JP7021058B2 - Oxygen concentration measuring device and reactor facility - Google Patents

Description

Embodiments of the present invention relate to an oxygen concentration measuring device and a nuclear reactor facility.

The power reactor facility has equipment to ensure the safety of the reactor and the facility in the event of a severe accident, and has a mechanism to grasp the situation of the accident and take measures for convergence.

In particular, in the severe accident at the Fukushima Daiichi Nuclear Power Station following the Great East Japan Earthquake, a hydrogen explosion caused by the reaction between hydrogen and oxygen has caused damage to the reactor facilities, and it is necessary to monitor the gas phase concentration to prevent the hydrogen explosion. ing.

In a conventional reactor facility, hydrogen and oxygen concentrations in the gas phase are measured by a containment vessel atmosphere monitor. The equipment is installed outside the reactor containment vessel, and the gas phase inside the reactor containment vessel is transferred to the equipment by a blower, and the humidity, temperature, pressure, etc. are adjusted and measured using a cooler or the like. ing.

Special Publication No. 64-4145

However, from the accident at the Fukushima Daiichi Nuclear Power Station following the Great East Japan Earthquake, it has become clear that sufficient measures cannot be taken with the existing facilities alone. In a conventional reactor facility, if the AC power supply is lost when a severe accident occurs, the containment vessel atmosphere monitor cannot be operated and constant monitoring cannot be achieved. In particular, in the severe accident at the Fukushima Daiichi Nuclear Power Station, the AC power supply was lost and monitoring became impossible, and the hydrogen explosion caused by the reaction between hydrogen and oxygen caused damage to the reactor facilities. It is important to monitor the gas phase concentration.

Therefore, there is a demand for a system that directly measures the gas phase composition in the containment vessel at the time of a severe accident without performing adjustments such as transfer of gas requiring an AC power source, dehumidification, cooling, and step-down.

In particular, oxygen, when coexisting with hydrogen, can cause combustion and explosion, which can greatly affect the soundness of the containment vessel, so its measurement is important for accident management.

As a prior art that can deal with such a situation, it is conceivable to apply a limit current type oxygen concentration meter using a solid electrolyte having oxygen ion conductivity. In the limit current type oxygen concentration meter, the combustion rate of hydrogen can be sufficiently reduced by adjusting the electrode material and the operating temperature, and the oxygen concentration in the storage container can be measured. On the other hand, in order for the solid electrolyte to exhibit oxygen ion conductivity, a high temperature of 400 ° C. or higher is generally required, and minute consumption of oxygen due to hydrogen combustion is unavoidable. Further, when the temperature is about 400 ° C., carbon is generated by the thermal decomposition of methyl iodide in the environment, and the generated carbon may cover the electrode portion, thereby impairing the function of the oxygen concentration meter.

The problem to be solved by the embodiment of the present invention is to use an oxygen concentration measuring device such as a limit current type oxygen concentration meter using a solid electrolyte having oxygen ion conductivity in measuring the oxygen concentration in the reactor facility. In some cases, the effects of hydrogen and iodine species are to be sufficiently small.

The oxygen concentration measuring device according to the embodiment is an oxygen concentration measuring device for measuring the oxygen concentration of the gas in the reactor storage container, and is an oxygen ion conductive solid electrolyte diaphragm arranged in the reactor storage container. And the first and second electrodes arranged in contact with the first surface of the diaphragm and the second surface opposite the first surface, respectively, and arranged in the reactor containment vessel. A hydrogen iodide generating section that produces hydrogen iodide by reacting hydrogen in the gas in the reactor storage container with an iodine species and a hydrogen iodide generating section that collects hydrogen iodide in the gas that flows out from the hydrogen iodide generating section. The gas that has passed through the hydrogen iodide filter is in direct contact with the first surface of the diaphragm and is not in direct contact with the second surface of the diaphragm. It is characterized by being configured.

