WO2002025670A1

WO2002025670A1 - Container for nuclear fuel transportation

Info

Publication number: WO2002025670A1
Application number: PCT/JP2000/006412
Authority: WO
Inventors: Masahiro Tooma; Masashi Shimizu; Kouichi Maki; Masashi Oda; Naoki Kumagai; Takashi Nishi
Original assignee: Hitachi, Ltd.
Priority date: 2000-09-20
Filing date: 2000-09-20
Publication date: 2002-03-28
Also published as: JPWO2002025670A1

Abstract

A container for nuclear fuel transportation comprises first and second cylindrical bodies of carbon steel (or stainless steel). The first cylindrical body encloses a plurality of spent fuel assemblies. The second cylindrical body encloses the first cylindrical body. Between the first and second cylindrical bodies is provided a first neutron shield composed of a material (for example, W, Gd or Mn) whose inelastic scattering cross section is greater than those of the cylindrical bodies. A second neutron shield containing hydrogen surrounds the second cylindrical body inside an outer cylindrical body. The first neutron shield effectively shields the neutrons of 105-107 eV energy, and it helps decrease the weight of the container for nuclear fuel transportation.

Description

Specification

Nuclear fuel container technical field

The present invention relates to a nuclear fuel transport container, and more particularly to a nuclear fuel transport container for transporting a spent nuclear fuel assembly generated in a nuclear power plant. Background art

Spent nuclear fuel assemblies generated at nuclear power plants are dedicated nuclear fuel that can (1) secure radiation shielding, (2) secure subcriticality, (3) secure sealing, and (4) secure structural strength. Loaded in transport containers (or nuclear fuel transport and storage containers) and transported from nuclear power plants to storage locations.

Conventionally, nuclear fuel transport containers for spent nuclear fuel have been developed using high-energy neutrons as described in Nuclear Fuel Transport Engineering Carbon steel or stainless steel is used as a shielding material. This high-energy neutron shielding material is also used as a structural material of the container body of a nuclear fuel transport container. The conventional nuclear fuel transport container is an outer cylinder made of carbon steel (or stainless steel), an inner cylinder made of carbon steel (or stainless steel) installed inside the outer cylinder, and placed between the outer cylinder and the inner cylinder. Neutron shield (consisting of materials containing hydrogen or boron). Further, the nuclear fuel transport container includes a basket forming a plurality of spaces for storing the spent fuel assemblies inside the inner cylinder. The neutrons emitted from the spent fuel assemblies loaded in the basket are shielded by the inner cylinder and then decelerated and shielded by the neutron shield.

Neutron shields used in nuclear fuel transport containers are generally made of organic substances. Therefore, in the safety analysis evaluation, in the test evaluation under special test conditions (evaluation at the time of fire), the shielding analysis is performed assuming that it does not exist because it burns and burns. At this time, Japanese law stipulates that the dose equivalent rate at a location 1 m away from the surface of the nuclear fuel transport container (the surface of the outer cylinder) must be less than 10 mS v / hr. The value of the dose equivalent rate is the transport standard value of the IAEA, which is also observed in countries other than Japan, and is called the 'limited dose equivalent rate'. Currently, the spent fuel assemblies for BWRs currently being transported in Japan are a fuel assembly with an 8-by-8 fuel rod array and a small diameter water rod (Step I fuel assembly). is there. The diameter of the small-diameter water inlet is larger than the diameter of the fuel rods but smaller than the pitch of the fuel rods.Step I The fuel assembly has a burnup of about 33 GWd / t before being loaded into the reactor. This is a fuel assembly (referred to as Step I fuel assembly) having an 8 × 8 fuel rod array. This Step I fuel assembly will achieve a dose equivalent rate (10 m SV no hr) or less in a conventional nuclear fuel transport container.

