RU2493622C1 - Reuse case for temporary storage of ampoules with bundles of spent fuel elements - Google Patents

Abstract

FIELD: power engineering.

SUBSTANCE: case comprises a body with a circular groove arranged in it, vertical stands, a lattice forming cells for placement of ampoules and a cover with a weight-gripping device made in the form of a central knob, a lock with locking rods installed in the central knob. The cover is installed onto the support flange connected to the body under the circular groove with welding. Locking rods are installed in guides on the outer surface of the cover and are connected with the lock. Upper surfaces of the circular groove and the locking rods are made at the angle that does not exceed the friction angle, and in the cover there is a hole, in which there is an aerosol filter.

EFFECT: higher safety when reloading ampoules with bundles of fuel elements due to placement of remaining ampoules with bundles of fuel elements in a reuse case temporarily placed in a storage seat.

5 cl, 2 dwg

Description

The invention relates to nuclear energy, in particular, to means for storing spent nuclear fuel elements of the RBMK-1000 reactor, and more particularly to means for ensuring safety during overloading of ampoules loaded with bundles of spent fuel elements (fuel elements) of the RBMK-1000 reactor, and is intended for use in a "dry" storage facility for spent nuclear fuel.

Ampoules for the spent fuel assembly (see RF patent No. 2353010, CL G21F 5/008, 2008), with fuel rod bundles placed in them, enter the “dry” storage facility for spent nuclear fuel (SNF) in a transport case installed inside the protective container (see RF patent No. 23234241). A transport case with ampoules with bundles of fuel rods is removed from the protective container and placed in the receiving socket of the camera picking case (hereinafter - KKP). When fully loaded, 144 ampoules with bundles of fuel rods are placed in the transport case. In KKP, ampoules with fuel rod bundles are reloaded from the transport case into sealed spent nuclear fuel storage cases (see RF patent No. 2372678, Cl. G21F 5/008, 2008), each of which contains 30 ampoules with fuel rod bundles. Overloading of ampoules with fuel rod bundles is carried out remotely by an electromechanical non-copying bridge manipulator with a lifting capacity of 500 kg (project 1697-20-0002 developed by OJSC Central Engineering Design Bureau).

After the case is completely filled with ampoules with bundles of fuel rods, a cover is installed on the case, connected to the case by welding, vacuuming and filling the case with nitrogen-helium mixture with overpressure are carried out through the cover valve, then the valve is sealed with welding and the welds are checked for tightness . Further, according to the existing transport scheme, with the help of a overhead crane, a pencil transfer machine and a reloading machine, fully loaded pencil cases are installed in the dry storage sockets.

Known sealed storage case for spent nuclear fuel of the RBMK-1000 reactor (see RF patent No. 2372678, CL. G21F 5/008, 2008), in which ampoules with bundles of fuel rods are loaded. Known pencil case consists of a housing, grill and cover. The body is formed by a cylindrical shell, on the upper thickened end of which a bore is made for installation and subsequent welding of the cover, and a blank bottom with a shock absorber. The housing is equipped with a central pipe for engaging it with the lid before welding, for which a bore with an entry chamfer and a special groove is made in the upper thickened part of the pipe. The cover is a disk, in the central thickened part of which a through step hole is made, in which there is a valve for pumping and filling the housing with storage medium, as well as a ball lock for engaging the cover with the housing of the pencil case before welding it to the housing. A collar and fungus of the load gripping device are made on the lid. At the end of the fungus, an edge is made for welding the valve. The valve includes a ball in the centering support, a control rod-plug and two springs. An edge for welding the valve is made at the upper end of the control rod.

The ball lock consists of a sleeve, balls placed in holes in the central thickened part of the cover, spring and nut.

