JPH10268081A - Transportation method for boiling water reactor fuel assembly - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transportation method for BWR fuel assembly not loosing integrity due to instantaneous work of large vibration and acceleration during transportation by increasing the restricting force of upper and lower tieplates in horizontal and axial directions on a BWR(boiling water reactor) fuel assembly contained in an inner vessel and the like. SOLUTION: In a transportation method for a BWR fuel assembly 1 in which a transportation separator is inserted and the assembly is contained in an inner vessel of a fuel protection vessel or a transportation vessel, the cross section shape of the inner vessel and the like 12 is made square shape, one side of the cross section of the assembly 1 and the inner vessel 12 is made inclined by about 45 degrees when the transportation vessel is laid horizontally and the assembly 1 is tightened to the inner vessel 12 from the above by using the tightening force of the lid 11 of the inner vessel 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the transport of a boiling water reactor fuel assembly, and more particularly to a method of securing a fuel assembly to an inner container containing the fuel assembly and a transport method using the same.

[0002]

2. Description of the Related Art Conventional boiling water reactors (Boiling Water Reactors)
Reactor (hereinafter, abbreviated as BWR) FIG. 10 (a) and FIG.
This will be described with reference to FIG. The fuel assembly 1 is assembled by a number of fuel rod groups and an upper tie plate 2, and a lower tie plate 3 and a fuel spacer 4.

At the time of transportation of the fuel assembly 1, between the fuel spacers 4 and between the fuel spacers 4 from the viewpoint of preventing vibration during transportation.
And several sets of transportation separators 5 are inserted between the upper tie plate 2 and the fuel spacer 4 and the lower tie plate 3,
It is placed in an inner container 9 or the like comprising a container body 7 with a protective body 6 lined therein and a lid 8, and further transported in a transport container (not shown).

After the fuel body 1 is stored in the container body 7 of the inner container 9 and the like, it is pressed by the transport separator 5 by the fastening force of the closed lid 8. Are transported in a state where a gap exists between the surfaces of the transport separator 5 and the protective body 6 on both sides.

[0005]

The method of inserting the transport separator 5 into the BWR fuel body 1 and transporting it involves a general method of transport during which the acceleration is not so large. This is extremely effective in preventing the vibration of the fuel body 1. However, in the prior art, there were the following issues regarding securing of the fuel body 1.

The first problem is that the horizontal restraining force is insufficient. As shown in FIG. 10, the vertical direction of the fuel assembly 1 is fastened by the inner bottom surface and the lid surface. On the other hand, in the horizontal direction, a gap exists between both side surfaces of the fuel body 1 and the inner surface of the inner container 9 or the surface of the protective body,
The resistance to the relative movement between the fuel body 1 and the inner container is only the frictional force due to the weight of the fuel body and the tightening force of the lid 8.

Among these, the fastening force of the lid 8 is large because the fastening portion is the transport separator 5 inserted between the fuel rods, so that the compression rigidity is small and the fuel rod is deformed according to the fastening force. Tightening force cannot be applied. Therefore, the fuel assembly 1 has a structure in which the fuel body 1 is liable to generate a vibration accompanied by a slip inside the inner container 9 in response to a horizontal vibration having a relatively small horizontal restraining force and a relatively large acceleration.

A second problem is that the axial restraining force is insufficient. For example, in transporting a MOX (mixed oxide) fuel body that generates heat, the fuel body
Difference between the fuel body 1 and the inner container 9 due to the difference in extension between the inner body 9 and the inner container 9 or the like, or a gap is inevitably formed between the top or bottom of the fuel body 1 and the inner container 1 or the like. Occurs.

Therefore, in the prior art, the axial restraining force is insufficient for the same reason as the lifting in the horizontal direction, and the same problem occurs with respect to the axial vibration with relatively large acceleration.

