JP2006058204A - Hydrogen manufacturing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrogen manufacturing device capable of making the best use of decay heat of a spent nuclear fuel. <P>SOLUTION: This device of the present invention is provided with a heat recovery means 10, a heat supply means 15, and a hydrogen generating means 20A, and the heat recovery means 10 is connected to the heat supply means 15 by flow passages 11 (11a, 11b). A container 2 storing the spent nuclear fuel is provided in an inside of the heat recovery means 10, and the decay heat radiated from he spent nuclear fuel is recovered by a heating medium S. The recovered heating medium S is fed to the heat supply means 15 via the flow passage 11b to supply heat to a reaction part 21. In the reaction part 21, a raw material is supplied from a raw material supply part 22, and hydrogen is generated using the heat of the heating medium S as a heat source in reaction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hydrogen production apparatus that produces hydrogen using decay heat of spent nuclear fuel discharged from, for example, a nuclear power plant.

  Spent nuclear fuel generated at the nuclear power plant is reprocessed, and recyclable nuclear fuel materials such as uranium and plutonium are recovered from the spent nuclear fuel. The spent nuclear fuel before recovering this recyclable nuclear fuel material releases decay heat, so that the spent nuclear fuel remains in the fuel rods until it is reprocessed. It is stored while cooling in a dedicated storage pool or intermediate storage facility. After the storage period has passed, spent nuclear fuel taken out from the fuel rods is reprocessed to recover uranium, plutonium, etc., and the rest is vitrified, and stored on the ground for a longer period of time before being disposed of.

  Conventionally, decay heat released from such spent nuclear fuel has been simply released outside without being effectively utilized. Therefore, various technologies for effectively utilizing decay heat released from spent nuclear fuel have been proposed from the viewpoint of resource conservation and energy saving. For example, Patent Documents 1 to 3 disclose the heat of spent nuclear fuel. A technique for generating electricity by using it has been proposed.

In recent years, development and popularization of fuel cells using hydrogen as fuel, such as fuel cell vehicles, have been promoted from the viewpoint of environmental protection. For this reason, the demand for hydrogen is expected to increase further in the future, and it is desired to supply hydrogen stably. As a method for producing hydrogen, it is common practice to use the heat of combustion of fossil fuel such as natural gas as a heat source during the reaction. However, when the heat of combustion of fossil fuel is used as a heat source, a problem arises in that a large amount of carbon dioxide, which causes global warming, is generated together with hydrogen. Thus, as a technique for generating hydrogen without generating carbon dioxide, for example, those described in Patent Documents 4 to 6 have been proposed.
Japanese Unexamined Patent Publication No. 2000-212297 (paragraphs 0035 to 0041, FIG. 1) Japanese Patent Laying-Open No. 2004-109013 (paragraphs 0029 and 0030) Japanese Patent Laid-Open No. 5-150099 (paragraph 0007) Japanese Patent Laid-Open No. 2002-241101 (paragraphs 0009 to 0010, FIG. 1) JP 2000-327301 A (paragraphs 0004 and 0005, FIG. 1) JP 2003-54902 A (paragraphs 0010 to 0013)

  However, in the system that generates power using the decay heat of spent nuclear fuel as described in Patent Documents 1 to 3, it is difficult to control the release of decay heat, and electricity is not a storable medium. When power generation is performed when power is required, heat is wasted when power generation is unnecessary, and decay heat cannot be used effectively.

  Further, in the system that directly uses the heat of the reactor described in Patent Document 4, the heat medium for recovering the heat of the reactor is set to a specific temperature. It becomes difficult to set a suitable temperature. In addition, Patent Documents 4 to 6 have all proposed a technique for generating hydrogen using a nuclear reactor, but have not studied any technique for effectively utilizing decay heat of spent nuclear fuel.

  The present invention solves the above-mentioned conventional problems, can effectively utilize decay heat released from spent nuclear fuel, etc., and can be adjusted to a temperature suitable for the reaction mode during hydrogen production. An object of the present invention is to provide a hydrogen production apparatus that can be used.