The valve is opened by an external pusher, which, overcoming the resistance of the springs, moves the ball dummy rod, centering the support all the way into the ball lock sleeve, and with further movement of the dummy rod, the ball lock spring is compressed. In this case, the lock balls are in the groove zone, the ball lock opens when the lid is lifted, and the lid is removed from the pencil case. After removing the force from the external pusher, the ball lock sleeve rises under the action of the ball lock spring, and the valve elements under the action of two valve springs. The lattice is used to place ampoules with bundles of fuel rods in a pencil case and to prevent their uncontrolled spontaneous movement during transportation and storage, which are carried out in an upright position. The lattice is made in the form of a set of disks with coaxial holes forming 30 cells for placement of ampoules with bundles of fuel elements. The disks are mounted on vertical racks at certain distances from each other, calculated by the formula, which allows the installation of ampoules with permissible directness.

Work with a pencil case is as follows.

In the initial state, the cover is installed in the body of the pencil case, the valve and ball lock are closed. After introducing an empty pencil case into the protective chamber, the control rod-plug with an external pusher lowers down, compresses the valve springs, the centering support rests against the sleeve and compresses the ball lock spring. At the same time, the lock balls are in the groove zone, the ball lock opens when the lid is lifted, the lid is removed from the pencil case. Ampoules with bundles of fuel rods are installed in the cells of the lattice. After loading the canister with ampoules with bundles of fuel rods, the lid is installed on the canister case, while the lower end of the central part of the lid initially enters the upper part of the central tube, which should help to combine the welded edges of the lid and the canister case. Next, the lid is welded to the body, the control rod-plug opens the valve through which the pump is evacuated and the case filled with a nitrogen-helium mixture with excess pressure, after which the valve closes. The valve is sealed by subsequent welding of the edges of the plug stem and the end of the cap fungus. After checking the tightness of the welds, the loaded known canisters are transported to storage slots.

A disadvantage of the known pencil case is that a ball lock for engaging the cover with the pencil case can only be used to transport the empty pencil case, since it does not provide tightness of the pencil before welding the cover and pencil case, and therefore cannot be used as a reverse pencil for temporary storage of the remainder of the ampoules with the fuel rods in the storage slot.

Known sealed storage case for spent nuclear fuel (see RF patent No. 2435239, IPC G21C 19/06, 2010), comprising a housing, a grill installed inside the housing and a cover, which is selected by the applicant as a prototype.

The body is formed by a cylindrical shell, on the upper thickened end of which a bore is made for installation and subsequent welding of the cover, and a blank bottom with a shock absorber. An inner annular groove is made in the housing at the upper thickened end.

The cover is a disk in which a fungus is installed in the central thickened part, in which a lock is installed with the ability to hold the case of the cover until the weld seam is connected to the case of the canister by inserting locking rods installed in the guides on the inner surface of the cover into the annular groove while aligning the welded edges of the central fungus and stub. A valve is installed in the central fungus of the lid for pumping and filling the canister with the storage and tightness control medium and the plug-rod controlling it. A sleeve with plates in which inclined grooves are made is connected to the dummy rod, movable axes are mounted in the grooves, pivotally connected to the locking rods, and the dummy rod is provided with a collar with an annular groove in which a gasket of elastic material is installed.

The lattice is used to place ampoules in a pencil case and to prevent uncontrolled spontaneous movement of them during transportation and storage, which are carried out in an upright position. The lattice is made in the form of a set of disks with coaxial holes forming 31 cells for accommodating spent fuel assemblies. The disks are mounted on vertical racks at certain distances from each other, calculated by the formula, which allows the installation of ampoules with permissible directness.

Download ampoules with PT in a known case is as follows.

The lid is removed from the empty canister installed in the loading slot. Ampoules with a PT electromechanical non-copying bridge manipulator are one at a time removed from the cover and installed in the lattice cells. After the canister is fully loaded with ampoules with a PT, the lid is installed on the canister case. Next, the lid is welded to the body, the control rod-plug opens the valve through which the pump is evacuated and the case filled with a nitrogen-helium mixture with excess pressure, after which the valve closes. The valve is sealed by subsequent welding of the edges of the plug stem and the end of the cap fungus.

A disadvantage of the known pencil case is that its lock is also able to hold the pencil case by introducing locking rods into the annular groove and can only be used to transport the empty pencil case, since it does not provide tightness of the pencil case before welding the lid and the pencil case, therefore it cannot be used as a reverse case loaded with the remainder of the ampoules with fuel rods bundles, and temporarily placed in the storage slot.

