JPS61237901A - Steam generator - 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 steam generator in an intercooling system of a liquid metal-cooled Toko reactor, and is particularly suitable for use in a cooling system that needs to absorb expansion and contraction of a coolant. Concerning a suitable steam generator.

[Background of the invention]

A prior art example of a secondary main cooling system for a sodium-cooled fast breeder reactor is shown in FIGS. 2 and 3. FIG. 2 shows an outline of a 92nd main cooling facility using an expansion tank 2, and is composed of a secondary main circulation pump 1, an expansion tank 2, a steam generator 3, and piping. The secondary coolant is discharged from the secondary main circulation pump 1, enters the tube side of the main intermediate heat exchanger 4, receives heat from the coolant of the primary deep cooling system flowing on the shell side, and is pulsated.

The secondary coolant discharged from the main intermediate heat exchanger 4t enters the steam generator shell side, exchanges heat with water and steam on the tube side, and returns to the secondary main circulation pump 1. The secondary main pump 1 is a mechanical vertical free liquid level centrifugal pump, and a portion of the secondary coolant flows out from a hydrostatic bearing at the bottom of the pump and returns to the piping via an expansion tank 2.

The purpose of installing the expansion tank 2 is to absorb expansion and contraction of volume due to temperature changes of the secondary coolant, and according to a design example, it is very large, with a diameter of about 4 m and a height of about 6 m.

Figure 3 shows an outline of the secondary main cooling system equipment using a coolant overflow system.

The sodium liquid level in the secondary main cooling system is increased by the overflow from the secondary main circulation bong 1 and the pumping up of the sodium in the overflow tank 6 by the pumping electromagnetic pump 5! It absorbs the expansion and contraction of the secondary coolant due to counter-change and is kept constant. In this system configuration, the expansion tank 2 is removed, but an overflow tank 6, an electromagnetic pump for pumping, 5, piping valves, etc. are added.

In Figures 2 and 3, the secondary system cover gas pressure is kept within a constant pressure range by the secondary argon gas system 10 to prevent radioactive substances in the primary system from transferring to the secondary system via the intermediate heat exchanger. is controlled by.

The secondary argon gas system equipment 10 includes a secondary main circulation pump 1,
This is equipment that handles inert argon gas that covers the free liquid surface of equipment including secondary coolant such as expansion tank 2,
Consists of vapor traps, tanks, piping, valves, etc.

In addition to controlling the cover gas, this equipment replaces argon gas in the secondary main cooling equipment, etc., and supplies seal gas to the secondary main circulation pump.

FIG. 4 shows an example of the structure of the helical coil steam generator 3.

It consists of a group of heat transfer tubes and other internal structures that are the heat exchange part of the steam generator, and a shell that houses them.

Sodium is introduced into the shell from the inlet nozzle 11, enters the heat transfer tube group 12, descends between the inner cylinder 13 and the shroud 14, and flows out from the outlet nozzle 15. The water/steam side is introduced into the main body through a ladder 16 to the ring. Further, it passes through the helical coil portion 12 and flows out to the ring on the upper part of the body via the rudder 17.

Note that the inner cylinder interior 13 is filled with stationary liquid sodium and is a part that does not contribute in any way functionally, and according to a design example, has an inner diameter of about 1 m or more and a length of about 15 m.

The conventional secondary main cooling system described above is of a type in which the expansion/contraction of the coolant performance of the system is absorbed by an expansion tank 2 branched from the secondary main cooling system or by a secondary overflow system. .

Such conventional secondary main cooling systems often have the following drawbacks.

■ Increased equipment An expansion tank branched off from the main cooling system, piping, and its attached equipment/primary or secondary overflow system equipment, piping, and attached equipment were required, and the amount thereof was enormous. Furthermore, a large amount of equipment and equipment was required to install these equipment.

■Increase in installation space and building Same as in ■K, as rapid expansion tank 2 or secondary overflow system is installed by branching from the main cooling system, more space is required for installation, and the building becomes larger accordingly. There was a drawback.

