JPH0116078Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an improvement of a fuel guide sleeve used during fuel exchange in a sodium-cooled nuclear reactor.

In a sodium-cooled nuclear reactor, a hold-down shaft is inserted into the reactor through a flexible rotary plug that penetrates the reactor vessel to form a fuel passage that spans the inside and outside of the reactor. A method using a hold-down axis is known. In other words, when loading and unloading fuel, the fuel inlet/output machine is connected to the outside of the furnace on the hold-down shaft, and while the fuel is stored in the fuel transfer pot, the fuel is transferred between the fuel storage rack inside the reactor and the fuel inlet/out machine outside the furnace through the hold-down shaft. will be delivered. In addition, when withdrawing spent fuel from the core during fuel exchange, connect the fuel exchanger to the hold-down shaft, position the exchanger at a predetermined position by operating the rotating plug, and then lower the hold-down shaft onto the core and hold it. While downing, the gripper is lowered through the hold-down shaft to grab the fuel in the reactor core, and once the gripper is pulled up and the fuel is stored in the hold-down shaft, the rotary plug is turned to release the fuel storage rack inside the reactor. Transfer the fuel into the pot. When loading new fuel from the in-core storage rack into the reactor core, this is done by performing the reverse operation as described above. This fuel exchange is different from the above-mentioned fuel loading and unloading, and the fuel is raised and lowered in a bare state within the hold-down shaft. Therefore, in order to correctly guide the grippers and fuel up and down within the large-diameter hold-down shaft, especially when replacing fuel, a small-diameter fuel guide sleeve is loaded inside the hold-down shaft. It has been conventionally practiced to guide the robot up and down. FIG. 1 shows how such a fuel guide sleeve is used. In the figure, 1 is a rotary plug installed at the top of the reactor pressure vessel, 2 is liquid sodium as a primary coolant housed in the reactor, and 3 is a liquid that penetrates the rotary plug 1 into the reactor. The hold-down shaft 4 installed in the drawer is the fuel guide sleeve to which this invention is applied. A door valve (not shown) and a mechanism for vertically driving the hold-down shaft (not shown) are provided at the upper end of the hold-down shaft. Further, in the illustrated example, the fuel guide sleeve 4 is divided into upper and lower halves, and the top part 51 of the lower guide sleeve 5 that constitutes the handling head engages with the support stepped part 31 formed in the middle part of the hold-down shaft 3. It is supported and further supports the upper guide sleeve 6 thereon. Furthermore, while the lower end portion 52 of the lower guide sleeve 5 is immersed below the liquid surface of the liquid sodium 2,
The top portion 51 is located in a sodium vapor atmosphere above the sodium liquid level. Note that numeral 7 indicates the main body of the fuel exchanger.

As mentioned above, such a fuel guide sleeve is loaded onto the hold-down shaft during fuel exchange, and is pulled out of the furnace again after the fuel exchange is completed.
It is desired that loading and unloading can be performed smoothly in addition to the fuel guide function.

By the way, the conventional detailed structure of the top part 51 and bottom end part 52 of the fuel guide sleeve shown as parts A and B in FIG. 1 is as shown in FIGS. 2 and 3. That is, in order to align the axial center of the guide sleeve 5 with the hold-down shaft 3, the top portion 51
The lower end portion 52 is particularly thickly bulged toward the outer circumferential side, and the outer diameter thereof is determined to substantially match the inner diameter of the hold-down shaft 3. Furthermore, the circumferential surfaces of the upper and lower ends are tapered as shown by the slope angle Q so that the guide sleeve does not become stuck in the middle of the passage during loading and unloading. Note that the upper guide sleeve 6 also has a similar structure.

However, with the conventional fuel guide sleeve described above, loading and unloading cannot be performed smoothly due to the sodium deposited on the inner wall surface of the hold-down shaft 3, and in the worst case, loading and unloading cannot be performed smoothly.
There was a problem where a trouble occurred that made it impossible to pull out. In other words, the hold-down shaft 3 is in an atmosphere of sodium vapor, and sodium may drip from the fuel transfer port when loading and unloading fuel, so that over a long period of time, the inner wall of the shaft 3 is exposed to the atmosphere of sodium vapor, as shown in FIGS. 2 and 3. Sodium Na adheres and accumulates.
For this purpose, in the process of moving the fuel guide sleeve 5 up and down in the hold-down shaft 3, the above-mentioned top part 5
1 and the deposited sodium Na entering toward the tapered surface of the lower end portion 52 acts as a wedge,
This acts as a resistance and prevents loading and unloading of the fuel guide sleeve. In addition, since the circumferential surfaces of the top portion 51 and the bottom portion 52 adhere to the accumulated sodium Na even though they do not act as wedges, loading of the guide sleeve,
Increase the load when pulling out. Furthermore, the guide sleeve 5 and hold-down shaft 3 are operated under the sodium liquid level.
The liquid sodium that has entered between the guide sleeve 5 and the guide sleeve 5 does not easily fall out when the guide sleeve 5 is pulled out.
For this reason, there were problems such as the area above the sodium liquid level getting wet and promoting the accumulation of sodium.