At present, a high burnup (approximately 39 GWd / t) fuel assembly (step 39) with a large diameter water inlet and fuel rods arranged in 8 rows and 8 columns, which is currently used in a nuclear power plant using BWRs A fuel assembly with a higher burnup (approximately 45 GWd / t), in which fuel rods that are beginning to be used at the nuclear power plant are arranged in 9 rows and 9 columns, and are expected to be used. Some MOX fuel assemblies generate significantly more neutrons than Step I fuel assemblies. The nuclear fuel transport container that transports these high burn-up fuel assemblies and MOX fuel assemblies must satisfy the above-mentioned limited dose equivalent rate, so the inner cylinder made of carbon steel (or stainless steel) is required. Must be very thick. An increase in the thickness of the inner cylinder leads to an increase in the weight of the nuclear fuel transport container, and consequently This leads to a decrease in the number of stored nuclear fuel assemblies that can be stored inside to satisfy the limit weight of the nuclear fuel transport container. This reduces the number of containers per nuclear fuel transport container and reduces the transport efficiency of spent fuel assemblies. Disclosure of the invention

An object of the present invention is to provide a nuclear fuel transport container capable of improving the transport efficiency of a spent fuel assembly.

A feature of the present invention is that it is provided adjacent to a cylindrical body made of either carbon steel or stainless steel, surrounding a plurality of spent fuel assemblies housed therein, and In addition, a neutron shield composed of a material having a large inelastic scattering cross section is provided.

A neutron shield composed of a material having a larger inelastic scattering cross-sectional area than a cylindrical body can be thinner than a case where the neutron shield is composed of carbon steel and stainless steel. For this reason, the weight of the nuclear fuel transport container can be reduced, and the number of spent fuel assemblies that can be stored in the nuclear fuel transport container can be increased. This can improve the transportation efficiency of spent fuel assemblies by the nuclear fuel transport container.

A feature of the first embodiment of the present invention is that the neutron shield provided adjacent to the cylindrical body is arranged inside other neutron shields containing hydrogen. Since the former neutron shield is located inside the latter neutron shield, the weight of the nuclear fuel transport container is reduced. This is because the weight of the former neutron shield becomes smaller as the neutron shield is located inward in the radial direction.

A feature of the second embodiment of the present invention, 1 0 ⁵ to 1 0 ⁷ for the neutral terminal of the energy e V, inelastic the neutron shielding member provided adjacent to the tubular body The elastic scattering cross section is larger than the inelastic scattering cross section of the cylindrical body for neutrons of that energy. Neutron shielding body is improved shielding ability against 1 0 ⁵ to 1 0 ⁷ energy neutrons e V. Therefore, the thickness of the neutron shield in the radial direction is reduced, and the number of spent fuel assemblies that can be stored in the nuclear fuel transport container increases. The neutron shield is preferably composed of one of tungsten, gadolinium and manganese.

Another feature of the present invention is that a first cylindrical body made of either carbon steel or stainless steel, and a first cylindrical body made of either carbon steel or stainless steel And a neutron shield provided between the first and second cylindrical bodies and made of a material having a larger inelastic scattering cross-sectional area than the cylindrical body. Have prepared. According to the other features, the effects obtained by the features of the present invention described above can be obtained. In addition, according to other features, since it is located inside the second cylindrical body, even in the event of an accidental drop of the nuclear fuel transport container, a material having a larger inelastic scattering cross-sectional area than the cylindrical body This prevents the neutron shielding body constituted by the scattered scattered particles from scattered outside and reduces the shielding ability of the nuclear fuel transport container. Further, since the neutron shield is located outside the first cylindrical body, an increase in the weight of the neutron shield is suppressed, and the weight of the nuclear fuel transport container is further reduced. A feature of the third embodiment of the present invention is that the first cylindrical body, the second cylindrical body, and the neutron shielding provided between the first cylindrical body and the second cylindrical body. That is, the first neutron shielding body, which is a body, is disposed inside the second neutron shielding body which is annularly arranged containing hydrogen. According to the third embodiment, since the first neutron shield is arranged inside the second neutron shield, the same effects as those obtained by the features of the first embodiment described above are produced. I will.

A feature of the fourth embodiment of the present invention is that the thickness of the first cylindrical body in the radial direction is smaller than the thickness of the second cylindrical body in the radial direction. The decrease in the thickness of the first cylindrical body in the radial direction depends on the position at which the neutron shield provided between the first cylindrical body and the second cylindrical body is disposed, and the axial center of the nuclear fuel transport container. Closer. Therefore, the weight of the neutron shield is reduced, and the weight of the nuclear fuel transport container is further reduced.