The reactor facility according to the embodiment is a reactor facility including a reactor storage container and an oxygen concentration measuring device for measuring the oxygen concentration of gas in the reactor storage container, and the oxygen concentration measuring device. Is placed in contact with the oxygen ion conductive solid electrolyte diaphragm placed in the reactor containment vessel and the first surface of the diaphragm and the second surface opposite the first surface, respectively. Hydrogen iodide generation that produces hydrogen iodide by reacting the first and second electrodes, which are arranged in the reactor storage container, with hydrogen in the gas in the reactor storage container and iodine species. The gas having a hydrogen iodide filter and a hydrogen iodide filter for collecting hydrogen iodide in the gas flowing out from the hydrogen iodide generation section, and the gas passing through the hydrogen iodide filter is the first gas of the diaphragm. It is characterized in that it is configured to be in direct contact with a surface and not in direct contact with the second surface of the diaphragm.

According to the embodiment of the present invention, when measuring the oxygen concentration in the reactor facility, when an oxygen concentration measuring device such as a limit current type oxygen concentration meter using a solid electrolyte having oxygen ion conductivity is used, hydrogen is used. And the effects of oxygen species can be reduced sufficiently.

The cross-sectional view which shows the structure of the oxygen concentration measuring apparatus which concerns on 1st Embodiment of this invention. The schematic vertical sectional view of the boiling water reactor facility which shows the installation state of the oxygen concentration measuring apparatus which concerns on 1st Embodiment of this invention. The cross-sectional view which shows the structure of the oxygen concentration measuring apparatus which concerns on 2nd Embodiment of this invention. The cross-sectional view which shows the structure of the oxygen concentration measuring apparatus which concerns on 3rd Embodiment of this invention. The cross-sectional view which shows the structure of the oxygen concentration measuring apparatus which concerns on 4th Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Here, common reference numerals are given to parts that are the same as or similar to each other, and duplicate description is omitted.

[First Embodiment]
FIG. 1 is a cross-sectional view showing the configuration of the oxygen concentration measuring device according to the first embodiment of the present invention. FIG. 2 is a schematic vertical sectional view of a boiling water reactor facility showing an installation status of the oxygen concentration measuring device according to the first embodiment.

The oxygen concentration measuring device of the first embodiment is a limit current type oxygen concentration measuring device using oxygen pumping.

This oxygen concentration measuring device has an oxygen sensor unit 12 installed in the reactor containment vessel 11 and a control / monitoring unit 13 installed in a control room (not shown) outside the reactor containment vessel 11. .. The oxygen sensor unit 12 and the control / monitoring unit 13 are electrically connected by a cable 14, and the cable 14 penetrates the wall of the reactor containment vessel 11 through the penetration portion 14a.

As shown in FIG. 2, in a boiling water reactor facility, the reactor containment vessel 11 has a dry well 90 and a wet well 91. The dry well 90 and the wet well 91 are connected by a vent pipe 92. A reactor pressure vessel 93 is arranged in the dry well 90. The pressure suppression pool 94 is housed in the wet well 91. The oxygen sensor unit 12 is arranged, for example, on the upper part of the dry well 90 and the upper part of the wet well 91.

As shown in FIG. 1, the oxygen sensor unit 12 includes an oxygen ion conductive diaphragm 15 having a first surface 15a and a second surface 15b. The first electrode 16 is attached to the first surface 15a of the diaphragm 15, and the second electrode 17 is attached to the second surface 15b of the diaphragm 15. An inspection chamber cover 18 is attached so as to cover the entire first electrode 16 and at least a part of the first surface 15a of the diaphragm 15, and covers the first electrode 16 and the first surface 15a of the diaphragm 15. The chamber 19 is formed. The second surface 15b and the second electrode 17 of the diaphragm 15 are not in direct contact with the laboratory 19. A diffusion hole 20 is formed in the examination room cover 18.

The control / monitoring unit 13 includes a DC power supply 25, an ammeter 26, and a voltmeter 27. The DC power supply 25 is connected to the first electrode 16 and the second electrode 17, and a voltage is applied so that the first electrode 16 side has a negative potential and the second electrode 17 has a positive potential. The ammeter 26 is connected to measure the current flowing through the first electrode 16 and the second electrode 17, and the voltmeter 27 is connected to measure the voltage applied to the first electrode 16 and the second electrode 17. ing.

