JP2021189058A - Device and method for measuring gas concentration inside nuclear reactor containment - Google Patents

Abstract

To provide a device and the like for measuring gas concentrations inside a nuclear reactor containment that allow measurement of concentrations of oxygen and water vapor in the nuclear reactor containment, by eliminating the need for gas sampling.SOLUTION: A device for measuring gas concentrations inside a nuclear reactor containment is equipped with: water vapor detecting means that is installed inside a nuclear reactor containment in order to detect water vapor inside the nuclear reactor containment by detecting a first electric physical quantity output from a limiting current type sensor using solid electrolytes; oxygen concentration measuring means that is installed inside the nuclear reactor containment in order to measure an oxygen concentration inside the nuclear reactor containment according to a concentration cell type sensor using solid electrolytes; and water vapor concentration measuring means for obtaining a value of a water vapor concentration inside the nuclear reactor containment, from a value of the first electric physical quantity acquired from the water vapor detecting means, and a value of the oxygen concentration inside the nuclear reactor containment acquired from the oxygen concentration measuring means, by referring to data showing a relationship between a first electric physical quantity given in beforehand and an oxygen concentration of gas to be measured, and data showing a relationship between a first electric physical quantity and a water vapor concentration of gas to be measured.SELECTED DRAWING: Figure 1

Description

An embodiment of the present invention relates to a gas concentration measuring device and a gas concentration measuring method in a reactor containment vessel.

Nuclear power plants have introduced a system for measuring the oxygen concentration in the reactor containment vessel from the viewpoint of preventing accidents and preventing the spread of accidents in the event of a severe accident. In the above-mentioned oxygen concentration measurement system in the reactor containment vessel, the gas in the reactor containment vessel is sucked out of the reactor containment vessel by a sampling device and sampled, and then the above-mentioned sampled gas is cooled by a cooler and dehumidified. After dehumidifying with, it is introduced into an oxygen gas analyzer and the oxygen concentration is measured (see Patent Document 1).

Japanese Patent No. 369804

The oxygen concentration measurement system described above includes a sampling device that sucks the gas inside the reactor containment vessel to the outside of the reactor containment vessel for sampling, a cooler for cooling the sampling gas, and dehumidifies the sampling gas. Since it is equipped with a dehumidifier for this purpose, it becomes difficult to measure the oxygen concentration in the reactor containment vessel if a trouble occurs in the above-mentioned sampling device, cooler and dehumidifier.

Problems with the sampling device include damage to the sampling pipe and stoppage of the suction pump due to loss of AC power. Further, the dew condensation prevention heater attached to the sampling pipe may be stopped due to the loss of the AC power supply, the sampling pipe may be filled with dew condensation water, and the inside of the pipe may be closed. Further, since the cooler and the dehumidifier require cooling water, if the cooling water source is lost, the sampling gas cannot be cooled and dehumidified. When the above trouble occurs, it becomes difficult to measure the oxygen concentration of the sampling gas.

On the other hand, when the sensor is installed in the reactor containment vessel and the measurement is performed directly without sampling the gas, the oxygen concentration in the state containing water vapor is measured, but the oxygen in the existing reactor containment vessel described above is measured. In the concentration measurement system, the oxygen concentration is measured in the state where the water vapor is removed, so the oxygen concentration is measured by different standards for both. In order to utilize it in combination with the existing oxygen concentration measurement system to prevent the occurrence and spread of accidents, it is desirable to measure the oxygen concentration according to the same standard, and for that purpose, the water vapor concentration was also measured and the water vapor was removed. It is necessary to evaluate the oxygen concentration in the state.

The present invention has been made in consideration of such circumstances, and in the reactor containment vessel, which eliminates the need for sampling of gas in the reactor containment vessel and can measure the concentrations of oxygen and water vapor in the reactor containment vessel. It is an object of the present invention to provide a gas concentration measuring device and a gas concentration measuring method.

The gas concentration measuring device in the reactor containment vessel of the embodiment is arranged in the reactor containment vessel and detects a first electric physical quantity output from a critical current type sensor using a solid electrolyte. Oxygen that measures the oxygen concentration in the reactor containment vessel by a steam detection means that detects steam in the reactor containment vessel and a light and light battery type sensor that is arranged in the reactor containment vessel and uses a solid electrolyte. Data showing the relationship between the concentration measuring means and the first electrically physical quantity given in advance and the oxygen concentration of the gas to be measured and data showing the relationship between the first electrical physical quantity and the steam concentration of the gas to be measured are provided. With reference to the value of the first electrical physical quantity obtained from the steam detecting means and the value of the oxygen concentration in the reactor storage container acquired from the oxygen concentration measuring means, the steam in the reactor storage container is referred to. It is provided with a steam concentration measuring means for obtaining a concentration value.

