RU2785581C1 - Case for vver fuel elements - Google Patents

Abstract

FIELD: nuclear engineering.

SUBSTANCE: invention relates to nuclear engineering, in particular to means for transporting and storing spent fuel elements (fuel rods) of a VVER reactor, and more specifically to means for transporting and storing leaky VVER fuel rods. The case for VVER fuel elements contains a cylindrical body with a bottom, a removable plug isolated from the internal volume of the vessel, cooling tubes passing through the tube plates of the canister, a guide, which is a hexagonal pipe, and safety valves in the bottom and plug. A sealed disk with a safety valve separates the lower and upper volumes of the canister. In the canister there are cells for fuel elements, which are thin-walled tubes with perforation, a plug at the bottom and a localizing device at the top. The localization node is the fuel rod head.

EFFECT: reducing the release of radioactive elements into the environment when handling leaky fuel.

3 cl, 4 dwg

Description

The invention relates to nuclear engineering, in particular to means for transporting and storing spent fuel elements (fuel rods) of a VVER reactor, and more specifically, to means for transporting and storing leaky VVER fuel rods.

The fuel assembly (FA) of a VVER reactor consists of a bundle of fuel elements, guide channels, a head and a liner. The fuel rods, made in the form of rods, are fixed in the lower and several spacer grids. In the course of VVER operation, leakage of zirconium fuel rod claddings is possible. To detect fuel assemblies containing leaky fuel elements, a number of methods are provided for monitoring the tightness of fuel claddings in an operating and shutdown reactor. Further operation of fuel assemblies with leaking fuel elements leads to the release of radioactive elements into the coolant, while at the same time, the termination of the operation of fuel assemblies, before the design level of burnup is reached, entails economic losses.

At nuclear power plants (NPPs) with VVER, devices are used to repair fuel assemblies. The principle of repair consists in removing the fuel assembly head, extracting the leaking fuel element, installing a fuel element simulator in its place, and installing the fuel assembly head in its original place. At the same time, a storage place for a leaky fuel element must be provided, with the possibility of its control and extraction.

Known from the prior art is a “Container for transporting and storing irradiated fuel rods, defective fuel rods and/or rods of defective fuel rods” (RF patent No. for fuel rods, moreover, the receiving basket is assembled by means of plug-in connections from light metal absorbing neutron plates and the assembled light metal plates form receiving shafts in which metal sleeves are fitted. At least one metal sleeve is used as a cup body for direct placement of defective fuel rods and/or rods of such fuel rods.

A device is known for packaging leaky nuclear fuel rods for transportation and long-term storage or warehousing (US patent No. 8130895 (B2), G21C 19/00, G21C 19/26, G21F 5/008, publ. a support structure that repeats the shape and size of the fuel assembly with end elements, in which capsules are located for accommodating leaky fuel rods, the capsules are closed on both sides with plugs.

The disadvantage of the design of the container and the device is that in order to control nuclear materials, the location of the damaged fuel, it is necessary to open the sleeve/capsule, while the release of radioactive elements into the environment is possible.

Known for Westinghouse Quiver (Quiver System for Storing Failed Fuel Rods. YouTube [online] [video]. WestinghouseNuclear, June 22, 2017 [retrieved 2021.09.02]. Found at <https://www.youtube.com/watch?v= SNtszjtYKzc>), which contains a frame with tubes installed inside it, a seal and a cover. Damaged fuel elements are placed in the tubes, the tubes are separated by spacer grids. The cover is installed with a screw connection. The Westinghouse Quiver provides sealed storage for damaged fuel and can be easily re-opened for inspection, inventory, or examination of rods in the fuel pool or hot cell.

The closest device to the claimed invention, in terms of the totality of features, is the "Case for leaky fuel elements" (Terms of Reference for the supply of non-standard technological equipment / product and / or system of the Balakovo Nuclear Power Plant branch of Rosenergoatom Concern JSC) Storage of Leaky SFAs from VVER-1000 Reactors, Rosenergoatom Concern JSC, Balakovo NPP, 2018.04.06 [retrieved 2021.09.02] Found in <http://zakupki.rosatom.ru/1805160608329>; stand for the inspection and repair of fuel assemblies. Materials of the 18th international scientific and technical conference of young specialists in nuclear power plants, OKB "GIDROPRESS", Podolsk, 2016), containing a cylindrical body with a bottom, a removable plug isolated from the internal volume of the vessel, cooling tubes, passing through the tube boards of the canister, the guide, which is a hexagonal pipe and safety valves in bottom and cork. In the inner space there is a receiving basket for fuel rods, made in the form of a block of pipes with spacer and support grids.

