RU2510721C1 - Container for spent nuclear fuel transportation - Google Patents

Abstract

FIELD: packing industry.

SUBSTANCE: invention relates to containers for transportation and temporary storage of spent nuclear fuel (SNF) of nuclear power plants (NPP) in the form of spent fuel assemblies (SFA). Container is comprised of metal shell including coaming with bottom and support attached to it, cylindrical ferrules attached to the coaming in concentric pattern and forming a cavity, tight cover of the mentioned cavity and internal cavity of container in the form of two covers mounted one over another on a base, neutron protection, dampers. Cavity between ferrules is filled with pads out of high-density metal, attached rigidly to the internal ferrule, inserts out of metal with high heat conductivity are placed between the pads and external ferrule, and neutron protection is placed in longitudinal channels of the inserts. Internal cover has conical form and is mounted into the internal conical groove of base and clamped by a ring put on internal row of base pins. End and cone surface of the internal cover feature annular grooves where sealing elements are placed.

EFFECT: possible transportation of spent nuclear fuel from reactors of RBMK-1000 type with increased U235 enrichment, ensuring efficient protection against gamma radiation and neutrons, and removing of heat from spent nuclear fuel loaded into container.

12 cl, 3 dwg

Description

The invention relates to containers intended for the transportation and temporary storage of spent nuclear fuel (SNF) of nuclear power plants (NPPs) in the form of spent fuel assemblies (SFA).

SFAs are characterized by high residual heat release and radiation levels, which requires the use of special containers for their safe transportation.

A known container for transporting and storing SFAs (German patent No. 3026249, class G21F 5/00, 1982), which contains a thick-walled case with cooling fins on the outer surface and a corrosive inner lining. The housing is sealed with two covers, and the inner lining is held onto the housing by threaded bushings.

The disadvantage of this container is insufficient protection against neutron radiation, as well as a rather complicated manufacturing technology, which requires the use of unique metallurgical equipment to produce high-quality multi-ton metal billets.

A known container for transporting burned fuel assemblies (US patent No. 3774037, class G21F 3/00, 1973), which contains the inner and outer cylindrical shells with stainless steel bottoms and a protective overlap with its fastening elements mounted on the bottom with a loading hole. On the outer shell are annular heat sink fins. Between the shells there is radiation protection in the form of uranium castings.

The disadvantages of the design of this container are:

- the manufacture of uranium castings requires the use of special technology, which complicates the overall process of manufacturing the product, and the presence of uranium castings requires special accounting and control when using the container for its intended purpose;

- for SFAs with increased mass and depth of nuclear fuel burnout, the required level of neutron protection is not provided.

A known container for transporting and / or storage of spent nuclear fuel (RF patent No. 2453006, class G21F 5/00, publ. 10.06.2012 Bull. No. 16), containing a metal body, including a bottom, support, cylindrical shells concentrically mounted on the bottom with the formation of a cavity, a tight overlap of the said cavity and the inner cavity of the container, which is made in the form of two covers installed one above the other on a common basis, a neutron shield mounted on the outer surfaces of the inner cover, bottom and cylindrical about the shell, elements with high thermal conductivity, passed through a neutron shield located on the cylindrical shell, the aforementioned cavity between the cylindrical shells is filled with an insert of high density metal and thermal conductivity relative to the shell material, V-shaped ribs located along the shell are used as elements with high thermal conductivity the body at a length corresponding to the length of the inner cavity of the container, the walls of the ribs are perforated with grooves located in the longitudinal rows with the offset of the groove of one row relative to the groove of the other row, while the ribs protrude beyond the surface of the neutron shield and are fastened together by a shell that is the cladding of the neutron shield, the neutron shield of the inner cover is lined, the neutron shield of the bottom is placed in the support, on the support and on the outer cover dampers. In container options:

- the inner cylindrical shell, the bottom and the common base are made of stainless steel;

- the outer cylindrical shell is made of low alloy steel;

- the insert is made of copper;

- the insert is fixed between the shells by a disk, reinforced by a ring and longitudinal plates;

- an insert made of metal of high density and thermal conductivity is made of blocks fixed from longitudinal movement using rings, while the gap between the blocks and the outer shell is filled with a powder filler of the same material as the blocks;

- V-shaped ribs are fastened together by welding.

- V-shaped ribs are a two-layer structure, the inner layer is made of copper, the outer one is made of corrosion-resistant steel;

- longitudinal panels are installed and fixed on the outer shell of the case, consisting of a shell, on which V-shaped ribs are fastened and fixed, fastened together by plates, the panels are interconnected by a neutron protection lining;

- neutron protection cladding is made of stainless steel;

- neutron protection is made of siloxane rubber;

- dampers consist of different-height kerchiefs connected by a shell and an end ring;

- dampers are made of corrosion-resistant steel;

- the cylindrical shells below are equipped with coaming, on which the bottom and support are fixed;

- the bottom is made in the form of two disks;

- the inner disk of the bottom is made of corrosion-resistant steel;

- sealing of each cover with the mating surfaces of the base is made using two sealing elements installed in the grooves concentrically located on the ring annular concentrically located on the respective surfaces of the covers.

