RU2325715C2 - Removable head of nuclear reactor fuel assembly - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: removable head of the nuclear reactor fuel assembly is attached to the upper ends of absorber rod guiding channels (1) and contains clamping plate (2) and guide bushings (6). Bushings (6) pass through holes in clamping plate (2) and are equipped with stops (9), internal ledges (10), and coupling components. Stops (9) are installed above clamping plate (2). Internal ledges (10) mate the ends of guiding channels (1). The coupling components are designed as collets (11). The collets interact with guiding channels (1) and are locked with locking components. The locking components are designed as sleeves (17). Support components (15) are installed coaxially to guide bushings (6). The support components interact with springs (16). The springs compress clamping plate (2) to stops (9). Support components (15) are rigidly connected to sleeves (17). The sleeve skirts interact with the external surfaces of collets (11). The lower ends of the collets have collars (13). The collars interact with the lower ends of sleeves (17).

EFFECT: invention aims at increase in fuel assembly reliability and increase in nuclear reactor safety margins.

2 cl, 2 dwg

Description

Technical field

The invention relates to nuclear energy, and more specifically to fuel assemblies of nuclear reactors with water under pressure.

State of the art

Known removable head fuel assembly (patent No. 2212065, priority 09.09.2001) of a nuclear reactor (prototype), including a pressure plate, guide bushings passing through holes in the pressure plate. The guide sleeves are equipped with stops mounted above the pressure plate, internal ledges that are joined to the ends of the guide channels, and coupling elements made, for example, in the form of collets, hooked onto the said guide channels and lockable locking elements. Moreover, the said guide bushings are provided with external protrusions with supporting elements mounted on them, interacting with springs, pressing the pressure plate to the stops. The supporting elements are rigidly connected to blocking elements made in the form of sleeves, the skirts of which interact with the outer surfaces of the collets.

A disadvantage of the known fuel assembly is the presence of radial play in the collet joints with the guide channels, which can lead to rotation of the axis of the head relative to the axis of the fuel assembly and, accordingly, to a decrease in the stability of the fuel assembly during longitudinal-transverse loading during operation. Such a decrease in stability leads to the formation in the active zone of increased gaps between the fuel assemblies. And the increased gaps between the fuel assemblies lead to local changes in the water-uranium ratio and, accordingly, to local bursts of energy release in the fuel assemblies. In practice, this can lead to local overheating of the fuel elements or to failure to fulfill the conditions for safe operation of the core.

Disclosure of invention

The aim of the invention is to increase the reliability of the fuel Assembly and increase reserves to ensure the safety of a nuclear reactor.

The objective of the invention is to eliminate the possibility of tilting the axis of the removable head relative to the axis of the fuel assembly.

The technical result of the invention is the exclusion of radial backlash in the connection of the collets with the guide channels of the fuel assembly.

The achievement of the objective of the invention is ensured by the fact that the removable head of the fuel assembly of the nuclear reactor, mounted on the upper ends of the guide channels of the absorbing rods, contains a pressure plate, guide bushings passing through the holes in the pressure plate, equipped with stops mounted above the pressure plate, internal ledges that are joined with the ends of the guide channels, and the coupling elements, made in the form of collets, hooked on the said guide channels and locked by locking elements, you olnennymi in the form of sleeves, wherein said guide sleeve coaxially mounted support members, cooperating with springs that urge the presser plate towards the stop and is rigidly connected to the sleeve, the skirt of which interact with the outer surfaces of the collets. New is that at the lower ends of the collets are made collars that interact with the lower ends of the sleeves.

In addition, according to the invention, the surface of the collars interacting with the lower ends of the liners is made conical.

With such a device, the detachable head of the collet is crimped and radial play between them and the guide channels is eliminated. And the absence of backlash ensures the alignment of the removable head and the fuel assembly.

Brief Description of the Drawings

The invention is illustrated by drawings, on which:

figure 1 is a vertical section of a removable head fuel assembly of a nuclear reactor;

figure 2 is a vertical section of the node connecting the collet with a guide channel.

Embodiments of the invention

The removable head of the fuel assembly (8) of the nuclear reactor is mounted on the upper ends of the guide channels (1) of the absorbing rods and contains a pressure plate (2). The guide bushings (6) pass through the holes (7) in the pressure plate (2) and are equipped with stops (9) installed (for example, by welding) above the pressure plate (2). The guide bushings (6) are joined with the ends of the guide channels (1) with their inner ledges (10) and in their lower part have coupling elements in the form of collets (11), which engage, for example, over the shoulders (12) of the guide channels (1). Collets (11) can be made, for example, in the form of pipes with vertical slots and internal annular grooves. And on the supporting elements (15), the lower ends are supported by the springs (16) installed coaxially with the guide bushings (6), on which the pressure plate (2) is supported. Supporting elements (15) can be made, for example, in the form of truncated cones (for streamlining in the coolant flow). The supporting elements (15) are also rigidly connected to the locking elements locking the collets (11), and together they are sleeves (17), the skirts of which interact with the outer surfaces of the collets (11). The lower ends of the sleeves (17) are rested against the shoulders (13) made at the lower ends of the collets (11). The surface of the shoulders (13), into which the lower ends of the collets (11) are abutted, can be made conical.

Additionally, a protective-guiding device (3) can be installed on the removable head, which is pressed by at least one spring (4) through the support element (14), mounted on the protective-guiding device (3), to the central pipe (18) . The upper end of the spring (4) rests against the pressure plate (2). The protective-guiding device (3) is held by couplers (5) at a distance from the pressure plate (2), not more than specified. Ties (5) can be made, for example, in the form of studs mounted on the adapter plate, with nuts above the pressure plate. The protective-guiding device (3) can be made of a plate with protective guides fixed on it in the form of a perforated conical shell or in the form of inclined ribs.

