JPS58138290A - Liquid metal pump - Google Patents

Abstract

PURPOSE:To prevent natural convection of sodium flowing out through hole of a casing, by employing such structure where sodium is not stored at the double tubular gap of the casing and preventing the mass of sodium from being added on the casing. CONSTITUTION:Sodium 14 leaked through a gap of a lower hydrostatic bearing 5 will lift to flow out through a plurality of small holes 11 made in the circumferential direction of an inner casing 1 then temporarily dammed by a dam 13 and flows out uniformly and outwardly from the circumference on boards 12. Since th boards 12 are also inclined, the flow speed is increased and the flow will collide against the inner face of an outer casing 2 then drop between the inner and outer casings 1, 2 thereafter it is discharged thorugh an overflow nozzle 7 to the outside. Consequently the sodium is not stored at the double tubular section of said casings 1, 2, thereby it is prevented, during vibration, that the mass of the sodium is added on the outer casing 2 thus to prevent the natural convection of the cover gas at the thin gap section.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pump for liquid metal, and in particular to prevention of a drop in natural frequency during pump vibration and prevention of casing deformation caused by natural convection of inert gas in a double cage/g gap. The present invention relates to a liquid metal pump having a structure suitable for prevention.

The structure of a conventional liquid metal pump, for example, a sodium pump applied to a liquid sodium-cooled fast breeder reactor, is
This will be explained using figures.

In FIG. 1, 1 is an inner casing, 2 is an outer casing, 3 is a rotating shaft, and 4 and 5 are ball bearings and static pressure bearings that support the rotating shaft 3. The hydrostatic bearing 5 is lubricated by the discharge pressure of the pump. Further, a sodium free liquid level 6 is located in the middle of the casing, and an overflow nozzle 7 is attached to the outer casing for discharging sodium leaked from the hydrostatic bearing 5 to the outside of the pump. Furthermore, an inert gas gap 8 is formed above the sodium free liquid level 6.
By attaching natural convection prevention plates 9 in multiple stages to the inert gas slit 8 on the outer periphery of the inner casing 1 so as to touch the inner periphery of the outer casing 2, temperature differences in the circumferential direction of the casing due to natural convection are prevented. This prevents deformation.

In the conventional liquid metal pump configured as described above, liquid (IJumlO) accumulates between the inner casing and the outer casing, and when a lifting force is applied to the casing during an earthquake, etc., the inner The mass of liquid sodium accumulated between the casing and the outer casing is added to the inner and outer casings, lowering the natural frequency of the casing and increasing the amplitude of the casing, which increases stress in various parts of the casing due to vibration, and In order to increase the load on the lower hydrostatic bearing 5, it is necessary to increase the thickness of the casing and increase the bearing diameter in order to increase the load capacity of the lower hydrostatic bearing, which leads to an increase in pump production costs. There were drawbacks.

Generally, the sodium mass M added to the inner casing is given by the following formula.

Here: Otori: Inner casing outer diameter b: Outer casing inner diameter ρ: Sodium density t: Double space sodium height Also, because the conventional convection prevention plate has a structure in which the outer casing is fixed, the convection prevention plate always has a constant value. It is required to contact the inner periphery of the outer casing with spring force. However, since the convection prevention plate is generally manufactured as a thin plate, when used in a high-temperature sodium pump, it deforms and creates a gap between the outer casing and the inner periphery, completely blocking the natural convection of inert gas that causes casing deformation. could not be prevented.

In addition, the sodium pump has a structure in which the inner casing can be pulled out from the outer casing, and when the inner casing is pulled out and suspended, the thin convection prevention plate is damaged due to the frictional force with the outer casing. was there.

The present invention has a structure that prevents sodium from accumulating in the double cylindrical slit of the casing so that the mass of sodium is not added to the casing. In addition, instead of using a convection prevention plate to prevent the natural convection of inert gas in the narrow gap of the double cylinder, the purpose is to prevent the above natural convection by using a flow of sodium flowing out from a hole provided in the inner casing. That is.

