Degradable decontamination formula and decontamination method for nuclear reactor

Abstract

The invention discloses a degradable decontamination formula for a nuclear reactor and a decontamination method, and relates to the technical field of nuclear industry. The decontamination formula comprises the following components in percentage by mass: 0.1-2% of an oxidizing agent and the balance of deionized water, the degradable reduction complexing liquid comprises at least two of a scale inhibitor, a reducing agent and a complexing agent, and comprises the following components in percentage by mass: 0-1% of the scale inhibitor, 0-2% of the reducing agent, 0-1.5% of the complexing agent and the balance of deionized water. The decontamination method comprises the steps of oxidation treatment, first-time deionized water rinsing, reduction complexing treatment, second-time deionized water rinsing and inorganic treatment of the decontaminated radioactive waste liquid. According to the degradable decontamination formula, in-service decontamination is carried out on a high-temperature and high-pressure test loop of a light-water type research reactor, the decontamination factor reaches 100 or above, the corrosion depth of stainless steel parts is about 0.2 micron, and the organic matter degradation rate reaches 98% or above after radioactive waste liquid obtained after decontamination is subjected to inorganic treatment.

Description

Technical Field

[0001] The present application relates to the field of nuclear industry technology, and in particular to a degradable decontamination formula and a decontamination method for a nuclear reactor. Background Art

[0002] During the operation of the reactor, the fission products and actinide nuclides released from the fuel assemblies, as well as the activation products produced by other factors, will enter the high-temperature and high-pressure test loop cooling system of the research reactor. They will be deposited on the pipes and produce radioactive contamination. Before the maintenance, overhaul and modification of the reactor system, it is necessary to perform in-service chemical decontamination on the loop to remove radioactive contamination, reduce the radiation field dose, and achieve the purpose of reducing the exposure dose of the staff. At the same time, it can provide a "clean" environment for the loop, provide a guarantee for the subsequent loop water quality to meet the operation requirements; maximize the reuse of existing loop resources, greatly shorten the loop construction cycle, and reduce expenses.

[0003] To this end, a large number of research and development and application of decontamination methods and decontamination formulas have been carried out at home and abroad. So far, more than 20 chemical decontaminants have been successfully used in the decontamination of nuclear facilities and have achieved good results. Including NS-1 (improved) method, POD method in the UK, O3-CAN-DECON method developed in Canada, formic acid / formaldehyde decontamination technology developed in Switzerland, etc. From the perspective of a large number of decontamination practices, effects, costs, etc. at home and abroad, the above-mentioned processes can achieve good expected results for decontamination, but for in-service decontamination, the above-mentioned processes as a whole still have some shortcomings: 1) The current decontamination process is complicated to operate; 2) Inorganic acids have strong dissolving ability for oxides, but they also have serious corrosion to the materials of equipment, pipelines, etc., which may cause safety hazards in the subsequent use of the circuit; 3) Some are not expensive, but the decontamination effect is poor, the decontamination efficiency is low, and it is impossible to provide the necessary conditions for the use and maintenance of the subsequent circuit; 4) Some decontamination implementation conditions are harsh, such as high reaction temperature, high concentration of chemical reagents, and difficult to control. In addition, the above-mentioned decontamination process will produce a large amount of difficult-to-degrade organic radioactive wastewater after decontamination. The presence of organic matter in decontaminated waste liquid is not only not conducive to the storage of radioactive waste liquid, but also increases the difficulty of waste liquid treatment, which is mainly reflected in the following four aspects: 1) In the waste liquid, organic matter may form complexes with radioactive nuclides in ionic state, making it difficult to separate radioactive nuclides, thereby affecting the effect of coagulation and precipitation; 2) The presence of organic matter causes foam entrainment in the waste liquid during coagulation and evaporation, reducing the decontamination efficiency; 3) In the final waste, the presence of organic matter reduces the adsorption of radioactive nuclides and accelerates the migration rate of radioactive nuclides in groundwater, soil and surface water, which has an adverse effect on the solidification and disposal of waste liquid; 4) Organic matter undergoes radiation and chemical degradation, producing CO 2 , CO and H 2etc., which makes the waste body less stable. Therefore, it is necessary to pre-treat the organic matter in the decontamination waste liquid before further treating the radioactive waste liquid in the conventional way. In response to the above problems, advanced decontamination technologies such as chemical oxidation, photochemical oxidation, electrochemical oxidation, supercritical wet oxidation and adsorption have been developed. However, due to the stable chemical properties of substances such as oxalic acid, citric acid, and EDTA, the above methods have certain limitations in the treatment of radioactive organic waste liquid, mainly because the degradation of organic matter is not complete and the degradation efficiency of organic matter is low, which cannot fundamentally solve the problem that radioactive organic waste liquid is difficult to treat after decontamination by existing decontamination formulas. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art or related art.