A common disadvantage of the well-known designs of Westinghouse Quiver and the "Case for Leaky Fuel Elements" is that when these devices are opened, with leaky fuel rods located in them, radioactive elements in the internal volume of the devices can escape into the working environment in which the operation takes place. Taking into account the fact that the depressurization of fuel rods at VVER is mainly of a single nature, it is assumed that the devices are periodically opened / closed to load leaky fuel rods for a long time until the device is filled.

The objective of the invention is to develop a canister design for storage and transportation of defective (leaky) fuel rods, which will make it possible to place individual VVER fuel rods. In this case, isolation from the environment of leaking fuel elements and visual control of the location of the fuel elements in the canister, when it is opened, must be ensured.

The technical result consists in reducing the release of radioactive elements into the environment when handling leaky fuel.

The specified technical result is achieved by the fact that in a canister containing a cylindrical body with a bottom, a removable plug isolated from the internal volume of the vessel, cooling tubes passing through the tube boards of the canister, a guide, which is a hexagonal pipe and safety valves in the bottom and plug, it is proposed to place sealed disk with a safety valve separating the lower and upper volume of the canister. It is proposed to place cells for fuel elements in the canister, which are thin-walled tubes with perforation, a plug at the bottom and a localizing device at the top. Cells for fuel elements are fixed by a localizing device in a compacted disk. When the plug is open, the cavities of empty cells with open localizing devices are in contact with the upper volume of the canister, which makes it possible to install fuel rods in them. After installing the fuel rod and closing the localizing device, the upper volume of the canister is cut off and a perforation in the cell tube opens, connecting the cell cavity with the lower volume of the canister, providing additional cooling and pressure reduction in the cells. Thus, the medium in contact with the place of depressurization will be localized in the lower volume of the canister. At the same time, one of the elements of the localization unit will be the fuel rod head, which will provide visual control of the location of the fuel rods when the canister is opened.

The claimed invention is illustrated by the drawings shown in Fig. 1-4:

fig. 1 - general view of the canister for VVER fuel elements;

fig. 2 - localizing device of the canister for VVER fuel elements (the collet tip is open) (fragment A of Fig. 1);

fig. 3 - localizing device of the canister for VVER fuel elements (the collet tip is closed) (fragment A of Fig. 1);

fig. 4 - the location of the valves in the canister for VVER fuel elements (fragment B of Fig. 1).

The patented canister for VVER fuel elements contains a cylindrical body 1 with a bottom 2, cooling tubes 3 isolated from the internal volume of the vessel, passing through the tube sheets 4 of the canister, a cover made of neutron-absorbing material 5, a sealed plug 6 with a load gripping element 7, a sealed disc 8. disk 8 divides the inner cavity of the canister into upper 9 and lower volume 10. Cells for fuel rods 11 with localizing devices 12 are located in the canister.

Cells for fuel elements 11 are thin-walled tubes 13 with perforation 14 and a locating device at the top 12. Cells for fuel elements 11 are fixed by a locating device 12 in a sealed disk 8. The locating device 12 consists of a collet tip 15, a nut 16 and a bushing 17. device 12 (collet tip 15 is open), the leaky fuel element 18 is installed in the cell for fuel elements 11, while the upper volume 9 of the canister is combined with the internal cavity of the cell for fuel elements 11. The nut 16 has a threaded connection with the sleeve 17. Due to the rotation of the nut 16, vertical movement is carried out sleeve 17, due to this, the collet tip 15 is closed, while the head of the leaky fuel element 18 becomes part of the localizing connection. When the sleeve 17 is moved, perforation 14 opens on the tube of the cell for fuel elements 13, providing communication of the working medium inside the cell for fuel elements 11 with the lower volume 10 of the canister .

The sealed plug 6 seals the internal volume of the canister. The valves 19 located in the sealed disk 8 and the sealed plug 6 open when the internal pressure exceeds the set value. In the bottom 2 there is a valve 20, which opens when the internal pressure drops below the set value.

Claims (3)

1. A canister for VVER fuel elements, containing a cylindrical body with a bottom, a removable plug isolated from the internal volume of the vessel, cooling tubes passing through the tube plates of the canister, a guide, which is a hexagonal pipe, and safety valves in the bottom and plug, characterized in that that a compacted disk is installed in the canister to divide the internal cavity of the canister into upper and lower volumes, cells for fuel elements with a localizing device are fixed in the disk. 2. The canister according to claim 1, characterized in that after the fuel element is installed in the cell for the fuel element, in the case of closing the locating device, the fuel element head becomes one of the elements of the localization unit. 3. The canister according to claim 1, characterized in that after the fuel element is installed in the fuel element cell, in case of closing the locating device, the perforation in the fuel element cells is opened, providing communication of the working medium inside the fuel cell cell with the lower volume of the canister.

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