Induced nuclear reactions: processes – systems – and elements – Handling of fission reactor component structure within... – Storage container systems for new and/or irradiated core...
Utility Patent
1998-07-01
2001-01-02
Carone, Michael J. (Department: 3643)
Induced nuclear reactions: processes, systems, and elements
Handling of fission reactor component structure within...
Storage container systems for new and/or irradiated core...
C376S261000
Utility Patent
active
06169777
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel transport container to transport a reactor fuel while housing a reactor fuel (fuel assembly) and a method of transporting the fuel assembly.
In particular, the present invention relates to a transport container having a compact size and a large capacity, which is able to simultaneously transport a great many of light water reactor fuels, such as mixed-oxide fuel assemblies and a method of transporting the great many light water reactor fuels.
2. Description of the Prior Art
In a light water reactor such as a boiling water reactor, a pressurized water reactor or the like, a mixed-oxide fuel assembly (hereinafter, referred to simply as MOX fuel assembly), which mixes a plutonium oxide (PuO
2
) and an uranium oxide (UO
2
), is used as a reactor fuel. The MOX fuel assembly is made in a fuel processing facility, and thereafter, is protected while being housed in a fuel protective container. Then, the fuel protective container is transported while being mounted into a fuel transport container.
In the case of transporting a light water reactor fuel assembly such as MOX fuel assembly, when a vibration is applied to the light water reactor fuel assembly, an abrasion is caused in a metallic contact portion of the light water reactor fuel assembly. This is undesirable to maintain economy and reliability of the light water reactor fuel assembly. On the other hand, a spent fuel assembly has no problem with abrasion caused during transport. Therefore, no special vibration preventive measures is taken with respect the spent fuel assembly. Thus, because the spent fuel assembly does not require special vibration preventive measures, there has been developed a fuel transport container which has a compact size and large capacity with a simple structure and can house a great many spent fuel assemblies.
On the contrary, in the case of transporting a new fuel assembly such as MOX fuel assembly, the MOX fuel assembly is used as a reactor fuel after transport. For this reason, vibration preventive measures must be taken during transport for safety and reliability. More specifically, the new fuel assembly or a fuel protective container housing the new fuel assembly is housed in a basket of a fuel transport container, and thereafter, there is a need of fixedly supporting the new fuel assembly to the basket, for example, by a fixedly supporting device. In this case, a ratio of a space occupied by the fixedly supporting device becomes large in the basket. This is a factor hindering the development of fuel transport containers which have a large capacity and a compact size and can collectively and simultaneously house a great many new fuel assemblies. For this reason, a transport container equivalent to the transport container for the spent fuel assembly, that is, a compact-size and large-capacity transport container for the new fuel assembly, such as the MOX fuel assembly, has not been developed.
In the case of transporting the MOX new fuel assembly, it is extremely well known to use a protective container or an internal container having a relatively large rigidity, which is provided with a protective member or a buffer member. That is, it is carried out to house the MOX new fuel assembly in the protective container to transport the protective container housing the MOX new fuel assembly, together. A conventional fuel transport container has the following problems. More specifically, in the case of inserting the MOX new fuel assembly directly into a narrow basket hole of the conventional fuel transport container so as to house the MOX new fuel assembly therein, because there is the possibility of the MOX fuel assembly being wounded by contact upon insertion, an area of the opening of the basket hole is enlarged to some degree.
Moreover, in the case of inserting the MOX new fuel assembly directly into the narrow basket hole, because it is difficult to arrange the MOX fuel assembly to one side in the transport container, that is, a so-called “one-side biased arrangement” is not carried out therein, there is a need of pressing four side surfaces (side walls) of the new fuel assembly by using the fixedly supporting device so that the new fuel assembly can be fixedly supported in the basket hole of the fuel transport container. Thus, in the fuel transport container, a space occupied by the fixedly supporting device becomes large. Therefore, in the entirety of the fuel transport container, a large space is occupied by the fixedly supporting device as compared with the case of using the protective container for housing the new fuel assembly.
In this case, the aforesaid “one-side biased arrangement” is employed to mean the following operation that the fuel assembly vertically inserted into the basket hole of the fuel transport container is moved into contact with two adjacent inner surfaces of the basket hole.
However, since the fuel assembly has a small bending rigidity, in the case of pressing (biasing) and moving the fuel assembly from one side surface or two side surfaces thereof in the basket hole, it is difficult to arrange the fuel assembly in a one-side biased state because there is the possibility that the fuel assembly itself becoming bent.
In the case of pressing the MOX new fuel assembly from four side surfaces thereof so as to fixedly support it in the basket hole of the fuel transport container, one fixedly supporting device is situated under the fuel assembly in a state that the fuel transport container is horizontally placed, that is, an axial direction (longitudinal direction) of the fuel transport container is positioned along a horizontal plane, during the transporting operation of the fuel transport container. Since the fixedly supporting device situated under the fuel assembly must receive the weight of the fuel assembly, there is required a great force for tightly fixing the fuel assembly to the fuel transport container. In order to obtain the tightly fixing great force, the fixedly supporting device must be firmly constructed. This is a factor of making large the fixedly supporting device, and increasing the space occupied by the fixedly supporting device.
If the MOX new fuel assembly is transported while being housed directly in the basket hole of the fuel transport container without housing the fuel assembly in the fuel protective container, it is possible to dispense with a process for housing the fuel assembly in the fuel protective container. Therefore, it is possible to reduce the cost of transporting the fuel transport container.
However, since the fuel assembly has a small bending rigidity and there is a problem relative to the above difficulty of the one-side biasing, the fuel assembly is not transported while being directly housed in the basket hole of the fuel transport container.
On the other hand, in the case where the MOX new fuel assembly is housed in the fuel protective container, and is transported with the use of the fuel transport container, the following problem relative to the difficulty of the one-side biasing is caused.
In the case of housing the MOX new fuel assembly one by one in the fuel protective container, the protective container housing the fuel assembly is relatively light weight; therefore, no problem relative to one-side biasing is caused therein. On the contrary, in order to provide a fuel transport container which is a compact size and has a large capacity, in recent years, there has been proposed a fuel protective container which can house a plurality of fuel assemblies, that is, four fuel assemblies. In this case, the protective container housing the fuel assembly is relatively heavy weight, for this reason, there is a problem that it is difficult to bias the fuel assembly to one side.
In the above transport containers, it has been strongly expected to develop a fuel transport container having a compact size and large capacity. However, in order to develop the aforesaid fuel transport container having a compact size and large capacity, there is a need of solvi
Ozawa Tamotsu
Yoshizawa Hiroyasu
Carone Michael J.
French III Fredrick T.
Kabushiki Kaisha Toshiba
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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