JP6608687B2 - Gas detector - Google Patents

Description

Embodiments of the present invention relates to a gas detector for detecting flammable object gas.

  For example, when a serious accident occurs at a nuclear power plant, it is important to monitor the hydrogen gas concentration in the reactor containment vessel and each place in the reactor building, and hydrogen gas detectors are installed at the locations that are assumed in the design. Thus, it is necessary to monitor the hydrogen concentration level.

  As a hydrogen gas detector for detecting the hydrogen gas concentration, a technique is known that utilizes the property that the electrical resistance changes when a hydrogen sensing element (for example, a palladium alloy) adsorbs hydrogen. In such a hydrogen gas detector, in order to stabilize the function of appropriately releasing the adsorbed hydrogen from the hydrogen sensing element according to the fluctuation of the hydrogen gas concentration after the hydrogen sensing element has adsorbed hydrogen, It is necessary to keep the surroundings at a constant temperature. For this purpose, the detector uses an electric heater to control the ambient temperature to be constant.

  On the other hand, there is a possibility that hydrogen reacts with oxygen and burns explosively due to the failure or abnormal heating of this electric heater. In such a case, the hydrogen gas detector container has sufficient strength to withstand the internal explosion even if it occurs. Therefore, it is required that the flame generated inside the hydrogen gas detector container diffuses to the outside and does not ignite outside the hydrogen gas detector. Therefore, an explosion-proof structure is generally used to prevent the flame generated inside the hydrogen gas detector from propagating to the outside.

  The detector container of the above-described hydrogen gas detector needs to transmit hydrogen gas as a detection target, and to prevent the flame from propagating to the outside when a flame is generated inside. Further, when a flame is generated inside, it is necessary to release the internal gas to the outside in order to suppress an increase in internal pressure.

  For this purpose, there is known a technique of providing a porous sintered metal window on two surfaces of a metal container, for example, a rectangular parallelepiped, facing each other. These windows are formed with a number of thin and curved flow paths that allow gas to pass therethrough and prevent the flame from propagating to the outside when a flame is generated inside.

JP2013-140114A

  The detector container of the hydrogen gas detector described above has an increased internal pressure and a large internal / external pressure difference when an explosion occurs inside. In that case, the detector container needs strength to confine the flame inside, and therefore, the detector container is thick and heavy, which is inconvenient to handle.

  In particular, when the detector container has a rectangular parallelepiped shape, the deformation of each surface tends to increase due to the internal / external differential pressure, and the thickness of the porous sintered metal window portion has to be increased.

Embodiments of the present invention has been made to solve the above problems, and an object thereof is to enable the weight of the gas detector for detecting flammable gas.

In order to achieve the above object, a gas detector according to an embodiment of the present invention is a gas detector that is installed in a nuclear reactor containment vessel and detects hydrogen gas, and includes a heat source to detect hydrogen gas. A gas detector that surrounds and houses the gas detector with a flame blocking cylinder formed with a large number of fine through-holes that transmit hydrogen gas and prevent flame propagation, and the flame blocking detachably mounted on the outside of the cylinder, the gas detection unit or by preventing intrusion of the poison gas corrosive to the detector container, characterized in that it has a gas filter which transmits the hydrogen gas And

According to an embodiment of the invention, a gas detector for detecting flammable gas can lighter.

It is typical sectional drawing of the gas detector which concerns on embodiment of this invention, and is the II sectional view taken on the line of FIG. It is the II-II arrow directional cross-sectional view of the gas detector of FIG. It is a typical elevation sectional view of the gas detector of Drawing 1, and is a figure showing the state where a sealing lid was attached.

  Hereinafter, a gas detector according to an embodiment of the present invention will be described with reference to the drawings. Here, a hydrogen detector that is suitable for installation in a reactor containment vessel and that uses hydrogen gas as a measurement target gas (target gas) will be described as an example.

FIG. 1 is a schematic vertical sectional view of a gas detector according to an embodiment of the present invention, and is a cross-sectional view taken along the line II in FIG. 2 is a side sectional view of the gas detector of FIG. 1 taken along the line II-II.

