JPH01189593A - Fuel support for fast breeder reactor - Google Patents

Abstract

PURPOSE:To intend an improvement of safety, by making a hook placed at an end of a working arm so as to fit with a groove dug to an entrance nozzle when a fuel assembly is placed completely at its final position, as the entrance nozzle is being inserted into a connection pipe. CONSTITUTION:When an entrance nozzle 4 is inserted into a connection pipe 3, a lower part of a working arm 5 is pushed downwardly and the arm 5 is made to rotate around a rotating axis 6. At a situation where a fuel assembly is placed completely at its final position, a hook 7 placed at an end of the arm 5 is fitted into a groove 8 of the nozzle 4. An axis 6 is supported by an axis hole 9 drilled into a connection pipe 3, and by using a material which has a higher thermal expansion rate than that of a material for the connection pipe 3, as the material for the axis 6, the axis 6 and the axis hole 9 is close fitted during a nuclear reactor is operated (at a higher temperature condition) therewith a rotation of the arm 5 is restricted. Consequently, an upward movement of the fuel assembly is restricted. Also, the arm 5 and a stopper 10 which is fixed to the connection pipe 3 are connected with a spring mechanism 11, and during a refueling (at a lower temperature condition), a righting force works on the arm 5, the hook 7 is unlatched from the groove 8 and the fuel assembly can be withdrawn.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a fuel support device for a fast breeder reactor.

(Prior Art) A reactor core in a fast breeder reactor has a large number of hexagonal fuel assemblies arranged in a core barrel. As shown in FIG. 6, each fuel assembly 1 is supported by an entrance nozzle 4 at the bottom of the fuel assembly inserted into a connecting pipe 3 fixed to a core support plate 2. , is not constrained in the vertical direction at all.

(Problems to be Solved by the Invention) In the support method described above, when vertical seismic motion is applied to the reactor core, the fuel assembly may vibrate or float up and down. After surfacing again.

When falling, an impact load will be applied to the core support plate.

The present invention has been made in view of the above circumstances, and prevents the fuel assembly from vertically vibrating and floating when it is grounded, and reduces the shock load applied to the core support plate. The aim is to provide highly safe nuclear reactors.

[Structure of the invention]

Means for Solving Problem C11) In the present invention, when the entrance nozzle at the lower part of the fuel assembly is inserted into the connecting pipe and supported, the operating arm, which is pushed by the lower end of the entrance nozzle and rotates, is attached to the side wall of the connecting pipe. When the fuel assembly is installed in I'm restrained.

(Function) According to the present invention, during reactor operation (at high temperatures), the rotating shaft, which is the center of rotation of one operating arm, tightens with the bearing hole of the connecting pipe due to thermal expansion. This restricts the rotational movement of the operating arm.

Since the movement of the entrance nozzle is restrained by the claw at the tip of the operating arm, upward movement of the fuel assembly can be restrained.

In addition, the actuating arm and the stopper fixed to the connecting pipe are connected by a spring mechanism, so that during fuel exchange (at low temperatures), the rotating shaft is free to rotate, and the fuel assembly is moved upward. In conjunction with the movement, a restoring force is obtained in the operating arm 5, and the claw at the tip of the operating arm is removed from the groove. Therefore, at low temperatures, the fuel assembly can be freely pulled out from the connecting pipe.

(Example) Hereinafter, an example according to the present invention will be described in detail with reference to the drawings. 1 to 5 show an embodiment of the present invention in longitudinal section and partial cross section. FIGS. 1 and 2 show the entrance nozzle 4 inserted into the connecting pipe 3. The state before the tip of the nozzle 4 contacts the actuating arm 5 is shown. Furthermore, when the entrance nozzle 4 is inserted, it is necessary to press the lower part of the operating arm 5 from above.
The actuating arm 5 begins to rotate around the rotation axis 6. As shown in FIGS. 3 and 4, when the fuel assembly 1 is completely seated, the claw 7 at the tip of the operating arm 5 fits into the groove 8 provided in the entrance nozzle 4. .

