JP3154950B2 - Method of transporting fuel body for boiling water reactor - Google Patents

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 fuel assembly used in a boiling water reactor, and more particularly to a boiling water reactor having an improved method of supporting a nuclear fuel assembly transported in a horizontal state inside an inner container or the like. The present invention relates to a method for transporting a furnace fuel assembly.

[0002]

2. Description of the Related Art Boiling Water Reactor
r, hereinafter abbreviated as BWR) in transporting the fuel body, the BWR fuel body is inserted into the fuel protection container or the inner container of the transport container after the transport separator is interposed in some places, and these are transported to the transport container. The container is stored, and the transport container is placed in a horizontal state by a transportation means, and transported from the nuclear fuel facility to a nuclear power plant or another nuclear fuel facility.

FIG. 7 shows a state of a BWR fuel body and an inner container during transportation in a conventional BWR fuel body transportation method. The BWR fuel body 1 has a large number of fuel rods 3, an upper tie plate 4 and a lower tie plate 4. It is composed of a tie plate 5 and fuel spacers 6 arranged at substantially equal intervals in an intermediate portion, and is assembled in a state of a fuel bundle.

[0004] In the BWR fuel assembly 1, usually 7
The fuel spacers 6-1 to 6-7 are used. The fuel spacers 6-1 to 6-7, the fuel spacer 6-1 and the lower tie plate 5, the fuel spacer 6-7 and the upper type are used. The space between the tie plate 4 and the rate 4 is called a span, and is referred to as a first span and a second span in order from the lower tie plate 5 side. Since the total length of the fuel rod 3 is approximately 4 m, the length per span is about 500 mm.

Since the fuel rod 3 has a long overall length and is liable to vibrate during transportation, the transportation of the BWR fuel assembly 1 is particularly prevented from being damaged by the vibration during transportation. To this end, a plurality of transport separators 8 in each of which the transport separator elements 7 are combined are inserted into each of the spans, and then transported in an inner container 9 or the like. In addition,
FIG. 8A is a cross-sectional view of the transport separator element 7 taken along the line AA in FIG.
As shown in FIG. 8B and FIG. 8C, the wave-shaped leaf spring 10 and the outer frame 11 are formed in a comb shape.

The transport separator element 7 is shown in FIG.
As shown in (a), there are two types of fuel rods 3 in the BWR fuel assembly 1 in which two fuel rods 3 are vertically inserted from above and below, and a combination in which two fuel rods 3 are inserted horizontally from right and left. However, this transport separator element 7
For the purpose of preventing both the horizontal and vertical vibrations of a large number of fuel rods 3, in principle, a combination of two fuel rods in the vertical and horizontal directions is configured as a set of transport separators 8, and the BWR fuel Used for body 1.

Here, since the outer dimensions of the transport separator element 7 are larger than the outer dimensions of the fuel spacer 6, the transport separator element 7 is in the inner container in the horizontal state during transportation shown in FIG. Thus, the weight of many fuel rods 3 is supported in contact with the inner wall of the fuel cell 9.

Further, as shown in FIG. 8 (a), since all the fuel rods 3 are in contact with the corrugated leaf spring 10 inside the comb-shaped transport separator element 7, the transport separator Due to the presence of the element 7, vibration during transportation of each fuel rod 3 can be prevented.

Therefore, in the conventional method of transporting the BWR fuel assembly 1, as shown in FIG. 7, for the purpose of suppressing vibration during transportation of the fuel spacer 6, the upper tie plate 4 and the lower tie plate 5, one span is required. The number of the transport separators 8 to be inserted per hit is two, and these are arranged at positions as close as possible to the fuel spacer 6, the upper tie plate 4, and the lower tie plate 5. That is,
In the future, many transport separators as shown in FIG.
In the state of being inserted close to the material spacer or tie plate
Transported material.

[0010]

The method of transporting the BWR fuel body 1 by inserting a large number of transport separators 8 into the inner container 9 and transporting the BWR fuel body 1 in order to prevent micro-vibration during transport is described. It is extremely effective in the point of. However, the dominant frequency of the vibration of the transportation and the natural frequency of the inner container of the transport container are 30-50 Hz for the engine of the transport ship and 30-50 Hz for the freight car, respectively.
30-40 Hz, the inner container of the transport container is 50-80 Hz.

On the other hand, the natural frequency of the BWR fuel body 1 in the conventional transportation method is close to the dominant frequency of vibration in various transportation means. Therefore, if the vibration of the freight car and the BWR fuel body 1 resonate during transportation by the freight car or the like, and the BWR fuel body 1 vibrates violently, wear is accelerated at the metal contact portion of the fuel rod 3 with the fuel spacer 6 or the like. There was a problem to be done.

