JPS5912640Y2 - Rotating plug seal mechanism - Google Patents

Description

[Detailed description of the invention] The present invention relates to an improvement of a rotating plug sealing mechanism used as a device for sealing contaminated gas in the gap between a fixed plug and a rotating plug in a fast breeder reactor that uses liquid metal as a coolant, for example. .

A conventional rotary plug seal mechanism used in a fast breeder reactor is composed of a partition plate, a tub, and a low melting point alloy.

Incidentally, the tub for storing the low melting point alloy has a double structure with cooling channels in order to solidify the low melting point alloy.

By the way, it is necessary to set the melting point of the low melting point alloy as low as possible so that excessive thermal stress does not act on nearby structures when melting the low melting point alloy, and so as not to adversely affect the O-ring etc. be.

However, during normal operation of a nuclear reactor, the temperature inside the reactor is around 500° C., which heats the vicinity of the rotating plug seal mechanism.

Therefore, the melting point of the low melting point alloy is higher than the temperature near the rotating plug seal mechanism.

Further, in order to prevent the low melting point alloy from melting even in the unlikely event of an accident, the low melting point alloy is always forcedly cooled and solidified by other cooling means.

In addition, the rotary plug seal mechanism was required to have a good sealing function as a highly reliable container in order to prevent air pollution due to leakage of activated gas inside the reactor.

However, in conventional cooling using only a tub, a temperature difference occurs between the wall surface of the partition plate and the wall surface of the tub, causing uneven solidification of the low melting point alloy during solidification, resulting in a significant reduction in sealing performance.

Furthermore, there is a need to improve the sealing performance of low melting point alloys by increasing the cooling rate, and to shorten the cooling operation time for low melting point alloys.

The purpose of the present invention was to solve the above-mentioned problems, and to improve the sealing performance by uniform temperature distribution solidification of the low melting point alloy of the rotary plug seal mechanism, shorten the solidification time, and reduce the primary boundary of the reactor cover gas. The object of the present invention is to obtain a plug having a rotary plug sealing mechanism that has sufficient functions to form a shape.

The present invention will be described below with reference to the drawings of an embodiment.

In FIG. 1, a fixed plug 1 is mounted in the upper opening of a furnace vessel 2. In FIG.

A rotary plug 3 is eccentrically provided on the fixed plug 1.

There are two types of plug fuel exchange methods: single-rotation plug and double-rotation plug methods, but the single-rotation plug method will be explained here.

A cylindrical partition plate 4 is hermetically sealed near the outer periphery of the rotary plug 3 so as to protrude downward.

Further, the partition plate 4 is provided on the lower surface of the opening edge of the fixed plug 1.
and a concentric disk tub 5 are hermetically connected.

A low melting point alloy 6 is stored in this tub 5, and the lower part of the partition plate 4 is appropriately immersed in this low melting point alloy 6.

Inside the partition plate 4, as shown in FIG. 2, a cooling passage 7 is bent and installed around the circumference of the partition plate.

A refrigerant is flowed into the cooling passage 7 at the same time as the cooling passage 8 of the tub, and the low melting point alloy is solidified with uniform temperature distribution.

Further, as shown in FIG. 3, a heater 9 for melting the low melting point alloy 6 is embedded within the partition plate 4.

The low melting point alloy 6 is melted prior to rotating the rotary plug 3.

In addition, numeral 10 in the figure is a mechanical seal, which has a backup sealing function in case the rotary flag seal mechanism loses its sealing function by any chance.

12 is a reactor fuel assembly, and 13 is a liquid metal.

Next, the effect will be explained.

During reactor fuel replacement work, etc., the rotary plug seal mechanism is in a melted state by the heater 9 while the rotary plug rotates three times, and airtightness is maintained by the partition plate 4, the molten low melting point alloy 6, and the tub 5. There is.

At this time, the cooling passage 7 provided inside the partition plate 4 and the tub 5
, 8, no cooling medium such as N2 gas flows therein.

After the work is completed, when the reactor returns to normal operation and there is no need to rotate the rotary plug 3, the heat source of the heater 9 that melts the low melting point alloy 6 is turned off, and the partition plate 4 is turned off.
, a cooling medium is flowed into cooling passages 7 and 8 provided inside the tub 5.

As a result, the temperature of the low melting point alloy 6 gradually lowers uniformly throughout, and finally solidifies.

As a result, the sealing function will not be impaired even if the pressure inside the furnace suddenly changes.

Furthermore, by continuing to flow the cooling medium, the sealing function will not be impaired even when the temperature inside the furnace changes.

When the rotary plug 3 is to be rotated again, the flow of the cooling medium is stopped and a heat source is turned on to the heater 9, so that the rotary plug 3 can be quickly turned into a rotatable state.

As explained above, the rotary plug seal mechanism of the present invention is structured so that when cooling the low melting point alloy, the wall surface of the partition plate,
Non-uniform temperature distribution does not occur on the wall surface of the tub, and good sealing performance can be obtained.

Moreover, since cooling is performed from both sides of the partition plate and the tub, the cooling rate of the low-melting point alloy can be increased, and wasted time during reactor operation can be significantly reduced.

This improves the functional reliability of the reactor power source as a primary boundary.

[Brief explanation of drawings]

Fig. 1 is a schematic vertical sectional view of a nuclear reactor, Fig. 2 is a longitudinal sectional view showing an embodiment of the rotating plug seal mechanism of the present invention, and Fig. 3 shows the heater installation state of the rotating plug seal mechanism of Fig. 2. FIG. 4...Partition plate, 5...Pail, 6...
...Low melting point alloy, 7,8...Cooling passage, 9...
····heater.

Claims (2)

[Scope of utility model registration request] (1) an annular tub that stores a low melting point alloy that can be melted and solidified; an annular partition plate that is immersed downward into the low melting point alloy;
A rotating plug seal mechanism consisting of a cooling system for solidifying a low melting point alloy installed inside this partition plate. (2) The rotating plug seal mechanism according to claim 1, wherein a heater for melting the low melting point alloy is installed in the cooling system.