Method and device for measuring lithium content of lithium type cation exchange resin

Abstract

The invention relates to the field of nuclear chemistry, in particular to a method and a device for measuring the lithium content of lithium type cation exchange resin. The method comprises the following steps: carrying out anion and cation resin separation on nuclear-grade mixed bed resin; a sodium chloride solution is adopted as a leacheate, and salt liquid leaching is conducted on the nuclear-grade lithium type cation resin; and measuring the lithium content in the eluent by adopting ion chromatography, wherein a sodium chloride solution is used as a matrix configuration standard during measurement. According to the invention, the precision and accuracy of measurement are improved, errors are reduced, and accurate measurement of the lithium content in the lithium type cation exchange resin is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of nuclear chemistry, in particular to a method and device for measuring lithium content of lithium type cation exchange resin. BACKGROUND

[0002] The primary loop chemical and volume control system of a pressurized water reactor nuclear power plant uses nuclear grade resin to purify the water quality of the reactor coolant. In order to avoid the absorption of lithium ions in the primary loop coolant after the nuclear grade resin is filled and operated, which causes the decrease of lithium concentration in the primary loop, the lithium type cation resin of the nuclear power plant is generally a nuclear grade lithium saturated cation resin, and the lithium transformation rate is > 99%.

[0003] Through investigation, it is found that the current industry standard "Method for Determining Transformation Rate of Nuclear Grade Lithium Type Cation Exchange Resin" (DL / T2294-2021) measures the lithium content as follows: using an excess of a monovalent acid to elute lithium ions from the lithium type cation exchange resin, and then measuring the lithium content by atomic absorption method. The measurement precision and accuracy of this method is about 1%, and the error is about 3%. At the same time, this method assumes that only lithium type groups and hydrogen type groups exist in the resin when calculating the lithium transformation rate, while in the actual application of the lithium type resin in the nuclear power plant, there may be other cations in addition to lithium ions and hydrogen ions, which causes a systematic error in principle. Therefore, it cannot be directly used for calculating the lithium transformation rate of the nuclear grade lithium type resin. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a method and device for measuring the lithium content of lithium type cation exchange resin, which improves the measurement precision and accuracy, reduces the error, and realizes accurate measurement of the lithium content in lithium type cation exchange resin.

[0005] The present application provides a method for measuring the lithium content of lithium type cation exchange resin, comprising the following steps:

[0006] Step 1: separate the anion and cation resins of the nuclear grade mixed bed resin;

[0007] Step 2: use sodium chloride solution as the leaching solution to leach the nuclear grade lithium type cation resin with salt solution;

[0008] Step 3: measure the lithium content in the eluent by ion chromatography, and use sodium chloride solution as the matrix to configure the standard during measurement.

[0009] In one embodiment of the present application, step 1 specifically comprises:

[0010] Step 1-1: load the mixed resin into a separation column, and pass ultrapure water from the bottom to backwash the mixed resin;

[0011] Step 1-2: stop water inflow, and let it stand to allow the mixed resin to naturally stratify;

[0012] Step 1-3: Extract the resin above the layer interface and the resin below the layer interface respectively, and realize the separation of the negative resin and the positive resin.

[0013] In one embodiment of the present application, when the ultrapure water is introduced, the flow rate of the ultrapure water is 20-50 mL / min, and the backwashing time is 60-80 minutes.

[0014] In one embodiment of the present application, in the step 2, the concentration of the sodium chloride solution is 1-2 mol / L.

[0015] In one embodiment of the present application, in the step 3, the eluate after the elution is collected,

[0016] The 1-2 mol / L sodium chloride solution is used as a standard solution for the matrix,

[0017] The ion chromatography is used to draw a curve to measure the lithium content in the eluate.

[0018] In one embodiment of the present application, during the elution, the volume of the elution solution for 1-2 grams of the positive resin is not less than 100 mL.

[0019] The present application provides a device for measuring the lithium content of lithium type cation exchange resin, which comprises a resin separation column, the lower part of which is provided with a liquid inlet and a first resin outlet, the liquid inlet is connected to an ultrapure water storage tank, and the first resin outlet is connected to a resin exchange column.

[0020] A separatory funnel is connected to the top of the resin exchange column at the lower part, and the top of the separatory funnel is connected to the ultrapure water storage tank and an elution solution storage container.

[0021] The resin exchange column is connected to an elution solution receiving pool at the lower part.

[0022] In one embodiment of the present application, the bottom of the resin exchange column is provided with a sand core glass plate.

[0023] In one embodiment of the present application, the components are connected by using soluble polytetrafluoroethylene pipes.

[0024] In one embodiment of the present application, the bottom of the separatory funnel is provided with a piston for controlling the flow rate of the liquid.

[0025] Compared with the prior art, the method and device for measuring the lithium content of lithium type cation exchange resin of the application improve the precision and accuracy of measurement, reduce the error, and realize accurate measurement of the lithium content in lithium type cation exchange resin. The measurement precision of the method is at least 0.30%, the recovery rate is at least 103%, and the error is about 1%, which makes up for the deficiency of the method for measuring the lithium content in nuclear grade lithium type cation resin, realizes quality supervision of nuclear grade lithium type cation resin in nuclear power plants, and ensures the stability of the water chemical control of the primary loop of the nuclear power plant. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The mechanism schematic diagram of the device for measuring the lithium content of lithium type cation exchange resin is shown in the figure.

