WO2022081039A1

WO2022081039A1 - Basket of a transportation packaging system for spent fuel assemblies

Info

Publication number: WO2022081039A1
Application number: PCT/RU2020/000669
Authority: WO
Inventors: Лев Николаевич КОЖАЕВ; Илья Алексеевич БАРЧЕНКОВ; Владимир Иванович КЕЧИН; Евгений Григорьевич КУДЕЛЬНИК; Александр Викторович ВИНОГРАДОВ; Олег Сергеевич АБРАШКИН; Андрей Николаевич КАРЛЫШКИН; Сергей Сергеевич КУКАНОВ; Сергей Юрьевич ГУЛАКОВ; Мария Юрьевна ИОНОВА
Priority date: 2020-10-15
Filing date: 2020-12-08
Publication date: 2022-04-21
Also published as: HUP2300028A1; WO2022081039A8; RU2743788C1

Abstract

The invention relates to nuclear engineering, in particular to devices for handling spent nuclear fuel (SNF) in nuclear power plants (NPPs) in the form of spent fuel assemblies (SFAs) and can be used for receiving same inside a container during transportation and/or storage. A basket for a transportation packaging system containing spent fuel assemblies comprises a base, a central tube and sectioned disks with openings in which solid hexagonal tubes are mounted in two annular rows relative to the axis of the basket for receiving SFAs. The composite central tube of the basket is made of heat-removing inserts. Heat-removing disks which together form sections are disposed between two neighboring sectioned disks. Additional openings in the sections form channels. The hexagonal tubes of the basket are formed in three layers, the inner layer having a cellular structure composed of spacing frames in which tiles of neutron-absorbing material are disposed, the ends of the hexagonal tubes being sealed. The invention provides an optimal nuclear-safe arrangement of 18 SFAs within the dimensions of the basket.

Description

TRANSPORT PACKAGING CASE FOR IRRADIATED FUEL ASSEMBLY

The field of technology to which the invention belongs

The invention relates to nuclear power, to devices for handling spent nuclear fuel (SNF) of nuclear power plants (NPPs) with reactor units VVER L 000/1200/1 ZOO/TOI in the form of irradiated fuel assemblies (SFA) and can be used for their placement in a container during transportation and / or storage.

Prior Art

Known container cover for transportation and storage of spent nuclear fuel (SNF) (p. RF No. 2642853, publ. two spacer grids made of stainless steel, between them there are hexagonal tubes for accommodating fuel assemblies, having neutron protection and installed relative to the axis of the central tube in two annular rows. The sections are mounted on a base consisting of a spacer support with holes. Heat-removing disks are installed between the spacer grids parallel to them, and steel racks are installed parallel to the hexagonal pipes. The neutron shield is installed inside each face of the pipe in the form of a plate made of a boron-containing composite.

The disadvantage of this cover is:

- execution in the form of a composite structure of sections, which, when the operation of the container can lead to staggering on the inner surface of the hexagonal tubes of the cover at the junction between the sections;

- load-bearing elements of the casing are made of a material (aluminum alloy), which has low strength characteristics under dynamic emergency impacts in the upper temperature range (up to +350°C);

- uneven distribution of neutron-absorbing material along the height of the cover;

- the absence of sockets on the upper disk for directing SFAs when they are loaded into the case;

- load-bearing structural elements of the case made of aluminum alloy do not provide corrosion resistance to aggressive environments.

As a prototype, a cover was chosen for placement and storage of spent fuel assemblies of the VVER-1000 reactor (p. RF No. 2453007, publ. 06/10/2012), containing a central tube, spacer grids with twenty tubes, in which spent fuel assemblies are placed. The pipes are made in the form of a hexagon and they are installed in two annular rows relative to the axis of the central pipe, separated by an intermediate pipe. Pipes in a row are mated with each other by ribs, and part of the faces on the outside is lined with radiation protection overlays.

The disadvantage of this cover is:

- uneven distribution of neutron-absorbing material along the edges of the hexagonal tube;

- the absence of sockets on the upper disk for the direction of SFA when loading them into a case;

- load-bearing structural elements of the case made of aluminum alloy do not provide corrosion resistance to aggressive environments; Radiation protection linings are made of expensive material based on amorphous boron.