  The gas detector 10 includes a gas detector 11, a detector container 12 that houses the gas detector 11, and a gas filter 13 that is detachably attached to the outside of the detector container 12.

  The gas detection unit 11 includes a winding core 14 made of an insulating material, a hydrogen detection element (for example, a resistance wire made of a palladium alloy) 15 wound around the outside of the winding core 14 in a solenoid shape while maintaining insulation from each other, and temperature compensation. Element 16 (for example, platinum resistance wire), electric heater 17 arranged so as to surround hydrogen detecting element 15 and temperature compensating element 16, and outside of hydrogen detecting element 15, temperature compensating element 16 and electric heater 17 It has the cylindrical heat insulating material 18 arrange | positioned so that it may cover. The winding core 14 is, for example, a solid or hollow cylindrical member made of an insulating material such as aluminum oxide.

  The detector container 12 is a substantially cylindrical container, and its cylindrical side wall constitutes a flame prevention cylinder 20. The flame blocking cylinder 20 has a structure that allows gas to pass therethrough and prevents flame propagation. Therefore, the flame blocking cylinder 20 has a structure in which a large number of fine through holes are formed. Each through hole preferably has a bent portion in the middle.

  As the flame prevention cylinder 20, for example, a laminated wire mesh in which a plurality of wire meshes are laminated can be bent into a cylindrical shape. For example, a laminated wire mesh having a thickness of 1 mm or more and a hole diameter of 150 μm or less can be used. Further, a plurality of commercially available laminated wire meshes bent into a cylindrical shape may be arranged in a coaxial cylindrical shape. In the illustrated example, two laminated wire nets bent into a cylindrical shape are coaxially stacked. By adopting such a configuration, it is possible to realize a structure that has good air permeability and can prevent flame propagation.

  Both ends of the detector container 12 are closed by a circular flat plate-like first end plate 21 and second end plate 22.

  The flame blocking cylinder 20 and the end plates 21 and 22 are desirably made of a material having high structural strength and corrosion resistance, for example, stainless steel.

  The first end plate 21 is provided with a through hole, and an electric wire outlet connector 23 is attached so as to close the through hole. A cable 24 is connected to the wire outlet connector 23. The hydrogen detection element 15, the temperature compensation element 16, and the electric heater 17 are electrically connected to the wire outlet connector 23, and are further electrically connected to the external instrument panel 41 via the cable 24. . The instrument panel 41 includes a power source, an electric circuit, a data processing device, and the like (not shown).

  A through hole is formed in the second end plate 22, and a calibration gas supply pipe 25 is connected to the through hole. A calibration gas supply source 40 such as a calibration gas cylinder is connected to the calibration gas supply pipe 25, and a calibration gas supply valve 26 is connected midway.

  A thermometer 30 and a pressure gauge 31 for measuring the temperature and pressure in the detector container 12 are attached. The thermometer 30 and the pressure gauge 31 are electrically connected to the instrument panel 41 via the wire outlet connector 23 and the cable 24.

  One or both of the first end plate 21 and the second end plate 22 or a part of them can be removed from the flame blocking cylinder 20, and the above-described hydrogen detection element 15, temperature compensation element 16, the electric heater 17, the thermometer 30, the pressure gauge 31, etc. can be maintained, inspected and replaced.

  The gas filter 13 is disposed so as to surround the flame prevention cylinder 20. The gas filter 13 is for adsorbing the corrosive poison gas contained in the atmospheric gas to prevent the flame prevention cylinder 20 and the gas detection unit 11 from being corroded. For example, when the poisoning gas is iodine gas, the gas filter 13 can use an iodine adsorbent such as zeolite.

  Since the gas filter 13 usually needs to be periodically replaced with a new one or removed and regenerated by washing or the like, the gas filter 13 is preferably removable. Thereby, according to the installation environment of the gas detector 10, the suitable gas filter 13 can be selected and attached. When the detector container 12 is installed in an environment where no poison gas exists, the gas filter 13 may be unnecessary. In such a case, the gas filter 13 may be removed.