The figure which shows the basic structure of the gas concentration measuring apparatus in the reactor containment vessel which concerns on embodiment. The figure which shows the schematic structure of the oxygen sensor, the heater control device, and the oxygen detection signal measurement device which concerns on embodiment. The figure which shows the schematic structure of the water vapor sensor, the heater control device, and the water vapor detection signal measurement device which concerns on embodiment.

Hereinafter, embodiments of the gas concentration measuring device and the gas concentration measuring method in the reactor containment vessel will be described with reference to the drawings.

FIG. 1 shows a basic configuration of a gas concentration measuring device in a reactor containment vessel according to an embodiment. As shown in FIG. 1, the gas concentration measuring device 100 in the reactor containment vessel includes an oxygen sensor 1, a heater control device 2, an oxygen detection signal measuring device 3, an oxygen concentration measuring device 4, and a steam sensor 5. A heater control device 6, a water vapor detection signal measuring device 7, a water vapor concentration measuring device 8, a monitoring device 9, and a penetration device 10 are provided.

The oxygen sensor 1 and the water vapor sensor 5 are installed inside the reactor containment vessel 12, and the other devices are installed outside the reactor containment vessel 12 such as the central control room. The penetration device 10 penetrates the containment vessel wall 11 and connects cables inside and outside the reactor containment vessel 12.

FIG. 2 shows a schematic configuration of the oxygen sensor 1, the heater control device 2, and the oxygen detection signal measurement device 3 described above. A concentration cell type oxygen sensor 1 using a solid electrolyte is used, and the oxygen sensor 1 includes a solid electrolyte 16, two electrodes 17a and 17b attached thereto, a cover 19 and a heater 13. is doing.

As the solid electrolyte 16, zirconia or the like that conducts oxygen ions 30 is used. Electrodes 17a and 17b are attached to both surfaces of the solid electrolyte 16. For the electrodes 17a and 17b, oxide materials such as samarium strontium cobaltate (SSC) and lanthanum strontium manganate (LSM) having low catalytic performance are used. The cover 19 covers the electrode 17b side of the solid electrolyte 16 to form a reference gas chamber 18. The reference gas chamber 18 is filled with high-concentration oxygen (for example, 100% oxygen) having a known concentration. The oxygen detection signal measuring device 3 is composed of a voltmeter 20. A DC constant voltage power supply 15 is used for the heater control device 2 that controls the heater 13. In FIG. 2, 14 is a cable.

FIG. 3 shows a schematic configuration of the water vapor sensor 5, the heater control device 6, and the water vapor detection signal measurement device 7 described above.

The water vapor sensor 5 is composed of a solid electrolyte 21, an electrode (cathode 22, anode 23), a cover 24, and a heater 13. Zirconia or the like that conducts oxygen ions 30 is used as the solid electrolyte 21. The two electrodes (cathode 22 and anode 23) are attached to both sides of the solid electrolyte 21. For the two electrodes (cathode 22 and anode 23), a noble metal material having high catalytic performance such as platinum is used.

The cover 24 is provided with a diffusion hole 25 and covers the cathode 22 side of the solid electrolyte 21 to form a gas detection chamber 26. The diffusion hole 25 is for allowing the gas 31 in the reactor containment vessel 12 to flow into the gas detection chamber 26 by diffusion, and a hole having a small diameter or a porous material is used.

A DC constant voltage power supply 15 is used for the heater control device 6 that controls the heater 13. The water vapor detection signal measuring device 7 includes a variable DC power supply 27, an ammeter 28, and a voltmeter 29. In FIG. 3, 14 is a cable.

Next, the operation and effect of the gas concentration measuring device 100 in the reactor containment vessel will be described.
A current is supplied from the DC constant voltage power supply 15 of the heater control device 2 to the heater 13 of the oxygen sensor 1, and the solid electrolyte 16 of the oxygen sensor 1 is heated and maintained at a constant temperature. The solid electrolyte 16 can easily conduct oxygen ions 30 by being heated. For example, in the case of zirconia, it is usually heated to 400 ° C. to 800 ° C. and used as an oxygen ion conductor.

In the present embodiment, the oxygen ion 30 is maintained at the lowest temperature that can be conducted, for example, about 400 ° C. in the case of zirconia. The solid electrolyte 16 acts as a concentration cell type sensor, and an electromotive force according to Ernst's equation is generated between the electrodes 17a and 17b depending on the oxygen concentration in the reactor containment vessel 12 and the reference gas chamber 18. Since the oxygen concentration in the reference gas chamber 18 is kept constant, the above electromotive force depends on the oxygen concentration in the reactor containment vessel 12, and therefore, the potential difference between the electrodes 17a and 17b should be measured. Therefore, the oxygen concentration in the reactor containment vessel 12 can be obtained.