Such a major disadvantage in terms of economic efficiency is a very serious problem for the development of fast breeder reactors, and some kind of solution is required.

[Purpose of the invention]

An object of the present invention is to provide a secondary main cooling system that can significantly reduce equipment and space such as the expansion tank 2 or overflow system, and is very economically effective.

[Summary of the invention]

The present invention focuses on the effective use of the space existing inside the inner cylinder 13 of the steam generator, and uses this space to change the liquid level position 19 depending on the system temperature. By absorbing the amount of water, the above purpose can be achieved.

[Embodiments of the Invention] Examples of the present invention will be described with reference to FIGS. 1 and 5. (
The present invention is suitable for helical coil type steam generators. ) FIG. 1 shows an outline of the steam generator of the present invention. The feature of the present invention is that in the conventional steam generator shown in FIG.
3 is provided with a gas space, and the gas volume is changed by the gas pressure control system 18 to absorb the expansion and contraction of the coolant in the system, thereby eliminating the expansion tank 2 and secondary overflow system in the conventional example shown in Fig. 3. It's about doing.

FIG. 5 shows an outline of the secondary main cooling system and gas pressure control system 18 having this steam generator.

It is. In the secondary main cooling system, the relationship between temperature and volume when the charged coolant is kept constant, and the relationship between the liquid level in the inner cylinder when it is absorbed in the internal space of the inner cylinder in the steam generator is shown in Figure G6. Shown below. In the design example, Na in the secondary cooling system
The amount is approximately 250 m'' for rated operation, and it is necessary to consider the change in volume of the coolant to be approximately 15 m1, but as shown above, the inner cylinder space 13 is comparable to this.

Now, considering that the plant is in a low-temperature shutdown state, the secondary main circulation pump 1 is operating at low speed to remove decay heat, and the liquid level 20 inside the secondary main circulation pump 1 is maintained at a certain level. There is. At this time, the sodium is at a low temperature and the sodium in the secondary main cooling system has contracted compared to during rated operation, so the pressure of the cover gas inside the steam generator inner cylinder 130 is increased and the liquid level 19 is lowered. As a result, the sodium chloride in the system is supplied from here.

When the plant is transferred from this state to rated operation, the sodium in the secondary main cooling system increases in temperature and expands.

The cover gas pressure of the secondary main circulation pump 1 is controlled to a constant pressure by the secondary argon gas system 10 so that radioactive substances in the primary system do not transfer to the secondary system via the intermediate heat exchanger 4. At the same time, argon gas is constantly circulated at a constant flow rate for shaft sealing. If the liquid level 19 in the inner cylinder 13 of the steam generator is kept constant due to sodium expansion in the secondary main cooling system, the liquid level 20 in the secondary main circulation pump 1 will rise and exceed the allowable value. Therefore, the following system is implemented.

Secondary main circulation pump internal liquid level detectors 21A, 21B.

21C (it is better to use a multiplexed signal to improve reliability b0, for example, 2out3) to detect the liquid level height and output the signal to the control device 22. The control device 22 receives the signal of the liquid level and opens the automatic valve 24 of the pressure reduction line 23 installed in the internal space 13 of the steam generator inner cylinder. The cover gas in the inner space 13 of the steam generator inner cylinder is passed through the reduced pressure inlet 23 and
Next, the gas is sent to the exhaust header 26 through an argon gas-based paper trap 25t and released into the atmosphere.

゛・The pressure of the 130 cover gas inside the steam generator inner cylinder is
, the pressure is reduced by the operation, and the sodium liquid level 19 rises.

When this liquid level rise absorbs the expansion of the sodium in the secondary main cooling system, the liquid level 20 of the secondary main circulation pump 1 returns to the normal liquid level, and the liquid level detectors 21A, 21B, 21C A normal liquid level signal is output to the control device 22. The control device 22 receiving the normal liquid level signal operates the automatic valve 24 of the pressure reduction line 23.
is closed.