This container is taken as a prototype, as the closest in technical essence to the claimed technical solution.

The disadvantages of this container are:

- the great complexity of manufacturing and fixing by welding on the container body of the V-shaped heat sink fins of the neutron shield and the cladding of the neutron shield;

- the need to use special technological equipment to fill the intercostal space with neutron protection material;

- the process of remote installation of the inner cover on the studs, which is present during the operation of the container, is quite complex and time-consuming.

The task to be solved is to create a container for transporting spent nuclear fuel from RBMK-1000 reactors with enhanced enrichment in uranium-235, providing effective protection against gamma radiation and neutrons and removing heat from spent nuclear fuel loaded into the container.

The problem is solved in that in a container for transporting spent nuclear fuel containing a metal body, including coaming with a bottom and a support fixed to it, cylindrical shells concentrically attached to the coaming with the formation of a cavity, a sealed overlap of the said cavity and the container’s inner cavity, which is made in in the form of two covers installed one above the other on the base, a neutron shield mounted coaxially in a metal case and in existing compartments on the bunk the surface of the inner cover and in the support on the outer surface of the bottom, dampers mounted on the support and on the outer cover, the aforementioned cavity between the shells is filled with high density metal inserts rigidly fixed to the inner shell, the inserts of high thermal conductivity metal are placed between the shells and the outer shell having longitudinal channels in which the neutron shield is placed, the inner cover is conical in shape and installed in the existing internal conical groove I with a support at its end face, the inner cover is pressed against the ring wear to the inner row of pins of a base on the end face and the conical surfaces of the inner lid there are annular grooves in which sealing elements are arranged.

In container options:

- on the outer cylindrical surface of the base there are two lifting holes diametrically located on the same axis;

- the upper damper has two lifting holes in the plates of the side surface diametrically located on the same axis;

- dampers consist of different-height kerchiefs connected by a shell and an end ring;

- part of the inserts is fixed by welding using overlays to the shell;

- the ring is fixed on studs with nuts;

- longitudinal ribs are installed on the outer shell of the case;

- two coaxially mounted and offset removable pins mounted diametrically located and offset relative to the longitudinal axis of the body;

- the outer cover is made conical in shape and installed in the outer conical groove of the base with support on the end surface of the base;

- on the outer end surface of the outer cover in the center there is a removable load-gripping adapter;

- inserts are made of aluminum alloy or copper;

- neutron protection is made of polypropylene.

Filling the cavity between the shells with high density metal inserts and inserts of high heat conductivity metal, in the longitudinal channels of which there is a neutron protection made of polypropylene, it provides both effective protection against gamma radiation and neutrons, and efficient heat removal from the inner shell of the container to the outer shell . More effective protection against gamma radiation is provided by metals with a higher density, and from neutrons - by hydrogen-containing materials.

Placing longitudinal ribs on the outer shell allows more intensively by convection and radiation to dissipate heat into the environment. Also, the outer shell and ribs are structural elements that extinguish pulses of external dynamic loads acting on the container in case of emergency. Therefore, it is advisable to perform them from a material having a high coefficient of elongation, for example, from corrosion-resistant steel 12X18H10T.

The implementation of the base of the container with conical grooves under the inner and outer covers of the conical shape can significantly simplify the process of installing-removing the covers and especially the inner cover when it is remotely installed or removed using special technical devices. After fixing it on the base, the inner cover is fastened with the help of a ring put on the base studs and fixed with nuts.

Sealing the inner cover with the mating surfaces of the base with the help of sealing elements installed in the annular grooves of the end and conical surfaces provides the required level of reliability in the tightness of the connection, while providing easy access to the sealing elements during maintenance of the cover.

The execution on the outer cylindrical surface of the base of two load-lifting holes diametrically located on the same axis makes it possible to lift and carry the container in an upright position with the upper damper removed.

The presence of two holes in the plates of the side surface of the upper damper, diametrically located on the same axis, allows the container to be lifted behind them and transported in a vertical position, and when used together with trunnions placed on coaming with an offset relative to the longitudinal axis of the body, the container is tilted. In this case, the container rises by the holes of the damper, is transferred to the tilting place and is mounted with pins on the support; when the container is further lowered, it moves from a vertical position to a horizontal position.

The presence on the outer cover of a removable load-gripping adapter allows you to remove or install the cover with a lifting device without the use of additional equipment, the adapter also protects the cover when exposed to external dynamic loads in the event of a traffic emergency.