When a severe accident occurs, hydrogen may be generated in the reactor containment vessel 12. However, by using a material having low catalytic performance for the electrode 17a and keeping the temperature of the solid electrolyte 16 low, hydrogen at the electrode 17a It is possible to suppress the occurrence of combustion and accurately measure the oxygen concentration. The potential difference between the electrodes 17a and 17b is measured by the voltmeter 20 of the oxygen detection signal measuring device 3, and the measured signal is output to the oxygen concentration measuring device 4.

In the oxygen concentration measuring device 4, the oxygen concentration in the reactor containment vessel 12 is calculated from Ernst's equation using the oxygen concentration value in the reference gas chamber 18 and the set temperature of the solid electrolyte 16, and the signal is sent to the monitoring device 9 and the water vapor. Output to the concentration measuring device 8.

In the water vapor sensor 5, the gas in the reactor containment vessel 12 flows into the gas detection chamber 26 from the diffusion hole 25 provided in the cover 24 of the water vapor sensor. A voltage is applied between two electrodes (cathode 22 and anode 23) provided on the solid electrolyte 21 by the variable DC power supply 27 of the water vapor detection signal measuring device 7, and the measured value of the voltmeter 29 of the water vapor detection signal measuring device 7 is measured. By feedback control using the above-mentioned applied voltage, the applied voltage is adjusted so as to be constant above a value that causes electrolysis of water.

The water vapor contained in the gas 31 flowing into the gas detection chamber 26 is electrolyzed into oxygen molecules and hydrogen molecules by the action of the voltage applied between the electrodes (cathode 22 and anode 23), and is further used for the cathode 22. Oxygen molecules are dissociated into oxygen ions 30 and electrons by the catalytic action of the noble metal.

A current is supplied from the DC constant voltage power supply 15 of the heater control device 6 to the heater 13 of the steam sensor 5, and the solid electrolyte 21 of the steam sensor 5 is heated and maintained at a constant temperature. The solid electrolyte 21 can easily conduct oxygen ions 30 by being heated. For example, in the case of zirconia, it is usually heated to 400 ° C. to 800 ° C. and used as an oxygen ion conductor.

Due to the action of the voltage applied to the heated solid electrolyte 21, the oxygen ion 30 is transported from the cathode 22 side to the anode 23 side, and a current flows between the electrodes (cathode 22 and anode 23). By appropriately setting the applied voltage between the electrodes (cathode 22 and anode 23) so that the oxygen ions 30 sufficiently flow through the solid electrolyte 21, the flow of oxygen atoms is caused by the diffusion process of water vapor in the diffusion holes 25. It becomes rate-determining. In this case, the current flowing between the electrodes (cathode 22 and anode 23) provided in the solid electrolyte 21 is called a limiting current, and has a characteristic of changing according to a change in the water vapor concentration in the gas 31.

On the other hand, the oxygen contained in the gas 31 flowing into the gas detection chamber 26 is dissociated into oxygen ions 30 and electrons by the catalytic action of the noble metal used in the cathode 22, and the oxygen ions 30 are heated solid electrolyte 21. It is transported from the cathode 22 side to the anode 23 side by the action of the applied voltage, and a current flows between the electrodes (cathode 22 and anode 23). By appropriately setting the applied voltage between the electrodes (cathode 22 and anode 23) so that the oxygen ion 30 sufficiently flows through the solid electrolyte 21, the flow of oxygen atoms is caused by the diffusion process of oxygen in the diffusion holes 25. It becomes rate-determining, and a limit current flows between the electrodes (cathode 22 and anode 23) provided in the solid electrolyte 21.

This critical current also has the property of changing in response to changes in the oxygen concentration in the gas. When hydrogen is contained in the gas 31 flowing into the gas detection chamber 26, oxygen and hydrogen cause a chemical reaction to form water vapor due to the catalytic action of the noble metal used in the cathode 22, but the formed water vapor is generated. Since it is electrolyzed into oxygen molecules and hydrogen molecules by the action of the voltage applied between the electrodes (cathode 22 and anode 23), water is electrolyzed between the electrodes (cathode 22 and anode 23) as in the present embodiment. When a voltage higher than the generated value is applied, the correlation between the above oxygen concentration and the critical current is not affected.

