JP2010019592A - Sodium purifier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cold trap which eliminates the necessity of the complicated reclamation treatment of an impurity trapping section and reduces the frequency of the reclamation treatment. <P>SOLUTION: A sodium purifier is constituted by placing mesh fillers for trapping impurities in a flow channel of liquid metal sodium, two or more layers of mesh fillers 13 and 14 are placed in the flow direction of the liquid metal sodium. When the mesh lattice length and the strand diameter of each layer of the mesh fillers are set at (a) and (b) respectively and the difference between the former and the latter is taken as (a-b), mesh fillers with a lower value of (a-b) are placed downstream in the flow direction of the liquid metal sodium than those placed upstream in the flow direction of the liquid metal sodium. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a sodium purification device called a cold trap provided in a fast breeder reactor, and more particularly to means for extending the life of an impurity trapping part that traps impurities contained in liquid metal sodium.

  Conventionally, a fast breeder reactor using liquid metal sodium as a coolant has been provided with a sodium purification device called a cold trap. This device deposits impurities dissolved in liquid metal sodium using the difference in saturation solubility depending on the temperature, and consists of mesh (wire mesh) filled in the low-temperature part or mesh filling such as expanded metal. It is the refinement | purification apparatus captured with a capture part (for example, refer nonpatent literature 1).

  FIG. 8 is a diagram showing an example of a cold trap of this type that is conventionally known. As is clear from this figure, the cold trap of this example has an upper tube plate 21 and a lower tube plate 22 in the body 10 formed in the shape of a cylindrical container, and is held through the tube plates 21 and 22. A plurality of cooling pipes 18 arranged along the inner wall of the fuselage 10, a heat insulating gas layer 15 arranged concentrically with the cooling pipe 18 on the inner peripheral side of the arrangement position of the cooling pipes 18, and the heat insulating gas layer 15, penetrates through the upper part of the body 10 and the upper tube plate 21, and communicates with the cooling part 11 provided in the body 10. A sodium inlet pipe 19, a sodium outlet pipe 20 that passes through the upper portion of the fuselage 10 and the upper tube plate 21 and communicates with the impurity trap 12, a cooling gas inlet pipe 16 provided at the lower portion of the fuselage 10, and the fuselage 10 At the top It is mainly composed of the cooling gas outlet pipe 17.

  Liquid metal sodium as the material to be purified flows into the body 10 from the sodium inlet pipe 19 and flows down through the cooling unit 11. On the other hand, the cooling gas enters the body 10 from the cooling gas inlet pipe 16 and rises through the cooling pipes 18 arranged in parallel around the periphery. Heat exchange is performed with the liquid metal sodium flowing down in this process, and the heated cooling gas further rises and flows out from the cooling gas outlet pipe 17. The liquid metallic sodium cooled in the cooling unit 11 is reversed in its flow direction by the lower tube plate 22 and passes through the impurity trapping unit 12, where impurities are deposited and removed. The purified sodium flows out through the sodium outlet pipe 20 (see, for example, Patent Document 1).

When the cold trap having such a configuration is continuously operated, the impurity trapping portion 12 is clogged with impurities, so that the pressure difference between the inlet side and the outlet side of the liquid metal sodium rises, and the liquid metal sodium becomes smooth. The flow is obstructed. For this reason, when the differential pressure becomes a predetermined value or more, for example, a regeneration process of the impurity trapping part using a regeneration method disclosed in Patent Document 2 is required.
JP 62-191002 A Japanese Patent Application No. 56-133610 Supervised by Masao Hotta, edited by the Basic Fast Reactor Engineering Editorial Committee "Basic Fast Reactor Engineering" (Nikkan Kogyo Shimbun, October 29, 1993, p68-69)

  However, the regeneration process of the impurity trapping part has a problem that the operation is complicated and requires a lot of labor, and secondary waste is generated. Therefore, it is desired to develop a technique that can eliminate the need for the regeneration process of the impurity trapping portion or reduce the frequency thereof.

  In order to eliminate the need to regenerate the impurity trapping part or reduce its frequency, the long life of the impurity trapping part made of mesh filling without sacrificing the problem of differential pressure, impurity trapping amount and removal rate It is necessary to plan.

  The present invention has been made based on such a demand, and an object of the present invention is to provide a cold trap that can eliminate the need for complicated regeneration processing of the impurity trapping portion and can reduce the frequency of the regeneration processing.

