JPH07120590A - Nuclear fuel transporting container - Google Patents

Abstract

PURPOSE:To make it possible to make sure of sealing up nuclear fuel against heating such as a fire providing an inner container where an insulation is installed on all wall surfaces for containing fuel assemblies and an outer container to contain such an inner container. CONSTITUTION:An inner container 34 has a double-walled structure, where all wall surfaces consist of an inner shell and an outer shell, and an insulation 31 is filled in the gap between the inner and outer shells. The inner container 34 consists of a main body 32 and a cover 33 and is fixed with bolts. Then, this inner container is suspended from the inner wall of an outer metal container 36 by a vibration-proof mechanism 35. The mechanism 35 is equipped with a supporting plate 37 welded on the inner wall of the outer container 36. This supporting plate 37 is equipped with members 39 which support elastic rubbers 38 and the like by protruding toward the inner container 34 at intervals in the vertical direction. The use of this container 30 can control the rise in the temperature of fuel rods.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nuclear fuel transportation container,
In particular, the present invention relates to a nuclear fuel transportation container that can withstand the heat of a fire or the like when the fuel assembly is transported and that does not impair the quality against impact.

[0002]

2. Description of the Related Art A fuel assembly is manufactured in a nuclear fuel factory and used in a nuclear power plant. In order to transport this fuel assembly from a nuclear fuel factory to a nuclear power plant, a transportation container that ensures subcriticality, hermeticity, etc. that satisfy legal standards is used.

As shown in FIG. 12, this fuel assembly 10 normally bundles a plurality of nuclear fuel rods 11 through elastic members 12, 12, ... And joint parts 13, at both ends of the bundled nuclear fuel rods 11. 14 is attached and assembled.

Here, the nuclear fuel rod 11 accommodates a nuclear fuel pellet and has a total length of about 4 m and a diameter of about 1 cm and is formed of a metal pipe.

Therefore, the total length of the fuel assembly 10 is about 4.5.
The width is about 14 cm and the weight is about 300 kg.
It becomes the weight of.

In order to safely transport the heavy and long fuel assembly 10, a nuclear fuel transportation container 15 as shown in FIGS. 13 and 14 has been conventionally used. This nuclear fuel transport container 1
5 will be described.

First, the fuel assembly 10 is packaged 1 by 1
After being wrapped with 6, the vias 17 are respectively set in the compartments inside the metallic inner container body 18 forming the inner container 20. The inner container body 18 is covered with an inner container lid body 19, and the inner container body 18 and the inner container lid body 19 are attached by bolts or the like.
And are fixed.

On the outside of the inner container 20, packing materials 21, 2 are provided.
After 1 and the like are attached, they are housed in a wooden outer container body 22 forming an outer container 25, covered with an outer container lid 23 and fixed by bolts 24, 24, and the outer container 25 is The nuclear fuel transportation container 15 is assembled by being fastened by the steel belts 26, 26.

[0009]

Thus, the nuclear fuel transportation container 15 accommodating the fuel assembly 10 is mounted on a truck, a freight car (not shown) or the like and transported from a nuclear fuel factory or the like to a nuclear power plant.

In such transportation, the nuclear fuel transportation container 1
Subcriticality and hermeticity must be ensured while ensuring the quality of the fuel assembly 10 in the fuel cell 5.

However, during transportation of the nuclear fuel transportation container 15, a shock is applied to the floor of a truck or the like from the road surface, and this shock is transmitted to the fuel assembly 10 and adversely affects the quality of the elastic member of the nuclear fuel 10 or the nuclear fuel pellets. May affect. Therefore, it is necessary to reduce the impact and maintain the quality by the packing material 16 wrapping around the fuel assembly 10 and the packing material 21 attached inside the outer container 25.

