Tank protective container

Abstract: To improve impact resistance in case of falling or the like while shortening the overall length and reducing the size, a tank 1 having a valve 6 in a head portion 4 and protected by a substantially cylindrical head skirt portion 7 is accommodated in a protective container 2. A pressure receiving member 23 having a projection 23c, to which a free end 7a of the head skirt portion 7 is fixed, is disposed between the head skirt portion 7 and the head support members 11. The head support members 11 are formed into a triple-layer structure formed by stacking, when viewed from the tank, a first layer having strong deformation resistance, and second and third layers 15 and 16 having weak deformation resistance. The second layer 15 consists of an annular outer layer 15a having deformation resistance weaker than that of the first layer and an inner layer 15b fitted in the central space and having weaker deformation resistance. The third layer 16 is made of the same material as that of the outer layer. A metal rotation-stopper 20 is provided for the head skirt portion 7 so as to be attached to the protective container 2.

Description: The present invention relates to a protective container for accommodating and protecting a tank when the tank, in particular, a UF 6 tank, is stored or transported. Hitherto, a UF 6 tank filled with UF 6 has been stored or transported in such a manner that the tank is accommodated in, for example, an external protective container. The UF 6 tank (hereinafter called a "tank") is formed into, for example, a capsule-like shape and has a valve on one of spherical-surface-like end surfaces thereof. In the description of the present invention, the end on which having the valve is called a" tank head portion" and another end opposing the foregoing end is called a "tank bottom portion". A cylindrical skirt portion is formed on each of the head and bottom end of the tank. The protective container is formed into, for example, a cylindrical shape to be adaptable to the shape of the tank. The head portion and the bottom portion of the protective container are closed by disc-like support members made of an appropriate material (for example, oak wood) having appropriate impact resistance. Furthermore, a heat insulating member is placed in the side of the protective container. To mount and remove the tank, the protective container is divided into two sections along a plane including the lengthwise directional axis thereof, the two sections being connected to each other after the tank has been mounted. A protective container of the foregoing type is subjected to the drop tests and the thermal (fire) test which is performed after tests, in a state where the tank is accommodated so as to evaluate the safety against the accidental conditions. In particular, to protect the valve from being damaged if the tank falls or encounters a fire, the protective container must have satisfactory shock absorbing performance. Therefore, the foregoing support members having a predetermined thickness has been employed in each of the head and bottom portions of the protective container. The protective container is subjected to the tests or the like in which the protective container is caused to fall in such a manner that its container head portion faces downwards, and in which the support members of the container head portion of the protective container locally deform so that shock is dispersed and absorbed. As a result, the valve located inside of the skirt portion of the tank head portion of the tank can be protected from being damaged. However, the foregoing protective container having the structure such that the support members for each of the tank head portion and the tank bottom portion disperses and absorbs the shock involves a fact that the support members for each of the tank head portion and the tank bottom portion are thickened to protect the tank. Therefore, the overall length of the protective container cannot be shortened, and the size of the same cannot be reduced. Thus, a large space has been required to locate the protective container, and manufacturing, storing and transporting cannot be performed efficiently. Therefore, there arises a problem in that the cost cannot be reduced. DE-OS-2 311 162 reveals a protective container for accommodating and protecting a tank, in particular a barrel, which is to be filled with a radioactive substance. The tank comprises a tank chamber for containing the radioactive substance. Above the actual tank chamber there is a chamber-like tank portion whose upper end is closed by a cap. In said chamber-like tank portion there are arranged conduits leading into the tank chamber. The end portions of the conduits located in said chamber-like tank portion are provided with valves and conduit couplings for charging, draining and ventilating the tank chamber. The protective container has a two-piece structure and comprises a container head portion and an opposing container bottom portion with a space therebetween for accommodating said tank. To mount and remove the tank, the protective container is divided into two sections along a plane in a widthwise direction thereof, the two sections being connected to each other after the tank has been mounted. In view of the foregoing, an object of the present invention is to provide a protective container, the size of which can be reduced and with which the safety of the valve and the like can be improved. This object is achieved by a