  The present invention includes heat recovery means for recovering heat released from spent nuclear fuel or nuclear waste that generates decay heat through a predetermined heat medium, and hydrogen using the heat recovered by the heat recovery means. Hydrogen generating means to be generated, heat supply means for supplying heat recovered by the heat recovery means to the hydrogen generating means, and a flow path for circulating the heat medium between the heat recovery means and the heat supply means Are provided.

  According to the present invention, decay heat can be effectively utilized by producing hydrogen that can be stored using decay heat generated from spent nuclear fuel.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. FIG. 1 is an overall configuration diagram showing the hydrogen production apparatus according to the first embodiment, and FIG. 2 is a sectional view showing an internal structure of the heat recovery means. In the following embodiments, a case where hydrogen is produced using decay heat of spent nuclear fuel will be described as an example.

(First embodiment)
As shown in FIG. 1, this hydrogen production apparatus 1A includes a heat recovery means 10, a flow path 11 (first flow path 11a, second flow path 11b), a circulation pump 12, and a heat supply means 15. And a hydrogen generation means 20A.

  As shown in FIG. 2, the heat recovery means 10 has a cylindrical storage portion 10a, and a plurality of containers 2 are stored in the storage portion 10a. The container 2 has a cylindrical body 3 formed of a metal material, and the spent nuclear fuel W is contained in the cylindrical body 3 and sealed. The spent nuclear fuel W in the present embodiment means pellets stored in each fuel rod constituting an assembly of spent nuclear fuel taken out from the nuclear reactor after performing power generation for a predetermined period. Note that the cylindrical body 3 has a shape and a material that can easily extract heat from the spent nuclear fuel W. Here, the shape from which heat is easily extracted is a shape having a large surface area per unit volume, for example, the cylindrical body 3 is elongated. By making the shape easy to extract heat, the heat recovery means 10 can be made compact, and large heat can be supplied to the reaction section 21 described later constituting the hydrogen generation means 20A. Further, the container 2 may be a fuel rod containing spent nuclear fuel W taken out from the nuclear reactor.

As shown in FIG. 1, the heat supply means 15 is made of, for example, metal and has a cylindrical shape in which the reaction unit 21 is accommodated. The lower portions of the heat recovery means 10 and the heat supply means 15 are connected to each other by a first flow path 11a through which a fluid before heating flows. Moreover, the upper part of the heat recovery means 10 and the heat supply means 15 are connected by a second flow path 11b through which the heated fluid flows. A circulation pump 12 is provided in the middle of the first flow path 11a, and the heat medium S heated by the heat generated by the container 2 by the heat recovery means 10 supplies heat via the second flow path 11b. The heat medium S supplied to the means 15 and supplied with heat to the reaction section 21 by the heat supply means 15 returns to the heat recovery means 10 via the first flow path 11a. That is, the heat medium S circulates between the heat recovery means 10 and the heat supply means 15 via the first flow path 11a and the second flow path 11b. The heat recovery means 10, the flow path 11, and the heat supply means 15 are each kept warm by a heat insulating material so that heat can be used effectively. Further, the heat supply means 15 is not limited to a cylindrical shape, and is not particularly limited as long as it can supply heat to the reaction section.
In the present embodiment, the circulation pump 12 is provided on the first flow path 11a side, but may be provided on the second flow path 11b side.

  The heat generated from the spent nuclear fuel W is generated when a fission product (FP) contained in the spent nuclear fuel W is collapsed and converted into a light element.

  In the present embodiment, as shown in FIG. 2, the heat recovery means 10 is arranged in a space inside the storage portion 10 a with a plurality of containers 2 spaced apart from each other by a predetermined distance. In FIG. 2, the vertically long container 2 is placed in a direction along the flow of the heat medium S, but the container 2 may be placed in a direction perpendicular to the flow. In the present embodiment, since a plurality of containers 2 are arranged in the storage portion 10a, the contact area between each container 2 and the heat medium S can be set wide, so that the decay heat recovery rate of the spent nuclear fuel W can be increased. Can do.

  The heat medium S is not particularly limited as long as heat can be recovered. For example, the heat medium S can be selected from inert gases such as helium and argon, water, and carbon dioxide. In addition, like the coolant of the nuclear reactor, it is desirable that the heat medium S has characteristics such as being not activated, having a large specific heat, and being easy to handle.

