JPS62148891A - Electromagnetic flow diode - 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 an electromagnetic flow diode that uses a conductive fluid as a working fluid and restricts the flow of the fluid in only one direction.

[Background of the invention]

In various fluid systems, there is a desire for the emergence of flow diodes with low pressure loss and high rectification ratios, which are equivalent to diodes in electrical circuits and which control the flow of fluid in one direction. An example of a fluid system that has particularly great demands is the primary main cooling system of a liquid metal cooled fast breeder reactor. Figure 2 is a longitudinal cross-section of a tank-type liquid metal cooled fast breeder reactor, showing the flow of the -order main cooling system.
The primary coolant (liquid metal sodium) discharged from the pump 1 passes through the discharge noip 2 and enters the high-pressure plenum 3 at the bottom of the core.
After being heated in the reactor core 4, it enters the upper Blenheim 7,
A circulation loop is formed in which heat is transferred to the secondary system via the intermediate heat exchanger 5, then returned to the lower blemish 6, and sent to the reactor core 4 again by the primary main circulation pump 1.

A tank-type fast breeder reactor with a full-scale (1000 MWe) class output is composed of 3 to 4 loops due to loop scale constraints for plant controllability, and each loop is equipped with a secondary main circulation pump 1 and An intermediate heat exchanger 5 is provided. During normal reactor operation, all loops are in operation, but if for some reason one of the primary main circulation pumps is triggered, the core flow rate decreases and the core cooling capacity decreases. The temperature of the primary sodium at the outlet increases abnormally. This situation results in excessive thermal stress on the structures in the upper Blenheim region. This is the so-called thermal shock caused by the N-1 pump trigger accident. However, in this accident, the core flow rate actually not only decreases to (N-t)A' (N is the number of loops) but also decreases further due to backflow. The reason for this will be explained using FIG. 3.

Figure 3 shows two primary main circulation pumps 1 and 1' of the plurality of primary circulation pumps arranged in the furnace vessel (tank) corresponding to the plurality of loops, and an illustration of the intermediate heat exchanger. is omitted. During normal operation, the secondary coolant flows in the direction indicated by the solid arrow, forming the aforementioned circulation loop. Each discharge/mother pump 2, 2' is connected to the high-pressure blenum 3 at the bottom of the core, and each primary main circulation pump 7'l,
1' sucks primary sodium from the suction parts 10 and 10' and sends it to the high-pressure blenum 3 via the discharge pipe 2.2'. The primary sodium pumped into the high-pressure blennium 3 joins there and flows into the reactor core 4. N
-171e engine trip accident occurs (here, -
It is assumed that the secondary main circulation cylinder f1/ has tripped), and the pressure loss in the reactor core 4 is large (approximately 8 ky/crt?).
The discharge pressure of healthy pumps other than the faulty pump f1' is
The flow path is directed to the failed bomb f1' side, which has a lower pressure loss, and flows backward through the discharge via '2'. Therefore, as shown by the dashed arrow in the figure, the primary sodium sucked from the suction section 10 of the healthy pump 1 passes through the high-pressure blemish 3 to the suction section 10 of the failed pump 1'.
′ forms a loop that is released from ′. When this happens, the failed pump f1' rotates from normal rotation to reverse rotation, turning into a water wheel.

It is supported by the complete characteristic curve of the pump that the phenomenon of turning the pump into a water wheel generally results in a negative flow rate and rotation speed exceeding the 100-inch output. Figure 4 shows the flow rate and rotational speed characteristics in a running speed state (unrestricted state) where the rotational force of the shaft of a pump converted into a water wheel is not restrained.
and β differ depending on the shape of the pump, etc.
In general, it can range from 10 to 50 inches. Therefore, if one primary main circulation pump fails, the core flow rate will be (N −
2.1~2.5)/N, N=4
This corresponds to a decrease of approximately 48% to 38% compared to the normal core flow rate. Therefore, unless some kind of effective backflow prevention mechanism is installed, the reactor is forced to scram.

Since the backflow prevention mechanism must be installed deep within the furnace vessel and below the bulkhead structure 13, maintenance is almost impossible, so it needs to have a simple and passive structure.

As such, a conventional structure type flow diode shown in FIGS. 5(A) and 5(b) can be considered. All of these have a structure that allows fluid to easily flow in one direction, and there are also those with a spiral structure, but the disadvantage of these structural type flow diodes is that they have a poor rectification ratio. In order to improve the rectification ratio, the structure must be dense and complicated.
There is a problem in that the pressure loss in the flow path increases significantly.