A third problem is that the binding force of the tie plate portion is insufficient. At the upper and lower ends of the fuel body 1, there are an upper tie plate 2 and a lower tie plate 3 made of metal having a relatively large mass. Due to these, especially under the horizontal vibration condition, the fuel body 1 exhibits a significantly different vibration characteristic from the central portion of the fuel body 1 with a slip between the upper tie plate 2 and the protection body 6 or between the lower tie plate 3 and the protection body 6. It was hot.

The above three problems are not particularly problematic when the acceleration of the vibration during transportation is small. However, when the acceleration is relatively large, the fuel body 1 slips inside the inner container 9 or the like. Due to the peculiar vibration, the inconvenience of accelerating the wear of the metal contact portion of the fuel rod group has been caused.

The fourth problem arises from the fact that the transport separator 5 supports the weight of the fuel rod group. In a crane operation or the like that accompanies loading and unloading of the transport container storing the fuel body 1 in the fuel transport process, an instantaneous force having a relatively large acceleration different from normal vibration may be generated. As a matter of course, it is necessary to maintain the integrity of the fuel body 1 against such an instantaneous force.

By the way, when the own weight of the fuel rod group is supported by the transport separator 5 as in the prior art, the lowermost row of the many fuel rods supports the most weight of the fuel rod group. Become.

Therefore, when an instantaneous force of a relatively large acceleration is applied, the lowermost fuel rods may be plastically deformed, so that the working conditions during transportation must be severely restricted. There were challenges. In particular, in future fuel assemblies, the diameter of fuel rods tends to be smaller, so this problem tends to be more severe in future fuel assemblies.

It is an object of the present invention to enhance the horizontal restraining force and the axial restraining force of the BWR fuel body stored and transported in an inner container and the like, and the restraining force of the upper and lower tie plates. A method for securing a BWR fuel body to an inner container, etc., which can stably transport the fuel body without causing a specific vibration accompanied by slipping inside the inner container, etc. against a higher level of vibration during transportation and this To provide a transportation method using a fuel cell, and furthermore, does not impair the soundness of the fuel body even when an instantaneous force of a relatively large acceleration acts.
An object of the present invention is to provide a securing method for transporting a BWR fuel body and a transport method using the same.

[0016]

According to a first aspect of the present invention, there is provided a method of transporting a BWR fuel assembly, the method comprising:
Inserting the transport separator into the BWR fuel body and the inner container of the fuel protection container or transport container (referred to as inner container, etc.)
In the transportation method in which the container is transported in a transport container, the cross-sectional shape of the inner container or the like is rectangular, and when the transport container is horizontal, one side of the cross section of the fuel body and the inner container is inclined at about 45 degrees from the horizontal. And fastening the fuel assembly from above to secure the fuel assembly to an inner container or the like.

The lower part of the fuel body is in contact with the inner container and the like on two sides, and is tightened by the fastening force of the lid and the like. Stable transportation is possible even with acceleration vibration.

According to a second aspect of the present invention, there is provided a method of transporting a BWR fuel assembly, comprising a clamping plate and a moving mechanism capable of detecting a tightening torque or a tightening displacement on two sides of a lid of an inner container in the method of the first embodiment. In addition to a fastening mechanism, the method includes a step of fastening the fuel body from above by the fastening mechanism to secure the fuel body to an inner container or the like.

By tightening with a tightening mechanism capable of detecting the tightening torque and the tightening displacement, the fuel body inside the inner container or the like is fixed at the position of the tightening mechanism by an arbitrary large lateral restraining force, so that a large acceleration Stable transportation is possible even with vibrations.

According to a third aspect of the present invention, there is provided a transportation method for transporting a BWR fuel body according to the first aspect of the present invention, wherein at least two portions of an upper tie plate portion and a lower tie plate portion are tightened by a tightening mechanism. The method includes a step of securing the body to an inner container or the like.

The fuel body inside the inner container or the like is tightened at at least two places, that is, the upper tie plate portion and the lower tie plate portion having a large mass by a fastening mechanism capable of detecting a fastening torque and a fastening displacement. There is no peculiar vibration that tends to occur in the upper and lower tie plates, and stable transportation can be performed even with a large acceleration vibration.

