JP4585333B2 - Hydrogen concentration meter - Google Patents

Description

  The present invention relates to a hydrogen concentration meter suitable for use in accurately detecting that water has leaked into liquid sodium used as a coolant for a fast breeder reactor.

  As is well known, high-purity liquid sodium is used as a coolant in a fast breeder reactor. The liquid sodium in this case is cooled by heating water with an evaporator or a heater after being heated in a nuclear reactor. Liquid sodium is very chemically reactive, so careful attention must be paid to its leakage. In particular, water intrusion into sodium in evaporators and heaters where heat exchange is performed can cause serious damage to the equipment, so monitoring is the most important safety management for fast breeder reactor equipment. ing.

  Conventionally, in a fast breeder reactor facility, a hydrogen concentration meter is used to detect water leakage into the liquid sodium. This hydrogen concentration meter is a detector configured to detect the leakage of water by detecting this hydrogen because when sodium leaks into sodium, the sodium and water immediately react to generate hydrogen.

  As a hydrogen concentration meter having such a configuration, for example, a hydrogen concentration meter having a structure as shown in FIG. 5 has been proposed (Patent Document 1). In this hydrogen concentration meter, first, a sampling bypass 1011 in which sodium is present and a vacuum chamber 1012 are partitioned by a membrane 1013 having hydrogen permeability, such as nickel, platinum, palladium, or the like. Inside the vacuum chamber 1012, a filament 1015 for thermionic emission, a shield electrode 1016, and a collector electrode 1017 are provided. The diaphragm 1013 is grounded, and an impact voltage 1019 is applied between the diaphragm 1013 and the filament 1015. An electron blocking voltage 1020 is applied between the filament 1015 and the shield electrode 1016. An ammeter 1018 is connected between the collector electrode 1017 and ground.

  In the hydrogen concentration meter, hydrogen atoms immediately after the hydrogen generated on the sodium side permeates to the vacuum side through the diaphragm 1013 is separated from the diaphragm 1013 by electron impact, and this is accelerated by the shield electrode 1016 and collected by the collector electrode 1017. Is done. By detecting the collector electrode 1017 when this hydrogen is collected, it can be known that hydrogen has been generated in the liquid sodium.

Japanese Unexamined Patent Publication No. 7-55735

  However, since the conventional hydrogen concentration meter measures the amount of hydrogen diffused in the diaphragm 1013 and moved to the vacuum chamber 1012, the measurement speed depends on the hydrogen diffusion speed in the diaphragm 1013. Since the hydrogen diffusion rate in the diaphragm is relatively slow, it takes time to detect hydrogen. That is, the responsiveness at the time of measurement is poor. Moreover, since the vacuum chamber 1012 is indispensable for the measurement, apparatus elements such as a vacuum chamber 1012 and a vacuum drawing device for maintaining the inside of the vacuum chamber 1012 in a vacuum state are necessary, and installation costs and operation costs are incurred. Also, the installation space cannot be reduced. Furthermore, since the diaphragm 1013 is always in contact with liquid sodium, it tends to deteriorate, and the cost for replacement becomes a problem.

  The present invention has been made in view of the above, and the problem is that the response speed is fast, the structure is simple, the installation space is small, both the installation cost and the operation cost are low, and the corrosion resistance to liquid sodium is high. Another object of the present invention is to provide a hydrogen concentration meter having excellent strength characteristics.

In order to solve the above-described problems, a hydrogen concentration meter according to the present invention is a hydrogen concentration meter that detects a hydrogen concentration in liquid sodium flowing through a liquid sodium flow path, and has an inner side in contact with a reference hydrogen gas and an outer side. A solid electrolyte membrane in contact with the liquid sodium, electrodes attached to the inside and outside of the solid electrolyte membrane, and a voltmeter for measuring an electromotive force between the inner electrode and the outer electrode, respectively. a, the solid electrolyte _{membrane, SrZr 0.95 Y 0.05 O 3,} CaZr 0.95 Yb 0.05 O 3, SrZr 0.95 Yb 0.05 O 3, CaZr 0.95 Al 0.05 O 3, SrZr 0.95 Al 0.05 O 3, SrZr 0.95 In 0.05 O 3 And a kind of solid electrolyte material selected from the group consisting of SrZr _0.95 Sm _0.05 O ₃ .

