RU2331943C1 - Hood for placement and storage of spent fuel assemblies of pwr 1000-type reactors - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention concerns storage facilities for spent nuclear fuel elements of pressurised water reactor PWR 1000 and can be applied in spent nuclear fuel storages at fuel reprocessing plants or nuclear power stations. The hood for placement and storage of spent fuel assemblies of PWR is made of stainless steel and includes a central tube, spacer grids and tubes for spent fuel assemblies. The distinguishing feature of the hood is that the spacer grids are square and have twenty holes for mounting of tubes where spent fuel assemblies will be placed, while the tube axes are positioned symmetrically against the central hood axis at points with definite polar coordinates of R_i and α_i.

EFFECT: increased revenue load factor for spent fuel assembly storage.

3 cl, 4 dwg

Description

The invention relates to nuclear engineering, in particular to means for storing spent nuclear fuel elements of a VVER 1000 reactor, and is intended for use in spent nuclear fuel storage facilities at such fuel recovery plants or at nuclear power plants.

Spent nuclear fuel storage is an essential part of any nuclear fuel cycle. This can be temporary storage until the spent nuclear fuel is reprocessed, or it can be stored for a sufficiently long time until the fuel is buried in the repositories. The total amount of spent fuel to be stored is continuously increasing due to the significantly lower production capabilities of the refineries. Not only the volume of stored fuel is growing, but the estimated storage periods are also increasing, since the task of disposing of spent nuclear fuel has not been solved in any country.

The core of Russia's nuclear power park is the VVER-440, VVER-1000 and RBMK reactors. For VVER-type reactors, the concept of a closed nuclear fuel cycle has been adopted. Spent nuclear fuel from nuclear power plants with VVER-440 reactors is reprocessed at the RT-1 plant, and the fuel of VVER-1000 reactors will be reprocessed at the RT-2 plant after it is put into operation. According to the “Strategy for the Development of Nuclear Energy in the First Half of the 21st Century," the creation of the RT-2 plant is planned for 2020-2025. On the RT-2 site, there is a storage facility for this fuel, where SNF is stored in a water-filled pool, the so-called “wet” storage. The reprocessing of spent reactor fuel at these plants is not yet planned, and its storage in safe conditions for a long time becomes an urgent problem, given the lack of free volumes in the reactor basins. Thus, the main storage practice for spent nuclear fuel in Russia today is storage.

The initial design capacity of the “wet” storage facility of 3,000 tons was increased to 6,000 tons due to the development and implementation of a twelve-seat storage case instead of the original

six-seater cover (in this case, not six spent fuel assemblies are placed in the cover, but twelve).

The prior art knows a device called a “Container for transporting spent fuel assemblies of the VVER-1000 reactor” (see USSR author's certificate No. 1653456, class G21F 5/00, 1989), which the applicant identified as the closest device of the same purpose to the claimed invention for the combination of features, and chose for the prototype. The well-known container for transporting spent fuel assemblies of the VVER-1000 reactor is made of stainless steel, contains a central pipe, spacer grids, as well as pipes for accommodating spent fuel assemblies.

The reasons that impede the achievement of the technical result indicated below when using the well-known container cover include the fact that the cover has a circular cross-section and when placing round covers in the storage it will be impossible to ensure complete and uniform filling of the storage with spent fuel assemblies. In addition, the cover contains only twelve pipes, which also does not provide full load storage. The use of hexagonal pipes in the design of the cover complicates the design of the cover and the technology of its manufacture due to the need to make hexagonal holes in the spacer grids, which leads to an increase in the cost of its manufacture.

The aim of the invention is to reduce the cost of manufacture and simplify the maintenance of the cover.

The technical result that can be obtained by carrying out the invention is to increase the payload coefficient of the storage for spent fuel assemblies.

