JPS5928803B2 - Nuclear plant steam temperature control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for controlling the vapor temperature of an atomic couplant, in particular the vapor temperature at the evaporator outlet.

A control system for normal load (30% to 100%) operation in nuclear couplers, for example, fast breeder reactor plants, has already been extensively studied and a certain method has been developed, but for start-up and shutdown (0% to 30%) As for load), this has not been done yet, and no active control has been applied.

The reason for this is that if there is a large change in steam pressure, such as during startup or shutdown, that change will have a great effect on the boiling situation, leading to unfavorable results.

For example, at startup, it is necessary to convert the steam at the evaporator outlet into superheated steam as soon as possible in order to shorten the startup time.

To do this, the pressure is initially kept low, then the saturation temperature of the fluid to be heated is lowered and the temperature difference between it and the secondary sodium is increased, thereby increasing the heat input and gradually increasing the pressure to the rated pressure. However, the current situation is that sufficient effects cannot be obtained due to the following problems.

Now, when the pressure inside the evaporator increases (generally 60 to 170
The enthalpy of saturated water corresponding to the pressure (in the range of ATA) increases proportionally, and the steam that was initially in the saturated region at a certain enthalpy will cool down due to the increase in pressure, and in extreme cases it will return to the subcooled region again. This phenomenon occurs, causing problems such as corrosion and thermal cycle fatigue failure in piping, superheaters, turbines, etc. after the evaporator outlet.

Furthermore, when the steam pressure is reduced when the steam generator is stopped, the amount of steam generated and the steam temperature increase, causing the same problems as when the steam generator is started.

The present invention has been made in order to efficiently and quickly start and stop a plant without causing the above-mentioned expected problems.

That is, the present invention provides an atomic coupler having a heat medium circulation system passing through an evaporator and a circulation pump, and a vapor circulation system passing through the evaporator corresponding to the heat medium circulation system, in which a controller is attached to the circulation pump. a flow rate signal generator that communicates with the controller via an adder, and a pressure setting device of a steam pressure control device provided in the steam circulation system communicates with the adder via a regulator; A flow rate signal generator generates a desired flow rate reference signal, and the flow rate reference signal is applied to the circulation pump to adjust the flow rate of the heat medium circulation system and control the steam temperature at the evaporative type outlet of the steam circulation system; According to the present invention, there is provided a device that adds a pressure set value of a pressure setting device to the flow rate reference signal via a regulator and controls steam temperature to a desired value in response to changes in steam pressure. For example, by pre-caulking and adjusting the heat medium flow rate before the steam pressure in the steam circulation system increases or decreases, the amount of heat carried into the evaporator can be increased or decreased in advance to respond to pressure changes in the steam circulation system, resulting in a time delay in the steam temperature. Therefore, the plant can be started and stopped efficiently and quickly without causing any problems to piping, turbines, etc.

Next, embodiments of the present invention will be described based on the drawings.

FIG. 1 is a system diagram of a fast breeder reactor plant whose steam pressure is controlled by the control device of this embodiment.

In Fig. 1, 1 is the core of a nuclear reactor, and this core 1 includes:
A control rod 3 with a control rod drive 2 is inserted.

A circulation system 4 of the heat medium, that is, liquid sodium, flowing through the reactor core 1 passes through an intermediate heat exchanger 5 and a primary circulation pump 6.

The circulatory system 4 is usually called the primary Na loop 4.

A secondary circulation system, that is, a secondary Na loop 7 for the heat medium, that is, liquid sodium, which passes through the intermediate heat exchanger 5 in correspondence with the primary Na loop 4, passes through the superheater 8 and the reheater 9 separately. After merging, the heat is returned to the intermediate heat exchanger 5 through the evaporator 10 and the secondary circulation pump 11 in sequence.

Note that the secondary Na loop 7 is provided with a distribution valve 12 on the upstream side of the reheater 9.

It exits the feed water pump 13 and passes through the feed water control valve 14, and is connected to a steam generator 10 and a superheater 8 corresponding to the secondary Na loop 7.
, and further passes through the speed regulating valve 15 to the high pressure turbine 16.
A steam circulation system 17 is provided in which the steam exits the high-pressure turbine 16, passes through the reheater 9, reaches the low-pressure turbine, and then returns to the feedwater pump 13.

FIG. 2 shows the system of the control device of this embodiment. In FIG. 20, said comparator 19 is connected to a proportional-integral action regulator 21, which form a compensation circuit.

A flow rate signal generator 22 provided for a central command device (not shown) is a controller provided in the secondary circulation pump 6 and has a function generation function, that is, a rotation speed regulator 23 and an adder 2
Electrical communication via 5.26.

