JP5062686B2 - Canister and concrete cask - Google Patents

Description

  The present invention relates to a canister which is a metal container for hermetically storing spent fuel used in a nuclear power plant, and a concrete cask in which the canister is covered with a concrete container.

  The spent fuel used at the nuclear power plant is subjected to reprocessing for recovering reusable substances such as plutonium and uranium. For example, in Japan, the amount of spent fuel generated at nuclear power plants is about 1200 tons per year, whereas the amount of reprocessing is about 800 tons per year, and the amount generated exceeds the amount of reprocessing. For this reason, the spent fuel which remains without being reprocessed is stored for a certain period in a predetermined place outside the nuclear power plant site, for example. And this amount of storage is expected to increase in the future.

  As a storage method, there are a wet method in which cooling is performed with water and a dry method in which cooling is performed with air. As one of the dry methods, metal cask storage and the like have been put into practical use. Although the dry method has a lower operating cost than the wet method, the cost of storing the metal cask is extremely high, and it is not possible to expect a significant cost reduction due to the need to consider safety when transported.

  Moreover, concrete cask storage is proposed as one of the dry methods (for example, refer patent document 1). Although concrete cask storage can greatly reduce costs, the corrosion resistance of canisters used for concrete cask storage, such as soundness against stress corrosion cracking, cannot be confirmed. is the current situation.

  In order to eliminate such problems as stress corrosion cracking of the canister, at least the inner peripheral surface of the cylindrical portion constituting the canister is covered with a corrosion resistant layer made of stainless steel having excellent corrosion resistance such as super stainless steel and SUS304. (For example, refer to Patent Document 2).

JP 2001-141883 A JP 2003-255086 A

  Thus, by providing the corrosion resistant layer made of stainless steel, the corrosion resistance of the canister can be improved. However, since canisters (concrete cask) containing spent fuel are often installed on coastal areas exposed to sea breeze, even canisters with a corrosion-resistant layer made of stainless steel will cause stress corrosion cracking. It can be considered. That is, even a canister provided with a corrosion-resistant layer made of stainless steel cannot be said to be able to sufficiently maintain the sealing function of the radioactive substance. For this reason, further improvement in the corrosion resistance of the canister is desired.

  The present invention has been made in view of such circumstances, and provides a canister and a concrete cask capable of securely storing spent fuel for a long period of time and reducing costs. For the purpose.

A first aspect of the present invention that solves the above problems comprises a cylindrical main body portion made of a metal material and containing spent fuel therein, and an outer surface of the main body portion made of titanium or a titanium alloy. The corrosion-resistant coating layer includes a bottom plate, an upper plate, and a side plate, and each of the bottom plate, the upper plate, and the side plate is fixed to the main body by welding, and the side plate is Each of the covering plates is welded to the main body portion between its end portions and an adjacent covering plate, and A plurality of through holes are formed in the cover plate, and the cover plate is welded to the surface of the main body at each through hole .

  In the first aspect, the corrosion resistance of the canister is greatly improved, and the sealing function of the radioactive substance can be sufficiently maintained over a long period of time. That is, the stress corrosion cracking of the canister is reliably prevented by the corrosion resistant coating layer.

  According to a second aspect of the present invention, there is provided the canister according to the first aspect, wherein the main body is formed of stainless steel.

  In the second aspect, since the main body is formed of a material having relatively excellent corrosion resistance, the radioactive substance can be more securely sealed and stored.

According to a third aspect of the present invention, there is provided a canister according to the first or second aspect, characterized in that a welded portion between the respective covering plates is covered with a band-shaped cover member .
A fourth aspect of the present invention is the canister according to any one of the first to third aspects, wherein the through hole is covered with a cover member .
According to a fifth aspect of the present invention, there is provided a concrete container having a canister according to any one of the first to fourth aspects, a cooling passage through which the canister is housed and a cooling air for cooling the canister passes. And a concrete cask characterized by comprising:

In the fifth aspect, the spent fuel can be securely stored for a long period of time. That is, the occurrence of stress corrosion cracking in the canister can be reliably prevented, and the radioactive substance can be hermetically stored for a long period of time.

