阅读说明：本技术 反应堆一回路溶解氢含量测定方法 (Method for measuring content of dissolved hydrogen in reactor primary loop ) 是由 周志梦 郑德超 刘晓军 韦荣伟 赵红杰 黄岩 叶伟 彭木林 吕腾 于 2021-01-04 设计创作，主要内容包括：本发明公开了一种反应堆一回路溶解氢含量测定方法,包括：S1、分别将流量计和压力表安装在便携式氢分析仪的流通池入口和出口上,标定；S2、将便携式氢分析仪连接在反应堆一回路中,将便携式氢分析仪的供气钢头连接氮气供应系统；S3、反应堆一回路的冷却剂通过入口进入流通池,通过出口返回反应堆一回路；S4、便携式氢分析仪对冷却剂进行测定,获得冷却剂中氢气和氦气的总含量；S5、将氢气和氦气的总含量减去预先通过气液相分离器测得的冷却剂中的氦气含量,获得冷却剂中氢气的含量。本发明实现对反应堆一回路冷却剂中溶解氢含量的在线连续测定,提高溶解氢含量测量的准确度、稳定性和灵敏度,减少溶解氢分析时的人员受辐照剂量,提高工作效率。(The invention discloses a method for measuring the content of dissolved hydrogen in a reactor primary loop, which comprises the following steps: s1, respectively installing a flowmeter and a pressure gauge on an inlet and an outlet of a flow cell of the portable hydrogen analyzer, and calibrating; s2, connecting the portable hydrogen analyzer in a reactor loop, and connecting a gas supply steel head of the portable hydrogen analyzer with a nitrogen supply system; s3, enabling the coolant in the reactor loop to enter the flow cell through the inlet and return to the reactor loop through the outlet; s4, measuring the coolant by a portable hydrogen analyzer to obtain the total content of hydrogen and helium in the coolant; and S5, subtracting the helium content in the coolant measured by the gas-liquid phase separator in advance from the total content of the hydrogen and the helium to obtain the content of the hydrogen in the coolant. The invention realizes the on-line continuous measurement of the content of the dissolved hydrogen in the coolant of the primary loop of the reactor, improves the accuracy, stability and sensitivity of the measurement of the content of the dissolved hydrogen, reduces the irradiation dose of personnel during the analysis of the dissolved hydrogen and improves the working efficiency.)

1. A method for measuring the content of dissolved hydrogen in a primary loop of a reactor is characterized by comprising the following steps:

s1, respectively installing a flowmeter and a pressure gauge on an inlet and an outlet of a flow cell of the portable hydrogen analyzer, and calibrating the portable hydrogen analyzer;

s2, connecting the portable hydrogen analyzer in a reactor loop, and connecting a gas supply steel head of the portable hydrogen analyzer with a nitrogen supply system of a nuclear island;

s3, the coolant of the reactor loop enters the flow-through cell through the inlet and returns to the reactor loop through the outlet;

s4, the portable hydrogen analyzer measures the accessed coolant to obtain the total content of hydrogen and helium in the coolant;

and S5, subtracting the helium content in the coolant measured by the gas-liquid phase separator in advance from the total content of the hydrogen and the helium in the coolant to obtain the content of the hydrogen in the coolant.

2. The method according to claim 1, wherein in step S2, the outlet of the flow cell is connected to a chemical volume control system of the reactor primary loop via a quick connector.

3. The method for determining the content of dissolved hydrogen in a primary loop of a reactor according to claim 1, wherein in step S2, one end of the pressure reducing valve is connected to the gas supply steel head of the portable hydrogen analyzer through a hose, and the other end of the pressure reducing valve is connected to the nitrogen supply system of the nuclear island through a quick connector.

4. The method according to claim 3, wherein in step S4, the portable hydrogen analyzer is purged with nitrogen by supplying nitrogen gas through a nitrogen gas supply system.

5. The method for determining the dissolved hydrogen content in a reactor loop according to claim 1, wherein in step S3, the coolant in the flow cell flows out to a volume control tank of the chemical and volumetric control system through the outlet and then returns to the reactor loop.

6. The method as set forth in claim 5, wherein in step S3, the outlet of the flow cell is connected to the control box of the chemical and volumetric control system via a quick connector.