protective container according to the present invention comprising the features of claim 1. Impact generated when the protective container falls in such a manner that its head faces downwards and collides with the ground of the like is transmitted to the head support members while being dispersed and absorbed by the pressure receiving member. Therefore, a fear of intrusion of the free end of the tank head skirt portion into the head support members or expansion of the head support members toward the tank due to the impact load causing the valve to collide with the head support members can be eliminated. Moreover, since the projection fixes the free end of the tank head skirt portion, deformation of the tank head skirt portion can be prevented. The pressure receiving member consists of a bottom portion disposed between the tank head skirt portion and the head support members, a side wall portion stood erect of the radial directional outside of the bottom portion and formed along the outer surface of the tank head skirt portion, and a projection stood erect from the bottom portion and formed on the inside of the side wall portion. Therefore, the impact resistance can be improved and the head support members can be thinned as compared with the conventional structure. According to a useful embodiment of the present invention, the protective container comprises bottom support members in the container bottom portion. According to another useful embodiment the protective container comprises: a structure formed by said support members and having at least two layers in which a first layer of the head skirt portion is completely formed into a plate-like shape, a second layer formed adjacent to said first layer has an annular outer layer having deformation resistance weaker than that of the first layer and an inner layer fitted in a central space of the outer layer and having deformation resistance further weaker than that of the outer layer. When the protective container falls in such a manner that its head portion faces downwards, the second layer of the head support members are compressive-deformed at the time of collision with the round or the like. In particular, the inner portion of the outer layer is expanded toward the inner layer having a weaker distortion resistance. Therefore, the pressure of upwards pushing the first layer toward the tank can be dispersed in the lateral direction so that collision of the head support members with the valve is effectively prevented. As a result, impact resistance can be improved and the head support members can be thinned as compared with the conventional structure. The mutual effects of the pressure receiving member and the head support members prevent deformation of the head support members toward the tank and intrusion of the tank head skirt portion at the time of falling so that the valve is protected. Also the deformation of the tank head skirt portion can be prevented, and impact can be dispersed and absorbed. Moreover, the head support members and the bottom support members can be thinned as compared with the conventional structure. Note that the head support members may, on the outside of the second layer, have a third layer having deformation resistance weaker than that of the first layer and stronger than that of the inner layer. Since the third layer, which is not deformed at the time of performing a puncture test or the like, exists, it is further preferable. The rotation stoppers may be fastened to the tank head skirt portion or the tank bottom skirt portion and the protective container to prevent relative movement of the tank in the protective container. Since the angle, at which the tank is accommodated in the protective container, is previously set, the tank can be attached in such a manner that the valve is not exposed through an opening when the protective container is opened at the time of performing a drop test or the like. If a fire takes place, damages of portions having poor heat resistance due to direct contact of flame with the valve can be prevented. The head support members may have a recess portion at a position facing the valve. As a result, the valve can be protected further reliably at the time of falling or the like. Note that the tank is a UF 6 tank filled with UF 6 . An embodiment of the present invention will now be described with reference to the drawings attached. Brief Figure Description: Fig.1 is a vertical cross sectional view showing an embodiment of the present invention and taken along the lengthwise direction of the protective container accommodating a tank; Fig. 2 is a lateral cross sectional view showing a tank head skirt portion of the protective container shown in Fig. 1 and taken along a direction perpendicular to the direction of the axial extension of the container; Fig. 3 is a plan view showing a state where the metal rotation-stopper is attached to the tank head skirt portion of the tank; Fig. 4 is a partial cross sectional view showing a structure for connecting a lower half portion and an upper half portion of the protective container where the metal rotation-stopper shown in Fig. 3 is attached to the protective container; Fig. 5 is a partial and vertical cross sectional view showing a state of deformation of the tank head skirt portion when the protective container accommodating the tank falls in such a manner that its container head portion faces downwards; Fig. 6 is a partial and vertical cross sectional view showing a state of deformation of the head