JPS62168095A - Primary main circulating pump for liquid-metal cooled fast breeder 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 [Field of Application of the Invention] The present invention relates to a primary main circulation pump for a liquid metal cooled fast breeder reactor.

[Background of the invention]

Mechanical pumps that circulate liquid metal are of the allam type and the Fermi type, using a treatment method that flows the lubricant of the hydrostatic bearing 10 (see Figure 15) in the coolant.
ermi) type, and the differences between the two are shown in Figures 5 and 6.
This will be explained in the figure. In the figure, 1 is the impeller wheel, 3 is the discharge casing, 4 is the suction nozzle, 5 is the discharge port, 7 is the pump upper tank chamber, 8 is the rotating shaft, 10 is the static pressure bearing, 15
is the over 70-processing system, 19 is the pump lower tank chamber, 2
o is an overflow column, and 21 is a pump liquid level fluctuation width.

In the Hallam type shown in FIG. 5, since the pump lower tank chamber 19 is under high pressure, the coolant for hydrostatic bearing lubrication that has flowed into the pump upper tank chamber 7 from the pump lower tank chamber 19 is returned to the pump lower tank chamber 19. Since this is not possible, it is made to flow out from the overflow column 20 to the outside of the pump. 7th
The figure shows a system in which a Hallam type circulation pump 12 shown in FIG. 5 is installed between the primary outlet of the intermediate heat exchanger 13 and the reactor vessel 11.
This figure shows the main cooling system equipment, in which liquid metal is sent from the intermediate heat exchanger 13 side to the reactor vessel 311 side as shown by the arrow. Incidentally, lN8LIE8L are the levels of liquid metal during normal operation and during pipe damage, respectively. In this pump, an overcrow 70-treatment system 1 is used to return the coolant flowing out from the overcrow column 20 to the circulation pump suction side piping.
Note that by allowing the coolant to flow out from the overflow column 20, the liquid level can be maintained near the overflow column 20.

On the other hand, in the Fermi type shown in FIG. 6, since the pump lower tank chamber 19 has a low pressure, it is possible to return the bearing lubricant with its own blade, and therefore the overflow treatment system 15 is not necessary. Due to pressure changes in the lower tank chamber 19, the liquid level in the pump upper tank chamber 7 fluctuates within a liquid level fluctuation range 21.

In particular, in the case of cold leg pumps, there is an intermediate heat exchanger on the suction side, so pressure loss fluctuations due to changes in flow are severe.
In the demonstration reactor class (one in the middle stage between an experimental reactor and a practical reactor), the length can reach approximately 10 m, so the width of liquid level fluctuation 21 in the upper tank chamber 7 of the pump becomes large, and therefore the pump has to be very long. There is a need to.

Furthermore, mechanical pumps for liquid metal coolant are divided into single suction pumps shown in FIG. 8 and double suction pumps shown in FIG. 9. For single suction pumps, it is the Haram type.

7. Both Hermi types are valid, but in a double suction pump, the pump lower tank chamber 19 is always on the low pressure side, so 7.
Only Elmi-type pumps are suitable.

10 and 11 are characteristic diagrams of the relationship between the discharge amount and the rotation speed of the single suction pump and the double suction pump, with the horizontal axis representing the discharge amount and the vertical axis representing the rotation speed, respectively. figure,
FIG. 13 is a characteristic diagram of the relationship between the discharge amount and pump diameter of a single suction pump and a double suction pump, with the horizontal axis representing the discharge amount and the vertical axis representing the pump diameter. In particular, in the circulation pump of the primary system of a liquid metal cooled fast breeder reactor (hereinafter referred to as FBR), reactor coolant circulation during coastdown after the pump trips during a reactor emergency shutdown is
From the viewpoint of ensuring R, the pump motor system is required to have rotational energy (oC rotational penetration GD2X rotational speed N') above a certain value. Now, as a design example, the relationship between the pump discharge sound, rotation speed, and GD, which was determined to ensure the pump coast down halving time of approximately 6 seconds or more in the event of an emergency shutdown of the nuclear reactor due to pump motor tripping, is plotted on the horizontal axis. Figure 14 shows the rotation speed on the vertical axis.

