Device for measuring concentration of hydrogen in containment vessel on line for nuclear power plant

Abstract

The invention belongs to the technical field of concentration measurement of flammable and explosive gas, and particularly relates to an on-line measurement device for hydrogen concentration in a containment vessel for a nuclear power plant. Comprising a hydrogen sensor installed in a containment and a secondary measurement and control system installed outside the containment, and the hydrogen sensor is connected with the secondary measurement and control system. An upper protective breathable layer is arranged on the mounting fixing frame, a lower protective breathable layer is arranged below the mounting fixing frame, an upper protective cover is arranged on the upper protective breathable layer, and a lower protective cover is arranged below the lower protective breathable layer; the first temperature measuring sensor is close to the electric heating element and fixed to the center of the upper protective cover, and the distance between the second temperature measuring sensor and the first temperature measuring sensor is 20-30 mm. The continuous measurement of the hydrogen concentration in the containment vessel under the accident condition of the nuclear power plant can be safely and reliably realized.

Description

Technical Field

[0001] The invention belongs to the technical field of flammable and explosive gas concentration measurement, and in particular relates to an online hydrogen concentration measurement device in a containment vessel of a nuclear power plant. Background Art

[0002] A large amount of hydrogen will be generated under accident conditions in nuclear power plants. The sources of hydrogen are: the loss of water in the core makes it impossible to extract the residual heat, the increase in core temperature causes the fuel cladding to react with water to release a large amount of hydrogen, and the residual heat of the reactor is released into the containment, which is in a high temperature, high pressure, high water vapor, and high irradiation state; in addition, the core produces and releases some toxic fission materials, and the operation of the containment spray system and other factors make the environmental conditions in the containment more complicated than general industrial processes. The task of hydrogen concentration monitoring after a serious accident in the containment requires much higher technical levels of gas concentration monitoring equipment than the hydrogen monitoring needs in ordinary atmosphere and other general industrial environments.

[0003] For the hydrogen concentration in the containment, a common measurement method is to extract a small amount of gas in the containment as sample gas and send it to the outside of the containment through a transmission pipeline. After gas pretreatment outside the containment, the hydrogen concentration in the gas is measured by a hydrogen sensor. The measurement process includes: gas pretreatment and gas concentration analysis are completed outside the containment. This method has application precedents at home and abroad. Due to the pipeline transmission of radioactive gas, this method has the disadvantages of delayed response and potential risk of radioactive leakage. At the same time, due to the limitation of the measurement pipeline, it is generally arranged as a single-point measurement. The state of the gas changes during the transmission process, and the accuracy of the measurement result is affected. Due to the existence of gas pretreatment and gas transmission pipelines, the system is more complex, with more energy-consuming equipment and high power consumption. However, the hydrogen sensor is arranged in the accident area in the containment to directly obtain analog signals related to the hydrogen concentration. It does not require special gas treatment processes or devices, and there is no potential risk of gas leakage. Therefore, it has higher application value and is the key direction of technical development in the field of hydrogen concentration monitoring after the containment accident.

[0004] Since the gas in the containment under accident conditions presents the characteristics of high temperature, high pressure and high radioactivity, the measurement of hydrogen concentration has increased greatly. At present, there are precedents for online measurement of hydrogen concentration in the containment of nuclear power plants, which are based on the catalytic combustion measurement principle. The catalyst-type sensor used in it has a short life (needs to be replaced every 3 years), a large maintenance workload, and high operation and maintenance costs. At the same time, the traditional thermal conductivity principle hydrogen concentration online measurement device cannot overcome the harsh environmental conditions such as high temperature, high pressure, and high radioactivity of the gas in the containment under accident conditions. There is no directly applicable online measurement device for hydrogen concentration in the containment of nuclear power plants based on the thermal conductivity principle. Summary of the invention

[0005] The object of the present invention is to provide an online measurement device for hydrogen concentration in a containment vessel of a nuclear power plant.

[0006] A new type of containment hydrogen concentration monitor based on the thermal conductivity principle was invented to replace the containment hydrogen concentration monitor based on the on-site catalytic combustion principle, solving the problems of short life of catalyst-type sensors (need to be replaced every three years), large maintenance workload, and high operating and maintenance costs.

