JP2002357693A - Manufacturing method of radioactive material containment vessel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radioactive material containment vessel requiring little labor hour for manufacturing. SOLUTION: A metal billet 202 used for hot expansion molding comprises an upper rim 202a and a lower rim 202b on both ends, and the sectional shape thereof is substantially the same as the inside sectional shape of a molding container 300. The lower rim 202b in a pressing forward side has a taper 205 so that the outer shape is minimized toward the pressing direction. The middle part of the metal billet 202 is formed so that the sectional area corresponds to the difference between the inside sectional area of the molding container 300 and the sectional area of a boring punch 400. After the metal billet 202 is inserted to the molding container 300, the billet 202 is hot expansion-molded by the boring punch 400.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a radioactive material storage container for storing, transporting and storing radioactive materials such as spent nuclear fuel, and integrally forming a body and a bottom.

[0002]

2. Description of the Related Art A cask for storing, transporting, and temporarily storing radioactive materials such as spent nuclear fuel generated from a nuclear reactor uses a vessel having a height and diameter of a cylinder of several meters. ing. Some containers have a thickness of about several tens of centimeters from the viewpoint of shielding γ-rays. Next, a conventional radioactive substance storage container used for such a cask will be described.

FIG. 17 is a sectional view showing an example of a conventional cask. The cask 500 includes a radioactive material storage container 501 made of stainless steel or carbon steel, a basket 502 disposed in the radioactive material storage container 501 to store a spent fuel assembly, and an outer periphery of the radioactive material storage container 501. And a neutron shield 503 provided. The neutron shield 503 is filled in the space between the outer cylinder 504 and the radioactive material storage container 501, and a plurality of heat transfer fins (not shown) are provided between the radioactive material storage container 501 and the outer cylinder 504. Have been. Basket 5
For 02, a material to which boron having a neutron absorbing ability is added is used.

[0004] The container 501 has a container body 501a and a container bottom 501b made of stainless steel or carbon steel and is formed by TIG welding (tungsten-inert gas welding) or SIG.
AW (submerged-arc welding) is performed. A neutron shielding material 506 is sealed in the container bottom 501b. A primary lid 507 and a secondary lid 508 are attached to the upper part of the radioactive substance storage container 501 by bolts. A neutron shielding material 509 is sealed in the secondary lid 508.

The gamma rays generated from the spent fuel assembly are as follows:
It is shielded by the radioactive substance storage container 501, the container bottom 501b, the primary lid 507, and the secondary lid 508. The neutrons are supplied to a neutron shielding member 503 provided on the outer periphery of the radioactive substance storage container 501, a container bottom 501 b and a secondary lid 508.
Are shielded by the neutron shielding materials 506 and 509 enclosed in the. The decay heat of the spent fuel assembly is transmitted from the radioactive substance storage container 501 to the outer cylinder 504 via the heat transfer fins, and is radiated to the outside from there.

Next, a method used to manufacture the radioactive substance storage container 501 shown in FIG. 17 will be described. FIG. 18 is an explanatory diagram illustrating an example of a method of manufacturing the container body illustrated in FIG. First, FIG.
As shown in (1), a metal billet 61 forged and stretched to a predetermined size is installed on an anvil 62 having a perforated hole, and a punch 63 is used to make a hole. Next, as shown in FIGS. 7B to 7C, the mandrel 65 is passed through the hole 64 of the metal billet 61, and the hole 64 is widened by the hammer 66 while rotating. Subsequently, as shown in FIG. 2D, the mandrel 67 is replaced with a large-diameter mandrel, and hollow forging is performed using a hammer 68. As a result, the metal billet 61 is made thinner, and a cylindrical container body is formed ((e) in the figure).

After molding the cylindrical container body 501a,
The container bottom 501b is welded to its lower part. Further, a heat treatment is performed on the radioactive substance storage container 501 in order to remove thermal stress and the like due to the welding.

[0008]

However, in the above-mentioned conventional cask 500, the container bottom 501b is joined to the container body 501a by welding, so that the radioactive substance storage container 5 can be used.
01, it is necessary to perform heat treatment after welding. Here, since the radioactive material storage container used for the cask 500 stores a fuel rod assembly having a length of several meters and needs a function of shielding γ-rays emitted therefrom,
It is made of carbon steel or stainless steel with a thickness of several tens of cm. The inside diameter of the fuel rod assembly is set at 2.
It ranges from 0m to 2.5m. As described above, since the radioactive substance storage container 501 used in the cask 500 is a large and thick-walled container, there is a problem that the welding and the subsequent heat treatment require a long time, and the production is troublesome.

In order to solve this problem, it is conceivable to integrally form the bottom and the body of the radioactive substance storage container used in the cask 500 by a backward extrusion method (not shown). Here, the backward extrusion processing method refers to the following processing method. That is, after charging a metal billet having a circular cross section substantially equal to the inner diameter of the container into the container, the metal flow between the punch and the container is caused by the compressive force of the punch pressed along the central axis of the metal billet. Wake up. Then, the metal billet is formed into a long cylindrical shape while the metal is raised rearward in the pressing direction.

[0010] However, in the backward extrusion method, when the size and thickness of the container to be molded are increased, the pressure required for pressing becomes extremely large. Therefore, it is difficult to manufacture a radioactive substance storage container having a large size as used in the cask 500 as a bottomed container in which the bottom and the body are integrated by the backward extrusion method. Also,
In the backward extrusion method, a metal billet is formed while generating high friction between the container and the metal billet. For this reason, many defects such as pock-like flaws and streak-like flaws are generated on the surface of the molded container, and there is a problem that the reworking operation requires a long time. Then, this invention was made in view of the above, and an object of this invention is to provide the manufacturing method of the radioactive material storage container which does not require effort for manufacture.

[0011]

In order to achieve the above object, a method for manufacturing a radioactive substance storage container according to the first aspect of the present invention provides a method for manufacturing a radioactive substance storage container, comprising the steps of: A metal billet containing the area of the cross section perpendicular to the axial direction of the forming container and the area of the cross section perpendicular to the axial direction of the perforated punch is stored in the forming container by the perforated punch. It is characterized in that the container is formed integrally with the bottom by hot expansion molding toward the inner surface.

In the method for manufacturing a radioactive substance storage container, the cross-sectional area of the metal billet is defined as a difference between the inner cross-sectional area of the molding container and the cross-sectional area of the punch. For this reason, even if the metal punch is pressed into the metal billet to form the metal billet, the metal only moves to the gap existing between the metal billet and the forming container. That is,
The press thrust applied to the punch is consumed only for the movement of the metal, and no metal flows between the metal and the forming container in the direction of the inner surface of the forming container. Therefore, the pressing thrust hardly increases even if the forming proceeds, so that the hot expansion forming can be performed with a small pressing thrust.