It is also conceivable that an accident such as a fire will be encountered during transportation of the nuclear fuel transportation container 15 or during storage of the nuclear fuel. In such a case, in the nuclear fuel transport container 15, the wooden outer container 25 disappears, the inner container 20 is exposed, and the temperature reaches 800 ° C. Therefore, the nuclear fuel 10 housed in the inner container 20 becomes high in temperature, so there is no problem with the currently designed nuclear fuel, but in the fuel assembly 10 for high combustion in the future, the pressure of the gas sealed in the nuclear fuel rods 11 will be high. Therefore, if the inner container 20 exists at 800 ° C. or higher for a long time, the nuclear fuel rods 11 may expand and break, and the sealing performance may not be ensured.

Therefore, in order to solve the above-mentioned problems, the present invention protects the fuel assembly by a heat insulating material and, if necessary, supports a container for accommodating the fuel assembly by a vibration isolation mechanism and applies heating and peaks to the nuclear fuel. The present invention provides a nuclear fuel transportation container adapted to absorb the vibration.

[0014]

According to the present invention, there is provided an inner container for accommodating a fuel assembly, the inner container having an insulating material on all wall surfaces thereof, and an outer container for accommodating the inner container. The present invention provides a nuclear fuel transportation container.

Further, the present invention provides a nuclear fuel transportation container characterized in that the inner container is supported by a vibration isolation mechanism attached to the outer container.

Further, the present invention provides a nuclear fuel transportation container characterized in that the vibration isolation mechanism is provided with elastic rubber.

[0017]

The fuel assembly is housed in the outer container after being housed in the inner container insulated by the heat insulating material.

As a result, even if a fire or the like occurs during transportation, the fuel assembly does not reach a high temperature and the fuel rods are not damaged, and the hermeticity is ensured.

Further, in the case where the vibration-proof mechanism is provided, the vibration-proof mechanism absorbs the shock even during transportation, so that the elastic member and the nuclear fuel pellets inside the nuclear fuel rod are not damaged and the deterioration of quality is prevented. .

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the nuclear fuel transportation container of the present invention will be described below with reference to the accompanying drawings. Since the basic configuration of the nuclear fuel transportation container 30 of the present invention is almost the same as that of the conventional nuclear fuel transportation container 15, the same portions are denoted by the same reference numerals and detailed description will be omitted.

An outline of the nuclear fuel transportation container 30 of the present invention is shown in FIGS. 1 and 2.

In the figure, reference numeral 34 is an inner container, and the inner container 34 has a double-wall structure in which the entire wall surface is composed of an inner shell and an outer shell, and the thickness is 50 mm in the gap between the inner shell and the outer shell. It is filled with a heat insulating material 31 which is solidified into a fibrous material of alumina and silica to a degree, and the inner container 34 thereof includes an inner container body 32 and an inner container lid 3.
3 and is fixed by bolts. The fuel assembly 10 is housed in each of the two compartments A and B divided by the partition wall in the inner container body 32.

Details of the inner container 34 are shown in FIGS.
A metal outer container 36 via a vibration isolation mechanism 35 as shown in FIG.
It is adapted to be suspended on the inner wall 36a of the.

A support plate 37 welded to the inner wall of the outer container 36 is attached to the vibration isolation mechanism 35. A support member 3 for supporting the elastic rubbers 38, 38 ...
9 and 39 are attached.

A hole penetrating in the vertical direction is provided in the central portion of the supporting members 39, 39. Bolts 40, 40 are passed through the holes through sleeves, washers, elastic rubbers 38, 38, etc., and nuts 41, 41, ... can be screwed into the holes.

The inner container 3 is provided between the elastic rubbers 38, 38 ...
A projecting support piece 43 projecting from the side of the L-shaped angle 42 that elastically supports 4 is inserted.

A hole extending vertically is formed in the center of the projecting support piece 43, and the bolts 40, 4 are formed in the hole.
0 is passed through and is attached integrally with the elastic rubbers 38, 38.

At the upper and lower portions of the L-shaped angle 42, support members 44 and 45 for connecting and supporting the L-shaped angle attached to the other vibration-proof mechanism are attached to prevent the angle from shaking. A packing material such as cardboard is appropriately attached to the inner surface of the outer container 36.