The oxygen sensor unit 12 has a diaphragm heater 30 for heating the diaphragm 15 and a diaphragm thermometer 31 for measuring the temperature of the diaphragm 15. The control / monitoring unit 13 includes a diaphragm heater power supply 35 that supplies electric power to the diaphragm heater 30, and a diaphragm temperature control unit 36 that controls the temperature of the diaphragm 15 within a predetermined range.

A hydrogen iodide filter 40 is arranged so as to cover the diffusion hole 20 on the outside of the inspection chamber 19, and a hydrogen iodide generation unit 41 is formed on the opposite side of the diffusion hole 20 adjacent to the hydrogen iodide filter 40. A hydrogen iodide generation unit heater 42 for heating the hydrogen iodide generation unit 41 and a hydrogen iodide generation unit thermometer 43 for measuring the temperature of the hydrogen iodide generation unit 41 are attached to the hydrogen iodide generation unit 41. Has been done. The control / monitoring unit 13 controls the temperature of the hydrogen iodide generation unit heater power supply 45 that supplies power to the hydrogen iodide generation unit heater 42 and the temperature of the hydrogen iodide generation unit 41 within a predetermined range. It has a control unit 46.

The gas G1 in the reactor containment vessel 11 to be measured by this oxygen concentration measuring device flows into the hydrogen iodide generation unit 41. In the hydrogen iodide generation unit 41, iodine in the gas and iodine species other than hydrogen iodide are changed to hydrogen iodide. The gas G2 that has passed through the hydrogen iodide generation unit 41 passes through the hydrogen iodide filter 40, at which time hydrogen iodide in the gas is collected (for example, adsorbed), and the remaining gas G3 passes through the diffusion hole 20. It flows into the examination room 19.

Oxygen gas among the gases in the examination chamber 19 changes to oxygen ions when it comes into contact with the first electrode 16, and the oxygen ions move in the diaphragm 15 toward the second electrode 17 (arrow a in the figure). ). Oxygen ions change from oxygen ions to oxygen gas again at the second electrode 17. By measuring the electric signal generated at this time, it is possible to measure the oxygen concentration or the oxygen partial pressure.

The diaphragm 15 is an oxygen ion conductive type solid electrolyte having oxygen ion conductivity at least at 525 ° C. or lower. Examples of the material of the diaphragm 15 include zirconia-based materials such as yttria-stabilized zirconia (YSZ) and scandia-stabilized zirconia (ScSZ), as well as perovskite-type oxygen ion conductors such as lanthanum strontium gallate, and gadolinium-doped ceria (gadolinium-doped ceria). Examples include ceria-based materials such as GDC). 525 ° C. is the natural combustion start temperature of hydrogen in an atmospheric pressure and an air environment (oxygen concentration of about 20%).

The materials used for the first and second electrodes 16 and 17 are a metal material generally used as a conductor, an oxide electrode used for a solid oxide fuel cell (SOFC), and a composite material of an oxide and a metal. Cermet materials can be used.

The hydrogen iodide generation unit 41 has a space for heating the gas G1 in the reactor containment vessel 11 to 200 ° C. to 400 ° C. by the hydrogen iodide generation unit heater 42. The lower limit of 200 ° C. is significantly higher than the temperature inside the containment vessel assumed at the time of the accident, and is a temperature at which the generation rate of hydrogen iodide can be controlled regardless of the temperature inside the containment vessel. Further, the upper limit of 400 ° C. is an upper limit temperature that does not affect the oxygen concentration detection on the diaphragm 15.

The hydrogen iodide filter 40 is filled with a porous body containing an inorganic substance as a main component for adsorbing hydrogen iodide, and the porosity of the porous body at that time is preferably 0.4 to 0. It is about 76. More preferably, the porous body is preferably a basic or amphoteric porous body, specifically, activated carbon modified with a basic brick containing MgO as a main component, alumina, an alkali metal or an alkaline earth metal. And zeolite. It is also possible to fill with a metal such as silver, but if it is filled with pure metal as it is, hydrogen iodide reacts with the metal to generate hydrogen, so it is modified to zeolite before use.