[0013] Further, this manufacturing method includes a large and thick radioactive substance storage container formed integrally with a bottom and a body used for a cask, and a relatively thin bottom and a body used for a canister. The present invention is also applicable to a radioactive substance storage container formed integrally (the same applies hereinafter). In the rear extrusion method, a metal body is formed between the punch and the forming container by raising a metal flow that rises rearward in the pressing direction to form the container body. Therefore, it is necessary to overcome the frictional force generated between the metal flow and the molding container and to provide a pressing thrust for raising the metal of the billet to be formed rearward in the pressing direction. Therefore, in the backward extrusion method, a press thrust larger than that required for the manufacturing method according to the present invention is required.

According to a second aspect of the present invention, there is provided a method for manufacturing a radioactive substance storage container, comprising: forming a metal billet having projecting rims at both ends and having a cross-sectional shape in the axial direction substantially shaped like a bobbin; In a molding container
The container is molded integrally with the bottom by hot expansion molding toward the inner surface of the molding container with a perforated punch.

In this method for manufacturing a radioactive substance storage container, a metal billet provided with rims at both ends is used. Therefore, the metal billet is installed in a molding container without eccentricity. For this reason, the center of the perforated punch and the metal billet are substantially coincident with each other, so that the hot expansion molding can be performed, so that the unevenness of the container thickness due to the eccentricity of the metal billet can be suppressed.
Also, when the punch is pushed into the metal billet, the overhang portion is first pressed against the inner wall side of the molding container, and the metal billet restrains the movement in the pressing direction, so that the metal billet can be prevented from being upset. . Furthermore, in this method for producing a radioactive material storage container, since the molding container having the outer shape of the container to be molded on its inner surface is used, the outer shape of the cross section perpendicular to the axial direction is not only circular, but also rectangular or octagonal. Bottomed containers can also be molded. Further, FIG.
If a molding container as shown in FIG. 16 is used, a bottomed container having a nozzle at the bottom can also be molded.

According to a third aspect of the present invention, there is provided a method for manufacturing a radioactive substance storage container, wherein the rim is provided at both ends, and the rim on the front side in the pressing direction is formed so as to become narrower in the pressing direction. The metal billet in a molding container having the outer shape of the container to be molded on its inner surface,
The container is molded integrally with the bottom by hot expansion molding toward the inner surface of the molding container with a perforated punch.

In the method for manufacturing a radioactive substance storage container,
The rim of the metal billet on the front side of the press is formed in a substantially truncated cone shape narrowing in the pressing direction. That is, since the rim portion of the metal billet on the press front side is provided with a taper, there is a gap between the metal billet and the molding container. Then, in the final stage of the forming process, the metal on the front side in the pressing direction expands into this gap, so that it is possible to suppress an increase in the pressing thrust. Further, since a minute metal flow can be generated in the pressing direction, the degree of forging near the bottom of the container can be increased. Here, the front side in the pressing direction of the metal billet refers to the side in the traveling direction of the punch in punching the metal billet with the punch.
The side opposite to the front side in the pressing direction is the rear side in the pressing direction of the metal billet (the same applies hereinafter).

According to a fourth aspect of the present invention, in the method for manufacturing a radioactive substance storage container, the outer diameter of the projecting rim at both ends of the metal billet is the inner diameter of the molding container. It is characterized by being substantially equal in size.

In this method for manufacturing a radioactive substance storage container, since the outer diameter of the projecting rim at both ends of the metal billet is substantially equal to the inner diameter of the molding container, the metal billet can be formed without eccentricity. Installed in a container. For this reason, the center of the perforated punch and the metal billet are substantially coincident with each other, so that the hot expansion molding can be performed, so that the unevenness of the container thickness due to the eccentricity of the metal billet can be suppressed.

According to a fifth aspect of the present invention, in the method for manufacturing a radioactive substance storage container, a substantially central portion of an end surface of the metal billet on the rear side in the pressing direction is pressed by the punch. Pressing, and forming the container integrally with the bottom by hot expansion molding toward the inner surface of the molding container.

In this method for manufacturing a radioactive substance storage container, since the center of the end face of the metal billet on the rear side in the pressing direction is pressed by the punch, the center of the punch and the metal billet substantially coincide with each other. Can be expanded during molding. As a result, it is possible to suppress unevenness in the container thickness due to the eccentricity of the punch.

According to a sixth aspect of the present invention, in the method for manufacturing a radioactive substance storage container, the cross-sectional shape perpendicular to the axial direction of the punch is perpendicular to the axial direction of the container to be molded. It has a characteristic cross-sectional shape. The cross-sectional shape perpendicular to the axial direction of the perforated punch used in this manufacturing method is a cross-sectional shape perpendicular to the axial direction of the container to be molded. Therefore, by changing the cross-sectional shape of the perforated punch, it is possible to form a radioactive substance storage container in which a bottom and a body having various shapes and an inner cross section perpendicular to the axial direction are integrally formed.

According to a seventh aspect of the present invention, in the method for manufacturing a radioactive substance storage container, a cross-sectional shape parallel to an axial direction at a tip of the punch is formed at a bottom portion of the container to be molded. It is characterized in that it has a cross-sectional shape parallel to the axial direction. The tip shape of the punch used in this manufacturing method is the shape inside the container at the bottom of the container to be molded as it is. For example, if the shape of the tip of the perforated punch is hemispherical, the inner shape at the bottom of the radioactive substance storage container to be formed also becomes hemispherical. In addition, a forming container 310 and a punch 4 as shown in FIG.
08, a bottomed container 270 having a nozzle 271 at the bottom can also be formed. For this reason, the step of welding the nozzle to the bottom of the container and the post-weld heat treatment step, which are conventionally required, become unnecessary, and the manufacturing process of the container having the nozzle can be reduced.

According to a eighth aspect of the present invention, in the method for manufacturing a radioactive substance storage container, the punch is a split punch made up of a plurality of members, and is a hole penetrating in the pressing direction. And, at least two or more members whose cross section perpendicular to the pressing direction is shaped to increase from the outside of the punch to the hole, a member arranged between the members and combined with the member, And a member to be inserted.

Since the hot-formed container shrinks when cooled, it is impossible to take out the perforated punch remaining at the bottom of the container after the hot expansion molding, and conventionally, the perforated punch was left at the bottom of the container. . In the method for manufacturing a radioactive substance storage container, since the perforated punch is a divided punch,
By taking the reverse procedure of assembling the perforated punch, the perforated punch can be easily taken out of the container even after the completion of the hot expansion molding.

According to a ninth aspect of the present invention, in the method for manufacturing a radioactive substance storage container, the punch having a hole is provided with a hole penetrating in the axial direction. And a leading punch inserted into the through hole in a state in which the metal billet can be slid relative to the axial direction of the metal billet. After the forming by the leading punch, the metal billet is formed by the forming punch. It is characterized by doing.

In this method for manufacturing a radioactive substance storage container, a metal billet is hot-expanded and formed in two stages, a leading punch and a forming punch, so that it can be formed even with a smaller press thrust than forming with a single punch. it can. Therefore,
Capital investment for introducing a large press can be reduced. Further, with the same pressing thrust, a radioactive substance storage container in which a large-sized thick bottom and a body are integrally formed can be formed as compared with the case of forming with a single punch.

