Plutonium reduction reverse extraction method

Abstract

The invention belongs to the technical field of spent fuel post-treatment, and particularly relates to a plutonium reduction and reverse extraction method. The method comprises the following steps: controlling the initial concentration of plutonium in 2AF according to the flow rate and flow rate ratio and the concentration multiple of plutonium; when the 2AF feed liquid passes through the oxidation column, the liquid flow is controlled to be 160-200L / h; when the 2AF feed liquid passes through the degassing column, the liquid flow is controlled to be 160-200L / h; the bottom material liquid in the 2AF feeding tank runs thoroughly every two or three batches, and the waste kerosene in the oil removal tank passes through the pulse extraction column at one time to run. The method can achieve the purpose of reducing the content of nitrous acid in the plutonium secondary cycle organic phase, avoids accumulation of nitrite in the 2AF feed liquid and the organic phase, reduces the heat effect of plutonium accumulation, and is suitable for long-term continuous operation of the system. Through multiple repeated experiments, the stable operation of the system can be realized, and the column temperature and hydraulic parameters of the 2BX column are stable.

Description

Technical Field

[0001] The present application belongs to the technical field of spent fuel post-processing, and specifically relates to a plutonium reduction stripping method. Background Art

[0002] In the Purex process, the plutonium secondary reduction stripping column (2BX column) in the plutonium purification cycle was found to have abnormal column temperature rise, high interface and high organic phase density during commissioning. After analysis, it was found that the nitrites entrained in the organic phase in the feed liquid were difficult to remove, resulting in the nitrites reacting with the reducing agent and supporting reducing agent in the 2BX column, causing the 2BX column to operate unstably, and even causing the loss of plutonium in severe cases.

[0003] The source of nitrite in the organic phase is part of the nitrous acid carried by the kerosene that is refluxed regularly and the oxidation adjustment in the plutonium secondary circulation raw material solution (1BP feed solution). Generally, nitrous gas is used to adjust the trivalent plutonium in the 1BP feed solution to a tetravalent plutonium. After the adjustment, the nitrite and nitrous gas in the solution need to be removed to a certain level. At present, the project uses a degassing column, supplemented by heating measures, to carry out the nitrous acid in the solution in the form of nitrogen oxides.

[0004] However, 1BP liquid, 2BP liquid and reflux washing acid usually carry a certain amount of organic phase, which makes it difficult to remove the nitrite carried in the organic phase. In addition, plutonium, as a radioactive nuclide, releases a large amount of heat when undergoing radioactive decay. The higher the plutonium concentration, the more neutrons are produced by the decay, and the greater the heat generated. A large amount of heat will further intensify the autocatalytic reaction of hydroxylamine. Summary of the invention

[0005] The purpose of the present application is to provide a plutonium reduction stripping method to solve the problem in the prior art that nitrite entrained in an organic phase is difficult to remove.

[0006] Technical solution to achieve the purpose of this application:

[0007] The present application provides a plutonium reduction stripping method, the method comprising:

[0008] Control the initial concentration of plutonium in 2AF according to the flow rate ratio and the plutonium enrichment multiple;

[0009] When the 2AF feed liquid passes through the oxidation column, the liquid flow rate is controlled at 160-200 L / h;

[0010] When the 2AF liquid passes through the degassing column, the liquid flow rate is controlled at 160-200 L / h;

[0011] The bottom liquid in the 2AF feed tank is completely run every two or three batches, and the waste kerosene in the de-oiling tank is run through the pulse extraction column at one time.

[0012] Optionally, the method further includes:

[0013] When the 2AF feed liquid passes through the oxidation column, the NO x The ratio to the 2AF reduction value is 1.8 to 2.2.

[0014] Optionally, the method further includes:

[0015] When the 2AF liquid passes through the degassing column, the temperature is 50±5℃.

[0016] Optionally, the method further includes:

[0017] When the 2AF liquid passes through the degassing column, the gas flow rate control adjustment range is 2 to 4 m 3 / h.

[0018] Optionally, the bottom liquid in the 2AF feed tank is completely run every two or three batches, specifically including:

[0019] When the liquid level of 2AF feed tank reaches 200mm, the flow rate of 2AF is controlled to 45±2.25L / h and the flow rate of 2AX is controlled to 20±1L / h.

[0020] Optionally, the bottom liquid in the 2AF feed tank is completely run every two or three batches, specifically including:

[0021] When the liquid level in the constant liquid level pre-tank of the first-stage empty extraction of the 2AF feed rises, or the liquid level in the separation tank at the organic phase outlet of the 2AX column rises above the preset threshold, the flow rate of 2AF is controlled to 55L / h and the flow rate of 2AX is controlled to 10L / h.

