RU2582083C2 - Method for producing container for transportation and storage of spent nuclear fuel - Google Patents

Abstract

FIELD: nuclear energy.

SUBSTANCE: invention relates to nuclear power engineering. Method of producing container for transportation and storage of spent nuclear fuel includes manufacturing of container body. Formed cavity is filled with neutron-protective material. In mold inner part of container housing is installed cylinder. External part of body is attached to its inner bimetallic part by shrinkage. Shrinkage occurs during solidification of liquid metal (molten iron), heat sink elements are clamped (cast) between outer surface of inner housing and inner part of outer surface of housing.

EFFECT: invention improves manufacturability of container, reduce human and financial costs of its production.

1 cl, 4 dwg

Description

The invention can be used in nuclear energy in the manufacture of containers for transporting and storing spent nuclear fuel and other radioactive materials.

A device, system and method for storing high-level waste (Apparatus, system and method for storing high level waste) [1], in the manufacture of which between its inner and outer shells are placed ring elements that form a single batch structure, which ensures the relative position of the inner and outer shells and heat removal from the inner shell. In the voids of the ring structures collected in a package, a neutron-absorbing material is placed.

A disadvantage of the manufacturing technology of the known device is the complexity of forming a batch structure of ring elements located between the inner and outer shells.

A known method of manufacturing a container for radioactive materials, using which the container [2] contains a casing (bimetallic body) cast from cast iron or steel and a shielding material. In the manufacture of the container, the shielding material is placed inside the casting mold for the casing, followed by pouring, for example, cast iron, into said casting mold. Thus, a cast bimetallic casing is obtained in which the shielding material is already “immersed” in the array of the side wall of the casing and occupies the required position. On the outside of the container body, longitudinal finning is performed to remove heat (cooling fins). In another embodiment, a molded case is placed inside an annular casing, which is two concentric metal shells, the gap between which is filled with a shielding material. At the same time, heat-removing elements installed in the molded body array are passed through the shielding material, attached (welded) to the said shells, respectively, and protruding outward beyond the outer shell. The heat-removing elements are made in the form of radial longitudinal sheet elements.

The disadvantage of the method of manufacturing a known container is that it involves the high complexity of manufacturing the container and, therefore, its high cost.

A known method of manufacturing containers of the CASTOR type (for example, CASTOR V / 52, CASTOR V / 21A, CASTOR V / 19, CASTOR HAW 20/28 CG) developed by Gesellschaft fur Nuklear - Service mbH (GNS) and Gesellschaft für Nuklear - Beh ä lter mbH (GNB) (Germany) [3] the cases of which are made monolithic of high-strength cast iron with spherical graphite (VChShG). The weight of the casting of the container body is more than 140 tons, the wall thickness is more than 450 mm. A system of longitudinal axial channels (usually of circular cross section) designed to be filled with neutron-protective material is implemented in the walls of the containers of CASTOR containers. The channels are made with a diameter of 60-80 mm to the depth of the working part of the body by machining in two diameters with an offset to prevent a "direct backbone" of neutrons. The distance between the channels is 30-40 mm.

The disadvantages of the known method of manufacturing containers are:

1. Organizational and technical difficulties in the manufacture of castings weighing more than 140 tons, since the known modifiers guarantee the necessary shape and size of graphite in the body of the casting and, as a result, the specified mechanical properties for no more than 30 minutes from the start of the release of metal from furnaces to the end of the fill form. The ability to fill at a given time have individual foundries in the world.

2. For the manufacture of channels serving to accommodate neutron protection, the use of unique highly specialized expensive equipment is required.

The closest set of essential features to the claimed method of manufacturing a container for transporting and storing spent nuclear fuel is the method used in the manufacture of a container known from the prior art for transporting and / or storing spent nuclear fuel [4], in the manufacture of which the outer and inner glasses, in the cavity formed between which heat-removing elements are placed, and the free space is filled radiation protective material. The end surfaces of the outer glass are equipped with shock absorbers in the form of protrusions of one and a half shapes. The heat-removing elements are made in the form of metal jumpers of a certain size, located between the outer and inner glasses of the container. The design feature of the container is that the inner cup, outer cup and heat sink elements are a monolith made of a cast alloy of ferritic high-strength cast iron.