The temperature characteristics, shock characteristics, and vibration transmission characteristics that can be assumed when the nuclear fuel transportation container 30 thus constructed is transported by a truck or the like will be examined. But,
When the container 30 of the present invention is used, the temperature rise of the nuclear fuel rod can be reduced. That is, in the conventional transportation container, when the wooden outer container 25 is burned down and the inner container is exposed when placed in an environment of 800 ° C. simulating a fire, the inner container quickly reaches the related temperature of 800 ° C. The surface temperature of the rods will be the same.

FIG. 5 shows the temperatures of the surface of the outer container 36, the surface of the inner container 34 and the surfaces of the nuclear fuel 10, 10 when the nuclear fuel transport container 30 is placed in an environment of about 800 ° C. simulating a fire. is there. According to this, the surface of the outer container 36 reaches 800 ° C. as shown by the dotted line, but the inner container 3
The surface temperature of 4 is about 5 at the highest value as shown by the chain line.
The temperature of 00 ° C. and the surface of the fuel assemblies 10 and 10 can be suppressed to 300 ° C. or lower as shown by the solid line. Therefore, the nuclear fuel rod 11 for high combustion in which a high-pressure gas is enclosed can be prevented from being damaged by the expansion of the gas and the sealing performance can be secured.

By the way, in general, the transmission rate of vibration can be expressed by the following equation using the input vibration frequency f and the natural vibration Fn of the elastic rubber.

[Equation 1]

According to this equation, the transmissibility increases as the input frequency and the natural frequency are closer to each other. In addition, the side where the input frequency is lower than the natural frequency is not significantly damped. FIG. 11 shows an example of the impact due to the vibration transmitted from the road surface to the vehicle floor that transports the nuclear fuel 10 during transportation. It can be seen from this figure that there are peaks near 5 Hz and 18 Hz, and that the vicinity of this frequency is a factor of impact.

The elastic rubber 38 used in the present invention can obtain an arbitrary natural frequency by changing its composition.
As a result, by selecting the elastic rubber 38 having a natural frequency far from the frequency that most affects the quality among the vibrations received from the road surface during transportation, the impact due to the vibration transmitted from the road surface to the fuel assembly 10 is reduced. , The impact on quality can be reduced. FIG. 10 shows the vibration transmissibility of the conventional container packaging material. FIG. 7 shows the vibration transmissibility of the elastic rubber 38 according to the present invention.

FIG. 6 shows the frequency and magnitude of an impact example due to vibration transmitted from the road surface to the nuclear fuel, and the conventional packaging material 16 for a container.
The magnitude of the impact transmitted to the fuel assembly 10 by the above and the magnitude of the impact transmitted to the fuel assembly 10 by the elastic rubber 38 of the present invention are shown.

Therefore, although the impact characteristic P applied to the conventional nuclear fuel transport container 15 peaks at around 5 Hz and 18 Hz, it gives a large impact to the nuclear fuel transport container 15, but the nuclear fuel transport container 30 of the present invention has an impact Q near 5 Hz. , 18Hz
The impact Q in the vicinity is absorbed and significantly reduced.

Therefore, the impact characteristic P of the conventional nuclear fuel transportation container 15 is remarkably improved like the impact characteristic Q in the nuclear fuel transportation container 30 of the present invention. As a result, the fuel assembly 1
0, in particular, the impact of the nuclear fuel rods 11 is reduced, the nuclear fuel pellets and elastic members contained therein are prevented from being damaged, and the deterioration of quality can be suppressed.

In the above-mentioned embodiment, the heat insulating material 31 obtained by solidifying alumina and silica into a fibrous shape is used, but the same effect can be obtained by using a foaming heat insulating material.

Further, the neutron absorbing material can be dispersed in the foaming heat insulating material to improve the final criticality of the container 30.