[0022] Optionally, the method further includes:

[0023] AF flow rate is controlled to 55L / h, 2AX flow rate is controlled to 10L / h.

[0024] The beneficial technical effects of this application are:

[0025] A plutonium reduction stripping method provided in an embodiment of the present application includes: controlling the initial concentration of plutonium in 2AF according to the flow ratio and the concentration multiple of plutonium; when the 2AF feed liquid passes through the oxidation column, controlling the liquid flow rate at 160-200L / h; when the 2AF feed liquid passes through the degassing column, controlling the liquid flow rate at 160-200L / h; the bottom feed liquid in the 2AF feed tank is run thoroughly every two or three batches, and the waste kerosene in the deoiling tank is run through the pulse extraction column at one time. This method can achieve the purpose of reducing the nitrous acid content in the organic phase of the second cycle of plutonium, avoid the accumulation of nitrite in the 2AF feed liquid and the organic phase, reduce the thermal effect of plutonium accumulation, and is suitable for long-term continuous operation of the system. After repeated experiments, the system can be operated stably, and the column temperature and hydraulic parameters of the 2BX column are stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic flow chart of a plutonium reduction stripping method provided in an embodiment of the present application;

[0027] Figure 2 A model diagram of a 2AF oxidation price adjustment process in a plutonium reduction stripping method provided in an embodiment of the present application;

[0028] Figure 3 A model diagram of the 2AF operation process in a plutonium reduction stripping method provided in an embodiment of the present application;

[0029] Figure 4 A model diagram of the organic phase operation process in a plutonium reduction stripping method provided in an embodiment of the present application.

[0030] In the figure:

[0031] 1-2AF price adjustment feed tank; 2- oxidation column; 3-2AF intermediate tank; 4- degassing column; 5-2AF receiving tank; 6-2AF feed liquid; 7-2AF acid adjustment tank; 8-2AF feed tank; 9-2AX column; 10-2AF; 11-2AX feed liquid; 12- pulse extraction column; 13- oil removal tank; 14- kerosene storage tank; 15- distilled kerosene; 16- circulating kerosene. DETAILED DESCRIPTION

[0032] In order to make those skilled in the art better understand the present application, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the embodiments described below are only a part of the embodiments of the present application, not all. Based on the embodiments recorded in the present application, all other embodiments obtained by those skilled in the art without paying creative work are within the scope of protection of the present application.

[0033] See also Figure 1 , which is a schematic flow chart of a plutonium reduction stripping method provided in an embodiment of the present application.

[0034] Combination Figure 2-4 , a plutonium reduction stripping method provided in an embodiment of the present application comprises:

[0035] Step S101: controlling the initial concentration of plutonium in the 2AF feed liquid according to the flow rate ratio and the plutonium concentration multiple;

[0036] Step S102: When the 2AF feed liquid passes through the oxidation column, the liquid flow rate is controlled at 160-200 L / h;

[0037] Step S103: When the 2AF liquid passes through the degassing column, the liquid flow rate is controlled at 160-200 L / h;

[0038] Step S104: The remaining bottom liquid in the 2AF feed tank is run through every two or three batches, and the waste kerosene in the de-oiling tank is run through the pulse extraction column once.

[0039] It should be noted that the main reaction equation for the reaction of nitrogen oxides with water to produce nitrous acid is shown in formula (1):

[0040] 2NO2+H2O→HNO2+HNO3 (1)

[0041] Nitrous acid can react with the reducing agent hydroxylamine nitrate and the supporting reducing agent hydrazine nitrate in the 2BX column. When the reaction occurs, a large amount of heat and gas will be generated. Hydroxylamine nitrate will also be autocatalytically oxidized by nitrous acid under the action of nitric acid, so that hydroxylamine is continuously consumed. The reaction formula is shown in formula (2):

[0042] NH3OH + +2HNO3+2HNO2→5HNO2+H3O + (2)

[0043] This often seriously affects the stability of the system operation, leading to inaccurate measurement of the system interface, overflow of the water phase entrained in the organic phase, and even the loss of plutonium in severe cases. Therefore, it is necessary to finely control the feed gas and liquid flow rates and flow ratios of the oxidation column (2).

[0044] Considering the operation of the system, in the embodiment of the present application, the feed gas flow rate of the oxidation column (2) needs to be controlled at 160-200 L / h. The 2AF reduction value of the system can be measured by sampling. It is known that NO x The content percentage of the gas under standard conditions is 22.4 mol / L, NO x The reference value of the consumption ratio of the 2AF reduction value is 2; therefore, NO x The gas consumption can be controlled by referring to formula (3).

