RU2611057C1 - Container for storage and transportation of spent fuel assemblies and case for their arrangement - Google Patents

Abstract

FIELD: packaging industry.

SUBSTANCE: invention relates to containers and cases, for transportation and storage of spent nuclear fuel. Container comprises a metal body, cylindrical shells concentrically mounted on the coaming. Between inserts and outer shell there are cylindrical inserts. Container cavity is tightly covered with two covers. On the inner cover and in the support under the bottom there is a neutron shield. On the top cover and support there are dampers. Inner cover is sealed in the form of two metal rings. In the upper coaming there are channels for checking leak integrity of the container cavities. In the lower coaming there is a channel, in which there is a valve for cooling-drying of the inner cavity. Channels and valve have the possibility of tight attachment of operational equipment. On the outer shell there are grouped lengthwise ribs.

EFFECT: invention allows to transfer, store for a long time, transport for recycling 31 pcs of SFA reactors of the PWR-1000 type.

22 cl, 9 dwg

Description

The invention relates to containers for transporting spent nuclear fuel (SNF) from nuclear power plants (NPPs) to storage for long-term storage, followed by storage of a container with SNF for storage after storage.

Currently, transport packaging kits are used to transport the spent nuclear fuel of the NPP, consisting of a sealed power container and a cover placed inside the container, having spaced diaphragms with channels for spent nuclear fuel. The container and the cover, as a rule, are intended for transportation and storage (short-term storage up to one year or long-term storage up to 50 years) of SNF of a specific type of reactor. SNF is characterized by the composition and depth of burnup of nuclear fuel, as well as the exposure time after discharge from the reactor. Structurally, nuclear fuel loaded into the reactor is made in the form of fuel assemblies (FAs), the geometric shape and overall dimensions of which are different for each type of reactor. Thus, the cross section of a fuel assembly can be round, square or hexagonal. Therefore, for transportation or storage of specific SNF they use their transport packaging set. Functionally transportable packaging sets can be single-purpose or dual-use. Single-purpose transport packaging kits serve either for transporting or for storage of spent nuclear fuel. Dual-use transport packaging kits serve for both multiple transportation and long-term storage of spent nuclear fuel. Currently, it is relevant to solve the problem of creating a reliable, modern IAEA requirements, transport packaging set designed for the transportation and long-term storage of SNF of a specific type of reactor having an increased nuclear fuel burn-up depth (not less than 70 GW · s / tU) and residual energy release of each spent fuel assembly (SFA) of at least 2 kW. Also, based on technical and economic requirements for optimizing the costs of organizing a long-term, at least 50 years, container storage of spent nuclear fuel, there is a need to create containers of relatively large usable volume that provide maximum capacity under certain, in particular, transportation, restrictions on their overall dimensions.

A known container for transporting radioactive materials (p. JP 3342994 B2 G21F 5/10, G21C 19/32, G21F 9/36, 2002), containing a metal casing, consisting of a bottom, outer and inner cylindrical shell, between which there are shielding layers for protection against gamma radiation and neutrons. Elements with high thermal conductivity are passed through the shielding layers, respectively attached to the said shells. There is a tight overlap of the cavity between the shells and the inner cavity of the housing, which is made in the form of two covers mounted one above the other on a common base and forming two concentric sealing circuits with the latter. To move the container, lifting trunnions are provided in the upper part of the body.

This container has the following disadvantages:

- low heat transfer of the outer cylindrical surface of the container body in view of the absence of cooling fins on it;

- insufficient efficiency of heat removal from the inner shell of the housing through the shielding layers on steel thermal bridges to the outer shell, because steel has a relatively low thermal conductivity compared to other known materials, for example aluminum alloys;

- “direct cross” of neutrons along the mentioned elements of the thermal bridge is possible, which reduces the level of protection against neutron radiation;

- the container does not have damping elements designed to reduce the dynamic loads acting on it and the radioactive materials placed in it in case of emergency during transportation;

- the container is not adapted for transportation and long-term storage in it of SFA of PWR-1000 reactors.