The adder 26 is in electrical communication with the proportional-integral operation regulator 21 of the compensation circuit.

A pressure detector "27 provided in the steam circulation system 17 in relation to the speed regulating valve 15 is connected to a pressure setting device 29 via a comparator 28.
The comparator 28 is in electrical communication with the regulating valves 15 via a proportional-integral operation regulator 30,
, pressure detector 27, comparator 28, proportional-integral operation regulator 3
0 and the pressure setting device 29 are integrated into the steam circulation system 17.
A steam pressure control device 31 is formed.

The pressure setting device 29 of the steam pressure control device 31 is connected to the adder 25 via a regulator, that is, a proportional differential operation regulator 32.
electrically connected to.

To explain the normal operation of the embodiment with the above configuration, the nuclear reaction heat generated in the reactor core 1 is transferred to the liquid sodium flowing through the primary Na loop 4, and the liquid sodium receives heat and rises in temperature.The liquid sodium then passes through the intermediate heat exchanger 5. Here, it transfers heat to the liquid sodium flowing through the secondary Na loop 7, which itself is reduced in temperature to a low temperature, passes through the primary circulation pump 6, returns to the core 1, and repeats this cycle during operation.

As mentioned above, heat was received in the intermediate heat exchanger 5 and the temperature became high.
Next, the liquid sodium in the Na loop 7 flows through a superheater 8 and a reheater 9 to transfer heat to the steam in the vapor circulation system 17, and further enters the evaporator 10, flows through the vapor circulation system 17, and then passes through the evaporator 10.
It transfers heat to the incoming feed water, so that said feed water boils and evaporates into steam.

The liquid sodium that has exited the evaporator 10 is sent to the secondary circulation pump 11
, and returns to the intermediate heat exchanger 5, and during operation, the above-described cycle is repeated to circulate through the secondary Na loop 7.

Further, as mentioned above, in the steam circulation system 1γ, water flows in some parts and steam flows in some parts.

Next, the steam temperature control operation according to this embodiment having the above-mentioned configuration will be explained by taking the startup time as an example.

Normally, before starting the turbine, the pressure in the steam circulation system 17 is
Since the pressure has been increased to approximately 60 ata using an appropriate method, the pressure must be increased from 60 ata to 120 ata when the plant is started up.
The case where the voltage is increased to ATA will be explained.

Note that the reactor core 1 is controlled by a normal control device (not shown) to generate a predetermined thermal output.

A central controller (not shown) causes the flow rate signal generator 22 to generate a flow rate reference signal as shown by curve F in FIG.

In other words, from time T(0) to T(3), F(0) to F
As shown in (3), it increases uniformly from time T(3) to T(
Until 6), it is constant as shown in F(3) to F(6), and increases uniformly from F(6) after time T(6).

It goes without saying that the pattern of this flow rate reference signal can be set in various ways taking into consideration the characteristics of the plant and the like.

As mentioned above, the set pressure of the pressure setting device 29 of the steam pressure control device 31 changes from A(0) to A(4) from time T(0) to T(4) as shown by curve A in FIG. As shown, constant (
60ata), and from time T(4) to T(5), A(
As shown in 4) to A(5), it rises uniformly, and at time T(6)
Thereafter, it is held at 120ata (120ata) as shown in A(6) and after.

Therefore, from time T(0) to T(3), the output of the proportional differential operation regulator 32 based on the set pressure is B of the song MB.
Since it is zero as shown in (0) to B(3), the input to the rotation speed regulator 23 increases uniformly in response to only the flow rate reference signal F, and is converted as appropriate to increase the rotation speed of the secondary circulation pump 11. The flow rate of the secondary Na loop 7 is increased from D(0) to D(3) along the curve.

When the flow rate of liquid sodium in the secondary Na loop 7 increases, the heat transfer coefficient in the intermediate heat exchanger 5 increases, the temperature of the liquid sodium in the secondary Na loop 7 increases, and eventually the evaporator 1
The amount of heat carried into the evaporator 10 increases, and the amount of heat transferred to the feed water flowing through the steam circulation system 17 into the evaporator 10 increases.

Therefore, the outlet temperature of the evaporator 10 of the steam circulation system 17 is curve E
As shown, the temperature rises from the initial temperature E(0) to the saturation temperature E(1) at 60ata.

Since the pressure is kept constant, the outlet temperature of the evaporator 10 of the steam circulation system 17 does not rise to E(2) until the steam changes to saturated steam.

Furthermore, the liquid sodium in the secondary Na loop 7 is transferred to the evaporator 10.
Since the amount of heat carried into is increasing, the outlet temperature is E(
2) to E(3), and the steam becomes superheated steam.