  In order to achieve the above object, the present invention provides a sodium purification apparatus in which a mesh filling for trapping impurities is arranged in a flow path of liquid metal sodium, and the mesh of at least two layers in the flow direction of the liquid metal sodium. The packing is arranged, and when the mesh lattice length of the mesh packing of each layer is a, the wire diameter is b, and the difference between these values is (ab), the downstream side in the flow direction of the liquid metal sodium In the configuration, a mesh filler having a value (ab) smaller than that of the mesh filler arranged on the upstream side in the flow direction of the liquid metal sodium is arranged.

  An effective space amount of a mesh filler such as a mesh or expanded metal can be expressed by a mesh lattice length a and a wire diameter b. According to the experiments by the present inventors, the larger the difference (ab) between the mesh lattice length a and the wire diameter b, the greater the amount of impurities trapped, but the smaller the impurity removal rate, and vice versa. As the difference (ab) is smaller, the impurity removal rate is increased, but the impurity trapping amount is smaller. Therefore, when a mesh packing having a large value (ab) is arranged on the upstream side in the flow direction of the liquid metal sodium and a mesh packing having a small value (ab) is arranged on the downstream side, trapping of impurities is performed. The amount and removal rate can be high, and an impurity trapping portion that is not easily clogged can be obtained. Therefore, it is possible to extend the life of the impurity trapping part, eliminate the need for the regeneration process of the impurity trapping part, reduce the frequency thereof, omit or reduce the labor required for the regeneration process of the impurity trapping part, and the impurity trapping part It is possible to eliminate or reduce the secondary waste generated with the recycling process.

  Further, in the sodium purification apparatus having the above configuration, the mesh packing (ab) disposed on the upstream side in the flow direction of the liquid metal sodium is 4 mm or more, and is disposed on the downstream side in the flow direction of the liquid metal sodium. (Ab) of the mesh filler to be formed is 1 mm or more and less than 4 mm.

  According to the experiment, when the difference (ab) between the mesh lattice length a and the wire diameter b is 4 mm or more, 100 kg or more of oxygen can be captured, and the difference (ab) is 1 mm or more and less than 4 mm. By doing so, about 90% or more of oxygen can be removed. Therefore, the amount of trapped impurities is set such that (ab) of the mesh packing arranged on the upstream side is 4 mm or more and (ab) of the mesh packing arranged on the downstream side is 1 mm or more and less than 4 mm. In addition, it is possible to provide an impurity trapping portion that has a high removal rate and is not easily clogged.

  In the sodium purification apparatus of the present invention, at least two layers of mesh packing are arranged in the flow direction of liquid metal sodium, the mesh lattice length of the mesh packing of each layer is a, the wire diameter is b, and the difference between these values. When (ab) is set to (a-b), mesh packing with a smaller value of (ab) than the mesh packing disposed on the upstream side in the liquid metal sodium flow direction on the downstream side in the liquid metal sodium flow direction Since an object is disposed, an impurity trapping portion that has a high amount of trapped impurities and a high removal rate and is less likely to be clogged can be obtained.

  First, the structure of the sodium purification apparatus (cold trap) which concerns on embodiment is demonstrated using FIG. FIG. 1 is a cross-sectional view of a sodium purification device according to an embodiment.

  The basic structure of the cold trap according to the embodiment is the same as that of the cold trap according to the conventional example shown in FIG. 8, and as shown in FIG. The upper tube plate 21 and the lower tube plate 22, a plurality of cooling tubes 18 that are penetrated and held by the tube plates 21 and 22 and arranged along the inner wall of the fuselage 10, and the arrangement positions of the cooling tubes 18 A heat insulating gas layer 15 arranged concentrically with the inner peripheral side, a sodium inlet pipe 19 penetrating through the upper part of the fuselage 10 and the upper tube plate 21 and communicating with the cooling unit 11 provided in the fuselage 10; The sodium outlet pipe 20 penetrating the upper part of the fuselage 10 and the upper tube plate 21 and communicating with the impurity trapping part 12, the cooling gas inlet pipe 16 provided at the lower part of the fuselage 10, and the upper part of the fuselage 10. Cooling gas out And a pipe 17.