  In the illustrated example, the gas detector 10 is fixed by, for example, a fixture 35 inside the side wall 34 (FIG. 2) of the reactor containment vessel. The fixture 35 is fixed to, for example, the first and second end plates 21 and 22 of the detector container 12.

  Further, a droplet holder 36 is fixed inside the side wall 34 so as to cover the upper part of the detector container 12. This is because, for example, when the detector vessel 12 is arranged in the reactor containment vessel, spray water from the containment vessel spray (not shown) for cooling the reactor containment vessel is prevented from being applied to the detector vessel 12. Or it is for suppressing.

  Further, it is preferable to apply a coating for preventing corrosion on the surface of the detector container 12. Furthermore, it is more preferable to apply a coating for preventing corrosion to the surfaces of the gas filter 13, the fixture 35, the droplet holder 36 and the like. Such a coating can prevent or suppress corrosion caused by environmental gases such as iodine. The coating is, for example, a silicon oxide coating having a thickness of 100 nm or more. As a coating method, CVD (chemical vapor deposition), PVD (physical vapor deposition), or the like can be used. Further, when it is necessary to particularly cope with corrosion due to hydrogen sulfide or chlorine, an anticorrosive material can be welded to the outer surface of the detector container 12.

  Next, the operation of the gas detector 10 will be described.

  During normal operation in which the gas detector 10 detects the gas concentration, a current is passed through the hydrogen detection element 15 and the temperature compensation element 16. The target gas (hydrogen gas) in the environmental gas outside the detector container 12 flows through the gas filter 13 and the flame blocking cylinder 20 to a position where it contacts the hydrogen detection element 15 and the temperature compensation element 16. At this time, the calibration gas supply valve 26 is closed.

  As the hydrogen detection element 15 occludes hydrogen in the detector container 12, the electrical resistance of the hydrogen detection element 15 changes according to the change in the hydrogen concentration. The hydrogen concentration can be detected by comparing the change in the electric resistance of the hydrogen detecting element 15 with the resistance of the temperature compensating element 16.

  At this time, a current is passed through the electric heater 17 to generate heat, and the temperature of the hydrogen detection element 15 is maintained at about 300 ° C. The hydrogen detection element 15 can maintain the adsorption and release of hydrogen reversibly by being maintained at about 300 ° C. Due to the presence of the heat insulating material 18, wasteful release of heat generated by the electric heater 17 is suppressed, and the hydrogen detection element 15 can be kept warm substantially uniformly.

  At this time, the temperature and pressure in the detector container 12 can be measured by the thermometer 30 and the pressure gauge 31.

  The hydrogen concentration can be measured based on the results of measuring the voltage and current of the hydrogen detecting element 15 and the temperature compensating element 16 and measuring the temperature and pressure in the detector container 12.

  Next, a calibration method of the gas detector 10 will be described.

  FIG. 3 is a schematic vertical sectional view of the gas detector shown in FIG. 1 and shows a state where a sealing lid is attached.

  In calibrating the gas detector 10, as shown in FIG. 3, the outside of the gas filter 13 is covered with a sealing lid 50, and the atmosphere of the gas detector 11 is isolated from the outside. Then, the calibration gas supply valve 26 is opened, and the calibration gas is introduced into the detector container 12 from the calibration gas supply source 40 through the calibration gas supply pipe 25. Thereby, the gas detection part 11 can be operated in the known atmosphere containing the target gas supplied from the calibration gas supply source 40, and the gas detection part 11 can be calibrated. Moreover, calibration can be easily performed with the gas detector 10 installed.

  According to the gas detector 10 according to the embodiment of the present invention described above, in the detector container of the gas detector that detects the flammable gas, there are a large number of fine through-holes that transmit the target gas and prevent flame propagation. By using an explosion-proof structure provided with the formed flame blocking cylinder, the detector container can be reduced in weight.

  In the above description, the detector container 12 is substantially cylindrical, but it does not necessarily have to be cylindrical. The shape of the cross section may be an elliptical shape or a polygonal cylindrical shape such as a pentagon or more as long as it is a shape that can easily receive a force due to the difference between the internal and external pressures.