A well-known container for transporting spent nuclear fuel of RBMK-1000 type reactors (Sec. RF No. 2510721, G21F 5/00, publ. 04/10/2014).

The container contains a metal case, including coaming with a bottom and a support fixed to it, shells concentrically attached to the shell coaming with a cavity, hermetic overlap of said and internal container cavities, made in the form of two covers mounted one above the other on the base, neutron protection, removable trunnions mounted on coaming dampers. The 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 installed in the inner groove of the base and is tightened by a ring worn on the inner row of studs of the base. On the outer and inner cover there are annular grooves in which the sealing elements are located.

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

The disadvantages of this container are as follows:

- the container is intended for transportation and temporary (up to one year) storage of SNF of the RBMK-1000 type, cut into bundles of fuel elements (PT) and placed in special ampoules;

- the container is intended for loading or unloading ampoules with PT only in a “dry” way, without immersing the container with load-gripping equipment in the pool under water. There are no auxiliary equipment and technology for using the container to load fuel under water. While the SNF loading technology with a high burn-up depth and a holding period of up to 6 years involves loading or unloading by the “wet” method, in a pool under water;

- low heat transfer of the outer cylindrical surface of the container body in view of the underdeveloped shape of the cooling fins. The energy release of spent nuclear fuel transported in such a container is limited and does not exceed 10 kW;

- the presence on the inner lid of sealing elements from a thermo-radiation-resistant mixture does not provide the required level of reliability of sealing the inner cavity of the container during its long-term (at least 50 years) storage with SNF.

Known metal container for transportation and / or storage of spent assemblies of fuel elements of nuclear reactors (p. RF No. 2189648, G21F 5/08, publ. September 20, 2002).

The container contains a housing with a bottom, with inner and outer protective sealing caps and end damping elements, a cover inserted into the cavity of the housing, including diaphragms with openings-cells for installing pencil cases with spent fuel assemblies, and rigging assemblies located on the housing. End damping elements located on the lower diaphragm of the case are simultaneously supporting elements of the case interacting with the bottom of the case. The case is equipped with shielding metal structures located around the diaphragms along its longitudinal axis, connecting the diaphragms.

However, the known metal-concrete container has a relatively small capacity, because it is designed in the dimensions of metal containers of the TK-18 type in order to use the existing infrastructure designed to handle these containers. Also, the target characteristics of the well-known metal-concrete container do not meet the target characteristics of the containers intended for transportation and long-term (at least 50 years) storage of SNF of nuclear reactors of the PWR-1000 type.

A well-known container for transporting and / or storage of spent nuclear fuel (p. RF No. 23224241, G21F 5/08, publ. 05/10/2008), containing a housing in which a cover is placed, including interconnected diaphragms with cells for installing bundles of fuel elements (PT) and the Central pipe with a shank for cargo capture, at least one protective sealing cover, made under the recess in the upper part of the housing, rigging nodes located on the housing, and the centers of the cells in the plan are located along the contours corresponding their regular hexagons having a common center which is aligned with the geometrically longitudinal central axis of the tube. The diaphragms of the case are rigidly connected by means of longitudinal rod elements located around the diaphragms along the longitudinal axis of the case, the container contains tubular elements that are installed in a fixed position, respectively, between adjacent diaphragms of the cover coaxially with corresponding non-adjacent cells, and the inner diameter of the tubular elements corresponds to the diameter of the cells while the cover is equipped with supporting damping elements that are installed on the outside of the lower diaphragm.

This container has the following disadvantages:

- the container refers to metal-concrete containers intended for long-term storage of SNF of RBMK reactors, divided into PT. SNF of the indicated type of reactors have a small depth of burnout and residual energy release. A cover with the installed PTs is loaded into the container. Loading the PT into the case and the case from the PT into the container is carried out according to technology that does not provide for these operations in the underwater pool, which is used when handling SFAs, for example, VVER or PWR reactors;

- the cover with the PT after being installed in the container body is not fixed from longitudinal movements, which in case of an emergency during transportation can lead to the impact of the cover from the PT on the inner cover. Given the possibility of a similar situation, reinforced fasteners are used to eliminate the depressurization of the connection of the inner lid with the housing, which complicates the maintenance of the container.