  The solid electrolyte membrane is preferably formed in a cylindrical shape with a bottom, filled or circulated with a reference hydrogen gas atmosphere, and inserted into a bypass channel of the sodium channel when used for detection. Thereby, the outside of the solid electrolyte membrane comes into contact with liquid sodium. Therefore, the structure is simple and installation space is small. In addition, the detection of hydrogen in sodium is obtained by measuring the electromotive force generated from the difference between the reference hydrogen amount inside the solid electrolyte membrane and the hydrogen abundance outside, so hydrogen diffusion in the membrane is unnecessary, The measurement response speed becomes very fast.

In the hydrogen concentration meter of the present invention, when hydrogen is present in liquid sodium, the electromotive force generated when the hydrogen becomes ions and permeates the solid electrolyte membrane to the reference hydrogen gas atmosphere side is measured. Also in the conventional hydrogen concentration meter, hydrogen atoms migrate through the partition wall, and it enters the measurement vacuum chamber to measure the gasified hydrogen. Therefore, an accurate hydrogen concentration cannot be measured in a state where a certain amount of hydrogen does not permeate. Since hydrogen permeation through a conventional diaphragm allows only gaseous hydrogen to permeate and does not allow other gases to permeate, the diaphragm used is a dense film and has a very low gas permeation rate. As a result, it takes time to permeate hydrogen gas. In contrast, in the present invention, hydrogen ions are permeated instead of gaseous hydrogen. Since hydrogen ions permeate the solid electrolyte membrane, an electromotive force is generated between both sides of the solid electrolyte membrane. The hydrogen concentration on the hydrogen ion migration source side is measured by measuring the electric power. Therefore, in the measurement method of the present invention, the movement of hydrogen in the membrane is permeation as hydrogen ions, and since a solid electrolyte membrane that is a material having high hydrogen ion conductivity is used, the permeation of hydrogen ions is rapid. The measurement time is not delayed.

  When the solid electrolyte membrane is composed of the perovskite type compound, the corrosion resistance against liquid sodium is increased, the life as a hydrogen concentration meter can be greatly extended, and the physical hardness can be improved.

As the perovskite-type compound, a SrZrO ₃ -based perovskite-type compound is used, and by doping any of Y, Yb, and In with this compound, the corrosion resistance against liquid sodium can be further improved.
In the present invention, the solid electrolyte membrane is most preferably composed of SrZr _0.95 Yb _0.05 O ₃ .

  The hydrogen concentration meter according to the present invention has a high response speed, a simple structure, a small installation space, a low installation cost and an operating cost, high corrosion resistance against liquid sodium, and excellent strength characteristics.

  Embodiments of the hydrogen concentration meter according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  FIG. 1 shows a schematic configuration of a hydrogen concentration meter according to the present invention, and shows a state in which the hydrogen concentration meter of the present invention is inserted and installed in a flow channel pipe 2 through which liquid sodium 1 flows.

  As shown in FIG. 1, the hydrogen concentration meter according to Example 1 includes a bottomed cylindrical solid electrolyte membrane 4 in which a reference hydrogen gas atmosphere 3 is filled or circulated, and an inner side of the solid electrolyte membrane 4. And electrodes 5 and 6 attached to the outside respectively, and a voltmeter 7 for measuring an electromotive force between the inside electrode (hereinafter referred to as a reference electrode) 5 and the outside electrode 6. The electrodes 5 and 6 are connected to the voltmeter 7 by platinum lead wires 8 and 9 whose surfaces are insulated. The bottomed cylindrical solid electrolyte membrane 4 is fixed to the support 11 via an insulating material 10 at the top.

  The bottomed cylindrical solid electrolyte membrane 4 is filled or circulated with the reference hydrogen gas 3 inside as described above, and is inserted into the liquid sodium channel tube 2 when used for detection. Thereby, the outside of the solid electrolyte membrane 4 comes into contact with the liquid sodium 1.

The hydrogen concentration meter of the first embodiment does not require a troublesome mechanism such as a vacuum chamber or a vacuum evacuation device, is simple in structure, and requires a small installation space. In addition, detection of whether or not water is leaking into the liquid sodium 1 is performed by the following formula (1) when water leaks into the liquid sodium 1.
2Na + H ₂ O → Na ₂ O + H ₂ (1)
According to the reaction shown in the above, hydrogen is generated in the liquid sodium 1, and the leakage of water is detected by measuring the hydrogen concentration. The measurement is obtained by directly measuring the electromotive force generated from the difference between the reference hydrogen amount inside the solid electrolyte membrane 4 and the hydrogen existing amount outside using the electrodes 5 and 6 and the voltmeter 7. Therefore, unlike the conventional hydrogen concentration meter, the measurement speed does not depend on the hydrogen gas diffusion speed in the film, and the measurement response speed becomes very fast.

