JPS6132550B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coating method for fast breeder reactor sodium piping using metallic sodium as a coolant.

Conventionally, asbestos insulation materials, rock wool insulation materials, barlite insulation materials, calcium silicate insulation materials, ceramic wool, etc. have been used as insulation materials for this sodium piping, but of course these insulation materials are usually used in plants. This material was developed as a heat insulating material for related thermal equipment, and has excellent properties as a heat insulating material. That is, it is a material that is heat resistant and has low thermal conductivity.

However, when these insulation materials come into contact with high-temperature metallic sodium in the atmosphere, they react violently and burn while emitting white smoke, destroying the insulation materials. Therefore, if these insulation materials are used for sodium piping, in the event that sodium leaks, it will immediately react with the sodium and cause a fire, destroying the insulation material and flowing out, producing a large amount of white smoke. The fuel will continue to burn, creating a dangerous situation. Therefore, we have adopted methods such as creating a double pipe structure for the sodium piping and creating an inert gas atmosphere between them, and placing a "tohi" or "receptacle" at the bottom of the piping covered with heat insulating material, in the event that sodium leaks and flows out. In some cases, methods have been considered for directing the fire to a "tamer mass" and centrally extinguishing it there, but the former is not necessarily advantageous in terms of construction and economy, and the latter is It is far from perfect as it involves problems such as allowing reactions with the heat insulating material and causing sodium or other compounds to accumulate on the "tohi" or saucer outside the heat insulating material, which may obstruct the flow to the tame mass. It's tough.

Therefore, the purpose of the present invention is to use a coating material that does not react with sodium even if sodium leaks from sodium piping, does not undergo an oxidation reaction, and does not react with burning sodium. By doing so, it is possible to prevent fires or to safely guide the sodium to ``Tamemas''. The present invention provides a coating method for sodium piping.

As is well known, metallic sodium is chemically active and burns by reacting with most substances, including oxygen and water, in the atmosphere. For example, the above-mentioned heat insulating material has SiO ₂ , CaO, Al ₂ O ₃ and the like as its main components, and burns by violently reacting with high temperature (approximately 600° C.) metallic sodium in the atmosphere.

Therefore, it is essential that the coating material used in the present invention has the property of not reacting with high-temperature metallic sodium in the atmosphere. Examples of such coating materials include the following coatings for sodium piping. There is material.

In other words, it is a coating material made by mixing a sodium-resistant alkali metal salt and silicic acid or sodium phosphate in a wet state, molding the mixture under pressure, and then drying it, and if necessary, adding metal soap to this mixture. It is a covering material that is pressure-molded with the addition of a reinforcing material, or that is pressure-molded with a reinforcing material and dried.

Approximately 800 sodium-resistant alkali metal salts
It can withstand metallic sodium up to ℃, and typical formulation examples are as follows.

Anhydrous sodium carbonate 250-300 parts Stearic acid metal salt 1-10 parts Stainless fiber thread or wire 1-10 parts Sodium silicate 150-250 parts Anhydrous sodium carbonate, the main ingredient, absorbs water and becomes sodium carbonate hydrate. , its hydrates include Na ₂ CO ₃ .H ₂ O Na ₂ CO ₃ .7H ₂ O Na ₂ CO ₃ .10H ₂ O.

Since these waters of crystallization easily decompose at temperatures below 100°C and become anhydrous sodium carbonate, a hydrate of sodium carbonate may be used instead of anhydrous sodium carbonate.

Sodium silicate used as a binder comes in powder form and liquid form. When using anhydrous sodium carbonate, it is sufficient to dilute liquid sodium silicate with water, but when using hydrated sodium carbonate as described above, mix powder and sodium silicate in advance. At the time of molding, it is preferable to further use a sodium silicate aqueous solution and perform pressure molding.

Stainless fiber thread is a bundle of stainless fibers (approximately 12μ) that facilitates pressure molding and demolding of the molded product, increases the strength of the molded product, prevents warping, and improves dimensional stability. It is valid. This stainless fiber thread is available in SUS304, SUS310S, SUS316L, etc. depending on its composition.
Among them, SUS310S is heat resistant and can withstand temperatures of approximately 600°C.
0.4m/mφ) can also be used.

Stearic acid metal salt, which is a metal soap, acts as a mold release agent during demolding, and also works at temperatures of about 100 to 200℃.
It melts and forms a film, which has the effect of preventing the penetration of metallic sodium.

This is a coating material obtained by mixing the above compounded materials, press-molding the mixture as a whole in a wet state, and drying it.

Specific formulation examples are as follows.