The cover of this container is selected for the prototype, as the closest in technical essence to the claimed technical solution.

The technical result consists in the fact that it is necessary to create a container and a cover for transporting and long-term storage (at least 50 years) of spent fuel from reactors of the PWR-1000 type with enriched uranium fuel with a burnup depth of up to 70 GW · day / tU, as well as MOX fuel with enrichment according to Pu and a burn-up depth of up to 60 GW · day / tU.

The technical result is solved by the fact that in the container for transporting spent nuclear fuel containing a metal body, including a lower coaming with a bottom and support fixed thereto, cylindrical shells concentrically attached to the coaming with the formation of a cavity filled with high-density metal inserts rigidly fixed to inner shell, between the liners and the outer shell placed cylindrical inserts of metal with high thermal conductivity, having longitudinal channels For the neutron shield, the aforementioned cavity is hermetically sealed by the upper coaming, the inner cavity of the container is sealed by two covers installed one above the other on the upper coaming, the neutron shield is placed on the inner cover and in the support under the bottom, and the upper cover and support are installed dampers, the inner cover has a seal made in the form of at least two metal rings and one sealing element from a thermo-radiation-resistant rubber compound installed in concentric grooves on the end surface of the lid. In the upper coaming there are channels for checking the tightness of the container cavities, and in the lower coaming there is a channel in which the dampening-drying valve of the internal cavity is installed, while the channels have the ability to tightly connect production equipment. Grouped ribs are made on the outer shell.

In the inner lid there is a channel in which there is a dampening-drying valve for the inner cavity of the container, while there is the possibility of hermetically connecting the operating equipment to the channel and valve. On the upper coaming are two diametrically located removable pins. On the lower coaming, two diametrically arranged and offset relative to the longitudinal axis of the axle are installed. The trunnions can be made removable. Upper and lower coamings are made of stainless steel. The inner and outer shells are made of stainless steel. Inserts made of carbon steel. The inserts are made of aluminum alloy. Neutron protection made of polypropylene. Longitudinal ribs are made of stainless steel. The inner cover is installed in the inner groove of the upper coaming and is tightened by a ring worn on the inner row of studs. The ring is fixed to the cover using fasteners, such as bolts. The caps are sealed using o-rings made of thermo-radiation-resistant rubber compound. A longitudinal guide bar is installed on the inner shell of the housing. An annular groove is made in the cavity of the container on the cylindrical surface of the housing. The damper mounted on the top cover is secured by fasteners, such as bolts, to the upper coaming.

The cover contains a diaphragm with cells for installing fuel elements. The diaphragms of the case are rigidly connected by means of longitudinal rod elements. Between the diaphragms there are sections with a longitudinal gap, consisting of spacing discs fastened together by square pipes in cross section, the walls of which are lined with boron carbide inserts. A split locking ring is mounted on the upper diaphragm. The diaphragms and spacers of the sections have a guide groove.

The case has 31 channels for accommodating the PWR-1000 type SNF of the reactor, while in the central part there are 4 channels, 10 channels are arranged in a ring around the central part and 17 channels are located in the outer ring. Diaphragms, longitudinal rod elements and a split locking ring are made of stainless steel. The sections are made of aluminum alloy.

The presence in the lower coaming and the inner cover of the dampening-drying valves of the inner cavity of the container allows, according to known technology, to dampen the container, i.e. provide lowering the temperature of the cavity of the container in which the spent fuel is placed by filling the cavity with running water; draining water from the container, draining the internal cavity, checking the cavity for leaks and filling it with the required gaseous medium after loading SNF into the container in the holding pool of the nuclear power plant.

The implementation of the channels in the upper coaming, having connecting places for the tight connection of production equipment, allows remote control of the tightness of the container by measuring the pressure in the cavities between the sealing elements of the covers, as well as between the inner and outer cover.

