JPS6115394B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Control rods for fast reactors are required to also have a scram function due to safety concerns. Therefore, a vibration isolation mechanism is required that prevents vibrations of the control rods due to fluid, etc., and does not affect the scram time. The present invention relates to a control rod for a fast reactor that has an improved vibration isolation mechanism.

During reactor operation, the control rods are withdrawn and stopped in the middle of this guide tube. In this case, the coolant for cooling the control rods flows from below the control rods to above. At this time, vibrations occur due to this fluid, and it is thought that the flow rate is large and the gap between the guide tube and control rod vibrates. Therefore, in order to suppress fluctuations in the reactor's output, it is necessary to reduce this gap.However, since the control rods also have a scram function at the same time as controlling the reactor's output, this function requires that the gap be made smaller. There is a need. Therefore, a control rod equipped with a rotary anti-vibration mechanism is used to satisfy both functions.

As mentioned above, this vibration isolation mechanism is made of a rotating mechanism to prevent fluctuations in output due to fluid vibration and at the same time to less likely affect scram time. Therefore, they can be broadly classified into ball type and roller type.

These characteristics have the drawback that the ball type makes point contact with the mating guide tube, so the surface pressure is approximately one order of magnitude higher than that of the roller type, and the mating guide tube is easily damaged. On the other hand, the roller type has a drawback that although the surface pressure is low, the structure is complicated because it consists of a pin and a roller, and the pin part is thin and hard, so it is more easily damaged than the ball type.

In order to eliminate the drawbacks of the above-mentioned prior art, the present invention has the following features:
It is an object of the present invention to provide a control rod for a fast reactor that minimizes damage to a mating guide tube and prevents damage to a guide roller pin portion, which is a vibration isolation mechanism, and increases reliability.

The present invention will be described in detail below with reference to the drawings of one embodiment.

Figure 1 shows an overall view of the control rod. In this figure, 11
is the control rod. Reference numeral 13 denotes a control rod guide tube, which serves as a guide when the control rod 11 is withdrawn, stopped, inserted, and scrammed. Further, 14 is a handling head, which is fastened to the control rod drive mechanism during reactor operation. Reference numeral 15 denotes a shock absorber, which is a device for stopping the control rod 11 so that it is not subjected to excessive impact when the control rod 11 is scrammed. 12 is a rotary vibration isolator which has a vibration isolating function when the control rod is withdrawn, and is used to prevent the scram time from increasing during the scram.

Next, details of this vibration isolation mechanism according to the present invention are shown in FIG. The rotary vibration isolator 12 is composed of 31 rollers, a support base 32 for supporting the rollers, and bolts 33 for attaching the rollers to the control rod 11, and in order to reduce damage to the mating guide tube 13. The curvature of the roller 31 is matched to the vicinity of the curvature of the mating guide tube.

In the above configuration, the control rod 11 moves up and down along the guide tube 13 during shim operation and scram operation. At this time, the roller 31 interferes with the mating guide tube 13 while rotating. In addition, during a scram, since a large speed is applied due to the scram impact force, the mating guide tube 13 is passed through the roller 31.
The impact force exerted on it also becomes considerably large. However, since the curvature of the roller 31 is matched to that of the mating guide tube 13 to minimize damage caused by this impact force, an increase in surface pressure can be prevented. Further, as another embodiment of the roller 31, the shape shown in FIG. 3 is also conceivable.

As explained above, the roller of the present invention can be manufactured to have the same curvature as the mating guide tube during the control rod shim and scram operations, so the surface pressure is small and damage to the mating guide tube can be minimized. As a result, the reliability against damage to the vibration isolating mechanism is greatly increased, and at the same time, damage to the mating guide tube can be minimized. Therefore, a control rod for a fast reactor that is stable for power control and scram functions can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view showing the overall structure of a fast reactor control rod and guide tube of the present invention, FIG. 2 is an explanatory view showing the structure of the vibration isolation mechanism of FIG. 1, and FIGS. FIG. 3 is a perspective view showing another embodiment of the roller shown in FIG. 2; 11...control rod, 12 ...rotary vibration isolator, 3
1...roller, 32...support stand, 33...bolt.

Claims (1)

[Claims] 1. A control rod for a fast reactor that has a handling head formed at its upper end and moves up and down in a guide tube to perform output control and scram functions. This rotary vibration isolator is installed on the side wall of the control rod, and is composed of a spindle-shaped roller section and a support base that supports both ends of the roller section, and the curvature of the side surface of the roller section is adjusted to match the curvature of the inner surface of the guide tube. A fast reactor control rod characterized by: