RU153580U1 - SPARE NUCLEAR FUEL COVER - Google Patents

Abstract

1. A cover for spent nuclear fuel, comprising a base fixed to the base of a central strut with alternating spacing elements located on it made of a material with high thermal conductivity - aluminum in the form of a disk with a central sleeve and spacer elements made of stainless steel, and pipes for placement of spent fuel assemblies, characterized in that the spacer elements of aluminum are made of separate segments, fastened together by a lock compounds of the inner and outer diametram.2. A cover according to claim 1, characterized in that the locking connection is made in the form of a protrusion-groove connection. 3. A cover according to claim 1, characterized in that the segments of the spacing elements are made of aluminum by precision casting, or by stamping, or by cutting from sheet metal by the hydroabrasive method.

Description

The utility model relates to nuclear energy, to devices for handling spent nuclear fuel (SNF) of nuclear power plants (NPPs), mainly VVER-1000 reactors, research reactors (IR) and ship installations in the form of spent fuel assemblies (FAs) and can be used for placement in a container during their transportation and / or storage,

Since during the transportation and storage of spent fuel assemblies there is a risk of an uncontrolled spontaneous chain reaction of fission of nuclei, which is accompanied by the release of significant energy up to the occurrence of a thermal explosion, the handling of radioactive materials having a high residual heat release places high demands on the prevention of overheating and ensuring efficient heat dissipation.

The heat generated inside the packaging container for the heat-generating radioactive material is removed based on natural physical processes of heat transfer, such as natural convection, radiant heat transfer, thermal conductivity of structural elements and more.

The placement and transportation of spent nuclear fuel in the form of fuel assemblies is carried out in a case installed in a transport container.

Known cover for spent assemblies of a nuclear reactor according to patent SU 1445449, G21C 19/07, publ. 1995.12.10, comprising a base with sockets, a central rack fixed to the base with a grip device, lattice spacers and an end piece mounted on a central rack, having sockets in the form of open U-shaped grooves, and tubular channels installed in the sockets for spent assemblies equipped with flanges fixed to the upper part with load gripping devices, and each groove of the end part is equipped with a rotary shutter.

Known cover for spent nuclear fuel according to patent RU No. 78979, G21F 5/012, containing a base fixed to the base of the Central rack with spacing elements located on it made of plates with high thermal conductivity and provided with holes that form channels for accommodating spent fuel assemblies and heat-separating inserts mounted on a central rack between the spacing elements and rigidly connecting them in the axial direction.

A disadvantage of the known cover is the restriction on permissible mechanical loads on the cover due to the insignificant strength characteristics of the plates made of materials with high thermal conductivity, for example, aluminum.

Known case for the placement and storage of spent fuel assemblies of the VVER-1000 reactor of the Russian Federation No. 1653456 publ. 1996.12.10, made of stainless steel and containing a central pipe, spacer elements in the form of partitions, which have openings for installing twelve hexagonal pipes to accommodate spent fuel assemblies in them, and the pipe axes are located at points with certain polar coordinates.

A disadvantage of the known cover is the restriction on the allowable thermal load on the package design due to insufficient heat removal.

The container cover for SNF transportation should have the following main functions:

- mechanical strength, ensuring the preservation of the integrity of the geometric shape in normal and emergency conditions of transportation, which ensures the preservation of control over the criticality of the mass of nuclear material in these conditions;

- heat dissipation created by materials placed in the case.

The heat generated in the fuel elements of spent fuel assemblies is transferred to the container body due to the thermal conductivity of the structural elements of the cover (spacer elements in the form of disks), where, in turn, it is removed to the outer surface of the housing and to the atmosphere.

To effectively remove heat, it is rational to use elements from a material that conducts heat well, such as aluminum, copper and alloys of aluminum and copper, together with elements from a structural material (stainless steel) to provide mechanical strength. That is, for example, spacers with the same geometric dimensions and shape are made of different materials and placed alternately along the length of the cover in order to create a sequence of components, each of which performs at least one of these functions.

The closest technical solution to the claimed is a patent for utility model No. 140520, op. 05/10/2014 A “cover for spent nuclear fuel”, comprising a base fixed to a base of a central strut with spacing elements located thereon, and pipes for accommodating spent fuel assemblies, with alternating spacing elements in the form of a disk with a central hub and located on the central strut outer shell made of material with high thermal conductivity and spacers made of stainless steel. Nuclear safety tubes made of boron-containing steel are installed in channels formed by round or hexagonal holes in the spacer elements.

