supercritical water oxidation conditions, thereby achieving a high-fold volume reduction and weight reduction of the radioactive waste resin, which is beneficial to the harmless treatment of the radioactive waste resin. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Other objects and advantages of the present invention will become apparent from the following description of the present invention with reference to the accompanying drawings, which will help to provide a comprehensive understanding of the present invention.

[0019] Figure 1 is a flow chart of a pre-treatment method for supercritical water oxidation of radioactive waste resin according to the present invention;

[0020] Figure 2is a flow chart of a method for supercritical water oxidation of radioactive waste resin according to the present invention.

[0021] It should be noted that the drawings are not necessarily drawn to scale, but are merely shown in a schematic manner that does not affect the reader's understanding. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiment is one embodiment of the present invention, not all embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0024] The present invention provides a pretreatment method for supercritical water oxidation of radioactive waste resin. The radioactive waste resin can be ground into fine particles by the method according to the present invention. By adding water and a dispersant during the grinding process, the ground waste resin particles can have good fluidity and good uniform stability, that is, the radioactive waste resin treated by the method according to the present invention can maintain good fluidity and stability for a long time. Therefore, the waste resin particles can be transported by a peristaltic pump without sedimentation and agglomeration inside the peristaltic pump, thereby realizing continuous transportation of the waste resin particles.

[0025] like Figure 1As shown, a flow chart of a pre-treatment method for supercritical water oxidation of radioactive waste resin according to an embodiment of the present invention is shown. The pre-treatment method comprises the following steps: S102: crushing the radioactive waste resin to obtain waste resin particles of a first size; S104: adding water to the rubber mill and starting the rubber mill; S106: adding the waste resin particles of the first size to the rubber mill and performing a first rubber milling on the waste resin particles of the first size; S108: adding a dispersant to the rubber mill; and S110: performing a second rubber milling on the waste resin particles to obtain a waste resin rubber mill slurry with good fluidity. First, since the radioactive waste resin is usually of a large size, it is necessary to crush the radioactive waste resin before adding it to the rubber mill so as to reduce the size of the radioactive waste resin, thereby facilitating the rubber milling process using the rubber mill. By adding water to the rubber mill, the fluidity of the waste resin particles being rubber-milled can be improved, and by adding a dispersant, the flow stability of the waste resin particles can be improved, so that water can be evenly distributed on the periphery of the waste resin particles for a long time, thereby ensuring that they have good fluidity for a long time, thereby facilitating pumping operations by a peristaltic pump. The waste resin particles that have been rubber-milled eventually form a waste resin rubber-milled slurry in the rubber mill, and the added dispersant can ensure the stability of the slurry, making it easier to pump the slurry.

[0026] In order to facilitate the smooth addition of waste resin into the rubber mill, the radioactive waste resin needs to be pre-crushed, and the particle size of the waste resin particles after the crushing process is controlled to be less than 2 mm, that is, the particle size of the first size of waste resin particles is less than 2 mm. This makes it easier to perform rubber grinding on the waste resin particles through the rubber mill.

[0027] In the pretreatment method for supercritical water oxidation of radioactive waste resin according to an embodiment of the present invention, the maximum weight ratio of the first size of waste resin particles added to the rubber mill to water is 13:5, that is, the amount of water added can be increased on this basis, while the amount of waste resin particles cannot be further increased on this basis. For example, 500 grams of water, which can be tap water, can be added to the rubber mill first, and then a total of 1,300 grams of radioactive waste resin particles can be added to the rubber mill. Advantageously, 1,300 grams of radioactive waste resin particles are added to the rubber mill in batches, and while the radioactive waste resin particles that have been added are being rubber-milled, another batch of radioactive waste resin particles is added until 1,300 grams of radioactive waste resin are completely added to the rubber mill, thereby preventing the rubber mill from being blocked.