According to a fourth aspect of the present invention, there is provided a method for transporting a BWR fuel assembly, wherein at least one of the fastening plates for fastening the lower tie plate does not contact a finger spring provided on the lower tie plate. A step having a stepped plate-like dimension and a step of arranging the stepped plate-shaped clamping plate on the step of the lower tie plate to restrain the axial displacement of the fuel body by the lower tie plate. I do.

The axial displacement of the fuel body inside the inner container or the like is restrained by the restraining force in the axial direction by the stepped plate-shaped tightening plate of the lower tie plate portion. Stable transportation is possible.

According to a fifth aspect of the present invention, there is provided a method of transporting a BWR fuel assembly, wherein the transport separator is inserted into the BWR fuel assembly, stored in an inner container, and transported in a transport container. Inserting the transport separator into the fuel body, with the outer wall of the transport separator within the range from the outer dimension of the fuel spacer to a value obtained by adding 1.2 mm to this outer dimension, with the inner wall or the protective body attached to the inner wall being planar. A step of bringing both the fuel spacer and the transport separator into contact with the inner wall of the inner container or the surface of a protective body attached to the inner wall to secure the fuel body to the inner container or the like.

Since the fuel body inside the inner container or the like has both the fuel spacer and the transport separator in contact with the inner wall of the inner container or the protective body, it has good soundness even with a relatively large momentary acceleration force. I can keep it.

According to a sixth aspect of the present invention, there is provided a method of transporting a BWR fuel body, wherein a transport separator is inserted into the BWR fuel body, and is stored in a fuel protection container or an inner container of the transport container and transported by the transport container. In the case where the outer dimension of the transportation separator is much larger than the outer dimension of the fuel spacer by more than 1.2 mm, the inner wall of the inner container or the protective body (referred to as the inner wall or the like) attached to the inner wall is positioned at the fuel spacer. Install the intermediate member and set the thickness of the intermediate member within the range from the sum of the fuel spacer outer dimension and the thickness of the intermediate member to the sum of the sum of the fuel spacer outer dimension and the thickness of the intermediate member plus 1.2 mm. And a step of bringing both the fuel spacer and the transport separator into contact with an inner wall or the like or an intermediate member to secure the fuel body to the inner container or the like.

When the outer dimension of the transport separator is larger than the outer dimension of the fuel spacer, an intermediate member is provided in the fuel spacer portion, thereby bringing both the fuel spacer and the transport separator into contact with the inner wall of the inner container. The integrity of the fuel body can be maintained even with a relatively large acceleration force.

According to a seventh aspect of the present invention, there is provided a method of transporting a BWR fuel assembly according to the fifth or sixth aspect, wherein the fastening plate, the fastening torque and the fastening displacement can be detected on the lid surface and one side surface of the inner container or the like. A step of tightening the fuel spacer portion, the upper tie plate portion, and the lower tie plate portion of the fuel body with the tightening mechanism to secure the fuel body to the inner container or the like. It is characterized by.

For the fuel body inside the inner container, etc.,
By tightening the fuel spacer part and the upper and lower tie plate parts by the tightening mechanism, the lateral restraint force and the restraint force of the upper and lower tie plate parts with large mass are ensured, and stable transportation is possible even with large acceleration vibration. it can.

In the method of transporting a BWR fuel body according to the invention of claim 8, when the transport container is made horizontal in the method of claim 7, one side of the cross section of the fuel body and the inner container is inclined at about 45 degrees from the horizontal. It is characterized in that it is transported in a state where it is kept.
When the transport container is leveled, one side of the cross section of the fuel body and inner container is inclined about 45 degrees from the horizontal, so the lateral restraining force and the restraining force of the upper and lower tie plate parts with large mass are further increased. As a result, stable transportation can be performed even with large acceleration vibration.

According to a ninth aspect of the present invention, there is provided a method of transporting a BWR fuel assembly according to the second, third, and seventh aspects, wherein a compression member such as a leaf spring is provided between the fastening plate of the fastening mechanism and the fuel assembly. The method includes a step of fastening the fuel body via a member to secure the fuel body to the inner container or the like.