After satisfying the safety requirements, from an economic point of view
The following conditions are required for a BR primary system circulation pump.

(1) It must be small.

Double suction is advantageous. That is, from the comparison between FIG. 12 and FIG. 13, under the same conditions, the double suction pump can have a smaller pump diameter.

(2) High rotation speed and dual suction are advantageous. That is, as shown in FIG. 14, GDz can be reduced by increasing the rotation speed.

From the comparison between FIG. 10 and FIG. 11, under the same conditions, both suction pumps can achieve a higher rotational speed.

(3) The liquid level inside the pump can be maintained within a certain range J.

In the conventional Fermi type, the liquid level inside the pump fluctuates when the discharge amount is changed.

(4) Pump overflow treatment system 15 outside the pump
That there is no.

The Hallam type requires a pump over 70-treatment system 15 to return this flow to the pump suction side.

FIG. 15 is a sectional view showing a specific example of a conventional Hallam type. In the figure, 9 is a shaft seal, 14 is an intermediate casing, 2
2 is a differential user, 26 is a liquid level, and 27 is a gas convection prevention plate. The pump in Fig. 15 has the above (1), (2),
Condition (4) cannot be satisfied. In addition, Fig. 16 shows a Fermi-type primary main circulation pump, which is (3
) cannot be satisfied.

In connection with this type of pump, fast reactor technology (plant design)
logy (plant[)esign) * J, Q, 'fevick et.

al, ) M, T, T, Publisher (The M,
T, T, Press (PL73-175)) are known.

[Purpose of the invention]

The present invention has been made in view of the above situation.

The object of the present invention is to provide a primary main circulation pump for a liquid metal cooled fast breeder reactor that can reduce the range of pump liquid level fluctuation and downsize the pump without providing a pump overflow treatment system outside the pump.

[Summary of the invention]

The primary main circulation pump for a liquid metal cooled fast breeder reactor of the present invention includes an outer casing of a vertical shaft type mechanical pump for circulating liquid metal coolant, and a state fixed to a rotating shaft from the axial direction within the outer casing. an impeller of the pump that is attached and detached by the impeller; a hydrostatic bearing that is lubricated by the liquid metal driven by the impeller and is held in the outer casing and supports the rotating shaft;
a low-pressure pump lower tank chamber for accommodating the double suction type pump, and the outer casing is configured to divide the pump lower tank chamber and the pump upper tank chamber provided above the pump lower tank chamber. a partition plate removably attached together with the rotating shaft inside, a communication pipe that communicates the diffuser portion of the impeller and the pump upper tank chamber through an orifice located in the pump upper tank chamber, and the pump upper portion. A communication hole is provided which communicates the tank chamber with the pump lower tank chamber through an orifice located in the pump lower tank chamber. That is, a double-suction 7-hermi type circulation pump is used for the fast breeder reactor primary main cooling system circulation pump, and a partition plate is installed in the pump tank chamber to divide the pump upper tank chamber and the pump lower tank chamber.
A communication pipe from the bottom to the top and a communication hole from the top to the bottom are installed in this partition plate to lower the pressure due to the flow resistance of the liquid metal flowing due to the pressure difference between the upper and lower chambers, and to keep the liquid level in the pump within a certain range. It was designed to be preserved.

