JPS6018794A - Shielding plug device - 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 shielding plug device for a liquid metal cooled fast breeder reactor.

[Technical background of the invention and its problems] In general, in a liquid metal cooled fast breeder reactor, in order to open the upper end opening of the reactor vessel, a fixed plug and a through hole protruding from the fixed plug are rotated. A shielding plug arrangement consisting of a freely rotating plug is arranged.

However, in such fast breeder reactors that use liquid metal sodium as a coolant, sodium vapor evaporates from the free liquid surface of the coolant, and these sodium vapors are transferred to fixed plugs and rotating plugs installed at the top of the reactor vessel. Sodium vapor enters the annular gap between the plugs, solidifies in this gap, and its amount increases over time, and the force required to shear the sodium to close the gap acts as a large resistance when the rotating plug rotates. Furthermore, when the rotating plug is lifted for fuel exchange, the rising sodium vapor adheres and accumulates on the flat surface of the space between the rotating plug and the stationary plug, which is formed by lifting the rotating plug. If the rotary plug does not return to its normal position when lowered after refueling, or if the fixed sodium is unevenly distributed, the rotary plug will tilt. As a result, the height from the lower end of the rotary plug to the reactor core changes, making it impossible to control the position of the control rods by the control rod drive mechanism, and there is a possibility that the reactor cannot be started.

[Object of the Invention] The present invention has been made in response to the above-mentioned circumstances, and is a reliable method that can easily remove the sodium vapor stuck and deposited on the flat surface of the space between the fixed plug and the rotating plug, and maintain normal operating conditions. The present invention aims to provide a highly shielded plug device.

[Summary of the Invention] That is, the present invention comprises a fixed plug that shields the upper end opening of a reactor vessel, and a rotating plug that is inserted into a page through hole formed in the fixed plug. A shielding plug device comprising: a rotary plug shielding body formed to protrude from the rotary plug, the rotary plug shielding body being placed on the fixed plug formed on the fixed plug, and supporting the rotary plug on the fixed plug; This shielding plug device is characterized in that a liquid metal scraping blade is disposed on the lower surface of the fixed plug and is biased toward the upper surface of the upper plate of the fixed plug.

[Embodiment 1 of the Invention] The details of the present invention will be described below with reference to an embodiment shown in the drawings.

FIG. 1 shows a fast breeder reactor equipped with a shielding plug device according to an embodiment of the present invention, in which a fixed plug designated by reference numeral 1 is mounted at the upper end opening of a reactor vessel 2. In FIG. A rotating plug 3 is eccentrically arranged on the fixed plug 1.

A core upper mechanism 5 having a control rod 4 for controlling the reactor is mounted on the rotating plug 3 and extends to the upper part of the reactor core 6.

Further, a rotary plug drive device 7 is disposed above the fixed plug, and this rotary plug drive device 7 transmits driving force to the rotary plug 3 via a swing gear 8, and drives the rotary plug 3 placed on a swing bearing 9. Rotate.

FIG. 2 shows details of section A in FIG. 1, and in the figure, reference numeral 1 indicates a fixing plug. A rotating plug shielding body 12 fixed to the rotating plug upper plate 11 is mounted on the bottom of the fixed plug upper plate 10 disposed at the top of the fixed plug 1 so as to bear the entire weight of the rotating plug 3. On the other hand, the surface of the rotating plug shielding body 123-, which is mounted on the bottom of the fixed plug upper plate 10, is cut out in several places (for example, four places) as shown in FIG.

As shown in FIG. 4, a blade support fitting 13 for fixing the upper ends of the three rods 14 is fixed to this notch. At the lower ends of these three rods 14, a blade 15 having a triangular bottom surface is disposed so as to be movable up and down and biased by a spring 14a. A melting heater 19 is embedded in the bottom of the fixed plug upper plate 10.

In the shielding plug device configured as described above, by lifting the rotary plug 3 with the hydraulic cylinder 16 during fuel exchange, the helium vapor that rises through the small gap 17 between the rotary plug 3 and the fixed plug 1 and adheres there. Automatically sheared.

On the other hand, as the rotating plug 3 rises, the rotating plug shielding body 12
The blade 15 biased by the spring 14a remains at the bottom of the fixed plug upper plate 10, and a gap 18 is formed between the blade 15 and the bottom of the fixed plug upper plate 10. During work with the rotating plug 3 lifted, sodium vapor constantly rises from the natrium 4-ram liquid level in the furnace through the gap between the rotating plug 3 and the fixed plug 1, reaches the gap 18, and is cooled there. be done. Therefore, the adhesion of the vapor on the other side of the contact surface between the blade 15, which is urged by the spring 14, and the bottom of the fixed plug upper plate 10 increases over time.

However, in the shielding plug device configured as described above, by heating several melting heaters 19 provided in the bottom of the fixed plug upper plate 10 in the circumferential direction, the plug can be fixed on the bottom of the fixed plug upper plate 10. The sodium is melted. By rotating the rotary plug 3 by the rotary plug drive device 7, the sodium melted by the edge portion 20 of the blade 15, which is urged from the rotary plug shielding shell 12 to the bottom of the fixed plug upper plate 10, is directed into the furnace. scraped off. As a result, the sodium stuck to the bottom of the fixing plug top plate 10 is removed, allowing normal jacking down.

[Effects of the Invention] As described above, according to the shielding plug device of the present invention, the sodium adhering to the upper plate of the fixed plug can be completely removed. It is possible to reduce the number of overhauls and inspections of the device, and it is possible to reduce radiation exposure of workers. In addition, by removing sodium, normal jackdown can be quickly achieved, and as a result, the operating rate can be improved.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing a fast breeder reactor equipped with a shielding plug device according to an embodiment of the present invention, FIG. 2 is a longitudinal sectional view showing details of section A in FIG. 1, and FIG. FIG. 4 is a cross-sectional view taken along the line ``---'' in the figure, and FIG. 4 is a vertical sectional view taken along the line TV--TV in FIG. 12... Rotating plug shielding body 13.
......Blade support fitting 14, a...
・・・・・・Spring 15・・・・・・・・・・・・
・Blade 19・・・・・・・・・Melting heater 2
0・・・・・・・・・・・・Etsuji Figure 1

Claims (1)

[Claims] (1) Consists of a fixed plug that shields the upper end opening of the reactor vessel, and a rotating plug that is inserted into a through hole formed in the fixed plug, and is formed to protrude laterally from the upper part of the rotating plug. In the shielding plug device, in which a rotating plug shielding body is placed on a plate shape on a fixed plug formed on the fixed plug, and the rotating plug is supported by the fixed plug, the fixed plug is placed on the lower surface of the rotating plug shielding body. A shielding plug device characterized in that a blade for scraping liquid metal is provided that is biased toward the upper surface of an upper plate.