[0028] Generally, it is necessary to add all the radioactive waste resin particles into the rubber mill within 3 minutes to 8 minutes, and to perform rubber milling on the mixture of radioactive waste resin and water. Advantageously, all the waste resin particles can be added into the rubber mill within 5 minutes. After this rubber milling time, the radioactive waste resin particles have a certain fluidity, and the particle size is about 200 microns.

[0029] Then, a dispersant is added to the radioactive resin after the rubber mill, and the weight of the added dispersant is 0.5%-2% of the weight of the radioactive waste resin, and preferably the weight of the dispersant is 1% of the weight of the radioactive waste resin. Here, 6.5 grams to 26 grams of dispersant can be added to the rubber mill for 1300 grams of radioactive waste resin particles to be processed. Preferably, 13 grams of dispersant is added to 1300 grams of radioactive resin.

[0030] In an embodiment of the present invention, the dispersant is selected from any one of sodium dodecyl sulfonate, sodium dodecyl sulfate, polycarboxylic acid water reducer and sodium styrene sulfonate. Here, the dispersant is determined and selected through experiments. The specific experimental process is to add 500 grams of water to the rubber mill, and then add 1300 grams of radioactive waste resin to the water in the rubber mill in batches, and perform rubber grinding on the radioactive waste resin. The radioactive waste resin can be subjected to rubber grinding for 40 minutes to obtain a radioactive resin rubber grinding slurry. 13 grams of dispersant sodium pyrophosphate is added to the configured radioactive resin rubber grinding slurry, and then the slurry is stirred with a magnetic stirrer at a stirring temperature of 50°C and a stirring time of 90 minutes. After stirring, it is aged overnight, for example, it can be stored for more than 12 hours. The slurry after aging undergoes sedimentation and agglomeration. The results show that sodium pyrophosphate has a poor dispersing effect on waste resin particles, and is therefore not suitable as a dispersant for radioactive resin rubber grinding slurry.

[0031] Several portions of the radioactive resin grinding slurry as described above were prepared in the same manner, and a substance as a dispersant was added to each portion of the grinding slurry to determine whether the corresponding substance was suitable as a dispersant for radioactive resin particles. The dispersants selected for the experiment also included: sodium oleate, sodium hydroxide, sodium silicate, sodium lignin sulfonate, carboxymethyl cellulose, sodium dodecyl sulfonate, sodium dodecyl sulfate, sodium hexametaphosphate, sodium dodecylbenzene sulfonate, polycarboxylic acid water reducer, n-butanol, sodium humate and sodium styrene sulfonate. The experimental method was the same as the experimental method described above for sodium pyrophosphate, that is, first 500 grams of water was added to the grinding mill, and then 1300 grams of radioactive waste resin was added to the grinding mill in batches, and the grinding process was performed for 40 minutes to obtain the resin grinding slurry. Then 13 grams of each of the above dispersants was added to each portion of the above grinding slurry. Then, the mixture was stirred at a temperature of 50° C. for 90 minutes by a magnetic stirrer and aged overnight.

[0032] The following results were obtained through experiments: the resin glue slurry with the addition of dispersant sodium dodecyl sulfonate has good fluidity; the resin glue slurry with the addition of dispersant sodium dodecyl sulfate, polycarboxylate water reducer or sodium styrene sulfonate has general fluidity; while the resin glue slurry with the addition of sodium oleate, sodium hydroxide, sodium silicate, sodium lignin sulfonate, carboxymethyl cellulose, sodium hexametaphosphate, sodium dodecylbenzene sulfonate, n-butanol or sodium humate has sedimentation and agglomeration phenomenon, so the resin glue slurry with the addition of the above dispersants has poor fluidity. Therefore, according to the pretreatment method for supercritical water oxidation of radioactive waste resin of the present invention, sodium dodecyl sulfonate is preferably selected as the dispersant, followed by sodium dodecyl sulfate, polycarboxylate water reducer or sodium styrene sulfonate as the dispersant.