[Embodiments of the invention]

In the following, the primary main circulation pump for a liquid metal cooled fast breeder reactor according to the present invention will be described as an embodiment, and the same parts as those in the conventional system will be denoted by the same reference numerals as shown in FIG.
This will be explained with reference to FIG. In the figure, 2 is the orifice;
Reference numeral 6 indicates a communication pipe, 16 indicates a communication hole, 17 indicates an orifice, 23 indicates a balance hole, 24 indicates a guide vane, and 25 indicates a partition plate, which are rotatably formed on the rotating shaft 8. Outer casing 14
An inlet nozzle 4 is provided at the lower part of the pump, and a discharge nozzle 5 is provided at the side thereof, and the inside is separated into a pump upper tank chamber 7 and a pump lower tank chamber 19 by a partition plate 25. A high-pressure discharge casing 3 is fixed to an outer casing 14 inside the pump lower tank chamber 19 . The rotating shaft 8 is supported by a lubricated hydrostatic bearing 10 (installed in sodium chloride) and a receiver installed in a shaft seal 9 at the top of the pump. A two-stage impeller l having a balance hole 23 is attached to the lower part of the rotating shaft 8, and a diffuser 22 installed facing the outlet of the impeller 1 is connected to the hydrostatic bearing 10 via a guide vane 24. It is supported by a partition plate 25.

A communication pipe 6 connecting the pump upper tank chamber 7 and the position of the diffuser 22 on the discharge side of the impeller 1 is provided in the guide vane 24 . An orifice 2 is attached to the outlet of the communication pipe 6 in the pump upper tank chamber 7. In addition, partition plate 2
A communication hole 16 is penetrated through the pump lower tank chamber 1.
An orifice 17 is attached to the outlet on the 9 side.

The pump of this embodiment has a structure in which the internal structure can be pulled out leaving the outer casing 14 welded to piping (not shown), and the outer casing 14 and the internal structure are fixed to the outer casing 14. The diffuser 22 is separated from the discharge casing 3 at the fitting portion thereof. A seal ring is installed in this fitting part to provide a seal during normal operation of the pump.

The fluid metal sodium flows from the suction nozzle 4 at the lower end of the outer casing 14 to the pump lower tank chamber 1 of the outer casing 14.
9. Then, some of the sodium is sucked into the upper impeller 1 from below the lower impeller 1, and some sodium passes through the gap between the inside of the outer casing 14 and the outside of the discharge casing 3. The sodium pressurized by the impeller 1 merges in the discharge casing 3 and then flows out from the discharge nozzle 5. Pressurized sodium in the discharge casing 3 is supplied to the sodium-lubricated hydrostatic bearing 10, and the impeller 1 is equipped with a balance hole 23 in order to form a sodium lubrication flow path. There is.

By adopting such a structure, a sodium lubrication flow path is formed in which the sodium that has lubricated the sliding surface of the hydrostatic bearing 10 is returned to the suction side of the impeller 1 from the back surface of the impeller 1 through the balance hole 23. Ru. In addition, in the pump of this embodiment, since the pump lower tank chamber 19 has a low pressure, it is possible to return the sodium in the pump upper tank chamber 7 to the pump lower tank chamber 19 by self-cutting. The liquid level in the pump upper tank chamber 7 changes with the pressure change (pump suction pressure change) K.

In particular, when the pump of this example is adopted as a demonstration reactor class FBR Roug type cold leg pump, the suction pressure of the pump changes as the pump discharge amount, that is, the flow rate inside the loose, changes to the suction pressure when the pump is stopped. About θ~-10
Varies in the mNa range.

This is due to the Loog pressure drop from the furnace vessel to the pump inlet, but if this change in suction pressure were to be absorbed by this pump as a fluctuation in the liquid level inside the pump, the axial length of the pump would become significantly longer, resulting in a large This is undesirable because it leads to distortion and reduces reliability.

For this reason, in this embodiment.

0) By sealing and isolating the suction flow path at the lower part of the pump and the pump upper tank chamber 7, a structure is created in which the sodium liquid level in the pump upper tank chamber 7 does not change in conjunction with changes in pump suction pressure.

Specifically, a seal ring is installed between the outer casing 14 and the internal structure, and a labyrinth structure is used to seal between the rotating shaft 8 and the fixed side. It is set up.