Combination example 1 Light anhydrous sodium carbonate 300 parts Zinc stearate 6 parts Stainless steel fiber thread (SUS310, length 3-50m/m) 5 parts Sodium silicate No. 3 (15% concentration) 200 parts Light anhydrous sodium carbonate and zinc stearate Mix well in advance, add 15% concentration sodium silicate and stainless fiber thread, and mix. In this case, the anhydrous sodium carbonate absorbs the water in the sodium silicate and becomes a hydrate when mixed for a long time, making moldability difficult. Pressure mold in ^cm2 . This is a coating material obtained by removing the mold after molding, slow heating the molded product, heating it at about 105°C, and drying it until it becomes an anhydride.

Formulation example 2 Light anhydrous sodium carbonate 250 parts Sodium carbonate hydrate (Na ₂ CO ₃・10H ₂ O) 150 parts Zinc stearate 6 parts Stainless steel wire (diameter 0.4 m/m, length 10 to 50 m/m) 5 parts Powder, Sodium Silicate No. 3 10 parts Sodium Silicate No. 3 (15% concentration) 200 parts The manufacturing method is almost the same as in Formulation Example 1. First, the powder components are mixed well in advance, and then 15% concentration of sodium silicate and This is a coating material obtained by adding a stainless steel wire and mixing the mixture, press-molding the mixture in the same manner, and then drying it.

It has been confirmed that the sodium piping coating material obtained in this way has sodium resistance by pouring metallic sodium onto the surface of the coating material at approximately 600°C in an atmospheric atmosphere, and the coating material thickness It has been confirmed that there is no penetration in the horizontal direction. That is,
The above-mentioned coating material does not react with high-temperature metallic sodium in the atmosphere, undergoes an oxidation reaction, and does not react with burning sodium, and its general physical properties are as follows: It is as follows.

〇Appearance White solid 〇Density 800Kg/m ³ ~1000Kg/m ³ 〇Bending strength 20Kg/cm ² ~30Kg/cm ² 〇Thermal conductivity 0.1Kcal/mn℃ 〜0.2Kcal/mh℃ 〇Workability “Saw” work Possible The present invention is a coating method for sodium piping characterized by using a coating material that does not react with high-temperature metallic sodium in the atmospheric atmosphere as described above,
By attaching such a sodium-resistant coating material to the sodium piping, even if high-temperature metallic sodium leaks, it will not react with the coating material, so general insulation materials such as those mentioned above can be used. Unlike in the case where the sodium is exposed to the outside of the sheathing material, without leaking to the atmosphere or causing a fire, the leaked sodium is released into the gap between the outer circumferential surface of the sodium pipe and the inner circumferential surface of the sheathing material. If it exists, it will burn there.

This combustion continues until oxygen is consumed or as long as metallic sodium continues to leak, and the metallic sodium that has finished burning becomes sodium oxide and is deposited. In this way, leaked sodium does not react with or penetrate the coating material, so
The metallic sodium itself burns on the inner peripheral surface of the coating material due to the presence of oxygen, so there is no external change and there is no need to cause a fire. Therefore, if the amount of leaked sodium is small, it is sufficient to simply install this kind of sodium-resistant coating on the sodium piping, but if metallic sodium leaks under high pressure or the amount of leakage If there is a large amount of metal sodium, it will flow along the slope of the piping because it will not react with the coating material. Therefore, in such cases, a number of grooves should be provided on the inner surface of the coating material, that is, the surface that comes into contact with the sodium piping, so that even if sodium leaks from any part of the sodium piping, it can easily flow to the bottom. The covering material located at the bottom of the pipe is preferably used with a groove for a flow path for leaked sodium in the length direction of the bottom of the pipe. A sodium-resistant adhesive joint compound is used to bond the joints between the covering materials. (An example of this adhesive joint agent is a heat-resistant inorganic sodium-resistant adhesive whose main ingredients are sodium carbonate and sodium silicate.) In cases where a large amount of metallic sodium leaks or leaks under high pressure, By providing the above-mentioned grooves on the inner surface of the sheathing material, in the event that sodium leaks, it will come into contact with the sheathing material first, but the sodium will not react or penetrate, so the grooves at the bottom of the pipe will If oxygen is present, the leaked sodium will be burned and flowed along the slope of the pipe, and the burned sodium will become sodium oxide and deposit.

Therefore, by creating an inert gas atmosphere around the groove, the combustion of the leaked sodium is minimized, and by maintaining fluidity, it can be guided safely along the slope of the pipe to "Tamemasu" etc. can do. However, always around the groove,
Since it is uneconomical to create an inert gas atmosphere, it should be combined with auxiliary measures such as installing a device that can supply inert gas only in the event of a leak in combination with a sodium leak detector. is desirable.