  Corrosion resistance of the canister is greatly improved. That is, soundness against stress corrosion cracking can be ensured. Therefore, the concrete cask using this canister can maintain the sealing function of the radioactive material for a long period of time, equivalent to or more than the metal cask, and greatly compared to the metal cast. Cost can be reduced.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
1 is a cross-sectional view showing a schematic configuration of a concrete cask according to Embodiment 1, FIG. 2 is a schematic perspective view of a canister according to Embodiment 1, and FIG. 3 is a cross-sectional view showing a part of the canister. It is. 4 to 7 are views for explaining a method of forming the corrosion-resistant coating layer, and are cross-sectional views showing a part of the canister.

  As shown in FIG. 1, a concrete cask 10 according to this embodiment includes a canister 30 that is a metal container in which a basket holding spent fuel is enclosed, and a concrete container 50 that holds the canister 30 inside. Has been. And this concrete cask 10 is installed in the building 70 provided in predetermined places, such as the shore vicinity, for example.

  The concrete container 50 is made of concrete and includes a cylindrical container body 51 whose bottom is closed and a lid body 52 that closes the upper opening of the container body 51. That is, in the concrete container 50, the container main body 51 and the lid body 52 form a storage portion 53 in which the canister 30 is stored. The canister 30 is placed in the housing portion 53 so as to be coaxial with the concrete container 50.

  Although not shown, a liner made of metal such as carbon steel is provided on the inner surface of the concrete container 50, that is, the inner surfaces of the container main body 51 and the lid body 52 constituting the housing portion 53. This liner serves to shield radiation (gamma rays) from spent fuel, which is a radioactive material.

  Further, in a state where the canister 30 is accommodated in the accommodating portion 53, a certain amount of gap is formed between the canister 30 and the concrete container 50. At the lower end of the concrete container 50, a plurality of inlets 54 are formed through which the cooling air is introduced through the gap in the housing 53 and the outside. On the other hand, a plurality of discharge ports 55 are formed at the upper end portion of the concrete container 50 so as to communicate with the gaps in the housing portion 53 and discharge cooling air. For example, in this embodiment, four inlets 54 and outlets 55 are formed at the lower end and the upper end of the concrete container 50, respectively. Then, cooling air flows into the accommodating portion 53 from each of the introduction ports 54, the concrete cask 10 is cooled by natural convection cooling of the cooling air, and the cooling air whose temperature has risen is discharged to the outside from the discharge ports 55. It has become so.

  As shown in FIGS. 1 to 3, the canister 30 accommodated in such a concrete container 50 is made of a metal material such as stainless steel (SUS304) and has a cylindrical body with both ends closed. 31 and a corrosion-resistant coating layer 32 provided on the outer surface of the main body 31, and a basket 100 holding spent fuel, which is a radioactive substance, is enclosed in the main body 31. The size of the canister 30 is not particularly limited. For example, the canister 30 is formed with a diameter of about 1.6 m and a height of about 4.5 m.

  The main body 31 includes a container main body 33, and a primary lid 34 and a secondary lid 35 that close the container main body 33. The main body 31 has a welded and sealed structure so that the spent spent fuel does not leak to the outside. That is, the container main body 33 has a cylindrical shape with a closed bottom surface, and the upper opening of the container main body 33 is double-closed by the primary lid 34 and the secondary lid 35. Further, the primary lid 34 and the secondary lid 35 are arranged with a gap between them, and the respective peripheral portions are welded to the container main body 33 over the entire circumference, and the inside of the canister 30 is sealed. Sexuality is enhanced. In addition, an inert gas having a higher thermal conductivity than air, for example, helium (He) gas, is sealed in the container body 33 and in the gap between the primary lid 34 and the secondary lid 35. Although omitted in FIG. 1, a plurality of suspension tools 36 used when lifting the canister 30 with a crane or the like are provided on the surface of the secondary lid 35 (see FIG. 2).