As described above, between the electrodes (cathode 22 and anode 23) provided in the solid electrolyte 21, a voltage that is equal to or higher than the value that causes electrolysis of water and that allows oxygen ions 30 to sufficiently flow through the solid electrolyte 21 is applied. When applied, the current flowing between the electrodes (cathode 22 and anode 23) is the sum of the limit current derived from water vapor and the limit current derived from oxygen.

The current flowing between the electrodes (cathode 22 and anode 23) is measured by the ammeter 28 of the water vapor detection signal measuring device 7, and the measured signal is output to the water vapor concentration measuring device 8. In the water vapor concentration measuring device 8, the data obtained by examining the correlation between the water vapor concentration of the measured gas 31 and the critical current value derived from the water vapor flowing between the electrodes (cathode 22 and anode 23) in advance, and the data of the measured gas 31 It contains data investigating the correlation between the oxygen concentration and the limit current value derived from oxygen flowing between the electrodes (cathode 22 and anode 23).

From the oxygen concentration input from the oxygen detection signal measuring device 3, the limit current value derived from oxygen is obtained with reference to the above data, and the limit current derived from oxygen is obtained from the current value input from the water vapor detection signal measuring device 7. By subtracting the value, the limit current value derived from water vapor can be obtained, and the water vapor concentration can be obtained from the limit current value derived from water vapor with reference to the above data.

The obtained signal of the water vapor concentration is output to the monitoring device 9, and the monitoring device 9 displays the water vapor concentration and the oxygen concentration contained in the gas 31 in the reactor containment vessel 12.

As described above, according to the present embodiment, the concentrations of oxygen and water vapor can be measured without sampling the gas 31 in the reactor containment vessel 12. That is, without using a sampling device for sucking and sampling the gas inside the reactor containment vessel to the outside of the reactor containment vessel, a cooler for cooling the sampling gas, a dehumidifier for dehumidifying the sampling gas, and the like. , The oxygen concentration in the state where water vapor is removed can be evaluated without the need for an AC power source.

Although some embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

1 ... Oxygen sensor, 2 ... Heater control device, 3 ... Oxygen detection signal measurement device, 4 ... Oxygen concentration measurement device, 5 ... Steam sensor, 6 ... Heater control device, 7 ... Water vapor detection signal measurement Equipment, 8 ... Water vapor concentration measuring device, 9 ... Monitoring device, 10 ... Penetration device, 11 ... Storage container wall, 12 ... Reactor storage container, 13 ... Heater, 14 ... Cable, 15 ... DC constant voltage power supply, 16 ... solid electrolyte, 17a, 17b ... electrode, 18 ... reference gas chamber, 19 ... cover, 20 ... voltmeter, 21 ... solid electrolyte, 22 ... electrode (cathode), 23 ... Electrode (anode), 24 ... Cover, 25 ... Diffuse hole, 26 ... Gas detection chamber, 27 ... Variable DC power supply, 28 ... Current meter, 29 ... Voltage meter, 30 ... Oxygen ion , 31 ... Gas, 100 ... Gas concentration measuring device in the reactor containment vessel.

Claims (3)

A steam detection means for detecting steam in the reactor containment vessel by detecting a first electrical physical quantity that is arranged in the reactor containment vessel and is output from a limit current type sensor using a solid electrolyte. ,
An oxygen concentration measuring means arranged in the reactor containment vessel and measuring the oxygen concentration in the reactor containment vessel by a concentration cell type sensor using a solid electrolyte.
With reference to the data showing the relationship between the first electric physical quantity and the oxygen concentration of the measured gas given in advance and the data showing the relationship between the first electric physical quantity and the water vapor concentration of the measured gas, the water vapor The value of the water vapor concentration in the reactor storage container is obtained from the value of the first electrical physical quantity acquired from the detection means and the value of the oxygen concentration in the reactor storage container acquired from the oxygen concentration measuring means. Water vapor concentration measuring means and
A gas concentration measuring device in a reactor containment vessel, which is characterized by being equipped with. The value of the first electrical physical quantity is obtained by applying a DC voltage equal to or higher than the potential that causes electrolysis of water between the two electrodes added to the solid electrolyte of the water vapor detecting means, and between the two electrodes. The gas concentration measuring device in the reactor storage container according to claim 1, wherein the current value flows through the reactor. A concentration cell type oxygen sensor using a solid electrolyte placed in the reactor containment vessel and a limit current type sensor using the solid electrolyte placed in the reactor containment vessel are used in combination.
From the oxygen concentration measured by the concentration cell type oxygen sensor and the current value flowing between the electrodes when a DC voltage higher than the potential that causes water electrolysis is applied between the electrodes of the limit current type sensor. A method for measuring a gas concentration in a reactor storage container, which comprises measuring the water vapor concentration in the reactor storage container.

Images