Since the fuel body inside the inner container or the like is tightened by the tightening mechanism via the compression member, the lateral restraining force and the restraining force of the upper and lower tie plate parts having a large mass are reliably ensured. Thus, stable transportation can be performed even with relatively large acceleration vibration, and resonance with the vibration of the transportation can be avoided by adjusting the natural frequency of the fuel body.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to the drawings. Note that the same components as those of the above-described conventional technology are denoted by the same reference numerals, and detailed description is omitted. The first embodiment relates to claim 1 and relates to FIG.
As shown in (1), in the BWR fuel assembly 1, several sets of transport separators 5 are inserted between the fuel spacers 4 and between the fuel spacers 4 and the upper and lower tie plates 2 and 3.

As shown in FIG. 1 (b), the fuel body 1 is housed in an inner container or the like 12 composed of a container body 10 and a lid 11 whose one side in the cross section is inclined at about 45 degrees from horizontal. Here, as an example, plastic,
The figure shows a case where a protective body 6 such as rubber or honeycomb is provided.

After the fuel body 1 is stored in the container body 10, it is tightened from above through the protective body 6 by the tightening force f of the lid 11 of the inner container 12 or the like. The fastening points are the transport separator 5, the upper tie plate 2 and the lower tie plate 3.
Position. In general, a very large force cannot be expected as the fastening force f by the lid 11, but in the present invention, the square fuel body 1 is mounted on the protection body 6 on the bottom side of the V-shaped container body 10. V-shaped lid 11 placed from above
Therefore, the horizontal restraining force can be remarkably enhanced as compared with the related art.

As shown in FIG. 2, the second embodiment relates to a second embodiment, in which the square fuel body 1 is housed in an inner container 12 composed of a container body 10 and a lid 11. A tightening mechanism 15 including a tightening plate 13 and a moving mechanism 14 capable of detecting a tightening torque and a tightening displacement is installed on the two surfaces 11, and the fuel body 1 is tightened from above by the tightening mechanism 15.

As described above, in general, a very large force cannot be expected as the tightening force f by the lid 11, but according to the present invention, an arbitrary tightening force is obtained by the tightening mechanism 15 according to the tightening position of the fuel body 1. , It is possible to secure a more reliable binding force. In addition, the tightening force management (torque management) during transportation becomes possible, and the fuel body 1 can be transported more safely.

The third embodiment relates to claim 3, and as shown in FIG. 3, the locations where the fuel body 1 is tightened by the tightening mechanism 15 are the location of the upper tie plate 2 and the location of the lower tie plate 3.
The transport separator 5 is fastened by the fastening force of the lid 13.

In general, the location of the transport separator 5 has a low compression rigidity, so that relatively uniform tightening can be realized by the tightening force of the lid 13, whereas the upper tie plate 2 and the lower tie plate 3 have a low compression rigidity. Very large because the lid
Uniform tightening cannot be expected with a tightening force of 13. However, according to the present invention, the portions of the upper and lower type plates 2 and 3 exhibiting unique vibration characteristics because of their large mass can be tightened with an appropriate tightening force, so that the above-described unusual vibration can be prevented.

In the fourth embodiment, as shown in FIG. 4, at least one of the fastening plates 16 of the lower tie plate 3 in the fuel assembly 1 is already provided in the lower tie plate 3, as shown in FIG. A stepped plate having a size not to contact the finger spring 17 is disposed on the step 3a of the lower tie plate 3, and the axial displacement of the fuel body 1 is restrained by the lower tie plate.

According to the present invention, slippage of the fuel body 1 due to axial vibration during transportation, or displacement due to thermal expansion difference between the fuel body 1 and the inner container at the time of MOX fuel transportation is restrained by the lower tie plate portion. be able to.