The execution of annular grooves on the inner end surface of the inner lid, in which two metal gaskets are installed and one gasket made of thermoradiocin-resistant rubber compound, allows the container with SNF to be transported and stored for a long time to ensure reliable sealing of the cavity in which the SNF is placed, i.e. to. the service life of metal gaskets exceeds the period of long (at least 50 years) storage of the container with spent nuclear fuel. In the event of an emergency during transportation of the container with SNF, the joint of the inner cover with the base of the housing may open, and the size of the joint may exceed the amount of residual elastic deformation of the metal gaskets. In this case, the main sealing element is a gasket made of thermoradiation-resistant rubber compound, the elastic deformation of which exceeds the possible value of the joint opening. During and after prolonged storage of the SNF container, if necessary, replace the gaskets in the outer cover. In the event of an emergency during transportation, the outer lid is the main element to maintain the tightness of the container.

Placement of grouped longitudinal ribs on the outer shell of the housing, made in the form of a rail having a comb shape in cross section, allows to provide the required area of the outer surface of the container through which heat dissipates intensively by convention and radiation into the environment.

The installation of removable trunnions for lifting and tilting the container on the upper coaming of the hull allows the use of known auxiliary lifting equipment for loading (unloading) SNF into the container under water.

The diaphragms of the case with longitudinal rod elements made of stainless steel are the power frame of the case, and the cells in the diaphragm determine the positional location of the SFA. Placing sections made of aluminum alloy between the diaphragms and consisting of spacing discs fastened together by square pipes in cross section, the walls of which are lined with boron carbide inserts, allows:

- ensure nuclear safety requirements when placing 31 SFAs of PWR-1000 reactors in a case, with 4 SFAs located in the central part, 10 SFAs located around the central part and 17 SFAs located on the outer ring, which is optimal with respect to the diameter of the cover ;

- ensure efficient heat removal from the SFA to the container.

The presence of a longitudinal gap between the diaphragms and sections eliminates the occurrence of temperature stresses in the structural elements of the cover.

The presence of guide grooves in the diaphragms and spacer discs allows you to position the angular position of the cover in the container along the bar, mounted on the inner shell of the container body,

The cover was fixed from axial movement in the container body by means of a locking ring installed in the annular groove of the body, which makes it possible to remove the effect of the mass of the cover on the inner cover in both standard and emergency situations with the container loaded with SNF.

In FIG. 1 shows a General view of the container with a cover in section; FIG. 2 is a plan view of the container, view A in FIG. one; FIG. 3 is a cross-sectional view of the container, section BB in FIG. one; FIG. 4 - sealing of the inner and outer covers, element B in FIG. one; FIG. 5 - channels for checking tightness in the upper coaming, section GG in FIG. 2; FIG. 6 - upper part of the cover, element D in FIG. one; FIG. 7 is a top view of the case, view E in FIG. 6; FIG. 8 is a longitudinal section of a cover, view G in FIG. 7; FIG. 9 - wall of a square pipe, element And in FIG. 8.

The container consists of a metal casing 1, including the upper 2 coaming with channels “a” for checking the tightness, support 3, bottom 4, lower 5 coaming, inner 6 and 7 outer shells, inserts 8, inserts 9 having longitudinal channels in which neutron shield 10, grouped ribs 11, neutron shield 12 located in support 3, removable trunnions 13 and 14, designed for lifting and tilting the container, locking pins 15 and 16. The inner cavity of the container is closed by an inner cover 17, on the outer surface of which is installed Lena has a neutron shield 18 having a lining 19. On the outer end surface of the lining 19 there are mounting holes for lifting the cover 17. In the concentric grooves of the cover 17, metal sealing elements 20 and 21 are installed, as well as a sealing element 22 made of heat-radiation-resistant rubber compound. A ring 23 is fixed on the inner lid 17 with bolts 24. The inner lid 17 has a channel in which a dampening-drying valve for the inner cavity 25 is installed. An outer lid 26 is mounted on the coaming top 2. Sealing elements 27 and 28 are installed in the concentric grooves of the lid 26 thermo-radiation-resistant rubber compound. On the outer end surface of the cover 26 there are holes designed to lift it. Dampers 29 are installed on the support 3 and the outer cover 26. The damper 29 mounted on the outer cover 26 is fixed by fasteners to the flange of the coaming of the upper 2. In the lower coaming 5 there is a channel in which the dampening-drying valve of the internal cavity 25 is installed. In the housing 1 there is a guide bar 30 and an annular groove "b". A case 31 is installed in the housing 1, having channels for accommodating 31 pieces. SFA. The cover 31 consists of diaphragms 32 interconnected by longitudinal rod elements 33. Between the diaphragms 32 are installed with a longitudinal clearance “c” of section 34, consisting of spacers 35 fastened together by square tubes 36, the walls of which are lined with boron carbide inserts 37. In the diaphragms 32 and the spacer discs 35 sections 34 there is a guide groove "d". On the upper diaphragm 32, a split locking ring 38 is inserted that fits into the annular groove “b” of the housing 1. On the outer end surface of the upper diaphragm 32 there are mounting holes for lifting the cover 31.

