RU2540975C1 - Device for collection of spilt spent nuclear fuel pellets - Google Patents

Abstract

FIELD: power industry.

SUBSTANCE: invention refers to devices for safety ensuring devices when transferring spent fuel assemblies of a VVER 1000 reactor from transport covers to storage covers and is intended to be used in water-filled storages of spent nuclear fuel as an emergency tool. A collection device of spilt spent nuclear fuel pellets includes a bar in the lower part of which a provision is made for a collector with an open lower part in which a soft elastic material is arranged, above which a displacer is installed, which is connected to a stock located inside the bar. In the displacer there are holes in which holders included in the soft elastic material are installed with a gap and attached to the collector. Scriptural plasticine is used as a soft elastic material. A net incorporated into the soft elastic material is attached with threads to the holders in the lower part. Total breaking force of threads does not exceed movement force of the displacer with the stock. The lower surface of the soft elastic material is located above the lower end face of the collector by 0.2-0.3 of diameter of a pellet at collection of non-destructed pellets and flush with the lower end face of the collector at collection of the destructed ones.

EFFECT: improvement of the device.

5 cl, 3 dwg

Description

The invention relates to nuclear engineering, in particular to means for ensuring safety when reloading spent fuel assemblies of the VVER 1000 reactor from transport covers to storage covers, and is intended for use in water-filled spent nuclear fuel (SNF) storage facilities at such fuel recovery plants or at nuclear power plants .

The core of Russia's nuclear energy park is the VVER-1000 and RBMK reactors. For VVER-type reactors, the concept of a closed nuclear fuel cycle has been adopted. Spent nuclear fuel (SNF) of the VVER-1000 reactors will be reprocessed at the SNF reprocessing plant after its commissioning. According to the "Strategy for the Development of Nuclear Energy in the First Half of the 21st Century", the creation of such a plant is planned for 2020-2025. At the site of the Isotope-Chemical Plant of the Federal State Unitary Enterprise Mining and Chemical Combine there is a storage facility for this fuel, where the spent fuel of VVER 1000 reactors is stored in a water-filled pool, the so-called “wet” storage facility. Spent nuclear fuel enters the receiving pool in a transport case loaded into the protective container, from which spent fuel assemblies (SFA) are loaded into storage covers in the overload compartment of the water-filled pool, which are stored in the SFA storage pool from the overload compartment.

SFAs are transferred from transport covers to storage covers using a well-known device - a P-type rod, drawing K.7050.00.000 developed by the Federal State Unitary Enterprise Mining and Chemical Combine, which contains a rod that is hung on a hook of a lifting device, in the lower part of which there is a gripper for coupling the rod with the SFA, lifting it from the transport case and reloading it into the storage case. The capture is made in the form of a cylindrical sleeve with a bayonet connection with a hooked SFA, in the form of two parallel grooves for the entry of the SFA fixing elements (dowels or pins) and two 45 samples offset with grooves for accommodating the SFA fixing elements. A rod is placed inside the rod, in the lower part of which a stop is installed, and in the upper part the rod is threadedly installed in the bevel gear of a bevel gear with a handle. SFA transshipment operations are carried out from a mobile platform installed above the transhipment compartment filled with water.

The known device operates as follows.

The operator captures the rod above the head of the SFA located in the transport case so that the locking elements are placed under two parallel grooves on the capture. Then the rod is lowered until the fixing elements are placed in the capture sample and rotated by 45 °, while the fixing elements on the SFA head are placed above the groove of the bayonet coupling connection. Further, the rod rises, and by rotating the handle of the manual bevel gear, the rod is lowered until the stop mounted on the lower part of the rod touches the end surface of the SFA head, fixing the SFA in the grip, after which the SFA is removed from the transport case and reloaded into the storage case.

The disadvantage of this device is that when SFA is overloaded with its use, there is a possibility of a SFA falling and spills of spent nuclear fuel pellets of uranium dioxide spilling to the bottom of the pool. To carry out the collection of spills of tablets known device is not possible.