In addition, a prior art technique has been proposed in Japanese Patent Application No. 59-114588 that prevents the pump from turning into a water wheel even if reverse flow occurs. This prior art is as shown in FIG. 6, in which a DC generator 18 is connected to the shaft of the pump 1 via a coupling 17 in addition to a main motor 19, and an electrical output terminal 24 from the DC generator 18 is connected to the shaft of the pump 1 via a coupling 17. is a diode circuit 21 and a braking resistor 22
is connected. During normal rotation, diode circuit 2
1 is off and there is no load on the generator 18, but when the reverse rotation occurs, the diode circuit 21 is on and power is consumed on the braking resistor 22 side, and the reaction force overloads the DC generator 18. act as a brake on rotational force. In this prior art, an electromagnetic braking force proportional to the reverse rotation speed is applied, so it is possible to prevent the pump from turning into a water wheel. However, since backflow through the discharge via 2 cannot be prevented, the suction section 10 of the failed pump
The release of primary sodium from the reactor is unavoidable, and the core flow rate decreases by that amount. In addition, the backflow force is always applied to the inlet cover of the failed pump, which is counterbalanced by the force trying to stop the impeller, so the impeller is always under load, which is not desirable. do not have.

[Purpose of the invention]

The object of the present invention is to provide a high rectification ratio suitable for use in a fluid system in which a conductive fluid such as a conductive fluid (for example, used in a fast breeder reactor) flows. The object of the present invention is to provide a flow diode with low pressure loss.

[Summary of the invention]

The flow diode of the present invention places a magnetic field in a direction perpendicular to a conductive fluid flowing in a flow path, and electrically connects a part of the current circuit in the fluid through which a current induced by Fleming's right-hand rule passes. By installing a diode mechanism so that the induced current flows only in one direction, the electromagnetic braking force works only against fluid flow in the opposite direction, and the electromagnetic braking force works against fluid flow in the forward direction. It prevents force from working.

[Embodiments of the invention]

An embodiment of the flow diode of the present invention is shown in FIG.

FIG. 5A shows a radial cross section, and FIG. 1B shows an axial cross section of the upper half. The flow diode of this embodiment has an annular structure, and has a permanent magnet 25 on the inside and a magnetic material 26 on the outside. , the portion facing the flow path 33 is sealed with an insulating material 28. If two partitions 27 are installed to divide the flow path 33 into two in the radial direction, this partition 2
Reference numeral 7 constitutes an electrical diode mechanism in which a diode portion 30i is sandwiched between two conductive plates 29.

31 is a covering material, and 32 is a pipe connected to the present flow diode.

The fluid flows in the flow path 33 in the axial direction, and the direction of the magnetic flux B from the magnet 25 is radially outward, and an electromotive force is induced in the circumferential direction according to the right-hand rule of Shihung. Partition 2
7, an electromagnetic braking force due to the ring current generated by the electromotive force would be applied to both forward and reverse fluid flows. On the other hand, by installing the partition 27 constituting the electric diode mechanism as described above, the current is blocked by the partition 27 and does not flow despite the electromotive force, and the electromagnetic brake Although no force is applied, the current due to the electromotive force flows through the partition 27 to form a ring current against reverse flow, and an electromagnetic braking force is applied to prevent reverse flow.

Typical structures of the electrical diode mechanism section include (1) one using a semiconductor rectifying element, and (2) a differential pressure operating type. For the former, polycrystalline semiconductors such as selenium and cuprous oxide, silicon, and high-temperature resistant GaAs (humidity resistant to 450°C) and gallium-su7 GaP (humidity resistant to 1000°C) can be used as semiconductors. , an example of its structure is shown in FIG. 7(a).

Shown in (b). In order to improve the rectification characteristics, a large number of diode elements 42 are constructed by using the semiconductors described above and reinforcing the rectifying jackets with ppn junctions, pnn junctions, and junctions with support plates as shown in FIG. 7(b). ) A substrate 34 of insulating material as shown in
The boards 30 arranged above are sandwiched between conductive plates 29 from both sides as shown in FIG. 7(a) to form a sandwich structure.

Each diode element 42 shown in FIG. 7 is an example of a flat rectifier diode, and its details are as shown in FIG. The device is mounted on a support plate 39, sealed with a seal 38, and embedded in an insulating substrate 34.