[0027] In the figure: 1, ultra-pure water storage tank; 2, resin separation column; 3, eluent storage container; 4, separating funnel; 5, resin exchange column; 6, sand core glass plate; 7, eluent receiving pool. DETAILED DESCRIPTION

[0028] In order to further understand the application, the embodiments of the application are described below in combination with examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the application, and are not limitations of the application.

[0029] The embodiments of the application disclose a method for measuring the lithium content of lithium type cation exchange resin, comprising the following steps:

[0030] Step 1: separate the anion resin and the cation resin of the nuclear grade mixed bed resin;

[0031] In this step, the separation is performed by using the hydraulic layering method based on the density difference between the anion resin and the cation resin. Generally, the density of the anion resin is smaller than that of the cation resin, and the anion resin floats up and the cation resin sinks down during backwashing.

[0032] Specifically, it comprises:

[0033] Step 1-1: load the mixed resin into the separation column, and introduce ultra-pure water from the bottom to backwash the mixed resin;

[0034] When the ultra-pure water is introduced, the flow rate of the ultra-pure water is 20-50 mL / min, and the backwashing time is 60-80 minutes.

[0035] Step 1-2: stop water feeding, and let the mixed resin naturally stratify;

[0036] Step 1-3: respectively extract the resin above the layer interface and the resin below the layer interface to realize separation of the anion resin and the cation resin.

[0037] Step 2: using sodium chloride solution as eluent, salt solution is used to elute the nuclear grade lithium type cation exchange resin;

[0038] The concentration of the sodium chloride solution is 1-2 mol / L. Using the sodium chloride solution with the concentration as the eluent can ensure the efficient separation of lithium ions in the nuclear grade lithium type resin.

[0039] When eluting, the volume of the eluent for 1-2 grams of cation exchange resin is not less than 100 mL.

[0040] When eluting, the elution speed and elution time are precisely controlled to improve the operability and operation accuracy, and the complete elution of lithium can be achieved.

[0041] When adding the sodium chloride eluent to the resin exchange column for resin elution, the valve opening is controlled to make the flow rate 3-4 ml / min during the elution process, and the liquid level of the resin column is observed to drop 1 cm in 1 min, and then it is fixed. The elution time is determined by the time when the eluent passes through the resin exchange column. Step 3: using ion chromatography to measure the lithium content in the eluent, and using sodium chloride solution as the matrix to configure the standard.

[0042] Specifically includes:

[0043] collecting the eluent after elution,

[0044] using 1-2 mol / L sodium chloride solution as the matrix to configure the standard solution,

[0045] using ion chromatography to draw a curve and then measuring the lithium content in the eluent.

[0046] The ion chromatography method is used to measure the lithium content in the resin eluent, and the measurement precision is high and the stability is good.

[0047] By the matrix matching method, the influence of the matrix on the measurement result of the lithium content in the eluent is reduced, and the accuracy of the analysis is ensured.

[0048] The embodiments of the application disclose a measuring device for the lithium content of lithium type cation exchange resin.

[0049] The measuring device for the lithium content of lithium type cation exchange resin comprises a resin separation column 2, which is provided with a liquid inlet and a first resin outlet at the lower part, the liquid inlet is connected with an ultrapure water storage tank 1, and the first resin outlet is connected with a resin exchange column 5;

[0050] A separatory funnel 4 is connected with the top of the resin exchange column 5 at the lower part; the top of the separatory funnel 4 is connected with the ultrapure water storage tank 1 and an eluent storage container 3; and the bottom of the separatory funnel 4 is provided with a piston for controlling the liquid flow rate;

[0051] Resin exchange column 5, lower part connected to eluate receiving pool 7.

[0052] The bottom of the resin exchange column 5 is provided with a sand core glass plate 6.

[0053] The components are connected by soluble polytetrafluoroethylene pipes to ensure that the entire system is resistant to acid and alkali and has low elution characteristics.

[0054] In order to further understand the present application, the measuring method and device for lithium content of lithium type cation exchange resin provided by the present application will be described in detail below in combination with examples, and the protection scope of the present application is not limited by the following examples.

[0055] Example 1

[0056] The mixed resin is loaded into the resin separation column 2, and ultrapure water is introduced from the bottom using the ultrapure water storage tank 1, with a flow rate of 30 mL / min and a backwashing time of 60 minutes; after stopping the water inlet, the resin naturally stratifies due to the density difference, with the upper layer being the negative resin and the lower layer being the positive resin; the upper and lower layer resins at the layer interface are extracted respectively to realize siphon separation. The separated positive resin is loaded into the resin exchange column 5.