If the automatic valve 24 of the pressure reducing line 23 fails to open when the signal of the liquid level of the secondary main circulation pump 1 is output, the liquid level 20 in the secondary main circulation pump will further rise. A liquid level detector 21A is used as a countermeasure.

218 and 210 to output a signal indicating the high liquid level, and the automatic valve 28 of the pressure reduction line bypass 27 is opened.

FIG. 7 shows the relationship between the liquid level of the secondary main circulation pump and the exhaust and supply of gas in the internal space of the inner cylinder of the steam generator.

Automatic valve 2 for pressure reduction line 23 and pressure reduction line bypass 27
4 and 28 have different power supply types to ensure reliability, and one of them always closes a normally operating valve train.

In addition, when the plant is transferred from the rated operating state to the low-temperature shutdown state, contrary to the above, the temperature of the sodium in the secondary main cooling system decreases and contracts, so the liquid level 20Vi of the secondary main circulation pump 1 decreases.
descend.

The liquid level detectors 21A, 21B, and 21C output low liquid level signals, and the internal space 13 of the steam generator inner cylinder is controlled via the control device 22.
The automatic valve 30 of the pressurization line 29 installed in the pressurization line 29 is opened.

Argon gas is supplied to the steam generator inner cylinder internal space 13 from an argon gas supply system 31 via a secondary argon gas system (argon gas supply header 35, etc.) and through a pressurization line 29.

The cover gas pressure inside the steam generator inner cylinder 13 is increased by this operation, and the sodium liquid level 19 is lowered.

When this liquid level drop absorbs the shrinkage of the sodium in the secondary main cooling system, the liquid level 20 of the secondary main circulation pump 1 returns to normal, and the automatic valve of the pressurizing line 29 is closed.

As with the pressure reduction side, a pressurization line bypass 32 is provided so that an automatic valve 33 opens when the liquid level is high. Further, the two automatic valves 28 and 33 also have different IEijX.

By these operations, the liquid level 20 in the secondary main circulation pump can be set within the range shown in FIG. - In addition, a liquid level detector 34A is installed in the steam generator inner cylinder internal space 13,
By installing 348.34C (to improve reliability, three of them are installed, similar to the liquid level detector of the secondary main circulation pump mentioned above), it is also possible to implement measures against malfunctions of the pressure control system as described below. . That is, when the sodium liquid level 19 in the inner cylinder internal space 13 rises excessively, a liquid level bulky signal is sent to the control device from the nine multiplexed steam generator dark internal space liquid level detectors 34A, 348, 35B. 22. When the control device 22 receives this signal, it closes the automatic valves 24 and 28 of the pressure reduction line 23 and the pressure reduction line bypass 27, and
Automatic valve 3 for pressurization line 29 and pressurization line bypass 32
Let's open 0.33. By this operation, the automatic valves 30 and 33 are closed when the liquid level 19 in the internal space of the steam generator inner cylinder returns to the normal fluctuation range (outputs a signal below the liquid level height).

If the steam generator inner cylinder internal space liquid level 19 drops abnormally, the steam generator inner cylinder internal space liquid level detectors 34A, 3
Signals indicating low and low liquid levels are input to the control device from 4B and 34C. The control device receives this signal and, contrary to the above, automatically activates the automatic valves 24 and 2 of the pressure reduction line 23 and the pressure reduction line bypass 27.
8 is opened, and the automatic valves 30, 3°3 of the pressurizing line 2.9 and the pressurizing line bypass 32 are closed. By this operation, when the steam generator inner cylinder internal space liquid level 19 returns to the normal operating range (outputs a signal indicating that the liquid level is low), the automatic valve 2
4.28 is closed.

As described above, it is possible to prevent an abnormal rise or fall in the liquid level in the space inside the inner cylinder of the steam generator.

Figure 8 shows each automatic valve 24 during secondary main circulation pump liquid level control.
, 28, 30, and 33 are shown in their open and closed states.