  Further, a corrosion-resistant coating layer 32 made of a titanium-based material, that is, titanium or a titanium alloy is directly lined on the outer surface of the main body 31, in this embodiment, the surface of the container main body 33 and the secondary lid 35 (sealing attachment). The main body 31 is completely covered with the corrosion-resistant coating layer 32 (see FIG. 3).

  As shown in FIG. 2, the corrosion-resistant coating layer 32 includes, for example, a bottom plate 37 that covers the bottom surface of the main body 31, an upper plate 38 that covers the upper surface (secondary lid 35), and a side surface ( And a side plate 39 that covers the circumferential surface. In the present embodiment, the side plate 39 is constituted by a plurality of cover plates 40. Each covering plate 40 is provided continuously over the circumferential direction of the main body 31, and each covering plate 40 is welded to the surface of the main body 31. The welded portion between the cover plates 40 is completely covered with a band-shaped cover member 41 welded onto the cover plate 40.

  Here, each covering plate 40 constituting the side plate 39 is welded to the main body 31 as follows. First, as shown in FIG. 4, the longitudinal welded portion (for example, portion A in FIG. 2), that is, the welded portion between the end portions of the same cover plate 40 is a state in which the end portions of the cover plate 40 are partially overlapped. Then, both are welded by so-called seam welding. On the other hand, as shown in FIG. 5 (a), first, as shown in FIG. 5 (a), the welded portion in the lateral direction (for example, portion B in FIG. 2), that is, the welded portion between the adjacently disposed cover plates 40, The end portion is directly welded to the surface of the main body portion 31 by so-called seam welding, and then a belt-like cover member 41 is disposed so as to cover the welded portion 80 between the respective cover plates 40 as shown in FIG. The cover member 41 is welded onto the cover plate 40.

  Further, in the present embodiment, a plurality of through holes 42 are formed in each cover plate 40, and each cover plate 40 is welded to the surface of the main body 31 also in these through holes 42. As shown in FIG. 6, these through holes 42 are completely covered by a circular cover member 43 welded onto the cover plate 40, similarly to the joint portion between the cover plates 40 described above. .

  Moreover, although the formation method of such a corrosion-resistant coating layer 32 is not specifically limited, In this embodiment, the corrosion-resistant coating layer 32 is previously formed in each of the container main body 33 and the secondary lid 35 at a factory etc. (Welding) Before the spent fuel is accommodated in the container body 33 and the container body 33 and the secondary lid 35 are welded, a welded portion between the container body 33 and the secondary lid 35 (C in FIG. 2). The corrosion-resistant coating layer 32 is formed (welded) only on the portion) so that the entire body 31 is completely covered with the corrosion-resistant coating layer 32.

  Specifically, after welding the container main body 33 and the secondary lid 35 in which the corrosion-resistant coating layer 32 is formed in advance, as shown in FIG. A strip-shaped spacer member 45 made of a titanium-based material is disposed so as to cover the welded portion 81, and then, as shown in FIG. 7B, the spacer member 45 and the welded portion 82 on both outer sides of the spacer member 45 are covered. The cover member 41 is welded onto the cover plate 40. In addition, although the material of the welding wire used for such welding is not specifically limited, For example, it is preferable to use a Cu-1Mn-3Si alloy. Moreover, what is necessary is just to determine joining (welding) conditions suitably, but it is preferable that a joining speed shall be 30-40 cm / min and an electric current shall be about 60-80A.

  Thus, the corrosion-resistant coating layer 32 according to the present embodiment is configured by the above-described bottom plate 37, top plate 38, side plate 39, cover members 41 and 43, and spacer member 45, and the outer surface of the main body 31 of the canister 30 is The corrosion-resistant coating layer 32 is completely covered.

  In this embodiment, a pure titanium plate is used as the material for the corrosion-resistant coating layer 32, and the bottom plate 37 has a thickness of about 4 mm in order to ensure the strength. The one having a thickness of about 1 mm is used.