7. The method for determining the primary dissolved hydrogen content of a reactor according to claim 1, wherein in step S3, the flow rate of the coolant entering the flow cell is controlled to be not less than 200 mL/min.

8. The method for determining the primary dissolved hydrogen content of a reactor according to any one of claims 1 to 7, wherein the algorithm of step S5 is obtained by:

the portable hydrogen analyzer uses a thermal conductivity detector, and the measurement result is represented by the following formula (1):

[H₂]_M=[H₂]_T+k×[He]+c （1）

wherein [ H ]₂]_MHydrogen content, [ H ] measured by a portable hydrogen analyzer₂]_TAnd [ He ]]Respectively measuring the content of hydrogen and helium gas by a gas-liquid phase separator, wherein k is a helium compensation coefficient, and c is a system error;

under the same conditions of selective permeability of the electrode semipermeable membrane of the portable hydrogen analyzer to hydrogen and helium, k is expressed as: k = λ H₂A/lambda He; wherein, λ H₂Is the thermal conductivity of hydrogen, λ He is the thermal conductivity of helium; at 25 ℃, k = 0.88;

according to the formula (1), the actual values of k and c are calculated according to the dissolved hydrogen content of the primary loop coolant with different helium concentrations, the value of k is 1.0, c is not more than 1.23mL/kg, the portable hydrogen analyzer has the same response to hydrogen and helium, and the system error is small, so that the content of hydrogen in the coolant is obtained by subtracting the helium content in the coolant measured by the gas-liquid phase separator from the total content of hydrogen and helium in the coolant measured by the portable hydrogen analyzer.

Technical Field

The invention relates to the technical field of reactor water quality analysis, in particular to a method for measuring the content of dissolved hydrogen in a reactor primary loop.

Background

The dissolved hydrogen content of the primary coolant must be controlled within limits as dictated by nuclear power plant water chemistry specifications during operation of the pressurized water reactor. Under the power operation and cold shutdown modes, the appropriate hydrogen content can effectively inhibit the radiation decomposition of primary loop water, prevent the hydrogen embrittlement effect of nuclear fuel zirconium alloy and prevent the corrosion of primary loop pressure boundary materials. The accurate measurement of the concentration of the dissolved hydrogen in the primary loop coolant of the reactor is a precondition and a necessary condition for tracking and adjusting the hydrogen concentration, and is closely related to the safe operation of a nuclear power plant.

The measurement method of the dissolved hydrogen in the primary loop of the pressurized water reactor mainly comprises three methods: the method has the advantages that the gas-liquid phase separator chromatography by means of a decanter and a gas chromatograph is accurate in measurement and traceable, but the operation is complex; an online instrument based on a principle that a metal palladium electrode adsorbs hydrogen has the advantages that the instrument electrode needs frequent regeneration and flushing, and response is slow, so that the reliability is extremely low; thermal conductivity hydrogen analyzers are portable and online, wherein online is rare, and portable hydrogen analyzers are applied to most nuclear power plants. Although documents relate to the use mode, common problems and solving measures of the portable hydrogen analyzer, the influence of various water chemistry conditions of the primary circuit coolant on measurement is lack of detailed research, so that the portable hydrogen analyzer has the problems of complex operation, coolant waste, low accuracy of measurement results and the like in the actual use process.

Water chemistry conditions that affect the measurements mainly include: sample water flow through the portable hydrogen analyzer; measuring back pressure of the portable hydrogen analyzer; interference of various interfering gases in the coolant on dissolved hydrogen detection; hydrogen analyzer system error.

The low accuracy of the traditional method is mainly reflected in that the interference of interference gas in primary circuit coolant on the detection of dissolved hydrogen is not considered, and the interference of helium on the measurement result of the dissolved hydrogen is not evaluated and compensated.

The traditional method is complex in operation and mainly comprises the following steps: in the traditional method, a purging nitrogen source used by the hydrogen analyzer is an air cylinder of the hydrogen analyzer, the air cylinder has a small volume and needs to be periodically inflated by an external high-pressure nitrogen steel cylinder, the inflation process is complex, and the high-pressure nitrogen has safety risk in the use process; in the traditional method, only pure hydrogen gas is used for calibrating the portable hydrogen analyzer, and the influence of other gases on a hydrogen measurement result is not considered, so that an external high-pressure hydrogen steel cylinder is required to be used during pure hydrogen gas calibration, and the operation is dangerous and complicated.