(b) The pump upper tank chamber 7 and the impeller discharge side are connected by a communication pipe 6 provided on the guide vane 24, and an orifice for flow rate control is installed at the end of the communication pipe 6.

(c) Suction channel at the bottom of the pump and tank chamber 7 at the top of the pump
are connected through a communication hole 16, and a flow rate control orifice 17 is installed at the end of the communication hole 16.

Here, in (b) and (c) above, the seal between the suction channel at the bottom of the pump and the tank chamber 7 at the top of the pump in (a) cannot completely isolate the respective spaces, so the liquid level inside the pump required to control. This principle will be explained below. In this embodiment, the flow rate of IJum flowing through the communication pipe 6 between the pump upper tank chamber 7 and the discharge side of the impeller 1 is Ql, and the communication hole between the pump lower suction channel and the pump upper tank chamber 7 is 16 ft of flowing sodium
If Q z , then Qt = + ・2g (Hd−
H,) −(1)Q2=2・2 g (H,−
H, )...(2) However, +1: Flow coefficient of orifice 2 of liaison officer 6, K2: Flow coefficient of orifice 17 of communication hole 16, Hd: Pump discharge amount 8 (m) T (d=H , +H... (3) Hl: Lift height of pump upper tank chamber 7 (m), H, = H,.-L
・・・・・・・・・(4) H3: Pump suction head (m) H,=H,. -HtxQ2/around ・・・・・・・・・(
5) Hl. : Pump suction head when the furnace is stopped (m) Hl: Pressure drop between the furnace vessel and the pump inlet when the pump is in rated operation (m) Qo : Pump rated discharge amount Q : Pump discharge amount H: Pump total head L : NsL ~ Pump liquid Distance to the plane (1) and (2
), equation (6) becomes (3), (4),
From equation (s), it can be determined as follows.

Here, during rated pump operation, the pressure drop H1 between the furnace vessel and the pump inlet is 7 m, and the conditions under which the liquid level fluctuation range in the pump is 4 m or less are determined from equation (7), and the flow coefficient ratio of orifice 2 and orifice 17 is determined. , K 1 / K z is 0.3, the operation range shown by diagonal lines in Fig. 4 of the diagram for explaining the operation range determined by the control of the liquid level in the pump, where the horizontal axis represents the discharge amount and the vertical axis represents the total head. The condition that the range is possible is required. This operating range can sufficiently satisfy the operating range required for the primary main circulation pump.

As mentioned above, in the 7-hermi type pump, the above (a),
By configuring as in (b) and (c), fluctuations in the liquid level within the pump can be reduced. That is, by providing the communication pipe 6 and the communication hole 16 and adjusting the size of the communication portion as appropriate, it is possible to connect the pump lower tank chamber 19 to the pump upper tank chamber 7 and from the pump upper tank chamber 7 to the pump lower tank chamber 19. The pressure can be lowered by the flow resistance when the fluid moves to the bonder liquid level, and the width of bonder liquid level fluctuation can be reduced. Therefore, the length of the pump is shortened, and the cost of the pump can be reduced.

In this way, the primary main circulation pump of the liquid metal cooled fast breeder reactor of this embodiment has a partition plate that divides the inside of the outer casing into a pump lower tank chamber containing a built-in pump part and a pump upper tank chamber. A communication passage and a communication hole are provided to communicate between the impeller dihyuser part and the upper tank chamber of the pump, and between the upper tank chamber of the pump and the lower tank chamber of the pump, respectively, so that the pressure is reduced by the flow resistance during fluid flow due to the pressure difference. The range of fluctuation in the pump liquid level can be reduced by eliminating the need for a pump over 70-processing system outside the pump.

In addition, the pump can be made smaller and economical efficiency can be improved.

FIG. 3 shows another embodiment. In this embodiment, a needle valve 18 that can be operated from the outside is installed and operated in the orifice 2 for controlling the flow rate of the above embodiment, thereby satisfying equation (7).