Further, in this method for manufacturing a radioactive substance storage container, a forming container 310, a leading punch 428 and a forming punch 438 as shown in FIG. 16 can also be used. Using these punches and containers, the last container of the bottom
By punching through the bottom of 0, the bottomed container 270 integrally provided with the nozzle 271 at the bottom can also be formed by the method for manufacturing a radioactive substance storage container. For this reason, the step of welding the nozzle to the bottom of the container and the post-weld heat treatment step, which are conventionally required, become unnecessary, and the manufacturing process of the container having the nozzle can be shortened.

According to a tenth aspect of the present invention, in the method for manufacturing a radioactive substance storage container, at least one of the leading punch and the forming punch is divided in an axial direction. And
In this method for manufacturing a radioactive material storage container, since the punch is divided in the axial direction, even when the height of the press and the stroke of the press cannot be sufficiently secured, the bottom and the body are integrally formed. A large-sized radioactive substance storage container having a large thickness can be formed.

Further, in the method for manufacturing a radioactive substance storage container according to the present invention, in the method for manufacturing a radioactive substance storage container, a recess is provided substantially at the center of an end surface of the metal billet on the rear side in the pressing direction. And According to the method for manufacturing a radioactive substance storage container, since the concave portion is provided substantially at the center of the end face on the rear side in the pressing direction of the metal billet, positioning of the preceding punch becomes easy, and the pressing thrust during expansion molding can be reduced. .

According to a twelfth aspect of the present invention, in the method for manufacturing a radioactive substance storage container, the forming punch is a split punch composed of a plurality of members, and has a cross section perpendicular to the pressing direction. Characterized by comprising at least two or more members having a shape that increases from the outside of the forming punch toward the hole penetrating in the axial direction, and a member disposed between the members and combined with the member. I do. In the method for manufacturing a radioactive substance storage container, since the forming punch of the perforated punch having the double structure is a divided punch, the procedure for assembling the forming punch is reversed, and the hot expansion molding is completed. After this, the punch can be easily taken out of the container.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. The present invention is not limited by the embodiment. In addition, components in the following embodiments include components that can be easily assumed by those skilled in the art.

(Embodiment 1) FIG. 1 is an explanatory view showing a method for manufacturing a radioactive substance storage container according to Embodiment 1. This manufacturing method uses a metal billet in hot expansion molding, where the cross-sectional area perpendicular to the axial direction is the difference between the internal cross-sectional area perpendicular to the axial direction of the forming container and the cross-sectional area perpendicular to the axial direction of the punch. There is a feature in that. That is, by using the symbols in the figure, relationship ^{_{πd 1 2/4 = πD 1}} 2/4-πd 0 2/4 is satisfied (refer to FIG. 1 (a) and (c)). Note that this relationship includes a case where the sectional area perpendicular to the axial direction of the metal billet is equal to the difference between the inner sectional area perpendicular to the axial direction of the forming container and the sectional area perpendicular to the axial direction of the punch. And the difference is included to within ± 10%. This is in consideration of a dimensional error of the metal billet. Then, in order to further suppress the increase in the pressing thrust and to increase the dimensional accuracy of the formed container, it is desirable that the cross-sectional area perpendicular to the axial direction of the metal billet be within ± 5% of the difference. . Note that hot expansion molding refers to a method in which a punch is punched into a metal billet heated to a temperature suitable for hot working, whereby the metal billet is expanded toward the inner wall side of the molding container to form a container.

In hot expansion molding, metal billet 2
00 is heated in a heating furnace (not shown) to a temperature that facilitates hot expansion molding. Since the heating temperature is determined by the material of the metal billet 200 and the like, it is not uniquely determined. In the case of a carbon steel material used for the body of a cask for storing, transporting, and temporarily storing spent nuclear fuel, it is desirable that the heating temperature be 1100 ° C. to 1300 ° C. If the amount exceeds this range, the crystal grains become coarse and the surface is oxidized and decarburized, and the material becomes brittle and easily cracks. In the case of carbon steel, the heating temperature decreases within the above range as the ratio of carbon increases.

The metal billet 200 heated to a temperature at which hot expansion molding is easy in an electric furnace or the like is loaded into a molding container 300 as shown in FIG. The metal billet 200 is provided with a projection 201 protruding radially outward at an end on the rear side in the pressing direction, and the center of the metal billet 200 can be held substantially at the center of the molding container 300 by this projection. As shown in FIG. 1, the molding container 300 has a cylindrical shape, which is the outer shape of a bottomed container 250 that is a radioactive substance storage container to be molded, on the inner surface of the molding container 300.

The metal billet 200 is formed into a container 30 for molding.
After the insertion, the punch 400 having a circular cross section perpendicular to the axial direction is placed on the upper end of the metal billet 200. At this time, the punch 400 and the container 300 are formed in advance.
Is confirmed, and the punch 400 is positioned substantially at the center of the end face on the rear side in the pressing direction of the metal billet 200 and substantially at the center of the molding container 300.

Next, after the punch 400 is placed on the metal billet 200, the punch 400 is pressed into the metal billet 200 by a press (not shown) to hot-expand the metal billet 200. Then, since the metal existing directly below the punch 400 cannot move to the front side of the press, the metal at the front side of the press deforms so as to be pushed and spread to the inner wall side of the molding container 300 without repulsion.

As described above, since the cross-sectional area of the metal billet 200 is defined as the difference between the inner cross-sectional area of the forming container 300 and the cross-sectional area of the punch 400, in this modification, the metal billet 200 and the forming container 300 The metal simply moves into the gap (portion indicated by A in FIG. 1) existing between the two. Therefore, the press thrust applied to the punch 400 is consumed only for the expansion molding, so that the press thrust hardly increases even if the molding proceeds. For this reason, the thick and large bottomed container 250 can be formed by a relatively small press machine (see FIG. 1C), and the manufacture of the radioactive substance storage container is facilitated. If a large-sized press is used, a larger bottomed container 250 can be manufactured.

FIG. 2 is a cross-sectional view perpendicular to the axial direction showing a punch used in the first embodiment. If a bottomed container is formed by selecting a punch having a cross section close to the outer shape of the cross section of the object stored inside the bottomed container to be formed, it is not necessary to process the inside of the container after forming, so that radioactive Manufacture of the substance storage container is facilitated. As such a punch, for example, there is a punch having a polygonal cross section perpendicular to the axial direction of the punch. Specifically, the punch 40
As shown in FIG. 1, the cross-sectional shape perpendicular to the axial direction is a quadrangle (the same figure (a)), and the cross-sectional shape perpendicular to the axial direction is an octagon like a punch 402. (FIG. 2B). In the case where the outer shape of the cross section of the object to be stored in the molded bottomed container is circular, FIG.
May be used.

