RU2248631C1 - Nuclear reactor fuel assembly - Google Patents

Abstract

FIELD: nuclear power engineering; fuel assemblies for pressurized-water reactors.

SUBSTANCE: proposed nuclear reactor fuel assembly has bottom nozzle, guide channels secured on the latter, bundle of fuel elements mounted in spacer grids, and top nozzle. The latter has sleeve with bottom, shield grid with guide members, and plate, all joined together, with guide channels running through them. Supporting members rest on projections made in guide channels. Springs are inserted between supporting members and sleeve bottom abutting against top stops secured on upper ends of guide channels. Guide members of shield grid are joined to sleeve for relative vertical displacement. Downward movement of shield grid is limited by bottom stops mounted on guide channels and its upward movement is limited by supporting members.

EFFECT: enhanced reliability of fuel assembly.

1 cl, 3 dwg

Description

Technical field

The invention relates to nuclear energy, and more particularly to fuel assemblies for nuclear pressurized water reactors.

State of the art

Known fuel assembly of a nuclear reactor [1], containing a bunch of fuel elements with spacer grids, the lower and upper end parts connected to each other by guide channels. The upper end part contains interconnected glass, plates, a protective grill and guides made in the form of a perforated conical shell, as well as springs that press at the top of the bottom of the glass to the upper stops at the upper ends of the guide channels and resting below on supporting elements made in the form of bushings mounted on the protrusions of the guide channels.

The known assembly has insufficient reliability associated with reduced stability due to the need to have an increased clearance between the ends of the fuel elements and the protective grill. The size of this gap for fuel assemblies is determined by the elongation of the fuel elements, and for a known fuel assembly it should be increased by the total stroke of the springs to prevent damage to the fuel elements by the protective grill. The section between the ends of the fuel elements and the protective grill has a reduced bending stiffness with respect to the beam of the fuel elements and the upper end part. An increase in its height significantly reduces the stability of the fuel assembly and can lead to increased bends of the guide channels and to increase friction when moving the absorbing rods in the guide channels.

Disclosure of invention

The aim of the invention is to increase the reliability of the fuel Assembly. The objective of the invention is to reduce the height of the section with reduced bending stiffness.

The technical result of the invention is to increase the bending stiffness of the fuel assembly.

This goal is achieved by the fact that in the fuel assembly of a nuclear reactor containing a shank, guide channels fixed to the shank, a bundle of fuel elements installed in the spacer grids, as well as a head containing a glass with a bottom, a protective grid with guide elements and a plate connected to each other penetrated by guide channels, as well as supporting elements based on protrusions made on the guide channels, springs located between the supporting elements and the bottom of the Akana, abutting against the upper stops fixed on the upper ends of the guide channels, new is that the connection of the guiding elements of the protective grill with the glass is made with the possibility of relative vertical movement, and the movement of the protective grill down is limited by the lower stops installed on the guide channels, and up - supporting elements.

Such a solution of the problem posed allows one to significantly reduce the necessary gap between the ends of the fuel elements and the protective grid and to significantly increase the bending stiffness of the section between the ends of the beam of the fuel elements and the protective grid, as well as the fuel assembly as a whole.

Brief Description of the Drawings

The invention is illustrated by drawings, on which

figure 1 is a vertical section of a fuel assembly, in which the protective lattice rests on the lower stops, made in the form of at least one guide channel;

figure 2 is a vertical section of a fuel assembly, in which the protective lattice rests on the lower stops, made in the form of protrusions on the guide channels;

figure 3 is a vertical section of a fuel assembly, in which the protective lattice rests on the lower stops, made in the form of rings mounted on the lower ends of the support elements passing through the protective lattice.

Embodiments of the invention

The fuel assembly contains a shank (1) on which guide channels (2) and a bundle of fuel elements (3) combined by spacer grids (4) are mounted, as well as a head (5). The head (5) contains a glass (6) pierced with guide channels (2) with a bottom (7), a protective grill (8) with guide elements (9), a plate (10), rigidly connected to the glass (6). The supporting elements (11) mounted on the protrusions (12) on the guide channels (2) serve as a support for the springs (13), abutting the upper ends in the bottom (7) of the glass (6) and pressing the said glass to the upper stops (14), fixed on the upper ends of the guide channels (2). The upper stops (14) can be made in the form of rings or nuts attached to the upper ends of the guide channels (2), or in the form of collets coupled to the guide channels and provided with an upper outer collar. The connection of the guide elements (9) of the protective grill (8) with the glass (6) is made with the possibility of relative vertical movement, for example, in the form of a cylinder, a coaxial glass (6). The protective grill (8) rests on the lower stops (15), made, for example, in the form of a central guide channel. From above, the protective grill abuts against the lower ends of the supporting elements (11).

Alternatively, the protective grill (8) rests on the lower stops (15), made, for example, in the form of protrusions on the guide channels (2), and the lower ends of the support elements (11) limit the movement of the protective grill (8) upward.

Alternatively, the protective grill (8) rests on the lower stops (15), made, for example, in the form of rings mounted on the lower ends of the support elements (11) passing through the protective grill (8). The upward movement of the protective grill (8) is limited by protrusions on the support elements (11).

The operation of the fuel Assembly is as follows. When assembling a nuclear reactor, the heads of the fuel assemblies are pushed from above by an intracase device. In this case, the glass (6) is lowered together with the plate (10), compressing the springs (13). The downward movement of the protective grill (8) is limited by the lower stops in the form of at least one of the guide channels (2), or protrusions on the guide channels (2), or rings attached to the lower ends of the support elements (11). The upward movement of the protective grill (8) is limited either by the lower ends of the spring-loaded support elements (11), or by protrusions on the support elements passing through the protective grill. In this case, the gap between the ends of the beam of fuel elements (3) and the protective grill remains unchanged and can only be selected from the condition of ensuring free elongation of the fuel elements under the influence of operating temperature and radiation.

During the operation of a nuclear reactor, the coolant enters through the shank (1) into a bundle of fuel elements (3), where it carries out heat removal and then leaves through the head (5) to the upper chamber of the reactor.

Thus, an increase in the bending stiffness of the section between the ends of the bundle of the fuel elements and the protective grill and the fuel assembly as a whole is ensured, increased deformation of the guide channels is eliminated, which reduces friction when moving the absorbing rods in the said guide channels, and therefore, the reliability of the fuel assembly is increased.

Industrial applicability

It is most appropriate to use the proposed solutions for fuel assemblies of nuclear power reactors with pressurized water.

Sourse of information

1. Auth. testimonial. SU No. 708830 A.

Claims (1)

A fuel assembly of a nuclear reactor comprising a shank (1), guide channels (2) fixed to the shank (1), a bundle of fuel elements (3) installed in the spacer grids (4), and a head (5) containing a cup (6) with a bottom (7), a protective grill (8) with guide elements (9) and a plate (10) connected to each other and pierced by guide channels (2), as well as supporting elements (11), based on the protrusions (12), made on the guide channels (2), springs (13) located between the supporting elements (11) and the bottom (7) with takana (6), abutting against the upper stops (14), mounted on the upper ends of the guide channels (2), characterized in that the connection of the guide elements (9) of the protective grill (8) with the glass (6) is made with the possibility of relative vertical movement, moreover, the movement of the protective grill (8) downwardly is limited by the lower stops (15) mounted on the guide channels, and upwardly by the support elements (11).

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