  As shown in FIG. 1, the hydrogen generation means 20 </ b> A includes a reaction unit 21, a raw material supply unit 22, and a hydrogen recovery unit 23.

The reaction unit 21 is an apparatus that produces hydrogen using the raw material supplied from the raw material supply unit 22, and the reaction form in the reaction unit 21 may be any type in which a hydrogen generation reaction proceeds in the presence of heat. Although not limited to heat, it can be selected from one of a pyrolysis method, a reforming method, and a thermochemical method. The pyrolysis method can be selected from, for example, water pyrolysis, methane pyrolysis, methanol pyrolysis, and the like. The reforming method can be selected from, for example, a natural gas steam reforming method, a lime gasification method, a methanol steam reforming method, and a natural gas CO ₂ reforming method. The thermochemical method can be selected from, for example, an IS (Iodine-Sulfur) process. The pyrolysis method, the reforming method, and the thermochemical method are all known principles.

For example, as an example of the reforming method, a steam reforming method of natural gas will be described. In this method, methane (CH ₄ ) and water (H ₂ O) are respectively supplied from the raw material supply unit 22 to a predetermined temperature. In this method, hydrogen (H ₂ ) is generated by reacting with each other while applying heat. However, if this reaction mode is used, carbon dioxide will be generated. However, since the heat source necessary for the hydrogen reaction uses decay heat released from the spent nuclear fuel W, the combustion heat of fossil fuel is used. The amount of carbon dioxide emissions can be reduced compared to. Therefore, hydrogen can be produced in a state where the amount of carbon dioxide that causes the global warming phenomenon is kept low.

  As an example of the thermochemical method, the IS process will be described. In this method, water is supplied from the raw material supply unit 22 and a predetermined heat is applied by combining the Bunsen reaction, the hydrogen iodide decomposition reaction, and the sulfuric acid decomposition reaction. This is a method of generating hydrogen by reacting. When this reaction mode is used, hydrogen can be produced without discharging carbon dioxide.

  In the present embodiment, it is not always possible to select all the reaction forms described above, and it is necessary to select the reaction form in the reaction unit 21 according to the temperature that can be set by the heat recovery means 10. That is, when the temperature that can be set by the heat recovery means 10 is low, it is necessary to select a reaction form suitable for the temperature, and when the temperature that can be set by the heat recovery means 10 can be set high, Can select the necessary reaction form.

  In the reaction unit 21, only hydrogen is collected and collected in the hydrogen recovery unit 23. The hydrogen recovery unit 23 is, for example, a high-pressure cylinder or a large tank, and hydrogen can be stored in the cylinder or tank for a long time by recovering hydrogen. As described above, in this embodiment, hydrogen that can be stored can be produced using decay heat from the spent nuclear fuel W, so that decay heat is not exhausted to the outside and effective use of decay heat is possible. become. Moreover, since decay heat is continuously discharged for a long period of time, hydrogen can be stably supplied continuously. In addition, although it changes with reaction forms, in the case of the reaction form in which carbon dioxide is generated as a by-product at the time of hydrogen generation as described above, an apparatus (not shown) for treating carbon dioxide is provided to remove carbon dioxide. It is preferable to perform a treatment that does not release into the atmosphere.

Next, a flow until hydrogen is produced in the hydrogen production apparatus 1A of the present embodiment will be described.
When the circulation pump 12 is operated, the heat medium S starts to circulate between the heat recovery means 10 and the heat supply means 15, and the decay heat released from the spent nuclear fuel W through the cylinder 3 is recovered by the heat medium S. The The heat medium S heated to the high temperature by the decay heat is sent to the heat supply means 15 through the second flow path 11b. Although not shown in detail, the heat supply means 15 is configured to be able to supply heat necessary for the hydrogen generation reaction to the reaction unit 21. The reaction unit 21 receives heat from the heat supply means 15 and uses this heat as a heat source during the reaction to generate hydrogen. And since the heat medium S discharged | emitted from the heat supply means 15 has absorbed a part of heat | fever in the reaction part 21, it is lower than the temperature before it introduce | transduces into the heat supply means 15, and it passes from the 1st flow path 11a. It is discharged and returns to the heat recovery means 10. The heat medium S is heated again by the decay heat generated from the container 2 and sent to the reaction unit 21 via the second flow path 11b. In this way, the heat medium S circulates between the heat recovery means 10 and the heat supply means 15 so that heat can be continuously supplied to the reaction section 21.