[0045] In this method, it is known that F is stable in control, h can be measured by sampling, C is a constant, and by selecting different multiples of n, V can be effectively controlled. It is stipulated that n is selected as a multiple of 1.8 to 2.2;

[0046] V=F×h×n×22.4 / C / 1000 (3)

[0047] Where V is NO x The feed gas flow rate, F is the feed gas flow rate of 2AF liquid, h is the reduction value concentration of 2AF liquid, and n is NO x Ratio of 2AF reduction value, C is NO x The percentage of content.

[0048] To remove nitrous acid, the current engineering application is a degassing column (4), in which AS3 compressed air is introduced into the column to purge the nitrous acid-containing liquid, and a jacket water bath heating measure is used to carry out the nitrous acid contained in the solution in the form of nitrogen oxides by means of water bath heating and air bubbling. In the embodiment of the present application, the liquid flow rate of the degassing column (4) is specified to be 160-200 L / h, the temperature is 50±5°C, and the original range of air flow control adjustment is 2-7 m 3 / h, choose 2~4m 3 / h.

[0049] The above method can reduce the nitrite content in the aqueous phase to below the limit value, but the 2AF feed liquid will be entrained with an organic phase, and part of the unremoved nitrite will be entrained into the organic phase. The nitrite in the organic phase is difficult to remove by water bath heating and air bubbling, and often ends up interacting with the reducing agent in the 2BX column, which has an adverse effect on the stable operation of the system. In order to remove the influence of the organic phase entrained in the 2AF feed liquid entering the system, the embodiment of the present application stipulates that the 2AF feed liquid batches are controlled to run thoroughly; the bottom feed liquid in the 2AF feed tank is run thoroughly every two or three batches.

[0050] The kerosene in the system adopts a long-term self-circulation operation mode and a periodic one-time complete reflux. During the self-circulation operation, the kerosene is in contact with the aqueous phase liquid for a long time, which often leads to the accumulation of some nitrous acid in the kerosene. During the one-time complete reflux, some nitrous acid entrained in the kerosene will also interact with the reducing agent in the 2BX column, which will have an adverse effect on the operation of the system.

[0051] The waste kerosene in the de-oiling tank (13) carries nitrous acid, and the operation of the circulating kerosene (16) causes the accumulation of nitrous acid. The kerosene operation mode is regulated, and the waste kerosene in the de-oiling tank is run through the pulse extraction column (12) once and for all without the circulation operation.

[0052] The accumulation of plutonium will release a large amount of heat, which will in turn intensify the autocatalytic reaction of hydroxylamine. By specifying the initial concentration of plutonium in the 2AF feed liquid, the rising trend of plutonium concentration in the plutonium reduction stripping process is controlled, and the heat release is further controlled. For example, according to the flow rate ratio and the plutonium concentration multiple, the initial concentration of plutonium in 2AF is controlled at A±0.5g / L.

[0053] In some possible implementations of the embodiments of the present application, the method may further include:

[0054] When the 2AF feed liquid passes through the oxidation column, the NO x The ratio to the 2AF reduction value is 1.8 to 2.2.

[0055] In some possible implementations of the embodiments of the present application, the method may further include:

[0056] When the 2AF liquid passes through the degassing column, the temperature is 50±5℃.

[0057] In one example, the method further includes:

[0058] When the 2AF liquid passes through the degassing column, the gas flow rate control adjustment range is 2 to 4 m 3 / h.

[0059] In some possible implementations of the embodiments of the present application, the bottom liquid in the 2AF feed tank is completely removed after every two or three batches of operation, which may specifically include:

[0060] When the liquid level of 2AF feed tank reaches 200mm, the flow rate of 2AF is controlled to 45±2.25L / h and the flow rate of 2AX is controlled to 20±1L / h.

[0061] In some possible implementations of the embodiments of the present application, the bottom liquid in the 2AF feed tank is completely removed after every two or three batches of operation, which may specifically include:

[0062] When the liquid level in the constant liquid level pre-tank of the first-stage empty extraction of the 2AF feed rises, or the liquid level in the separation tank at the organic phase outlet of the 2AX column rises above the preset threshold, the flow rate of 2AF is controlled to 55L / h and the flow rate of 2AX is controlled to 10L / h.

[0063] In some possible implementations of the embodiments of the present application, the method further includes:

[0064] AF flow rate is controlled to 55L / h, 2AX flow rate is controlled to 10L / h.