In order to achieve the indicated technical result in a case for placement and storage of spent fuel assemblies of the VVER-1000 reactor made of stainless steel containing a central pipe, spacer grids and pipes for accommodating spent fuel assemblies, the feature is that the spacer grids are square and have twenty openings for installing pipes in which spent fuel assemblies are placed, and the pipe axes are symmetrically relative to the central axis and a cover at points with certain values of the polar coordinates R _i and α _i .

Given the special operating conditions, the cover is characterized in that the holes in the spacer grids and the pipes installed in them are made round, three ribs are installed in the upper part of the round pipes, forming an open hexagon and the cover along the periphery of the square section is framed by stiffeners symmetrically located relative to the central axis cover.

Distinctive features of the proposed cover from the above-mentioned known container closest to it are the increase in the capacity of the cover from twelve to twenty spent fuel assemblies, as well as the fact that the spacer grids are square and the axis of the pipes to accommodate the spent fuel assemblies are symmetrically relative to the central axis of the cover the points with defined polar coordinate values of the radii R _i and angles α _i. This technical solution allowed to increase the capacity of the cover, and, consequently, the entire storage.

Due to the presence of these signs during operation of the claimed cover under conditions when it is loaded and transported remotely under water, the arrangement of pipes and frames surrounding the cover along the square cross-section of the stiffeners symmetrically with respect to the central axis of the cover provides a uniform distribution of the hydrodynamic effect of water on the cover during transportation under water and eliminates its deployment in the transport corridor, which, in turn, allows the use of covers with spacing grids square section with a side of slightly less than the width of the corridor, but with a diagonal greater than its width. Stiffeners located symmetrically to the central axis of the cover made it possible to maintain its strength, despite the increase in the load factor of the cover.

When the applicant studied the distinguishing features of the described cover for the placement and storage of spent fuel assemblies of the VVER-1000 reactor, no similar known solutions were identified from the available patent and scientific and technical sources of information, characterized by features identical to all the essential features of this invention. As well as the applicant, the effect of the transformations provided for by the essential features of the claimed invention on the achievement of a technical result was not found.

The proposed cover for the placement and storage of spent fuel assemblies of the VVER-1000 reactor is illustrated by the drawings shown in figures 1, 2, 3 and 4.

Figure 1 shows a front view of the cover; figure 2 shows a top view of the cover; figure 3 and 4 illustrate the layout of the covers in the store.

The proposed cover for placement and storage of spent fuel assemblies of the VVER-1000 reactor contains a central pipe 1, spacer grids 2 attached to the central pipe 1 and pipes 3 (20 pieces) installed in them. A plate 4 and a base 5 connected to each other by ribs 6 are also connected to the central tube 1. The outer shell is surrounded by corners 7 and stiffeners 8 located symmetrically to the central axis. The distance grids 2 and the plate 4 are made square, with a square side smaller than the width of the storage transport corridor. The spacer grids 2 have twenty round holes 9 in which round pipes 3 are mounted, the axes of which are symmetrical to the central axis of the cover. In the upper part of the round pipes 3 there are three ribs 10 forming an open hexagon.

The axis of the pipes 3 are located at points with nominal polar coordinates, where

R _i is the nominal value of the polar radius for the i-th pipe in units of side A of the square cross section of the cover;

α _i - nominal value of the polar angle for the i-th pipe .:

R _i αI R _i αi R ₁ = 0.1758, α ₁ = 0 ° R ₁₁ = 0.1758, α ₁₁ = 180 ° R ₂ = 0.4069, α ₂ = 15 ° R ₁₂ = 0.4069, α ₁₂ = 195 ° R ₃ = 0.2952, α ₃ = 45 ° R ₁₃ = 0.2952, α ₁₃ = 225 ° R ₄ = 0.5138, α ₄ = 45 ° R ₁₄ = 0.5138, α ₁₄ = 225 ° R ₅ = 0.4069, α ₅ = 75 ° R ₁₅ = 0.4069, α ₁₅ = 255 ° R ₆ = 0.1758, α ₆ = 90 ° R ₁₆ = 0.1758, α ₁₆ = 270 ° R ₇ = 0.4069, α ₇ = 105 ° R ₁₇ = 0.4069, α ₁₇ = 285 ° R ₈ = 0.2952, α ₈ = 135 ° R ₁₈ = 0.2952, α ₁₈ = 315 ° R ₉ = 0.5138, α ₉ = 135 ° R ₁₉ = 0.5138, α ₁₉ = 315 ° R ₁₀ = 0.4069, α ₁₀ = 165 ° R ₂₀ = 0.4069, α ₂₀ = 345 °

The relative values of the polar radius R _i associated with the absolute R _{d the} ratio of R _d = R _i × A.