  As described above, in the concrete cask 10 according to the present invention, the canister 30 is constituted by the main body portion 31 and the corrosion-resistant coating layer 32 made of a titanium-based material provided so as to cover the main body portion 31. Thereby, the sealing performance of the canister 30 improves. In particular, the occurrence of stress corrosion cracking of the canister 30 can be reliably prevented over a long period (50 years or more). Further, by providing the corrosion-resistant coating layer 32, the thickness of the main body 31 can be reduced, the weight of the canister can be reduced, and the material cost can be reduced.

  From these things, if it is the concrete cask 10 which concerns on this invention, spent fuel can be safely stored over a long period of time, and the storage cost of spent fuel can be reduced significantly. Become.

  As described above, since the canister 30 has a double container structure, the slow heat performance is slightly lowered, but the main body 31 and the corrosion-resistant coating layer 32 are both made of metal and heat transfer deterioration is small. The influence on the slow heating performance of the canister 30 is considered to be small.

  In the present embodiment, the side plate 39 of the corrosion-resistant coating layer 32 has been described as being composed of a plurality of coating plates 40. Of course, the side plate 39 may be formed of a single plate material. Furthermore, the canister 30 according to the present embodiment has a corrosion-resistant coating layer 32 made of a titanium material formed on the surface of a main body 31 made of a metal material such as stainless steel. For example, the surface of stainless steel is made of a titanium plate. It may be formed by rolling a so-called clad material coated in advance. In this case, as the clad material, for example, a stainless steel surface having a thickness of about 20 mm and a pure titanium plate having a thickness of about 1 mm adhered to each other by an explosion method or a rolling method is used. Even in a canister formed of such a clad material, of course, as with the canister of this embodiment in which the main body is covered with a cover plate, the sealing performance is improved and the occurrence of stress corrosion cracking on the canister is prolonged. It can be reliably prevented over a period of time.

  Here, for example, a welded portion between the main body 31 and the cover plate 40 constituting the corrosion-resistant coating layer 32, that is, a welded portion between the stainless steel plate and the titanium plate, and a welded portion between the cover plates 40, that is, a weld between the titanium plates. The results of various tests on the bondability of the parts are described.

(Test Example 1)
First, titanium lining welding is performed using MG960 (Cu-1Mn-Si alloy), which is a welding wire of the example, and MG910 (Cu-10Ni), which is a welding wire of a comparative example. The presence or absence of weld bead cracking was evaluated.

  Specifically, as shown in FIG. 8, the test piece 100 includes a stainless steel plate 110 and a titanium plate 120, and as shown in FIG. 9, the test piece 100 is held on the titanium plate 120 and held by the holding plate 200. The stainless steel plate 110 and the titanium plate 120 were welded together with the welding material 130. In this test, the stainless steel plate 110 and the titanium plate 120 were welded by running a carriage (not shown) on which the torch 210 was fixed and the test piece 100 was placed. At that time, the test was performed by changing the target position, that is, the distance d between the torch 210 and the end of the titanium plate 120. The test conditions (welding speed, current and target position) and the results (number of cracks) are shown in Table 1 below. The “number of cracks” is the result of the penetrant test of the number of cracks per 230 mm weld length.

  As the stainless steel plate, a plate material of stainless steel (SUS304) of thickness (t1) 9 mm × width (w1) 80 mm × length (l1) 300 mm is used, and as the titanium plate, thickness (t2) 1 mm × width (W2) A plate of pure titanium (JIS H 4600, 2 types) having a size of 50 mm × length (l2) 300 mm was used.

  As shown in Table 1, when the target position is d = 0 mm (a corner portion of the titanium material), the titanium melts excessively, so that both the welding wire of the example and the welding wire of the comparative example generate cracks. It tended to be easy. Also, when the welding current was high, cracks were likely to occur for the same reason. However, in the welding wire of the example, there was a tendency that cracking hardly occurred when the target position was not 0 mm.

  On the other hand, the welding wire of the comparative example was easily cracked even when the target position d was other than 0 mm. FIG. 10 is a photograph showing an example of a crack generated in a bead welded using a welding wire of a comparative example. As shown in FIG. 10, the crack was a transverse crack that cracked in the direction perpendicular to the weld line and occurred immediately after welding. It is considered that cracks are caused by the formation of a brittle intermediate compound of titanium and copper and the shrinkage stress in the weld line direction.