[0033] In addition, relevant experiments were conducted on the amount of dispersant added. For example, when sodium dodecyl sulfate was used as a dispersant, 0.5%, 1%, 2%, 3%, 4%, 5% and 6% of the weight of the resin were added to the resin grinding slurry after the rubber mill. The experimental results showed that the amount of dispersant added did not have much effect on the fluidity of the resin grinding slurry. It was only when the amount of dispersant added was less than 1% of the weight of the radioactive resin particles that the fluidity of the resin grinding slurry was slightly worse. When the amount of dispersant added was greater than 2%, more bubbles were generated in the grinding slurry, which was not conducive to the pumping of the grinding slurry. Therefore, the weight of the added dispersant was 0.5%-2% of the weight of the radioactive resin to be ground.

[0034] In an embodiment of the pretreatment method for supercritical water oxidation of radioactive waste resin according to the present invention, the process of adding radioactive waste resin particles to the rubber mill in batches and grinding the resin particles at the same time is called the first rubber grinding, and the duration of the first rubber grinding is usually controlled to be 3-8 minutes, preferably controlled to be 5 minutes. The rubber grinding process after the radioactive waste resin particles are completely added is called the second rubber grinding, and the duration of the second rubber grinding is controlled to be at least 40 minutes. The particle size of the waste resin particles after the second rubber grinding is generally less than 50 microns. Since the rubber mill will generate heat as the rubber grinding time increases during operation, and overheating will occur if the working time is too long, in order to prevent the rubber mill from overheating, the single working time of the rubber mill is controlled to be about 40 minutes. Therefore, the duration of the second rubber grinding is advantageously controlled to be 40 minutes. The particle size of the radioactive waste resin particles after the second rubber grinding is between 10 microns and 50 microns.

[0035] In addition, the effect of dispersants on the fluidity of different types of radioactive waste resins was verified. Relevant experiments were carried out using irradiated 732 resin, 717 resin and macroporous D296 resin. Here, 500 grams of water were added to the rubber mill, and then 1300 grams of radioactive waste 732 resin and 13 grams of sodium dodecyl sulfate were added to the rubber mill in batches within about 5 minutes. The rubber milling process was then continued for 40 minutes to obtain a resin rubber mill slurry. The paddle was stirred with a glass rod, and the fluidity was good. The peristaltic pump could be transported normally, and there was no obvious deposition of the resin in the pipeline. After aging overnight, the fluidity of the resin paddle did not change much, so it could meet the requirements of transportation by a peristaltic pump. The same experiments were also carried out on 717 resin and macroporous D296 resin, and the results were basically the same. Therefore, sodium dodecyl sulfate fully meets the conditions for being a dispersant for radioactive waste resins.

[0036] According to the pretreatment method for supercritical water oxidation of radioactive waste resin of the present invention, water is added to the radioactive waste resin, a mixture of the radioactive waste resin and water is grinded into a resin grinding slurry by a grinder, and a dispersant is added during the grinding process, so that the added water can be wrapped around the periphery of the resin grinding particles in a very stable manner, thereby allowing the resin grinding slurry to be stored in a stable slurry state for a long time, so that the slurry can be continuously pumped by a peristaltic pump without precipitation and agglomeration in the peristaltic pump, so that the water-quality grinding slurry can be smoothly and continuously transported to the supercritical water oxidation equipment, so as to perform supercritical water oxidation treatment on the waste resin.

[0037] The present invention also provides a method for supercritical water oxidation of radioactive waste resin, the method comprising the following steps: S202: pre-treating the radioactive waste resin; and, S204: pumping the pre-treated radioactive waste resin into a supercritical water oxidation device to perform supercritical water oxidation treatment on the radioactive resin, wherein the pre-treating of the radioactive waste resin comprises pre-treating the radioactive waste resin according to the pre-treating method for supercritical water oxidation of radioactive waste resin as described above. The method for supercritical water oxidation of radioactive waste resin according to the present invention adopts the method of adding a certain dispersant to resin gel grinding to form a stable slurry, and then transports it through a peristaltic pump, and the waste resin slurry transported to the supercritical water oxidation device reacts fully with oxygen and water under supercritical water oxidation conditions, thereby achieving high volume reduction and weight reduction of the radioactive waste resin, which is beneficial to the harmless treatment of the radioactive waste resin.