The feature of the present invention is that a plurality of small holes are drilled in multiple rows in the axial direction around the inner casing, and the small holes are attached to the outer periphery of the lower end of the small hole so as to have a gap with the inner surface of the annular plate tube outer casing. The nozzle is installed below the row of small holes provided in the inner casing to prevent the mass of sodium from being added to the outer casing when the casing vibrates, and to cover the slit formed by the outer casing and inner casing. Prevent natural convection of gas.

An embodiment of the present invention will be described below with reference to FIG. Second
In the figure, parts given the same reference numerals as in FIG. 1 are the same parts. In FIG. 2, reference numeral 11 denotes a plurality of small holes provided around the inner casing 1 in a plurality of rows in the axial direction. A stacked plate 12 is attached to the outer circumference of the lower end of the small hole 11 at an angle to the outer circumference of the inner casing 1, and has a gap with respect to the inner surface of the outer casing 2. 13 is a weir installed on the circumference of the upper surface of the plate 12. 7 is an overflow nozzle attached to the outer casing 2 at a position below the small hole 11.

In this structure, sodium 14 leaking from the gap in the lower hydrostatic bearing 5 rises, flows out through the small holes 11 provided in the circumferential direction of the inner casing 1, and is stopped by the -tan dam 13. It flows outward evenly from the circumference of the plate 12. At this time, since the plate 12 is angled, the flow has a speed, and after hitting the inner surface of the outer casing 2, it falls between the inner casing 1 and the outer casing 2, and flows into the overflow installed below. It is discharged from the nozzle 7 to the outside of the pump.

As mentioned above, since the sodium accumulated in the double cylindrical part between the inner casing and the outer casing is eliminated, the mass added to the casing during vibration is eliminated, and the resulting increase in oscillation width causes an increase in stress and static pressure in the casing. It is possible to prevent an increase in the load applied to the bearing.

1+, the double cylindrical portion formed by the inner casing and the outer casing is divided in the axial direction by the flow flowing out from the small hole 11 and hitting the inner surface of the outer casing, so that natural convection of the inert gas can be prevented.

As a result, since there is no contact part with respect to the conventional convection prevention plate, there is an effect that the convection prevention plate is not damaged when the inner casing is hung or removed.

According to the present invention, the liquid metal that accumulates in the slit of the double cylindrical portion of the casing can be eliminated, which eliminates the mass added to the outer casing, and has the effect of preventing a decrease in the natural frequency of the casing. Since the natural convection of inert gas generated in the double cylindrical part of the casing can be prevented by a jet of liquid metal, damage to the convection prevention plate can be prevented when the inner casing is pulled out or suspended, compared to a contact type convection prevention plate. effective.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of 17 Umbongpu (conventional spring construction).
FIG. 2 is a longitudinal sectional view of a sodium pump to which the present invention is applied. 1...Inner casing, 2...Outer casing, 3...
・Rotating shaft, 4... Ball bearing, 5... Lower static pressure bearing, 6
...Free liquid level, 7.Overflow nozzle, 8.
...Inert gas slit, 9...Natural convection prevention plate, 10
...Cavity liquid Nato, Lium, Xl... Hole, 12.
... Plate, 13... Weir, 14... Hydrostatic bearing leaking sodium. Sai 1 Zuga 2 eyes

Claims (1)

[Claims] It has a double cylindrical casing consisting of an outer casing and an inner casing, and forms a free liquid surface of liquid metal on the surface in contact with the cover gas within the casing, and discharges the iron liquid to the outside when the free liquid level of the liquid metal rises. In the liquid metal pump, a plurality of rows of small holes are bored in the axial direction around the inner casing, and an annular plate is attached to the outer periphery of the lower end of the small hole. A pump for liquid metal, wherein the pump is mounted so as to have a gap with the inner surface of the casing, and the overflow nozzle is installed below the row of small holes provided in the inner casing.