  As described above, the welding wire of the example tended to be less susceptible to cracking than the welding wire of the comparative example. That is, with the welding wire of the embodiment, the covering plate 40 constituting the corrosion-resistant covering layer 32 can be favorably welded to the main body 31 without causing cracks.

(Test Example 2)
Next, the tensile shear strength test of the welded part was performed. Specifically, a stainless steel plate made of stainless steel (SUS304) of thickness (t1) 9 mm × width (w1) 80 mm × length (l1) 300 mm, and thickness (t2) 1 mm × width (w2) 50 mm × length (12) A titanium plate made of 300 mm pure titanium (JIS H 4600 2 types) is prepared. As shown in FIG. To do. That is, the stainless steel plate 110 and the titanium plate 120 are welded using the welding wire (MG960 (Cu-1Mn-3Si)) of the example. Then, as shown in FIG. 12, a test piece 100 having a length of 25 mm is taken from the three joint portions of the stainless steel plate 110 and the titanium plate 120, and the tensile shear of the welded portion is obtained using this test piece 100. A strength test was performed. The welding speed was 40 cm / min, the target position was 2 mm from the corner of the titanium plate, and argon gas was used as the shielding gas. The applied voltage at this time was 12V, and the welding current was 65A.

  FIG. 13 is a photograph showing the appearance of each of the three test pieces after the test. As is clear from FIG. 13, the fractured portion was not a welded portion but a titanium plate (base material), and it was confirmed that there was no problem in weldability. The measured tensile shear strength evaluation results are shown in Table 2 below. Each test piece after the test is confirmed to have sufficient tensile shear strength because the titanium plate is in a squeezed state and the tensile stress is equivalent to the pure titanium JIS type 2 used for breaking stress. It was done. In other words, by using the welding wire of the embodiment to weld the coating plate 40 constituting the corrosion resistant coating layer 32 of the canister 30 to the main body portion 31, the corrosion resistant coating layer 32 is favorably formed on the surface of the main body portion 31. Can do.

(Test Example 3)
Next, a peel strength test was performed. Specifically, a stainless steel plate made of stainless steel (SUS304) having a thickness (t1) 9 mm × width (w1) 80 mm × length (l1) 300 mm welded with a plate material having a predetermined dimension on one surface side, and a thickness ( t2) 1 mm × width (w2) 50 mm × length (l2) 300 mm of pure titanium (JIS H 4600 2 types) and a titanium plate prepared as shown in FIG. The titanium plate 120 is welded to the surface opposite to the welded plate material 111 by the welding material 130 so as to face the plate material 111. That is, the titanium plate 120 is welded to the surface of the stainless steel plate 110 using the welding wire (MG960 (Cu-1Mn-3Si)) of the example. And the test piece 100 whose length is 25 mm was extract | collected from three places of the joint parts of the seam welding of these stainless steel plates 110 and the titanium plate 120. FIG. The welding speed was 40 cm / min, the target position was 2 mm from the corner of the titanium plate, and argon gas was used as the shielding gas. The applied voltage at this time was 12V, and the welding current was 65A.

  And the board | plate material 111 and the titanium plate 120 of this test piece 100 were pulled in the reverse direction, and the peeling strength test was done.

  FIG. 15 is a photograph showing the appearance of each of the three test pieces after the test. As apparent from FIG. 15, the fractured portion was the interface between stainless steel and copper alloy.

  The results of the peel test are shown in Table 3 below. The peel strength was significantly smaller than the shear strength. However, for example, since the peel strength of the welded portion between aluminum alloys is about 30 to 40% of the tensile shear strength, the peel strength of the test piece is considered to be sufficient even when it is used in a canister. It is done.