support members when the protective container accommodating the tank falls in such a manner that its head portion faces downwards; Fig. 7 is a partial cross sectional view of the protective container according to another embodiment of the present invention; and Fig. 8 is a cross sectional view showing an essential portion of the metal rotation-stopper according to the other embodiment. Detailed Figure Description Referring to Fig. 1, a UF 6 tank (hereinafter simply called a "tank") 1 is stored or transported in such a manner that the tank 1 is hermetically accommodated in a protective container 2. Moreover, the outer surface of the protective container 2 is fixed and secured by a frame (not shown). The tank 1 is formed into, for example, a capsule-like shape having a cylindrical side portion 3 which has two ends respectively formed into a tank head portion 4 and a tank bottom portion 5 each of which is formed into a substantially convex shape. A valve 6 is, near the side surface and apart from the lengthwise directional central axis 0 common to the tank 1 and the protective container 2 in the accommodated state, attached to the tank head portion 4. A tank head skirt portion 7 and a tank bottom skirt portion 8, each of which has a cylindrical shape, are connected to two extensions from the ends of the side portion 3 of the tank 1. The tank head skirt portion 7 forwards extends over the valve 6 and the tank head portion 4 to protect the valve 6 and the tank head portion 4, while the tank bottom skirt portion 8 projects and extends from a plug 9 (a sealing cap) and the tank bottom portion 5 to protect the plug 9 and the tank bottom portion 5. The diameter of the free end of each of the tank head and bottom skirt portions 7 and 8 is reduced so as to be somewhat warped inwards. The protective container 2 is formed into a cylindrical shape having a bottom, and has a container head portion provided with a disc-like head support members 11. Similarly, disc-like bottom support members 12 are provided for the bottom portion of the protective container 2. Between the two support members 11 and 12, there is disposed a cylindrical heat insulating member 13. The heat insulating member 13 is made of a material, for example, phenolic foam or the like, exhibiting excellent flexibility, and extends to the side region surrounding of the tank 1. The two ends of the heat insulating member 13 are respectively connected to the head support members 11 and the bottom support members 12. The head support members 11 and the bottom support members 12 have the same structure. The head support members 11 is formed into, for example, a triple layer structure formed by stacking, in a direction of the axial line 0 from the tank 1 toward the outside, a first layer 14, a second layer 15 and a third layer 16 each having the same outer diameter. Each layer serves as a shock absorbing member. The first layer 14 is formed into a disc-like shape and made of a material (for example, oak wood) having excellent deformation resistance. The second layer 15 consists of a ring-like outer layer 15a and a disc-like inner layer 15b to be fitted in a hollow portion of the outer layer 15a and having a smaller diameter. The outer layer 15a is made of a material (for example, balsa wood) having deformation resistance weaker than that of the first layer 14, while the inner layer 15b is made of a material, such as phenolic foam, exhibiting excellent flexibility, that is, a material having resistance weaker than that of the outer layer 15a. The third layer 16 is formed into a disc-like shape and made of a material (for example, balsa wood) similar to that of the outer layer 15a which has relatively weak deformation resistance. The bottom support members 12 have the same structure. The protective container 2 is, as shown in Fig. 2, vertically divided into two sections in the lengthwise direction thereof along a plane including the central axis O, the two sections being an upper half 2a and a lower half 2b. The halves 2a and 2b have corresponding stepped portions 18a and 18b so as to be connected to each other. When the tank 1 is mounted or removed, the upper half 2a and the lower half 2b can be separated from each other. As shown in Figs. 2 to 4, a metal rotation-stopper 20 for the tank 1 is attached to the tank head skirt portion 7. The metal rotation-stopper 20 is formed into, for example, a band-like semicircular arc shape disposed along the outer surface of the tank 1 and having flat engaging members 20a at the two lengthwise directional ends thereof. Moreover, a pin 20b is implanted in the inner surface of the metal rotation-stopper 20 so as to be received by and fixed to any of holes 21, the number of which is determined appropriately to be disposed at predetermined intervals around the circumferential direction of the tank head skirt portion 7, so that the metal rotation-stopper 20 is attached to the tank head skirt portion 7. The engaging members 20a of the metal rotation-stopper 20 are inserted into grooves 18c formed in either connection surface of the stepped portions 18a and 18b of the upper and lower halves 2a and 2b so that the tank 1 is secured in such a manner that relative rotation of the same in the protective container 2 is prevented. Referring to Fig. 1, a pressure receiving member 23 having a substantially L-shape cross section and formed into a substantially annular shape is attached to a free end 7a of the tank head skirt portion 7. The pressure receiving member 23 has