RU2213382C1 - Conveyer for spent nuclear fuel transport and/or storage - Google Patents

Abstract

FIELD: mobile safety containers designed for transport and/or storage of spent nuclear fuel. SUBSTANCE: container designed for handling environmentally hazardous materials has body in the form of internal and external shells with insert in-between, as well as cover and bottom joined to body. Insert is made in the form of rolled flexible sheet material. Outer size of roll corresponds to that of internal shell and its inner size, to that of external shell. External and internal shells and insert are joined together. Proposed mechanical design of container makes it practically feasible, provides for dispensing with jointing unlike materials and for preventing throughout destruction of container in emergency situations. EFFECT: improved safety of environmentally hazardous wastes in transport and storage under impact loads and in emergency situations. 7 cl, 4 dwg

Description

 The invention relates to mobile protective containers and is intended for transportation and / or storage of spent nuclear fuel.

Known containers for transporting and storing spent nuclear fuel (SNF):
-TK-6 (transport kit) - for VVER-440 SNF;
-TK-8 - for RBMK-1000 SNF;
-TK-11 - for SNF BN-350 and BN-600;
-TK-13 - for VVER-1000 spent nuclear fuel;
-TK-18 - for SNF of power plants (Monthly Theoretical and Scientific-Technical Journal of the Ministry of the Russian Federation for Atomic Energy of the Nuclear Society of Russia and the Russian Academy of Sciences, "Atomic Energy", Volume 89, Issue 4, October 2000, pp. 273-284 , "Long-term storage and transportation of spent nuclear fuel").

 In the design of the cases of the above containers, expensive, thick-walled (up to 350 mm) forgings are used, made of corrosion-resistant austenitic steel. The production of such containers is expensive, complex and low-tech. However, it can be noted that these shopping malls were created in 1983-1991. and their service life of 20 years will expire in 2011, while decommissioning of power units will occur approximately from 2010 to 2030, but the design of the fuel cell is morally obsolete, and the capacity is not optimal. In this regard, it will be necessary to replace the fleet of vehicles with a new one.

TK are known for transportation and long-term storage of spent nuclear fuel:
- metal containers CASTOR company GNB, Germany, with a body cast from special malleable cast iron with spherical graphite (Radiochemical processing of nuclear fuel of nuclear power plants. M: Energoizdat, 1983, p.33-43, section "Transportation of spent fuel".).

 These TCs are technologically advanced to manufacture and relatively cheap, however, they do not have the necessary crack resistance under the conditions of their operation. In addition, these containers are not suitable for long SNF.

 Known container for transportation and / or storage of spent nuclear fuel containing the outer and inner shells. The outer shell in it is a damping casing of detachable elements, the latter being made in the form of a drum with end walls and a shell, including central and end elements. At each end wall of the casing inside the latter there are installed radially arranged tubular elements fastened to the end element of the shell and to each other, and along the generatrix of each end element of the shell installed other tubular elements fastened to the end element of the shell and to each other. The tubular elements are filled with cement-sand concrete (RF patent 2105364, G 21 F 5/008, publ. 02.20.98). In such a container, damping elements create a sufficiently high impact resistance in emergency situations.

 But the need for additional protection of the inner container of the container leads to a significant increase in the cost of the entire structure of the container.

 A container for transporting and / or storing spent nuclear fuel is known, containing metallic outer and inner cylindrical shells with bottoms, the cavity between which is filled with heavy concrete, and an airtight ceiling. Hermetic overlap is made in the form of two covers installed one above the other on a common base and forming two concentric sealing circuits with the latter. Inside the concrete aggregate (insert) with a gap relative to the outer cylindrical shell, a reinforcement is placed in the form of a lattice consisting of ring and longitudinal elements connected to the bottom of the outer shell, and the base of the covers, between the lattice and the inner cylindrical shell with a gap relative to the latter, a shielding power cup is installed, connected to the base of the covers and connected to the grill by rods (RF patent 2084975, G 21 F 5/008, publ. 07.20.97). This container is closest in essential features to the proposed one and is selected as a prototype.