The fifth embodiment relates to claim 5, and as shown in FIG. 5, the fuel body 1 has an outer dimension ranging from the outer dimension value of the fuel spacer to a value obtained by adding 1.2 mm to the outer dimension value. The transport separator 5 within the range is inserted, and the inner wall or the protective body 6 attached to the inner wall is housed in a flat inner container 12 or the like. In the stored fuel assembly 1, both the fuel spacer 4 and the transport separator 5 are fixed to the inner container 12 while being in contact with the protective body 6, and are transported in a transport container (not shown). .

The present embodiment has been made for the above-mentioned fourth problem, and is intended to support the high strength fuel spacer 4 when a relatively large momentary force is generated. In this case, the transport separator 5 having a transport separator outer dimension slightly larger than the fuel spacer outer dimension is used. Since the transport separator 5 is inserted between the fuel rod groups between the fuel spacers 4, the transport separator 5 has low compression rigidity and is easily deformed by compression.

Therefore, as in the present invention, even if the outer dimension 18 of the transportation separator is larger than the outer dimension 19 of the fuel spacer by about 1.2 mm, the weight of the fuel 1
The transport separator 5 can be deformed without causing any damage to the fuel spacer 4, and the fuel spacer 4 can be brought into contact with the protective body 6.

As a result, a load due to a momentary large acceleration that may occur during a crane operation or the like is supported by the fuel spacer 4, so that the fourth problem of plastic deformation of the lowermost fuel rod is prevented. can do. Note that the transport separator outer dimension value 18 is greater than the fuel spacer outer dimension value 19.
When it is larger than 1.2 mm, when the transport separator 5 is compressed and deformed to bring the fuel spacer 4 into contact with the protective body 6, the fuel body 1 may be damaged by plastic deformation.

In the sixth embodiment, as shown in FIG. 6, as shown in FIG. 6, the outer dimension 18 of the transport separator is much larger than 1.2 mm as compared with the outer dimension 19 of the fuel spacer. This is a corresponding example.

In the above state, the intermediate member 20 is installed at the position of the fuel spacer 4 on the inner wall of the inner container 12 to adjust the gap. That is, the transport separator outer dimension 18 is within the range from the sum of the fuel spacer outer dimension 19 and the plate thickness of the intermediate member 20 to a value obtained by adding 1.2 mm to the sum. The thickness of the intermediate member 20 is selected.

According to the present invention, similarly to the fifth embodiment, the load is supported by the fuel spacer 4 against an instantaneous large acceleration force. Plastic deformation of the fuel rod can be prevented.

The seventh embodiment is based on claim 7 and relates to FIG.
As shown in (a) and (b), the fuel body 1 has a transport separator 5 which is equal to or slightly larger than the outer dimension of the fuel spacer 4.
Is inserted, and the fuel body 1 is stored in the inner wall or the inner container 12 in which the protective body 6 attached to the inner wall is flat.

In the stored fuel body 1, both the fuel spacer 4 and the transport separator 5 are in contact with the protector 6, and further, the fuel 11 is held by the lid 11 of the inner container 12 and one side of the container body 10. At the position of the spacer 4, a fastening mechanism 15 including a fastening plate 13 and a moving mechanism 14 is installed, whereby the fuel body 1 is fixed to the inner container 12 at the fuel spacer 4.

A transport separator 5 which is equal to or slightly larger than the outer dimension of the fuel spacer is inserted into the fuel body 1, and the fuel body 1 is housed in an inner container 12 or the like having a flat inner wall or a protective body 6 attached to the inner wall. Then, both the fuel spacer 4 and the transport separator 5 are in contact with the protective body 6.

Further, the lid 11 of the inner container 12 and the container body 10
In one aspect, the fuel assembly 1 is secured to the inner container 12 at the fuel spacer 4 by the fastening mechanism 12. Therefore, according to the present invention, it is possible to prevent the plastic deformation of the lowermost fuel rod with respect to the momentary large acceleration force, and to secure the horizontal and vertical restraining forces against the vibration during transportation. Secure and safer transportation.