a flat bottom portion 23a in the substantially L-shape cross section thereof so as to be interposed between the free end 7a of the tank head skirt portion 7 and the head support members 11. A side wall 23b stood erect substantially perpendicularly to the bottom portion 23a and formed into a cylindrical shape is disposed at an outer end of the bottom portion 23a so as to extend between the outer surface of the tank head skirt portion 7 and the heat insulating member 13. An annular projection 23c stood erect substantially perpendicularly to the bottom portion 23a is formed at an inner end of the bottom portion 23a. The projection 23c fixes the free end 7a of the tank head skirt portion 7 on the outer surface thereof. The projection 23c is required to be capable of fixing the free end 7a of the tank head skirt portion 7. For example, its height is the same as the thickness of the free end 7a of the tank head skirt portion 7, the height being considerably shorter than the height of the side wall 23b. The pressure receiving member 23 is located outer than the valve 6 so that contact of the valve 6 is prevented when the drop test or the like is performed. Since the embodiment of the present invention is structured as described above, the pin 20b is inserted into the appropriate hole 21 and the metal rotation-stopper 20 is attached prior to accommodating the tank 1 into the protective container 2 in such a manner that the valve 6 is located at an angular degree of about 90° from the pair of engaging members 20a at a position opposing the metal rotation-stopper 20 with respect to the tank head skirt portion 7 of the tank 1. Moreover, the pressure receiving member 23 is fixed to the free end 7a of the tank head skirt portion 7. Then, the engaging members 20a of the metal rotation-stopper 20 are inserted into the engaging groove 18c formed in the stepped portion 18b (or 18a) of the upper and lower halves 2a and 2b, and the tank 1 is accommodated in the lower half 2b in such a manner that the engaging stepped portions 18a and 18b are fixed to each other so that the two halves 2a and 2b are closed. Then, the outer surface of the protective container 2 is fastened and secured by a frame of the like (not shown). Thus, the tank 1 is accommodated in the protective container 2 in a state where it is fastened and secured when the tank 1 is stored or transported. According to the structure of this embodiment, if the protective container 2 accommodating the tank 1 falls vertically due to a drop test or an accident in such a manner that the container head portion of the protective container 2 faces downwards, the inertia force of the dropping protective container 2 can be absorbed because the head support members 11 are deformed when it collides with the ground or the like. At this time, the head support members 11 are compressed between the ground or the like and the tank 1, and therefore it is deformed. The inertia force of the tank 1 causes the free end 7a of the tank head skirt portion 7 to press against the head support members 11 through the pressure receiving member 23. Thus, the head support members 11 are deformed. Since the free end 7a is warped inwards in the foregoing case, it is pressed with respect to the bottom portion 23a of the pressure receiving member 23 in a direction in which it is moved inwards in the radial direction so as to be restrained by the projection 23c. Thus, a portion near the free end 7a of the tank head skirt portion 7 is warped so that it is brought into contact with the side wall 23b. As a result, warp of the portion near the free end 7a of the tank head skirt portion 7 is prevented. Moreover, the inertia force causes the outer surface of the tank head skirt portion 7 to press against the side wall 23b, causing the degree of the warp to be limited such that the tank head skirt portion 7 is not curved considerably (see Fig. 5). Since the conventional structure, which is not provided with the pressure receiving member 23, has the arrangement that the end of the free end 7a of the tank head skirt portion 7 is in direct contact with the head support members 11, the end of the free end 7a is intruded into the head support members 11 due to the inertia force. Moreover, the exerted stress causes the head support members 11 in the peripheral portion to expand toward the tank 1. Thus, there arises a risk that the head support members 11 collide with the valve 6. To prevent this, inevitably the head support members must be thickened. Since the free end 7a is warped inwards, there arises another risk that the tank head skirt portion 7 is warped considerably at the time of a collision to collide with the valve. In view of the foregoing, in the embodiment of the present invention, when the protective container 2 collides with the ground or the like, the inertia force of the tank 1 is received by the entire bottom 23a of the pressure receiving member 23. Moreover, a portion of the load is received by the projection 23c and the side wall 23b so that concentration of the load due to the inertia force of the head support members 11 to a small area is prevented. The load is widely dispersed and absorbed by the pressure receiving member 23 so that intrusion of the tank head skirt portion 7 into the head support members 11 and considerable warp of the tank head skirt portion 7 are prevented. therefore, the fear of the valve 6 being damaged can reliably be eliminated without thickening the head support members 11. When the head support members 