Further, like the punch 403, the cross section may have a square corner with a stepped shape (FIG. 3C). This shape is also included in the polygon of the present invention. The punch 40 having such a cross-sectional shape
When the container is formed in step 3, the inside of the container is also formed into a stepped cross-sectional shape at the corners. Therefore, when the inside of the container is internally cut in order to match the outer shape of the basket for storing the fuel rod assembly, a small amount of shaving is required, so that processing is not troublesome and economical. The shape of the inside of the cross section of the molding container is not limited to a circle, but may be a polygon such as a quadrangle or an octagon, an ellipse, or the like, if necessary, to form a bottomed container having an arbitrary outer shape.

FIG. 3 is an axial cross-sectional view showing a modification of the perforated punch according to the first embodiment. This punch 40
Nos. 4 to 406 and 408 are characterized in that the cross-sectional shape parallel to the axial direction at the tip is matched to the internal shape parallel to the axial direction at the bottom of the container to be molded. With this configuration, the inner shape of the bottom of the container for various purposes can be formed by a single process, so that the container can be easily manufactured. Examples of the punches according to this modification include, for example, those shown in FIGS.
In addition, these perforated punches can also be applied to a method for manufacturing a bottomed container which is a radioactive substance storage container described later.

Further, if a punch 408 as shown in FIG. 3D is used, a projection 408a
Thus, a hole can be formed in the bottom of the container, and if the shape of the bottom of the forming container is devised, a bottomed container having a nozzle at the bottom can also be formed.

FIG. 15 is an explanatory view showing an example of a method of manufacturing a bottomed container integrally provided with a nozzle at the bottom using the perforated punch. The punch 408 used in this manufacturing method has a projection 408a at the tip. Further, the molding container 310 is provided with a depression 310a at the bottom thereof for molding a nozzle in order to have the outer shape of the container to be molded on its inner surface.

In the final step of forming the bottomed container 270,
The protrusion 408a provided on the punch 408 pushes the metal at the bottom of the container into the depression 310a provided on the container 310, and further presses the punch 408 into the protrusion 408a.
Penetrates the bottom of the container to complete the molding. In this molding process, the outer shape at the bottom of the bottomed container 270 is
The inner shape at the bottom of the forming container 310 provided with 10 a is the outer shape of the punch 408 at the bottom of the bottomed container 270. Therefore, if such a punch 408 and the molding container 310 are used,
By the method for manufacturing a container according to the first embodiment, a bottomed container 270 integrally provided with a nozzle 271 at the bottom can be manufactured.

Conventionally, the nozzle was attached to the bottom of the vessel by welding, so that welding and a post-weld heat treatment step were required. According to this manufacturing method, since the nozzle can be formed integrally with the container bottom, the welding and post-weld heat treatment steps are not required, and the manufacturing process of the container including the nozzle can be shortened. Especially when the container is large or the container is thick, the heat treatment step after welding requires much time and heat energy. For example, in a bottomed container used for a cask which is a used nuclear fuel storage container, it took about one month for the heat treatment step after welding. However, according to this manufacturing method, the welding and the heat treatment step after welding can be omitted, so that the construction period can be shortened for at least one month. The perforated punch and the molding container can be applied to a method for manufacturing a bottomed container described below.

(Embodiment 2) FIG. 4 is an explanatory view showing a method for manufacturing a radioactive substance storage container according to Embodiment 2. This manufacturing method is characterized in that a metal billet having a substantially thread-shaped cross section in the axial direction is used in hot expansion molding. An upper rim 202a and a lower rim 202b are provided at both ends of the metal billet 202 according to the second embodiment, and the cross-sectional shape is substantially the same as the inner cross-sectional shape of the molding container 300. The cross-sectional dimension of the portion where the upper rim 202a and the lower portion 202b are provided is also substantially the same as the inner cross-sectional size of the molding container 300.
Then, the lower rim 202b on the front side in the pressing direction
Is provided with a taper 205 so that the outer shape becomes smaller in the pressing direction. Also, the middle portion of the metal billet 202, that is, the portion where the upper rim 202a and the lower rim 202b are not present, is such that the cross-sectional area is the difference between the inner cross-sectional area of the molding container 300 and the cross-sectional area of the punch 400. Is molded.

The metal billet 202 formed into a predetermined shape and size by forging or cutting is heated to a temperature suitable for hot expansion forming, and then charged into a forming container 300. At this time, if the lower rim 202b does not exist, the metal billet 202 may be eccentrically installed in the molding container 300 as shown in FIG. In this case, the punch 400 is pushed into the metal billet 202 with a deviation y between the punch 400 and the center of the metal billet 202. Then, at the time of expansion molding, the punch 400 is moved by the arrow J by the metal flowing from the center of the metal billet 202.
(FIG. 4 (d)). Then, due to the eccentricity of the punch 400, the thickness of the formed container is deviated.

The metal billet 202 according to the second embodiment
Since the shape and dimensions of the cross section in the portion where the upper rim 202a and the lower rim 202b are provided are substantially the same shape and dimensions as the inner cross section of the molding container 300, the front side in the pressing direction and the pressing direction The rear side is held at the center of the molding container 300. Therefore,
The metal billet 202 is not eccentric and the molding container 30
It is set in 0. For this reason, the hot expansion molding can be performed in a state where the center of the punch 400 and the center of the metal billet 202 are substantially coincident with each other, so that the uneven thickness of the molded container due to the eccentricity of the metal billet 202 can be suppressed. The dimension of the cross section in the portion where the rim is provided is desirably 95% or more, more preferably 98%, of the inner cross sectional dimension of the molding container during hot expansion molding.
% Is appropriate. In this case, the effect of suppressing the eccentricity and the effect of suppressing the upsetting of the metal billet described below can be sufficiently exhibited.

The upper rim 202a provided on the rear side in the pressing direction has a cross-sectional shape and dimensions of the molding container 30.
Since the punch is pressed into the metal billet, this portion is pressed against the inner wall of the molding container 300 because it has substantially the same shape and substantially the same size as the inside cross section of 0. Since the movement of the metal billet 202 in the pressing direction is restricted by this action, the upsetting phenomenon of the metal billet 202 that occurs when the punch 400 is pushed into the metal billet 202 can be suppressed. As a result, the flow of the metal in the direction opposite to the pressing direction is reduced, and the increase in the pressing thrust can be suppressed.

In order to further increase the restraining force of the metal billet 202 in the pressing direction, the end of the metal billet 202 on the rear side in the pressing direction is formed at the entrance of the forming container 300 before hot expansion molding with the punch 400. It may be extended to the side end. In addition, metal billet 202
At the end on the rear side in the pressing direction, a projecting portion that engages with the entrance-side end of the molding container 300 may be provided. In this case, even if the forming punch 400 is pushed into the metal billet 202, the overhanging portion is engaged at the entrance side end of the forming container 300, so that the metal billet 202 cannot be further set up. Absent. For this reason,
The flow of metal in the direction opposite to the pressing direction can be more effectively reduced, and an increase in pressing thrust can be suppressed.