[0065] The embodiment of the present application finds a method for stabilizing the plutonium reduction stripping operation by re-regulating the operation of the oxidation column (2), the operation of the degassing column (4), the thorough operation of 2AF, the kerosene operation mode, and the initial plutonium concentration of 2AF, which is conducive to the stable operation of the subsequent system. It can achieve the purpose of reducing the nitrous acid content in the organic phase of the plutonium second cycle, avoid the accumulation of nitrite in the 2AF feed liquid and the organic phase, reduce the thermal effect of plutonium accumulation, and is suitable for long-term continuous operation of the system. After repeated experiments, the system can be operated stably, and the column temperature and hydraulic parameters of the 2BX column are stable.

[0066] Example 1

[0067] This embodiment provides a method for stabilizing the plutonium reduction stripping operation. The method for stabilizing the plutonium reduction stripping operation includes running 2AF through an oxidation column, running a degassing column, running 2AF thoroughly, passing waste kerosene once, and specifying the initial concentration of plutonium in 2AF. The device is as shown in the attached Figure 1 , Attachment Figure 2 , Attachment Figure 3 shown.

[0068] The method comprises the following steps:

[0069] When the S1 and 2AF feed liquids pass through the oxidation column, the liquid flow rate is controlled at 160-200 L / h, and n is selected as 1.8;

[0070] When the S2 and 2AF liquid passes through the degassing column, the liquid flow rate is controlled at 160-200 L / h and the temperature is 50

[0071] ±5℃, air flow rate select 3m 3 / h;

[0072] S3, 2AF run completely, the bottom liquid in 2AF feed tank runs completely every 2 batches;

[0073] S4, in case 1, the liquid level of 2AF feed tank is 200mm, the flow rate of 2AF is controlled to 45±2.25L / h, and the flow rate of 2AX is controlled to 20±1L / h;

[0074] S5, the waste kerosene in the oil removal tank is run through the pulse extraction column once;

[0075] S6. Control the initial concentration of plutonium in 2AF at A±0.5 g / L.

[0076] The nitrite content in the 2AF feed tank was sampled and analyzed, and the nitrite content was effectively controlled at 3-5 mg / L. The operation of the 2BX column was observed. The stable operation was manifested by the column temperature being maintained at 45±5°C, and the interface, column weight and density fluctuating stably. Situation 2 did not occur, and it was determined that there was no organic phase entrainment. The above means enabled the stable operation of plutonium reduction stripping to be achieved.

[0077] In this embodiment, the goal of stable operation of plutonium reduction stripping is achieved, the column temperature of the 2BX column is stable, and the interface, column weight and density fluctuate stably.

[0078] Example 2

[0079] This embodiment provides a method for stabilizing the plutonium reduction stripping operation. The method for stabilizing the plutonium reduction stripping operation includes running 2AF through an oxidation column, running through a degassing column, running 2AF thoroughly, passing waste kerosene through once, and specifying the initial concentration of plutonium in 2AF. The device is as shown in the attached Figure 1 , Attachment Figure 2 , Attachment Figure 3 shown.

[0080] The method comprises the following steps:

[0081] When the S1 and 2AF feed liquids pass through the oxidation column, the liquid flow rate is controlled at 160-200 L / h, and n is selected as 2.2;

[0082] When S2 and 2AF liquid passes through the degassing column, the liquid flow rate is controlled at 160-200L / h and the gas flow rate is 3±1m 3 / h, temperature 50±5℃;

[0083] S3 and 2AF are fully operated, and the bottom liquid in the 2AF feed tank is fully operated every 3 batches;

[0084] S4, in case 1, the liquid level of 2AF feed tank is 200mm, the flow rate of 2AF is controlled to 45±2.25L / h, and the flow rate of 2AX is controlled to 20±1L / h;

[0085] The liquid level in the constant liquid level pre-tank of the first-stage empty extraction of S5 and 2AF feed increased, and then the liquid level in the separation tank of the organic phase outlet of the 2AX column increased significantly;

[0086] S6, in case 2, the flow rate of 2AF is controlled to 55±5.5L / h, and the flow rate of 2AX is controlled to 10L / h;

[0087] S7, the waste kerosene in the oil removal tank is run through the pulse extraction column once;

[0088] S8. Control the initial concentration of plutonium in 2AF at A±0.5 g / L.

[0089] Situation 2 occurs, it can be judged that 2AF runs to the organic phase, and the nitrite content in the 2AF feed tank is sampled and analyzed. It is found that the content is slightly increased compared with Example 1. It can be determined that when n is increased, the gas flow rate of the degassing column also needs to be appropriately increased. The entrainment of nitrite in the organic phase can be judged. The operation of the 2BX column fluctuates slightly, but is generally stable. The column temperature is maintained at 45±5°C, and the interface, column weight, and density fluctuate stably.