11 collide with the ground or the like and thus it is deformed, the structure that the second layer 15 and the third layer 16 are made of materials each having the distortion resistance weaker than that of the inner first layer 14 results in easy deformation. In particular, since the inner layer 15b of the second layer 15 is made of the material having the flexibility superior to those of the outer layer 15a and the third layer 16, the inner portion of the outer layer 15a is deformed toward the inner layer 15b as shown in Fig. 6 so that it is compressed from the outer portion. Moreover, also the central portion of the third layer 16 is expanded toward the inner layer 15b. The expansions of the outer layer 15a and the central portion of the third layer 16 are dispersed and absorbed by the overall body of the inner layer 15b and the same are not concentrated in a direction in which the first layer 14 is pushed upwards toward the tank 1. Thus, the upward pushing operation of the head support member 11 is prevented significantly. Therefore, the fear that the head support members 11 collide with the valve 6 or the like and thus it is damaged can be eliminated. On the other hand, the conventional structure, in which the head support members are formed by a single layer having the same thickness as that employed in this embodiment, causes the overall body of the central portion of the head support member pressed by the tank head skirt portion 7 or the like of the tank 1 to be expanded toward the tank 1. Thus, there arises a problem in that the central portion easily collides with the valve 6. If the protective container 2 does not fall vertically but if the same falls diagonally in such a manner that its container head portion faces downwards, load generated at the time of the collision is concentrated to the end of the head support members 11 of the protective container 2. The principle of the impact deformation and absorption by the pressure receiving member 23 and the head support members 11 are the same as that in the case of the vertical falling. As described above, according to this embodiment, the pressure receiving area of the tank 1 can be enlarged due to the pressure receiving member 23 so that local deformation of the head support members 11 causing the tank head skirt portion 7 to be intruded deeply and allowed to collide with the valve 6 is reliably prevented. Moreover, the projection 23c of the pressure receiving member 23 prevents the tank head skirt portion 7 being considerably deformed. Since the head support members 11 have the triple-layer structure, excessive expansion of the overall body of the central portion of the head support members 11 toward the tank 1 resulting in collision with the valve 6 at the time of falling or collision can be prevented. Therefore, the impact resistance can be improved without the necessity of thickening the head support members 11 as required for the conventional protective container. Thus, the valve 6 can reliably be protected from being damaged at the time of falling. Since also the bottom support members 12 have the triple-layer structure, the impact resistance in the case where the protective container 2 falls in such a manner that its container bottom portion faces downwards can be improved due to the same reason. Moreover, its thickness can relatively be reduced. Therefore, the overall length of the protective container 2 along the central axis 0 thereof can be shortened as compared with the conventional protective container and its size can be reduced. As a result, manufacturing, storing, transporting and the like can be made efficient and economical. Moreover, the relative rotation and movement of the tank 1 in the protective container 2 are prevented by the metal rotation-stopper 20. Since the valve 6 is disposed apart from the engaging stepped portions 18a and 18b of the upper and lower halves 2a and 2b by an angular degree of about 90°, the valve 6 cannot be exposed through an opening formed if the upper and lower halves 2a and 2b are slipped and opened due to the impact generated at the time of falling or the like of the protective container 2. Therefore, there is substantially no possibility that flame directly comes in contact with the valve 6 through the opening if a fire takes place. As a result, elements of the valve 6 having poor heat resistance can be protected from being damaged, and the safety of the valve 6 can be improved. Note that the head support members 11 and the bottom support members 12 are not required to be formed into the triple-layer structure. A double-layer structure consisting of the first layer 14 and the second layer 15 may be employed. Another structure having four or more layers formed by adding the second layer 15 or the third layer 16 may be employed. If the double-layer structure is employed, the second layer of the head support members are compressive-deformed and the inner portion of the outer layer is expanded toward the inner layer having weak distortion resistance. Therefore, the pressure for upwardly pushing the first layer toward the tank is disposed in the lateral direction. However, the double-layer structure is not preferable because it is advantageous that a layer, which is not considerably deformed, is left in the outer layers when a puncture test (the protective container 2 dropped from a height of 1 m from a columnar testing frame having a diameter of 150 mm) is performed. If a structure having four or more layers is employed, each