A safety analysis showed that when SFA is overloaded, there is a possibility of it falling and spilling fuel with a mass of about 13.2 kg of uranium dioxide to the bottom of the pool. Fuel, uranium dioxide or a mixture of uranium dioxide and gadolinium trioxide, when scattered, are in the form of tablets, which are cylinders with a diameter of 7.53 mm and a height of 10.7 mm. The depth of the pill spill at the bottom of the pool is 13.4 m from the slotted overlap of the pool, and the pill spill must be collected under a layer of water without removing the pill from the pool.

Closest to the claimed device by the totality of signs is a device for collecting spills of spent nuclear fuel, comprising a receiving basin, a movable platform with a running gear installed above the receiving basin, a lifting device, a protective cup having a cavity open from the side of the pool, and a grip mounted in the cavity protective glass. A protective cup is attached to the bottom of the boom mounted on the lifting device. The gripper is equipped with a rod with a reciprocating motion of the rod, placed in the cavity of the protective glass, and the gripping legs cover the fungus of the collector made in the form of a hollow parallelepiped. Two scraper with fingers are mounted on the axes of the collector on the axes, and a collector scraper drive with a reciprocating rod connected to the scrapers by articulated rods through bushings mounted with a clearance from above on the fingers of the scrapers of the collector is attached to the protective cup.

In addition, the protective cup is made in the form of two flat parallel plates connected by jumpers, and the gripper contains two horizontal and vertical links articulated to each other, with vertical links mounted in the protective cup on the fixed axis, and horizontal links mounted on the movable axis, located in the grooves of the plates of the protective glass. The cross section of the fungus and the claw legs are square. Pneumatic cylinders are used as capture and collection drives with a reciprocating rod movement, connected by tubes with manual pneumatic distributors installed on the upper end of the rod.

A disadvantage of the known device is that after filling the collection with tablets, they remain stored in the collection, and the next collection is attached to the known device. In the future, it will be necessary to use another device for unloading from collection of tablets for recycling.

Also in the event of the destruction of part of the tablets, the collection of their small parts by a known device is practically impossible.

The known device is used as an emergency tool. The presence of the drives at the capture and collection with the reciprocating movement of their rods requires maintaining the known device in working condition for the long-term operation of the "wet" SNF storage, which leads to additional costs. So when storing the device, it is necessary to remove its lower part from the pool with pneumatic cylinders and store it separately from the rod.

In addition, defective SFAs, in particular after a fall, are placed in a well-known case intended for storage until processing (see RF patent No. 2477899).

When storing defective SFAs in it, there is also the possibility of spilling of spent fuel pellets on the bottom of the cells of a well-known case, which is practically impossible to remove from the cells with a known device.

The problem to which the invention is directed, is to expand the functionality of the device for collecting tablets from the bottom of the pool, and from the bottom of the cell cover, designed to store defective SFA.

The technical result that can be obtained by carrying out the invention consists in pressing and fixing the tablets and their parts in a soft elastic material.

To achieve the specified technical result in a device for collecting spills of spent nuclear fuel pellets containing a receiving basin, a movable platform with a running gear installed above the receiving basin, a lifting device with a rod mounted on its hook, at the end of which a collection is fixed, the collection is made with the bottom open in which soft elastic material is placed. Above the soft elastic material in the collector there is an ejector attached to a rod located inside the rod.

Holes are made in the ejector, in which holders are mounted with a gap and are attached to the collector and are included in soft elastic material.

In the particular case of execution, a gasket is installed between the ejector and the soft elastic material, which has low adhesion to the ejector material, for example a plastic film, and sculptural plasticine is used as the soft elastic material.

In another particular case of execution, a mesh is attached to the holders in the lower part, embedded in a soft elastic material, and the total breaking strength of the threads does not exceed the force of movement of the ejector rod.

In another particular case of execution, the lower surface of the soft elastic material is located 0.2-0.3 times the diameter of the tablets above the lower end of the collection.