[0005] The first aspect of the present invention provides a degradable decontamination formulation for a nuclear reactor, comprising:

[0006] Oxidation cleaning solution, the oxidant accounts for 0.1% to 2% by mass, and the rest is deionized water;

[0007] The degradable reducing complex liquid comprises at least two of a scale inhibitor, a reducing agent and a complexing agent. Calculated by mass fraction, the scale inhibitor accounts for 0-1%, the reducing agent accounts for 0-2%, the complexing agent accounts for 0-1.5%, and the rest is deionized water.

[0008] Further, the oxidant is one or more of potassium persulfate, cerium ammonium nitrate, hydrogen peroxide, nitric acid and potassium permanganate;

[0009] The scale inhibitor is one or more of malic acid, acrylic acid, organic phosphonic acid and polyaspartic acid;

[0010] The reducing agent is one or more of oxalic acid, ferrous nitrate, sodium thiosulfate, ascorbic acid and hydrazine;

[0011] The complexing agent is one or more of succinic acid, sodium diaminodisuccinate, nitrilotriacetic acid, and disodium ethylenediaminetetraacetate.

[0012] Furthermore, the decontamination formula comprises:

[0013] An oxidative cleaning solution, wherein the oxidant in the oxidative cleaning solution is potassium permanganate, with a mass fraction of 0.4% to 0.6%, and the rest is deionized water;

[0014] The degradable reducing complex liquid comprises a scale inhibitor of polyaspartic acid with a mass fraction of 0.16% to 0.24%, a reducing agent of oxalic acid with a mass fraction of 0.4% to 0.6%, a complexing agent of sodium diaminodisuccinate with a mass fraction of 0.4% to 0.6%, and the rest of the liquid is deionized water.

[0015] Furthermore, the degradable decontamination formula is used to carry out in-service decontamination of the high-temperature and high-pressure test circuit of a light water research reactor, and the decontamination factor reaches more than 100; the corrosion depth of stainless steel parts is 0.18 to 0.22 μm; and the organic matter degradation rate of the decontaminated radioactive waste liquid reaches more than 98% after inorganic treatment.

[0016] A second aspect of the present invention provides a degradable decontamination method for a nuclear reactor, comprising:

[0017] Oxidation treatment, injecting the above-mentioned oxidation decontamination liquid into the high-temperature and high-pressure test loop of the light water research reactor, and discharging the oxidation treatment waste liquid after the circulation reaction;

[0018] The first deionized water rinse is to rinse the light water research reactor high temperature and high pressure test circuit after the oxidation treatment with deionized water;

[0019] Reduction and complexation treatment, injecting the above-mentioned degradable reduction and complexation liquid into the high-temperature and high-pressure test loop of the light water research reactor after the first deionized water rinse, and discharging the reduction and complexation treatment waste liquid after the cycle reaction;

[0020] A second deionized water rinse, using deionized water to rinse the light water research reactor high temperature and high pressure test circuit after the reduction and complexation treatment;

[0021] Inorganic treatment of decontaminated radioactive waste liquid.

[0022] Furthermore, in the oxidation treatment, the cycle reaction temperature is 80°C to 95°C, and the cycle time is 4h to 10h.

[0023] Furthermore, the first deionized water rinsing is performed at room temperature for 1 hour to 2 hours.

[0024] Furthermore, in the reduction complexation treatment, the cycle reaction temperature is 80°C to 95°C, and the cycle time is 4h to 10h.

[0025] Furthermore, the second deionized water rinsing is performed at room temperature until the pH of the rinsing solution is 6 to 9 and the specific resistivity is greater than 5×10 5 After Ω·m, stop rinsing.

[0026] Furthermore, the inorganic treatment of the decontaminated radioactive waste liquid includes:

[0027] Inorganic treatment of the oxidation waste liquid and the reduction complexation waste liquid, adjusting the pH of the oxidation waste liquid to 1.5-2.5, and then mixing it with the reduction complexation waste liquid to obtain a mixed decontamination waste liquid, adding hydrogen peroxide to the mixed decontamination waste liquid, and reacting at 40°C-60°C for 2h-4h;

[0028] The pH value of the oxidation waste liquid is adjusted to 1.5-2.5 by using nitric acid with a mass concentration of 0.5%-1%; and the mass concentration of hydrogen peroxide in the mixed decontamination waste liquid is controlled to be 1.5-2.5%.

[0029] Compared with the prior art, the beneficial effects of the degradable decontamination formula and decontamination method for nuclear reactors provided by the present invention include: 1) the decontamination formula is low in price and the decontamination method is simple to operate; 2) the decontamination factor is high; 3) the damage to the substrate is small; 4) the degradation rate of organic matter in the radioactive waste liquid after decontamination is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the following detailed description of the preferred embodiment.The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application.