  Further, the circulation pump 12 functioning as the adjusting means in the present embodiment can adjust the output, and can control the flow rate of the heat medium S circulating between the heat recovery means 10 and the heat supply means 15. Yes. Thereby, the temperature that can be supplied to the reaction unit 21 can be adjusted, and the temperature suitable for the reaction mode in the reaction unit 21 can be set.

  Even if the temperature can be adjusted by changing the flow rate of the heat medium S as described above, the heat is not wasted to the outside, so that the effective use of heat is not impaired.

(Second Embodiment)
FIG. 3 is an overall configuration diagram showing a hydrogen production apparatus according to the second embodiment.
The hydrogen production apparatus 1B of this embodiment is equipped with a hydrogen generation means 20B that converts the thermal energy of decay heat released from the spent nuclear fuel W into electrical energy and produces hydrogen by water electrolysis. . Since other configurations are the same as those of the first embodiment, the same reference numerals are given and description thereof is omitted. The same applies to each of the third and subsequent embodiments.

  The hydrogen generation means 20B includes a thermoelectric conversion unit 25 and an electrolysis unit 26. The thermoelectric conversion unit 25 includes a thermoelectric element, and the thermoelectric element directly converts heat energy into electric energy via the heat supply means 15. The thermoelectric element is not particularly limited as long as it can convert heat energy into electric energy, and can be selected from elements conventionally used in general.

  The electrolysis part 26 is comprised by the apparatus which can manufacture hydrogen by the electrolysis method of water. The electrolysis method of water can be selected from any one of alkaline water electrolysis, high temperature / high pressure alkaline water electrolysis, solid polymer electrolyte water electrolysis, and high temperature steam electrolysis. Any electrolysis method is a known principle.

  For example, a solid polymer electrolyte water electrolysis method will be described as an example of an electrolysis method. This method uses an ion exchange membrane as a diaphragm and an electrolyte, joins electrodes on both sides, and electrolyzes pure water to generate hydrogen. It is a method to do. According to this method, maintenance is easy and high-purity hydrogen can be obtained with high efficiency.

  In the hydrogen production apparatus 1 </ b> B of the second embodiment, the heat medium S that has recovered the decay heat of the spent nuclear fuel W is directly converted into electric energy by the thermoelectric conversion unit 25. The electrolysis unit 26 connected to the thermoelectric conversion unit 25 electrolyzes the water supplied from the raw material supply unit 22 by the electricity supplied from the thermoelectric conversion unit 25. By the electrolysis of water, hydrogen is generated from the cathode side of an electrode (not shown) provided in the electrolysis section 26 and oxygen is generated from the anode side.

  In the second embodiment, since hydrogen is generated using electric energy, if an alkaline water electrolysis method or a solid polymer electrolyte water electrolysis method is used as an electrolysis method in the electrolysis unit 26, a relatively high temperature heat source is generated. Since it becomes unnecessary, it becomes possible to use spent nuclear fuel taken out from a nuclear reactor in which it is difficult to set the heat medium S to a high temperature.

(Third embodiment)
FIG. 4 is an overall configuration diagram showing a hydrogen production apparatus according to the third embodiment.
This hydrogen production apparatus 1C is configured to include a turbine power generation unit 31 in the rear stage of the reaction unit 21 of the hydrogen production apparatus 1A, that is, the first flow path 11a. The turbine power generation unit 31 is provided in the middle of the first flow path 11a, and includes a turbine, a generator, a boiler (all not shown), and the like. The turbine is, for example, a steam turbine, which generates heat by using the heat of the heat medium S by a boiler to generate steam, and is rotationally driven by the steam. At this time, the generator is rotated by the rotational torque of the steam turbine to generate electricity.

  In the embodiment shown in FIG. 4, by installing the turbine power generation unit 31, power generation can be performed together with hydrogen production, and the use range can be expanded without impairing the decay heat of the spent nuclear fuel W. . Further, by providing the turbine power generation unit 31 at the subsequent stage of the reaction unit 21, the high-temperature heat medium S recovered from the heat recovery means 10 can be directly introduced into the reaction unit 21, so that the temperature of the hydrogen generation reaction is higher. It can be suitably used for the reaction section 21 in a reaction form that requires a large amount of heat.