of the support members 11 and 12 is thickened to the thickness of the conventional support member. Therefore, advantage of the invention is unsatisfactory. Another embodiment of the present invention will now be described with reference to Fig. 7. Referring to Fig. 7, the metal rotation-stopper 20 is attached to the tank 1 as described in the foregoing embodiment so that the position of the valve 6 is fixed in a state where the tank 1 is accommodated in the protective container 2. A recess portion 25 is formed in the head support members 11 at a position in the direction of the axial line O opposing the valve 6. The recess portion 25 is formed by cutting the first layer 14. The foregoing structure is able to further eliminate the fear that the valve 6 collides with the head support members 11 at the time of a collision or the like so that the safety is further improved. The structure for engaging the metal rotation-stopper 20 to the upper and lower halves 2a and 2b is not required to be the engaging member 20a and the engaging groove 18c as employed in the foregoing embodiment. For example, a structure shown in Fig. 8 may be employed in which a pin 29 secured, by threads or the like, to a metal rotation-stopper 28 having a substantially circular arc shape is received by an engaging hole 30 formed in either of the stepped portion 18a or 18b of the upper and lower halves 2a and 2b. The engaging groove 18c and the engaging hole 30 are not required to be formed in the stepped portion 18a or 18b. They may be formed at arbitrary positions in the circumferential direction of the upper and lower halves 2a and 2b. As a matter of course, the metal rotation-stopper 20 may be provided for the tank bottom skirt portion 8. Although the foregoing embodiments have the structure such that both of the head support members 11 and the bottom support members 12 are formed into the same triple-layer structures not to specify the direction of the tank head portion 4 (having the valve 6) of the tank 1 when the tank 1 is accommodated in the protective container 2, specification of the direction, in which the tank head portion 4 is accommodated, will enable a structure, in which only either support member (the head support members 11) has two or more layers according to the present invention and the other support member (the bottom support member 12) is formed into a single layer, to be employed. Although the foregoing embodiments have the structure such that the pressure receiving member 23 is provided for the tank head skirt portion 7, it may be provided for the head support members 11. In the foregoing case, the pressure receiving member 23 is divided to be adaptable to the upper half 2a and the lower half 2b. Although the foregoing embodiments have been described about the UF 6 tank filled with UF 6 , the present invention is not limited to this. As a matter of course, the protective container according to the present invention may be used as that for any of a variety of tanks. As described above, the protective container according to the present invention has the structure such that the pressure receiving member, having a projection, to which the free end of the tank head skirt portion is fixed, is provided between the tank head skirt portion and the head support members. Therefore, impact generated when the protective container falls in such a manner that its head faces downwards and the protective container collides with the ground or the like can be transmitted to the head support members while being dispersed and absorbed by the pressure receiving member. Thus, the fears that the tank head skirt portion is cut into the head support members and that the head support members is expanded toward the tank due to the load causing the valve to collide with the head support members can be eliminated. Since the projection portion fixes the free end of the tank head skirt portion, deformation of the tank head skirt portion can be prevented. As a result, the impact resistance can be improved and the head support members can be thinned as compared with the conventional structure. The protective container according to the present invention has the head support members formed into a structure having at least two layers. The second layer consists of the annular outer layer having deformation resistance weaker than that of the first layer and the inner layer fitted in the central space of the outer layer and having deformation resistance further weaker than that of the outer layer. Therefore, when the tank protective container falls onto and collides with the ground or the like, the inner portion of the outer layer of the head support members is expanded toward the inner layer having weaker distortion resistance. Therefore, the pressure for upwards pushing the first layer can be dispersed and absorbed so that collision of the head support members with the valve is effectively prevented. As a result, the impact resistance can be improved and the head support members can be thinned as compared with the conventional structure. The protective container according to the present invention has the pressure receiving member between the tank head skirt portion and the head support members. Moreover, the head support members have the structure consisting of at least two layers. The second layer consists of the annular outer layer having weaker deformation resistance than that of the first layer and the inner layer fitted in the central space of the outer layer and having a deformation