  The difference between the cold trap according to the embodiment and the cold trap according to the conventional example is that the cold trap according to the conventional example includes one impurity trap 12 on the inner peripheral side of the heat insulating gas layer 15. The cold trap according to the embodiment is provided with two layers of the first impurity trap 13 and the second impurity trap 14 on the inner peripheral side of the heat insulating gas layer 15. The first impurity trap 13 is an impurity trap disposed upstream with respect to the flow direction of liquid metal sodium, and the second impurity trap 14 is an impurity trap disposed downstream with respect to the flow direction of liquid metal sodium. Part.

  The 1st and 2nd impurity capture parts 13 and 14 are formed with mesh fillings, such as a mesh (metal mesh) and an expanded metal. The expanded metal is obtained by extending a metal plate having a large number of cuts in the plane direction in the plate thickness direction, and in the same manner as the mesh, a void having regularity is formed in the cut portions.

  When the mesh lattice length of the mesh filler constituting the first and second impurity traps 13 and 14 is a, the wire diameter is b, and the difference between these values is (ab), the second As the mesh filler constituting the impurity trapping part 14, a mesh filler having a value (ab) smaller than that of the mesh filler constituting the first impurity trapper 13 is used.

  The sodium outlet pipe 20 is connected to the upper part so as to communicate with the second impurity trapping part 14.

  In the cold trap of this example, liquid metal sodium to be purified flows into the body 10 from the sodium inlet pipe 19 and flows down through the cooling unit 11 in the vicinity. On the other hand, the cooling gas enters the body 10 through the cooling gas inlet pipe 16 and rises through a large number of cooling pipes 18 arranged in the vicinity. Heat exchange is performed with the liquid metal sodium flowing down in this process, and the heated cooling gas further rises and flows out from the cooling gas outlet pipe 17. The liquid metal sodium cooled in the cooling section 11 is reversed in its flow direction in the lower tube plate 22 and passes through the first impurity trapping section 13 where impurities are deposited and removed, and further passes through the second impurity trapping section 14. The impurities are also deposited and removed there. Purified sodium flows out through the sodium outlet pipe 20.

  Hereinafter, specifications of the first impurity trap 13 and the second impurity trap 14 according to the present embodiment will be described with reference to FIGS. These specifications were found by the following examination using calculation codes whose validity was confirmed by actual plant data.

  As shown in FIG. 2, the mesh filler constituting the impurity traps 13 and 14 can be modeled as a cube surrounded by wires. Basically, it is solved by using the formula of the total length of the wire calculated from this model and the wire volume ratio calculated from the mesh packing density, the wire density, and the wire diameter.

  Specifically, assuming that the total length per unit volume of the wire is A, from the model shown in FIG.

A ≒ wire length per grid x number of grids per unit volume ≒ 3 · L / L ³
On the other hand, the volume ratio V of the wire obtained by dividing the mesh packing density by the wire density is expressed by the following equation.

V = π / 4 · D ² · A = 3/4 · π · (D / L) ²
Further, in consideration of the overlapping of the wires at the intersection of the lattice, the volume ratio V of the wire is expressed by the following equation.

V≈3 / 4 · π · (D / L) ² −1.8 / 4 · π · (D / L) ³
From the above equation, the lattice length L can be obtained.

  In addition, as shown in FIG. 2, oxygen O and hydrogen H, which are impurities in the liquid metal sodium, diffuse through the outer boundary film and deposit with a wire (elementary wire) or precipitate as a nucleus. The amount of precipitate on the wire increases with time, and the wire diameter of the wire apparently increases. When the wire diameter approaches the lattice length L, the differential pressure increases and liquid metal sodium cannot pass therethrough.

  Next, the amount of impurities trapped until the differential pressure increased and the removal rate were calculated using a calculation model. Here, the calculation was performed by changing the packing density of the meshes having two wire diameters. 3 and 5 are data in which the calculation results are arranged by packing density, and FIGS. 4 and 6 are data in which “lattice length a−element diameter b” representing an effective space amount are arranged. As shown in FIG. 4 and FIG. 6, when arranged by “lattice length a−element diameter b”, a good linear relationship is obtained for both the impurity trapping amount and removal rate, and in a system for removing impurities from liquid metal sodium. , "Lattice length a-strand diameter b", it was found that can be organized.

  As apparent from FIG. 4, the amount of trapped impurities increases as “lattice length a−element diameter b” increases. In contrast, as is clear from FIG. 6, the impurity removal rate decreases as “lattice length a−element diameter b” increases. Therefore, in the conventional cold trap, a region where “lattice length a−element wire diameter b” is 1 mm or more and less than 4 mm is used in order to exclude a region where the amount of trapped impurities is almost zero.