The disadvantages of the manufacturing technology of the known container include the complexity of manufacturing a monolithic container body from ductile iron. This drawback is, in particular, due to the difficulty of providing a sufficiently high cooling rate of thick-walled castings throughout the thickness to ensure the formation of the necessary cast iron structure.

The technical result from the application of the proposed method of manufacturing a container for transportation and storage of spent nuclear fuel is to increase the manufacturability of the container for transportation and storage of spent nuclear fuel, reducing labor and financial costs for its manufacture.

The technical result is achieved by the fact that a cylinder made of stainless steel and heat-removing elements with devices for their preservation when interacting with a high-strength cast iron melt with spherical graphite filling the mold are installed in the mold of the container’s inner part, so that when the high-strength melt cools down cast iron with spherical graphite filling the indicated mold; a cylinder made of stainless steel turned out to be connected to the casting internally part of the body due to shrinkage occurring during crystallization of liquid ductile iron with spherical graphite, and the heat-removing elements at one end turned out to be poured into the outer surface of the casting of the inner part of the container body, then the casting mold is filled with high-strength cast iron with spherical graphite, after cooling the casting, knock out cleaning and cutting the profits of casting the inner part of the body, then collect the mold intended for the formation of the outer part of the body, in prices where the casting of the inner part of the casing is installed vertically with the profitable part downward, while the outer surface of the casting of the inner part is encapsulated with the molding mixture, thereby forming the shape of the inner surface of the casting of the outer part of the casing so that the heat-removing elements are poured into its outer surface with one end and the other end protruded beyond the moldable mixture, and the inner part of the body served as a core in the specified casting mold, then cast-iron chill molds are installed, forming the surface of the casting of the container body, on top of the chill mold is closed with a cast iron lid forming the bottom of the casting of the container body, then the specified casting mold is poured with a melt of ductile iron with spherical graphite, after cooling the casting, the casting mold is disassembled, and the resulting container body, in which it is internal and external parts are interconnected in the required mutual position due to shrinkage of ductile iron with spherical graphite, there is a dense abutment the surface of the casting of the inner part of the casting of the body to the inner surface of the outer part of the casting of the container body, after cooling, the casting of the container body is directed to machining, the free space between the inner and outer parts of the body is filled with neutron-protective material through the holes in the bottom of the outer part of the body, to the outer part of the body from the bottom of the set plate.

Figure 1 presents the casting of the inner bimetallic part of the container body for transportation and storage of spent nuclear fuel.

Figure 2 presents the trimetallic casting of the container body for transportation and storage of spent nuclear fuel.

Figure 3 shows a section aa of the container body for transporting and storing spent nuclear fuel.

Figure 4 shows a section bB of the container for transportation and storage of spent nuclear fuel.

The method provides the manufacture of a container for transportation and storage of spent nuclear fuel, which includes a trimetallic housing formed by an internal bimetallic (Fig. 1) and external 1 parts interconnected due to shrinkage occurring during crystallization of a melt of ductile iron with spherical graphite, and also heat-releasing elements 8 located between the outer surface of the inner bimetallic and the inner surface of the outer 1 parts of the housing.

According to the proposed method of manufacturing a container for transporting and storing spent nuclear fuel, the container body is made of high-strength cast iron with spherical graphite by two fillings. For pouring, a rain gating system is used.

At the first casting, a casting of the inside of the body is made. In the manufacture of the mold of the inner part of the housing, a cylinder 5 is made in it, made of stainless steel and forming the inner part of the casting of the inner part of the housing. The outer surface of the casting of the inner part of the body is formed by 4-5 cores installed in the mold.

Heat-releasing elements 8 are installed in the rods, having a curved shape and made of a material with high thermal conductivity, such as copper, and with the implementation of protective measures to protect them when interacting with the melt of high-strength cast iron with spherical graphite filling the mold so that after cooling the casting the heat-removing elements 8 with one end turned out to be poured into the outer surface of the casting of the inner part of the housing.

As measures for protecting the heat-removing elements 8 from changing a given shape when exposed to high temperature due to the interaction with the melt of high-strength cast iron with spherical graphite, devices in the form of protective cases made of X18H9T steel can be used, in which heat-removing elements 8 are placed.

To compensate for the thermal expansion of the heat-removing elements 8 and the cylinder 5 in the mold, there are height gaps.

