RU2746959C1 - Container for transportation and storage of spent nuclear fuel - Google Patents

Abstract

FIELD: transportation and storage of nuclear fuel.SUBSTANCE: invention relates to containers; it is intended for transportation and long-term storage of spent nuclear fuel (hereinafter – SNF) in the form of spent fuel assemblies (hereinafter – SFAS). The container for the transportation and storage of SNF contains a metal case with a lower coaming with a bottom fixed on it, concentric cylindrical shells with the formation of cavities, and an upper coaming with an outer and inner lid fixed on it. Damping devices are installed on the outer lid and the lower coaming. The upper coaming is made with channels for checking and controlling the tightness of the container. Both coamings are equipped with a valve for cooling, purging, drying and vacuuming the inner cavity of the container. The upper coaming has trunnions with removable sleeves for lifting and tilting the container. The lower coaming has trunnions with removable sleeves for tilting the container. Neutron protection units have longitudinal trapezoidal channels. The gamma protection inserts are made of carbon steel. Each longitudinal rib is made of stainless steel in the shape of wedge. One contour of the sealing elements of the upper and lower coaming valves is made of a thermoradiation-resistant rubber compound, the second one is made of thermally expanded graphite.EFFECT: invention makes it possible to expand the functional purpose of the container, allowing it to be used both for transportation and for long-term storage of SNF.10 cl, 4 dwg

Description

The invention relates to containers designed for both transportation and long-term storage of spent nuclear fuel (SNF) of nuclear power plants (NPP) in the form of irradiated fuel assemblies (SFA) of VVER-1000/1200 reactor plants.

Currently, containers are used to handle NPP SNF, which are functionally specialized for their purpose:

- Containers for transportation and temporary (up to one year) storage of spent nuclear fuel;

- casks for SNF transportation from NPPs with subsequent placement for long-term (up to 50 years) dry container storage of SNF.

Specialization in the functional purpose of the container is due to the need to solve, as a rule, one main task - transportation or storage of spent nuclear fuel.

Expansion of the functional purpose of the container, providing for its use, both for transportation and long-term storage of SNF from VVER-1000/1200 reactors, has not been fully resolved at present.

Thus, a container for transportation and temporary storage (up to one year) of spent nuclear fuel from VVER-1000 reactors is known (p. Russia No. 2453006, class G21F 5/00, publ. 10.06.2012).

The container contains a metal body, including a bottom, a support, cylindrical shells concentrically fixed on the bottom to form a cavity, a hermetic overlap of the said cavity and the inner cavity of the container, which is made in the form of two covers mounted one above the other on a common base, neutron protection mounted on the outer surfaces of the inner cover, bottom and cylindrical shell, elements with high thermal conductivity, passed through the neutron protection layer located on the cylindrical shell, the aforementioned cavity between the shells is filled with an insert of high density metal and thermal conductivity relative to the shell material, ribs V are used as elements with high thermal conductivity -shaped, located along the body at a length corresponding to the length of the inner cavity of the container. The ribs are mounted on a base on a cylindrical shell and fixed to it. The ribs protrude beyond the surface of the neutron shield and are fastened together by a shell, which is the lining of the neutron shield. In the neutron protection zone, the rib walls are perforated with through grooves located in longitudinal rows with a groove in one row displaced with respect to the groove in the other row. Dampers are installed on the support and on the outer cover. This container has the following disadvantages:

- the container is not intended for long-term (up to 60 years) dry container storage of spent nuclear fuel;

- the location of the neutron protection on the outer cylindrical surface of the container and in the ribs with lining between the ribs in the event of an emergency leads to possible damage to the ribs, lining and neutron protection, which may be partially lost;

- high labor intensity of manufacturing and fastening V-shaped heat-removing fins passing through the neutron protection layer and the lining by means of welding on the container body.

Another container is known for transportation and long-term storage (up to 50 years) of spent nuclear fuel from VVER-1000/1200 reactors (p. Russia No. 2593273, G21F5 / 00, publ. 08/10/2016) with an increased mass and burn-up rate of nuclear fuel (uranium enrichment -235 to 5% and burnup up to 70 GW⋅day / tU).