(Test Example 4)
Next, a shear strength test according to JIS G 0610 was performed. Specifically, first, a stainless steel plate made of stainless steel (SUS304) of thickness (t1) 9 mm × width (w1) 80 mm × length (l1) 300 mm is prepared, and the welding wire (MG960 (Cu-1Mn) of the example is prepared. -3Si)), a weld bead (SCU) 140 is formed on the stainless steel plate 110 as shown in FIG. And as shown in FIG. 17, the 1st test piece 100A whose length is 25 mm is extract | collected from two places of the weld bead 140 part on this stainless steel plate 110. As shown in FIG.

  Further, a stainless steel plate having the above dimensions provided with a step portion having a depth of 1 mm and pure titanium (JIS H 4600, two types) having a thickness (t2) of 1 mm × width (w2) of 50 mm × length (l2) of 300 mm 18), and a titanium plate 120 is disposed on the step portion of the stainless steel plate 110, and one end of the titanium plate 120 is welded onto the stainless steel plate 110 with a welding material 130, as shown in FIG. That is, welding is performed on a clad material (titanium clad steel) composed of the stainless steel plate 110 and the titanium plate 120 using the welding wire (MG960 (Cu-1Mn-3Si)) of the embodiment, and a weld bead (STI) 140. Form. As shown in FIG. 19, a second test piece 100B having a length of 25 mm is collected from the four joint portions of the stainless steel plate 110 and the titanium plate 120. The welding speed was 40 cm / min, the target position was 2 mm from the corner of the titanium plate, and argon gas was used as the shielding gas. The applied voltage at this time was 12V, and the welding current was 65A.

  Then, the first and second test pieces 100A and 100B were evaluated by performing a compression test using a test jig. FIG. 20 is a diagram showing an outline of the test jig 250. As shown in FIG. 20, the test jig 250 is composed of two support plates 252 and 253 and a compression punch 254 fixed on a base 251 at a predetermined interval, and a test piece is provided between the support plates 252 and 253. By inserting 100 (100B) and pressing the test piece 100 with the compression punch 254, the shear force is concentrated on the bead 140 portion.

  FIG. 21 is a photograph showing the appearance of the first test piece 100A after the test, and FIG. 22 is a photograph showing the appearance of the second test piece 100B after the test. As is clear from these drawings, the first test piece 100A is peeled off from the interface between the copper alloy bead and the stainless steel plate. Moreover, in the 2nd test piece 100B, it has peeled from the interface of a copper alloy bead, a titanium plate, and a stainless steel plate.

The results of the shear strength test are shown in Table 4 below. As can be seen from this result, the shear stress of the second test piece was equivalent to the shear stress of the first test piece, and both were 200 N / mm ² or more. And since the shear stress of the 2nd test piece is over 140 N / mm < ² > which is a standard of the shear strength of titanium clad steel, the 2nd test piece has sufficient intensity | strength. That is, even when a clad material made of a stainless steel plate and a titanium plate is employed for the canister 30 according to the present invention and the stainless steel and the titanium plate are welded, sufficient strength can be obtained.

(Test Example 5)
Next, the corrosion resistance test of the welded part was performed. First, a stainless steel plate made of stainless steel (SUS304) of thickness (t1) 10 mm × width (w1) 80 mm × length (l1) 300 mm, and thickness (t2) 1 mm × width (w2) 50 mm × length (l2) A titanium plate made of 300 mm pure titanium (JIS H 4600 two types) is prepared, and as shown in FIG. 23, the welding wire (MG960 (MG960) (both ends of the titanium plate 120 becomes the welding material 130 on the stainless steel plate 110). Lining welding using Cu-1Mn-3Si)). And the 1st test piece whose length is 25 mm was extract | collected from three places of the welding joint part of these stainless steel plates 110 and the titanium plate 120. FIG.

  Further, as shown in FIG. 24, the two titanium plates 120A and 120B are welded to each other by using the welding wire (MG960 (Cu-1Mn-3Si)) of the embodiment which becomes the welding material 130. A test piece was prepared. Specifically, the end of one titanium plate 120A was TIG welded onto the other titanium plate 120B, and second test pieces having a length of 25 mm were collected from three joint portions of the weld. Further, the end of one titanium plate 120A was MIG welded on the other titanium plate, and third test pieces having a length of 25 mm were collected from three joint portions of the weld.

