JPS58161882A - Fast breeder reactor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a fast breeder reactor in which the reactor output can be normally controlled even when an earthquake occurs.

[Technical background of the invention]

Conventionally, a tank-type rapid breeder reactor as shown in Figure 1 has been used. In the figure, 1 is a reactor vessel, and this reactor vessel 1 is filled with liquid sodium 2, which is a coolant. Nine, a reactor core 3 is configured within this reactor vessel 1,
It also houses the upper core machine #I4, primary coolant pump 5, intermediate heat exchanger 6, etc. And this reactor vessel 1
The upper part of the tank is sealed with a roof slab 7 as an upper shield, and a cover gas is sealed between the roof slab 1 and the liquid level of the liquid sodium 2. A control rod drive mechanism 8 is supported at the center of the roof slab 1. The control rod drive mechanism 8 includes a drive section on the roof slab, an upper guide tube 12 on the lower surface of the roof slab, and an extension tube IS. The control rod drive mechanism 8 controls the reactivity of the core 3 by inserting and withdrawing the control rods 10 into and out of the core 3. The control rods 10 are classified into main reactor shutdown control rods and backup reactor shutdown control rods according to their functions, and the main reactor shutdown control rods are partially inserted into the reactor core 3 during normal operation. The control rods for controlling the reactivity and for stopping the backup reactor are fully inserted into the reactor core J during scram, but here we will only discuss the control rods for stopping the main reactor.

As shown in FIG. 2, a lower guide tube 1 into which control rods 10 are inserted is inserted into the core fuel 9 disposed in the center of the reactor core 3.
1... is provided. The control rod drive mechanism 8... has extension tubes IJ vertically disposed within the upper guide tube 12 supported by the roof slider f1, and extends from each extension tube 11 side. The control rod 10...
The device is configured to be inserted or pulled out.

[Intermediate point of background technology]

The conventional fast breeder reactor had the following problems.

In other words, this is true for fast breeder reactors in general, but especially for tank-type fast breeder reactors, the reactor vessel 1 is large because the primary coolant Imp 5, intermediate heat exchanger 6, etc. are housed in the reactor vessel 1. The roof sura suddenly takes shape and acts as an upper covering body! 1 also has a large diameter. Therefore, in the event of an earthquake, the amplitude and period of the reactor vessel 1 and the roof slide! There will be a large difference between the amplitude and period of 1. Therefore, as shown in FIG. 3, it is expected that the roof slab 1 will float 9 higher than the reactor vessel 1 and the distance in the vertical direction from the control rod drive mechanism 8 will increase. In such a case, all the control rods 10 will move in the withdrawal direction with respect to the reactor core 3, and a positive reactivity will be inserted into the reactor core 3, causing a sudden increase in reactor power.

Therefore, the control rods 10 may not be able to properly control the reactor output, and there is a risk that a severe thermal load will be applied to the reactor core 3.

[Purpose of the invention]

An object of the present invention is to provide a fast breeder reactor in which the reactor output can be normally controlled even if the relative position between the control rod drive mechanism and the reactor core changes due to earthquake vibrations or the like.

[Invention 0IIEIE] In the fast breeder reactor system of the present invention, the control rod drive mechanism is provided at the lower part of the reactor core and supported by nine core support plates, and a bellows mechanism is provided between the control rod drive mechanism and the upper shield. The control rod drive mechanism and the upper shield are designed to maintain airtightness and to be freely displaceable.

[Embodiments of the invention]

Embodiments of the present invention will be explained with reference to FIGS. 4 to 8.
Figure 4 shows the general configuration of a tank-type fast breeder reactor. In the figure, 14 is a reactor vessel, and this reactor vessel 14 is filled with liquid sodium 16, which is a coolant. There is.

Further, within this reactor volume 1) J4, nine reactor cores 16 are configured supported on a core support plate 16A, and a core upper mechanism 1
1, a secondary coolant pump, an intermediate heat exchanger 19, etc. are accommodated. The upper part of this reactor vessel 14 is sealed with a roof slab 20 as an upper shield.
A cover gas is provided between the roof slab 20 and the liquid level of liquid sodium II. A control rod drive mechanism U... is provided in the center of the roof slab xoq), and this control rod drive mechanism 111-1 is supported by a core support plate ighK. As shown in FIG. 5, the control rod drive mechanism 21 includes a drive section 21, a guide tube 23, an extension tube 24, a latch mechanism 26 for holding the control rod 2J, and a control rod 25.
is moved up and down within the extension tube 24, and the control rod drive mechanism 1
When removing the unit from the core 16, the latch mechanism is released and the control rod 1s is closed and shut.