As described above, according to the first embodiment, when the oxygen concentration in the reactor containment vessel 11 is measured by using the limit current type oxygen concentration meter, it is contained in the gas in the reactor containment vessel 11. The hydrogen and iodine species are converted into hydrogen iodide by the hydrogen iodide generation unit 41 and collected by the hydrogen iodide filter 40. This makes it possible to sufficiently reduce the adverse effects of hydrogen and iodine species on the faradaic current oxygen concentration meter.

[Second Embodiment]
FIG. 3 is a cross-sectional view showing the configuration of the oxygen concentration measuring device according to the second embodiment of the present invention. This second embodiment is a modification of the first embodiment, in which the hydrogen iodide generating section 41 is filled with a porous body 50 containing an inorganic substance as a main component. The porosity of the porous body 50 is preferably 0.4 to 0.76. More preferably, the porous body is preferably a porous body having basic or amphoteric properties, and specifically, it is modified with a basic brick containing MgO as a main component, alumina, an alkali metal or an alkaline earth metal. Examples include activated charcoal and zeolite.

The configuration other than the above is the same as that of the first embodiment.

According to this second embodiment, hydrogen iodide generation unit 41 is filled with a porous body 50 to increase the specific heat capacity of the hydrogen iodide generation unit 41 and the contact area with gas to generate hydrogen iodide. The gas passing through the unit 41 can be heated more efficiently, and the volume of the hydrogen iodide generating unit 41 can be reduced. Moreover, the same effect as that of the first embodiment can be obtained.

[Third Embodiment]
FIG. 4 is a cross-sectional view showing the configuration of the oxygen concentration measuring device according to the third embodiment of the present invention. This third embodiment is a modification of the first embodiment, and has a structure in which a hydrogen iodide generating section 41 is filled with a catalyst 51 containing an inorganic substance as a main component. The catalyst 51 is composed of a honeycomb made of an inorganic oxide or a spherical or columnar pellet in which platinum group atoms are dispersed. At that time, the amount of the platinum group supported is preferably 0.1 to 5% by weight based on the total weight of the catalyst.

According to this third embodiment, the hydrogen iodide generation unit 41 is filled with the catalyst 51 to reduce the activation energy for hydrogenation of hydrogen and iodine, thereby reducing the temperature and time required for the reaction. It is possible to reduce the volume of the hydrogen iodide producing unit 41. Moreover, the same effect as that of the first embodiment can be obtained.

[Fourth Embodiment]
FIG. 5 is a cross-sectional view showing the configuration of the oxygen concentration measuring device according to the fourth embodiment of the present invention. The first to third embodiments described above are the critical current type oxygen concentration measuring device, but the fourth embodiment is the shading type oxygen concentration measuring device.

This oxygen concentration measuring device has an oxygen sensor unit 12 installed in the reactor containment vessel 11 and a control / monitoring unit 13 installed in a control room (not shown) outside the reactor containment vessel 11. .. The oxygen sensor unit 12 and the control / monitoring unit 13 are electrically connected by a cable 14, and the cable 14 penetrates the wall of the reactor containment vessel 11 through the penetration portion 14a.

The oxygen sensor unit 12 includes an oxygen ion conductive diaphragm 15 having a first surface 15a and a second surface 15b. The first electrode 16 is attached to the first surface 15a of the diaphragm 15, and the second electrode 17 is attached to the second surface 15b of the diaphragm 15.

A reference gas chamber cover 61 is attached to the second surface 15b and the second electrode 17 of the diaphragm 15 so as to be in contact with the reference gas chamber 60. The reference gas chamber cover 61 is, for example, a pipe through which a reference gas flows, and the reference gas chamber 60 holds a reference gas having a known oxygen concentration. Here, the oxygen concentration of the reference gas is assumed to be lower than the oxygen concentration in the reactor containment vessel 11 for which the oxygen concentration is to be measured. The first surface 15a and the first electrode 16 of the diaphragm 15 are not in direct contact with the reference gas chamber 60.