Furthermore, as mentioned above, the temperature of sodium is about 600℃.
℃, the thermal expansion of the piping is large, and there is a risk of creating gaps at the seams of the sheathing material.In that case, it is thought that leaked sodium will permeate through those gaps, and the sheathing material It is safer to construct two or more layers with staggered seams and adhere them with a sodium-resistant adhesive joint compound.

In addition, if the sodium-resistant coating material has a high density and thermal conductivity as mentioned above, the operating temperature of sodium piping is approximately 600℃, and from the standpoint of insulation, the coating material is thicker than necessary. In that case, it is used in combination with a heat insulating material as a composite material. In this case as well, it goes without saying that a sodium-resistant coating material is first used on the outer surface of the sodium pipe, and by using the above-mentioned inorganic heat insulating material as the outer layer, the overall coating thickness can be reduced. can be made thinner and lighter. In either case, the outermost layer is covered with an exterior material commonly used for heat insulation work.

Next, embodiments of the present invention will be described with reference to the drawings. In FIGS. 1 and 2, 1 is a sodium pipe of a fast breeder reactor, for example, and 2 is a covering material molded into a vertically divided semi-cylindrical shape using the above-mentioned formulation example. To cover the sodium pipe 1 with this material, The vertically split semi-cylindrical sheathing materials 2 are attached to the sodium pipe 1 while facing each other, and the joints 2a of the sheathing materials 2 are glued with a sodium-resistant adhesive joint material 3, and the outer periphery is covered with stainless steel wire. Bondage at 4. The coating materials 2 are successively installed in the length direction of the sodium pipe 1 and the joints 2b at both ends of each coating material 2 are adhered with the adhesive joint material 3, and then the outer periphery of the coating material 2 is wrapped in a tape or sheet shape. The exterior is sequentially covered with exterior material 5.

FIGS. 3 and 4 show grooves 6 for guiding leaked metal sodium provided on the inner surface of the covering material 2 that is in contact with the bottom of the sodium pipe 1. The grooves 6 for guiding leaked metal sodium are continuous along the bottom of the sodium pipe 1. In this case, attach the covering material 2 to each of the sodium pipes 1 so as to
If metallic sodium leaks from the guide groove 6
It can be safely guided to the "Tamemasu" (not shown) below. Figures 5 and 6 show two layers of vertically split semi-cylindrical sheathing material 2, which are attached with the seam 2b of the outer semi-cylindrical sheathing material 2 and the inner seam staggered, respectively. It is desirable that both ends of the outer sheathing material 2 and both ends of the outer sheathing material 2 be offset from each other. By shifting each joint in this manner, leakage of metallic sodium from the joints of the inner covering material 2 can be further prevented.

In FIGS. 7 and 8, the coating material 2 is made of two layers, and a guide groove 6 is further provided on the inner surface of the coating material 2 that contacts the bottom of the sodium pipe 1.

In the embodiments shown in FIGS. 1 to 8, the sheathing material 5 is an example in which the same sheathing material as in the ordinary insulation method is used, but as shown in FIGS. 9 to 16, the sheathing material 5 is made of Using a heat insulating material 5a and a sheet-like or tape-like exterior material 5b, the heat-insulating material 5a is attached to the outer periphery of each covering material 2, and the outer periphery is further covered with a sheet-like or tape-like exterior material 5b. Increases heat retention effect.

In FIG. 17, a plurality of protrusions 7 are formed on the inner surface of the covering material 2 having a vertically divided semi-cylindrical shape.
A circumferential groove 8a and a longitudinal groove 8b on the inner surface of the
is formed so that the leaked metallic sodium collects in the metallic sodium guiding groove 6 at the bottom. FIG. 18 shows a covering material 2 to be attached to a vertical portion of a sodium pipe, and an inclined groove 8c is formed on its inner surface so that leaked metallic sodium flows along the inclined groove 8c and collects in the guiding groove 6. Furthermore, Figures 17 and 18
The sheathing shown in the figure is installed in the same manner as the embodiment shown in FIGS. 1-16. Figure 19 is the first
Grooves 8a and 8b on the inner surface of the coating material 2 shown in FIG. 7 are used, and sheathed heaters 9 for keeping metal sodium warm are provided in the grooves 8a and 8b. FIG. 20 shows a metal sodium leak detector 1 installed in the metal sodium guide groove 6 on the inner surface of the sheathing material 2 after the sodium piping 1 is coated with the sheathing material 2 in the above-described embodiment.
0, and an inert gas supply pipe 11 is connected to the guide groove 6 to detect leakage of metallic sodium to the detector 10, and send the signal to the controller 1.
2, close the upstream valve 13 of the sodium pipe 1 to prevent metal sodium from leaking for a long time, and at the same time open the inert gas supply valve 14 to supply inert gas into the guiding groove 6. supply
The leaked metallic sodium is safely guided down the guide groove 6 to the dam 15 below.