  As described above, in the cold trap according to the present embodiment, the impurity trapping portion is divided into two regions, and the first layer filled with the mesh filler whose “lattice length a−element diameter b” exceeds 4 mm, and 1 mm or more And a second layer filled with a mesh filler of less than 4 mm.

  FIG. 7 shows the relationship between the differential pressure and the amount of trapped impurities in the cold trap according to the present embodiment and the cold trap according to the conventional example.

As a conventional example, a mesh having a strand diameter of 0.294 mm was filled into a hollow cylindrical impurity trapping portion having an outer diameter of 1000 mm and an inner diameter of 17.3 mm so as to have a packing density of 100 kg / m ³ . At this time, “lattice length a−element diameter b” is 3.8 mm. On the other hand, in the cold trap according to the embodiment, first, as the first impurity trapping part 13, a mesh having a wire diameter of 1.0 mm has a diameter of 1000 mm in the above-described impurity trapping part so as to have a packing density of 400 kg / m ^3. To 800 mm in a cylindrical shape. Thereafter, as the second impurity trapping portion 14, a mesh having the same wire diameter of 0.294 mm as in the conventional example was filled so as to have a filling density of 100 kg / m ³ . At this time, “lattice length a−element diameter b” of the first impurity trapping portion 13 is 5.46 mm, which satisfies the condition exceeding 4 mm of the present invention. As can be seen from FIG. 7, the amount of oxygen trapped by the cold and wrap according to the embodiment is about 194 kg, which is more than twice the amount of about 92 kg which is the amount of oxygen trapped by the cold and wrap according to the conventional example.

  Therefore, the cold trap according to the present embodiment can capture impurities over a long period of time that is twice or more that of the cold and wrap according to the conventional example.

  In the present embodiment, liquid metal sodium is allowed to flow from the side surface direction of the columnar impurity traps 13 and 14, but this has a larger inflow area than the method of flowing from the upper and lower surfaces of the column. Since it can be increased, the differential pressure rise can be moderated, which is suitable for the purpose of the present invention.

  In this embodiment, a mesh having a strand diameter of 0.294 mm and a strand diameter of 1.0 mm is used, but other strand diameters may be used. The thicker the wire diameter, the less the mesh filling portion is compressed by the pressure when the differential pressure is increased, and it is possible to prevent the differential pressure increase from being accelerated by the consolidation.

  Furthermore, in the said embodiment, although the two layers of impurity trap parts 13 and 14 were provided, it can also be provided with the impurity trap part of three or more layers.

  The cold trap according to the present embodiment can be applied not only to FBR but also to a metal sodium production line.

It is a structure figure of the cold trap which concerns on embodiment. It is the figure which showed the impurity capture mechanism. It is the figure which showed the relationship between the capture amount and the mesh packing density. It is the figure which showed the relationship between the capture amount and "the mesh lattice length of a filler-element wire diameter". It is the figure which showed the relationship between a removal rate and a mesh packing density. It is the figure which showed the relationship between a removal rate and "the mesh lattice length of a filler-strand diameter". It is the figure which showed the relationship of the differential pressure | voltage rise and capture amount by one Example of this invention. It is a structural diagram of a cold trap of a conventional example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Body 11 Cooling part 13 1st impurity capture part 14 2nd impurity capture part 15 Adiabatic gas layer 16 Cooling gas inlet pipe 17 Cooling gas outlet pipe 18 Cooling pipe 19 Sodium inlet pipe 20 Sodium outlet pipe,

Claims (2)

  In a sodium purification apparatus in which a mesh filler for trapping impurities is arranged in a flow path of liquid metal sodium, at least two layers of mesh filler are arranged in the flow direction of the liquid metal sodium, and the mesh filler of each of these layers When the mesh lattice length is a, the wire diameter is b, and the difference between these values is (ab), the downstream of the flow direction of the liquid metal sodium is upstream of the flow direction of the liquid metal sodium. A sodium purifier, wherein a mesh filler having a value (ab) smaller than that of the mesh filler arranged on the side is arranged.   (Ab) of the mesh packing disposed on the upstream side in the flow direction of the liquid metal sodium is 4 mm or more, and (ab) of the mesh packing disposed on the downstream side in the flow direction of the liquid metal sodium. ) Is 1 mm or more and less than 4 mm.

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