[0007] We invented and carried out research on online monitoring technology of hydrogen concentration based on the principle of heat conduction under severe accident conditions, development of sensors, development of secondary measurement and control systems, and performance verification tests of the whole equipment. We mastered the design, manufacturing and performance testing technologies of hydrogen concentration monitoring devices, overcame the harsh environment of on-site measurements, and developed a hydrogen concentration monitoring device that meets the technical requirements for hydrogen concentration measurement under accident conditions in the containment of nuclear power plants. We also carried out function and performance tests and identification tests on the device, which is used for monitoring and management of hydrogen in the containment of nuclear power plants under severe accidents.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is:

[0009] An online measurement device for hydrogen concentration in a containment of a nuclear power plant comprises a hydrogen sensor installed in the containment and a secondary measurement and control system installed outside the containment. The hydrogen sensor and the secondary measurement and control system are connected.

[0010] The hydrogen sensor and the secondary measurement and control system are connected by cables.

[0011] The hydrogen sensor consists of an upper protective cover, a first temperature sensor, an electric heating element, an upper protective breathable layer, a second temperature sensor, a mounting bracket, a lower protective breathable layer and a lower protective cover; the upper protective breathable layer is arranged on the mounting bracket, the lower protective breathable layer is arranged under the mounting bracket, the upper protective cover is arranged on the upper protective breathable layer, and the lower protective cover is arranged under the lower protective breathable layer; the first temperature sensor and the electric heating element are close together and fixed at the center of the upper protective cover, and the second temperature sensor is 20-30mm away from the first temperature sensor.

[0012] The upper protective breathable layer and the lower protective breathable layer are both cylindrical.

[0013] The diameter of the upper protective breathable layer and the lower protective breathable layer is 80mm-150mm, and the thickness of the stainless steel wire mesh used is 3-10mm.

[0014] The upper protective cover and the lower protective cover are made of stainless steel with a thickness of 3-6 mm.

[0015] The diameter of the electric heating element is 2-5 mm.

[0016] The first temperature sensor and the second temperature sensor have a diameter of 2-5 mm and are made of platinum resistance or armored thermocouple.

[0017] The secondary measurement and control system includes a concentration display data storage and upload module and a data acquisition and processing module, and uses PLC to complete data acquisition and calculation as well as 4-20mA analog output.

[0018] After an accident occurs, the stabilized ambient temperature T in the containment is monitored by the second temperature sensor and output to the data acquisition and processing module; the heating power of the electric heating element is controlled by the data acquisition and processing module to increase its surface temperature to 100°C to 200°C higher than the ambient temperature; the surface temperature of the electric heating element is monitored by the first temperature sensor, and the heating power of the electric heating element at this time is recorded; the hydrogen concentration is calculated according to the heating power of the electric heating element, as shown in formula (1), and displayed;

[0019] C H2 = K1×W 3 + K2×W 2 +K3×W+K4 (1)

[0020] C H2 To calculate the hydrogen concentration, the unit is %; K1, K2, K3, K4 are parameters, and the specific values ​​of the parameters are obtained after a large number of tests. W is the heating power of the electric heating element, the unit is watt.

[0021] The beneficial effects achieved by the present invention are:

[0022] The device of the present invention uses a structure of two temperature measuring sensors and an electric heating element, and can safely and reliably realize continuous measurement of hydrogen concentration in the containment under accident conditions of a nuclear power plant.

[0023] The hydrogen sensor of the device of the present invention is directly installed in the containment shell, which does not require special gas processing process or equipment, does not have potential gas leakage risks, and the measurement process is safe and reliable.

[0024] The hydrogen sensor of the device described in the present invention is based on the principle of thermal conductivity. Compared with sensors based on the catalytic combustion measurement principle, it has the advantages of long service life (needs to be replaced every 10 years), small maintenance workload, low operating cost, etc., and can safely and reliably realize continuous measurement of hydrogen concentration in the containment under accident conditions of nuclear power plants.

[0025] The secondary measurement and control system has passed the equipment performance verification tests such as earthquake resistance, radiation resistance, and electromagnetic interference protection. It can safely and stably monitor the hydrogen concentration in the containment under high temperature, high radioactivity, earthquake and other working conditions, and has strong reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of an online measurement device for hydrogen concentration in the containment of a nuclear power plant.

[0027] Figure 2 Schematic diagram of a hydrogen sensor.

[0028] Figure 3 This is the schematic diagram of the secondary measurement and control system.

[0029] Figure 4 This is a schematic diagram of the cabinet structure of the secondary measurement and control system.