(Fourth embodiment)
FIG. 5 is an overall configuration diagram showing a hydrogen production apparatus according to the fourth embodiment.
This hydrogen production apparatus 1D has a configuration in which the turbine power generation unit 32 is provided in the previous stage of the reaction unit 21, that is, in the second flow path 11b. The turbine power generation unit 32 has the same configuration as the turbine power generation unit 31 and includes a turbine, a generator, a boiler, and the like.

  In the embodiment shown in FIG. 5, by providing the turbine power generation unit 32 in the preceding stage of the reaction unit 21, the heat of the high-temperature heat medium S recovered by the heat recovery means 10 is taken away by the turbine power generation unit 32, so that the temperature is lower. The heat medium S is introduced into the reaction section 21. Therefore, it can utilize suitably for the reaction part 21 which has the reaction form which produces | generates hydrogen with the heat source of a low temperature.

  As shown in the third and fourth embodiments, in the present embodiment, by providing the turbine power generation units 31 and 32, the reaction unit 21 can be provided without adjusting the flow rate of the heat medium S as in the above-described embodiment. It becomes possible to control the temperature of the heat to be given. As a result, it is not necessary to provide a mechanism for controlling the temperature of the heat introduced into the reaction unit 21, so that the configuration of the hydrogen production apparatuses 1C and 1D can be simplified.

  In the present embodiment, as shown in the third and fourth embodiments, when the turbine power generation units 31 and 32 are provided to generate power, for example, in the reaction in the reaction unit 21, when electrolysis is combined, There are cases where the production efficiency of hydrogen can be increased, and there is a possibility that the temperature required in the reaction section 21 can be lowered. Moreover, if the temperature required in the reaction unit 21 can be lowered, it is not necessary to use a high-cost material as the material constituting the reaction unit 21, and it is possible to suppress deterioration of the apparatus constituting the reaction unit 21. it can.

  In addition, when the heat medium S cannot be heated to the temperature required for the reaction unit 21 only by the decay heat of the spent nuclear fuel W, the electric power of the turbine power generation unit 31 is also used to bring the heat medium S to the temperature required for the reaction unit 21. You may make it raise. That is, in the present embodiment, the configuration can be appropriately changed according to the required heat amount in the hydrogen production method to be used.

(Fifth embodiment)
FIG. 6 is an overall configuration diagram showing a hydrogen production apparatus according to the fifth embodiment.
This hydrogen production apparatus 1E is provided with an intermediate heat exchanger 40 between the heat recovery means 10 and the heat supply means 15 of the first embodiment. The intermediate heat exchanger 40 includes a heat exchanging unit 40a and a heat exchanging unit 40b, and a channel 41 (first channel 41a, second channel 41b, third channel 41c, and fourth channel 41d). And have. The heat recovery means 10 and the heat exchanging unit 40a are connected at a lower portion by a first flow path 41a through which the heat medium S before heating flows, and at the upper portions, a second flow through which the heat medium S after heating flows. They are connected by a path 41b. Further, the lower portions of the heat exchanging unit 40b and the heat supply means 15 are connected by a third flow path 41c through which a heat medium Sa different from the heat medium S before heat exchange flows, and the upper parts are heat exchanged. It is connected by a fourth flow path 41d through which the subsequent heat medium Sa flows. In addition, the circulation pump 13 is provided in the middle of the third flow path 41c, and the heat medium Sa heat-exchanged by the intermediate heat exchanger 40 passes through the fourth flow path 41d to supply heat. 15 and the heat medium Sa supplied with heat to the reaction part 21 by the heat supply means 15 returns to the heat exchange part 40b via the third flow path 41c.

  In the intermediate heat exchanger 40, the heat medium S and the heat medium Sa are not mixed with each other. Further, the circulation pump 13 may be provided with a mechanism capable of adjusting the output similar to the above-described circulation pump 12 and can change the flow rate (flow velocity) of the heat medium Sa.