This invention was developed in consideration of the above points, and its purpose is to provide a fuel guide sleeve that eliminates the drawbacks of the conventional fuel guide sleeve and allows loading and unloading from the hold-down shaft to be carried out smoothly without being hindered by accumulated sodium. It's about doing.

This object is achieved by providing a plurality of guide ribs that protrude radially from the outer periphery of the guide sleeve and whose outer diameter substantially matches the inner diameter of the hold-down shaft.

This invention will be described in detail below based on illustrated embodiments.

4a, b and 5 a, b show the structure of an embodiment of this invention corresponding to the parts shown in FIGS. 2 and 3, respectively. 51 and lower end portion 52
A plurality of guide ribs 53, 54 are bulgingly formed to protrude radially from the outer circumferential surface of the guide ribs 53, 54. The guide ribs 53 and 54 are designed so that their outer diameters almost match the inner diameter of the hold-down shaft 3, and their upper and lower ends are tapered to prevent them from sticking when going up and down. There is. Further, a flange-shaped sodium scraper 55 is formed on the lower end portion 52, particularly at the same position as the guide rib 54, and protrudes from the outer periphery of the guide sleeve 5. This sodium scraper 55 has a sharp outer peripheral edge so as to constitute a blade portion. Furthermore, a sodium drain through hole 56 is opened in the guide sleeve so as to communicate between the upper surface side of the sodium scraper 55 and the inner peripheral side of the guide sleeve 5. Although not shown, the upper guide sleeve 6 of FIG. 1, which is not immersed under the sodium liquid level, is constructed in the same manner as the lower guide sleeve 5 described above, except for the through hole for the sodium drain.

According to the above configuration, first, the guide sleeve 5 is connected to the guide ribs 53 and 54 with respect to the hold-down shaft 3.
It is held in the correct posture with the axis centered. Moreover, only the guide ribs 53 and 54 are in contact with the inner wall of the hold-down shaft 3, and the second
The contact area is much smaller than that of the conventional structure shown in FIGS. As a result, the adhesion area of sodium Na adhering to the inner surface of the hold-down shaft 3 is greatly reduced, so the guide sleeve 5
The load when loading and unloading is reduced. In addition, the sodium scraper 55 at the lower end portion 52 slides on the inner wall of the hold-down shaft 3 during the process of the guide sleeve 5 moving up and down inside the hold-down shaft 3, and the sodium scraper 55 slides on the inner wall of the hold-down shaft 3 to remove the accumulated sodium Na. Scrape off and scrape off the accumulated sodium
remove. Furthermore, when the guide sleeve 5 is pulled out of the furnace, the liquid sodium that has entered between the guide sleeve 5 and the hold-down shaft 3 below the sodium liquid level flows down smoothly through the drain hole 56, so that the hold-down is completed. The upper part of the shaft 3 is no longer directly wetted with liquid sodium, and the accumulation of sodium in this part can be suppressed.

As is clear from the above, the configuration of this invention allows the loading and unloading of the guide sleeve to be carried out on the inner surface of the hold-down shaft while maintaining the normal guiding function of the fuel and gripper during fuel exchange. Practical effects can be achieved in that the process can be carried out smoothly without being hindered by the adhering sodium.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of the structure showing the state in which the fuel guide sleeve is loaded on the hold-down shaft, Figs. 2 and 3 are enlarged views showing the conventional structure of parts A and B in Fig. 1, and Fig. 4 a 5a is a block diagram of the embodiment of the second invention corresponding to FIGS. 2 and 3, respectively, and FIGS. 4b and 5b are viewed from the arrows in FIGS. 4a and 5a, respectively. -, - It is a sectional view. DESCRIPTION OF SYMBOLS 1... Shiyahei rotating plug, 2... Liquid sodium, 3... Hold down shaft, 4... Fuel guide sleeve, 5... Lower guide sleeve, 51... Top, 52... Lower end, 53, 54 ...Guide rib, 55...Sodium scraper, 56...Through hole for sodium drain.

Claims (1)

[Scope of Claim for Utility Model Registration] 1. The hold-down shaft is inserted into the reactor through a flexible rotary plug of the reactor vessel to form a fuel passage extending between the inside and outside of the reactor. In the fuel guide sleeve loaded and supported within the hold-down shaft, protruding radially from the outer periphery of the fuel guide sleeve,
A fuel guide sleeve for a sodium-cooled nuclear reactor, characterized in that a plurality of guide ribs are provided, the outer diameter of which substantially matches the inner diameter of a hold-down shaft. 2 Utility Model Registration A fuel guide sleeve for a sodium-cooled nuclear reactor according to claim 1, characterized in that guide ribs are provided at the top and bottom ends of the guide sleeve. 3. In the fuel guide sleeve according to claim 1 or 2 of the utility model registration, a flange-shaped sodium scraper that bulges out from the outer periphery of the sleeve is provided together with the guide rib at the lower end of the guide sleeve, and the sodium A fuel guide sleeve for a sodium-cooled nuclear reactor, characterized by having a through hole for a sodium drain communicating between the upper surface side of the scraper and the inner peripheral side of the sleeve.