[0090] In this embodiment, the plutonium reduction stripping is stably operated, the column temperature of the 2BX column is stable, and the interface, column weight and density fluctuate stably.

[0091] Example 3

[0092] This embodiment provides a method for stabilizing the plutonium reduction stripping operation. The method for stabilizing the plutonium reduction stripping operation includes running 2AF through an oxidation column, running through a degassing column, running 2AF thoroughly, passing waste kerosene through once, and specifying the initial concentration of plutonium in 2AF. The device is as shown in the attached Figure 1 , Attachment Figure 2 , Attachment Figure 3 shown.

[0093] The method comprises the following steps:

[0094] When the S1 and 2AF feed liquids pass through the oxidation column, the liquid flow rate is controlled at 160-200 L / h, and n is selected as 2.2;

[0095] When S2 and 2AF liquid passes through the degassing column, the liquid flow rate is controlled at 160-200L / h and the gas flow rate is 7±1m 3 / h, temperature 50±5℃;

[0096] S3, there was slight carryover in the washing acid, and the plutonium concentration was slightly increased when sampling and analysis were performed;

[0097] S4, 2AF run completely, the bottom liquid in 2AF feed tank runs completely every 2 batches;

[0098] S5, the waste kerosene in the oil removal tank is run through the pulse extraction column once;

[0099] S6. Control the initial concentration of plutonium in 2AF at A±0.5 g / L.

[0100] The change in the degassing column gas flow rate causes the washing acid liquid level to rise, which shows that if the degassing column gas flow rate is increased too high, serious phase entrainment will occur. Therefore, it is recommended that the degassing column gas flow rate be controlled within the method range. The nitrite content in the 2AF feed tank is sampled and analyzed, and the nitrite content is effectively controlled at 3-5 mg / L. The operation of the 2BX column is observed, the column temperature is maintained at 45±5℃, the interface, column weight and density fluctuate stably, and the operation is stable.

[0101] In this embodiment, stable plutonium reduction stripping operation is achieved, the column temperature of the 2BX column is stable, and the interface, column weight and density fluctuate stably.

[0102] The present application is described in detail above in conjunction with the accompanying drawings and embodiments, but the present application is not limited to the above embodiments, and various changes can be made within the knowledge of ordinary technicians in the field without departing from the purpose of the present application. Any content not described in detail in the present application can adopt the existing technology.

Claims

1. A plutonium reduction stripping method, characterized in that: The method comprises: Control the initial concentration of plutonium in 2AF according to the flow rate ratio and the plutonium enrichment multiple; When the 2AF feed liquid passes through the oxidation column, the liquid flow rate is controlled at 160-200 L / h; When the 2AF liquid passes through the degassing column, the liquid flow rate is controlled at 160-200 L / h; The bottom liquid in the 2AF feed tank is completely run every two or three batches, and the waste kerosene in the de-oiling tank is run through the pulse extraction column at one time.

2. The plutonium reduction stripping method according to claim 1, characterized in that: The method further comprises: When the 2AF feed liquid passes through the oxidation column, the NO x The ratio to the 2AF reduction value is 1.8 to 2.

2.

3. The plutonium reduction stripping method according to claim 1, characterized in that: The method further comprises: When the 2AF liquid passes through the degassing column, the temperature is 50±5℃.

4. The plutonium reduction stripping method according to claim 3, characterized in that: The method further comprises: When the 2AF liquid passes through the degassing column, the gas flow rate control adjustment range is 2 to 4 m 3 / h.

5. The plutonium reduction stripping method according to claim 1, characterized in that: The bottom liquid in the 2AF feed tank is completely removed after two or three batches of operation, specifically including: When the liquid level of 2AF feed tank reaches 200mm, the flow rate of 2AF is controlled to 45±2.25L / h and the flow rate of 2AX is controlled to 20±1L / h.

6. The plutonium reduction stripping method according to claim 1, characterized in that: The bottom liquid in the 2AF feed tank is completely removed after two or three batches of operation, specifically including: When the liquid level in the constant liquid level pre-tank of the first-stage empty extraction of the 2AF feed rises, or the liquid level in the separation tank at the organic phase outlet of the 2AX column rises above the preset threshold, the flow rate of 2AF is controlled to 55L / h and the flow rate of 2AX is controlled to 10L / h.

7. The plutonium reduction stripping method according to claim 1, characterized in that: The method further comprises: AF flow rate is controlled to 55L / h, 2AX flow rate is controlled to 10L / h.

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