The disadvantages of the container are:
- low technological design;
- low reliability: in a container with monolithic walls in emergency situations, the crack propagates immediately over the entire wall thickness, the destruction is catastrophic, since the energy released during a very short period of time gives the destruction the character of a dangerous explosion;
- the need to remove hydrogen from the container body, resulting from the radiolysis of water bound in concrete, which leads to a weakening of the strength, resistance, protective characteristics of concrete and, accordingly, may not provide long-term guaranteed safe transportation and storage of spent nuclear fuel;
- the impossibility of creating a metal-concrete container with a length of more than 10 m, while for some types of spent nuclear fuel a longer container is required.

 Thus, the object of the present invention is to provide a more technologically advanced container design, which provides increased reliability of protection of environmentally hazardous cargo from shock loads during transportation, storage, in emergency situations.

 The technical result consists in eliminating the need to connect dissimilar materials, in preventing catastrophic through destruction of the container walls as a result of external influences.

 To solve this problem, a container for transportation and / or storage of spent nuclear fuel is proposed, comprising a housing in the form of outer and inner shells, an insert located between them, a lid and a bottom connected to the housing. According to the invention, the insert is made in the form of a roll of flexible sheet material with an inner roll size corresponding to the outer dimension of the inner shell, and the outer dimension to the inner size of the outer shell, while the outer and inner shells and the insert are interconnected.

 In this case, the insert is equipped with two wedge elements, fixed at the ends of the sheet forming a roll and bent until locked into a cylindrical surface of the roll.

 The most technologically advanced connection of shells and inserts on the surface of wedge elements.

 The housing can be made of separate sections, rigidly and hermetically connected along the end surfaces to each other. This will allow producing containers for containers without length restrictions for any type of SNF.

 In this case, the container is equipped with a flange for attaching the lid, rigidly and hermetically connected to the end surface of the housing.

 The outer surface of the outer shell may be made in the form of a bimetallic sheet with an outer layer of stainless steel followed by corrosion-resistant surfacing.

 An anticorrosive coating is applied to the outer surface of the cover, flange and bottom.

 The proposed container for transportation and storage of spent nuclear fuel is illustrated by the drawings shown in figures 1,2,3,4.

Figure 1 shows a container for transporting and / or storage of spent nuclear fuel;
figure 2 - multi-section container for transportation and / or storage of spent nuclear fuel;
figure 3 - section aa, the design of the elements of the rolled shell;
figure 4 is a wedge element, item 7 in figure 3.

 The container for transporting and / or storage of spent nuclear fuel (Fig. 1) contains a housing 1 in the form of an outer 2 and an inner 3 shell (Fig. 3), an insert 4 located between them, a cover 5 and a bottom 6 (Fig. 1). The connection of the housing 1 with the bottom 6 is carried out by welding. Insert 4 (figure 3) is made in the form of a roll of flexible sheet material. The outer dimension of the insert 4 corresponds to the inner dimension of the outer shell 2, and the inner dimension corresponds to the outer dimension of the inner shell 3. The inner shell 3 (Fig. 3) is rolled from a sheet stock with a thickness of 10 to 20 mm, after rolling, longitudinal welds are welded. To obtain the correct concentric shape on the inner shell 3, a wedge element 7 is installed (figure 4). The wedge element 7 is made mechanically with dimensions: a width (around the circumference of the shell) of at least 300 mm; length - the entire length of the shell; the thickness of the thin end is not more than 0.3 mm, the thickness of the opposite end must be equal to the thickness of the rolled steel. The wedge element 7 is attached to the inner shell 3 by welding. Further, on the inner shell 3 with the wedge element 7 (Fig. 3), a steel roll tape is spirally wound, with a width of 1400 to 1700 mm, a thickness of 2 to 5 mm. The winding of the roll tape is carried out continuously to the specified thickness of the insert 4. The thickness of the insert 4 is determined in each case and for a specific type of fuel, for example: if the fuel holding time in the reactor pools is less than 8-10 years, then the thickness of the insert 4 will be about 300 mm. In addition, on the outer surface of the housing, it is possible to install a casing (not shown in the drawings) that plays the role of neutron protection; if the fuel holding time is more than 10 years, then the thickness of insert 4 will be less than 300 mm. The end of the roll tape (Fig. 3) is welded to the underlying coil. Then, the closing wedge element 7 is welded to the insert 4 and the outer shell 2 is installed. The outer shell 2 is made of a two-layer sheet 10 mm thick with the outer sheet of stainless steel, which provides reliable protection of the outer surface of the housing as a result of external influences. The fastening of the outer shell 2 with the wedge element 7 is carried out by welding. The quality of all welds is monitored. To protect against corrosion, the outer surface of the joints is covered with a corrosion-resistant facing layer. All surfaces of the container are cleaned to the required cleanliness.