  Hydrogen in the liquid sodium 1 becomes hydrogen ions and permeates through the solid electrolyte membrane 4 to generate an electromotive force, which is measured by the electrodes 5 and 6 and the voltmeter 7, whereby hydrogen in the sodium 1 The concentration is measured. This measurement principle will be described in more detail below to clarify the difference from the prior art.

That is, by the reaction shown in the formula (1), hydrogen generated in the liquid sodium, emits electrons at the surface of the solid electrolyte film 4, it passes through the solid electrolyte membrane 4 medium become hydrogen ions (H ⁺⁾ . Since the permeation is performed on the solid electrolyte membrane 4 having a high ionic conductivity as described above, it is rapid. The emitted electrons flow from the electrode 6 through the voltmeter 7 to the electrode 5 provided inside the solid electrolyte membrane 4 (reference hydrogen gas atmosphere 3). On the other hand, the hydrogen ions that have passed through the solid electrolyte membrane 4 escape to the reference hydrogen gas atmosphere 3 side, and take electrons from the electrode 5 to become hydrogen gas. By this series of permeation of hydrogen ions, an electromotive force is generated between the liquid sodium side of the solid electrolyte membrane 4 and the reference hydrogen atmosphere 3 side inside the solid electrolyte membrane 4. This electromotive force is generated between the outer electrode 6 and the inner electrode 5 and is measured by a voltmeter 7. The concentration of hydrogen generated in the liquid sodium 1 can be measured by this electromotive force value. This hydrogen concentration can be easily converted to water leaked into sodium by the above formula (1). Therefore, it can be measured how much the amount of leakage is that water has leaked into sodium.

When hydrogen ions permeate through the solid electrolyte membrane 4, an electromotive force is generated between the outside (electrode 6) and the inside (electrode 5) of the solid electrolyte membrane 4. This is explained by the following equation.
E = (R · T / 2F) × In (P _H2 (in standard hydrogen atmosphere) / P _H2 (in Na))
In the formula, P _H2 (reference): hydrogen partial pressure (atm) of the reference hydrogen gas atmosphere
P _H2 (in Na): hydrogen concentration in liquid sodium (atm)
E: Electromotive force (V)
F: Faraday constant (96485 C / mol)
R: Gas constant T: Absolute temperature (K)

The hydrogen ions permeate through the solid electrolyte membrane 4 because hydrogen ion vacancies are generated in the solid electrolyte compound. This principle will be described using CaZr _0.9 In _0.1 O ₃ as the solid electrolyte material. This fixed electrolyte material can be obtained by adding In (trivalent rare earth element) as a dopant to the matrix (CaZrO ₃ ). As a result of the doping, a part of tetravalent Zr is replaced with trivalent In. become. As a result of this substitution, as is well known , hydrogen ion vacancies are generated in order to satisfy the electrical neutralization condition inside the solid. Since the hydrogen ion vacancies are scattered inside the solid, hydrogen ions from the outside of the solid electrolyte can propagate through the solid and permeate to the other side by using the hydrogen ion vacancy as a bridge. In this way, the hydrogen ion vacancies serve as a bridge, and hydrogen ions permeate from one side to the other, so that the permeation speed is rapid.

In the present invention, an electrode 6 is provided on the liquid sodium 1 side outside the solid electrolyte membrane 4, and an electrode 5 is provided on the inner reference hydrogen gas atmosphere 3 side. These electrodes are connected via a voltmeter 7. Yes. Therefore, as described above, there is a concentration difference between hydrogen in the outer liquid sodium 1 and the hydrogen ion concentration (reference concentration) on the inner side. As described above, the outer hydrogen emits electrons, and ions and As a result, it quickly permeates through the solid electrolyte membrane 4, moves into the reference atmosphere, takes electrons, and becomes hydrogen gas. At this time, an electromotive force is generated. Since this electromotive force value is proportional to the hydrogen concentration generated in the liquid sodium, the hydrogen concentration can be measured. This hydrogen concentration is converted into the leaked water by the equation (1) as described above. In the present invention, since the principle is to measure the difference in electromotive force between both sides of the solid electrolyte membrane 4, the solid electrolyte membrane 4 is connected to the channel tube 2 and the support 11 through an insulating material. It is fixed to.