The rotating shaft 6 is supported by a bearing hole 9 provided in the connecting pipe 3, and is made of a material with a higher coefficient of thermal expansion than that of the connecting pipe. (At high temperatures), there is an interference fit between the rotating shaft 6 and the bearing hole 9, and the rotational movement of the actuating arm 5 is restricted. Therefore, upward movement of the fuel assembly is restricted. Furthermore, a spring mechanism 11 connects between the actuating arm 5 and a stopper lO fixed to the connecting pipe 3.
Since it is free to rotate, a restoring force acts on the actuating arm 5,
As the entrance nozzle 4 moves upward, the pawl 7 disengages from the groove 8 and the fuel assembly can be pulled out.

The circumferential arrangement and number of the operating arms 5 and grooves 8 described above are arbitrary. Furthermore, if it is desired to have a degree of freedom in the horizontal angle when loading the fuel assembly, the width of the groove 8 may be increased.

FIG. 5 shows another embodiment. The basic structure and principle are the same as the above embodiment, but the difference is that the spring mechanism connecting the operating arm and the stopper is replaced with one operating arm 5. A counterweight 12 is attached to the opposite end of the claw 7.

Thereby, even when the actuating arm 5 stands upright, a state can be created in which the center of gravity of the entire actuating arm is always outside the vertical line passing through the rotation axis. Therefore, when the operating arm is free to rotate at low temperatures, a restoring force due to gravity acts on the operating arm, and in conjunction with the upward movement of the entrance nozzle 4, the claw 7
It deviates from the

〔Effect of the invention〕

According to the fuel support device for a high-speed bed reactor of the present invention, the fuel assembly is restrained from vertical movement during reactor operation (at high temperatures), and even if vertical seismic motion is applied to the reactor core, Vertical vibration and lifting of the fuel assembly can be prevented,
A highly safe core with a relatively simple structure that satisfies earthquake resistance in the vertical direction can be created.

Furthermore, during fuel exchange (at low temperatures), the vertical restraints are released and the fuel assembly can be freely pulled out from the core.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a main part showing an embodiment of the present invention. FIG. 2 is a view taken along arrow AA in FIG. 1. FIG. 4 is a view taken along the arrow AA in FIG. 3, FIG. 5 is a longitudinal cross-sectional view of another embodiment of the present invention, and FIG. 6 is a cross-sectional view showing the supporting state of a conventional fuel assembly. . DESCRIPTION OF SYMBOLS 1... Fuel assembly, 2... Core support plate, 3... Connecting pipe. 4... Entrance nozzle, 5... Operation y-, t-
, h6... Rotating shaft %7... Claw, 8... Groove% 9.
...Bearing hole, 10...Stopper, 11...Spring mechanism, 12...Counterweight. Figure 1 Figure i2 Figure 7 Figure 5 Figure 6

Claims (4)

[Claims] (1) In the connecting pipe that supports the fuel assembly of a fast breeder reactor at its lower end, an operating arm is installed that is pushed and rotated by the entrance nozzle when the entrance nozzle is inserted into the connecting pipe, so that the fuel assembly is completely A fuel support device for a fast breeder reactor, characterized in that, in a seated state, a claw at the tip of an operating arm fits into a groove provided in an entrance nozzle. (2) By making the material of the rotating shaft, which is the center of rotation of the operating arm, a material with a higher coefficient of thermal expansion than that of the connecting pipe, during reactor operation (at high temperatures), the bearings on the rotating shaft and connecting pipe side 2. The fuel support device for a fast breeder reactor according to claim 1, wherein the operating arm is tightly fitted to the hole and rotational movement of the operating arm is restricted. (3) The fuel for the fast breeder reactor according to claim 1, characterized in that the operating arm has a structure in which a restoring force is obtained by coupling the operating arm and the stopper fixed to the connecting pipe with a spring mechanism. Support device. (4) The fuel support system for a fast breeder reactor according to claim 1, wherein a restoring force due to gravity is applied to the operating arm by adding a counterweight to the operating arm.