 Case 1 can be made of separate sections, rigidly and hermetically connected along end surfaces to each other, which allows the use of spent nuclear fuel of any length, for example: for nuclear submarines (nuclear submarines) BN-350, the length of spent nuclear fuel is 3.5 m, the container is assembled from 2 sections; for VVER-440, VVER-1000, the SNF length is 4-5 m, the container is assembled from 3 sections; for RBMK-1000, the SNF length is 10 m, the container is assembled from 7 sections; for AMB, the SNF length is from 13 to 14.5 m, the container is assembled from 10-11 sections.

 The container is equipped with a flange 8 for attaching the cover 5, rigidly and hermetically connected to the end surface of the housing.

 An anti-corrosion coating is applied to the outer surfaces of the cover, flange and bottom to ensure corrosion resistance.

 Spiral-wound gaskets (SNP) OST 26.260.454-93 are used to seal structural joints, which withstand high temperatures in a fire and are resistant to ionizing radiation. Structurally, SNPs are ring-shaped and wound from two spiral alternating tapes - profiled cold-rolled corrosion-resistant steel tape and graphite foil "Graflex" TU 57-1-1326778-92.

 The elements of the container have rather simple forms, and their production does not cause difficulties, large bending, pressing and thermal equipment are freed.

 A container made in this way for the transportation and / or storage of SNF is ready for the transport of environmentally hazardous cargo and long-term storage (50 years).

 Consider an emergency option.

 As a result of external impact on the SNF container during transportation and / or storage, cracking of the outer shell 2 occurs, but the multilayer design of the insert 4 localizes the propagation of cracks, restricting it to nearby layers, and does not go to the lower layers and the inner shell 3, thereby not destroying the entire container construction thickness. For further crack propagation, a new impulse is needed, i.e. new external impact.

 The container for transportation and / or long-term storage of spent nuclear fuel has passed the entire range of tests and has maintained its operability and tightness. Tests of the container confirmed the validity of the use of an insert in the form of a roll of flexible sheet material, which ensures reliable protection of environmentally hazardous cargo from the effects of shock loads during transportation, long-term storage, in emergency situations.

Claims (7)

 1. A container for transporting and / or storage of spent nuclear fuel, comprising a housing in the form of coaxially arranged outer and inner shells connected to the bottom, and a lid, characterized in that the space between the shells is filled with a roll of flexible sheet material.  2. The container according to claim 1, characterized in that the roll is equipped with two wedge elements fixed at the ends of the sheet forming the roll and bent until locked into the cylindrical surface of the roll.  3. The container according to claim 1 or 2, characterized in that the rigid connection of the shells and the insert is made on the surface of the wedge elements.  4. The container according to any one of paragraphs. 1-3, characterized in that the housing is made of separate sections, rigidly and hermetically connected along the end surfaces to each other.  5. The container according to any one of paragraphs. 1-4, characterized in that it is equipped with a flange for attaching the cover, rigidly and hermetically connected to the end surface of the housing.  6. The container according to any one of paragraphs. 1-5, characterized in that the outer surface of the outer shell is made in the form of a bimetallic sheet with an outer layer of stainless steel.  7. The container according to any one of paragraphs. 1-6, characterized in that on the outer surface of the cover, flange and bottom is applied anti-corrosion coating.

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