The container contains a metal body, including a bottom coaming with a bottom, a support and concentric cylindrical shells attached to it with the formation of cavities, a hermetic overlap of the inner cavity of the container with two lids, an inner conical lid installed in the inner conical groove of the coaming and compressed by a ring put on the inner row coaming studs, and an outer lid mounted on the upper coaming above the inner lid. The cavity between the shells is filled with liners rigidly fixed to the inner shell; the liners consist of a sealed carbon steel body filled with high-density gamma protection. Between the liners and the outer shell there are inserts made of metal of high thermal conductivity, with longitudinal channels in which the neutron protection is located. The latter is also installed in the available compartments on the outer surface of the inner cover and in the support. Longitudinal ribs are installed on the outer shell of the body, each longitudinal rib is V-shaped and consists of a stainless steel casing and an aluminum alloy insert. Removable dampers are installed on the outer cover and support. The upper coaming is made with channels for checking and controlling the tightness of the container cavities, the lower coaming is made with a channel in which a temperature sensor is installed, the channels in both coamings have connection points for hermetically sealed connection of operating equipment, both coamings are equipped with a cooling-drying valve for the inner cavity, the upper coaming has removable pins for lifting and tilting the container, the lower coaming has pins with removable sleeves for tilting the container.

This container is taken as a prototype, as the closest in design and functionality to the claimed invention.

The container has the following disadvantages: - the increased overall dimensions of the container, allowing to accommodate up to twenty VVER-1000/1200 spent fuel assemblies, make it impossible to use the container in transport and technological operations at existing and projected NPPs;

- the shape of the thermal bridges of the neutron protection inserts, which reduces its efficiency;

- the scheme of handling the container loaded with SNF at the NPP requires the removal of the dampers of this container, which affects its safety when the container falls on the NPP;

- to install the container in the reloading well (container compartment) of the reactor hall of the NPP, it is necessary to remove the lower damper to install the container in the universal socket, which reduces its safety in case of emergency falls;

- high labor intensity of manufacturing and installation of V-shaped heat sink fins on the outer shell, consisting of a lining made of stainless steel and an insert made of aluminum alloy;

- there is no possibility of horizontal transfer of the container when handling the NPP.

The object of this invention to be solved is the development of a high-tech container design for transportation and long-term storage of spent fuel assemblies of VVER-1000/1200 reactors, providing radiation (gamma and neutron) protection, efficient heat removal from the inner shell to the outer surface of the container with subsequent dissipation into the environment. , as well as fitting into the weight and dimensions, ensuring its use in transport and technological schemes for handling spent fuel assemblies at existing and under construction NPPs.

The technical result of the development:

- expansion of the functional purpose of the container, providing for its use, both for transportation and long-term storage of spent nuclear fuel up to 60 years;

- optimization of the overall dimensions of the container (height 6050 mm - 6110 mm, outer diameter 2480 mm - 2540 mm), ensuring its use in transport and technological schemes for handling spent fuel assemblies at existing and under construction NPPs with VVER-1000/1200 reactors;

- optimization of the geometry of the neutron protection blocks of the container to ensure more effective radiation protection.

The technical result is achieved by the fact that in a container for transportation and storage of spent nuclear fuel, containing a metal body, including an upper coaming, concentric cylindrical inner and outer shells, a lower coaming with a power bottom, a hermetic overlap of the inner cavity of the container with two lids, an inner lid installed in inner groove of the top coaming, and an outer cover installed on the top coaming above the inner cover, a cavity between the inner and outer shells filled with gamma protection liners rigidly fixed to the inner shell, high thermal conductivity metal inserts placed between the gamma protection liners and the outer shell shell, having longitudinal channels in which the neutron protection is located, the latter is also installed on the outer surface of the inner cover and in the cavity of the lower coaming, longitudinal ribs mounted on the outer shell of the body, removable dampers installed on the outer cover and the lower coaming, channels for checking and controlling the tightness of the container cavities, hermetically installed valves for cooling-drying the inner cavity, pins for lifting and tilting the container; neutron shielding units have trapezoidal longitudinal channels, gamma shielding liners are made of carbon steel, each longitudinal rib is made of wedge-shaped stainless steel, one circuit of the sealing elements of the upper and lower coaming valves is made of a thermo-radiation-resistant rubber compound, the second is made of thermally expanded graphite ...