Still another feature of the present invention is that a first metal portion made of either carbon steel or stainless steel, and provided inside the first metal portion, wherein the first metal portion is more inelastic. A third neutron shield composed of a material having a large scattering cross-sectional area, a first lid attached to the container body, a second metal part composed of either carbon steel or stainless steel, and A second lid is provided inside the second metal part, has a fourth neutron shielding body containing hydrogen, and has a second lid which is attached to the container body so as to cover the first lid. The container body is made of either carbon steel or stainless steel, and is made of either a first tubular body surrounding a plurality of spent fuel assemblies housed inside, a carbon steel or stainless steel. A second tubular body configured and surrounding the first tubular body, provided between the first tubular body and the second tubular body, and having a less inelastic scattering cross-sectional area than the tubular body. A first neutron shield composed of a large material, a second neutron shield containing hydrogen, which is annularly arranged around the second cylindrical body, and a second neutron shield which is annularly arranged. It has an outer tubular body surrounding the outer side.

According to another feature of the present invention, since the container body is double-sealed by the primary lid and the secondary lid, the fuel rod cladding tube of the stored spent fuel assembly may be damaged. The radioactive material inside the fuel rod is Not released to Since the third neutron shield is provided in the primary lid and the fourth neutron shield is provided in the secondary lid located outside, the primary lid and the secondary lid are compact and their respective weights are reduced. Reducing the weight of the primary and secondary lids leads to a reduction in the weight of the nuclear fuel transport container.

Features of the fifth embodiment of the present invention, with respect to 1 0 ⁵ to 1 0 ⁷ e V the neutral terminal of the energy, non弹性scattering cross section of a third neutron shielding body, 1 0 ⁵ -

1 0 ⁷ for energy neutrons e V, in greater than inelastic scattering cross section of the first metal portion. The third neutron shielding body is improved shielding ability against 1 0 ⁵ to 1 0 ⁷ energy neutrons e V. For this reason, the thickness of the third neutron shield in the axial direction is reduced, and the weight of the nuclear fuel transport container is reduced. The third neutron shield is preferably composed of one of tungsten, gadolinium and manganese. BRIEF DESCRIPTION OF THE FIGURES

Fig. 1 is a characteristic diagram showing the relationship between neutron energy in a nuclear fuel transport container made of carbon steel and the neutron flux and dose equivalent rate at a location 1 m away from the surface of the nuclear fuel transport container, and Fig. 2 shows the neutron energy and Fig. 3 is a characteristic diagram showing the relationship between the cross-sectional areas of iron (Fe), Fig. 3 is a characteristic diagram showing the relationship between the neutron energy and each cross-sectional area of tungsten (W), and Fig. 4 is a graph showing the relationship between neutron energy and gadolinium (G d) is a characteristic diagram showing the relationship between each cross-sectional area, FIG. 5 is a characteristic diagram showing the relationship between neutron energy and each cross-sectional area of manganese (M n), and FIG. 6 is a preferred embodiment of the present invention. FIG. 7 is a longitudinal sectional view of a nuclear fuel transport container according to an embodiment, FIG. 7 is a transverse sectional view of FIG. 6, and FIG. 8 is an enlarged longitudinal sectional view of a lid of FIG. BEST MODE FOR CARRYING OUT THE INVENTION The inventors studied the neutron shielding characteristics of a nuclear fuel transport container. In particular, the neutron shielding characteristics of the nuclear fuel transport container when each of the Step I fuel assembly, the Step II fuel assembly, and the M0X fuel assembly were loaded were examined. These studies were based on analytical calculations. For example, a detailed neutron shielding calculation was performed taking into account the source spectrum of a high burnup fuel assembly, and the equivalent dose limit of the nuclear fuel transport container during test evaluation under special test conditions (evaluation at the time of fire). Rate was evaluated. This analysis and evaluation focused on changes in the neutron spectrum and dose equivalent rates. Figure 1 shows the calculation results for a nuclear fuel transport container with an inner cylinder and an outer cylinder made of carbon steel. In Fig. 1, the horizontal axis is the neutron energy, the left vertical axis is the neutron flux (relative value) at a distance of 1 m from the surface of the nuclear fuel transport container, and the right vertical axis is lm from the surface of the nuclear fuel transport container. The dose equivalent rate (relative value) at each location is shown. Calculation results shown in FIG. 1, although the neutron flux in a nuclear fuel transport container surface or al 1 m away is distributed standing I a wide range from 1 e V to 1 0 ⁷ e V, nuclear fuel transport container which indicates that the limit dose equivalent rate at 1 m away from the surface is dominated mainly to fast neutrons of ^{^{1 0 5 ~ 1 0 7 e}} V. That is, since limited dose equivalent rate at a distance lm from the nuclear fuel transport container surface which is mainly determined by fast neutrons ^{^{1 0 5 ~ 1 0 7 e}} V, by shielding neutrons of this energy region, the dose It was found that the equivalent ratio could be made very small. We, the nuclear fuel transport container of the above, fast neutrons ^{^{1 0 5 ~ 1 0 7 e}} V is the causes have difficulty shielded analytically. As a result, the inventors have found that inelastic scattering cross section of the iron is the main component of carbon steel (F e), relatively and ^{^{1 0 6 ~ 1 0 7 e}} V in about l barn (see FIG. 2) large but was noticed that an abrupt decrease in the 1 0 ⁶ e V than about 1 0- ² barn. Inelastic iron below the 1 0 ⁶ e V It has been clarified that the sudden decrease in the scattering cross section is the reason that fast neutrons are difficult to be shielded by the conventional nuclear fuel transport container.