After cooling the casting of the inner part of the casing, the heat-removing elements 8 made of copper turn out to be poured into the outer surface of the casting of the inner part of the casing, and the cylinder 5 made of stainless steel is connected to the casting of the inner part of the casing due to the shrinkage that occurs during the crystallization of high-strength liquid nodular cast iron as the casting of the inside of the body cools.

After knocking out, cleaning and cutting profit margins, casting the inside of the body is used in the second casting.

During the second pouring into the mold, casting of the inner part of the body with the profitable part 16 down with the space filled with the rod mixture between the heat-removing elements 8 is established and forms the inner surface of the casting of the container body. The outer surface of the casting of the container body is formed by cast iron molds installed in the mold. On top of the chill mold is closed with a cast-iron lid forming the bottom of the container body casting.

This casting is to be filled with ductile iron with spherical graphite.

When cooling the melt of nodular cast iron, the seat belts 11, 12 of the outer part 1 are tightly adjoined to the seat belts 9, 10 of the inner bimetallic part, due to which there is a reliable fixation of the inner bimetallic and outer 1 parts of the housing relative to each other in the required relative position. When this heat-removing elements 8 are poured between the outer surface of the inner bimetallic part of the housing and the inner surface of the outer part 1 of the housing.

After cooling the casting of the container body, said mold is disassembled, the resulting container body is sent for mechanical processing.

In the manufacture of the container body, it is possible to install cylinder 5 in the casting of the container body by hot press fit at the stage of its cooling at a temperature of 150-200 ° C, as well as the manufacture of the inner part (Fig. 1) of the body without cylinder 5 and bottom 13 made of stainless steel , while providing a corrosion-resistant coating of the inner surface of the inner part of the housing by another method.

In the resulting container body for transportation and storage of spent nuclear fuel, the free space 15 between the inner and outer parts of the body through the holes in the bottom of the outer part 1 of the body is filled with neutron-protective material, and a plate 7 is installed on the surface of the bottom of the outer part 1. In this case, the space between the plate 7 and the bottom surface of the outer part of the container body for transporting and storing spent nuclear fuel is filled with a neutron-protective material.

With this method of manufacturing a container for transporting and storing spent nuclear fuel, its inner bimetallic part is cast from ductile iron with spherical graphite and has the shape of a cylinder with landing belts made on the outer surface in its upper part 9 and lower part 10 by machining the casting inside which is located cylinder 5, equipped with a bottom 13 installed during assembly of the housing, made, for example, of stainless steel. Stainless steel provides a corrosion-resistant coating on the inside of the container body.

The outer part 1 of the housing of the proposed device is also cast from high-strength cast iron with spherical graphite and has the form of a glass with internal landing belts located in the upper 11 and lower 12 parts of the housing and mating with the landing belts 9, 10 of the inner bimetallic part. The outer part 1 has a bottom (figure 3) with through holes located opposite the cavity formed in the manufacture of a container for transporting and storing spent nuclear fuel between the outer surface of the inner bimetallic part and the inner surface of the outer part 1 when assembling the trimetallic body. Through these openings in the bottom of the outer part 12, the above cavity is filled between the inner and outer 1 parts of the casing with a neutron-protective material. On the outer surface of the bottom of the outer part 1, a plate 7 of a corresponding shape is installed, made, for example, of stainless steel and acting as a cover for holes in the bottom of the outer 1 part of the housing.

On the outer part 1 of the casing, load gripping pins 14 are provided, which make it possible to move and tilt the container for transporting and storing spent nuclear fuel, as well as transverse cooling fins 6 obtained by turning, providing good heat transfer from the casing to the environment.

The double tightness barrier of the container for transportation and storage of spent nuclear fuel is ensured by the fact that a hermetically sealed lid 2 is installed on the inner bimetallic part, which has the shape of a cylinder, and a hermetically sealed lid 3 is installed on the outer part 1.

To provide protection against neutron radiation, the inner space between the covers 2 and 3 is filled with solid neutron-protective material 4.

The heat-releasing elements 8 are made in the form of curved plates to prevent the "direct shot" of neutrons. At the same time, the heat-removing elements of the container for transportation and storage of spent nuclear fuel are made up of 4-5 parts with thermal gaps.