[0031] Figure 1 This is the morphology of the sample before decontamination provided in Example 1 of the present application.

[0032] Figure 2 This is the morphology of the sample after decontamination provided in Example 1 of the present application. DETAILED DESCRIPTION

[0033] In order to better understand the above-mentioned technical scheme, the technical scheme of the embodiments of the present application is described in detail below through the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present application and the specific features in the embodiments are detailed descriptions of the technical scheme of the embodiments of the present application, rather than limitations on the technical scheme of the present application. In the absence of conflict, the embodiments of the present application and the technical features in the embodiments may be combined with each other.

[0034] A first aspect of an embodiment of the present invention provides a degradable decontamination formula for in-service decontamination of a high-temperature and high-pressure test loop of a light water research reactor, comprising:

[0035] The oxidative cleaning liquid (PP liquid) has an oxidant content of 0.1% to 2% by mass, and the rest is deionized water; preferably, the oxidative cleaning liquid has an oxidant content of 0.3% to 1% by mass, and the rest is deionized water; more preferably, the oxidative cleaning liquid has an oxidant content of 0.4% to 0.6% by mass, and the rest is deionized water;

[0036] The degradable reducing complex liquid (DIP liquid) comprises at least two of a scale inhibitor, a reducing agent and a complexing agent, wherein, by mass fraction, the scale inhibitor accounts for 0-1%, the reducing agent accounts for 0-2%, the complexing agent accounts for 0-1.5%, and the rest is deionized water; preferably, the scale inhibitor accounts for 0.1%-0.5%, the reducing agent accounts for 0.3%-1%, the complexing agent accounts for 0.3%-1%, and the rest is deionized water; further preferably, the scale inhibitor accounts for 0.16%-0.24%, the reducing agent accounts for 0.4%-0.6%, the complexing agent accounts for 0.4%-0.6%, and the rest is deionized water.

[0037] In some embodiments, the oxidant is one or more of potassium persulfate, ammonium cerium nitrate, hydrogen peroxide, nitric acid and potassium permanganate;

[0038] The scale inhibitor is one or more of malic acid, acrylic acid, organic phosphonic acid and polyaspartic acid;

[0039] The reducing agent is one or more of oxalic acid, ferrous nitrate, sodium thiosulfate, ascorbic acid and hydrazine;

[0040] The complexing agent is one or more of succinic acid, sodium diaminodisuccinate, nitrilotriacetic acid, and disodium ethylenediaminetetraacetate.

[0041] In the preferred decontamination formula, the oxidant in the oxidation decontamination liquid is potassium permanganate, with a mass fraction of 0.4% to 0.6%, and the rest is deionized water; the scale inhibitor in the degradable reduction complex liquid is polyaspartic acid, with a mass fraction of 0.16% to 0.24%; the reducing agent is oxalic acid, with a mass fraction of 0.4% to 0.6%; the complexing agent is sodium diaminodisuccinate with a mass fraction of 0.4% to 0.6%, and the rest is deionized water. This decontamination formula is used to carry out in-service decontamination of the high-temperature and high-pressure test circuit of the light water research reactor, and the decontamination factor reaches more than 100; the corrosion depth of stainless steel parts is 0.18 to 0.22μm; and the degradation rate of organic matter after inorganic treatment reaches more than 98%.

[0042] Furthermore, the preferred formula is adopted: the oxidant in the oxidation decontamination liquid is potassium permanganate, with a mass fraction of 0.5%, and the rest is deionized water; in the degradable reduction complex liquid: the scale inhibitor is polyaspartic acid, with a mass fraction of 0.2%; the reducing agent is oxalic acid, with a mass fraction of 0.5%; the complexing agent is sodium diaminodisuccinate with a mass fraction of 0.5%, and the rest is deionized water. Using this decontamination formula, the high-temperature and high-pressure test loop of the light water research reactor was decontaminated in service, and the decontamination factor reached 121; the corrosion depth of stainless steel parts was 0.194μm; and the degradation rate of organic matter after inorganic treatment reached 98.3%.

[0043] A second aspect of an embodiment of the present invention provides a degradable decontamination method for in-service decontamination of a high-temperature and high-pressure test loop of a light water research reactor, comprising:

[0044] Oxidation treatment, injecting the above-mentioned oxidation decontamination liquid into the high-temperature and high-pressure test loop of the light water research reactor, and discharging the oxidation treatment waste liquid after the circulation reaction;

[0045] The first deionized water rinse is to rinse the light water research reactor high temperature and high pressure test circuit after the oxidation treatment with deionized water;

[0046] Reduction and complexation treatment, injecting the above-mentioned degradable reduction and complexation liquid into the high-temperature and high-pressure test loop of the light water research reactor after the first deionized water rinse, and discharging the reduction and complexation treatment waste liquid after the cycle reaction;

[0047] A second deionized water rinse, using deionized water to rinse the light water research reactor high temperature and high pressure test circuit after the reduction and complexation treatment;

[0048] Inorganic treatment of decontaminated radioactive waste liquid.