[0030] In the figure, 1 is a hydrogen sensor, 2 is a containment shell, 3 is a penetration piece, 4 is a secondary measurement and control system, 5 is a concentration display data storage and upload module, 6 is a data acquisition and processing module, 7 is an upper protective cover, 8 is a first temperature sensor, 9 is an electric heating element, 10 is an upper protective breathable layer, 11 is a second temperature sensor, 12 is a mounting bracket, 13 is a lower protective breathable layer, and 14 is a lower protective cover. DETAILED DESCRIPTION

[0031] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] An online measurement device for hydrogen concentration in a containment of a nuclear power plant comprises: a hydrogen sensor installed in the containment, and a secondary measurement and control system installed outside the containment, wherein the hydrogen sensor and the secondary measurement and control system are connected via a cable;

[0033] Hydrogen sensor: measures the hydrogen concentration inside the containment of a nuclear power plant.

[0034] The hydrogen sensor used in the present invention uses the principle of thermal conductivity. The sensor is composed of an upper protective cover, a first temperature sensor, an electric heating element, an upper protective breathable layer, a second temperature sensor, a mounting bracket, a lower protective breathable layer and a lower protective cover. An upper protective breathable layer 10 is arranged on the mounting bracket 12, a lower protective breathable layer 13 is arranged under the mounting bracket 12, an upper protective cover 7 is arranged on the upper protective breathable layer 10, and a lower protective cover 14 is arranged under the lower protective breathable layer 13.

[0035] The hydrogen sensor used in the present invention has an upper protective breathable layer and a lower protective breathable layer structure, both of which are cylindrical and can filter aerosols and other dust in the environment to protect the internal environment of the sensor from being polluted. The diameter of the upper protective breathable layer and the lower protective breathable layer is 80mm-150mm, and the thickness of the stainless steel wire mesh used is 3-10mm.

[0036] The upper protective cover and the lower protective cover of the hydrogen sensor used in the present invention can effectively prevent water and protect the sensor performance from being affected by the spray liquid in an accident. The upper protective cover and the lower protective cover are made of stainless steel with a thickness of 3-6 mm.

[0037] The electric heating element of the hydrogen sensor used in the present invention is fixed at the center of the upper protective cover, and the diameter of the electric heating element is 2-5 mm.

[0038] The first temperature sensor and the second temperature sensor of the hydrogen sensor used in the present invention are close to the electric heating element and fixed at the center of the upper protective cover, and the second temperature sensor is 20-30mm away from the first temperature sensor. The diameter of the first temperature sensor and the second temperature sensor is 2-5mm, and platinum resistance or armored thermocouple is selected.

[0039] All shells of the hydrogen sensor used in the present invention are made of stainless steel, so that the sensor can be used in a high temperature, high pressure, and high radiation environment.

[0040] Secondary measurement and control system: PLC system is used to complete data acquisition, program calculation and 4-20mA analog output, and the display instrument completes the numerical display of hydrogen concentration.

[0041] The secondary measurement and control system used in the present invention includes a concentration display data storage and upload module and a data acquisition and processing module. The signal processing cabinet is installed on site in the nuclear power plant. The cabinet is a single-door form, and the panel is arranged with a data display instrument, a start / stop button, and an indicator light. The main components in the cabinet include: PLC module, display, indicator light, circuit breaker, terminal block, DC power supply, cable. It meets the national standard requirements for heat aging resistance, radiation aging resistance, seismic resistance, vibration resistance, etc.

[0042] The measuring method of the online measuring device for measuring hydrogen concentration in a containment of a nuclear power plant according to the present invention adopts the following steps:

[0043] 1. After an accident occurs, the second temperature sensor is used to monitor the stable ambient temperature (T) inside the containment and output it to the data acquisition and processing module;

[0044] 2. Control the heating power of the electric heating element through the data acquisition and processing module, increase its surface temperature to 100°C to 200°C higher than the ambient temperature (T+100°C to 200°C), monitor the surface temperature of the electric heating element through the first temperature measuring sensor, and record the heating power of the electric heating element at this time;

[0045] 3. Calculate the hydrogen concentration based on the heating power of the electric heating element, as shown in formula (1), and display it.

[0046] C H2 = K1×W 3 + K2×W 2 +K3×W+K4 (1)

[0047] C H2 To calculate the hydrogen concentration, the unit is %; K1, K2, K3, K4 are parameters, and the specific values ​​of the parameters are obtained after a large number of tests. W is the heating power of the electric heating element, the unit is watt.