  In the above description, the laminated wire mesh is used as the constituent material of the flame prevention cylinder 20, but as a modification, for example, the constituent material of the flame prevention cylinder 20 is porous sintered similar to the conventional flame propagation prevention window. Metal can also be used.

  Further, as a constituent material of the flame blocking cylinder 20, a perforated metal or earthenware can be used. For example, a number of through-holes having a diameter of 1 μm are formed in a flat plate made of stainless steel having a thickness of 1 mm at regular intervals, and then the flat plate is bent into a cylindrical shape to form the flame prevention cylinder 20.

  In the above description, the wire outlet connector 23 is attached to the first end plate 21 and the calibration gas supply pipe 25 is attached to the second end plate 22. However, as a modification, one end plate is used. It is also possible to attach both the wire outlet connector 23 and the calibration gas supply pipe 25. A part of the plurality of wire outlet connectors 23 can be attached to the first end plate 21 and the rest can be attached to the second end plate 22.

  The hydrogen detector suitable for installation in the reactor containment vessel has been described above as an example, but the present invention is not limited to this. The installation location may be other than inside the reactor containment vessel.

  The detection target is not limited to hydrogen gas, and any flammable gas is applicable. In the above description, an electric heater is assumed as a gas ignition source (heat generation source), but even without a heater, for example, discharge of an electrical product can be an ignition source (heat generation source). Therefore, the present invention can be applied even in such a situation.

  As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 10: Gas detector, 11: Gas detection part, 12: Detector container, 13: Gas filter, 14: Winding core, 15: Hydrogen detection element, 16: Element for temperature compensation, 17: Electric heater (heater, heat source) ), 18: heat insulating material, 20: flame blocking cylinder, 21: first end plate, 22: second end plate, 23: wire outlet connector, 24: cable, 25: calibration gas supply pipe, 26: Calibration gas supply valve, 30: Thermometer, 31: Pressure gauge, 34: Side wall, 35: Fixing tool, 36: Droplet removal, 40: Calibration gas supply source, 41: Instrument panel, 50: Sealing lid

Claims (8)

A gas detector installed in a reactor containment vessel for detecting hydrogen gas,
A gas detector that includes a heat source and detects hydrogen gas;
A detector container that surrounds and accommodates the gas detection unit with a flame blocking cylinder formed with a large number of fine through-holes that transmit hydrogen gas and block flame propagation ; and
A gas filter that is detachably attached to the outside of the flame blocking cylinder, prevents the entry of corrosive poison gas into the gas detector or the detector container, and transmits the hydrogen gas;
Gas detector, comprising a.   The gas detector according to claim 1, wherein the flame blocking cylinder includes a laminated wire mesh in which a plurality of wire meshes are laminated.   The gas detector according to claim 1, wherein the flame prevention cylinder includes a sintered metal. The detector container includes two flat end plates that close both ends of the flame blocking cylinder,
On at least one side of the end plate, an electric wire outlet connector, a cable electrically connected to the gas detection unit via the electric wire outlet connector,
Have
On the other side of the end plate, there is a calibration gas supply pipe extending through and capable of supplying calibration gas from the outside to the gas detection unit during calibration of the gas detection unit,
Gas detector according to any one of claims 1 to 3, characterized in. 5. The apparatus according to claim 1, further comprising a sealing lid configured to be openable and closable so that the entire flame prevention cylinder can be hermetically surrounded from the outside during calibration of the gas detection unit. The gas detector according to one item . 6. The liquid droplet removal device according to claim 1, further comprising a liquid drop remover that is disposed outside the detector container and suppresses liquid droplets from the outside from being applied to the detector container. The gas detector described in 1. The gas detector according to any one of claims 1 to 6, wherein a coating for preventing corrosion is applied to an outer surface of the detector container . The gas detection unit
A hydrogen sensing element whose electrical resistance value changes by occluding hydrogen gas;
A heater for heating the hydrogen detection element as the heat source;
Include, gas detector according to any one of claims 1 to 7, characterized in.

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