[0049] In some embodiments, during the oxidation treatment, the cycle reaction temperature is 80° C. to 95° C., and the cycle time is 4 h to 10 h.

[0050] It is understandable that the oxidation treatment needs to increase the cyclic reaction temperature to speed up the oxidation treatment, shorten the decontamination time during the actual oxidation treatment decontamination operation, and reduce the radiation dose of the staff. The reaction temperature and reaction time are the ranges determined by single variable experiments. Through multiple tests, the reaction temperature and reaction time were changed respectively, and the corrosion depth and decontamination factor of the samples after the test were examined. It was finally determined that in the oxidation treatment, the cyclic reaction temperature is 80℃~95℃, and the cycle time is 4h~10h. Preferably, the cyclic reaction temperature is 90℃~95℃, and the cycle time is 8h~10h.

[0051] Specifically, when the temperature exceeds 95°C, the oxidative decontamination liquid will evaporate in large quantities, affecting the decontamination effect. Specifically, a large amount of water in the oxidative decontamination liquid evaporates, increasing the concentration of the oxidative decontamination liquid and deepening the corrosion. In addition, if the decontamination temperature is too high, it will put a lot of pressure on the heating equipment, indirectly extending the operation time. When the temperature is lower than 80°C, the decontamination effect will deteriorate, probably because the heat required for the reaction cannot be provided. When the reaction time exceeds 10h, the oxidative decontamination liquid will over-react with the surface oxide layer, aggravating the corrosion of the substrate material and increasing the corrosion depth. When the reaction time is less than 4h, the oxidative decontamination liquid will not have enough time to react with the surface oxide layer, and the radioactive substances on the surface of the material cannot be effectively removed, and the decontamination factor is greatly reduced.

[0052] In some embodiments, during the reduction complexation treatment, the cycle reaction temperature is 80° C. to 95° C., and the cycle time is 4 h to 10 h.

[0053] It is understandable that the reduction treatment needs to increase the cyclic reaction temperature to speed up the reduction treatment, shorten the decontamination time during the actual reduction treatment process, and reduce the radiation dose of the staff. The reaction temperature and reaction time are the ranges determined by single variable experiments. Through multiple experiments, the reaction temperature and reaction time were changed respectively, and the corrosion depth and decontamination factor of the samples after the test were examined. It was finally determined that in the reduction complex treatment, the cyclic reaction temperature is 80℃~95℃, and the cycle time is 4h~10h. Preferably, the cyclic reaction temperature is 90℃~95℃, and the cycle time is 8h~10h.

[0054] Specifically, when the temperature exceeds 95°C, the degradable reducing complex liquid will volatilize in large quantities, affecting the decontamination effect. Specifically, a large amount of water in the degradable reducing complex liquid evaporates, increasing the concentration of the decontamination liquid and deepening the corrosion. In addition, if the decontamination temperature is too high, it will put a lot of pressure on the heating equipment, indirectly extending the operation time. When the temperature is lower than 80°C, the decontamination effect will deteriorate, probably because the heat required for the reaction cannot be provided. When the reaction time exceeds 10h, the degradable reducing complex liquid will over-react with the surface oxide layer, aggravating the corrosion of the substrate material and increasing the corrosion depth. When the reaction time is less than 4h, the degradable reducing complex liquid will not have enough time to react with the surface oxide layer, and the radioactive substances on the surface of the material cannot be effectively removed, and the decontamination factor is reduced.

[0055] In some embodiments, the first deionized water rinse is performed at room temperature for 1 hour to 2 hours.

[0056] It is understandable that the first rinse is to remove the oxidized detergent remaining on the surface of the object to be decontaminated and ensure the normal use of the reducing detergent. Rinsing at room temperature for 1 to 2 hours is sufficient. If rinsing is not performed, the oxidized detergent remaining on the surface of the object to be decontaminated will undergo an oxidation-reduction reaction with the added reducing detergent, thereby reducing the decontamination effect.

[0057] In some embodiments, the second deionized water rinse is performed at room temperature until the pH of the rinse solution is 6 to 9 and the specific resistivity is greater than 5×10 5 After Ω·m, stop rinsing.