[0048] The key points and protection points of the present invention are:

[0049] 1. Use a structure with two temperature sensors and one electric heating element. After an accident occurs, the second temperature sensor is used to monitor the stabilized ambient temperature (T) inside the containment and output it to the data acquisition and processing module; the data acquisition and processing module controls the heating power of the electric heating element, raising its surface temperature to 100℃~200℃ higher than the ambient temperature (T+100℃~200℃, monitors the surface temperature of the electric heating element through the first temperature sensor, and records the heating power of the electric heating element at this time, and calculates the hydrogen concentration based on the heating power of the electric heating element.

[0050] 2. The use of stainless steel wire mesh on the side of the device of the present invention can ensure gas circulation.

[0051] 3. A stainless steel plate without openings is used on the top of the device of the present invention to achieve a spray-proof effect for the sensor.

[0052] 4. The secondary measurement and control system and sensors of the device of the present invention have passed the equipment performance verification test and identification test such as earthquake resistance, radiation resistance and electromagnetic interference resistance. A thermal conductivity principle hydrogen concentration monitoring device that meets the technical requirements for hydrogen concentration measurement under nuclear power plant containment accident conditions has been developed and mastered.

Claims

1. An online measurement device for hydrogen concentration in a containment vessel for a nuclear power plant, characterized in that: It includes a hydrogen sensor installed in the containment shell, and a secondary measurement and control system installed outside the containment shell, and the hydrogen sensor and the secondary measurement and control system are connected.

2. The on-line measuring device for hydrogen concentration in a containment vessel of a nuclear power plant according to claim 1, characterized in that: The hydrogen sensor and the secondary measurement and control system are connected by cables.

3. The on-line measuring device for hydrogen concentration in a containment vessel of a nuclear power plant according to claim 1, characterized in that: The hydrogen sensor consists of an upper protective cover, a first temperature sensor, an electric heating element, an upper protective breathable layer, a second temperature sensor, a mounting bracket, a lower protective breathable layer and a lower protective cover; the upper protective breathable layer is arranged on the mounting bracket, the lower protective breathable layer is arranged under the mounting bracket, the upper protective cover is arranged on the upper protective breathable layer, and the lower protective cover is arranged under the lower protective breathable layer; the first temperature sensor and the electric heating element are close together and fixed at the center of the upper protective cover, and the second temperature sensor is 20-30mm away from the first temperature sensor.

4. The on-line measuring device for hydrogen concentration in a containment vessel of a nuclear power plant according to claim 3, characterized in that: The upper protective breathable layer and the lower protective breathable layer are both cylindrical.

5. The on-line measuring device for hydrogen concentration in a containment vessel of a nuclear power plant according to claim 3, characterized in that: The diameter of the upper protective breathable layer and the lower protective breathable layer is 80mm-150mm, and the thickness of the stainless steel wire mesh used is 3-10mm.

6. The on-line measuring device for hydrogen concentration in a containment vessel of a nuclear power plant according to claim 3, characterized in that: The upper protective cover and the lower protective cover are made of stainless steel with a thickness of 3-6 mm.

7. The on-line measuring device for hydrogen concentration in a containment vessel of a nuclear power plant according to claim 3, characterized in that: The diameter of the electric heating element is 2-5 mm.

8. The on-line measuring device for hydrogen concentration in a containment vessel of a nuclear power plant according to claim 3, characterized in that: The first temperature sensor and the second temperature sensor have a diameter of 2-5 mm and are made of platinum resistance or armored thermocouple.

9. The on-line measuring device for hydrogen concentration in a containment vessel of a nuclear power plant according to claim 3, characterized in that: The secondary measurement and control system includes a concentration display data storage and upload module and a data acquisition and processing module, and uses PLC to complete data acquisition and calculation as well as 4-20mA analog output.

10. The on-line measurement device for hydrogen concentration in a containment vessel of a nuclear power plant according to claim 9, characterized in that: After an accident occurs, the stabilized ambient temperature T in the containment is monitored by the second temperature sensor and output to the data acquisition and processing module; the heating power of the electric heating element is controlled by the data acquisition and processing module to increase its surface temperature to 100°C to 200°C higher than the ambient temperature; the surface temperature of the electric heating element is monitored by the first temperature sensor, and the heating power of the electric heating element at this time is recorded; the hydrogen concentration is calculated according to the heating power of the electric heating element, as shown in formula (1), and displayed; C H2 = K1×W 3 + K2×W 2 +K3×W+K4 (1) C H2 To calculate the hydrogen concentration, the unit is %; K1, K2, K3, K4 are parameters, and the specific values ​​of the parameters are obtained after a large number of tests. W is the heating power of the electric heating element, the unit is watt.

Images