For the safe transportation of spent nuclear fuel on the outer surface of the container for transporting and storing spent nuclear fuel, damping devices are installed (not shown in Fig.), Which serve to protect the environmentally hazardous cargo inside the container from damage due to impact loads when not handled carefully, as well as emergency situations.

Due to the novelty of the proposed method of manufacturing a container for transporting and storing spent nuclear fuel, its manufacturability is improved while reducing financial and labor costs by simplifying the design of the connection of the external and internal bimetallic parts of the housing while ensuring their reliable fixation relative to each other, as well as eliminating the need for special labor-intensive operations for installing heat-releasing elements 8 while ensuring their reliable contact with body parts s along their sealing surfaces, thus increasing heat transfer.

The total weight of a set of castings from VChShG calculated for a reactor of the VVR-1000 type will be no more than 120 tons with a cavity width for neutron protection of 100 mm. The maximum weight of the largest casting will not exceed 90 tons, and the wall thickness of the castings will be less than 300 mm (in comparison with the analogue, the weight of the cast casting, the weight of the container body is more than 140 tons and the wall thickness is more than 450 mm)

The proposed invention:

a) increases the level of mechanical properties of castings. According to the Federal Institute for Materials Research and Testing (VAM of Germany), the relative elongation will be at least 16%, which cannot be achieved in the well-known container body designs, in which the elongation is at least 12% due to the large wall thickness,

b) reduces the level of organizational and technical requirements for manufacturers of cast iron container bodies for transportation and storage of spent nuclear fuel in connection with the reduction in the weight of a single-use casting from 140 tons to 90 tons.

c) the heat-removing elements poured into the walls of the inner and outer parts of the castings of the container body form the best contact in comparison with the presented analogues.

g) a corrosion-resistant coating of the inner part of the container body in the form of a cylinder 5 of stainless steel is formed at the stage of manufacturing the casting.

1. Patent WO 2008005932, IPC G21C 19/02, priority 2006

2. Patent EP 0116412A1, IPC G21F 5/00, priority 1984.

3. Kalinkin V.I. et al. Storage of spent nuclear fuel from power reactors. - SPb., 2009, p. 44-50.

4. Patent for utility model RU 9998 U1, IPC G21F 5/008, 1999 priority.

Claims (1)

A method of manufacturing a container for transporting and storing spent nuclear fuel, comprising manufacturing a container body formed by the inner bimetallic and external cast iron parts of the body, placing heat-removing elements between them, filling the cavities formed with a neutron-protective material, characterized in that the mold is the inner part of the container body a cylinder made of stainless steel is installed, and heat-removing elements with devices for their preservation during interchange operation with the melt of ductile iron with spherical graphite filling the mold, so that when cooling the melt of ductile iron with spherical graphite filling the specified mold, the stainless steel cylinder is connected to the casting of the inner part of the body due to shrinkage occurring during crystallization of liquid ductile iron with spherical graphite, and the heat-removing elements with one end turned out to be poured into the outer surface of the casting of the inner part of the container body, then the casting mold is cast with high-strength cast iron with spherical graphite, after cooling the casting, the inner part of the body is knocked out, cleaned and profit cut, then the mold is assembled to form the outer part of the body, in the center of which the casting of the inner part of the body is installed vertically profitable part down, while the outer surface of the casting of the inner part is covered with a molding mixture, thereby forming the shape of the inner surface and casting the outer part of the body in such a way that the heat-releasing elements, poured into the outer surface with one end, and the other end protrude beyond the moldable mixture, and the inner part of the body acted as a rod in the specified casting mold, then cast iron molds forming the outer surface of the body casting are installed container, on top of the chill mold is closed with a cast-iron lid forming the bottom of the container body casting, then the specified casting mold is filled with a melt of high-strength cast iron with spherical graphite, after cooling the casting, the specified casting mold is disassembled and the container body obtained, in which its inner and outer parts are interconnected in the required relative position due to the shrinkage of high-strength cast iron with spherical graphite, the outer surface of the casting is closely adjoined to the casting the inner surface of the outer part of the container body casting, after cooling, the container body casting is sent for machining, freely e the space between the inner and outer parts of the body through the holes in the bottom of the outer part of the body is filled with neutron-protective material, on the outside of the body from the bottom of the set plate.

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