The eighth embodiment relates to claim 8 and relates to FIG.
As shown in FIGS. 8A and 8B, the internal state of the inner container 12 is the same as that of FIG. However, as in the first embodiment, when a transport container (not shown) that houses the inner container 12 and the like is horizontal, one side of the cross section of the fuel body 1 and the inner container 12 and the like is inclined by about 45 degrees from the horizontal. ing.

Therefore, together with the seventh embodiment, the first
By providing the same operation and effect as the embodiment,
Since a larger binding force can be secured with a small tightening force, safer transportation can be performed.

The ninth embodiment is directed to a ninth embodiment. As shown in FIG. 9, a tightening plate of a tightening mechanism 15 provided on the lid 11 is provided.
13, a compression member 21 such as a leaf spring
Is installed. As a result, the fuel spacer 4 is fastened by the fastening mechanism 15 via the compression member 21.

In general, the natural frequency of the fuel assembly 1 differs between the unloading of the fuel rod group supported by the transport separator 5 and the support of the fuel rod group by the fuel spacer due to the difference in the rigidity of the supporting portion. Since the rigidity of the fuel spacer 4 is considerably greater than the rigidity of the transport separator 5, the fifth to eighth embodiments have the rigidity of the fuel spacer 4 as shown in FIGS. 5 to 8, respectively. When the fuel rod group is supported, there is a concern that the natural frequency will increase and resonate with the vibration of a transportation such as a locomotive.

However, in the present invention, the fuel rod group is supported via the compression member 21 such as a leaf spring, so that the natural frequency of the fuel body 1 can be set to a low value. Resonance with vibration can be avoided.

[0058]

As described above, according to the present invention, the horizontal restraining force and the axial restraining force, and the restraining force of the upper and lower tie plates are enhanced by the securing method of the BWR fuel body stored in the inner container or the like. In addition, with respect to vibration at a higher acceleration level during transportation, stable transportation can be performed without generating a unique vibration accompanied by slipping of the fuel body inside the inner container or the like. Further, even when an instantaneous force of a relatively large acceleration is applied during transportation, the fuel body is not damaged, and resonance with vibration in the transportation can be avoided. Ensuring soundness and improving transportation work efficiency.

[Brief description of the drawings]

1A and 1B are views showing an inner container and the like according to a method for transporting a fuel body according to a first embodiment of the present invention, wherein FIG. 1A is a partially cutaway side view, and FIG. Arrow sectional drawing which followed the -B line.

FIG. 2 is a sectional view of an inner container and the like according to a method for transporting a fuel body according to a second embodiment of the present invention.

FIG. 3 is a partially cutaway side view of an inner container and the like according to a method of transporting a fuel body according to a third embodiment of the present invention.

FIG. 4 is a partially cutaway side view of a main part of an inner container and the like according to a fuel body transporting method according to a fourth embodiment of the present invention.

FIG. 5 is a partially cut-away side view of a main part of an inner container and the like according to a fuel body transporting method according to a fifth embodiment of the present invention.

FIG. 6 is a partially cutaway side view of a main part of an inner container and the like according to a fuel body transportation method according to a sixth embodiment of the present invention.

7A and 7B are views showing an inner container and the like according to a fuel body transporting method according to a seventh embodiment of the present invention, wherein FIG. 7A is a partially cutaway side view, and FIG. Arrow sectional drawing which followed the -C line.

8A and 8B are views showing an inner container and the like according to a fuel body transportation method according to an eighth embodiment of the present invention, wherein FIG. 8A is a partially cutaway side view, and FIG. Arrow sectional drawing along the -D line.

FIG. 9 is a sectional view of an inner container and the like according to a ninth embodiment of a fuel body transportation method according to the present invention.

10A and 10B are views showing an inner container and the like according to a conventional method for transporting a fuel body, wherein FIG. 10A is a partially cutaway side view, and FIG.
FIG. 2 is a cross-sectional view taken along line AA in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... BWR fuel body, 2 ... Upper tie plate, 3 ... Lower tie plate, 3a ... Lower tie plate step part, 4 ... Fuel spacer, 5 ... Transport separator, 6 ... Protective body, 7,10
… Container body, 8,11… Lid, 9,12… Inner container, 13,16…
Clamping plate, 14… Transfer mechanism, 15… Clamping mechanism, 17… Finger spring, 18… Transport separator outer dimension value, 19
... fuel spacer outer dimensions, 20 ... intermediate member, 21 ... compression member,
f: Clamping force by lid.