[0058] It is understandable that the second rinse is to fully wash the reducing decontamination liquid remaining on the surface of the decontaminated object to ensure the normal operation of the subsequent reactor. If rinsing is not performed, the reducing decontamination liquid remaining on the surface of the decontaminated object will affect the normal operation of the subsequent reactor. Therefore, it is necessary to clean it until the pH of the rinsing liquid is 6-9 and the specific resistivity is greater than 5×10 5 Ω·m.

[0059] In some embodiments, the inorganic treatment of the decontaminated radioactive waste liquid includes:

[0060] The oxidation treatment waste liquid and the reduction complex treatment waste liquid are subjected to inorganic treatment, the pH value of the oxidation treatment waste liquid is adjusted to 1.5-2.5, and then mixed with the reduction complex treatment waste liquid to obtain a mixed decontamination waste liquid, hydrogen peroxide is added to the mixed decontamination waste liquid, and reacted at 40°C-60°C for 2h-4h; wherein, the pH value of the oxidation treatment waste liquid is adjusted to 1.5-2.5 using nitric acid with a mass concentration of 0.5%-1%; and the mass concentration of hydrogen peroxide in the mixed decontamination waste liquid is controlled to be 1.5-2.5%.

[0061] Specifically, hydrogen peroxide has strong oxidizing properties. By appropriately adding hydrogen peroxide and adjusting the mass concentration of hydrogen peroxide in the mixed decontamination waste liquid to 1.5-2.5%, the effect of hydrogen peroxide can be best exerted. A reaction temperature higher than 60°C will cause a large amount of hydrogen peroxide to volatilize, and a temperature lower than 40°C will seriously affect the oxidation effect of hydrogen peroxide. The preferred reaction temperature is 55°C-60°C.

[0062] In summary, the degradable decontamination formula and decontamination method provided by the embodiments of the present invention are used for in-service decontamination of a high-temperature and high-pressure test loop of a light water research reactor, and have the following beneficial effects:

[0063] 1) High decontamination factor. The oxidant and reductant used in the decontamination process can effectively dissolve the oxide layer on the surface of the stainless steel, making the decontamination process excellent in decontamination performance. After decontamination, the surface of the stainless steel changes from black to bright metallic color. The radioactivity on the surface of the decontamination pipeline sample is close to the local environment. In the preferred case, the decontamination factor is as high as 100 or more. This process can effectively reduce the level of extranuclear radiation, reduce the radiation dose to the staff, and facilitate the staff to inspect and maintain the equipment.

[0064] 2) Little damage to the substrate. In the preferred case, the corrosion depth of the stainless steel parts in a single operation of the decontamination process is about 0.2um. Under 500x electron microscope observation, the stainless steel surface is smooth as a whole, without obvious intergranular corrosion. Experiments have shown that this process has extremely low damage to the stainless steel substrate to be decontaminated, can ensure the safety of the system to be decontaminated, and is suitable for in-service decontamination of nuclear facilities.

[0065] 3) Low price and simple operation. In the chemical formula of the decontamination liquid of this process, the concentration of chemical reagents is low, which reduces the amount of chemical decontamination reagents used, the comprehensive decontamination cost is low, the operation is simple, the reagents used are industrial products, the price is cheap, easy to purchase, and the amount of waste generated is small.

[0066] 4) High degradation rate of organic matter. The organic waste liquid after decontamination is subjected to inorganic treatment. In the preferred case, the degradation rate of organic matter in the waste liquid reaches more than 98%, which has good social and economic value.

[0067] Example 1 A degradable decontamination formula and decontamination method for in-service decontamination of a high-temperature and high-pressure test loop of a light water research reactor

[0068] (I) Decontamination formula: see Table 1 for details.

[0069] (II) Decontamination process

[0070] The degradable decontamination method of embodiment 1 comprises the following steps:

[0071] 1) Inject the PP liquid into the loop system through a pump, circulate continuously, the reaction temperature is 95°C, the reaction time is 8 hours, and then drain it;

[0072] 2) Rinse the circuit system with deionized water, circulate continuously, and rinse the residual PP liquid, pollutants and other soluble impurities in the circuit. The reaction temperature is room temperature and the cleaning time is 1 hour;

[0073] 3) Inject the DIP solution into the loop system and circulate it continuously. Through reduction and complexation, the insoluble high-valent metal oxides in the radioactive oxidation corrosion deposits on the surface of the stainless steel parts are reduced to low-valent ions. The decontamination temperature is controlled at 95°C and the reaction time is 8 hours.