Regarding the transportation of the BWR fuel assembly 1,
Impact resistance that can withstand a certain impact force is required, and one of the conditions is that the fuel rod 3 is not damaged even if the BWR fuel body 1 falls from a certain height in a vertical state. . Here, when the BWR fuel body 1 is dropped vertically,
Due to the impact force applied to the lower tie plate 5 colliding with the floor, the lower tie plate 5 is deformed, and in particular, the first span of the fuel dedication 3, that is, the lower tie plate 5 and the first fuel spacer 6-1. The part in between vibrates or deforms.

Therefore, the deformation of the lower tie plate 5 and the vibration and deformation of the fuel cell 3 in the first span absorb the impact energy received by the BWR fuel body 1 due to the falling collision. However, if many transport separators 8 are interposed in the first span that absorbs impact energy,
Since the vibration and deformation of the fuel member 3 generated at the time of the falling collision are restrained, there is a problem that the impact resistance performance is reduced and the fuel member 3 is damaged.

In particular, when the fuel body 1 is a mixed-oxide (hereinafter abbreviated as MOX) fuel body having an exothermic property, the heat generated causes the inner container 9 and the fuel body 1 to be heated. due to thermal expansion differences, there is a possibility of contact with the fuel spacer 6 and transport separator 8, where the influence of the fuel rod 3 is concerned.

An object of the present invention is to reduce the number of transport separators and to select an interposition position so as to reduce the natural frequency of the BWR fuel body during transportation, and to reduce the vibration of the transportation mechanism during transportation. and to provide a method for transporting BWR fuel body sealed explosion damage the fuel rods to prevent resonance with.

[0016]

According to a first aspect of the present invention, there is provided a method for transporting a fuel assembly for a BWR, wherein the fuel assembly for a BWR is provided between fuel spacers and between a fuel spacer and an upper tie plate and a lower portion. in the transport process of BWR fuel body transporting shipping containers in the horizontal state with by inserting the shipping separator between tie accommodated in the fuel protective container or transport vessel inner container stored in the shipping container, for the transport Separators are two transport separator elements
Children with each other vertically and horizontally
The fuel spacers are configured as one set
Between the fuel spacer and the upper tie near the upper tie plate
Between the plates, with the fuel spacer close to the lower tie plate
One set of transport separators between each lower tie plate
The fuel spacers and between and above each fuel spacer.
Fuel spacer and upper tie plate near the tie plate
The transport separator inserted between the fuel
At least 70mm away from the upper or upper tie plate
It is characterized in that it is transported in an arranged state.

When transporting a BWR fuel assembly, only one set of transport separators is inserted in each span of the fuel assembly .
In addition, the insertion position of the transport separator inserted in each span
But 70mm or more from each fuel spacer and upper tie plate
is seperated. As a result, the insertion position of the transport separator
To the center of each span.
By lowering the natural frequency of the BWR fuel body in the transportation state, resonance with the vibration in the transportation can be avoided. Sa
In addition, the natural frequency of the fuel
Reduce to below 30Hz, which is smaller than Seki's dominant frequency range
This prevents vibration of the transportation and resonance of the fuel body.
be able to.

[0018]

[0019]

[0020]

[0021]

[0022]

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to the drawings. The same components as those of the above-described conventional technology are denoted by the same reference numerals, and detailed description thereof will be omitted. As shown in FIG. 1, the BWR fuel assembly 1 is transported between the fuel spacers 6 and between the fuel spacers 6 and the upper tie plate 4, and between the fuel spacers 6 and the lower tie plate 5, as shown in FIG. After being inserted into the inner container 9 or the like with the separator 8 interposed therebetween, the container is transported from a nuclear fuel facility or the like to a nuclear power plant or another nuclear fuel facility in a transport container (not shown) in a horizontal state.

The transport separator 8 is composed of a combination of two vertical transport separator elements 7 and two horizontal transport separator elements 7. It is configured to be inserted almost at the center of the span.

Next, the operation of the above configuration will be described. In the BWR fuel assembly 1 inserted in the inner container 9 with the transport separator 8 interposed between the fuel rods 3 in the BWR fuel assembly 1 to prevent vibration and damage, the most important factor affecting the natural frequency Is considered as follows. A large number of fuels 3 etc. are very rigid upper tie plate 4
The lower tie plate 5, and the relatively rigid fuel spacers 6-1 to 6-7 are assembled so that the distance between the fuel rods 3 is kept constant.

When the transportation separator 8 is interposed in such a BWR fuel assembly 1 to support the weight of the BWR fuel assembly 1 laid horizontally for transportation, the BWR fuel assembly 1 has a large number of fuel rods 3. Most of the weight of the lowermost fuel rods 3 will be supported. Therefore, B supported in this state
It can be said that the most important factor affecting the natural frequency of the WR fuel body 1 is the bending rigidity of the lowermost fuel rod 3.