In another particular case of execution, the lower surface of the soft elastic material is flush with the lower end of the collector.

Running the collector with the bottom open and installing soft elastic material in it allows you to press and fix the tablets in a soft elastic material and place them in a special container installed near the tablet spill when installing the collector on the tablet spill.

The installation in the collector above the soft elastic material of the ejector and its attachment to the rod located inside the rod allows you to move the soft elastic material with the tablets pressed into it when moving the rod with the ejector attached to it.

The holes in the ejector and the mounting of holders attached to the collection with the gap included in the soft elastic material allow you to first fix the soft elastic material in the collection holders, and then when moving the ejector to ensure the release of the soft elastic material with the holders and thereby unload it from the collection along with tablets pressed into it.

The installation between the ejector and the soft elastic material of the gasket, which has low adhesion to the material of the ejector, such as a plastic film, eliminates the sticking of the soft elastic material to the ejector and ensures that the soft elastic material falls out when it leaves the collector.

The use of sculpted plasticine as a soft flexible material, having high adhesion between the layers, allows filling the collection layer by layer and obtaining a smooth surface for pressing tablets.

Attaching to the holders in the lower part with a mesh of fibers embedded in a soft elastic material allows reinforcing its tensile strength and, after pressing tablets with high density into it, prevents the soft elastic material weighted by tablets from falling out when the collector is lifted.

The total breaking strength of the threads does not exceed the force of movement of the ejector rod by the rod, when unloading, it breaks the threads that fasten the mesh to the holders and unload soft elastic material together with the mesh and tablets pressed into it.

The location of the lower surface of the soft elastic material above the lower end of the collector by 0.2-0.3 tablet diameters allows the tablet to be pressed into the soft elastic material until it comes into contact with the bottom of the pool and the particles of soft elastic material adhere to the bottom when the collector is placed on a spill of tablets.

The location of the bottom surface of the soft elastic material flush with the lower end of the collector allows you to squeeze them into the soft elastic material when installing the collector on the bottom of the compartment after collecting spills of tablets in the event that small parts of crushed tablets are found on the bottom of the compartment.

The proposed device for collecting spills of tablets of spent nuclear fuel is illustrated by the drawings presented in figure 1, figure 2 and figure 3.

Figure 1 shows the proposed device located in the receiving pool;

figure 2 - the proposed device in the context;

figure 3 - the proposed device in the context of when unloading.

The proposed device (see Fig. 1) is located in the receiving pool 1 (SFA overload compartment) and is serviced with a movable platform 2 with a running gear installed above the receiving pool 1. The proposed device comprises a rod 4 mounted on a hook of a lifting device (crane) 3 with a rod 5 located inside it. The rod 4 is provided with a flange 6, to which a collector 8 with an open bottom is attached with bolts 7. Inside the collector 8 (see FIG. 2), a pusher 9 is installed over its entire area, provided with a pin 10 connected to the rod 5 by means of a pin 11, and the pin 11 is located opposite the holes 12 made in the rod 4 with the upper position of the pusher 9. B collector 8 under the ejector 9 through a strip 13 of plastic film, placed soft elastic material 14, which is used as a sculptural clay. Openings 15 are made in the ejector 9, in which holders 16 are attached to the collector 8 and included in the soft elastic material 14. The net 18 is attached to the holders 16 with threads 17, embedded in the soft flexible material 14, and the total breaking strength of the threads does not exceed the force moving the ejector 9 by the rod 5, carried out manually. The lower surface 19 of the soft elastic material 14 is located above the lower end 20 of the collection 8 by 0.2-0.3 tablet diameters.

In the upper part of the rod 4, longitudinal grooves 21 are made, in which there are handles 22 attached to the rod 5. In the upper part of one of the longitudinal grooves 21, a latch 23 of the handle 22 and the rod 5 and the ejector 9 connected to it are installed in the upper position. To collect a scattering of tablets from the bottom of the cell cover, designed to store defective SFAs, the collection 8 is made round with a diameter that allows you to lower it to the bottom of the cell. To collect a pill placer from the bottom of the overload compartment, the collector 8 can be made of any shape based on the possibility of unloading soft elastic material 14 with the tablets into a special container (not shown in the drawings) located in the pool near the tablet spill.