The cross-sectional area at the intermediate portion of the metal billet 202 is a difference between the inner cross-sectional area of the forming container 300 and the cross-sectional area of the punch 400 as described in the first embodiment. For this reason, in the hot expansion molding process, the metal merely moves to the gap existing between the metal billet 202 and the molding container 300, and the pressing thrust hardly increases even if the molding proceeds.

Since the lower rim 202b on the press front side of the metal billet 202 is provided with the taper 205, there is a gap between the metal billet 202 and the molding container 300. In the final stage of the forming process, the metal at the front side of the press expands into this gap, so that an increase in the press thrust at this stage can be suppressed. Also, this taper 2
Since a minute metal flow in the pressing direction occurs at the portion 05, the degree of forging at the bottom of the container can be increased. The hot expansion forming is completed by pushing the punch 400 to a predetermined depth, but at this time, if the bottom is left, a bottomed container in which the bottom and the body are integrated can be formed.

It is to be noted that a cylindrical spacer (not shown) may be provided on the bottom and the bottom may be punched to form a cylinder. In addition, the outer shape of the punch 400 or the container 30 for molding.
By appropriately changing at least one of the inside shapes of 0, a cylinder and a bottomed container having a desired outer shape or inner shape can be formed. For example, if a forming punch as shown in FIGS. 2 and 3 is used, a bottomed container having a polygonal cross section perpendicular to the axial direction or a bottomed container having a hemispherical or conical bottom can be formed. By using a punch 408 and a forming container 310 as shown in FIG. 15, a bottomed container 270 having a nozzle 271 at the bottom of the container can be formed.

According to this production method, hot expansion molding can be performed with a relatively small pressing force, so that a large container can be molded with a relatively small press machine. Therefore, capital investment for introducing a large press can be suppressed. Also, with the same pressing thrust, a large container can be formed as compared with the backward extrusion method.

The metal billet applicable to the present embodiment is not limited to the one having rims at both ends. For example, as shown in FIG.
And 203b may be provided to keep the metal billet 203 at the center of the molding container. In particular, when the front side in the pressing direction has this structure, a larger gap can be formed between the rim and the forming container 300 than when the rim is tapered (see FIG. 4A). In the final stage of the process, the increase in the press thrust can be further suppressed. The number of the projections 203a and 203b is not limited to the example shown in FIG.
In order to keep it at the center, three or more are desirable. Also, this projection is provided only on the front side in the pressing direction of the metal billet,
The overhanging rim may be provided on the rear side in the pressing direction. With this configuration, the rim is pressed against the inner surface of the molding container during molding, thereby suppressing upsetting of the metal billet, and suppressing an increase in press thrust in the final stage of molding.

(Embodiment 3) Next, another method of manufacturing a radioactive substance storage container will be described. FIG. 6 is an explanatory view showing an example of a punch used in the method for manufacturing a radioactive substance storage container according to the third embodiment. This manufacturing method is characterized in that a split punch composed of a plurality of members is used as a punch and hot expansion molding is performed. First, a member 410a having a cross section perpendicular to the pressing direction that increases in size from the outside of the punch having holes penetrating in the pressing direction toward the hole is combined with the member 410a disposed between the members 410a. Member 410
Combine with b. Then, an annular punch is formed ((a) in the figure), and a member 41 inserted into the hole is inserted into a central space (a region indicated by B in the figure) which is a hole penetrating in the pressing direction.
0c is incorporated. Next, a restraining member 418 is attached to a groove 417 provided on the side surface of the members 410a and 410b, and the members 410a and 410b are fixed (FIG. 10B) to form a punch and used for hot expansion molding. The shape of the hole (the area indicated by B in FIG. 6) penetrating in the pressing direction is not limited to a circle, but may be a polygon such as a quadrangle or an octagon.

When the members 410a to 410c are to be taken out of the formed metal billet (not shown), the members
c is withdrawn from members 410a and 410b,
The member 410a is moved to the central space (the area indicated by B in FIG. 6) into which the member 410c has been inserted, and is taken out.
The last remaining member 410b is the members 410a and 41
Oc can be taken out by moving to the space created by taking out Oc.

The annular punch may be formed by combining members 412a and 412b as shown in FIGS. 7A and 7B. Here, this member 412a is
It is characterized in that the cross-sectional shape parallel to the pressing direction becomes narrower in the pressing direction. Hot expansion molding is completed,
As the molded container cools and shrinks, members 412a and 412b forming the annular punch receive a force toward the center. The member 412a has a cross-sectional shape perpendicular to the pressing direction that increases from the outside to the inside of the member 412a. Therefore, when the member 412b receives a force inward in the radial direction due to the contraction of the container, a force for moving the member 412a in the center direction acts. Also, this member 412a
Since the cross-sectional shape parallel to the pressing direction becomes narrower in the pressing direction, a force toward the opposite side in the pressing direction also acts. By these actions, the members 412a and 412b can be easily taken out even after the molded container has cooled and contracted.

As described above, when the punches are constituted by the members 410a to 410c, the members 410a to 410c can be easily taken out when the metal billet 200 after molding is cooled and contracted. Note that the number of divisions of the annular punch is not limited to the number disclosed in the present embodiment.For example, in the case of a large punch, the number of divisions is increased to make it easier to handle. The number of divisions can be determined. FIG. 8C shows an example in which a punch having a polygonal cross section perpendicular to the axial direction is divided. As shown in the figure, even when the cross-sectional shape perpendicular to the axial direction of the perforated punch is a polygon, it can be a split punch.

FIG. 9 is an explanatory view showing a second modification of the punch of the third embodiment. This punch is
It is characterized in that the members 411a and 411b are connected to each other. Each of the members 411a and 411b has a connecting portion 415 formed of a concave portion and a convex portion on the inner peripheral side.
a and 415b are provided. When assembling the punch, the connecting portions 415a and 415b are combined with each other to connect the members 411a and 411b. Also, a protrusion 416a is provided on the side surface of the member 411a.
Is provided, and the protrusion 416a is provided with a member 411a.
When combined with and 411b, they are fitted into grooves 416b provided on the side surface of the member 411b. For this reason,
When assembling the member 411a and the member 411b, it is not necessary to fix the member 411a and the member 411b with a restraining material as in the above-described punching punch (see FIG. 6), and the assembling work is facilitated. Also, the groove 41
6b is provided at right angles to the pressing direction,
Even if the member 411c (see FIG. 9A) is not substantially T-shaped, the annular punch formed by combining the members 411a and 411b during hot expansion molding does not shift in the pressing direction. Therefore, in the punch of the present modification, a columnar member may be used as the member 411c.