This design of the container with a cover allows you to transport, store for a long time (at least 50 years), and then transport for disposal 31 pcs. SFA of PWR-1000 type reactors with enriched uranium fuel with a burn-up depth of up to 70 GW · day / tU, as well as MOX fuel with Pu enrichment and a burn-up depth of up to 60 GW · day / tU, while the overall mass characteristics make it possible to operate with known processes using existing equipment.

Using a container with a cover is as follows.

To lift and tilt the container, the pins 13 and 14 are used. The cover 31 is installed in the container body 1 with the container vertically removed from which the damper 29 and the covers 17 and 26 are removed. Before installing the container body 1, the split diaphragm is removed from the upper diaphragm 32 of the cover 31. ring 38. After placing the cover 31 in the container body 1, a previously removed split locking ring 38 is installed, while it enters the annular groove “b” of the body 1, and is fixed to the upper diaphragm 32 of the cover 31.

The container with the cover 31 installed therein is delivered to the NPPs in a railway carriage or by road. Further, the technology for handling the transport packaging set of a particular nuclear power plant is used, for example, in the following sequence:

- after delivery to the nuclear power plant, the container is unloaded and transferred to the internal loading car with a crane. Damper 29 is removed from the container either on a vehicle or on a loading car;

- the container on the transfer car is delivered to the pool building in which the spent nuclear fuel is located. In the pool building, using the crane of the pool building, the container is installed at the service station, where it is prepared for loading operations. From the service station, the container is transferred to the intermediate level of the loading compartment, where, if necessary, further preparatory work is carried out with the container. The list of work performed during these operations includes such operations as installing on the end face of the outer cover 26 a technological adapter for connecting to the load gripping device, removing the outer cover 26, unfastening the ring 23 fixed to the upper coaming 2 with the help of pins 15. Installing on the end the inner cover 27 of the technological adapter for connection with the load gripping device, removing the inner cover 17;

- after preparatory work, the container is lowered into the loading compartment of the pool;

- SNF is loaded into the container under water in the loading compartment of the pool, after which the inner cover 17 with the ring 23 fixed to it by bolts 31 is also mounted on the container in the loading compartment, and the ring 23 is put on the studs 16;

- then the container is transferred to the intermediate level of the loading compartment, where it is prepared for the closing operation. Then the container is delivered to the service station, a closing operation is performed. The list of works performed during these operations includes such things as draining water from the container, draining the internal cavity, checking the cavity for leaks and filling it with the required gas medium, using one or two valves 25, ring fastening pos. 23, removing the technological adapter from the inner cover 17, installing and securing the outer cover 26, removing the technological adapter from the outer cover 26, deactivating the container, checking the tightness of the cavity between the covers 17 and 26 and the sealing elements 21 and 22, 27 and 28, using the channels a ”in coaming top 2;

- using the crane of the pool building, the container is placed in the internal carriage;

- a loading wagon with a container is delivered to a semi-gantry crane, with which the container is then loaded into a railway wagon. The installation of dampers 29 on the container can be made when it is located both in the wagon-reloader and in the railway wagon.

