A method and device for titrating boric acid solution in the primary loop system of a nuclear power plant

Abstract

The present invention provides a boric acid solution titration method and device in the primary loop system of a nuclear power plant. By comparing the ratio of the electrode potential difference to the titrant volume difference of the mixed solution of the boric acid solution to be titrated and the titrant within a set time with a preset threshold, the titrant with the corresponding concentration is replaced according to the comparison result. When the concentration of the boric acid solution to be titrated changes, the concentration of the titrant can be adjusted in a timely manner, fully considering the problem that a single-concentration titrant cannot meet the titration accuracy when the concentration of the boric acid solution to be measured changes, and improving the accuracy of the entire titration process of the boric acid solution.

Description

Technical Field

[0001] The present invention belongs to the technical field related to nuclear reactor safety, and particularly relates to a method and device for titrating boric acid solution in the primary loop system of a nuclear power plant. Background Art

[0002] The statements in this part merely provide background technical information related to the present invention and do not necessarily constitute prior art.

[0003] Isotopes of boron 10 10B has good neutron absorption. Its compound boric acid is a most commonly used soluble neutron poison, which is dissolved in the primary coolant of a pressurized water reactor to control and regulate the reactivity of the reactor. In order for reactor operators to timely understand and master the boron concentration in the coolant and ensure the safe and stable operation of the unit, an on-line boron concentration titrator is set in the primary loop and other related systems of a pressurized water reactor nuclear power plant to monitor the boron concentration under various conditions. However, in the process of on-line determination of boric acid in a nuclear power plant, there is a situation where the boric acid concentration changes greatly but the titrant concentration does not change accordingly. In the titration process, using the same concentration titrant for different boric acid concentrations will result in too long titration time for high-concentration boric acid and inaccurate determination results for low-concentration boric acid. The existing on-line determination technology of boric acid concentration in nuclear power plants does not consider the large change in boric acid concentration during the titration process. Summary of the Invention

[0004] To overcome the deficiencies of the above-mentioned prior art, the present invention provides a method and device for titrating boric acid solution in the primary loop system of a nuclear power plant. When the concentration of the boric acid solution to be titrated changes greatly, the titrant concentration is changed for titration to improve the accuracy of titration.

[0005] To achieve the above object, the first aspect of the present invention provides a method for titrating boric acid solution in the primary loop system of a nuclear power plant, including:

[0006] Obtaining a boric acid solution sample to be titrated and titrating and mixing the boric acid solution sample with a titrant to obtain a mixed solution;

[0007] During the titration process, comparing the ratio of the electrode potential difference to the titrant volume difference of the mixed solution within a set time with a preset threshold;

[0008] According to the comparison result, replacing the titrant with the corresponding concentration for titration.

[0009] The second aspect of the present invention provides a device for titrating boric acid solution in the primary loop system of a nuclear power plant, including: a titration device, a first injection pump connected to the inlet of the titration device for injecting a boric acid solution sample to be titrated, and a plurality of injection pumps connected to the inlet of the titration device for injecting titrants with different concentrations respectively.

[0010] The above one or more technical solutions have the following beneficial effects:

[0011] In the present invention, fully considering the problem that a titrant with a single concentration cannot meet the titration accuracy when the concentration of the boric acid solution to be measured changes, by comparing the ratio of the difference in the electrode potential of the mixed solution of the boric acid solution to be titrated and the titrant to the difference in the volume of the titrant within a set time with a preset threshold, and replacing the titrant with the corresponding concentration according to the comparison result, when the concentration of the boric acid solution to be titrated changes, the concentration of the titrant can be adjusted in a timely manner, improving the accuracy of the entire titration process of the boric acid solution.

[0012] Advantages of additional aspects of the present invention will be partly given in the following description, partly will become obvious from the following description, or will be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings forming a part of this specification are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0014] Figure 1 It is a flowchart of a method for titrating boric acid solution in a primary loop system of a nuclear power plant in Embodiment 1 of the present invention;

[0015] Figure 2 It is a relationship curve between the potential of the mixed solution and the volume of the titrant in Embodiment 1 of the present invention;

[0016] Figure 3 It is a schematic diagram of a device for titrating boric acid solution in a primary loop system of a nuclear power plant in Embodiment 2 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0018] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention.