(Embodiment 4) FIG. 10 shows Embodiment 4 of the present invention.
It is explanatory drawing which shows the manufacturing method of the radioactive substance storage container concerning this. This manufacturing method is characterized in that a metal billet is hot-expanded and formed using a perforated punch having a double structure in which a preceding punch is passed through a through hole of a formed punch, thereby manufacturing a radioactive substance storage container. The metal billet 202 formed into a predetermined shape and size by forging or the like is charged into a forming container 300 after being heated to a temperature suitable for hot expansion forming. In addition, the metal billet and the perforated punch described in the first embodiment (see FIGS. 2 and 3) can be applied to the method for manufacturing a radioactive substance storage container according to the fourth embodiment. Also, as described in Embodiments 1 and 2, if the tip shape of the forming container and the leading punch is devised, a bottomed container with a nozzle can be formed. This method will be described later.

FIG. 11 is an explanatory diagram showing a combination of the preceding punch and the forming punch. The leading punch 420 used in the manufacturing method according to the present embodiment is
Smaller in diameter than The cross-sectional shape of the preceding punch 420 is not limited to a circle, but may be a polygon such as a quadrangle. Also, the forming punch 430 is a leading punch 420
In order to hot-expand the metal billet 202 by penetrating it into the metal billet 202 (see FIG. 10), a through hole 435 having substantially the same diameter as the preceding punch 420 penetrating in the axial direction of the forming punch 430 is provided. The leading punch 420 is inserted into the through hole 435 so that it can slide relative to the axial direction of the forming punch 430. Next, an example in which hot expansion molding is performed by a plurality of presses while sequentially adding the leading punch 420 and the forming punch 430 divided in the pressing direction will be described.

FIG. 12 is an explanatory view showing steps of a method for manufacturing a radioactive substance storage container according to the fourth embodiment. When hot-expanding the metal billet 202, first press the leading punch 420a into the metal billet 202 (FIG. 12).
(A)). At this time, as shown in FIG. 13, a small-diameter recess 2 is previously formed in the end of the metal billet 202 on the rear side of the press.
06 (FIG. 13 (a)), and a small-diameter through-hole 2 that penetrates the metal billet 202 in the axial direction to the vicinity of the bottom.
07 can also be provided (FIG. 13B). By doing so, the positioning of the preceding punch 420a is facilitated, and the pressing thrust at the time of expansion molding by the molding punch 430 can be reduced. The metal billet 202
Is formed into a bottomless cylinder, the small-diameter through hole 20
7 may be provided.

When the leading punch 420a is pushed in, the pushing is stopped in a state where the leading punch 420a protrudes to some extent from the upper end surface of the metal billet 202 so as to serve as a positioning guide for the forming punch 430a to be pushed next (FIG. 12B). ). Next, the hole provided inside the forming punch 430a is fitted to the preceding punch 420a, and the forming punch 430a is pushed in (FIG. 12C). Again,
The pushing is stopped at an appropriate position before the upper end face of the forming punch 430a reaches the upper end face of the preceding punch 420a pushed in advance so that it can be used as a positioning guide for the preceding punch 420b to be used next (FIG. 12D). ).

Next, the leading punch 420b is placed on the leading punch 430a and pushed in (FIG. 12 (e)), and the forming punch 430b is placed on the forming punch 430a and pushed in (FIG. 12 (f)). By repeating the above procedure, the metal billet 202 is formed into an integrated container with a bottom. Note that, as described above, a cylinder can be formed by punching through the bottom. Also, by appropriately changing the outer shape of the forming punch 430a or the inner shape of the forming container 300, it is possible to form a cylinder or a bottomed integrated container having a desired outer shape or inner shape. For example, a bottomed container with a polygonal outer cross section perpendicular to the axial direction, a bottomed container with a polygonal inner cross section perpendicular to the axial direction, or a hemispherical shape or a bottomed container with a conical bottom shape it can.

In the above description, the leading punches 420a and 420b and the forming punch 43 divided in the axial direction are used.
Although 0a and 430b are used, the punch applicable to the present embodiment is not limited to this. For example, if the height of the press and the stroke of the press can be sufficiently ensured, a leading punch and a forming punch that are not divided in the axial direction can be used. At this time, since it is not necessary to add the leading punch and the forming punch, the time required for forming can be shortened.

In this manufacturing method, since the metal billet 202 is hot-expanded and formed in two stages of the pressing of the leading punch and the pressing of the forming punch, the forming can be performed with a smaller press thrust than forming with a single punch. it can. Therefore, capital investment for introducing a large press can be suppressed. Also, with the same pressing thrust, a large container can be formed as compared with the case of forming with a single punch.

Further, as described in the third embodiment, if the forming punch 430 is a split punch, the forming punch 430 can be easily taken out of the container. FIG.
FIG. 4 is an explanatory view showing an example in which the forming punch according to the fourth embodiment is a split punch. First, a hole 43 penetrating a cross section perpendicular to the pressing direction from the outside of the forming punch in the axial direction.
A member 431a having a shape increasing toward 5 and a member 431b arranged between the members 431a and combined with the member 431a are combined to form an annular punch (FIG. 7A). The through-hole 435 allows the preceding punch 420 to penetrate. Next, the members 431a and 431
A restraining member 438 is attached to a groove 437 provided on the side surface of the member 31b, and members 431a and 431b are fixed to form a forming punch (FIG. 13B), which is used for hot expansion forming.

When the members 431a and 431b are taken out of the formed metal billet (not shown), the preceding punch 420 is pulled out from the formed punch composed of the members 431a and 431b. Then, the member 431a is moved to the through hole 435 through which the preceding punch 420 has penetrated, and is taken out. The last remaining member 431b is a member 431a
And it can be taken out by moving to the space created by taking out the preceding punch 420. As described above, when the molding punch is divided, even if the molded container cools and shrinks, it can be easily taken out. As described in Embodiment 3, the number of divisions of the forming punch and the fact that the forming punch may be divided even when the cross-sectional shape perpendicular to the axial direction is polygonal may be used.

Further, as described in the third embodiment, a connecting portion may be provided between the forming punches and may be combined with each other. At this time, as shown in FIG. 9, when the protrusions 416a and the grooves 416b that mesh with each other are provided on the side surfaces of the members 411a and 411b that form the forming punch, the members 411a and 411b can be moved with respect to the pressing direction during hot expansion molding. It will not shift. In this case, there is no need to provide a means for preventing displacement in the pressing direction.
It is advantageous in a double punched punch in which the leading punch slides axially inside the molded punch.

Next, as another example of changing the inner shape of the forming container and the shapes of the forming punch and the preceding punch to form a bottomed integrated container having a desired outer shape or inner shape, a nozzle is provided at the bottom. The case of forming a bottomed container integrally provided will be described. FIG. 16 is an explanatory diagram illustrating an example of a method for manufacturing a bottomed container having a nozzle integrated with a bottom in Embodiment 4. The molding container 310 used in this manufacturing method is provided with a recess 310a at the bottom for molding a nozzle in order to have the outer shape of the container to be molded on its inner surface.

