JPH01150892A - Shielding plug device - Google Patents

Abstract

PURPOSE:To decrease the rotating resistance of a rotating plug by projecting a stationary cylinder and rotating cylinder to the lower side of the inside circumferential face of a stationary plug and the outside circumferential face of the rotating plug and communicating the spacing between both the cylinders with the spacing between both the plugs. CONSTITUTION:The stationary cylinder 39 and the rotating cylinder 40 are respectively fixed at one end to the inside circumferential face of the stationary plug 24 and the outside circumferential face of the rotating plug 25. The cylinders 39, 40 have the length at which the cylinders come into contact with a heat shielding plate 36 in a cover gas installed below both the plug 24. The spacing 41 between the cylinders 39 and 40 is communicated with the spacing 34 between the plug 24 and the plug 25. The respective bottom ends of the cylinders 39 and 40 are brought into contact with the shielding plate 36 installed below the plug 24 by this constitution. The quantity of the metal vapor infiltering the spacing 34 between the two plugs 24 and 25 is limited by the quantity of the vapor at which the liquid metal sodium penetrated from the contact surfaces between the cylinders 39, 40 and the shielding plate 36 reevaporates within the range of the cylinders 39, 40 and, therefore, the rotational driving of the plug, etc., are prevented from being hindered.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to an improvement in a shielding plug device for closing the upper end opening of a nuclear reactor vessel of a liquid metal cooled high speed filter.

1 (Prior Art) The configuration of a conventional shielding plug device will be explained with reference to FIG.

The reactor vessel 1 has an open upper end, and contains liquid metal sodium 3 for cooling the reactor core 2 . This JII [fixed plug 4 whose upper end opening of the child furnace vessel 1 is annular]
A through hole provided at an eccentric position of the fixed plug 4 is closed by a disk-shaped rotating plug 5.

Cover gas heat shielding plates 16 and 17 are attached below the fixed plug 4 and rotating plug 5 by support rods 18 so as to block radiant heat from the liquid metal sodium 3.

The fixed plug 4 is fixed to the reactor vessel 1, and the "-" portion thereof includes a drive device 7 having a drive gear 6 that rotates around a vertical axis, and a hydraulic cylinder device 9 in which a rod 8 is driven in the vertical direction. It is provided. Rotating plug 5 is fixed plug 4
It has a turning gear 10 which is rotatable relative to the l drive gear 6 and meshes with the l drive gear 6, thereby being rotationally driven. Further, the one-turn plug 5 is connected to a rod 8 of a hydraulic cylinder 9, and is thereby driven up and down. The rotating plug 5 is provided with an upper core mechanism 12 having a control rod 11 and a fuel exchanger 13. Note that heat exchangers and the like are omitted for simplicity of explanation.

By the way, in such a fast reactor, a phenomenon occurs in which sodium vapor evaporated from the surface of liquid metal sodium as a coolant enters the annular gap 14 between the stationary plug 4 and the rotating plug 5 and solidifies. This solidified sodium creates a large resistance when the rotating plug is rotated 40 times.

Further, an offset portion 15 that is stepped in the vertical direction is formed in the gap 14 between the fixed plug 4 and the rotary plug 5. Then, for example, a rotating plug 5 is used for fuel exchange, etc.
If the rotary plug 5 is lifted, sodium will solidify and accumulate in the space of the offset part 15 formed by lifting the rotary plug, and when the rotary plug 5 is lowered after a fuel change, it may not return to its normal position, or the solidified sodium may If the distribution is not uniform, the rotary plug 5 will be tilted, which will interfere with the operation of the control rod drive mechanism and cause movement that will make it impossible to start the reactor.

(Problems to be Solved by the Invention) In conventional shielding plug devices, solidified sodium vapor accumulates in the annular gap and offset portion between the stationary plug and the rotating plug, and solidifies, resulting in normal operating conditions. It may become unsustainable.

The present invention has been developed in view of these circumstances, and it eliminates the need for maintenance related to sodium fixation, allows the rotating plug to rotate and move up and down normally, and ensures control rod position control and fuel exchange operations. The purpose of the present invention is to provide a shielding plug device that can improve the reliability of an atomic filter.

[Structure of the invention]

(Means for Solving the Problems) The present invention includes an annular fixing plug that closes the upper end opening of the reactor vessel of a liquid metal cooled high-speed filter, and a disc-shaped fixing plug that closes the through hole inside the fixing plug. a rotating plug, the shielding plug device having an annular gap formed between the two plugs, a fixed cylinder and a rotating cylinder extending below the inner circumferential surface of the fixed plug and the outer circumferential surface of the rotating plug; protruding from each other, both cylinders have a length that touches the upper surface of a cover gas heat shielding plate provided below the fixed plug, and the gap between the two cylinders communicates with the gap between the two plugs. It is characterized by

(Function) The fixed cylinder that hangs down from the fixed plug and the rotating cylinder that hangs down from the rotating plug have their lower ends in contact with the cover gas heat shield plate provided below the fixed plug. The amount of metal vapor that enters the gap is limited to the amount of vapor that is re-evaporated within the gap between the two cylinders from the liquid metal that has seeped in from the contact surface between the cylinders and the heat shield plate in the cover gas. Its amount is significantly reduced. Here, the cover gas heating shield plate has a thin plate structure that is soft and easily deformed, so even if the lower end level of the rotating cylinder is lower than the fixed cylinder, the cover gas heating shield plate will deform. The lower ends of both cylinders will be closed. Note that the lower end of the rotating cylinder is dimensioned so that it does not rise above the lower g11+ of the fixed cylinder.