Differential pressure operated types take advantage of the fact that dynamic pressure increases when the direction of flow is reversed, and can be thought of as gas-filled types or those that use a piston-shaped switching mechanism.
Here, a gas-filled type will be explained as an example. FIG. 9 is a schematic diagram for explaining the structure and operation of the gas-filled type, and FIG. 9 (at is a radial sectional view, and FIG. 9(b) is an axial sectional view.

In this embodiment, a gap 41 is provided in the middle of the conductive plate 29 of the partition 27, and a gas is sealed therein.

34 is an insulating plate sandwiched between the conductive plates 29. Cavity part 41
is connected to the flow path 33 via a binoculars flow path 40. As shown in the figure, the pinos flow path 40 has a structure in which forward flow is blocked from flowing in, but h1 reverse flow is easily allowed to flow in. The internal pressure of the sealed gas is adjusted so that the liquid level in the pi/ips flow path 40 is at the solid line position during forward flow. In such a state, if backflow occurs for some reason, the dynamic pressure of the backflow will be applied to the gas-liquid interface due to the structure of the bypass flow path 40.
The filled gas is compressed and the liquid level rises to the position indicated by the dashed line.

Therefore, during normal flow, the partition 27 is electrically insulated by the void 41, and during reverse flow, the partition 27 becomes conductive as the conductive fluid flows into the void 41, operating as an electrical diode mechanism.

Incidentally, it is actually better to arrange a large number of the above-mentioned differential pressure operating types as shown in FIG. 10, thereby achieving a better backflow prevention effect.

A trial calculation will be made to determine whether sufficient electromagnetic braking force can be obtained when the flow diode shown in the above embodiment is applied to the tank-type fast breeder reactor shown in FIG.

The flow diode is connected in the middle of the discharge pipe 2 of each secondary main circulation pump 1. The pressure loss due to the electromagnetic brake is expressed by equation (1).

p = ty-u fLB at -
・-(1) Here, σ: Electrical conductivity of fluid C87m)
, U: average flow velocity (m/5ee), B: magnetic flux density [Wb/
rn2], L: magnet length [m]. If the magnetic field is uniform over the entire length of the magnet, p=σ・u−B2・L ・・・・・・
・It can be rewritten as in (2). In a tank-type fast breeder reactor, the pressure loss in the reactor core is approximately 0.8 MPa, and if the pressure loss of the electromagnetic brake due to backflow is sufficiently larger than this, the coolant sodium will not flow back to the failed pump and will be completely transferred to the core side. It will flow to If the cross-sectional area of the flow diode is the same as that of a conventional discharge pipe, the average flow velocity is u
=7.64m/sec. The currently available magnetic flux density B=0.5 Wb/m (for example, alnico) is used, and the magnet length is 1 m. The electrical conductivity σ varies depending on the temperature, but using the value when the temperature of the lower plenum is 350°C, in the case of sodium, σ = 5 × 10' 87
m. Substituting the above values into formula (2) and calculating,
Electromagnetic braking force p per unit length of magnet 9.5
It can be seen that a sufficient pressure loss can be obtained at 5 MPa. However, when using semiconductors, the u, B, L
needs to be adjusted to an appropriate value.

In this way, if the flow diode of the present invention is applied to a tank-type fast breeder reactor, it will be a flow diode with a very good rectification ratio, with no resistance to forward flow and a braking force only applied to reverse flow. However, the backflow is stopped within the discharge pump, no load is placed on the stopped pump, and the core flow rate drop can be kept at (N-1)/N. Additionally, the flow diode itself has no moving parts and is completely passive (
Because it has a passive structure, the probability of failure is extremely low, maintenance is unnecessary, and it is highly reliable, meeting the requirements of tank-type fast breeder reactors. Another effect is that since the core flow rate decreases by only (N-1), it is no longer necessary to immediately scram the reactor with the primary pump trip as in the past. That is, it can be easily predicted from past experience that negative pump trigs are overwhelmingly more likely to be caused by a failure in the electrical system than by a mechanical failure in the main body. This means that there are a considerable number of pump failures that can be repaired even during reactor operation, and it is more efficient to not shut down the reactor in the event of such a failure. Therefore, if the flow diode of the present invention is installed, it will be possible to shift to reduced output operation when the next pump trips, investigate the cause of the pump trip, and determine whether or not to scram the reactor based on the repair details of the failure. This allows for the adoption of better reactor operating methods, leading to improved reactor operating efficiency. Thus, it can be said that the flow diode of the present invention is suitable as a backflow prevention mechanism for a pump of a tank-type fast breeder reactor.