- образных пластин, демпфер на комингсе нижнем - в виде

образных, закрепленных на соответствующих основаниях. На наружной крышке закреплено кольцо, обеспечивающее защиту шпилек комингса верхнего при падении контейнера. В нижнем и верхнем комингсе имеется возможность установки дополнительных блоков адаптивной гамма и нейтронной защиты. Высота контейнера 6050 мм - 6110 мм, наружный диаметр 2480 мм - 2540 мм.In the inter-roof space of the upper coaming, it is possible to install a sealing sheet. The pins for lifting and tilting the container are equipped with removable sleeves. The container for loading spent fuel assemblies can be installed in the overload well without removing the lower damper. A connecting place is made on the surface of the container for fixing the bracket of the traverse during horizontal transfer of the container. On the end surface of the inner cover there is a ring for installing the gripping head. The structure of the inner and outer cover is equipped with elements for lifting devices. The damper on the outer cover is made as a set

- shaped plates, the damper on the lower coaming - in the form

figurative, fixed on appropriate bases. A ring is fixed on the outer cover, which protects the top coaming pins when the container falls. In the lower and upper coaming, it is possible to install additional adaptive gamma and neutron shielding units. Container height 6050 mm - 6110 mm, outer diameter 2480 mm - 2540 mm.

The implementation of gamma shielding inserts made of carbon steel provides effective protection against ionizing radiation and heat removal from the inner shell to the neutron shielding units.

The shape of thermal bridges made of metal of high thermal conductivity in the neutron shielding blocks ensures efficient heat transfer from the gamma shielding liners to the outer ribbing system of the container.

The presence of trapezoidal cavities in the neutron shielding units, filled with polypropylene, ensures effective shielding of SNF neutron radiation.

Powerful steel sealed cylindrical body provides an additional range of protection.

The system of external ribbing of the container, consisting of longitudinal wedge-shaped ribs of stainless steel, allows efficiently, by convection and thermal radiation, to dissipate heat into the environment. Longitudinal ribs are structural elements of the container that reduce dynamic loads on the contents of the container under normal and emergency operating conditions.

As part of the system for sealing the outer and inner lids of the container for transportation and temporary storage, a set of gaskets made of thermo-radiation-resistant rubber compound is used, and for long-term storage, specialized metal or graphite gaskets are used.

In the inter-roof space of the upper coaming, there is a free volume that allows the installation of the sealing sheet by welding it with the upper coaming when placing the container with SNF for long-term storage.

The structure of the valves in the upper and lower coaming includes gaskets made of thermally expanded graphite, which make it possible to ensure the tightness of the inner cavity of the container under thermal influences in normal and emergency operating conditions.

The trunnions of the upper and lower coaming are equipped with removable sleeves to ensure their maintainability.

The design of the lower damper ensures the installation of the container in the overload well (container compartment) without removing the lower damper, which ensures the safety of the container in case of emergency falls.

образных пластин, а демпфера на комингсе нижнем - в виде

- образных пластин позволяет более эффективно снизить перегрузки на содержимом контейнера при аварийных динамических воздействиях при разных углах падения контейнера.Execution of the damper on the outer cover in the form of a set

shaped plates, and the damper on the lower coaming - in the form

- shaped plates can more effectively reduce overloads on the contents of the container during emergency dynamic impacts at different angles of fall of the container.

On the surface of the container, a connecting place is made for fixing the bracket of the traverse, which, together with the trunnions of the upper coaming, carries the container in a horizontal position.

The structure of the inner and outer covers includes elements that provide connection with load-gripping devices, allowing the removal and installation of covers using slings.

There is a variant of the design of the upper and lower coaming of the container with annular grooves for accommodating adaptive gamma and neutron shielding, made, respectively, of a metal with a high density and a material with a high specific content of hydrogen.

FIG. 1 shows a general view of the container in section; in fig. 2 is a top view of the container, view A in FIG. 1 and a bottom view of the container, view B in FIG. one; in fig. 3 is a cross-section of the container, section b-b in FIG. one; in fig. 4 - a system for sealing the inner and outer covers, section G-G in Fig. 2.

The container is a power steel sealed vessel of a cylindrical shape, consisting of a body 1 with an inner cavity for placing a canister with spent fuel assemblies, which is hermetically closed by an inner lid 2 and an outer lid 3.

The body 1 consists of the coaming of the lower 4, the intermediate compartment 5 of a cylindrical shape and the coaming of the upper 6, which has a stepped-shaped loading opening.