From this result, the inventors found that if efficiently shield the faster neutrons ^{^{1 0 5 ~ 1 0 7 e}} V , which primarily determine the dose equivalent rate at a distance lm from the nuclear fuel transport container surface dose equivalent rate Thought it could be smaller. The non弹性scattering cross section in the energy range ^{^{1 0 5 ~ 1 0 7 e}} V a neutron is concluded that the larger material than carbon steel or stainless steel may be used in nuclear fuel transport container. Materials that satisfy this condition include tandatin (W), gadolinium (G d), and manganese (M n). Figures 2, 3, and 4 show the relationship between the energy of each neutron and each cross-section centered on the inelastic cross-section in Tandasten, gadolinium, and manganese, respectively. As is apparent from these figures, tungsten, Gadoriniumu and manganese, inelastic scattering cross section in the region of the neutron Eneru formic one ^{^{1 0 5 ~ 1 0 7 e}} V is summer large as 1 barn extent can shield neutrons of energy regions ^{^{1 0 5 ~ 1 0 7 e}} V that can not be shielded by a carbon steel (or stainless steel).

Nuclear fuel transport container, the neutron energy ^{^{1 0 5 ~ 1 0 7 e}} V inelastic scattering cross section is large material region (element), tungsten (W), Gadoriniu beam (G d), manganese (M n) By using it, the shielding performance of the nuclear fuel transport container is improved. For this reason, the thickness of the nuclear fuel transport container (for example, the thickness of at least one of the inner and outer cylinders made of carbon steel (or stainless steel)) necessary for neutron shielding can be reduced, The diameter becomes smaller. This leads to a reduction in the weight of the nuclear fuel transport container. By reducing the weight of the nuclear fuel transport container, the number of spent nuclear fuel assemblies that can be stored per nuclear fuel transport container can be increased. Therefore, the spent fuel collection The combined transport efficiency is improved.

A nuclear fuel transport container according to a preferred embodiment of the present invention will be described below with reference to FIGS. 6 and 7.