The coolant waste is mainly due to: when the traditional method uses a hydrogen analyzer, the sample water of the primary loop coolant of the reactor flowing through the hydrogen analyzer is directly discharged to the air and then is discharged into a wastewater treatment system as chemical wastewater, and the direct recycling of the primary loop coolant is not realized.

Disclosure of Invention

The invention aims to provide a method for measuring the dissolved hydrogen content in a reactor primary loop, which realizes on-line continuous measurement.

The technical scheme adopted by the invention for solving the technical problems is as follows: the method for measuring the content of the dissolved hydrogen in the primary loop of the reactor comprises the following steps:

s1, respectively installing a flowmeter and a pressure gauge on an inlet and an outlet of a flow cell of the portable hydrogen analyzer, and calibrating the portable hydrogen analyzer;

s2, connecting the portable hydrogen analyzer in a reactor loop, and connecting a gas supply steel head of the portable hydrogen analyzer with a nitrogen supply system of a nuclear island;

s3, the coolant of the reactor loop enters the flow-through cell through the inlet and returns to the reactor loop through the outlet;

s4, the portable hydrogen analyzer measures the accessed coolant to obtain the total content of hydrogen and helium in the coolant;

and S5, subtracting the helium content in the coolant measured by the gas-liquid phase separator in advance from the total content of the hydrogen and the helium in the coolant to obtain the content of the hydrogen in the coolant.

Preferably, in step S2, the outlet of the flow cell is connected to the chemical volume control system of the reactor loop via a quick connector.

Preferably, in step S2, one end of the pressure reducing valve is connected to the gas supply steel head of the portable hydrogen analyzer through a hose, and the other end is connected to the nitrogen supply system of the nuclear island through a quick connector.

Preferably, in step S4, during the measurement, nitrogen is provided through a nitrogen supply system to purge the portable hydrogen analyzer with nitrogen.

Preferably, in step S3, the coolant in the flow-through cell flows out to the control box of the chemical and volumetric control system through the outlet and then returns to the reactor loop.

Preferably, in step S3, the outlet of the flow cell is connected to the control box of the chemical and volumetric control system via a quick connector.

Preferably, in step S3, the flow rate of the coolant entering the flow-through cell is controlled to be more than or equal to 200 mL/min.

Preferably, the algorithm of step S5 is obtained by:

the portable hydrogen analyzer uses a thermal conductivity detector, and the measurement result is represented by the following formula (1):

[H₂]_M＝[H₂]_T+k×[He]+c (1)

wherein [ H ]₂]_MHydrogen content, [ H ] measured by a portable hydrogen analyzer₂]_TAnd [ He ]]Respectively measuring the content of hydrogen and helium gas by a gas-liquid phase separator, wherein k is a helium compensation coefficient, and c is a system error;

under the same conditions of selective permeability of the electrode semipermeable membrane of the portable hydrogen analyzer to hydrogen and helium, k is expressed as: k ═ λ H2/λ_He(ii) a Where λ H2 is the thermal conductivity of hydrogen, λ_HeIs the thermal conductivity of helium; k is 0.88 at 25 ℃;

according to the formula (1), the actual values of k and c are calculated according to the dissolved hydrogen content of the primary loop coolant with different helium concentrations, the value of k is 1.0, c is not more than 1.23mL/kg, the portable hydrogen analyzer has the same response to hydrogen and helium, and the system error is small, so that the content of hydrogen in the coolant is obtained by subtracting the helium content in the coolant measured by the gas-liquid phase separator from the total content of hydrogen and helium in the coolant measured by the portable hydrogen analyzer.

The method for measuring the dissolved hydrogen content in the primary loop of the reactor realizes the on-line continuous measurement of the dissolved hydrogen content in the coolant of the primary loop of the reactor by adopting the portable hydrogen analyzer, and the coolant returns to the primary loop after measurement to realize recycling; the accuracy, stability and sensitivity of the measurement of the content of the dissolved hydrogen in the primary loop coolant are improved, the irradiation dose of personnel during the analysis of the dissolved hydrogen is reduced, the working efficiency is improved, and chemical analysis personnel are protected.

Drawings

The invention will be further described with reference to the accompanying drawings and examples, in which:

FIG. 1 is a flow chart of a method for determining the dissolved hydrogen content in a reactor primary loop according to the present invention;

fig. 2 is a schematic view of the structure of the portable hydrogen analyzer in the present invention.