The removable head of the fuel Assembly of a nuclear reactor is as follows.

The springs (16), abutting against the pressure plate (2), press the sleeves (17) against the shoulders (13). The interaction forces of the sleeve (17) with the shoulders (13) are directed downward. Since the vectors of these efforts do not lie on the axis of the collet (11), bending moments are created on the petals of the said collet, causing the collet petals to bend in the direction of the axis until the petals are pressed against the guide channel (1). If the collar surface (13) interacting with the lower end of the sleeve (17) is conical, then in addition to the moment, a force will appear on each petal of the collet (11), pressing the petal against the guide channel (1).

During transportation, the fuel assembly is suspended using the technological capture of the reloading machine by the removable head. In this case, the guide bushings (6), coupled by coupling elements in the form of collets (11) to the collars (12) on the guide channels (1), are suspended on the pressure plate (2) using the stops (9). The springs (16) are pressed from above through the supporting elements (15) of the sleeve (17), holding their skirts in a working position in which they block the collets (11) from disengaging from the shoulders (12) in the upper part of the guide channels (1).

A fuel assembly with a detachable head installed in a nuclear reactor is pressed by the internals of the nuclear reactor so that the springs (16) receive additional elastic working deformation. In this case, the force that keeps the blocking elements - sleeves (17) - from rising, increases, providing reliable retention of the blocking elements - sleeves (17) and guide sleeves (6) from the ascent in the coolant flow.

In the case of installing a protective-guiding device, the spring (4) and couplers (5) allow the protective-guiding device (3) to be moved down by the amount of the detachable head pressed by the internals of the nuclear reactor. And if the stop (14) interacting with the end of the central pipe (18) is installed on the protective-guiding device (3), the downward movement of the said protective-guiding device is limited.

The coolant enters the fuel assembly (1) from below and, having removed thermal energy from it, exits through the protective-guiding device (3) of the removable head. In this case, on the elements of the removable head, in particular on the protective-guiding device (3), buoyancy forces are created from the pressure drop on these elements. At least one spring (4) counteracts these pushing forces. However, for individual transient operating modes of a nuclear reactor, depending on the flow rate of the coolant, the ratio of the spring force (4) and the total buoyant force on the protective-guiding device (3) may change, as a result of which the specified protective-guiding device (3) may undergo vibration. Since the cross section of the sleeves (17) is much smaller than the area of the protective-guiding device (3), then much less hydrodynamic forces from the coolant side are realized on the sleeves (17). The springs (16) provide sufficient force for the complete absence of movement of the sleeves (17) relative to the collets (11) under the action of the coolant flow, which excludes the possibility of fretting wear of the collets (11).

To dismantle the removable head, the device according to patent No. 2075118, which raises the protective-guiding device (3), can be used. Rising, the plate of the protective-guiding device (3) abuts against the radial protrusions (19) of the sleeves (17) and moves the sleeves (17) upward, compressing the springs (4) and (16). Sleeves (17) are moved to a height sufficient to release the collets (11) from blocking. After that, by lifting the removable head, the collets (11) are disengaged from the shoulders (12) of the guide channels (1) and the head can be removed from the fuel assembly. Ties (5) ensure the integrity of the removable head in the dismantled state, that is, they hold the protective-guiding device (3) on the removable head.

To install the removable head on the fuel assembly (1), the removable head compressed using the above-mentioned device is installed with collets (17) until it stops at the ends of the guide channels (1). Then, the preload of the springs (4) and (16) is weakened by the indicated device, while the protective-guiding device (3), as well as the supporting elements (15) with sleeves (17) are moved downward by the action of the springs (4) and (16) and the collets (12) are locked in the engaged position for the collars (2) of the guide channels (1). And the abutment of the ends of the sleeves (17) in the collars (13) of the collets (11) ensures that the petals of the said collets are pressed against the guide channels (1).

Thus, the proposed solution for the removable head of the fuel Assembly of a nuclear reactor have significant differences and technical advantages compared with the prototype. By introducing the proposed solutions, an increase in the reliability of the fuel assembly is achieved by eliminating radial backlash in the connection of the removable head to the fuel assembly. And this, in turn, eliminates the inclination of the axis of the head relative to the axis of the fuel assembly, which increases its stability during longitudinal-transverse loading in the active zone of a nuclear reactor. Ultimately, increasing the stability of the fuel assembly leads to the exclusion of the formation of increased gaps between the fuel assemblies, in which increased energy release can occur, which results in an increased margin for ensuring the safety of the nuclear reactor.

Industrial applicability

It is most expedient to use the proposed solutions for operation in water-cooled nuclear power reactors.

Claims (2)

1. The removable head of the fuel assembly of the nuclear reactor, mounted on the upper ends of the guide channels (1) of the absorbing rods, containing a pressure plate (2), guide bushings (6) passing through holes in the pressure plate (2), equipped with stops (9), mounted above the pressure plate (2), internal ledges (10), joined with the ends of the guide channels (1), and coupling elements made in the form of collets (11), hooked onto the said guide channels (1) and locked by locking elements made in sleeve form (17), moreover, coaxially referred to guide bushings (6), support elements (15) are installed, interacting with springs (16), pressing the pressure plate (2) to the stops (9), and rigidly connected to sleeves (17), the skirts of which interact with the outer surfaces of the collets (11), characterized in that at the lower ends of the collets are made collars (13), interacting with the lower ends of the sleeves (17). 2. The removable head of the fuel assembly of a nuclear reactor according to claim 1, characterized in that the surface of the collars (13) interacting with the lower ends of the liners (17) is made conical.

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