The nuclear fuel transport container 1 of the present embodiment stores a spent fuel assembly generated in a boiling water reactor. The nuclear fuel transport container 1 includes a primary lid 11, a secondary lid 13, and a container body 15. The container body 15 includes a basket 3, a first inner cylindrical body 4, a neutron shielding body 5, a second inner cylindrical body 6, a neutron shielding body 7, and an outer cylindrical body 9. The first inner cylindrical body 4, the neutron shielding body 5, the second inner cylindrical body 6, the neutron shielding body 7, and the outer cylindrical body 9 are arranged concentrically. The first inner cylindrical body 4, the second inner cylindrical body 6, and the outer cylindrical body 9 are made of carbon steel, but may be made of stainless steel. Each of the first inner cylindrical body 4, the second inner cylindrical body 6, and the outer cylindrical body 9 has a container shape having a cylindrical side wall and a bottom connected to the side wall. The neutron shield 5 is tungsten. A basket 3 having a plurality of fuel storage spaces partitioned in a grid is provided inside the first inner cylindrical body 4. A support 16 extending horizontally from the basket 3 is in contact with the inner surface of the first inner cylindrical body 4. The first inner cylindrical body 4 is located inside the second inner cylindrical body 6. The neutron shield 5 is disposed between the first inner cylindrical body 4 and the second inner cylindrical body 6. That is, the neutron shield 5 is formed not only between the side wall of the first inner cylindrical body 4 and the side wall of the second inner cylindrical body 6, but also at the bottom of the first inner cylindrical body 4 and the second inner cylindrical body. Also provided between the bottom of 6. The outer cylindrical body 9 is located outside the second inner cylindrical body 6. A plurality of fins 8 extending in the axial direction of the second inner cylindrical body 6 are attached to the outer surface of the second inner cylindrical body 6 and reach near the inner surface of the outer cylindrical body 9. The neutron shield 7 is disposed between the second inner cylindrical body 6 and the outer cylindrical body 9. The neutron shield 7 contains hydrogen It is composed of quality organic matter (eg, resin).

Primary lid 11 is made of carbon steel. The primary lid 11 has a neutron shielding body 10 made of tungsten, and is attached to the first inner cylindrical body 4 of the container body 15 by screws 17 as shown in FIG. . The secondary lid 13 is also made of carbon steel. A neutron shield 12 made of resin is provided inside the secondary lid 13. The secondary lid 13 is attached to the second inner cylindrical body 6 of the container body 15 by screws 18 as shown in FIG. An annular gasket 19 seals between the secondary lid 11 and the first inner cylindrical body 4, and an annular gasket 20 seals between the secondary lid 13 and the second inner cylindrical body 6. . The primary lid 11 and the secondary lid 13 may be made of stainless steel.

The spent fuel assemblies generated from the boiling water reactor are stored in the spent fuel storage pool on the reactor terrestrial planet. Then, the spent fuel assemblies 14 stored for a predetermined period are stored in the nuclear fuel transport container 1. That is, the spent fuel assembly 14 is stored in the basket 3 with the primary lid 11 and the secondary lid 13 removed. After the spent fuel assemblies are stored in all the fuel storage spaces in the basket 3, the nuclear fuel transport container 1 is sealed with the primary lid 11 and the secondary lid 13. The nuclear fuel transport container 1 containing the spent fuel assemblies 14 is transported from the nuclear power plant to the nuclear fuel reprocessing facility. The secondary lid 13 and the primary lid 11 of the nuclear fuel transport container 1 are sequentially removed in the nuclear fuel reprocessing facility. The spent fuel assemblies 14 in the basket 3 are removed from the nuclear fuel transport container 1 and transferred to the spent fuel storage pool in the nuclear fuel reprocessing facility, where they are stored until they are reprocessed. Basket 3 is made of boron-containing stainless steel. Since the basket 3 contains boron, the criticality of nuclear fuel material in the spent fuel assembly stored adjacently can be prevented. During transport of spent fuel assemblies 14 in nuclear fuel transport container 1, The heat generated in the spent fuel assembly 14 is transmitted to the first inner cylindrical body 4 by radiation from the basket 3 and heat transfer through the basket 3 and the support 16. This heat is transmitted from the first inner cylindrical body 4 to the outer cylindrical body 9 via the neutron shielding body 5, the second inner cylindrical body 6, and the fins 8, and is transferred from the outer cylindrical body 9 to the outside. Released into the air. Since the neutron shield 7 is made of resin, its thermal conductivity is low, and the transfer of heat from the second inner cylindrical body 6 to the outer cylindrical body 9 is promoted by the fins 8.