resistance further weaker than that of the outer layer. Therefore, the mutual effects of the pressure receiving member and the head support members prevent deformation of the head support members toward the tank and intrusion of the tank head skirt portion in case of falling or the like so that the valve is protected. Moreover, deformation of the tank head skirt portion can be prevented. Furthermore, the head support members and the bottom support members can be thinned to achieve the foregoing protection and prevention. Since the overall length of the protective container can be shortened and the size of the same can be reduced. Thus, manufacturing, storing and transporting can be made to be efficient. Moreover, the manufacturing cost and the transporting cost can be reduced. The head support members have the third layer on the outside of the second layer, the third layer having deformation resistance weaker than that of the first layer and stronger than that of the inner layer. Therefore, the third layer, which cannot be deformed considerably at the time of falling or the like, exists so that a preferred result is realized when the puncture test or the like is performed. Since the rotation stoppers are fastened to the tank head skirt portion or the tank bottom skirt portion and the protective container, mutual movement of the tank in the protective container can be prevented. Therefore, the angle, at which the tank is accommodated in the protective container, can be previously set. Thus, even if the protective container is opened at the time of the drop test or the like, the tank can be mounted at a position, at which the valve is not exposed through an opening. Even if a fire takes place, flame does not directly come in contact with the valve, and portions having poor heat resistance are not damaged. Since the recess portion facing the valve is formed in the head support members, the valve can be protected further reliably at the time of falling. Reference numerals: 0 lenghtwise directional central axis / axial line 1 tank 2 protective container 2a upper half of 2 2b lower half of 2 3 - 4 tank head portion 5 tank bottom portion 6 valve 7 tank head skirt portion 7a free end of 7 8 tank bottom skirt portion 9 plug 10 - 11 head support members (disc-like -) 12 bottom support members 13 heat insulating member 14 first layer of 11/12 15 second layer of 11/12 15a outer layer (ring-like -) 15b inner layer (disc-like -) 16 third layer of 11/12 17 - 18 - 18a stepped portion 18b stepped portion 18c grooves 19 - 20 metal rotation-stopper 20a flat engaging members 20b pin 21 holes 22 - 23 pressure receiving member 23a flat bottom portion of 23 23b side wall stood of 23 23c projection (annular -) of 23 24 - 25 recess portion 26 - 27 - 28 metal rotation-stopper 29 pin 30 engaging hole

Claims: A protective container (2) for accommodating and protecting a tank (1), said tank (1) comprising: a valve (6) in a tank head portion (4) and a substantially cylindrical tank head skirt portion (7) adjacent to the tank head portion (4); said tank protective container (2) comprising: a container head portion and an opposing container bottom portion with a space therebetween for accommodating the tank (1); head support members (11) in the container head portion; and a pressure receiving member (23) disposed between said tank head skirt portion (7) and said head support members (11) and having a projection (23c) arranged to be capable of restraining a free end (7a) of said tank head skirt portion (7) upon deformation of the tank head skirt portion (7). A protective container (2) according to claim 1, further comprising bottom support members (12) in the container bottom portion. A protective container (2) according to claim 1 or 2, further comprising: a structure formed by said support members (11, 12) and having at least two layers (14, 15) in which a second layer (15) formed adjacent to a first layer (14) has an annular outer layer (15a) having deformation resistance weaker than that of said first layer (14) and an inner layer (15b) fitted in a central space of said outer layer (15a) and having deformation resistance further weaker than that of said outer layer (15a). A protective container (2) according to claim 3, wherein a third layer (16) having deformation resistance weaker than that of said first layer (14) and stronger than that of said inner layer (15b) is, on the outside of said second layer (15), provided for said support members (11, 12). A protective container (2) according to anyone of claims 1 to 4, further comprising a rotation stopper (20, 28, 29) being fixable to said tank head skirt portion (7) or a tank bottom skirt portion (8) and said protective container (2) so that relative movement of said tank (1) in said protective container (2) can be prevented. A protective container (2) according to claim 5, wherein said head support members (11) have a recess portion (25) at a position facing said valve (6).

Inventors: NAKAMURA KAZUHITO, OSAKO AKIHIKO, TANAKA SHOICHI, TEZUKA YOUICHI, WAKAKI MAKOTO, NAKAMURA, KAZUHITO, OSAKO, AKIHIKO, TANAKA, SHOICHI, TEZUKA, YOUICHI, WAKAKI, MAKOTO, Nakamura, Kazuhito, c/o Nuclear Energy Center, Osako, Akihiko, c/o Nuclear Energy Center, Tanaka, Shoichi, c/o Nuclear Energy Center, Tezuka, Youichi, c/o Nuclear Energy Center, Wakaki, Makoto, c/o Nuclear Energy Center
Applicants: MITSUBISHI MATERIALS CORP, MITSUBISHI MATERIALS CORPORATION
Application year: 1996
Main classification: G21F5
IPC codes: G21F5, B65D88