Figure 1 shows a General view of the container in section; figure 2 sealing of the inner and outer covers, element B in figure 1; figure 3 is a cross section of a container.

The container (see figures 1, 2 and 3) consists of:

- metal casing 1, including:

- coaming 2;

- support 3;

- bottom 4;

- base 5;

- inner 6 and outer 7 shells;

- liners 8;

- insert 9;

- lining 10;

- ribs 11;

- neutron protection 12;

- neutron shield 13 located in the support 3;

- removable pins 14 designed for tipping the container;

- the inner cover 15, on the outer surface of which a neutron shield 16 is installed, having a lining 17. Sealing elements 18 and 19 are installed in the grooves of the cover 15;

- studs 20;

- ring 21;

- studs 22;

- the outer cover 23. In the concentric grooves of the cover 23, sealing elements 24 and 25 are installed. The cover 23 has an adapter 26 for lifting it;

- damper 27 mounted on the support 3;

- damper 28 mounted on the outer cover 22.

The use of the container is as follows.

Spent nuclear fuel is first loaded into a spacer grid (not shown in FIG. 1), which is then installed in a container. After loading the container into the conical groove of the base 5, the inner cover 15 is installed, the ring 21 is put on and fastened with nuts, while the inner cover 15 is pressed against the end surface of the base 5. The tightness of the connection of the cover 15 with the housing 1 is checked. In another conical groove the base 5 on the studs 22 install and fasten the outer cover 23 with nuts. Perform tightness control of the connection of the cover 23 with the housing 1. After that, the container can be lifted if necessary a removable device for the holes in the base 5 and moved vertically to the required service station. A damper 28 is mounted and bolted to the outer cover 23 by guide pins. After that, the container is moved in a vertical position and moved from a vertical position to a horizontal one with support on the lower pins 14 by a lifting device, which is connected to the damper by entering the lifting device pins into the holes D damper 28. The container with SNF on the vehicle is located in a horizontal position.

After the container is transported to the SNF location for long-term storage or reprocessing, it is transferred to a vertical position and transferred to a service post where the corresponding technological operations for SNF unloading are performed. At all stages of operation of the container, the lower damper 27 from the housing 1 may not be removed.

The developed container design for the transportation and / or storage of spent nuclear fuel of reactors such as RBMK-1000 type reactors with enhanced uranium-235 enrichment, nuclear fuel burnup up to 37 GW · day / tU and residual total energy release up to 8.1 kW provides effective protection against gamma radiation and neutrons, as well as efficient heat removal from the SNF loaded into the container, which meets the requirements for the safe transportation and storage of SNF.

Claims (12)

1. A container for transporting spent nuclear fuel, comprising a metal case, including coaming with a bottom and a support fixed thereto, cylindrical shells concentrically attached to the coaming to form a cavity, hermetic closure of said cavity and the container’s internal cavity, which is made in the form of two covers installed one above the other on the base, a neutron shield mounted coaxially in a metal case and in existing compartments on the outer surface of the inner lid and support on the outer surface of the bottom, dampers mounted on the support and on the outer cover, characterized in that the aforementioned cavity between the shells is filled with liners of high density metal rigidly fixed to the inner shell, between the liners and the outer shell there are inserts of metal of high thermal conductivity having longitudinal channels in which the neutron shield is placed, the inner cover is made of conical shape and installed in the existing internal conical groove of the base with support on it the end surface, the inner cover is preloaded by a ring worn on the inner row of the base studs; on the end and conical surfaces of the inner cover there are annular grooves in which the sealing elements are located. 2. The container according to claim 1, characterized in that on the outer cylindrical surface of the base there are two lifting holes diametrically located on the same axis. 3. The container according to claim 1, characterized in that the upper damper has two lifting holes diametrically located on the same axis in the side surface plates. 4. The container according to claim 1, characterized in that the part of the inserts is fixed by welding using overlays to the shell. 5. The container according to claim 1, characterized in that the ring is fixed to the studs with nuts. 6. The container according to claim 1, characterized in that longitudinal ribs are installed on the outer shell of the housing. 7. The container according to claim 1, characterized in that the coaming has two diametrically located and offset removable axles offset from the longitudinal axis of the housing. 8. The container according to claim 1, characterized in that the outer cover is conical in shape and installed in the outer conical groove of the base with support on the end surface of the base. 9. The container according to claim 1, characterized in that on the outer end surface of the outer cover in the center there is a removable load-gripping adapter. 10. The container according to claim 1, characterized in that the liners are made of cast iron, or steel, or copper. 11. The container according to claim 1, characterized in that the inserts are made of aluminum alloy or copper. 12. The container according to claim 1, characterized in that the neutron protection is made of polypropylene.

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