The container is transported to the appropriate storage facility. At the storage facility, using lifting equipment, the container is removed from the wagon and delivered to a service station where, according to the regulations adopted at the storage facility, the container is prepared for long-term storage, after which it is delivered to the long-term storage hall. If necessary, an additional protective cover is installed on the upper coaming 2 of the container. To control the tightness of the container cavities, appropriate operating equipment is installed on it, for example, shutoff valves and pressure monitoring sensors. During long-term storage, if necessary, the sealing elements 27 and 28 of the top cover 26 can be replaced.

Claims (22)

1. A container for storing and transporting spent fuel assemblies (SFA), comprising a metal case, including a lower coaming with a bottom and support fixed thereto, cylindrical shells concentrically attached to the coaming with the formation of a cavity filled with high-density metal inserts, rigidly fixed to the inner shell, between the liners and the outer shell housed cylindrical inserts of metal of high thermal conductivity, having longitudinal channels in which the neutron I protection, the aforementioned cavity is sealed by the upper coaming, the container cavity is sealed by two covers installed one above the other on the upper coaming, a neutron shield is placed on the inner cover and in the support under the bottom, dampers are installed on the upper cover and support, characterized in that the sealing the inner cover is made in the form of at least two metal rings and one sealing element made of thermo-radiation-resistant rubber compound installed in concentric grooves on the end the surface of the lid, in the upper coaming there are channels for checking the tightness of the container cavities, and in the lower coaming there is a channel in which the dampening-drying valve of the internal cavity is installed, while the channels and the valve have the ability to tightly connect operating equipment, grouped longitudinal are made on the outer shell ribs. 2. The container according to claim 1, characterized in that the inner lid has a channel in which a dampening-drying valve of the inner cavity is installed. 3. The container according to p. 1, characterized in that to the channel and valve of the inner cover there is the possibility of tight connection of operational equipment. 4. The container according to claim 1, characterized in that two diametrically located removable pins are installed on the upper coaming. 5. The container according to claim 1, characterized in that two diametrically arranged and offset relative to the longitudinal axis of the axles are installed on the lower coaming. 6. The container according to claim 1, characterized in that the pins mounted on the lower coaming are removable. 7. The container according to claim 1, characterized in that the upper and lower coamings are made of stainless steel. 8. The container according to claim 1, characterized in that the inner and outer shells are made of stainless steel. 9. The container according to claim 1, characterized in that the liners are made of carbon steel. 10. The container according to claim 1, characterized in that the inserts are made of aluminum alloy. 11. The container according to claim 1, characterized in that the neutron shield is made of polypropylene. 12. The container according to claim 1, characterized in that the grouped ribs are made of stainless steel. 13. The container according to claim 1, characterized in that the inner lid is installed in the inner groove of the upper coaming and is tightened by a ring worn on the inner row of pins. 14. The container according to claim 1, characterized in that the ring pressing the inner lid is fixed to the lid using fasteners, such as bolts. 15. The container according to claim 1, characterized in that the sealing of the covers is carried out using o-rings made of heat-radiation-resistant rubber compound. 16. The container according to claim 1, characterized in that the damper mounted on the top cover is secured by fasteners, such as bolts, to the upper coaming. 17. The container according to claim 1, characterized in that a longitudinal guide bar is installed on the inner shell of the housing. 18. The container according to claim 1, characterized in that an annular groove is made in the container cavity on the cylindrical surface of the housing. 19. A cover containing diaphragms with cells for installing fuel elements, the diaphragms of the cover are rigidly connected by means of longitudinal rod elements, between the diaphragms there are sections with a longitudinal gap, consisting of spacer discs fastened together by square tubes in section, the walls of which are lined with boron carbide inserts , on the upper diaphragm, a split locking ring is installed, in the diaphragms and spacers of the sections there is a guide groove. 20. The case according to claim 19, characterized in that it has 31 channels for accommodating the spent fuel of the PVR-1000 type, with 4 channels in the central part, 10 channels in a ring around the central part and 17 channels in the outer ring. 21. A case according to claim 19, characterized in that the diaphragms, longitudinal rod elements and a split locking ring are made of stainless steel. 22. Case under item 19, characterized in that the sections are made of aluminum alloy.

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