Detailed Description

For a more clear understanding of the technical features, objects and effects of the present invention, embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

With reference to fig. 1 and 2, a method for determining the content of dissolved hydrogen in a reactor primary loop according to an embodiment of the present invention includes the following steps:

s1, the flow meter 20 is attached to the inlet or outlet of the flow cell of the portable hydrogen analyzer 10.

A flow meter 20 for monitoring the flow of coolant into the flow cell; preferably, the flow meter 20 is installed at the inlet of the flow cell.

A pressure gauge 30 is attached to the outlet of the flow cell for monitoring the pressure.

After the flowmeter 20 and the pressure gauge 30 are mounted, the portable hydrogen analyzer 10 is calibrated. The portable hydrogen analyzer can be calibrated by a pure hydrogen gas calibration method, and can also be directly calibrated manually by using the measurement result of dissolved hydrogen of the gas-liquid phase separator.

S2, connecting the portable hydrogen analyzer 10 to a reactor primary circuit, and connecting the gas supply steel head of the portable hydrogen analyzer 10 to the nitrogen supply system (RAZ) of the nuclear island.

Wherein, according to the hydrogen content in the coolant to be measured, the portable hydrogen analyzer 10 is connected with a corresponding passage in a reactor primary circuit so as to connect the coolant into a flow cell. The outlet of the flow cell is connected with the chemical volume control system of the reactor primary loop through the quick-connection connector 40, so that the measured coolant is discharged to the chemical volume control system from the outlet of the flow cell, and is discharged back to the reactor primary loop for recycling, and waste is avoided.

The pressure gauge 30 is located on the connection line between the quick connector 40 and the outlet of the flow cell, and monitors the back pressure of the portable hydrogen analyzer 10 to maintain a stable state.

The gas supply steel head of the portable hydrogen analyzer 10 is connected to a nitrogen gas supply system (RAZ) through a pressure reducing valve 50. Further, one end of the pressure reducing valve 50 is connected to the gas supply steel head of the portable hydrogen analyzer 10 through a hose 60, and the other end is connected to the nitrogen supply system of the nuclear island through a quick connector 70. The nitrogen supply system continuously supplies nitrogen to the portable hydrogen analyzer 10, and the complex operation of periodically inflating the cylinder of the portable hydrogen analyzer 10 through an external high-pressure nitrogen steel cylinder is omitted.

S3, the coolant of the reactor loop enters the flow cell of the portable hydrogen analyzer 10 through the inlet and returns to the reactor loop through the outlet.

Because the sample water flow has an important influence on the measurement result of the dissolved hydrogen, according to the test result, the flow influence characteristic of the portable hydrogen analyzer 10 is as follows: when the flow of the sample water is less than 200mL/min, the measurement result is greatly increased along with the increase of the flow of the sample water; when the flow is increased to 200-500 mL/min, the measurement result is stable. Therefore, in order to reduce the influence of flow variation on the measurement of dissolved hydrogen, the sample water flow rate should not be lower than 200mL/min when the portable hydrogen analyzer 10 is used.

According to the above conclusion, the flow rate of the coolant entering the flow cell is controlled to be more than or equal to 200mL/min in combination with the flow meter 20 on the inlet of the flow cell.

In addition, the hydrogen solubility is related to the pressure, and according to the test results, the back pressure of the portable hydrogen analyzer 10 slightly affects the measurement results of the dissolved hydrogen, and the higher the pressure is, the larger the measurement value is, so that the measurement process needs to keep the back pressure as stable as possible.

The outlet of the flow cell of the portable hydrogen analyzer 10 is connected to the control box of the chemical and volumetric control system via a quick connector 40, and the coolant discharged from the outlet of the flow cell first enters the control box of the chemical and volumetric control system and then returns to the reactor loop.

S4, the portable hydrogen analyzer 10 measures the accessed coolant to obtain the total content of hydrogen and helium in the coolant.

And S5, subtracting the helium content in the coolant measured by the gas-liquid phase separator in advance from the total content of the hydrogen and the helium in the coolant to obtain the content of the hydrogen in the coolant (namely the content of the dissolved hydrogen in the coolant).

Wherein the coolant measured by the gas-liquid phase separator and the coolant entering the portable hydrogen analyzer 10 are the coolants in the same path in the reactor primary circuit.