[0038] Regarding the embodiments of the present invention, it should also be noted that, in the absence of conflict, the embodiments of the present invention and the features therein may be combined with each other to obtain new embodiments.

[0039] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. The protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A pretreatment method for supercritical water oxidation of radioactive waste resin, characterized in that: The pre-treatment method comprises the following steps: The radioactive waste resin is pulverized to obtain waste resin particles of a first size; Adding water into the rubber mill and starting the rubber mill; adding the first-sized waste resin particles into the rubber mill and performing a first rubber grinding on the first-sized waste resin particles; adding a dispersant to the rubber mill; and Performing a second rubber grinding on the waste resin particles to obtain a waste resin rubber grinding slurry with good fluidity; By adding water to the rubber mill, the fluidity of the waste resin particles being rubber-milled can be improved; and by adding the dispersant, the stability of the flow of the waste resin particles can be improved, so that water can be evenly distributed on the periphery of the waste resin particles for a long time, thereby ensuring that the waste resin particles have good fluidity for a long time, thereby facilitating the pumping operation by the peristaltic pump; The weight ratio of the first size waste resin particles to water added to the rubber mill is at most 13:

5.

2. The pretreatment method for supercritical water oxidation of radioactive waste resin according to claim 1, characterized in that: The particle size of the waste resin particles of the first size is less than 2 mm.

3. The pretreatment method for supercritical water oxidation of radioactive waste resin according to claim 1, characterized in that: The step of adding the first-size waste resin particles into the rubber mill and performing a first rubber grinding on the first-size waste resin particles comprises: adding the first size of waste resin particles into the rubber mill in batches; and The waste resin particles of the first size are added to the rubber mill while the waste resin particles added to the rubber mill are being rubber-milled.

4. The pretreatment method for supercritical water oxidation of radioactive waste resin according to claim 3, characterized in that: The duration of the batch addition is 3 minutes to 8 minutes.

5. The pretreatment method for supercritical water oxidation of radioactive waste resin according to claim 4, characterized in that: The duration of the batch addition is 5 minutes.

6. The pretreatment method for supercritical water oxidation of radioactive waste resin according to claim 1, characterized in that: The weight of the dispersant added to the gel mill is at least 0.5% to 2% of the weight of the first size of radioactive waste resin added.

7. The pretreatment method for supercritical water oxidation of radioactive waste resin according to claim 6, characterized in that: The weight of the dispersant added to the gel mill is 1% of the weight of the radioactive waste resin of the first size added.

8. The pretreatment method for supercritical water oxidation of radioactive waste resin according to claim 1, characterized in that: The dispersant is any one of sodium dodecyl sulfonate, sodium dodecyl sulfate, polycarboxylate water reducer and sodium styrene sulfonate.

9. The pretreatment method for supercritical water oxidation of radioactive waste resin according to claim 8, characterized in that: The dispersant is sodium dodecyl sulfate.

10. The pretreatment method for supercritical water oxidation of radioactive waste resin according to claim 1, characterized in that: The duration of the second rubber grinding is at least 40 minutes.

11. The pretreatment method for supercritical water oxidation of radioactive waste resin according to claim 1, characterized in that: The particle size of the waste resin particles in the waste resin slurry is less than 50 microns.

12. A method for supercritical water oxidation of radioactive waste resin, characterized in that: The method comprises: Pre-treating the radioactive waste resin; and The radioactive waste resin that has undergone the pretreatment is pumped into a supercritical water oxidation device to perform supercritical water oxidation treatment on the radioactive waste resin. Wherein, the radioactive waste resin is pre-treated according to the pre-treatment method according to any one of claims 1-11.

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