As the vibration isolation mechanism 35, vibration isolation mechanisms 50 and 60 as shown in FIGS. 8 and 9 may be used. That is, in the vibration isolation mechanism 50 shown in FIG. 8, the support members 51, 52 are provided between the angle 42 supporting the inner container 34 and the outer container 36.
Are provided, spherical elastic rubbers 53, 53 between the support members 51, 52 are inserted, and these are fixed by bolts 54, nuts 55 and the like via a pressing plate or the like.

With such a structure, the compressive force and the shearing force can be utilized from the whole, unlike the one utilizing the vertical compressive force and the lateral shearing force.

Further, in the vibration isolation mechanism 60 shown in FIG. 9, a three-dimensional elastic rubber 61 is inserted between the angle 42 supporting the inner container 34 and the outer container 37 and fixed by screws 62. .

With such a structure, it is possible to absorb the impact from the whole.

[0047]

As described above, the nuclear fuel transport container of the present invention comprises an inner container provided with a heat insulating material on all wall surfaces for housing a fuel assembly, and an outer container for housing this inner container. As a result, it is possible to ensure the sealing performance of the nuclear fuel against heating such as a fire.

When the inner container is supported by the vibration isolation mechanism attached to the outer container, the impact during transportation can be further prevented and the quality of nuclear fuel can be secured.

Further, since the vibration isolation mechanism is provided with the elastic rubber, it is easy to assemble and handle.

[Brief description of drawings]

FIG. 1 is a sectional view showing a main part of a nuclear fuel transportation container of the present invention.

FIG. 2 is a perspective view showing a main part of the nuclear fuel transportation container of the present invention.

3 is a front view showing the vibrating mechanism of FIG. 2, taken along line III-III in FIG. 4 and viewed in the direction of the arrow.

FIG. 4 is a cross-sectional view showing the vibration mechanism of FIG. 2 taken along line IV-IV in FIG. 3 and seen from the direction of the arrow.

FIG. 5 is an explanatory view showing temperature characteristics of the nuclear fuel transportation container of the present invention.

FIG. 6 is an explanatory view showing impact characteristics of the nuclear fuel transportation container of the present invention.

7 is an explanatory diagram showing impact characteristics of the elastic rubber shown in FIGS. 3 and 4. FIG.

FIG. 8 is an explanatory view showing another vibrating mechanism.

FIG. 9 is an explanatory view showing another vibration mechanism.

FIG. 10 is an explanatory diagram showing impact characteristics of a general nuclear fuel transportation container.

FIG. 11 is an explanatory diagram showing impact characteristics of a floor surface of a general truck or the like.

FIG. 12 is a front view showing a partially used cross section of a commonly used fuel assembly.

FIG. 13 is a sectional view showing a main part of a conventional nuclear fuel transportation container.

FIG. 14 is a perspective view showing a main part of a conventional nuclear fuel transportation container.

[Explanation of symbols]

 10 Nuclear Fuel 11 Nuclear Fuel Rod 12 Elastic Member 15 Nuclear Fuel Transport Container 16 Packing Material 20 Inner Container 21 Packaging Material 25 Outer Container 30 Nuclear Fuel Transport Container 31 Insulation Material 34 Inner Container 35 Vibration Isolation Mechanism 36 Outer Container 37 Support Plate 38 Elastic Rubber 39 Support Member 40 bolts 41 nuts 42 angle 43 projecting support pieces 44, 45 support materials 50, 60 anti-vibration mechanism 53, 61 elastic rubber

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display area G21F 5/00 S

Claims (3)

[Claims] 1. A nuclear fuel transportation container comprising: an inner container for accommodating a fuel assembly, the wall surface of which is provided with a heat insulating material; and an outer container for accommodating the inner container. 2. The nuclear fuel transportation container according to claim 1, wherein the inner container is supported by a vibration isolation mechanism attached to the outer container. 3. The nuclear fuel transport container according to claim 1, wherein the vibration isolation mechanism is provided with elastic rubber.