In addition, since the lower end of the gap between the two plugs is closed with a cover gas heat shield plate and separated from the cover gas space, the natural convection that occurs within this gap is greatly weakened. Therefore, the temperature distribution in the circumferential direction in the gap can be significantly reduced, making it possible to approach a uniform temperature distribution.

(Example) An example of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 shows a fast reactor superstructure with a shielding plug arrangement.

The reactor vessel 21 has an open upper end, and contains liquid metal sodium 23 for cooling the reactor core 22 inside. The upper end opening of this JIF reactor vessel 21 is closed by an annular fixed plug 24, and a through hole provided at an eccentric position of this fixed plug 24 is closed by a disc-shaped rotating plug 25. Below the fixed plug 24 and rotating plug 25, cover gas heat shield plates 36, 37 are installed with support rods 38 so as to block radiant heat from the liquid metal sodium 23. The fixed plug 24 is fixed to the reactor vessel 21, and a drive device 27 having a drive gear 26 that rotates around a vertical axis and a hydraulic cylinder device 29 that drives a rod 28 in the vertical direction are provided on the top thereof. ing. The rotary plug 25 is rotatable with respect to the fixed plug 24, and the rotating gear 3 meshes with the drive gear 26.
0, and is rotationally driven by this. Further, the rotary plug 25 is connected to a rod 28 of a hydraulic cylinder device 29, and thereby is driven upward. The rotating plug 25 is provided with an upper core mechanism 12 having a control rod 31 and a fuel exchanger 33.

There is an annular gap 34 between the inner circumferential surface of the fixed plug 24 and the outer circumferential surface of the rotary plug 25, and an offset portion 35 that is stepped in the vertical direction is formed in the gap 34.

In this device, a fixed cylinder 39 and a rotating cylinder 40, which extend below the gap VX 34, are protruded from the inner circumferential surface of the fixed plug 24 and the outer circumferential surface of the rotary plug 25, respectively. That is, one end (upper end) of each cylinder 39, 40 is fixed to the inner peripheral surface of the fixed plug 24 and the outer peripheral surface of the rotating plug 25, respectively. Both cylinders 39.
40 has a length that contacts the cover gas heat shielding plate 36 installed below the fixed plug 24. Further, the gap 41 of both cylinders 39, 40 communicates with the gap 34 between the fixed plug 24 and the rotary plug 25.

According to such a configuration, the lower ends of the fixed cylinder 39 and the rotating cylinder 40 are in contact with the heat shielding plate 36 in the cover gas installed below the fixed plug 24, so that both plugs 24 ．． .

The amount of metal vapor that enters the gap 34 of the cylinder 39.
The amount of vapor reevaporated is limited to within a range of 40%. That is,
Like the conventional device in which the gap between the two plugs opens widely to the surface of the liquid metal, strong natural convection using the cover gas space and the gap 34 between the two plugs as a flow path causes metal vapor to flow from the wide liquid surface into the gap between the plugs. Unlike the inflow, the amount of sodium vapor entering vX34 is significantly reduced.

In addition, the lower end of the gap 34 between both plugs is closed by the cover gas heat shielding plate 36 and is isolated from the cover gas space, so the natural convection that occurs within the gap 34 is greatly weakened. The circumferential temperature distribution in the gap can be significantly reduced, making it possible to approach a uniform temperature distribution.

Therefore, according to the above embodiment, the amount of steam flowing into the gap 34 between the fixed plug 24 and the rotating plug 25 itself can be reduced, and there is no problem with the rotational drive and lifting drive of the rotating plug 25. In addition, the positioning of the rotary plug 25 after its descent and the normalization of the operation of the control rod drive mechanism are ensured. Furthermore, since it is possible to weaken the natural convection within the gap 34 between the fixed plug 24 and the rotating plug 25, it is possible to equalize the circumferential temperature distribution in the gap 34, thereby reducing thermal deformation and thermal stress in the structure of the relevant part. It becomes possible to reduce the

〔Effect of the invention〕

As described above, according to the building plug device according to the present invention,
It is possible to reduce the amount of metal vapor flowing into the gap between the fixed plug and the rotating plug of the high-speed filter, reducing the rotational resistance of the rotating plug and reducing the driving capacity. In addition, it can eliminate the need for maintenance related to sodium fixation, normalize the operation of the rotating plug, control the position of control rods, and ensure operations such as fuel exchange, which can greatly contribute to improving reactor reliability. Furthermore, since it is possible to suppress natural convection in the gap between the fixed plug and the rotating plug, it is possible to equalize the temperature distribution in the circumferential direction in the relevant part, and to reduce thermal deformation and thermal stress. This can contribute to improving the reliability of the atomic filter.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention, FIG. 2 is an enlarged view of the section ``■'' in FIG. 1, and FIG. 3 is a longitudinal sectional view showing a conventional example. 21... Reactor vessel 23... Liquid metal sodium 24... Fixed plug 25... Rotating plug 34... Gap between plugs 39... Fixed cylinder 40... Rotating cylinder 4... Gap between cylinders 36, 37...cover gas heat shield plate 42
...Cover gas space agent Patent attorney Nori Ken Chika Yudo Ken Daishimaru Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] The liquid metal-cooled high-speed filter has an annular fixed plug that closes the upper end opening of the atomic filtration container, and a disc-shaped rotating plug that closes the through hole inside the fixed plug, and a cover is provided below both plugs. In a shielding plug device having a shielding plate capable of being heated in gas, a fixed cylinder and a rotating cylinder are respectively provided projecting below the inner circumferential surface of the fixed plug and the outer circumferential surface of the rotary plug, and these cylinders are connected to the fixed plug. 1. A shielding plug device, characterized in that the length of the shielding plug is in contact with the upper surface of a cover gas heating plate provided below, and the gap between both cylinders communicates with the gap between the two plugs.