The proposed device for collecting spills of tablets is used as an emergency tool and is operated as follows.

The collection 8 and the ejector 9 are disconnected from the rod 4 and the rod 5 by unscrewing the bolts 7 and removing the pin 11, respectively. A gasket 13 is laid on the ejector 9 and the side walls of the collector 8 and the collector 8 is filled with a layer of soft elastic material 14.

A grid 18 is attached to the holders 16 with threads 17 and a second layer of soft elastic material 14 is applied, and its lower surface 19 should be located under the lower end 20 of the collector 8 at a distance of 1.5-2 mm, which is 0.2-0.3 tablet diameter . The equipped collector 8 with the ejector 9 is connected to the rod 4 and rod 5 by setting the bolts 7 and the pin 11, respectively. In this case, using the lock 23, the handle 22 is fixed in the upper part of the groove 21, and the rod 5 and the ejector 9 connected to it are in the collector 8 also in the upper position.

The proposed device is lowered by a crane to the bottom of the receiving pool 1 and using a movable platform 2 is placed above the spill of tablets at the bottom of the overload compartment or above the cell cover designed to store defective SFA, which is delivered to the receiving pool 1. By moving the lifting device 3 rod 4 with the collector 8 is lowered onto a spill of tablets, which are pressed into a soft elastic material 14. Next, with a lifting device 3, the collector 8 is placed above a special container for storing tablets and explosives ditsya in his neck.

Unloading soft elastic material 14 with tablets pressed into it (see figure 3) is as follows.

The retainer 23 is removed and the handles 22 are moved along the longitudinal grooves 21 down together with the rod 5 and the ejector 9 connected to it. In this case, the ejector 9 discharges soft elastic material 14 with tablets pressed into it, the mesh 18 and the gasket 13 from the collection 8, breaking the threads 17 securing the mesh 18 to the holders 16, as a result of which it falls into a special container. Further, the operations of collecting tablets continue in a similar manner until the complete collection of spills of tablets.

After collecting the tablets, in the case of parts of crushed tablets at the bottom, the soft elastic material 14 is placed in the collector 8 so that its lower surface 19 is flush with the lower end 20 of the collector 8. Moreover, to prevent the soft elastic material 14 from sticking to the bottom of the compartment, as a soft elastic material 14 is applied sculptural clay with reduced stickiness. The collection of parts of the crumbled tablets and the unloading of soft elastic material 14 with the parts of the crumbled tablets is carried out similarly to the collection of tablets and unloading of the soft elastic material 14 with tablets.

Claims (5)

1. A device for collecting a spill of tablets of spent nuclear fuel, comprising a receiving basin, a movable platform with a running gear mounted above the receiving basin, a lifting device with a bar mounted on its hook, at the end of which a collection is fixed, characterized in that the collection is made with the bottom open in which soft elastic material is placed, over which a pusher is installed in the collector, attached to a rod located inside the rod, holes are made in the pusher, in which tanovleny with a gap secured to the collection holder entering into a soft elastic material. 2. The device according to claim 1, characterized in that a gasket is installed between the ejector and the soft elastic material, which has low adhesion to the ejector material, for example a plastic film, and sculptural clay is used as the soft elastic material. 3. The device according to claim 1, characterized in that to the holders in the lower part of the threads is attached a mesh embedded in a soft elastic material, and the total breaking strength of the threads does not exceed the force of movement of the ejector rod. 4. The device according to claim 1, characterized in that the lower surface of the soft elastic material is located above the lower end of the collection by 0.2-0.3 tablet diameters. 5. The device according to claim 1, characterized in that the lower surface of the soft elastic material is flush with the lower end of the collection.

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