RU2298848C1 - Fuel assembly - Google Patents

Abstract

FIELD: core members of nuclear reactors using liquid-metal primary coolant.

SUBSTANCE: proposed nuclear-reactor core fuel assembly has fuel elements, bottom and top spacer grids, splinting wire, and hexagonal tube with bottom nozzle. The latter has outer thread on its cylindrical part and is provided with hold-down nut. Bottom spacer grid is provided with perforated thrust ring and is split through height into two parts joined together. Slots are milled in bottom part of spacer grid along hole axes to pass fuel element splinting wire.

EFFECT: enhanced manufacturability and operating reliability.

1 cl, 2 dwg

Description

Technical field

The invention relates to the elements of the active zone of a nuclear reactor, mainly with a liquid metal coolant of the primary circuit.

State of the art

The known design of the fuel assembly (FA) in the active zone of a nuclear reactor (VVER active zones for nuclear power plants. Authors: V.D.Shmelev, Yu.G. Dragunov and others. FSUE OKB "GIDROPRESS", Moscow 2004, p. 27), consisting of a bunch of fuel rods fixed in the upper and lower gratings. Outside, the fuel assembly is covered with a hexagonal pipe fastening the upper and lower lattices. In the lower lattice along the axis of the holes in which the tips of the fuel rods are installed, there are through holes for the cotter pin, through which the fuel rods are mounted. To do this, holes for the cotter pin are also drilled in the tips of the fuel rods. In the upper part of the fuel assembly there is a head with a gripping device, in the lower part there is a shank with a damping device. The head and shank are rigidly interconnected by a hex pipe.

The disadvantage of this design is the great complexity and complexity of manufacturing the lower lattice, associated with a large number of through holes of small diameter for the cotter pin, as well as the lack of alignment of uneven flow along the height of the active zone due to the outer shelling of the fuel assemblies.

This design of fuel assemblies is the closest technical solution known and therefore adopted as a prototype.

Disclosure of invention

The objective of the invention is to improve the manufacturability of the structure and increase the reliability of its work.

The technical result of the invention is the reliable fixation of the fuel rods in the lower lattice, as well as the lattice itself on the shank of the fuel assembly.

This is achieved by the fact that the lower grill has a height connector, and in its lower part there are grooves along the axes of the holes into which the tips of the fuel rods are inserted and secured with a cotter pin, and the shank has an external thread on its cylindrical protruding part and is equipped with a clamping nut, using which tightly connects both parts of the lower lattice during assembly, and also provides reliable fixation of the position of the lower lattice on the shank of the hexagonal pipe, taking into account the locking of the nut with the help of rki.

Brief Description of the Drawings

The invention is illustrated by drawings, which represent the following:

Figure 1 is a longitudinal section of a fuel assembly;

Figure 2 - section aa.

Figure 1 shows the fuel rods 1, the upper lattice 2, the lower lattice, consisting of two parts 3 and 4 in height with a stop ring 5, cotter pin 6, hexagonal pipe 7 with collet shank 8, thread 9 and clamping nut 10.

Figure 2 shows the lower part of the lattice 4, cotter pin 6, grooves 11.

The implementation of the invention

The invention allows to ensure high manufacturability of fuel assembly, as well as the reliability of its work.

A fuel assembly consists of fuel rods fixed in the upper and lower grids, and the fuel rods are fixedly fixed in the lower grid, and the fastening is made along the sliding fit, which provides thermal expansion during operation. In the central part of the fuel assembly there is a hexagonal pipe fastening the upper and lower lattices. At the bottom, the pipe passes into a collet shank, the cylindrical part of which has a protrusion, with the help of which an emphasis is made in the lower grate. In turn, the lower grill consists of two parts in height. In the lower part of the said lattice there is a persistent perforated ring, and along the axes of the holes into which the tips of the fuel rods are mounted, grooves for the cotter pin are milled, by means of which the fuel rods are fastened, which is technologically a fairly simple operation. The tips of the fuel rods also have holes for the cotter pin. The collet shank of the hexagonal pipe has an external thread in its cylindrical part and is equipped with a clamping nut. During assembly, a small gap is provided between both parts of the lower lattice, which makes it easy to fix the fuel rods using splint wires inserted into the grooves of the lattice and the holes in the ends of the fuel rods. Then the clamping nut is tightened, locked on the shank by welding, and the lower grill itself is scalded around the perimeter at the connector. The absence of an external hexagonal pipe and the presence of a thrust ring perforated by holes make it possible to ensure uniform flow rate for each fuel assembly due to the transverse mixing of the coolant flow, thereby contributing to an increase in the reliability of its operation.

Claims (1)

A fuel assembly of the core of a nuclear reactor containing fuel rods, lower and upper lattices, a cotter pin, a hexagonal pipe with a shank, characterized in that said shank has an external thread in its cylindrical part and is equipped with a clamping nut that secures the lower lattice, and the lower lattice itself equipped with a perforated thrust ring and consists in height of two parts bonded to each other, and in the lower part along the axes of the holes grooves are cut for the cotter pin velov.

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