For example, focusing on the automatic valve 24 (Vl), when the secondary main circulation pump liquid level is below the reference value, it is in the closed state 36. When the liquid level rises and exceeds the liquid level high, this automatic valve 24 (
Vl) is in the open state 37, and the liquid level drops as described above. When the liquid level drops to the reference value, the automatic valve is again in the closed state 36. In addition, other automatic valves 28 (V2),
30 (V3).

Similarly, for 33 (V4), its open/closed state and 2
This shows the relationship between the main circulation pump liquid level.

FIG. 9 shows a logic circuit within the control device 22. As shown in FIG.

An explanation of this figure focusing mainly on the area around the automatic valve 24 will be given below.

Secondary main circulation pump internal liquid level detectors 21A, 21B.

When a liquid level signal is output from at least two of the 21C, a signal is output from the 2 out of 3 circuit 38. (By constructing such a circuit, automatic valve wA operation due to erroneous signal output from one liquid level detector and liquid level detector 1
When the automatic valve needs to be activated due to book failure or stoppage, it can prevent inoperation. ) 2 out of 3 The signal output from the circuit 38 is O
It passes through the R circuit 39, enters the drive device for the automatic valve 24, and opens the automatic valve 24. At this time, there is a memory circuit 40 that stores the output signal around the OR circuit 39, and the signal to open the automatic valve 24 continues until the signal is manually input from the memory removal circuit 41, and the signal to open the automatic valve 24 is sent to the automatic valve 24 drive unit. Since the input is received, the automatic valve 24 remains open.

By this operation, the liquid level in the secondary main circulation pump decreases, and when it reaches the standard, the liquid level in the secondary main circulation pump 21A, 21
A liquid level reference signal is output from B and 21C, and 20ut o
The signal is input to the memory deletion circuit 41 via the f3 circuit 38' and the 0 circuit 39'. As a result, the signal for opening the automatic valve 24 is removed, and a signal is output from the NOT circuit 42 to close the automatic valve 24.

At this time, the automatic valve 28 is in the closed state (the liquid level bulk signal is not output), but the liquid level reference signal is manually input to the memory removal circuit 41 in the control circuit on the automatic valve 28 side, and the automatic valve 28 is closed. 2
A closing signal of 8 is output from the NOT circuit 42.

In addition, for the automatic valves 24 and 28, the memory removal circuit 41 includes the steam generator inner cylinder internal space liquid level detectors 34A and 34.
B, liquid level bulk signal from 34C ■43 and liquid level low/low 0
The liquid level reference signal 045 output after 46 is the OR circuit 39.
It is also closed by being input via ′.

As a plant, in addition to the state transitions explained above,
There are changes in coolant temperature due to load fluctuations, etc., or rapid coolant temperature drops after a reactor trip, but these cases can also be handled by the embodiments of the present invention. Temperature change is at most 20
0C/h, the gas volume is at most 20m3°. Therefore, even if we consider the cover gas pressure in the steam generator to be 10Kg/da, the required gas exhaust/supply speed is much smaller than 1100N'/h, and the gas piping has a small diameter. can be fully dealt with.

According to the first embodiment of the present invention, there are the following effects.

■ Reduction in amount of material A gas space is provided inside the inner cylinder 13 of the steam generator 3 of the secondary main cooling system, and expansion and contraction of the coolant is absorbed by changes in the liquid level in this gas space. Compared to the main cooling system, the expansion tank 2, secondary overflow system and its auxiliary equipment can be reduced. (Additional equipment required for reduction is small.) ■ Rationalization of space and building The installation space for the large expansion tank 2 and the secondary overflow system, which were required for the conventional secondary main cooling system, can be significantly rationalized. As a result, the size of the building can also be reduced.

■ Reduction of empty loads and preheating and insulation equipment Expansion tank 2. By eliminating the secondary overflow system, the surface area of liquid metal equipment and piping in contact with the atmosphere is significantly reduced. Along with this, the load on air conditioning, preheating insulation membrane,
Kiyoshi's construction scope will be significantly reduced.

