JPS6058588A - Rotary shielding plug for nuclear 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 C. Technical Field to Which the Invention Pertains] The present invention relates to a rotating shielding plug for a nuclear reactor of a sealing mechanism of a rotating plug type, which is one of the fuel exchange systems of a fast breeder reactor.

[Prior art and its problems]

The rotating shield plug is one of the fuel exchange systems for fast breeder reactors, and although it remains fixed during steady operation of the reactor, it rotates and functions during fuel exchange.

FIG. 1 shows a schematic cross-sectional view of a conventional single-rotation plug installed at the top of a reactor vessel of a fast breeder reactor. As shown in the figure, a seal portion 12 is provided in an annular space 13 on the sliding surfaces of the rotating plug 10 and the fixed plug 11.

Note that A and B indicate the center of the rotating plug and the center of the upper part of the furnace vessel, respectively.

Figure 2 shows an enlarged view of the seal part.
It has a 2 i seal structure with a double seal alloy tube seal. In other words, the freeze seal alloy section is composed of a freeze seal alloy 15 provided so that the partition plate 14 that is a part of the rotating plug 10 is immersed therein, and an alloy storage container 16 that stores the freeze seal alloy 15. On the other hand, the tube seal part is located above the freeze seal alloy part, and two tube seals 17 facing each other are attached, and lubricating oil 18 is supplied between these tube seals 17. . Note that an oil receiver 19 is provided below the tube seal to collect leaked oil.

A problem that is a concern with the seal structure configured in this manner is that oil in the tube seal portion may leak out due to damage to the tube 17, and a situation may arise in which liquid and vaporized oil mix into the alloy. That is, if oil gets mixed into the seal alloy, there is a risk that reactants will be generated in the alloy due to the stirring effect of the partition plate 14 as the rotating plug 10 rotates, and if oil is generated, these reactants may have various adverse effects. There is a possibility that it will fall short. For example, reactants may be present in the alloy or at the contact surface between the alloy and a container housing the alloy, impairing the inherent sealing performance of the alloy, and rotational torque of the partition plate 14 due to the presence of reactants in the alloy. It is assumed that an increase in the amount of water will not interfere with the rotation function of the rotary plug.

In order to prevent these troubles, the conventional structure is to provide an oil receiver 19 below the tube seal to collect leaked oil. However, although this conventional structure prevents liquid oil from being mixed into the alloy,
No measures have been taken to prevent oil leaking from the tube seal portion or oil collected in the oil receiver 19 from being vaporized by evaporation and mixed into the alloy.

It can be easily inferred that even when vaporized oil forms an oil film layer on the alloy surface, reactants are generated, similar to when liquid oil is mixed into the alloy. Therefore, it is necessary to take measures to prevent vaporized oil from being mixed into the alloy.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned points, and it is assumed that if the old oil used in the tube seal part mixes into the seal alloy in a vaporized state, for example, reactants will be generated. It is an object of the present invention to provide a rotating shielding plug for a nuclear reactor having a structure that prevents this and prevents damage to the sealing function of the seal alloy and the function of the rotating plug.

[Summary of the invention]

Silicon-based oil is generally used as the lubricating oil for the tube seal. Silicone oil is about -50
It has a freezing point near °C, and the present invention was developed with a focus on this solidifying temperature.It is provided at the open end of a pressure vessel, and a sealing alloy is provided in the annular space of the sliding part of the fixed plug and rotating plug. This rotary shielding plug for a nuclear reactor is equipped with a sealing mechanism using a tube seal, and is characterized in that an oil sensing sensor is provided between the seal alloy part and the tube seal part.

[Embodiments of the invention]

Embodiments of the present invention will be described using the drawings. In one embodiment of the present invention, as shown in FIG. 3, the characteristic difference from FIG. 1 and FIG. It is formed with two sections.

For this reason, if lubricating oil leaks out due to damage to the tube seal and accumulates in the oil receiver 19, liquid nitrogen gas or the like is poured into the oil cooling pipe 21 to cool the oil to -50°C.
It is then cooled and solidified.

By maintaining the oil in a solidified state in this manner, the oil is prevented from evaporating and becoming mixed into the alloy.

Note that when taking out the oil from the oil receiver 19, cooling is stopped (the oil temperature is raised to 150° or higher) and the oil is returned to a liquid state.

FIG. 4 shows another embodiment of the present invention in which not only the outer periphery of the oil receiver 19 but also the rotary plug 10 directly below the tube seal portion is shown.
This is an example in which oil cooling piping is also provided in the wall portion on the side and the fixed plug 11 side.

In the case of this embodiment, the oil leaking from the tube seal portion can be solidified before it accumulates in the oil receiver 19, that is, when the oil is attached to the wall.

[Effects of the Invention] According to this invention, even if oil leaks in the oil pan and oil accumulates, it is possible to prevent the oil from vaporizing and mixing into the alloy, and the rotation function of the hypothetical rotating plug can be improved. There is no fear that it will cause any problems.

[Brief explanation of the drawing]

Fig. 1 is a sectional view schematically showing the main parts of a conventional rotating shielding plug, Fig. 2 is an enlarged sectional view of a part of Fig. 1, and M
FIG. 3 is an enlarged sectional view of a main part showing one embodiment of a rotating shielding plug for a nuclear reactor according to the present invention, and FIG. 4 is a sectional view showing a main part of another embodiment of the present invention. 10-... Rotating plug 11... Fixed plug 12...
・Seal part 13... Annular space part 14... Partition plate
15... Freeze seal alloy 16... Alloy storage container 17... Tube seal 18... Oil 19.
...Oil receiver 20...Inner reactor space 21...Oil cooling piping agent Patent attorney Nori Sosuke Chika (and 1 other person) Fig. 1//1 Fig. 2/h Fig. 3//1 Figure 4

Claims (1)

[Claims] A rotating shielding plug for a nuclear reactor that is provided at the open end of a pressure vessel and has a sealing mechanism using a seal alloy and a tube seal in the annular space between the sliding part of the fixed plug and the rotating plug, and is provided below the tube seal mechanism. A rotary shielding plug for a nuclear reactor, characterized in that an oil receiving portion is equipped with an oil cooling pipe.