Claims (9)

[Claims] 1. A transportation method in which a transportation separator is inserted into a boiling water reactor fuel body, is housed in an inner container or the like, and is transported by a transportation container. When made horizontal, one side of the cross section of the fuel body and the inner container is inclined about 45 degrees from the horizontal,
A method for transporting a boiling water reactor fuel assembly, comprising a step of fastening the fuel assembly to an inner container or the like by tightening the fuel assembly from above. 2. A fuel body is tightened from above by a tightening mechanism including a tightening plate and a moving mechanism capable of detecting at least one of a tightening torque and a tightening displacement on two lid-side surfaces of the inner container or the like, and the fuel body is tightened from above. 2. The method for transporting a boiling water reactor fuel assembly according to claim 1, further comprising a step of securing the fuel assembly. 3. The method according to claim 1, further comprising the step of fastening at least two places of an upper tie plate portion and a lower tie plate portion by the fastening mechanism to secure the fuel body to an inner container or the like. A method for transporting boiling water reactor fuel assemblies. 4. At least one of the tightening plates for tightening the lower tie plate has a stepped shape having a size that does not contact a finger spring provided on the lower tie plate, and the stepped plate-shaped tightening plate is formed of the lower type. 2. The method for transporting a boiling water reactor fuel assembly according to claim 1, further comprising the step of arranging the fuel assembly in a step portion of the rate plate to restrain axial displacement of the fuel assembly by a lower tie plate portion. 5. A transportation method in which a transport separator is inserted into a boiling water reactor fuel body and is stored in an inner container or the like and transported by a transport container, wherein the inner wall of the inner container or the protector attached to the inner wall is provided. A transport separator having a planar shape in which the outer dimension of the transport separator is in a range from the outer dimension of the fuel spacer to a value obtained by adding 1.2 mm to the outer dimension is inserted into the fuel body, and the separator of the fuel spacer and the transport separator is inserted. A method for transporting a boiling water reactor fuel body, comprising a step of contacting both with an inner wall of the inner vessel or the like or a surface of a protective body attached to the inner wall to secure the fuel body to the inner vessel or the like. 6. A transportation method in which a transportation separator is inserted into a boiling water reactor fuel body and is stored in an inner container or the like and transported by a transportation container, wherein the transportation separator outer dimension is 1.2 times smaller than the fuel spacer outer dimension. When the intermediate member is installed at the position of the fuel spacer such as the inner wall of the inner container, and the thickness of the intermediate member is set to the outer dimension of the fuel separator and the outer dimension of the intermediate member. And the fuel spacer and the transportation separator are brought into contact with the inner wall or the like or the intermediate member. A method for transporting a boiling water reactor fuel assembly, comprising the step of securing the fuel assembly to an inner container or the like. 7. A tightening mechanism comprising a tightening plate and a moving mechanism capable of detecting a tightening torque and a tightening displacement is provided on a lid surface and one side surface of the inner container or the like, and the fuel spacer portion of the fuel body is provided by the tightening mechanism. 7. The method for transporting a boiling water reactor fuel assembly according to claim 5, further comprising the step of fastening the fuel assembly to an inner container by tightening the upper tie plate portion and the lower tie plate portion. . 8. The boiling water reactor according to claim 7, wherein when the transport container is made horizontal, the fuel body and the inner container are transported in a state where one side of the cross section is inclined at about 45 degrees from the horizontal. How to transport fuel. 9. A method comprising the steps of: providing a compression member such as a leaf spring between a tightening plate of the tightening mechanism and a fuel body, and tightening the fuel body via the compression member to secure it to the inner container or the like. The method for transporting a boiling water reactor fuel body according to claim 2 or claim 3 or claim 7.