The lower coaming 4 consists of a ring 7, a power bottom 8, a cylindrical sealed neutron protection compartment filled with polypropylene 9 and a cover 10. On the side surfaces of the lower coaming, there are edging pins 11 with removable sleeves 12. Also on the side surface of the lower coaming there are fasteners 13 for fastening the bracket (not shown in the figure) when transferring the container in a horizontal state.

The intermediate compartment 5 consists of an inner shell 14, an outer shell 15, liners 16 made in the form of thick-walled cylinders rigidly fixed to the shell 14, neutron protection blocks 17, which have longitudinal trapezoidal channels filled with polypropylene 18. On the outer surface of the compartment 5 are longitudinally mounted four rows of ribs 19.

Coamings top 6 has a stepped loading opening with two end surfaces. On one of the end surfaces there are studs 20 intended for installation and fastening using nuts 21 of the inner cover 2, on the other end surface there are studs 22 intended for installation and fastening with the nuts 23 of the outer cover 3. On the outer side surfaces of the top coaming 6 there are four pins 24 for tilting, lifting and carrying the container. Removable sleeves 25 are installed on the trunnions. There are also channels on the outer side surfaces for checking the container tightness. During transportation, the channels are closed with sealed covers.

The inner lid 2 consists of a base 26 and a sealed compartment filled with polypropylene 27, struts 28 and a ring 29, which have holes for fixing load-gripping devices and a removable gripping head for transferring the lid. Sealing elements 30 and 31 are installed in the annular grooves on the end surface of the base 26.

- образных пластин, закрепленных на соответствующих основаниях. На внутренней торцовой поверхности диска 32 имеются две кольцевые проточки, в которых установлены уплотнительные элементы 38 и 39. Крышка наружная 3 оснащена кольцом защитным 40, закрепленным при помощи винтов.The outer cover 3 consists of a disk 32, on the outer end surface of which there are pins 33 and 34 for installing load-gripping devices and a removable gripping head for transferring the cover. Also on the outer end surface of the disc 32 there are pins 35 intended for fastening with the nuts 36 of the damper of the upper 37. The damper is made in the form of a set

- shaped plates fixed on appropriate bases. On the inner end surface of the disk 32 there are two annular grooves in which the sealing elements 38 and 39 are installed. The outer cover 3 is equipped with a protective ring 40, fixed with screws.

- образных пластин, закрепленных на соответствующих основаниях. В конструкции демпфера нижнего 42 имеется три направляющих планки 43 для установки транспортного упаковочного комплекта в гнездо универсальное.A lower damper 42 is installed on the lower coaming 4 fixed with bolts 41. The damper is made in the form

- shaped plates fixed on appropriate bases. In the structure of the damper of the lower 42, there are three guide strips 43 for installing the transport packaging into the universal socket.

Two valves 44 are installed in the container, one in the upper coaming 6, the second in the lower coaming 4, designed to carry out the processes of drying and evacuation, entering the gas coolant into the internal cavity, testing the container for leaks, entering and exiting the cooler during cooldown.

In versions of the container, an adaptive gamma and neutron protection 45 are installed in the annular grooves of the upper and lower coaming.

The container is used as follows.

Spent nuclear fuel in the form of spent fuel assemblies at a nuclear power plant is loaded into a cover (not shown in the figure) installed in the inner cavity of the container. The work is carried out under a layer of water in the cooling pool.

Before diving into the pool at the service station from the container, remove the outer cover 3 with the fixed upper damper 37 and the inner cover 2, for two trunnions 24 using a traverse (not shown in the figure) the container is transferred to the pool, where the traverse is remotely uncoupled from the container.

After loading the spent fuel assembly container under water into the groove of the coaming of the upper 6, the inner cover 2 is installed on the pins 20 using a load gripping device and a gripping head pre-installed on the inner cover (not shown in the figure). The gripping device is remotely detached from the gripping head of the inner cover 2. The vertical traverse is remotely connected to the trunnions 24 of the upper coaming 6. The loaded SFA container is completely removed from the water, water is drained from the inner cavity of the container. The container is transferred to the service station, where work is performed to prepare the container for transportation:

- installation and tightening of container lids fastening nuts;

- purging the inner cavity of the container through the valves of the upper 6 and lower coaming 4;

- decontamination of the container;

- checking the tightness of the inner cavity of the container and the inter-lid space (sealing elements of the outer and inner lids).