[0074] 4) Rinse the circuit system with deionized water, and circulate continuously to rinse the DIP detergent, pollutants and other impurities remaining on the decontaminated parts. The reaction temperature is room temperature and the cleaning time is 1 hour. At this time, the pH of the rinse liquid is 7 and the specific resistivity is greater than 5×10 5 Ω·m;

[0075] 5) After the decontamination is completed, the decontamination waste liquid in step 1) is adjusted to a pH of 2.0 and mixed with the decontamination waste liquid in step 3), and then hydrogen peroxide is added to the mixed decontamination waste liquid to a mass concentration of 2%, reacted at 60° C. for 2 hours, and discharged into the three-waste treatment system.

[0076] (III) Effect evaluation

[0077] Sampling was performed and the surface of the decontaminated object was observed using a high-magnification electron microscope. The surface dose of the radioactive waste liquid evaporator was measured using a portable surface contamination meter. The decontaminated waste liquid was inorganicized using hydrogen peroxide and the degradation rate of organic matter was calculated. See Appendix 2 for details.

[0078] Example 2

[0079] (I) Decontamination formula: see Table 1 for details.

[0080] (ii) Decontamination method: same as in Example 1.

[0081] (III) Effect evaluation: See Table 2 for details.

[0082] Example 3

[0083] (I) Decontamination formula: see Table 1 for details.

[0084] (ii) Decontamination process: same as in Example 1.

[0085] (III) Effect evaluation: See Table 2 for details.

[0086] Example 4

[0087] (I) Decontamination formula: see Table 1 for details.

[0088] (ii) Decontamination method: same as in Example 1.

[0089] (III) Effect evaluation: See Table 2 for details.

[0090] Example 5

[0091] (I) Decontamination formula: see Table 1 for details.

[0092] (ii) Decontamination method: same as in Example 1.

[0093] (III) Effect evaluation: See Table 2 for details.

[0094] Example 6

[0095] (I) Decontamination formula: see Table 1 for details.

[0096] (ii) Decontamination methods:

[0097] The degradable decontamination method of Example 6 comprises the following steps:

[0098] 1) Inject the PP liquid into the loop system through a pump, circulate continuously, the reaction temperature is 80°C, the reaction time is 8h, and then drain it;

[0099] 2) Rinse the circuit system with deionized water, circulate continuously, and rinse the residual PP liquid, pollutants and other soluble impurities in the circuit. The reaction temperature is room temperature and the cleaning time is 1 hour;

[0100] 3) Inject the DIP solution into the loop system and circulate it continuously. Through reduction and complexation, the insoluble high-valent metal oxides in the radioactive oxidation corrosion deposits on the surface of the stainless steel parts are reduced to low-valent ions. The decontamination temperature is controlled at 80°C and the reaction time is 8 hours.

[0101] 4) Rinse the circuit system with deionized water, and circulate continuously to rinse the residual DIP detergent, pollutants and other impurities on the decontaminated parts. The reaction temperature is room temperature and the cleaning time is 1 hour. At this time, the pH of the rinse liquid is between 6 and 9, and the specific resistivity is greater than 5×10 5 Ω·m;

[0102] 5) After the decontamination is completed, the decontamination waste liquid in step 1) is adjusted to a pH of 2.0 and mixed with the decontamination waste liquid in step 3), and then hydrogen peroxide is added to the mixed decontamination waste liquid to a mass concentration of 2%, reacted at 60° C. for 2 hours, and discharged into the three-waste treatment system.

[0103] (III) Effect evaluation: See Table 2 for details.

[0104] Example 7

[0105] (I) Decontamination formula: see Table 1 for details.

[0106] (II) Decontamination process:

[0107] The degradable decontamination method of Example 7 comprises the following steps:

[0108] 1) Inject the PP liquid into the loop system through a pump, circulate continuously, the reaction temperature is 95°C, the reaction time is 10 hours, and then drain it;

[0109] 2) Rinse the circuit system with deionized water, circulate continuously, and rinse the residual PP liquid, pollutants and other soluble impurities in the circuit. The reaction temperature is room temperature and the cleaning time is 1 hour;

[0110] 3) Inject the DIP solution into the loop system and circulate it continuously. Through reduction and complexation, the insoluble high-valent metal oxides in the radioactive oxidation corrosion deposits on the surface of the stainless steel parts are reduced to low-valent ions. The decontamination temperature is controlled at 95°C and the reaction time is 10 hours.

[0111] 4) Rinse the circuit system with deionized water, and circulate continuously to rinse the residual DIP detergent, pollutants and other impurities on the decontaminated parts. The reaction temperature is room temperature and the cleaning time is 1 hour. At this time, the pH of the rinse liquid is between 6 and 9, and the specific resistivity is greater than 5×10 5 Ω·m;

[0112] 5) After the decontamination is completed, the decontamination waste liquid in step 1) is adjusted to a pH of 2.0 and mixed with the decontamination waste liquid in step 3), and then hydrogen peroxide is added to the mixed decontamination waste liquid to a mass concentration of 2%, reacted at 40° C. for 2 hours, and discharged into the three-waste treatment system.