FIG. 2 shows a calculation model for the bending stiffness of the lowermost row fuel 3 of the BWR fuel assembly 1 in the above situation. Here, L ₁ is the fuel spacer pitch defined in FIG. 2, is approximately 500mm as described above. Also, W
Is the weight of the fuel body between the fuel spacers, E is the Young's modulus of the fuel rod, and I is the total value of the moment of inertia of the lowermost row.

FIG. 2A shows the present invention in which one set of transport separators 8 is inserted per span according to the present invention, and the transport separator 8 is inserted at a distance x from the fuel spacer 6. And supports the fuel body's own weight W. Also,
FIG. 2B shows a conventional case in which two sets of the transport separators 8 are inserted per span, and the transport separator 8 is inserted at a position separated by a distance x from the fuel spacer 6. And supports W / 2, which is half of the weight of the fuel body.

With the calculation model shown in FIG. 2, the bending displacement of the lowermost fuel rod 3 can be calculated, whereby the spring constant K of the self-weight supporting point can be calculated. Therefore, BWR
The natural frequency f of the vibration mode caused by the supporting method in the fuel body 1 can be calculated by the following equation (1). Here, G represents gravitational acceleration.

[0030]

(Equation 1)

FIG. 3 shows the calculation result of the natural frequency f according to the above equation (1). FIG. 3A shows the case where one set of the transport separators 8 is inserted per span of the present invention. 3
(B) shows a conventional case where two sets of the transport separators 8 are inserted per span.

FIG. 3A, which is the analysis result of the present invention, shows that
When the distance x is 135 mm or more, the natural frequency f of the above equation (1) becomes a value smaller than the lower limit of 30 Hz of the dominant frequency of the transportation means. Further, when the distance x = L1 / 2, that is, as shown in FIG.
Is inserted at the center of the span, the natural frequency f is about
It becomes the minimum value of 20 Hz.

On the other hand, regarding the conventional transportation method,
The following can be said from FIG. 3B, which is the analysis result. Even when two sets of transport separators 8 are inserted per span, if the distance x is 160 mm or more, the natural frequency f becomes 30 Hz or less. However, the width of the transport separator element 7 is about 50 mm, and in this case, the distance x is smaller than that of FIG.
As shown in (b), there is a limit that can approach the center of the span.

This limit is indicated by (A) in FIG. 3 (b). However, even in this limit, the natural frequency f is reduced only to about 25 Hz. In order to more reliably prevent resonance with the vibration of the transportation, it is desirable to keep the natural frequency as far as possible from the dominant frequency region of the transportation.

Accordingly, the conventional transport method is not only inferior in vibration characteristics as compared with the present invention, but also requires two sets of transport separators 8 to be interposed in the vicinity of the center of the span, which is twice as large. It is expensive and wasteful because the number of separators is required. However, according to the first embodiment, the characteristic of the fuel body
By lowering the frequency and forming one set of the transport separators 8 inserted per span, it is possible to prevent the resonance with the vibration of the transportation means, and to provide an economically superior B.
A method of transporting a WR fuel assembly can be provided.

The BWR fuel assembly 1 is formed between the seven fuel spacers 6-1 to 6-7 and the upper tie plate 4, as shown in FIG. Be done 7
In one span, the transport separators 8 inserted into the large number of fuel rods 3 are formed as one set by combining two transport separator elements 7 in the vertical and horizontal directions.

Further, the interposed position of the transport separator 8 in the BWR fuel assembly _{1 is} separated from the fuel spacers 6-1 to 6-7 or the upper tie plate 4 by a distance l ₁ or more, and the distance l _{1 is set} to 70 mm. Constitute.

Next, the operation of the above configuration will be described. As shown in FIG. 3A, which is an analysis result of the present invention, the distance x also defined in FIG.
In the case of 35 mm or more, the natural frequency f of the above equation (1) is 30H
z or less. Here, since the width of the transport separator element 7 is about 50 mm and the width of the fuel spacer 6 is about 30 mm,
If the fuel spacer 6 and the transport separator 8 are separated by 70 mm or more, the natural frequency f becomes 30 Hz or less.
The natural frequency of the vibration mode caused by the support method during transportation of the WR fuel body 1 can be set to a value of 30 Hz or less.

Accordingly, the natural frequency region of the BWR fuel assembly 1 can be kept away from the natural frequency region of the transportation,
The resonance with the vibration of the transportation is avoided, and the fuel rod 3 of the BWR fuel body 1 is prevented from being damaged by the large vibration caused by the resonance.

In the third embodiment , as shown in FIG.
In the R fuel body 1, the lower tie plate 5 and the fuel spacer 6-1
In the first span formed between the BWR fuel body 1 and the inner container 9, etc., the position where the transport separator 8 is interposed is adjusted by the fuel spacer 6-1. as a distance more than necessary, with release the transport separator by a distance l ₂ between the fuel spacer 6-1,
The position is as close as possible to the fuel spacer 6-1. For example, the minimum value at the distance l ₂ is 5
mm.