For subsequent transportation, the container can be transferred to a vehicle, for example, a railroad car, both vertically and horizontally. The transfer of the container in a vertical position is carried out using a vertical traverse attached to the pins 24, followed by resting on the lower pins 11 and tilting from a vertical position to a horizontal one. When the container is transferred in a horizontal position, the horizontal traverse is connected to the pins 24 and a bracket (not shown in the figure) fixed on the side surface of the lower coaming 4. Then the container is fixed in the car and transported to the appropriate facility for wet storage and processing of spent fuel assemblies, or a long-term dry container SNF storage (up to 60 years):

- after transportation to the facility for temporary wet storage and processing of spent fuel assemblies, the container is removed from the car and installed on the cooldown site in a vertical position. Devices of the cooling system are connected to the valves 44 of the container and the inner cavity of the container is filled with water. After the cooldown procedure is completed, the outer cover 3 is removed together with the upper damper 37, the nuts 21 are loosened and removed on the inner cover 2. The container is transferred to the pool, after which the inner cover is remotely removed using a load gripping device. for long-term storage of spent fuel assemblies under water. All work in the pool is carried out remotely using specialized devices (shown in Fig. E). After the spent fuel assemblies are unloaded, the container undergoes a decontamination procedure.

After transportation to the facility for long-term dry container storage of spent nuclear fuel, the container is removed from the car and installed on the service platform in the spent nuclear fuel storage (ISF) in a vertical position. At the service site, the inner cavity of the container is dried (evacuated), followed by the injection of an inert gas, for example, nitrogen or helium. Next, the container is placed for long-term storage using one of the sealing methods:

a) installation of the sealing sheet in the inter-lid space by welding it with the top coaming 6;

b) replacement of 3 sealing elements 38, 39 of a rubber compound on the outer cover with specialized metal or graphite gaskets (service life up to 60 years);

c) a combination of the above sealing methods.

To control the temperature of the outer surface of the container, a temperature sensor (not shown in the figure) is mounted to its body.

Claims (10)

1. Container for transportation and storage of spent nuclear fuel, containing a metal body, including an upper coaming, concentric cylindrical inner and outer shells, a lower coaming with a power bottom, a hermetic overlap of the inner cavity of the container with two covers, an inner cover installed in the inner groove of the upper coaming, and an outer cover installed on the upper coaming above the inner cover, a cavity between the inner and outer shells filled with gamma protection liners rigidly fixed to the inner shell, inserts of high thermal conductivity metal placed between the gamma protection shells and the outer shell, having longitudinal channels , in which the neutron protection is located, the latter is also installed on the outer surface of the inner cover and in the cavity of the lower coaming, longitudinal ribs installed on the outer shell of the body, removable dampers installed on the outer cover and the lower coaming, channel for checking and controlling the tightness of container cavities, hermetically installed valves for cooling-drying the inner cavity, trunnions for lifting and tilting the container, characterized in that the neutron protection units have longitudinal trapezoidal channels, gamma protection liners are made of carbon steel, each longitudinal rib It is made of a wedge-shaped form of stainless steel, one circuit of the sealing elements of the valves of the upper and lower coamings is made of a thermoradiation-resistant rubber compound, the other is made of thermally expanded graphite. 2. The container according to claim 1, characterized in that it is possible to install a sealing sheet in the inter-lid space of the upper coaming. 3. The container according to claim 1, characterized in that the pins for lifting and tilting the container are provided with removable sleeves. 4. The container according to claim. 1, characterized in that the container for loading spent fuel assemblies can be installed in the overload well without removing the lower damper. 5. The container according to claim. 1, characterized in that on the surface of the container there is a connecting place for fixing the bracket of the traverse during horizontal transfer of the container. 6. The container according to claim 1, characterized in that a ring is installed on the end surface of the inner cover for installing the gripping head. 7. A container according to claim 1, characterized in that the structure of the inner and outer covers is equipped with elements for lifting devices. 8. The container according to claim 1, characterized in that a ring is attached to the outer cover, which protects the top coaming pins when the container falls. 9. The container according to claim 1, characterized in that in the lower and upper coamings it is possible to install additional adaptive gamma and neutron shielding units. 10. The container according to claim 1, characterized in that the height of the container is 6050-6110 mm, the outer diameter is 2480-2540 mm.

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