[0113] (III) Effect evaluation: See Table 2 for details.

[0114] Example 8

[0115] (I) Decontamination formula: see Table 1 for details.

[0116] (ii) Decontamination process: the same as that of Example 1.

[0117] (III) Effect evaluation: See Table 2 for details.

[0118] Example 9

[0119] (I) Decontamination formula: see Table 1 for details.

[0120] (ii) Decontamination process: the same as that of Example 1.

[0121] (III) Effect evaluation: See Table 2 for details.

[0122] Example 10

[0123] (I) Decontamination formula: see Table 1 for details.

[0124] (ii) Decontamination process: the same as that of Example 1.

[0125] (III) Effect evaluation: See Table 2 for details.

[0126] Embodiment 11

[0127] (I) Decontamination formula: see Table 1 for details.

[0128] (ii) Decontamination process: the same as that of Example 1.

[0129] (III) Effect evaluation: See Table 2 for details.

[0130] Example 12

[0131] (I) Decontamination formula: see Table 1 for details.

[0132] (ii) Decontamination process: the same as that of Example 1.

[0133] (III) Effect evaluation: See Table 2 for details.

[0134] Table 1 Decontamination formula of the embodiment and comparative example

[0135]

[0136]

[0137]

[0138]

[0139] Table 2 Evaluation of decontamination effects of the embodiments and comparative examples

[0140]

[0141] It can be seen from Table 2 that the decontamination formulas and decontamination processes of Examples 1 to 12 all achieved a certain decontamination effect. Among them, Example 1 is the optimal decontamination formula of the present application. The decontamination factor of Example 1 is the highest, the corrosion depth is less than 0.2 μm, and the organic matter degradation rate of the waste liquid after decontamination exceeds 98%. In theory, the higher the decontamination factor, the more effectively the intensity of radiation to the staff can be reduced. The morphology of the sample before and after decontamination provided in Example 1 of the present application is as follows: Figure 1 and Figure 2 As shown, it can be seen that the surface of the stainless steel is smooth as a whole after decontamination, without obvious intergranular corrosion, which proves that the decontamination formula and decontamination process of Example 1 cause extremely low damage to the stainless steel substrate to be decontaminated, can ensure the safety of the system to be decontaminated, and is suitable for in-service decontamination of nuclear facilities.

[0142] Example 2: Changing the concentration of potassium permanganate in the PP liquid improves the oxidizability of the decontamination formula. Its decontamination factor is similar to that of Example 1, but the corrosion depth is greatly deepened. This shows that increasing the concentration of potassium permanganate does not improve the decontamination effect. This is because the potassium permanganate concentration in Example 1 can ensure the decontamination effect, and the radioactive nuclides have been basically removed. On the contrary, the increase in potassium permanganate brings a negative effect, that is, it strengthens the corrosion of the substrate, which is not conducive to the reuse of subsequent equipment.

[0143] Example 3: Changing the concentrations of polyaspartic acid, oxalic acid and sodium diaminodisuccinate in the DIP solution has the same effect as Example 2, but also brings negative effects.

[0144] Example 4: The concentration of potassium permanganate in the PP liquid is changed to reduce the oxidizing property of the decontamination formula. From the results of Example 4, the decontamination factor is significantly reduced.

[0145] Example 5: The concentration of oxalic acid and the like in the DIP solution is reduced. From the results of Example 5, it can be seen that the decontamination factor is significantly reduced.

[0146] Example 6: The reaction temperature of the PP solution and the DIP solution in the decontamination method is changed, thereby resulting in a significant decrease in the decontamination factor.

[0147] Example 7: Changing the reaction temperature of the inorganic oxidation of the decontamination waste liquid in the decontamination method results in a significant decrease in the degradation rate of organic matter in the decontamination waste liquid.

[0148] Example 8: Reducing the components of DIP, resulting in a significant decrease in the decontamination factor.

[0149] Example 9: Reducing the components of DIP, resulting in a significant decrease in the decontamination factor.

[0150] Example 10: Reducing the components of DIP, resulting in a significant decrease in the decontamination factor.

[0151] Example 11: The PP liquid was changed to nitric acid instead of potassium permanganate. Although the decontamination factor did not change much, dilute nitric acid was highly corrosive, which led to a significant increase in the corrosion depth, which was not conducive to in-service decontamination.

[0152] Example 12: The components of the DIP solution were changed to malic acid, ascorbic acid, and disodium ethylenediaminetetraacetate. The decontamination factor decreased to a certain extent, and the degradation rate of organic matter in the waste liquid decreased significantly after decontamination.