In the final step of forming the bottomed container 270,
The leading punch 428 pushes the metal at the bottom of the container into the depression 310 a provided in the container 310, and the leading punch 4
When the lead 28 is pushed in, the preceding punch 428 penetrates the bottom of the container and the molding is completed. In this forming process, the outer shape at the bottom of the bottomed container 270 becomes the inner shape of the bottom of the forming container 310 provided with the recess 310a, and the inner shape at the bottom of the bottomed container 270 becomes the outer shape of the forming punch 438. Therefore, if such a preceding punch 428, a formed punch 438, and a container 310 are used, the nozzle 27 at the bottom can be formed by the container manufacturing method according to the fourth embodiment.
1 can be manufactured integrally with the bottomed container 270. According to this manufacturing method, since the nozzle can be formed integrally with the container bottom, the welding and post-weld heat treatment steps are not required, and the manufacturing process of the container including the nozzle can be shortened.

[0073]

As described above, in the method for manufacturing a radioactive material storage container according to the present invention (claim 1), the area of the cross section perpendicular to the axial direction is reduced by the area of the cross section perpendicular to the axial direction of the molding container. The metal billet having a difference between the area of the cross section perpendicular to the axial direction of the punch and the punch was hot-expanded by the punch. For this reason, in the forming process, the metal only moves to the gap existing between the metal billet and the forming container. Therefore, since the press thrust applied to the punch is consumed only for the movement of the metal, the press thrust hardly increases even if molding proceeds, and a thick and large container in which the bottom and the body are integrated is used. Can be manufactured. For this reason, welding of the bottom plate and post-weld heat treatment become unnecessary, and the manufacture of the radioactive substance storage container does not require labor.

Further, in the method for manufacturing a radioactive substance storage container according to the present invention (claim 2), a metal billet having projecting rims at both ends and having an axial cross-sectional shape formed into a substantially wound rod shape is formed by a punching punch. The container was molded integrally with the bottom by hot expansion molding toward the inner surface of the molding container.
For this reason, the center of the perforated punch and the metal billet are substantially coincident with each other, so that the hot expansion molding can be performed, so that the uneven thickness of the molded container due to the eccentricity of the metal billet can be suppressed.
As a result, there is almost no need for modification after molding, and no trouble is required in manufacturing the radioactive substance storage container. Also, when the punch is pushed into the metal billet, the overhang is pressed against the inner wall side of the molding container, and the metal billet can be restrained from moving in the pressing direction to prevent the metal billet from being upset. Thrust is relatively small.
Therefore, without using a large press machine, it is possible to mold a thick and large container with the bottom and body integrated,
No effort is required to manufacture the radioactive material containment container.

In the method for manufacturing a radioactive substance storage container according to the present invention (claim 3), a rim on the front side of the press is formed by punching a metal billet formed into a substantially truncated conical shape narrowing in the pressing direction. To perform hot expansion molding. That is, since the rim portion on the press front side of the metal billet is provided with a taper,
There is a gap between the metal billet and the forming container. Then, in the final stage of the forming process, the metal on the front side in the pressing direction expands into this gap, so that it is possible to suppress an increase in the pressing thrust. Therefore, it is possible to form a thick and large container in which the bottom and the body are integrated without using a large-sized press machine. Also, since a minute metal flow can be generated in the pressing direction, the degree of forging of the bottom of the container to be formed can be improved.

In the method for manufacturing a radioactive material storage container according to the present invention (claim 4), the outer diameter of the projecting rim at both ends of the metal billet is substantially equal to the inner diameter of the molding container. The metal billet is installed in the molding container without eccentricity. For this reason,
Hot expansion molding can be performed in a state where the center of the perforated punch and the metal billet are substantially coincident with each other, so that the thickness deviation in the molded container due to the eccentricity of the metal billet can be suppressed. As a result, there is almost no need to modify the radioactive substance storage container after the container is formed, and it is not necessary to manufacture the radioactive substance storage container.

Further, in the method for manufacturing a radioactive material storage container according to the present invention (claim 5), in the method for manufacturing a radioactive material storage container, substantially the center of the end face on the rear side in the pressing direction of the metal billet is formed with the perforated punch. And pressurized. For this reason, the center of the perforated punch and the center of the metal billet substantially coincide with each other, and hot expansion molding can be performed. As a result, the thickness deviation in the molded container due to the eccentricity of the punch can be suppressed, so that the modification after molding is almost unnecessary,
No effort is required to manufacture the radioactive material containment container.

Further, in the method for manufacturing a radioactive substance storage container according to the present invention (claim 6), in the method for manufacturing a radioactive substance storage container, the cross-sectional shape of the perforated punch perpendicular to the axial direction is the container to be molded. In a cross section perpendicular to the axial direction. For this reason, by changing the cross-sectional shape of the perforated punch, radioactive substance storage containers having various shapes of internal cross-sections perpendicular to the axial direction can be formed. In addition, since processing of the inside of the container after molding is required to a minimum, no trouble is required for manufacturing the radioactive substance storage container.

In the method for manufacturing a radioactive substance storage container according to the present invention (claim 7), in the method for manufacturing a radioactive substance storage container, the cross-sectional shape parallel to the axial direction at the tip of the perforated punch may be a container to be molded. The inside shape of the cross-section parallel to the axial direction at the bottom of was obtained. Since the tip shape of the perforated punch used in this manufacturing method is the same as the inner shape of the container at the bottom of the container to be molded, radioactive substance storage containers having various inner shapes at the bottom can be molded. In addition, since processing of the inside of the container after molding is required to a minimum, no trouble is required for manufacturing the radioactive substance storage container. Furthermore, since the nozzle can be integrally formed at the bottom of the container, the conventionally required nozzle welding process and post-weld heat treatment process are not required.
The manufacturing process of a bottomed container equipped with a nozzle can be shortened.

In the method for manufacturing a radioactive substance storage container according to the present invention (claim 8), in the method for manufacturing a radioactive substance storage container, the punches are divided punches.
Therefore, by taking the reverse procedure of assembling the punch, the punch can be easily taken out of the container even after the hot expansion molding is completed. Therefore, no trouble is required for manufacturing the radioactive substance storage container.

Further, in the method for manufacturing a radioactive substance storage container according to the present invention (claim 9), in the method for manufacturing a radioactive substance storage container, the metal billet is divided into two stages of a leading punch and a forming punch. Expansion molding was performed. For this reason, molding can be performed with a smaller press thrust than molding with a single punch. Therefore, a thick large-sized radioactive substance storage container can be manufactured without using a large-sized press machine. Further, with the same pressing thrust, a radioactive substance storage container in which a large-sized thick bottom and a body are integrally formed can be formed as compared with the case of forming with a single punch.
Furthermore, since the nozzle can be formed integrally with the bottom of the container, the conventional welding step of the nozzle and the post-weld heat treatment step are not required, and the manufacturing process of the bottomed container equipped with the nozzle can be shortened.

In the method for manufacturing a radioactive substance storage container according to the present invention (claim 10), in the method for manufacturing a radioactive substance storage container, at least one of the preceding punch and the formed punch is divided in the axial direction. Even when the height of the press and the stroke of the press cannot be sufficiently secured, a thick and large radioactive substance storage container in which the bottom and the body are integrally formed can be formed.