[0019] Without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0020] Embodiment 1

[0021] As Figure 1 shown, this embodiment discloses a method for titrating boric acid solution in a primary loop system of a nuclear power plant, including:

[0022] Obtain a sample of boric acid solution to be titrated and titrate and mix the boric acid solution sample with a titrant to obtain a mixed solution;

[0023] During the titration process, compare the ratio of the electrode potential difference to the titrant volume difference of the mixed solution within a set time with a preset threshold value;

[0024] According to the comparison result, replace the titrant with the corresponding concentration for titration.

[0025] In the current boric acid titration process in nuclear power plants, the influence of the titrant concentration on the titration result and titration efficiency is rarely considered under the condition of continuously changing boric acid concentration. In this embodiment, different concentration titrants are switched according to the change of the boric acid solution concentration to further improve the accuracy of the titration result.

[0026] In this embodiment, for an unknown concentration of boric acid solution, first set a pre-titration with a titrant of medium concentration, and judge whether to use a high or medium or low concentration titrant for the initial titration based on the pre-titration result.

[0027] Specifically, high concentration (6 g / L ≤ x < 18 g / L), medium concentration (1 g / L ≤ x < 6 g / L), low concentration (0.1 g / L ≤ x < 1 g / L).

[0028] Such as Figure 2 As shown, after determining the initial titration concentration, perform the titration process. During the titration process, by judging the range of ΔE / ΔV, switch different concentration titrants, specifically as follows:

[0029] If the ratio of the absolute value of the electrode potential difference of the mixed solution to the titrant volume difference within a set time is not greater than the first preset threshold value, replace it with a titrant in the first concentration range.

[0030] If the ratio of the absolute value of the electrode potential difference of the mixed solution to the titrant volume difference within a set time is greater than the first preset threshold value and not greater than the second preset threshold value, replace it with a titrant in the second concentration range.

[0031] If the ratio of the absolute value of the electrode potential difference of the mixed solution to the titrant volume difference within a set time is greater than the second preset threshold value, replace it with a titrant in the third concentration range.

[0032] Among them, the first concentration range (high concentration) is greater than the second concentration range (medium concentration), and the second concentration range (medium concentration) is greater than the third concentration range (low concentration).

[0033] Specifically,

[0034]

[0035]

[0036]

[0037] Among them, ΔE and ΔV are the difference in electrode potential and the difference in titrant volume of the mixed solution within the set time, respectively. The unit of ΔE is mV, the unit of ΔV is mL, the value range of A is 1 - 5, and the value range of B is 6 - 10.

[0038] In this embodiment, the adjustment process during the titration is as follows:

[0039] The boric acid solution sample to be measured is pre-titrated with a medium-concentration titrant to select the initial titrant concentration through the pre-titration. Among them, the pre-titrant concentration here does not need to be selected, meaning that after pre-titration with any currently existing concentration (high or medium or low) titrant, after calculating ΔE / ΔV based on the current pre-titration result, a more suitable titrant concentration is selected by judging the threshold.

[0040] If the concentration of the initial titrant is a high-concentration titrant, it is replaced with a high-concentration titrant for titration. When |ΔE| / ΔV ≤ A / ΔV, that is, the first preset threshold, the high-concentration titrant continues to be used for titration; when A / ΔV, that is, the first preset threshold < |ΔE| / ΔV ≤ B / ΔV, that is, the second preset threshold, a medium-concentration titrant is used for titration; when B / ΔV, that is, the second preset threshold < |ΔE| / ΔV, it is replaced with a low-concentration titrant for titration until the titration equivalence point appears, and the entire titration process ends. Among them, the value range of A is 1 - 5, and the value range of B is 6 - 10.

[0041] In this embodiment, taking the potassium hydroxide standard solution as the titrant as an example, potentiometric titration is carried out with the boric acid solution:

[0042] 1. When titrating high-concentration boric acid (1 mol / L) with a single-concentration titrant and a self-adjusting concentration titrant, the time t (s) is as shown in the following table:

[0043]

[0044] Obviously, the titration time of the single-concentration titrant is longer than that of the self-adjusting system. The self-adjusting system determines a more suitable concentration for titration after pre-titration, making the titration process more efficient.

[0045] When titrating low-concentration boric acid (0.01 mol / L) with a single-concentration titrant and a self-adjusting concentration titrant, the titration results (mol / L) are as shown in the following table:

[0046]

[0047]

[0048] As can be seen from the table, the titration result with self-adjusting titrant concentration is more accurate, and its accuracy and parallelism are better than those of titration with a single titrant concentration.