[0153] It is easy for those skilled in the art to understand that, under the premise of no conflict, the above-mentioned advantageous methods can be freely combined and superimposed. The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application. The above are only preferred implementation methods of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and variations can be made without departing from the technical principles of the present application, and these improvements and variations should also be regarded as the protection scope of the present application.

Claims

1. A degradable decontamination formulation for a nuclear reactor, characterized in that: include: Oxidation cleaning solution, the oxidant accounts for 0.1% to 2% by mass, and the rest is deionized water; The degradable reducing complex liquid comprises at least two of a scale inhibitor, a reducing agent and a complexing agent. Calculated by mass fraction, the scale inhibitor accounts for 0-1%, the reducing agent accounts for 0-2%, the complexing agent accounts for 0-1.5%, and the rest is deionized water.

2. The degradable decontamination formulation according to claim 1, characterized in that: The oxidant is one or more of potassium persulfate, ammonium cerium nitrate, hydrogen peroxide, nitric acid and potassium permanganate; The scale inhibitor is one or more of malic acid, acrylic acid, organic phosphonic acid and polyaspartic acid; The reducing agent is one or more of oxalic acid, ferrous nitrate, sodium thiosulfate, ascorbic acid and hydrazine; The complexing agent is one or more of succinic acid, sodium diaminodisuccinate, nitrilotriacetic acid, and disodium ethylenediaminetetraacetate.

3. The degradable decontamination formulation according to claim 1, characterized in that: The decontamination formula comprises: An oxidative cleaning solution, wherein the oxidant in the oxidative cleaning solution is potassium permanganate, with a mass fraction of 0.4% to 0.6%, and the rest is deionized water; The degradable reducing complex liquid comprises a scale inhibitor of polyaspartic acid with a mass fraction of 0.16% to 0.24%, a reducing agent of oxalic acid with a mass fraction of 0.4% to 0.6%, a complexing agent of sodium diaminodisuccinate with a mass fraction of 0.4% to 0.6%, and the rest of the liquid is deionized water.

4. The degradable decontamination formulation according to claim 3, characterized in that: The degradable decontamination formula is used to carry out in-service decontamination of a high-temperature and high-pressure test loop of a light water research reactor, and the decontamination factor reaches more than 100; the corrosion depth of stainless steel parts is 0.18-0.22 μm; and the organic matter degradation rate of the decontaminated radioactive waste liquid reaches more than 98% after inorganic treatment.

5. A degradable decontamination method for a nuclear reactor, characterized in that: include: Oxidation treatment, injecting the oxidation decontamination liquid described in any one of claims 1 to 4 into a high-temperature and high-pressure test loop of a light water research reactor, and discharging the oxidation treatment waste liquid after a cyclic reaction; The first deionized water rinse is to rinse the light water research reactor high temperature and high pressure test circuit after the oxidation treatment with deionized water; Reduction and complexation treatment, injecting the degradable reduction and complexation liquid described in any one of claims 1 to 4 into the high-temperature and high-pressure test loop of the light water research reactor after the first deionized water rinse, and discharging the reduction and complexation treatment waste liquid after the cyclic reaction; A second deionized water rinse, using deionized water to rinse the light water research reactor high temperature and high pressure test circuit after the reduction and complexation treatment; Inorganic treatment of decontaminated radioactive waste liquid.

6. The degradable decontamination method according to claim 5, characterized in that: In the oxidation treatment, the cycle reaction temperature is 80° C. to 95° C., and the cycle time is 4 h to 10 h.

7. The degradable decontamination method according to claim 5, characterized in that: The first deionized water rinsing is performed at room temperature for 1 hour to 2 hours.

8. The degradable decontamination method according to claim 5, characterized in that: In the reduction complexation treatment, the cycle reaction temperature is 80° C. to 95° C., and the cycle time is 4 h to 10 h.

9. The degradable decontamination method according to claim 5, characterized in that: The second deionized water rinsing is performed at room temperature until the pH of the rinsing solution is 6 to 9 and the specific resistivity is greater than 5×10 5 After Ω·m, stop rinsing.

10. The degradable decontamination method according to claim 5, characterized in that: The inorganic treatment of the decontaminated radioactive waste liquid includes: Inorganic treatment of the oxidation waste liquid and the reduction complexation waste liquid, adjusting the pH of the oxidation waste liquid to 1.5-2.5, and then mixing it with the reduction complexation waste liquid to obtain a mixed decontamination waste liquid, adding hydrogen peroxide to the mixed decontamination waste liquid, and reacting at 40°C-60°C for 2h-4h; The pH value of the oxidation waste liquid is adjusted to 1.5-2.5 by using nitric acid with a mass concentration of 0.5%-1%; and the mass concentration of hydrogen peroxide in the mixed decontamination waste liquid is controlled to be 1.5-2.5%.

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