When fully loaded, 144 ampoules with bundles of fuel rods are placed in the transport case entering the PSC. Since the capacity of known canisters is 30 or 31 ampoules with bundles of fuel rods, then, after four cases are fully loaded, only the remainder of 24 or 23 ampoules with bundles of fuel rods can be installed in the fifth canister. When unloading two transport covers, the remainder will be 18 or 17 ampoules with bundles of fuel rods, three transport covers - 12 or 11 ampoules with bundles of fuel rods, four - 6 or 5 ampoules with bundles of fuel rods, and only when unloading five transport covers all ampoules with bundles of fuel rods can be placed in 24 well-known pencil cases with a capacity of 30 ampoules without residue.

An incompletely loaded pencil case cannot remain in the socket of the camera picking case until the next transport cover arrives, since its location does not allow carrying out preventive work with the equipment of the camera picking case. Also, an incompletely loaded pencil case cannot be temporarily installed in the nests of the dry storage, since in this case it will be transported with a non-welded lid, which is unacceptable, since it drastically reduces the safety during transportation of spent nuclear fuel. Sealing incomplete cases using the established technology and installing them for permanent storage will lead to a decrease in the dry storage capacity.

If the remainder of the loaded ampoules not placed in the canisters is left in the transport case, the latter must be reinstalled in a protective container and stored until the next flight arrives, which impairs radiation safety and reduces the turnover of the transport and packaging set between the nuclear power plant and the dry storage.

The technical result that can be obtained by carrying out the invention is to increase the safety during overloading of ampoules with fuel rods by placing the remainder of the ampoules with fuel rods in a reversible case temporarily placed in the storage slot.

To achieve the specified technical result in a known case containing a housing with an annular groove made in it, vertical struts, a grid forming cells for accommodating ampoules with bundles of spent fuel elements with a given straightness, and a lid with a load-gripping device made on the lid in the form of a central fungus and duplicate gripping collar, a lock installed in the central fungus with the ability to hold the pencil case by introducing locking rods into the annular groove, is set lenches in the guides, the cover is mounted on a support flange attached to the body under the annular groove for welding, the closing rods are installed in the guides on the outer surface of the cover and connected to the lock, the upper surfaces of the annular groove and the closing rods are made at an angle not exceeding the angle of friction, and a hole is made in the lid, in which an aerosol filter is installed.

In addition, a gasket made of heat-resistant elastic material is installed between the flange and the cover.

In the particular case, the lock contains a sleeve with a screw installed in it, provided with a conical tip with T-grooves in the lower part, into which the ends of the locking rods are inserted with the profile corresponding to the shape of the grooves.

In another particular case, the vertical posts are installed in the housing between the support flange and the bottom of the pencil case, and the grill is made of tubular sleeves connected to the vertical posts, the flange and the plates with each other with the formation of round and triangular cells, the diameter of the inscribed circle of triangular cells being equal to the inner diameter round cells.

The installation of the cover on the support flange attached to the housing under the annular groove in welding, the installation of locking rods in the guides on the outer surface of the cover and their connection with the lock, the execution of the upper surfaces of the annular groove and locking rods at an angle not exceeding the angle of friction allows the annular groove of the locking rods not only connect the lid to the body of the pencil case, but also as a result of the interaction of the conical surfaces of the annular groove and the locking rods get the force its cover to the supporting flange, providing connections for leaks "support flange - a cover of" after its adhesion to the proposed housing canister during storage. In addition, the implementation of the upper surfaces of the annular grooves and the locking rods at an angle not exceeding the angle of friction, eliminates the movement of the locking rods during transportation of the proposed case. This allows you to load the rest of the ampoules with the fuel rods bundles into the proposed case, place it for temporary storage in the storage slot, return the proposed case to the CCP to replenish the remainder of the ampoules with the fuel bundles or use the remainder of the ampoules with the fuel rods for the full loading of the known cases. Thus, the proposed case allows you to use it as a working case with installation in storage sockets in the intervals between overloads of ampoules from transport cases into known cases and to increase radiation safety when loading ampoules with bundles of fuel rods.