In addition, in the above-mentioned embodiment, an example was shown in which the sheathing material is formed into a vertically divided semi-cylindrical shape, but the present invention is not limited to this shape, and the shape of the sheathing material is shaped into a cylindrical shape according to the diameter of the sodium pipe. Of course, it can be covered by dividing it into four parts, etc.

As described above, since the present invention uses a sodium-resistant coating material for sodium piping,
In the unlikely event that high-temperature metallic sodium leaks from sodium piping, a fire will occur because the sodium will not react with or penetrate the coating material, unlike when conventional general insulation materials are used. This is an indispensable coating method for sodium piping, which prevents leakage and prevents leakage of sodium into the atmosphere.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an embodiment of the present invention, Fig. 2 is a sectional view taken along the line - - in Fig. 1, and Fig. 3 is a diagram showing an embodiment in which guide grooves are provided on the inner surface of the covering material in Fig. 1. , Fig. 4 is a sectional view taken along the line - - in Fig. 3, Fig. 5 is a diagram showing an example in which the covering material in Fig. 1 is made into a multilayer, and Fig. 6 is a cross-sectional view taken along the line -5 in Fig. 3.
Figure 7 is a cross-sectional view taken along the line ``-'', Figure 7 is a diagram showing an example in which the coating material in Figure 3 is made of multiple layers, and Figure 8 is a sectional view taken along the line ``-'' in Figure 7.
Line sectional view, Figure 9, Figure 11, Figure 13, Figure 15
The figures show an example in which a heat insulating material is attached to the outer periphery of the covering material shown in Fig. 1, Fig. 3, Fig. 5, and Fig. 7, respectively. Fig. 10 is a sectional view taken along the line - - of Fig. 9, and Fig. 12. is a sectional view taken along the line XII--XII in Fig. 11, Fig. 14 is a sectional view taken along the - line in Fig. 13, Fig. 16 is a sectional view taken along the - line in Fig. 15, and Fig. 17 is a perspective view showing the inner shape of the covering material. Fig. 18 is a perspective view showing another inner surface shape of the coating material, Fig. 19 is a perspective view of the sheathed heater attached to the sheathing material of Fig. 17, and Fig. 20 is a perspective view of the coating material installed on the sodium pipe. It is a diagram showing an example in which a detector and an inert gas supply pipe are further attached. 1... Sodium piping, 2... Covering material, 5...
Exterior material.

Claims (1)

[Scope of Claims] 1. A coating method for sodium piping, in which sodium piping is coated with a coating material made of a sodium-resistant material molded using a sodium-resistant binder, and an exterior material is wrapped around the outer periphery of the coating material. . 2. A sodium pipe in which the coating material is formed in advance into a plurality of vertically divided cylindrical shapes and the vertically divided cylindrical covering materials are successively attached to the sodium pipe in the circumferential direction to cover the sodium pipe in the construction method according to claim 1. Covering method. 3 In the construction method described in claim 2, the joints of the vertically split cylindrical covering material attached in the circumferential direction are adhered with a sodium-resistant adhesive joint agent, and the outer periphery of the covering material is further bonded to stainless steel wire. A coating method for sodium piping in which the sodium piping is tied up and covered with a covering material. 4 In the construction method described in claim 1, the coating material is formed into a longitudinally divided cylindrical shape with multiple layers in the radial direction of the sodium pipe and each layer is divided into multiple sections in the circumferential direction, and the coating material on the inner layer side is formed into a vertically divided cylindrical shape. A coating method for sodium piping in which the materials are sequentially attached in the circumferential direction, and then the outer layer coating material is sequentially attached to the outer periphery of the material to cover it in multiple layers. 5. A coating for sodium piping in which metal sodium guiding grooves are formed in the axial direction of the inner surface of the coating material in contact with the bottom of the sodium piping in the construction method according to any one of claims 2, 3, and 4. Construction method. 6. A coating method for sodium piping according to claim 5, in which a groove is formed on the inner surface of the coating material in contact with the sodium piping to guide leaked metallic sodium to the guiding groove. 7 Molding a coating material from a sodium-resistant material using a sodium-resistant binder, forming grooves for guiding metallic sodium on the inner surface of the coating material, coating the sodium piping with the coating material, and molding the coating material around the outer periphery. A metal sodium detector is arranged to face the guiding groove formed on the inner surface of the covering material, and an inert gas supply pipe is connected to the detector, and a supply valve of the inert gas supply pipe is connected to the detector. A coating method for sodium piping that is linked by a control device. 8. A coating for sodium piping in which the coating material is formed in advance into a plurality of vertically divided cylindrical shapes to cover the sodium piping and a guide groove is positioned at the bottom of the sodium piping in the construction method according to claim 7. Construction method.