  And the corrosion resistance test of the welding part was done about these 1st-3rd test pieces. As the corrosion resistance test, a salt spray test (5 wt% sodium chloride aqueous solution spray test) was performed in accordance with JIS Z 2371. Specifically, the environmental temperature was 50 ° C., and the test time was 32 days (768 h). The internal dimensions of the test tank are 900 mm × depth 600 mm × height 500 mm.

  FIG. 25 is a photograph showing the corrosion state before and after the test of the first test piece, FIG. 26 is a photograph showing the corrosion state before and after the test of the second test piece, and FIG. 27 is the third test. It is a photograph which shows the corrosion aspect before and behind the test of a piece.

  As shown in FIG. 25, the appearance of the first test piece after the test was clearly changed, and overall corrosion was observed near the weld bead. This is considered to be corrosion caused by copper contained in the welding rod. However, a concrete cask canister is not a problem because it does not come into direct contact with the atmosphere as long as sealing is ensured.

  Further, as shown in FIG. 26, the overall corrosion and pitting corrosion were not observed in the second test piece after the test. Further, as shown in FIG. 27, the third test piece after the test showed pitting corrosion partially although corrosion was relatively small. In FIG. 27, a portion surrounded by a circle is a portion where pitting corrosion was observed. From this result, it is considered that TIG welding is appropriate as a welding method between titanium plates.

  As can be seen from these results, the canister 30 according to the present invention has extremely high corrosion resistance, and as described above, the occurrence of stress corrosion cracking can be reliably prevented over a long period of time. .

(Embodiment 2)
FIG. 28 is a schematic view of a canister according to Embodiment 2, and FIG. 29 is a cross-sectional view showing a part of the canister. The canister 30A according to the present embodiment has a configuration that is assumed to be placed horizontally, for example, at the time of transportation. For example, as shown in FIG. Same as 1. Specifically, a plurality (two in this embodiment) of collar portions 46 are provided on the outer peripheral surface of the container main body 33A of the canister 30A in the circumferential direction. In the present embodiment, these collar portions 46 are formed of stainless steel, which is the same material as the container body 33A, and are directly welded to the container body 33A. As shown in FIG. 29, the surfaces of the container main body 33A and the collar portion 46 are covered with a corrosion-resistant coating layer 32A.

  Even in such a configuration, of course, the sealing performance of the canister 30A is greatly improved. Specifically, soundness against stress corrosion cracking is greatly improved. Therefore, the spent fuel can be safely stored by the concrete cask 10 for a long period of time, and the storage cost of the spent fuel can be greatly reduced.

(Other embodiments)
As mentioned above, although embodiment of this invention was described, of course, this invention is not limited to these embodiment.

  For example, in the above-described embodiment, each cover plate 40 is provided with a through hole 42, and the cover plate 40 is welded to the main body 31 also in this through hole 42. The hole 42 may not be provided. The welding in the through hole 42 is performed for the purpose of preventing the displacement of the covering plate 40, and the through hole 42 may be provided only when there is a need to prevent the displacement of the covering plate 40.

  Further, as shown in FIG. 30, ring-shaped support legs 47 that support the canister 30 may be provided on the bottom surface of the canister 30, that is, on the bottom plate 37 of the corrosion-resistant coating layer 32. Thereby, in a state where the canister 30 is placed in the concrete container 50, the cooling air flows into the gap between the bottom surface of the canister 30 and the concrete container 50, and the concrete cask 10 is cooled more reliably. Note that the shape of the support leg 47 is not particularly limited, and is not necessarily a ring shape. The material of the support legs 47 is preferably made of a titanium-based material, but is not limited to the titanium-based material. However, it is preferable that a corrosion-resistant coating layer made of a titanium-based material is formed on the surface of the support leg 47.

  Moreover, although the above-mentioned embodiment demonstrated the example which joined the corrosion-resistant coating layer 32 to the main-body part 31 by welding, of course, the corrosion-resistant coating layer 32 is joined to the main-body part 31 by methods other than welding, for example, explosion etc. You may do it.