In general, portable hydrogen analyzers are subject to drying during useThe influence of interfering gases. Calculating the thermal conductivity (W.m.K) of the reactor primary loop common gas at 25 ℃ by using a gas thermal conductivity calculation formula¹) Are respectively (H)₂，0.17064)、(He，0.15016)、(N₂，0.02475)、(O₂0.02571), (Ar,0.01795), (Xe, 0.00568), (Kr, 0.00946). Wherein O is₂Ar, Xe and Kr are contained in a reactor loop in a small amount and have extremely low thermal conductivity, N₂Acting as background gas for the hydrogen analyzer, they have negligible effect on the dissolved hydrogen measurement. However, the thermal conductivity and molecular diameter of helium are close to those of hydrogen, and the presence of a large amount of helium affects the measurement result. Thus, helium gas can be evaluated and removed from interfering with dissolved hydrogen detection by means of dissolved hydrogen and helium measurements from a gas-liquid phase separator, as follows:

the portable hydrogen analyzer uses a thermal conductivity detector, and the measurement result can be represented by the following formula (1):

[H₂]_M＝[H₂]_T+k×[He]+c (1)

wherein [ H ]₂]_MHydrogen content (i.e., dissolved hydrogen content) measured for a portable hydrogen analyzer, [ H ]₂]_TAnd [ He ]]The contents of hydrogen and helium measured by the gas-liquid phase separator are respectively, k is a helium compensation coefficient, and c is a system error.

Under the same conditions of selective permeability of the electrode semipermeable membrane of the portable hydrogen analyzer to hydrogen and helium, k can be expressed as: k ═ λ H2/λ_He(ii) a Where λ H2 is the thermal conductivity of hydrogen, λ_HeIs the thermal conductivity of helium. At 25 ℃, k is 0.88.

From equation (1), the actual values of k and c were calculated based on the dissolved hydrogen content of the primary coolant at different helium concentrations, and the results are shown in Table 1. As can be seen from Table 1, the value of k is about 1.0, c is not greater than 1.23mL/kg, i.e., the portable hydrogen analyzer has substantially the same response to hydrogen and helium, and the system error is small, so that the content of hydrogen in the coolant can be obtained by subtracting the content of helium in the coolant measured by the gas-liquid phase separator from the total content of hydrogen and helium in the coolant measured by the portable hydrogen analyzer.

TABLE 1. compensation coefficient for dissolved helium and systematic error

In addition, the portable hydrogen analyzer 10 used in the present invention should be periodically calibrated for continuously maintaining the measurement accuracy of the portable hydrogen analyzer 10; quality control checks are performed on the portable hydrogen analyzer 10 for assessing the stability and accuracy of the analysis process of the analyzer.

The portable hydrogen analyzer can be calibrated by a pure hydrogen gas calibration method, and when the hydrogen content in the coolant of the primary loop of the reactor is higher, the measurement result of the dissolved hydrogen of the gas-liquid phase separator can be directly used for manual calibration. Because the external high-pressure hydrogen cylinder is needed to be used during the calibration of the pure hydrogen gas, the operation is dangerous and complex, the manual calibration process using the analysis result of the gas-liquid phase separator is simple, and the use risk of the hydrogen is avoided.

The dissolved hydrogen content is measured by a gas-liquid phase separator at regular intervals as the quality control inspection basis of the portable hydrogen analyzer. Helium content analysis, periodic calibration and quality control inspection can be carried out simultaneously.

By measuring the content of dissolved hydrogen in the primary loop coolant of the reactor by the measuring method, the measuring working efficiency is obviously improved, and the irradiation dose of an analyst is greatly reduced; when the concentration of the dissolved hydrogen in the coolant is 1.50-32.10 mL/kg, the measurement error is not more than 1.37 mL/kg. After single calibration, the portable hydrogen analyzer can be used for at least 2 months; the accuracy, stability and sensitivity are all superior to DH1021 hydrogen meter.

When the method is applied to the reactor during normal power operation and overhaul start-stop periods, the measured value of the dissolved hydrogen is more accurate, sensitive and reliable, and the method is beneficial to controlling the content of the dissolved hydrogen in the primary loop coolant of the nuclear power unit, so that the reactor is safer and more reliable to operate.

The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes performed by the present specification and drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.