Disclosure of invention

The technical result consists in ensuring the optimal nuclear-safe arrangement of 18 SFAs in the casing dimensions, efficient heat removal from the SFA installation area due to the creation of thermal bridges in heat-removing disks and inserts of the central tube, heat-conducting contacts between the casing and the inner cylindrical surface of the container body, increased strength of the casing design for spacing SFA under emergency dynamic effects due to the use of steel in the composition of all load-bearing elements of the casing.

The technical result is achieved by the fact that the cover for the transport packaging kit with irradiated fuel assemblies contains a central tube, a base (frame), with sectional disks with holes located on it, into which one-piece hexagonal pipes are installed in two annular rows relative to the axis of the cover for placing SFAs . Composite central tube of the cover is made of heat-removing inserts. Between two adjacent sectional disks, heat-removing disks are placed, which together form sections fastened together by fasteners. Additional openings in the sections form channels that ensure uniform filling of the internal free volumes of the container with a moderator in emergency operating conditions. The hexagonal tubes of the case are made of three layers, the inner layer is a cellular structure made up of spacer frames in which the tiles are located. neutron-absorbing material, while the ends of the hexagonal tubes are sealed.

Hexagonal pipes, sectional discs, clamping devices, fasteners are made of corrosion-resistant steel,

5 heat-removing disks and inserts of the central tube - made of aluminum alloy, providing heat removal from the SFA installation area (hexagonal tubes) to the outer cylindrical surface of the casing. At the base of the cover under the hexagonal pipes there are clamping devices that provide compression of the empty and loaded cover in the inner cavity of the container in horizontal and vertical orientation. On the upper disk of the cover there is a removable adapter for the load gripping device. Each hexagonal pipe is equipped with a socket for directing SFAs when they are loaded into the case. The case has grooves to exclude its rotation relative to the container. 5 The three-layer design of the hexagonal tubes of the cover allows you to place the required amount of neutron-absorbing material, ensures its uniform distribution in the volume of the hexagonal tube and excludes its exit from the sealed volume under normal and emergency operating conditions. 0 The geometry and perforation of the sectional and heat-removing disks with the formation of channels ensures uniform filling of the internal free volumes of the container with a moderator (water, ice, snow, steam) in emergency operating conditions.

The presence of contact surfaces between the heat-removing inserts of the central tube and the heat-removing disks of the case makes it possible to ensure efficient heat removal from the SFA installation area to the inner cylindrical surface of the cask body.

The peculiarity of the execution of the hexagonal tubes of the cover in the form of a one-piece jointless design and the presence of sockets increased the operational characteristics of the cover. steel structure hexagonal tubes of the cover allowed to set the optimal number of heat-removing discs while maintaining the rigidity of the cover as a whole.

Best Implementation

Figure 1 shows the design of the transport cover

5 packaging sets for irradiated fuel assemblies; in fig. 2 is a top view of figure 1; in fig. 3 - design of a hexagonal pipe; in fig. 4 - design of the heat-removing disk; in fig. 5 - design of the clamping device; in fig. 6 - cover design in three-dimensional image.

The cover is a metal structure consisting of eighteen hexagonal tubes 1, nine stacking sections of sectional disks 2 and heat-removing disks 3, a composite central tube of heat-removing inserts 4, upper 5 and lower 6 disks, lead-in ring 7, plate 8, eighteen clamping devices 9.5 sockets 10 over each hexagon tube 1 and gripper 11.

The material of hexagonal pipes, discs, clamping devices is corrosion-resistant steel 12X18SH0T, heat-removing discs and inserts are AMgZ aluminum alloy.