[0049] Example Two

[0050] As Figure 3 shown, the purpose of this embodiment is to provide a boric acid solution titration device in the primary loop system of a nuclear power plant, including: a titration device, a first injection pump connected to the inlet of the titration device for injecting a boric acid solution sample to be titrated, and a plurality of injection pumps connected to the inlet of the titration device for injecting titrants with different concentrations respectively.

[0051] It further includes a second injection pump connected to the inlet of the titration device, and the second injection pump is used to inject other reagents except the titrant in the titration test.

[0052] Among them, the titration device includes a titration cup and a magnetic stirrer.

[0053] The process of titration using the boric acid solution titration device in this embodiment is as follows:

[0054] The boric acid solution sample to be titrated enters the first injection pump P1 through the first valve V1 and is injected into the titration cup through the first injection pump P1. Other reagents required in the titration experiment enter the second injection pump P2 through the second valve V2 and are injected into the titration cup by the second injection pump P2; throughout the process, continuous stirring is carried out by the magnetic stirrer to ensure full reaction of the solution in the titration cup;

[0055] The titrant with medium concentration is injected into the titration cup by the fourth injection pump P4 to carry out the pre-titration process, and the initial titrant concentration is selected through the pre-titration;

[0056] If the initial titrant is a high concentration, the fourth injection pump P4 is switched to the third injection pump P3, and the high-concentration titrant is titrated by the third injection pump P3. When |ΔE| / ΔV ≤ A / ΔV, the high-concentration titrant is continuously injected by the third injection pump P3 for titration; when A / ΔV < |ΔE| / ΔV ≤ B / ΔV, the third injection pump P3 is switched to the fourth injection pump P4, and the medium-concentration titrant is titrated by the fourth injection pump P4; when B / ΔV < |ΔE| / ΔV, the fourth injection pump P4 is switched to the fifth injection pump P5, and the low-concentration titrant is titrated by the fifth injection pump P5 until the titration equivalence point appears, then the whole

[0057] One titration process ends. Among them, ΔE and ΔV are the electrode potential difference and titrant volume difference of the mixed solution within the set time respectively. The unit of ΔE is mV, and the unit of ΔV is mL. The value range of A is 1 to 5, and the value range of B is 6 to 10.

[0058] It should be noted that the measurement of the electrode potential is obtained by inserting the electrode (electrochemical sensor) into the solution to obtain the potential value.

[0059] Although the specific implementation manners of the present invention are described above in conjunction with the accompanying drawings, it is not a limitation on the protection scope of the present invention. Those skilled in the art should understand that various modifications or deformations that can be made without creative efforts on the basis of the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for titrating boric acid solution in the primary loop system of a nuclear power plant, characterized in that, Including: Obtaining a boric acid solution sample to be titrated and titrating and mixing the boric acid solution sample with a titrant to obtain a mixed solution; During the titration process, comparing the ratio of the electrode potential difference to the titrant volume difference of the mixed solution within a set time with a preset threshold; According to the comparison result, replacing the titrant with a corresponding concentration for titration; For a boric acid solution with an unknown concentration, first set a pre-titration using a titrant with an intermediate concentration, and judge whether to use a high or medium or low concentration titrant for the initial titration based on the pre-titration result; Specifically, the high concentration is 6 g / L ≤ x < 18 g / L, the medium concentration is 1 g / L ≤ x < 6 g / L, and the low concentration is 0.1 g / L ≤ x < 1 g / L; after determining the initial titration concentration, perform the titration process. During the titration process, by judging the range of ΔE / ΔV, switch the titrant with different concentrations, specifically as follows: If the ratio of the absolute value of the electrode potential difference of the mixed solution to the titrant volume difference within a set time is not greater than the first preset threshold, replace it with a titrant in the first concentration range; If the ratio of the absolute value of the electrode potential difference of the mixed solution to the titrant volume difference within a set time is greater than the first preset threshold and not greater than the second preset threshold, replace it with a titrant in the second concentration range; If the ratio of the absolute value of the electrode potential difference of the mixed solution to the titrant volume difference within a set time is greater than the second preset threshold, replace it with a titrant in the third concentration range; Wherein, the high concentration in the first concentration range is greater than the medium concentration in the second concentration range, and the medium concentration in the second concentration range is greater than the low concentration in the third concentration range; Specifically, （1） （2） （3） Wherein, ΔE and ΔV are respectively the electrode potential difference and the titrant volume difference of the mixed solution within a set time, the unit of ΔE is mV, the unit of ΔV is mL, the value range of A is 1 to 5, and the value range of B is 6 to 10.

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