The opening in the lid of the hole in which the aerosol filter is installed allows air to be vented through the filter during temperature expansion of the proposed reverse canister, eliminating the occurrence of excessive pressure in the canister, which creates a force that opens the connection “support flange - cover”, to further improve the tightness conditions of this connection, to exclude aerosol contamination of the storage slot during temporary storage of a revolving canister in it and, thereby, increase safety during overloading of ampoules with fuel rods .

The installation of a gasket made of heat-resistant elastic material between the support flange and the lid helps to seal the connection of the support flange-lid with less pressing forces.

The installation inside the central fungus of the lock containing the sleeve with a screw installed in it, provided with a conical tip with T-grooves in the lower part, into which the ends of the locking rods are inserted with the profile corresponding to the shape of the grooves, allows the screw to be moved during rotation of the sleeve and, due to interaction of the conical surfaces of the T-shaped grooves of the tip with the ends of the locking rods, to reciprocate the movement of the locking rods, introducing and removing them from the annular groove, providing ement and disengage the cover from the canister housing.

The implementation in the particular case of the lattice of the proposed pencil case of tubular sleeves connected to vertical posts, a flange and with each other with the formation of round and triangular cells with equal diameters of the inscribed circle of triangular cells to the inner diameter of the round cells, allows ampoules with bundles of fuel rods to be installed in round and triangular cells permissible directness and load the remainder of the ampoules with the fuel rods from the transport cover into the proposed case.

The proposed reverse storage case for spent nuclear fuel RBMK-1000 is illustrated by the drawings presented in figure 1 and figure 2.

Figure 1 shows a General view of the proposed pencil case in section;

figure 2 is a section aa in figure 1.

The proposed reverse case intended for temporary storage of the remainder of ampoules with fuel rods bundles (see FIG. 1) comprises a housing 1 with a flat bottom 2, to which a shock absorber 3 is attached. An annular groove 4 is made in the housing 1, below which a support flange is mounted for welding 5. The upper conical surface 6 of the annular groove 4 is made at an angle not exceeding the angle of friction of steel on steel, comprising 7 degrees. A cover 7 is mounted on the supporting flange 5 with a central fungus 8 and a backup gripping collar 9. A groove 10 is made on the lower surface of the cover 7, into which a gasket 11 is made of an elastic heat-resistant material. A hole 12 is made in the lid 7, in which an aerosol filter 14 is installed between the gaskets 13, which is pressed by the threaded sleeve 15 with the central hole 16. On the upper surface of the lid 7 in the guides 17, closing rods 18 are installed, the upper surfaces 19 of which are made at the same angle as and the upper conical surface 6 of the annular groove 4. In the central fungus 8, a sleeve 20 is installed, in which a screw 22 is installed on the thread 21, provided with a conical tip 23. In the conical tip 23 there are T-shaped grooves 24, in which the ends 25 of the locking rods 18 with the corresponding shape of the T-grooves are guided by the profile. A cross-shaped slot 25 is made on top of the sleeve 20. Vertical struts 26 are installed between the flange 5 and the flat bottom 2. A grill 27 is installed inside the housing 1. The grill 27 (see Fig. 2) is made of tubular sleeves 28 connected to the vertical struts 26, a flange 4 and between the plates 29 to form round 30 and triangular 31 cells, the diameter of the inscribed circle of the triangular cells 31 being equal to the inner diameter of the round cells 30.

The proposed reverse case, designed for temporary storage of the remainder of the ampoules with the bundles of fuel rods and serving as a safety tool, is operated as follows.