Next, the operation of the above configuration will be described. In the BWR fuel assembly 1, the lower tie plate 5
In the first span between the fuel separator 3 and the fuel spacer 6-1, the position of the transport separator 8 inserted between the fuel rods 3 is
It is farther than lower tie plate 5.

Thus, in the first span of the BWR fuel assembly 1, the restraining force on the large number of fuel rods 3 due to the interposition of the transport separator 8 is minimized.
When the WR fuel body 1 falls vertically, the BWR fuel body 1
Is easily absorbed by the deformation and deformation of the lower tie plate 5 and the vibration and deformation of the fuel rods 3 of the first span, so that sufficiently high shock resistance can be maintained. Therefore, even when the BWR fuel body 1 is vertically dropped, the impact at the time of a drop collision is easily alleviated, so that damage to the fuel rod 3 is avoided and safety is improved.

The BWR fuel assembly 1 has a heat-generating M
Even in the case of the OX fuel body, the transport separator 8 inserted in the large number of fuel rods 3 in the first span is longer than the distance required to absorb the difference in thermal expansion between the inner container 9 and the BWR fuel body 1. It is separated from the fuel spacer 6-1. As a result, the fuel spacer 6-1 does not come into contact with the transport separator 8 due to a difference in thermal expansion or the like, so that the fuel rod 3 and the fuel spacer 6 are not damaged.

[0044]

As described above, according to the present invention, the natural frequency caused by the supporting method in the transportation state of the BWR fuel body is reduced, and the resonance with the vibration in various transportation means is avoided. Wear at the metal contact portion of the fuel rod due to the generated severe vibration can be prevented.

[0045]

[Brief description of the drawings]

FIG. 1 is a plan view of a fuel body and an inner container during transportation of a BWR fuel body according to a first embodiment of the present invention.

FIGS. 2A and 2B are calculation model diagrams of the rigidity of a support portion during transportation of a BWR fuel body according to the first embodiment of the present invention, wherein FIG. 2A shows the present invention and FIG.

FIG. 3 is a characteristic curve diagram of a natural frequency caused by a supporting method during transportation of the BWR fuel body according to the first embodiment of the present invention,
(A) shows the present invention, and (b) shows a conventional example.

FIG. 4 is a side view of a main part of a supporting method for minimizing a natural frequency of the BWR fuel body during transportation according to the first embodiment of the present invention, wherein (a) is the present invention and (b) is a conventional example. Is shown.

FIG. 5 is a partially cutaway side view of a BWR fuel assembly during transportation according to a second embodiment of the present invention.

FIG. 6 is a partially cutaway side view of a BWR fuel assembly during transportation according to a third embodiment of the present invention.

FIG. 7 is a plan view of a fuel body, an inner container, and the like during transportation of a conventional BWR fuel body.

FIG. 8 is a transport separator, (a) showing A in FIG. 7;
FIG. 2B is a cross-sectional view taken along the line A, FIG. 2B is an enlarged front view of a main part of the transport separator element, and FIG. 2C is an enlarged side view of the transport separator element.

[Explanation of symbols]

1 ... BWR fuel body, 2 ... missing number, 3 ... fuel rod, 4 ... upper tie plate, 5 ... lower tie plate, 6,6-1 to 6-7 ...
Fuel spacer, 7: transport separator element, 8: transport separator, 9: inner container, 10: corrugated leaf spring, 11: outer frame, L ₁ : distance between fuel spacers (span), l ₁ ,
l ₂ , x ... distance.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-180699 (JP, A) JP-A-1-75896 (JP, U) JP-A 64-46797 (JP, U) (58) Investigation Field (Int.Cl. ⁷ , DB name) G21F 5/008 G21C 3/00

Claims (1)

(57) [Claims] 1. A fuel container for a boiling water reactor is inserted into a fuel protection container or an inner container of a transport container by interposing a transport separator between the fuel spacers and between the fuel spacer and the upper tie plate and the lower tie plate. In the method for transporting a boiling water reactor fuel body, which is stored in a container and transports the transport container in a horizontal state, the transport separator includes two transport separator elements that are vertically combined with each other in a horizontal direction. The combination is configured as one set, one set between each fuel spacer, between the fuel spacer and the upper tie plate near the upper tie plate, and between the fuel spacer and the lower tie plate near the lower tie plate. Between the fuel spacers and the fuel spacer near the upper tie plate and the upper tie plate. The transport separator interposed between the plates must be connected to the nearest fuel spacer or upper tie plate.
A method for transporting a fuel body for a boiling water reactor, comprising transporting the fuel body in a state of being disposed at a position separated by 70 mm or more.