The range of permissible values of polar coordinates is determined by the distances between the axes of the pipes, the smallest of which exceeds the minimum permissible distance by nuclear safety conditions.

Cover for the placement and storage of spent fuel assemblies of the VVER-1000 reactor is operated as follows.

Spent fuel assemblies (SFA) in the transport container enter the receiving compartment of the storage, where they are underwater reloaded from the transport container into the tubes 3 of the cover. Then the loaded covers from the SFA are transferred to the pool 11 and then along the transport corridor 12 and the slotted floor 13 are fed to the storage location.

Thus, the above information indicates that when using the claimed cover, the following set of conditions:

- means embodying the claimed invention, - a cover for placing and storing spent fuel assemblies of the VVER-1000 reactor during its implementation, is intended for use in industry, namely in nuclear, in spent nuclear fuel storage facilities at spent fuel recovery plants or at nuclear power plants.

- for the claimed case in the form described in the independent clause of the claims, the possibility of its implementation using the means and methods described in the application is confirmed;

- a device - a cover for the placement and storage of spent fuel assemblies of the VVER-1000 reactor, embodying the invention, when implemented, is able to achieve the achievement of the technical result perceived by the applicant.

Claims (3)

1. A cover for the placement and storage of spent fuel assemblies of the VVER-1000 reactor, made of stainless steel and containing a central pipe, spacer grids and pipes for accommodating spent fuel assemblies, characterized in that its spacer grids are square and provided with twenty holes for installing pipes in which the spent fuel assemblies are located, and the pipe axes are located symmetrically with respect to the central axis of the sheath at points with nominal polar values coordinates: R _i α _i R _i α _i R ₁ = 0.1758, α ₁ = 0 ° R ₁₁ = 0.1758, α ₁₁ = 180 ° R ₂ = 0.4069, α ₂ = 15 ° R ₁₂ = 0.4069, α ₁₂ = 195 ° R ₃ = 0.2952, α ₃ = 45 ° R ₁₃ = 0.2952, α ₁₃ = 225 ° R ₄ = 0.5138, α ₄ = 45 ° R ₁₄ = 0.5138, α ₁₄ = 225 ° R ₅ = 0.4069, α ₅ = 75 ° R ₁₅ = 0.4069, α ₁₅ = 255 ° R ₆ = 0.1758, α ₆ = 90 ° R ₁₆ = 0.1758, α ₁₆ = 270 ° R ₇ = 0.4069, α ₇ = 105 ° R ₁₇ = 0.4069, α ₁₇ = 285 ° R ₈ = 0.2952, α ₈ = 135 ° R ₁₈ = 0.2952, α ₁₈ = 315 ° R ₉ = 0.5138, α ₉ = 135 ° R ₁₉ = 0.5138, α ₁₉ = 315 ° R ₁₀ = 0.4069, α ₁₀ = 165 ° R ₂₀ = 0.4069, α ₂₀ = 345 °, where R _i is the nominal value of the polar radius for the i-th pipe in units of side A of the square cross section of the cover, and α _i is the nominal value of the polar angle for the i-th pipe. 2. The cover according to claim 1, characterized in that the holes in the spacer grids and the pipes installed in them are made round, and in the upper part of the round pipes there are three ribs forming an open hexagon. 3. The case according to claim 1, characterized in that along the periphery of the square section, it is framed by stiffeners located symmetrically with respect to the central axis of the case.

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