  In the fifth embodiment, the heat medium S that has been heated by the decay heat generated from the spent nuclear fuel W and has reached a high temperature state is sent to the heat exchange unit 40a of the intermediate heat exchanger 40 through the second flow path 41b. . In the intermediate heat exchanger 40, the heat of the heat medium S is transmitted to the heat medium Sa flowing in the heat exchange unit 40b, and the heat medium Sa becomes a high temperature state. The high-temperature heat medium Sa is sent to the heat supply means 15 through the fourth flow path 41 d by the power of the circulation pump 13. In the reaction unit 21, hydrogen is generated using the heat of the heat medium Sa as a heat source. And the heat medium Sa discharged | emitted from the heat supply means 15 returns to the heat exchange part 40b through the 3rd flow path 41c, and receives heat again from the heat exchange part 40a.

  By providing the intermediate heat exchanger 40 as in the fifth embodiment, the heat medium S contaminated with the radioactive material is not directly supplied to the reaction unit 21 side, so that a safer system can be obtained. it can.

  The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the heat source is not limited to the spent nuclear fuel taken out from the nuclear reactor, but may be nuclear waste called so-called high-level radioactive waste that remains after the spent nuclear fuel is reprocessed. Or the nuclear waste after use which discharge | releases the decay heat other than that may be sufficient.

  In the third and fourth embodiments, the turbine power generation units 31 and 32 are installed in the subsequent stage and the previous stage of the reaction unit 21, but the turbine power generation is performed in the subsequent stage and the previous stage of the thermoelectric conversion unit 25 of the second embodiment. The structure which mounts a part may be sufficient. Moreover, the structure which provides an intermediate | middle heat exchanger between the heat recovery means 10 and the thermoelectric conversion part 25 may be sufficient.

It is a whole lineblock diagram showing the hydrogen production device of a 1st embodiment. It is sectional drawing which shows the internal structure of a heat recovery means. It is a whole block diagram which shows the hydrogen production apparatus of 2nd Embodiment. It is a whole block diagram which shows the hydrogen production apparatus of 3rd Embodiment. It is a whole block diagram which shows the hydrogen production apparatus of 4th Embodiment. It is a whole block diagram which shows the hydrogen production apparatus of 5th Embodiment.

Explanation of symbols

1A to 1E Hydrogen production apparatus 2 Container 10 Heat recovery means 15 Heat supply means 11a First flow path 11b Second flow path 12, 13 Circulation pump (adjustment means)
20A to 20B Hydrogen generating means 21 Reaction unit 22 Raw material supply unit 23 Hydrogen recovery unit 25 Thermoelectric conversion unit 26 Electrolysis unit 31, 32 Turbine power generation unit 40 Intermediate heat exchanger S, Sa Heat medium W Used nuclear fuel

Claims (7)

  Heat recovery means for recovering heat released from spent nuclear fuel or nuclear waste that generates decay heat via a predetermined heat medium, and hydrogen generation using the heat recovered by the heat recovery means to generate hydrogen Means, a heat supply means for supplying heat recovered by the heat recovery means to the hydrogen generation means, and a flow path for circulating the heat medium between the heat recovery means and the heat supply means. A hydrogen production apparatus characterized by   The hydrogen production apparatus according to claim 1, wherein the hydrogen generation unit includes a reaction unit that generates hydrogen by any one of a thermal decomposition method, a reforming method, and a thermochemical method.   The hydrogen generation unit includes a thermoelectric conversion unit that converts the heat into electricity, and an electrolysis unit that generates hydrogen by an electrolysis method of water using electricity generated by the thermoelectric conversion unit. The hydrogen production apparatus according to claim 1.   The hydrogen production apparatus according to any one of claims 1 to 3, wherein an adjustment means capable of adjusting a flow rate of the heat medium is provided in the flow path.   The turbine flow path that extends from the heat supply unit to the heat recovery unit is provided with a turbine power generation unit that generates power using heat discharged from the heat supply unit. The hydrogen production apparatus according to any one of claims 1 to 4.   2. The turbine power generation unit that generates power using heat before being supplied to the heat supply unit is provided in the flow path from the heat recovery unit to the heat supply unit. The hydrogen production apparatus according to any one of claims 1 to 4.   The hydrogen production apparatus according to any one of claims 1 to 6, wherein an intermediate heat exchanger is provided between the heat recovery means and the heat supply means.

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