In a normal state, the neutrons emitted from the spent nuclear fuel assembly 14 are, in the radial direction of the nuclear fuel transport container 1, the plate of the basket 3, the first inner cylindrical body 4, the neutron shield 5, the second inner It is shielded by the cylindrical body 6, neutron shielding body 7 and outer cylindrical body 9. In particular, the first inner cylindrical member 4 and the second inner cylindrical member 6 shield high energy neutrons emitted from the spent nuclear fuel assembly 14. Neutron shielding body 5 is constituted by Tandasute emissions of metals, as described above, a large non-elastic scattering cross section for high energy neutrons having an energy of ^{^{1 0 5 ~ 1 0 7 e}} V. Therefore, the neutron shielding body 5, Oite shielding ability is lowered to the first inner tubular member 4 and the second inner cylindrical member 6, 1 0 ⁵ to 1 0 ⁷ high energy neutrons e V efficiently shielding I do. The neutron shield 7 slows down and shields neutrons transmitted through the second inner cylindrical body 6. At the bottom (lower side in Fig. 6) of the nuclear fuel transport container 1, neutrons are also supplied to the bottom plate of the basket 3, the first inner cylindrical body 4, the neutron shield 5, the second inner cylindrical body 6, and the neutron shield 7 And is shielded by the outer tubular body 9. The neutrons in the lid of the nuclear fuel transport container 1 are also the metal part of the primary lid 11 (carbon steel), the neutron shield 10, the metal part of the secondary lid 13 (carbon steel) and the neutron shield 1 Shielded by two. Neutron shield 10 is similar to neutron shield 5, The high-energy neutrons ^{^{1 0 5 ~ 1 0 7 e}} V efficiently shielding. Neutron shielding body 1 0, shielding ability is lowered in the metal portion of the primary lid 1 1, to shield high energy neutrons ^{^{1 0 5 ~ 1 0 7 e}} V.

Next, the radiation shielding ability of the nuclear fuel transport container 1 in the event of a fire will be described. In the event of a fire, the neutron shields 7 and 12, which are composed of organic matter, will be destroyed. Therefore, the neutrons released from the spent nuclear fuel assembly 14 in the radial direction and the bottom of the nuclear fuel transport container 1 are the basket 3, the first inner cylindrical body 4, the neutron shield 5, and the second inner cylindrical body. Shielded by body 6 and outer tubular body 9. In the lid part of the nuclear fuel transport container 1, neutrons are shielded by the metal part of the primary lid 11, the neutron shield 10 and the metal part of the secondary lid 13.

When the neutron shields 7 and 12 are burned down by a fire, (1) the neutron shielding capacity in the radial direction in this embodiment, and (2) the radial direction of the nuclear fuel transport container when carbon steel is used instead of the neutron shield 5 The neutron shielding ability of the neutrons was examined. In Case II (carbon steel installation), the thickness of carbon steel that satisfies the limited dose equivalent rate in the event of a fire (less than OmS v / hr) was about 33 Omm. In Case I (5 neutron shields installed), the thickness of the neutron shield 5 that satisfies the limited dose equivalent rate in the event of a fire (l OmS v / hr or less) was about 130 mm. The specific gravity of carbon steel is 7.89 g / cm ³ and that of tungsten is 19.1 g / cm ³ . Although the specific gravity of tungsten is higher than that of carbon steel, the thickness of the neutron shield 5 can be reduced by about 20 Omm compared to the thickness of carbon steel. Therefore, the total weight of the nuclear fuel transport container in Case I is lighter than the total weight in Case I in a state where the spent fuel assemblies are not stored. The reduction in the total weight is equivalent to the spent nuclear fuel collection that can be stored in the nuclear fuel transport container in Case II. The number of storage units in the united unit can be increased to about twice the number of storage units in Case II. Ie, the case of using the neutron shielding body 5 constituted by inelastic scattering cross section is large tungsten neutron energy ^{^{1 0 5 ~ 1 0 7 e}} V region, use of carbon steel in place of the neutron shielding body 5 The number of spent nuclear fuel assemblies that can be stored in a nuclear fuel transport container can be doubled as compared with the case where This increases the transport efficiency of spent fuel assemblies.

Since the neutron shield 5 is located inside the neutron shield 7, the weight of the nuclear fuel transport container 1 is reduced. In other words, the neutron shielding body 5 requires a predetermined thickness as described above in order to shield any are arranged at positions 1 0 ⁵ ~ 1 0 ⁷ e V of E Nerugi one neutron be in the radial direction. For this reason, the weight of the neutron shield 5 decreases as the inner diameter of the neutron shield 5 decreases.