In the case of a fast breeder reactor of a loop type rather than a tank type, a check valve is conventionally attached to a part of the secondary system piping to prevent backflow, but the flow diode of the present invention can be used in place of this check valve. When the flow diode of the present invention is provided all around the device, the generation of impact pressure, that is, the water hammer phenomenon that occurs when a check valve is operated, does not occur, and excessive impact force on the equipment can be prevented.

Note that as another example of the partition 27 having an electric diode configuration using a semiconductor rectifying element, a structure shown in FIG. 11 can be considered. In this embodiment, a large-sized rectifying pellet plate 35 is used as is, with a tungsten plate 36 and a copper plate 37.
A sandwich structure is formed by sandwiching the two conductive plates 29 between conductive plates 29.

Rectifying diodes using semiconductors have a limited allowable current value, and when a large current flows, such as when preventing backflow in a tank-type fast breeder reactor, the cross-sectional area of the diode element 42 shown in Fig. 7 is large. Moderately good. The structure shown in this embodiment was conceived from this point of view, and has the advantage that the current density flowing through the diode can be reduced. Polycrystalline semiconductors, which can be produced by vapor deposition, are considered to be a promising material for the large-sized rectifying pellet plate used in this example.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide a flow diode that has OJ performance applicable to fluid systems using conductive fluid, has a large rectification ratio, and has low pressure loss for forward flow.

Moreover, since this flow diode has no moving parts and has a single, completely passive structure, it requires no maintenance and is highly reliable.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) are radial and axial cross-sectional views, respectively, of a flow diode according to an embodiment of the present invention;
Figure 2 is a longitudinal sectional view of a tank-type fast breeder reactor, Figure 3 is a longitudinal sectional view of a tank-type fast breeder reactor to explain the flow of primary coolant due to failure of the primary main circulation pump, and Figure 4 is a longitudinal sectional view of a tank-type fast breeder reactor. A characteristic curve diagram of the main circulation pump, FIGS. 5(a) and 5(b) are axial cross-sectional views of a conventional structural flow diode, and FIG. 6 is a diagram showing the invention proposed in Japanese Patent Application No. 114588/1983. 7(a) and 7(b) are perspective views respectively showing the overall structure and partial structure of the partition in FIG. 1 in the case of a semiconductor type, and the structure of the diode element in FIG. 8Fi and FIG. 7(b). 9(a) and (b) are cross-sectional views showing the first
A radial cross-sectional view and an axial cross-sectional view of a flow diode according to an embodiment of the present invention when the partition in the figure is a differential pressure operated type, and FIG. 10 shows a practical aspect of the flow diode shown in FIG. FIG. 11 is a perspective view showing another embodiment of a semiconductor type partition. 1...Reactor core, 2...Discharge pipe, 3
...High pressure blennium, 4...Reactor core, 5...Intermediate heat exchanger, 6...Lower blennium, 7...Upper brenum, 10...Suction part, 13...
・Bulkhead, 14...Roof slab, 17・
...Shaft coupling, 18...DC generator, 19...Main motor, 2
1... Diode circuit, 22... Braking resistor, 24...
...Electric output terminal, 25...Permanent magnet, 26...
・Magnetic material, 27... Partition, 28... Insulating material, 29... Conductive plate, 30... Diode part, 31... Covering material, 32... Piping,
33... Channel, 34-... Insulating material substrate,
35... Rectifier cover, 36... Tungsten (or molybdenum) plate, 37... Copper plate, 3
8... Seal part, 39... Support plate, 40
... pie gas flow path, 41... void part,
42...Diode element. Fig. 1 (α) Fig. 1 (b) Fig. 3 Fig. 4 Fig. 5 (α) (b) Fig. 6'2 I, approx. (b) System 11 diagram

Claims (1)

[Claims] a flow path through which an electrically conductive fluid flows; means for generating a magnetic field within the flow path that crosses the flow of the fluid; and means for generating an induced current in the fluid flowing through the flow path due to the magnetic field. An electromagnetic flow diode comprising a partition installed in a flow path, the partition forming an electrical diode mechanism that allows the induced current to pass in only one direction across the partition.