[0057] The eluate storage container 3 is poured into the separatory funnel 4, the piston of the separatory funnel 4 is adjusted to control the flow rate, and the positive resin in the resin exchange column 5 is eluted with salt solution, and the sand core glass plate 6 is used to prevent the resin from flowing out of the exchange column. After elution, ultrapure water is input into the separatory funnel 4 and the resin exchange column 5 through the ultrapure water storage tank 1 to flush the separatory funnel 4 and the resin exchange column 5, ensuring that the lithium ions are completely flushed, and the resin eluate is transferred to the eluate receiving pool 7. It is confirmed through experiments that about 1-2g of resin is eluted with 1 mol / L sodium chloride eluent, and the elution endpoint is reached after 100ml of eluent is used to elute the resin.

[0058] According to the sodium chloride concentration in the eluate in the resin exchange column 5, 1 mol / L sodium chloride is used as the matrix to prepare a standard, and the lithium content in the eluate is measured after drawing a curve using ion chromatography (IC). The relative standard deviation RSD of the lithium content measured by ion chromatography (IC) can be as low as 0.30%, the recovery rate can be as low as 103%, and the measurement error is about 1%. The ion chromatography (IC) method for measuring lithium content has good precision and high accuracy.

[0059] The recovery rate refers to the recovery rate of lithium. The recovery rate test is based on the principle of mass conservation, by adding a known amount of analyte to the measurement matrix, and performing the same treatment and analysis as the real sample, the accuracy of the method is evaluated by calculating the ratio of the measured value to the added value. Whether the recovery rate is within an acceptable range is used to determine whether the analysis method is reliable.

[0060] The calculation formula of the recovery rate is:

[0061] Recovery (%) = (Measured concentration - Original concentration of the blank sample) / Added concentration x 100%. The explanation in the formula is as follows:

[0062] Measured concentration: The total concentration obtained after analyzing the sample to which the standard was added.

[0063] Original concentration: The concentration obtained after analyzing the blank sample to which the standard was not added.

[0064] Added concentration: The concentration of the standard artificially added to the sample.

[0065] The acceptable range of recovery rate depends on the type of analysis method, the nature of the analyte, the complexity of the sample matrix, and the relevant regulations / standards. Generally, the acceptable level of recovery rate for trace / microanalysis is 80%-120%. Due to acceptable measurement error, the calculated value of recovery rate can be greater than 100%, and the closer to 100% indicates that the measurement method is more accurate.

[0066] The above description of the embodiments is only used to help understand the method of the present application and its core idea. It should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

[0067] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for measuring the lithium content of a lithium-type cation exchange resin, characterized in that, Includes the following steps: Step 1: Separate the anion and cation resins from the nuclear-grade mixed bed resin; Step 2: Use sodium chloride solution as the rinsing solution to rinse the nuclear-grade lithium cation resin with salt solution; Step 3: The lithium content in the eluent was measured by ion chromatography, using sodium chloride solution as the matrix preparation standard.

2. The method for measuring the lithium content of lithium-type cation exchange resin according to claim 1, characterized in that, Step 1 specifically includes: Step 1-1: Pack the mixed resin into the separation column and backwash the mixed resin by introducing ultrapure water from the bottom. Steps 1-2: Stop the water supply and let it stand to allow the mixed resin to naturally separate into layers; Steps 1-3: Extract the resin above the interface and the resin below the interface respectively to separate the anion resin and the cation resin.

3. The method for measuring the lithium content of lithium-type cation exchange resin according to claim 2, characterized in that, When introducing ultrapure water, the flow rate of ultrapure water is 20-50 mL / min, and the backwashing time is 60-80 minutes.

4. The method for measuring the lithium content of lithium-type cation exchange resin according to claim 1, characterized in that, In step 2, the concentration of the sodium chloride solution is 1-2 mol / L.

5. The method for measuring the lithium content of lithium-type cation exchange resin according to claim 4, characterized in that, In step 3, the eluent after rinsing is collected. A 1–2 mol / L sodium chloride solution was used as the matrix to prepare the standard solution. The lithium content in the eluent was measured after plotting the curve using ion chromatography.

6. The method for measuring the lithium content of lithium-type cation exchange resin according to claim 1, characterized in that, During the rinsing process, the volume of the rinsing solution for 1-2 grams of cation exchange resin shall not be less than 100 mL.

7. A device for measuring the lithium content of a lithium-type cation exchange resin, characterized in that, It includes a resin separation column, which has an inlet and a first resin outlet at the bottom. The inlet is connected to an ultrapure water storage tank and the first resin outlet is connected to a resin exchange column. The separatory funnel is connected at its lower part to the top of the resin exchange column; the top of the separatory funnel is connected to the ultrapure water storage tank and the eluent storage container. The resin exchange column is connected to the eluent receiving tank at the bottom.

8. The measuring device for lithium content of lithium-type cation exchange resin according to claim 7, characterized in that, The bottom of the resin exchange column is provided with a frit-core glass plate.

9. The measuring device for lithium content of lithium-type cation exchange resin according to claim 7, characterized in that, The components are connected by soluble polytetrafluoroethylene pipes.

10. The measuring device for lithium content of lithium-type cation exchange resin according to claim 7, characterized in that, A piston is installed at the bottom of the separating funnel to control the liquid flow rate.

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