It is sectional drawing which shows schematic structure of the concrete cask which concerns on Embodiment 1. FIG. 1 is a schematic perspective view of a canister according to Embodiment 1. FIG. 2 is a cross-sectional view showing a part of the canister according to Embodiment 1. FIG. 2 is a cross-sectional view showing a part of the canister according to Embodiment 1. FIG. 2 is a cross-sectional view showing a part of the canister according to Embodiment 1. FIG. 2 is a cross-sectional view showing a part of the canister according to Embodiment 1. FIG. 2 is a cross-sectional view showing a part of the canister according to Embodiment 1. FIG. 2 is a schematic view showing a test piece according to Test Example 1. FIG. 5 is a schematic view showing a method for producing a test piece according to Test Example 1. FIG. 2 is a photograph showing a test piece of a comparative example after the test of Test Example 1. FIG. 6 is a schematic view showing a process for producing a test piece according to Test Example 2. FIG. 6 is a schematic perspective view showing a test piece according to Test Example 2. FIG. 6 is a photograph showing a test piece after the test of Test Example 2. 10 is a schematic view showing a test piece according to Test Example 3. FIG. 6 is a photograph showing a test piece after the test of Test Example 3. 10 is a schematic diagram illustrating a process for producing a first test piece according to Test Example 4. FIG. 6 is a schematic diagram showing a first test piece according to Test Example 4. FIG. 10 is a schematic diagram showing a process for producing a second test piece according to Test Example 4. FIG. It is the schematic which shows the 2nd test piece which concerns on the test example 4. FIG. It is a figure which shows schematic structure of the test apparatus used in Test Example 4. 6 is a photograph showing a first test piece after the test of Test Example 4. FIG. 10 is a photograph showing a second test piece after the test of Test Example 4. 10 is a schematic diagram illustrating a manufacturing process of a first test piece according to Test Example 5. FIG. 10 is a schematic diagram illustrating a process of manufacturing second and third test pieces according to Test Example 5. FIG. 6 is a photograph showing a first test piece before and after a test of Test Example 5. FIG. 6 is a photograph showing a second test piece before and after the test of Test Example 5. FIG. 6 is a photograph showing a third test piece before and after the test of Test Example 5. FIG. 6 is a schematic perspective view of a canister according to Embodiment 2. FIG. 6 is a cross-sectional view showing a part of a canister according to Embodiment 2. FIG. It is sectional drawing which shows the bottom face part of the canister which concerns on other embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Concrete cask 30 Canister 31 Main body part 32 Corrosion-resistant coating layer 33 Container main body 34 Primary lid 35 Secondary lid 36 Lifting tool 37 Bottom plate 38 Top plate 39 Side plate 40 Cover plate 41, 43 Cover member 42 Through-hole 45 Spacer member 46 Color part 47 Support leg 50 Concrete container 51 Container body 52 Lid 53 Storage part 54 Introduction port 55 Discharge port 70 Building

Claims (5)

It comprises a cylindrical main body made of a metal material and containing spent fuel inside, and the outer surface of the main body is covered with a corrosion-resistant coating layer made of titanium or a titanium alloy ,
The corrosion-resistant coating layer includes a bottom plate, a top plate, and a side plate, and each of these bottom plate, top plate, and side plate is fixed to the main body by welding,
The side plate is composed of a plurality of cover plates provided continuously over the circumferential direction of the main body, and each cover plate is welded to the main body between its end portions and an adjacent cover plate. ,
A plurality of through holes are formed in the covering plate, and the covering plate is welded to the surface of the main body portion in each through hole .   The canister according to claim 1, wherein the main body is made of stainless steel. The canister according to claim 1 or 2 , wherein a welded portion between the cover plates is covered with a belt-like cover member. The canister according to any one of claims 1 to 3 , wherein the through hole is covered with a cover member. A canister according to any one of claims 1 to 4 , and a concrete container having a cooling passage in which the canister is housed and a cooling air for cooling the canister passes. Characteristic concrete cask.