/ y ) l j B.

The guide tube 21 is fixed to the lower surface of the drive section 22, passes through the core fuel 22, and accommodates a 24° elongated tube control rod 25 therein. A through hole 21 is provided in the center of the guide tube 23, and the guide tube 23 is configured to allow a coolant to flow therein. On the inner surface of the lower end of the guide tube 23, a plurality of engaging claws 28 as an attachment/detachment mechanism shown in FIG. 6 are fixed at equal intervals in the circumferential direction. It is supported in a detachable manner. The engaging claw sr' is made of spring steel such as Inconel, and engages with the engaging groove 28 provided in the core support plate 16m, and is activated by an external force to push or pull out the entire service guide tube 23 during attachment/detachment. It is configured to contract in the inner diameter direction and float when attached and detached. (9) A bellows mechanism 29 is provided between the outer periphery of the drive section z2 and the roof slab 220) to maintain airtightness and to ensure that the control rod drive mechanism L and the roof slab 20 are relative to each other. It is configured to be movable.

The above configuration has the following effects. In the unlikely event that
When an earthquake occurs, the roof slab 20 and the reactor vessel 14 vibrate violently, and the roof slab 2o lifts up from the reactor vessel 14, as shown in Figure 8, compared to Figure 7, which shows a normal state. It is expected that the vertical distance between the roof slab 2o and the core IC will increase. Even in such a case, with the above configuration, the control rod drive mechanism υ...
Since the control rods 2j are supported by the core support plate 16m, the relative position between the control rods 2j and the reactor core 16 does not change, and the reactor output can be normally controlled.

In addition, since the control rod drive mechanism L''...K is provided with a two-way mechanism 26 and an engaging pawl 21..., the second mechanism 26 is disengaged when changing fuel, and the 111j control rod 25 is disengaged.
is dropped into the reactor core J6, and the drive section 22 and guide tube 23 are
The core fuel 16 can be replaced by pulling it upward.

It should be noted that the present invention is not limited to the above-mentioned embodiment; however, the present invention is not limited to tank-type fast breeder reactors.
It can also be applied to the shape of tun O.

Additionally, the engaging claws 21 are not limited to being fixed to the inner surface of the guide tube 210, but may be fixed to the outer peripheral surface.

〔Effect of the invention〕

The fast breeder reactor according to the present invention is designed so that a control rod drive mechanism is supported by a core support plate at the bottom of the reactor core. Therefore, even if the distance between the upper shield and the reactor core increases due to vibrations caused by an earthquake, etc., the reactivity of the reactor inserted into the reactor core remains the same as in normal times, making it possible to control the reactor output normally. This is an expansion of the effect.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view showing a conventional tank-type fast breeder reactor, Figures 2 and 3 are configuration diagrams showing a conventional control rod drive mechanism, and Figure 4 is a vertical cross-sectional view showing an embodiment of the present invention. Fig. 5il
I is a vertical sectional view of the control rod drive mechanism that is used in the 11I koji example of the present invention, FIG. 6 is a sectional view of the smo* section, FIG. 7, and 5aiaa -! of the main proboscis. It is a block diagram of Example J. 14...Reactor vessel, 16...Reactor core, 1σm...
Core support plate, 20... roof slab (upper shield),
U... Control rod drive mechanism, 22... Core fuel, 21.
...Latching claw (attachment/detaching mechanism), 29...Bellows mechanism. Applicant's agent Patent attorney Takehiko Suzue Figure 4'lA5 Figure 86 Figure 7

Claims (1)

[Scope of Claims] (1) A reactor core provided in a reactor vessel, a core support plate provided at the lower end of the reactor core to support the core, and an upper shield that closes off the upper part of the reactor vessel. , a control rod drive mechanism that passes through the upper shield and is supported by the core support plate, an attachment/detachment mechanism provided at the bottom of the control rod drive mechanism, and the control rod drive mechanism and the upper shield are freely displaceable. A fast breeder reactor characterized by a bellows mechanism that maintains airtightness. (2) The control rod drive mechanism has a cylindrical extension tube provided vertically penetrating the reactor core, and the attachment/detachment mechanism is provided at the lower end of the extension tube. Fast breeder reactor described in patent (1). (3) The attachment/detachment mechanism is fixed to the lower end of the control rod drive mechanism and has an engaging pawl formed of spring steel that engages with the core support plate. A fast breeder reactor according to scope item (1).