  Since the solid electrolyte membrane 4 is always in contact with the liquid sodium 1 while being used to detect leakage of water into the liquid sodium, the solid electrolyte membrane 4 needs to have excellent corrosion resistance against the liquid sodium 1. In the present invention, a perovskite type compound is specified as a material constituting the solid electrolyte membrane 4, and experiments and studies leading to the specification are shown in Example 2 below.

As candidate materials for the solid electrolyte membrane 4 having the above-described structure, various types of solid electrolyte materials known to have hydrogen ion conductivity are selected, and these are formed into pellets (a circle having a thickness of 1.0 mm and a diameter of 20.0 mm). After being formed into a plate), it was immersed in liquid sodium at 380 ° C. in an N ₂ gas atmosphere as an inert gas for 1000 hours. This temperature setting of 380 ° C. is because liquid sodium used as a coolant in the fast breeder reactor facility is placed at 330 ± 50 ° C. Therefore, if no corrosion is observed in a long-time immersion test at 380 ° C. exceeding 1000 hours, it is considered that the solid electrolyte membrane 4 constituting the hydrogen concentration meter of the present invention functions sufficiently.

As a result of the immersion test over 1000 hours, it was determined that a CaZrO ₃ -based perovskite-type compound and a SrZrO ₃ -based perovskite-type compound are suitable as the matrix of the material constituting the solid electrolyte membrane 4. In the present invention, specific materials are specified from these material matrices. Experiments and examinations that enable the specification are shown in Example 3 below.

Since the solid electrolyte material suitable as the solid electrolyte membrane 4 is determined to be suitable for the matrix, the CaZrO ₃ -based perovskite type compound and the SrZrO ₃ -based perovskite type compound have a specific composition capable of further improving performance. investigated. La, Y, Yb, Nb, Al, In, Ni, Mn, and Sm were added as dopants to the matrix to obtain 17 solid electrolyte material samples in Table 1 below. The sample shape was in the form of pellets (thickness 1.0 mm × diameter 20.0 mm disk).

  These 17 solid electrolyte material samples were immersed in liquid sodium at 380 ° C. in a nitrogen atmosphere for 300 hours in the same manner as in Example 2, and the weight before immersion and the weight after immersion were compared. The results are shown in FIG. In the graph of FIG. 2, the vertical axis indicates the weight change rate. As can be seen from FIG. 2, there are those that are swollen by immersion and increased in weight, and those that are dissolved in liquid sodium and reduced in weight. For both changes in weight increase and weight decrease, those within ± 1.0% were judged as suitable materials. In FIG. 2, the weight change rate is not shown for samples 1, 7, 8, 12, 13, 14, 15 and 16, but this is because they are dissolved in liquid sodium or significantly corroded. It is because it deteriorated so as not to be measured.

Those exceeding ± 1.0% are shown in Table 1 with “×” and those within ± 1.0% as “◯”. That is, the specific perovskite type compounds excellent in corrosion resistance against liquid sodium are SrZrO ₃ -based perovskite type compounds, SrZr _0.95 La _0.05 O ₃ (sample 2), SrZr _0.95 Y _0.05 O ₃ (sample 4), SrZr _0.95 Yb _0.05 6 points of O ₃ (sample 6), SrZr _0.95 Al _0.05 O ₃ (sample 10), SrZr _0.95 In _0.05 O ₃ (sample 11), SrZr _0.95 Sm _0.05 O ₃ (sample 17), and a CaZrO ₃ -based perovskite compound Then, it was two points of CaZr _0.95 Yb _0.05 O ₃ (sample 5) and CaZr _0.95 Yb _0.05 O ₃ (sample 9).

Ten samples were prepared by adding two samples of CaZrO ₃ and SrZrO ₃ to eight samples 4, 5, 6, 9, 10, 11, and 17 in which good sodium corrosion resistance was confirmed in Example 3. Sample 2, which had good sodium corrosion resistance, contains lanthanum and is very difficult to handle in production. Therefore, it is excluded, and instead, it is inferior to long-term corrosion resistance, but short-term corrosion resistance is a problem. Sample 3 judged not to be used was used. A list of these sample configurations is shown in Table 2. These sample shapes were pellets (thickness 1.0 mm × diameter 20.0 mm disk). The hydrogen concentration detection characteristics of these 10 samples were measured.

  A hydrogen circulation chamber that is airtightly isolated from each other is formed on opposite side surfaces of each of the disk-shaped samples, and a hydrogen gas of 50 ppm as a reference hydrogen concentration continues to flow into one hydrogen circulation chamber, and the other hydrogen circulation chamber 5% hydrogen gas continued to flow. The environmental temperature was set in two ways, 500 ° C. and 300 ° C. The setting of 300 ° C. assumes a temperature at which liquid sodium used as a coolant for a fast breeder reactor facility is normally placed, and the setting of 500 ° C. is liquid sodium also used as a coolant for a fast breeder reactor. Is assumed to be instantaneously hot. Therefore, it is said that a material having better characteristics under both temperature environments is a preferable material.

  In the measurement configuration, hydrogen ions permeate each sample from a hydrogen gas circulation chamber in which 5% concentration hydrogen gas flows to a hydrogen gas circulation chamber in which 50 ppm of hydrogen gas flows. With this transmission, an electromotive force is generated between the opposite side surfaces of the sample. This electromotive force and its S / N ratio were measured. The measurement results are shown in FIG. 3 (500 ° C.) and FIG. 4 (300 ° C.). The white bar graph is the voltage measurement value, and the solid bar graph is the S / N measurement value. At 500 ° C., all samples could be measured, but at 300 ° C., the samples 3, 4, 9, 10 were so low that they could not be measured.

From the measurement results shown in FIG. 3 and FIG. 4, the preferred materials from the viewpoint of hydrogen concentration detection characteristics are 7 samples of samples 2, 4, 5, 6, 9, 10, and 17, and 2 of CaZrO ₃ and SrZrO ₃ . With samples. These samples have excellent corrosion resistance against liquid sodium and excellent hydrogen concentration detection characteristics, and are suitable as the solid electrolyte membrane 4 constituting the hydrogen concentration meter of the present invention. Among these 9 samples, the sample 6 that showed the most excellent characteristics was SrZr _0.95 Yb _0.05 O ₃ . The results are also shown in Table 2. In Table 2, a preferred material is marked with a circle, and the most suitable material is marked with a circle.

Nine samples excellent in both corrosion resistance and hydrogen concentration detection characteristics were immersed in liquid sodium at 380 ° C. for 1000 hours and then subjected to a bending test to confirm the strength. As a result, the strength (10 to 15 kgf / cm) that can sufficiently withstand a hydrogen concentration meter. ² ) has been confirmed.

  The hydrogen concentration meter according to the present invention has a high response speed, a simple structure, a small installation space, low installation costs and operation costs, high corrosion resistance against liquid sodium, excellent strength characteristics, and high speed. It can be suitably used for a hydrogen detection apparatus for monitoring water leakage into liquid sodium used as a coolant in a breeder reactor facility.

It is a figure which shows schematic structure of the hydrogen concentration meter concerning this invention. It is a figure which shows the corrosion resistance with respect to the liquid sodium of the candidate material of the solid electrolyte membrane which is a component of the hydrogen concentration meter of this invention. It is a figure which shows the hydrogen concentration detection characteristic in 500 degreeC of the candidate material of the solid electrolyte membrane which is a component of the hydrogen concentration meter of this invention. It is a figure which shows the hydrogen concentration detection characteristic in 300 degreeC of the candidate material of the solid electrolyte membrane which is a component of the hydrogen concentration meter of this invention. It is a figure which shows the structure of the conventional hydrogen concentration meter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid sodium 2 Liquid sodium distribution pipe 3 Standard hydrogen gas atmosphere 4 Solid electrolyte membrane 5 Electrode 6 Reference electrode 7 Voltmeter 8, 9 Platinum lead wire 10 Insulation material 11 Support body

Claims (3)

A hydrogen concentration meter for detecting a hydrogen concentration in liquid sodium flowing through a liquid sodium channel,
A solid electrolyte membrane in which the inner side is in contact with the reference hydrogen gas and the liquid sodium is in contact on the outer side, electrodes attached to the inner side and the outer side of the solid electrolytic membrane, and between the inner and outer electrodes A voltmeter for measuring electromotive force,
The solid electrolyte _{membrane, SrZr 0.95 Y 0.05 O 3,} CaZr 0.95 Yb 0.05 O 3, SrZr 0.95 Yb 0.05 O 3, CaZr 0.95 Al 0.05 O 3, SrZr 0.95 Al 0.05 O 3, SrZr 0.95 In 0.05 O 3, and SrZr A hydrogen concentration meter comprising a kind of solid electrolyte material selected from the group consisting of _0.95 Sm _0.05 O ₃ . The hydrogen concentration meter according to claim 1 , wherein the solid electrolyte membrane is made of SrZr _0.95 Yb _0.05 O ₃ . Hydrogen concentration meter according to claim 1 or 2, characterized in that the solid electrolyte film is formed into a bottomed cylindrical shape.

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