■ Reduction of sodium inventory By converting the space 13 inside the steam generator, which was conventionally filled with sodium, into a gas space and eliminating the expansion tank 2, the sodium inventory can be significantly reduced. Along with this, the secondary sodium filling and draining equipment can be significantly streamlined.

■ Reduction of sodium fire countermeasures By removing the expansion tank 2 and secondary overflow system, the scope of sodium fire countermeasures can be reduced. Along with this, safety and reliability are improved, and
It also becomes possible to reduce the need for countermeasure equipment.

Although the embodiment of the present invention has been described using ON-OFF control of the exhaust/supply valve, it is not necessary to limit the control to ON-OFF control as long as the liquid level can be obtained within a certain width within the pump.

[Brief explanation of the drawing]

Figure 1 is a schematic configuration diagram of the steam generator of the present invention, Figure 2 is a diagram showing the secondary main cooling system (expansion tank installed type) of a conventional liquid metal cooled fast reactor, and Figure 3 is the same as Figure 2. A diagram showing a similar cooling system (overflow system installed type), Figure 4 is a schematic configuration diagram of a conventional steam generator, and Figure 5 is the liquid level of a secondary main cooling ring pump using the steam generator of the present invention. FIG. 8 is a diagram showing the control range, FIG. 8 is a diagram showing the opening/closing state of the automatic valve, and FIG. 9 is a diagram showing the logic circuit of the control device. 1... Secondary main circulation pump, 2... Expansion tank, 3...
...Steam generator, 4...Main intermediate heat exchanger, 5...Over 70-system pumping electromagnetic pump, 6...Overflow system overflow tank, 10...Secondary argon gas equipment%11. ...Steam generator inlet nozzle stand, 12...Steam generator heat transfer tube group, 13...Steam generator inner cylinder, 14...Steam generator shroud, 15...Steam generator outlet nozzle stand,
16... Steam generator ring header (inlet), 17...
・Steam generator ring header (outlet), 18...Steam generator pressure control system, 19...Liquid level in the internal chamber when inside the steam generator, 20...Secondary main circulation pump liquid level, 21.・・２
Next main circulation pump internal liquid level detector, 22...control device, 2
3... pressure reduction line, 24... pressure reduction line automatic valve, 2
5...Reduction line vapor trap, 26...Exhaust header, 27...Reduction line bypass, 28...Reduction line bypass automatic valve, 29...Pressure line, 30.
... Pressurization line automatic valve, 31 ... Argon gas supply system, 32 ... Pressure line bypass, 33 ... Pressure line bypass automatic valve, 34 ... Steam generator inner cylinder internal space liquid level Detector, 35...Argon gas supply header, 36
...Automatic valve closed state, 37...Automatic valve open state, 38.
...2 out of 3 circuits, 39...OR circuits,
40... Memory circuit, 41... Memory removal circuit, 42.
...NOT circuit, 43...Steam generator internal inner cylinder space liquid level bulk signal, 44...Steam generator internal inner cylinder space liquid level high or lower signal, 45...Steam generator internal inner cylinder space liquid 46...Steam generator internal cylinder space liquid level low/low signal.

Claims (1)

[Claims] 1. In a steam generator for a fast breeder reactor that has a liquid level in a part separated from the heat transfer part, volume fluctuations due to expansion and contraction of the coolant can be absorbed by the liquid level part separated from the heat transfer part. 1. A steam generator characterized by being provided with means for absorbing water by varying it. 2. In the steam generator according to claim 1,
The volume fluctuation absorbing means includes a pressurizing line and a depressurizing line for controlling the heat transfer section and the separated liquid surface section of the steam generator, a stop valve attached to each line, and a secondary main circulation pump. A detector that detects fluctuations in the coolant liquid level in the tank and outputs a signal, and a control device that receives this signal and opens/closes and adjusts the opening of the pressurization line stop valve and the pressure reduction line stop valve. steam generator.