Each face of the hexagonal casing tube (Fig. 3) is a three-layer structure. The inner layer 12 consists of two triangular profiles forming a hexagon with a turnkey dimension of 243 mm. The outer layer 13 consists of two triangular profiles forming a hexagon with a turnkey dimension of 279 mm. A layer of neutron-absorbing material based on boron carbide is placed between the inner and outer layers of the pipe. Structurally, this layer is a cellular structure composed of spacer frames 14, in which tiles 15 of boron-containing composite are located. The sealing of this volume is ensured by welding end caps 16 and longitudinal welding of the outer and inner layers of the hexagonal tube of the cover. Each of the nine stacking sections of the cover consists of four disks of complex shape: two sectional and two heat-removing disks (Fig. 4). The disks of the section are fastened together by fasteners made of corrosion-resistant steel (not shown in the figure). Sections are installed at a certain distance one above the other. Structural elements of the aluminum alloy case carry out heat removal from the SFA installation area to the inner cylindrical surface of the container. Sectional discs 2 ensure the optimal location of SFAs in the inner cavity of the container. Upper 5 and lower 6 disks provide additional rigidity of the case in horizontal and vertical position. On the upper disk 5, a removable grip 11 is provided for a load gripping device (not shown in the figure).

The case has grooves 17 (Fig. 2) necessary to exclude its rotation relative to the axis of the container.

The socket 10 is a metal structure made of six petals welded together. The bell is used to guide SFAs when they are loaded into the case.

The clamping device (Fig. 5) provides compression of the empty and loaded case in the inner cavity of the container with its horizontal and vertical orientation. The clamping device consists of a cup 18, an axle 19, a central spring 20, a set of springs 21, a movable disk 22, a cage 23. The cage 23 has six grooves 24 to enable the SFA to be installed in six orientations with an angle of 60°.

Industrial Applicability

The inventive cover of the transport packaging kit for irradiated fuel assemblies is operated as follows: - the case with the help of a lifting device (not shown in Fig. 1) fixed on the grip 11 is installed vertically in the internal cavity of the container intended for transportation and storage of irradiated fuel assemblies of the VVER-Yu00/1200/1300/TOI reactor plant. The cover is installed in a certain angular position using grooves 17, into which the container guides go; lead-in ring 7 simplifies the installation of the cover;

- installation of SFAs in the case is carried out under water in a given sequence using a special load-handling device. To guide the SFA during loading, sockets 10 are used, which are installed on the top disk 5 of the casing. SFAs are installed in hexagonal tubes 1 of the cover on clamping devices 9.

The cover is transported in a horizontal position.

The removal of the cover from the cavity of the container is carried out in order to carry out routine maintenance.

The combination of these design solutions ensures the nuclear safe placement of 18 SFAs of the VVER-1000/1200/1300/TOI reactor plant with an initial enrichment of up to 5% in ²³⁵ U in the case, both taking into account its burnup in the reactor, and under the conservative assumption of transportation of non-irradiated fuel in accordance with the requirements IAEA SSR-6 and NP-053-16.

Claims

Claim

1. Cover of a transport packaging set for irradiated fuel assemblies (SFA), containing a central tube, a base (frame), with sectional disks with holes located on it, into which solid hexagonal pipes are installed in two annular rows relative to the axis of the cover to accommodate irradiated fuel assemblies , characterized in that the central pipe is made composite and has heat-removing inserts, heat-removing disks are placed between two adjacent sectional disks, forming together sections fastened together by fasteners, heat-removing and sectional disks have channels, hexagonal pipes are made of three layers, the inner layer is a cellular structure , made up of spacer frames, in which tiles of neutron-absorbing material are located, while the ends of the hexagonal pipes are sealed.

2. The cover according to claim 1, characterized in that at the base of the cover under the hexagonal pipes there are clamping devices that provide compression of the empty and loaded cover in the inner cavity of the container in horizontal and vertical orientation.

3. Case according to claim 1, characterized in that the hexagonal tubes, upper disk, lower disk, sectional disks, clamping devices, fasteners are made of corrosion-resistant steel, heat-removing disks and inserts of the central pipe are made of aluminum alloy, providing heat removal from the installation area SFAs (hexagonal pipes) to the outer surface of the casing.

4. Case according to claim 1, characterized in that the upper disk has a removable grip for the load gripping device.

5. Case according to claim 1, characterized in that the upper disk has a socket for directing SFAs when they are loaded into the case.

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6. Case according to claim 1, characterized in that it has grooves to prevent its rotation relative to the container.

7. Cover according to claim 1, characterized in that the tiles of the neutron-absorbing material are made on the basis of natural (natural) boron carbide.

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