In the method for manufacturing a radioactive material storage container according to the present invention (claim 11), in the method for manufacturing a radioactive material storage container, a concave portion is provided substantially at the center of an end surface of the metal billet on the rear side in the pressing direction. Because
It becomes easy to position the preceding punch. As a result, the hot expansion molding process can be started quickly, so that the time of the molding process can be shortened and no trouble is required for manufacturing the radioactive substance storage container. Further, the pressing thrust during expansion molding can be reduced.

In the method for manufacturing a radioactive material storage container according to the present invention (claim 12), the forming punch for the perforated punch having the double structure is divided in the method for manufacturing a radioactive material storage container. By taking the reverse procedure of assembling the punch, the molded punch can be easily taken out of the container even after the completion of the hot expansion molding. Therefore, no trouble is required for manufacturing the radioactive substance storage container.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a method for manufacturing a radioactive substance storage container according to Embodiment 1.

FIG. 2 is a cross-sectional view perpendicular to the axial direction showing a punch that can be used in the first embodiment.

FIG. 3 is an axial sectional view showing a modified example of the perforated punch according to the first embodiment.

FIG. 4 is an explanatory view showing a method for manufacturing a radioactive substance storage container according to a second embodiment.

FIG. 5 is an explanatory view showing a metal billet that can be used in the method for manufacturing a radioactive substance storage container according to the second embodiment.

FIG. 6 is an explanatory view showing an example of a punch used in the method for manufacturing a radioactive substance storage container according to the third embodiment.

FIG. 7 is an explanatory view showing an example of a punched punch used in the method for manufacturing a radioactive substance storage container according to the third embodiment.

FIG. 8 is an explanatory view showing an example of a punch used in the method for manufacturing a radioactive substance storage container according to the third embodiment.

FIG. 9 is an explanatory diagram showing a modification of the split punch according to the third embodiment.

FIG. 10 is an explanatory diagram showing a method for manufacturing a radioactive substance storage container according to Embodiment 4.

FIG. 11 is an explanatory view showing a combination of a leading punch and a forming punch.

FIG. 12 is an explanatory view showing steps of a method for manufacturing a radioactive substance storage container according to the fourth embodiment.

FIG. 13 is an explanatory view showing an example in which a recess is provided at the upper end of a metal billet.

FIG. 14 is an explanatory diagram showing an example in which the forming punch according to the fourth embodiment is a split punch.

FIG. 15 is an explanatory view showing an example of a method of manufacturing a bottomed container having a nozzle at the bottom integrally using the perforated punch.

FIG. 16 is an explanatory diagram showing an example of a method of manufacturing a bottomed container having a nozzle integrated with a bottom in Embodiment 4.

FIG. 17 is a sectional view showing an example of a conventional cask.

FIG. 18 is an explanatory view showing an example of a method of manufacturing the container body shown in FIG.

[Explanation of symbols]

 200, 202, 203 Metal billet 201, 203a, 203b Projection 202a Upper rim 202b Lower rim 205 Taper 206 Depression 207 Small diameter through hole 250, 270 Bottom container 271 Stub 300, 310 Molding container 310a Depression 400-408 Punch punch 408a Projection 410, 411, 412, 431 Member 415 Connection 416a Projection 416b Groove 420, 428 Leading punch 430, 438 Molding punch 435 Through hole 500 Cask 501 Radioactive substance storage container 501a Container trunk 501b Container bottom

Continuation of the front page (72) Inventor Shinji Ogame 5-1-1, Komatsu-dori, Hyogo-ku, Kobe F-term in Shinryo High-Tech Co., Ltd. (Reference) 3E033 AA20 BA07 CA20 DA02 FA01 GA03

Claims (12)

[Claims] In a molding container having an outer shape of a container to be molded on an inner surface thereof, an area of a cross section perpendicular to an axial direction is set to an area of a cross section perpendicular to an axial direction of the molding container and an axial direction of a punch. A radioactive material storage container characterized in that a metal billet having a difference from an area of a vertical cross section is stored therein, and a container is integrally formed with a bottom by hot expansion molding toward the inner surface of the molding container by the perforated punch. Production method. 2. A metal billet having projecting rims at both ends and having an axial cross-sectional shape formed into a substantially thread-wound rod shape is accommodated in a molding container having an outer shape of a container to be molded on its inner surface.
A method for producing a radioactive substance storage container, characterized in that a container is formed integrally with a bottom by hot expansion molding toward the inner surface of the molding container with a perforated punch. 3. A projecting rim is provided at both ends, and a projecting rim on the front side in the pressing direction is formed with a metal billet formed so as to become narrower in the pressing direction. In a molding container
A method for producing a radioactive substance storage container, characterized in that a container is formed integrally with a bottom by hot expansion molding toward the inner surface of the molding container with a perforated punch. 4. The method for manufacturing a radioactive substance storage container according to claim 2, wherein the outer diameter of the projecting rim at both ends of the metal billet is substantially equal to the inner diameter of the molding container. . 5. A substantially central portion of an end face of the metal billet on the rear side in the pressing direction is pressurized by the punch, and a bottom is integrally formed by hot expansion molding toward an inner surface of the molding container. Claims 1 to
5. The method for producing a radioactive substance storage container according to any one of 4. 6. The cross-sectional shape perpendicular to the axial direction of the perforated punch is an internal shape perpendicular to the axial direction of a container to be formed, according to claim 1, wherein: Manufacturing method of radioactive material storage container. 7. The cross-sectional shape parallel to the axial direction at the tip of the perforated punch is an internal shape parallel to the axial direction at the bottom of the container to be molded.
7. The method for producing a radioactive substance storage container according to any one of 6. 8. The punch is a split punch composed of a plurality of members, and has a hole penetrating in a pressing direction, and a cross section perpendicular to the pressing direction having a shape that increases from the outside of the punch to the hole. The member according to any one of claims 1 to 7, further comprising at least two or more members, a member disposed between the members and combined with the member, and a member inserted into the hole. 3. The method for producing a radioactive substance storage container according to 1.). 9. A punch having a hole penetrating in the axial direction, and a preceding punch inserted in the penetrating hole so as to be relatively slidable in the axial direction of the punch. The radioactive substance storage container according to any one of claims 1 to 7, wherein the metal billet is formed by the forming punch after the forming by the preceding punch. Production method. 10. The method for manufacturing a radioactive substance storage container according to claim 9, wherein at least one of the leading punch and the forming punch is divided in an axial direction. 11. The method for manufacturing a radioactive substance storage container according to claim 9, wherein a concave portion is provided substantially at the center of an end surface of the metal billet on the rear side in the pressing direction. 12. The forming punch is a split punch composed of a plurality of members, and has at least two sections each having a cross section perpendicular to the pressing direction having a shape that increases from the outside of the forming punch toward the hole penetrating in the axial direction. The method for manufacturing a radioactive substance storage container according to any one of claims 9 to 11, comprising: the above-mentioned member; and a member arranged between the member and combined with the member.