The proposed revolving pencil case is inserted into the control panel and installed in the loading slot. A Phillips screwdriver is inserted into the grip of the electromechanical non-copying manipulator, inserted into the Phillips 25 slot and the sleeve 20 is rotated. By rotating the sleeve 20, the screw 22 installed in it moves upward along the thread 21, while due to the interaction of the profiles of the ends 25 of the locking rods 18 and T-grooves 24 on the conical tip 23, the locking rods 18 move to the center of the lid 7 and exit the annular groove 4. The lid 7 is hooked by a crane using a central fungus 8 and a duplicate gripper shoulder 9 and is set aside. The ampoules remaining in the transport case with the bundles of fuel rods by the electromechanical non-copying bridge manipulator are installed in round 30 and triangular 31 cells of the grid 27. After the remainder of the ampoules with the bundles of fuel rods is placed in the proposed reverse case, the cover 7 with the manipulator 11 with the gasket 11 is mounted on the supporting flange 5. Further, by rotating the sleeve 20, the screw 22 installed in it moves down the thread 21, due to the interaction of the profiles of the ends 25 of the locking rods 18 and the T-grooves 24 on the conical at the end 23, the locking rods 18 are inserted into the annular groove 4. In this case, due to the interaction of the upper conical surface 6 of the annular groove 4 and the upper surfaces 19 of the locking rods 18 made at the same angle, a force arises, pressing the cover 7 with a heat-resistant elastic gasket 9 to the supporting the flange 5. This ensures not only a reliable connection of the cover 7 with the housing 1 of the pencil case, but also the tightness of the connection “supporting flange 5 - cover 7”, which allows the transportation of the reverse case, loaded of the remainder of the ampoules with bundles of fuel rods and the temporary storage in the storage slot.

Then, the proposed reverse case is hooked by a crane for a central fungus 8 and a duplicate gripping collar 9 and then, according to the existing transport scheme, is installed in the dry storage storage slot, where it is temporarily stored until the next reload. During temporary storage in the proposed reverse case due to the residual heat of the fuel bundles, an increase in air temperature occurs. The expanding air is discharged through an aerosol filter 14, which eliminates the overpressure in the reverse canister and aerosol contamination of the storage slot during temporary storage of the reverse canister.

At the next overload of ampoules with fuel rods bundles, the proposed case loaded with the previous remainder of ampoules with fuel rods bundles is delivered to the control panel and installed in the backup loading slot, where cover 7 is removed. Further actions with the remains of ampoules with fuel rods bundles in the proposed reverse case and transport case depend on the total number of ampoules with fuel rods in two residues.

If the total number of ampoules with bundles of fuel rods is equal to or greater than 30 ampoules, the ampoules with bundles of fuel rods are reloaded from the transport case and the proposed reverse case into a known case. Next, on the proposed working case with the remaining ampoules with the bundles of fuel rods, the lid 7 is again installed, and it is transported to the storage slot for temporary storage.

If the total number of ampoules with bundles of fuel rods is not enough until the known pencil case is fully loaded, then the ampoules with bundles of fuel rods are reloaded from the transport case into the proposed reverse case, with its subsequent installation in the storage slot for temporary storage.

Claims (4)

1. A reverse case for temporary storage of ampoules with bundles of fuel elements, comprising a housing with an annular groove made therein, vertical racks, a grid forming cells for accommodating ampoules with bundles of spent fuel elements with a given straightness, and a lid with a load gripping device made on the lid in the form central fungus and duplicate gripping collar, a lock installed in the central fungus with the ability to hold the pencil case by introducing locking rods into the annular groove installed in the guides and connected to the lock, characterized in that the cover is mounted on a support flange attached to the housing under the annular groove for welding, the closing rods are installed in the guides on the outer surface of the cover, the upper surfaces of the annular groove and the part of the closing rods introduced into it made at an angle not exceeding the angle of friction, and a hole is made in the lid in which an aerosol filter is installed. 2. A reversible pencil case for temporary storage of ampoules with bundles of fuel elements according to claim 1, characterized in that a gasket of a heat-resistant elastic material is installed between the flange and the lid. 3. A reversible case for temporary storage of ampoules with bundles of fuel elements according to claim 1, characterized in that the lock contains a sleeve inside the central fungus with a screw installed in it, provided with a conical tip with T-grooves in the lower part into which the ends are inserted trailing rods with a corresponding groove shape profile. 4. A reverse pencil case for temporary storage of ampoules with bundles of fuel elements according to claim 1, characterized in that the vertical posts are installed in the housing between the support flange and the bottom of the pencil case, and its grate is made of tubular sleeves connected to the vertical posts, the flange and the plates together with the formation of round and triangular cells, and the diameter of the inscribed circle of the triangular cells is equal to the inner diameter of the round cells.

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