2 can be adjusted to Kl/. Therefore, in this embodiment, if the liquid level fluctuation range 21 in the pump after the start of operation is significantly different from the original plan, it is possible to reset it to a predetermined fluctuation range by operating the needle valve 18. In addition, it has the same effects as the above embodiment.

〔Effect of the invention〕

As described above, 1 of the liquid metal cooled fast breeder reactor of the present invention.
The secondary main circulation pump has the effect of eliminating the need for a pump over 70-processing system outside the pump, reducing the width of pump liquid level fluctuation, and making the pump more compact.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view of an embodiment of the primary main circulation pump for a liquid metal cooled fast breeder reactor according to the present invention, Fig. 2 is a detailed view of section A in Fig. 1, and Fig. 3 is a liquid metal cooled fast breeder reactor according to the present invention. A detailed view of the N section in FIG. 1 of another embodiment of the primary main circulation pump for a fast breeder reactor, FIG. Figure 6 is an explanatory diagram of Hallam type and Fermi type mechanical pumps for driving the circulation of liquid metal, Figure 7 is a schematic illustration of the primary main cooling system of the Halumi type pump in Figure 5, and Figure 8 is an explanatory diagram of the single suction pump of the pump in Figure 6, Figure 9 is an explanatory diagram of the double suction pump of the pump in Figure 6, and Figures 10 and 11 are the single suction 9 of the pump in Figures 8 and 9, respectively.
Characteristic diagram of the relationship between the discharge amount and rotation speed of both suction pumps, 1st
Figures 2 and 13 are explanatory diagrams of the relationship between the discharge amount and pump diameter of the single-suction, single-suction pump shown in Figures 8 and 9, respectively, and Figure 14.
The figure is an explanatory diagram of the discharge amount, rotational speed, and rotational inertia of a conventional liquid metal circulation pump, and FIGS. 15 and 16 are explanatory diagrams of conventional Hallam type and Fermi type pumps, respectively. 1... Impeller, 2.17... Orifice, 6...
Communication pipe, 7... Pump upper tank chamber, 8... Rotating shaft, 10... Static pressure bearing, 14... Outer casing, 16
...Connection hole, work 8...needle valve, 19...pump lower tank chamber, 1st figure, 2nd port, 30th 4th day yesterday - 1 failure (K'/,,ru) 5th prison committee Otsu Kunime δ mouth 1st θ mouth O length withdrawal Bon-l Nitontaku AH [r buttge γlπ) 12th (3(2) of: amount (J/B; 71) U my amount (* J/$7 Lord Tsuji (S mouth

Claims (1)

[Scope of Claims] 1. An outer casing of a vertical shaft mechanical pump for circulating liquid metal coolant, and an impeller of the pump that is attached to and removed from the outer casing while being fixed to the rotating shaft from the axial direction. a hydrostatic bearing lubricated by the liquid metal driven by the impeller and held in the outer casing to support the rotating shaft; and a low-pressure pump lower tank chamber housing the dual-suction type pump. a partition plate removably attached to the outer casing together with the rotating shaft to divide the pump lower tank chamber and the pump upper tank chamber provided above the pump lower tank chamber; A communication pipe that communicates the diffuser portion of the impeller and the pump upper tank chamber through an orifice located in the pump upper tank chamber, and a communication pipe that communicates the pump upper tank chamber with the pump lower tank chamber and the pump lower tank chamber. 1. A primary main circulation pump for a liquid metal cooled fast breeder reactor, characterized in that it is provided with a communication hole that communicates with an orifice interposed therebetween. 2. The high-speed liquid metal cooling system according to claim 1, wherein an externally operable needle valve is provided opposite to the upper opening of the connecting pipe that protrudes from the partition plate to the upper tank chamber of the pump. Primary main circulation pump of a breeder reactor.