Remote heat-removing elements with high thermal conductivity have a complex configuration - they must have six or more hexagonal or round holes with high accuracy for the installation of hexagonal pipes for fuel assemblies, they are made of aluminum, and today they make up a significant amount of costs in the manufacture of a cover, t. to. made from a single piece of forged aluminum, followed by machining, in which the waste makes up more than 80% of the metal. Currently, there are no other manufacturing technologies to eliminate these shortcomings.

In order to significantly reduce the manufacturing cost of this element, reduce metal consumption, manufacturing complexity, reduce manufacturing time and improve manufacturability, it is proposed to change the design of the specified spacing element, which will allow the use of more modern low-waste technologies.

Thus, the technical result is to reduce metal consumption, the complexity of manufacturing and reduce the cost of manufacturing a cover while maintaining effective heat removal from spent fuel assemblies.

The specified technical result is achieved by the fact that the proposed cover for spent nuclear fuel, containing a base fixed to the base of the Central rack with alternating spacing elements located on it made of a material with high thermal conductivity - aluminum in the form of a disk with a Central sleeve, and spacing elements made stainless steel, and pipes for the placement of spent fuel assemblies, while the spacer elements of aluminum are made of nyh segments fastened together interlocks the inner and outer diameter.

In this case, the locking connection is made in the form of a protrusion-groove connection.

In this case, the segments of the spacing elements are made of aluminum by precision casting, or by stamping, or by cutting from sheet metal by the hydroabrasive method.

The essence of the utility model is illustrated in the drawing.

The figure 1 shows a cover for spent nuclear fuel containing a base 1, a central rack 2, alternating spacers 3 made of a material with high thermal conductivity - aluminum and spacers 4 made in the form of stainless steel disks, boron tubes 5 for spent fuel assemblies, installed in the holes of the distance elements. The distance elements 3 and 4 are mounted on the central rack 2.

The elements of the cover 4 made of stainless steel provide mechanical strength.

Pipes made of boron-containing steel are installed in the channels formed, for example, by round or hexagonal holes in the spacers 3 and 4 to ensure nuclear safety. The central rack 2 of the cover can be equipped with a device for capture.

The figure 2 shows the spacer element 3 made of a material with high thermal conductivity of aluminum and representing a disk of variable thickness with a Central sleeve.

Structurally, the sleeve provides the installation of the disk on the Central rack, and functionally designed for heat transfer in the axial direction, i.e. along the central pillar.

In FIG. 3-5, a spacer element 3 of aluminum is shown, which is a disk consisting of individual segments 6 (Fig. 4), interconnected by locking joints (Fig. 5) along the outer and inner diameters. As a specific embodiment, a spacer element 3 is shown, made of 6 segments with hexagonal holes for accommodating hexagonal boron tubes for fuel assemblies.

Segments 6 are interconnected by locking joints, which can be made in the form of a protrusion-groove connection.

Separate segments of the spacing aluminum disk allow them to be made with higher accuracy than in the prototype, for example,

- injection molding under high or low pressure;

- hot stamping;

- cutting blanks of parts from sheet metal by a hydroabrasive method.

Prepared composite disc segments require minimal subsequent machining of the assembled disc.

The assembly of the finished segments 6 is carried out using lock joints on the outer and inner diameters of each segment. As an option, the protrusion-groove connection is shown. That is, a protrusion made on the outer and inner diameter of the previous segment is included in the groove of the subsequent segment. The assembled disk element is mounted on the central rack 2.

According to preliminary estimates, the cost of manufacturing an AK 8 TOST 190073-85 aluminum spacer heat sink disk of the proposed design by injection molding should be reduced by 1.5-2 times compared with the prototype - a solid forged disk of a similar size.

Thus, the proposed design of the spacer element from a material with high thermal conductivity for the case for spent fuel assemblies will reduce the amount of metal, expand the technological capabilities of manufacturing, while maintaining the efficiency of heat dissipation.

Claims (3)

1. A cover for spent nuclear fuel, comprising a base fixed to the base of a central strut with alternating spacing elements located on it made of a material with high thermal conductivity - aluminum in the form of a disk with a central sleeve and spacer elements made of stainless steel, and pipes for placement of spent fuel assemblies, characterized in that the spacer elements of aluminum are made of separate segments, fastened together by a lock compounds of the inner and outer diameters. 2. A case according to claim 1, characterized in that the locking connection is made in the form of a protrusion-groove connection. 3. The case according to claim 1, characterized in that the segments of the spacing elements are made of aluminum by precision casting, or by stamping, or by cutting from sheet metal by the hydroabrasive method.

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