The tungsten constituting the neutron shield 5 is fragile, but is not scattered around because it is surrounded by the rigid first inner cylindrical body 4 and the second inner cylindrical body 6, so that the neutron shield 5 is formed. Demonstrate the function of. For example, when the neutron shield 5 is disposed outside the second inner cylindrical body 6, for example, between the second inner cylindrical body 6 and the neutron shield 7, the nuclear fuel transport container falls during transportation. When the outer cylindrical body 9 is damaged and the neutron shield 7 scatters outside, the neutron shield 5 may also scatter outside. Scattering to the outside of the neutron shielding body 7, in the nuclear fuel transport container 1, reducing the shielding ability against 10 ⁵ ~ 1 0 ⁷ e V energy neutrons. In the present embodiment, since the neutron shield 5 is disposed inside the second inner cylindrical body 6, such a decrease in the shielding ability can be prevented. Further, by providing the first inner cylindrical body 4, the neutron shield 5 can be annularly arranged with a substantially uniform thickness inside the second inner cylindrical body 6. The cross section of basket 3 is 7th It is square as shown in the figure. For this reason, when the first inner cylindrical body 4 is not provided, the neutron shield 5 is disposed between the second inner cylindrical body 6 and the basket 3. In this case, the radial thickness of the neutron shield 5 needs to satisfy the above-mentioned predetermined thickness at the position where the thickness is the smallest. Therefore, there are places where the thickness of the neutron shield 5 in the radial direction becomes unnecessarily thick, so that the weight of the nuclear fuel transport container increases.

The thickness of the first inner cylindrical body 4 in the radial direction is smaller than the thickness of the second inner cylindrical body 4 in the radial direction. For this reason, the inner diameter of the neutron shield 5 having a large specific gravity adjacent to the second inner cylindrical body 4 is reduced. This leads to a reduction in the weight of the neutron shield 5 and a reduction in the weight of the nuclear fuel transport container 1.

In this embodiment, since the container body 15 is double-sealed by the primary lid 11 and the secondary lid 13, the fuel rod cladding tube of the stored spent fuel assembly may be damaged by any chance. Also, radioactive materials in the fuel rods are not released out of the nuclear fuel transport container 1. Also, the neutron shield 10 in the primary lid 11 located inside, the neutron shield 12 in the secondary lid 13 located outside, the neutron shield 10 and the neutron shield 1 2 The primary lid 11 and the secondary lid 13 are compact, and their weights are reduced.

The neutron shields 5, 10 may be made of a tungsten alloy such as W—Fe and W—Pb, or a sintered body of tungsten, instead of metal tungsten. Further, the neutron shields 5, 10 may be made of gadolinium or manganese. Here, gadolinium is used in the form of a metal gadolinium, a gadolinium alloy such as Gd-Fe and Gd-Pb, or a sintered body of gadolinium. When manganese is used, the metal manganese, M n — Fe and M n — It takes the form of either a manganese alloy such as Pb or a sintered body of manganese. The neutron shield 5, 10 only needs to contain at least one of tungsten, gadolinium, and manganese.

Spent fuel assemblies generated from pressurized water reactors are also transported using nuclear fuel transport containers. The same structure as the nuclear fuel transport container 1 can be applied to this nuclear fuel transport container. However, the cross-sectional area of a spent fuel assembly generated from a pressurized water reactor is larger than that of a spent fuel assembly generated from a boiling water reactor. For this reason, the nuclear fuel transport container that stores the spent fuel assemblies generated from the pressurized water reactor has a cross-sectional area of the fuel storage space formed in the basket, and the spent fuel assemblies generated from the boiling water reactor Is larger than its cross-sectional area. The nuclear fuel transport container provided with the neutron shields 5 and 12 and storing the spent fuel assemblies generated from the pressurized water reactor can obtain the effects produced in the nuclear fuel transport container 1 described above. Nuclear fuel transport · Storage containers are used for transport and storage of spent fuel assemblies. The neutron shields 5, 12 used in the nuclear fuel transport container 1 can be applied to the nuclear fuel transport / storage container. The nuclear fuel transport and storage container to which the neutron shields 5 and 12 are applied has the structure of the nuclear fuel transport container 1. Nuclear fuel transport · Storage containers are also nuclear fuel transport containers. Industrial applicability

INDUSTRIAL APPLICABILITY The present invention is applied not only to a nuclear fuel transport container for storing a spent fuel assembly generated in a boiling water nuclear power plant, but also to a nuclear fuel transport container for storing a spent fuel assembly generated in a pressurized water nuclear power plant. It is possible. The present invention is also applicable to a nuclear fuel transport / storage container having a storage function.