The control / monitoring unit 13 includes a voltmeter 63, and is connected so that the voltage between the first electrode 16 and the second electrode 17 can be measured by the voltmeter 63.

The structure of the diaphragm 15, the first electrode 16, and the second electrode 17 is the same as that of the first embodiment. Further, a hydrogen iodide filter 40, a hydrogen iodide generation unit 41, a hydrogen iodide generation unit heater 42, a hydrogen iodide generation unit thermometer 43, a hydrogen iodide generation unit heater power supply 45, and a hydrogen iodide generation unit temperature control unit 46. The configuration of is the same as that of the first embodiment. However, the hydrogen iodide filter 40 is arranged so as to cover at least a part of the first surface 15a and the first electrode 16 of the diaphragm 15, and is different from the second surface 15b and the second electrode 17 of the diaphragm 15. Not in direct contact. Although the diaphragm heater 30, the diaphragm thermometer 31, the diaphragm heater power supply 35, and the diaphragm temperature control unit 36 (FIG. 1) are not shown in FIG. 5, they may be arranged in the same manner as in the first embodiment.

In this fourth embodiment, the gas G1 in the reactor containment vessel 11 flows into the hydrogen iodide generation unit 41. In the hydrogen iodide generation unit 41, iodine in the gas and iodine species other than hydrogen iodide are changed to hydrogen iodide. The gas G2 that has passed through the hydrogen iodide generation unit 41 passes through the hydrogen iodide filter 40, at which time hydrogen iodide in the gas is collected, and the oxygen gas of the remaining gas is transferred to the first electrode 16. Upon contact, it changes to oxygen ions, and the oxygen ions move in the diaphragm 15 toward the second electrode 17 (arrow a in the figure). Oxygen ions change from oxygen ions to oxygen gas again at the second electrode 17.

A positive voltage is generated in the first electrode 16 and a negative voltage is generated in the second electrode 17 due to the flow of oxygen ions. Therefore, this voltage is measured by the voltmeter 63. Since this voltage changes depending on the difference between the oxygen concentration of the gas G1 in the reactor storage container 11 and the oxygen concentration of the gas in the reference gas chamber 60, the oxygen concentration of the gas G1 in the reactor storage container 11 is derived from this voltage. Can be measured.

As described above, according to the fourth embodiment, when the oxygen concentration in the reactor containment vessel 11 is measured by using the concentration type oxygen concentration meter, it is contained in the gas in the reactor containment vessel 11. Hydrogen and iodine species are converted into hydrogen iodide by the hydrogen iodide generation unit 41 and collected by the hydrogen iodide filter 40. This makes it possible to sufficiently reduce the adverse effects of hydrogen and iodine species on the light and shade oxygen concentration meter.

[Other embodiments]
In the fourth embodiment, the configuration of the hydrogen iodide generation unit 41 is the same as that of the first embodiment, but as another example, the configuration of the hydrogen iodide generation unit 41 of the fourth embodiment is the second. Alternatively, it may be the same as that of the third embodiment.

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 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 variations thereof are included in the scope of the invention described in the claims and the equivalent scope thereof, as are included in the scope and gist of the invention.

11 ... Reactor storage container, 12 ... Oxygen sensor unit, 13 ... Control / monitoring unit, 14 ... Cable, 14a ... Penetration part, 15 ... Diaphragm, 15a ... First surface, 15b ... Second surface, 16 ... Second surface 1 electrode, 17 ... 2nd electrode, 18 ... Examination room cover, 19 ... Examination room, 20 ... Diffuse hole, 25 ... DC power supply, 26 ... Current meter, 27 ... Voltage meter, 30 ... Diaphragm heater, 31 ... Diaphragm Thermometer, 35 ... diaphragm heater power supply, 36 ... diaphragm temperature control unit, 40 ... hydrogen iodide filter, 41 ... hydrogen iodide generator, 42 ... hydrogen iodide generator heater, 43 ... hydrogen iodide generator thermometer, 45 ... Hydrogen iodide generator heater power supply, 46 ... Hydrogen iodide generator temperature control unit, 50 ... Porous body, 51 ... Catalyst, 60 ... Reference gas chamber, 61 ... Reference gas chamber cover, 63 ... Voltage meter, 90 … Drywell, 91… Wetwell, 92… Vent tube, 93… Reactor pressure vessel, 94… Pressure suppression pool