After time T(3), the reference flow rate signal (F) changes from F(3) to
After becoming constant as shown in F(6), the outlet temperature of the evaporator 10 also becomes constant as shown in E(3) to E(4), and furthermore, at time T(4), the set pressure (A) becomes A( 4) starts to rise toward A(5), the output (B) of the proportional differential action regulator 32 first instantaneously increases from B(4--L) to B(4-U). , and then increases from B(4-U) to B(5-U) corresponding to A(4) to A(5).

The output (B) of the proportional differential operation regulator 32 described above is added to the reference flow rate signal F) from the adder 25, so it is a secondary N
Similarly, the flow rate (D) of the a-loop 7 changes from D(4) to D(5) by the operation of the rotation speed regulator 23 and the secondary circulation pump 11.
).

Due to the above-mentioned reason, the amount of heat introduced into the evaporator 10 by the secondary Na loop 7 increases, and the amount of heat that the feed water or steam flowing through the steam circulation system 17 receives in the evaporator 10 increases.

The increase in the amount of heat received by the steam circulation system 1T is determined by the steam pressure control device 3 based on the setting pressure hole of the pressure setting device 29.
Since this is carried out prior to and in parallel with the pressurization of the steam circulation system 17 carried out by 1, the evaporator outlet temperature (1) is maintained constant without falling.

After time T(5), the set pressure (A) is kept constant (120 ata) from A(5), but the output (B) of the proportional differential action regulator loses only the differential term and changes in pressure (△P
Only the proportional term proportional to (=120-60=60 ata) remains and is held at a constant value after B(5-L).

Therefore, the flow rate D) of the secondary Na loop 7 is also maintained at a value slightly larger than before the set pressure (A) increases.

The increase (△D) in this flow rate (D) is the pressure change (△P)
The outlet temperature of the evaporator 10 (the same) is kept constant because the change in enthalpy corresponds to the change in enthalpy.

In the above case, the steam temperature setting device 20 of the compensation circuit
The set temperature is set in advance as shown by curve E, and the steam temperature at the outlet of the evaporator 10 is detected by the temperature detector 18.
The steam temperature is compared with the set temperature, and if a deviation occurs, a compensation signal is output from the proportional-integral operation controller 21, thereby increasing or decreasing the flow rate of the secondary Na loop to control the steam temperature to match the set temperature. .

According to this embodiment having the configuration and operation described above, the steam temperature at the outlet of the evaporator 10 does not decrease compared to a control method that simply increases the steam pressure (the controlled outlet temperature of the evaporator 10 is curve E/). Since there is no piping for steam circulation system 17,
This has the effect that the plant can be started appropriately, efficiently, and quickly while preventing the occurrence of thermal cycle stress and corrosion in the superheater 9, high-pressure turbine 16, and the like.

Furthermore, prior to and in parallel with the rise in steam pressure, secondary N
Since it increases the flow rate of a-loose, it increases the furnace output after detecting a change in steam temperature, compared to simply installing a steam temperature compensation circuit that can be easily done by a person skilled in the art. It is possible to prevent a time delay until the amount of heat transfer is increased and to more reliably control the steam temperature at the evaporator outlet, thereby producing the above-described effects.

Those skilled in the art will easily understand that the control action and effect at the time of starting according to the present embodiment have been explained in detail above, but at the time of stopping, the control action and effect will correspond to this and work towards stopping.

Furthermore, although the present invention is very effective during startup and shutdown, it is of course possible to use it for steam temperature control during normal operation by making some changes in the configuration.

[Brief explanation of drawings]

FIG. 1 is a system diagram of an atomic couplant to which an embodiment of the present invention is applied, FIG. 2 is a system diagram showing an embodiment of the present invention, and FIG. 3 is an explanatory diagram of the operation. 1...Reactor core, 2...Control rod drive device,
4...Primary Na loop, 6...Primary circulation pump, 7...Secondary Na loop, 10...
...Evaporator, 15...Governing valve, 22...
...Flow rate signal generator, 23...Rotation speed regulator,
25.26... Adder, 27... Pressure detector, 28... Comparator, 29... Pressure setting device, 30...・Proportional-integral action regulator, 31
. . . Steam pressure control device, 32 . . . Proportional differential operation regulator.

Claims (1)

[Claims] 1. In an atomic couplant having a heat medium circulation system passing through an evaporator and a circulation pump, and a vapor circulation system passing through the evaporator corresponding to the heat medium circulation system, a controller is attached to the circulation pump, and the same A flow rate signal generator is provided in communication with the controller via an adder, and a pressure setting device of a steam pressure control device provided in the steam circulation system is communicated with the adder via a regulator. Atomic couplant steam temperature control device.