Claims

The scope of the claims

1. A tubular body formed of any one of carbon steel and stainless steel and surrounding a plurality of spent fuel assemblies housed therein; and a tubular body provided adjacent to the tubular body, and A nuclear fuel transport container, comprising: a neutron shield composed of a material having a larger inelastic scattering cross-sectional area than a lamella.

2. A second neutron shield containing hydrogen is arranged in an annular shape, and an outer cylindrical body surrounding the outside of the second neutron shield arranged in an annular shape is provided, and the first neutron shield is the neutron shield. 2. The nuclear fuel transport container ff according to claim 1, wherein the body and the inner cylindrical body are disposed inside the second neutron shielding body.

3. The first neutron shielding ^{^{body, 1 0 5 ~ 1 0 7}} e V energy inelastic scattering cross section for neutrons of claim 1 greater than its non弹性scattering cross section of the tubular body of the Nuclear fuel transport container.

4. The nuclear fuel transport container according to claim 3, wherein the first neutron shield includes any of tungsten, gadolinium, and manganese.

5. The first cylindrical body that is made of either carbon steel or stainless steel and surrounds a plurality of spent fuel assemblies housed inside, and that is made of either carbon steel or stainless steel A second cylindrical body surrounding the first cylindrical body, and provided between the first cylindrical body and the second cylindrical body, and having a larger inelastic scattering cross-sectional area than the cylindrical body. A nuclear fuel transport container comprising a neutron shield made of a material.

6. The first cylindrical body, the second cylindrical body, and a first neutron shielding body that is the neutron shielding body provided between the first cylindrical body and the second cylindrical body, Located inside the second neutron shield arranged in a ring containing hydrogen 6. The nuclear fuel transport container according to claim 5, wherein an outer cylindrical body surrounding an outside of the second neutron shielding body arranged in an annular shape is provided.

7. The nuclear fuel transport container according to claim 5, wherein a thickness of the first cylindrical body in a radial direction is smaller than a thickness of the second cylindrical body in a radial direction.

8. The neutron shielding body, 1 0 ⁵ to 1 0 ⁷ nuclear fuel transportation large heard claim 5 than the inelastic scattering cross sections of the non弹性scattering cross section is the cylindrical body against the neutron energy e V container.

9. The nuclear fuel transport container according to claim 8, wherein the neutron shield includes any of tungsten, gadolinium, and manganese.

10. Constructed of either carbon steel or stainless steel and composed of the first tubular body surrounding multiple spent fuel assemblies contained inside, and composed of any of carbon steel and stainless steel A second tubular body surrounding the first tubular body, provided between the first tubular body and the second tubular body, and having a larger inelastic scattering cross-sectional area than the tubular body. A first neutron shield composed of a material, a second neutron shield containing hydrogen, which is annularly arranged around the second cylindrical body, and a second neutron shield which is annularly arranged. A container body having an outer cylindrical body surrounding the outer side;

A first metal portion made of any one of carbon steel and stainless steel; and a first metal portion provided inside the first metal portion and made of a material having a larger inelastic scattering cross-sectional area than the first metal portion. 3 having a neutron shield, a first lid attached to the container body,

A second metal part made of one of carbon steel and stainless steel, and a fourth neutron shield provided in the second metal part and containing hydrogen, the vessel covering the first lid and covering the first lid A nuclear fuel transport container equipped with a second lid attached to the main body.

1 1. The first neutron shielding ^{^{body, 1 0 5 ~ 1 0 7}} e inelastic scattering cross sections for the neutral terminal of the energy of the V is greater Ri by the inelastic scattering cross section of the tubular body, the first 3 neutron shielding body, 1 0 ⁵ ~ 1 0 ⁷ e inelastic scattering cross section nuclear fuel transportation according to claim 1 0 greater than its inelastic scattered Randan area of the first metal portion relative to the neutron energy one V container.

12. The nuclear fuel transport container according to claim 11, wherein the first neutron shield and the third neutron shield include any of tundane, gadolinium, and manganese.