Claims (12)

An oxygen concentration measuring device that measures the oxygen concentration of gas in the reactor containment vessel.
An oxygen ion-conducting solid electrolyte diaphragm placed in the reactor containment vessel and
The first and second electrodes arranged in contact with the first surface of the diaphragm and the second surface opposite the first surface, respectively.
A hydrogen iodide generating unit, which is arranged in the reactor containment vessel and reacts hydrogen in the gas in the reactor containment vessel with an iodine species to generate hydrogen iodide.
A hydrogen iodide filter that collects hydrogen iodide in the gas flowing out from the hydrogen iodide generation unit,
Have,
Oxygen characterized in that the gas that has passed through the hydrogen iodide filter is configured to be in direct contact with the first surface of the diaphragm and not in direct contact with the second surface of the diaphragm. Density measuring device. The oxygen concentration measuring device according to claim 1, further comprising a hydrogen iodide generating unit heater for heating the hydrogen iodide generating unit. The oxygen concentration measuring device according to claim 2, further comprising a hydrogen iodide generating section thermometer for measuring the temperature of the hydrogen iodide generating section. The third aspect of claim 3, further comprising a hydrogen iodide generation unit temperature control unit that controls the hydrogen iodide generation unit heater so that the temperature of the hydrogen iodide generation unit thermometer is within a predetermined range. Oxygen concentration measuring device. The oxygen concentration measuring apparatus according to any one of claims 1 to 4, further comprising a diaphragm heater for heating the diaphragm. Diffusion that forms an inspection chamber covering at least a part of the first electrode and at least a part of the first surface of the diaphragm, and gas passing through the hydrogen iodide filter passes through and flows into the inspection chamber. The laboratory cover with holes and
A DC power supply that applies a voltage to the first and second electrodes so that the second electrode has a positive voltage with respect to the first electrode.
An ammeter that measures the current flowing through the first and second electrodes,
A voltmeter that measures the voltage applied to the first and second electrodes,
The oxygen concentration measuring device according to any one of claims 1 to 5, further comprising. Further having a voltmeter measuring the voltage between the first electrode and the second electrode.
A reference gas chamber for accommodating a reference gas having a controlled oxygen concentration is formed, and the reference gas in the reference gas chamber is in direct contact with at least a part of the second surface of the diaphragm and the first of the diaphragm. The oxygen concentration measuring device according to any one of claims 1 to 5, wherein the oxygen concentration measuring device is configured so as not to come into direct contact with the surface of 1. The oxygen concentration measuring device according to any one of claims 1 to 7, wherein the hydrogen iodide filter contains at least one of activated carbon, basic brick, alumina, and zeolite. The oxygen concentration measuring device according to any one of claims 1 to 8, wherein the hydrogen iodide generating unit is filled with a porous body. The oxygen concentration measuring device according to claim 9, wherein the porous body contains any one of basic brick, alumina, and zeolite. The oxygen concentration measuring device according to claim 9, wherein the porous body is filled with a filling material containing a platinum group atom. Reactor containment vessel and
An oxygen concentration measuring device that measures the oxygen concentration of the gas in the reactor containment vessel,
It is a nuclear reactor facility equipped with
The oxygen concentration measuring device is
An oxygen ion-conducting solid electrolyte diaphragm placed in the reactor containment vessel and
The first and second electrodes arranged in contact with the first surface of the diaphragm and the second surface opposite the first surface, respectively.
A hydrogen iodide generating unit, which is arranged in the reactor containment vessel and reacts hydrogen in the gas in the reactor containment vessel with an iodine species to generate hydrogen iodide.
A hydrogen iodide filter that collects hydrogen iodide in the gas flowing out from the hydrogen iodide generation unit,
Have,
An atom characterized in that the gas that has passed through the hydrogen iodide filter is configured so as to be in direct contact with the first surface of the diaphragm and not in direct contact with the second surface of the diaphragm. Reactor facility.

Images