JPS5928802B2 - 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, first the pressure is kept low, the saturation temperature of the fluid to be heated is lowered, and the temperature difference with the secondary sodium is increased, thereby increasing the heat input and gradually increasing the pressure to the rated pressure. At present, sufficient effects cannot be obtained due to the following problems.

Now, when the pressure inside the evaporator increases (generally 60 to 17 Oa
The enthalpy of saturated water corresponding to the pressure (in the range of ta) increases proportionally, and the steam that was initially in the saturated region at a certain enthalpy will be cooled by the increase in pressure, and in extreme cases it will return to the subcooled region again. This phenomenon occurs,
This causes problems such as corrosion and thermal cycle fatigue failure in the piping, superheater, turbine, 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 enables the plant to be started efficiently and quickly without causing the above-mentioned expected problems.

This was done to stop it.

That is, the present invention provides a flow rate controller on the upstream side of the evaporator in a vapor circulation system that flows through the evaporator in correspondence with the heat medium circulation system, and a pressure setting device on the vapor circulation system on the downstream side of the evaporator. a steam pressure control device comprising: a feed water signal generator communicating with the flow rate controller via a subtractor; and an atomic couplant steam signal generator communicating with the pressure setting device via a regulator with the subtractor; Regarding the temperature control device, according to the present invention, when increasing or decreasing the pressure of the steam circulation system, a pressure setting signal from the pressure setting device of the steam pressure control device is added to the flow rate control system to adjust the water supply flow rate prior to the pressure change. Therefore, the steam pressure can be increased or decreased while maintaining the steam temperature at a predetermined value, and the plant can be started and stopped efficiently and quickly.

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 lid generator 10 and the secondary circulation pump 11 in sequence.

It exits the feed water pump 12, passes through the feed water control valve 13, passes through the evaporator 10 and superheater 8 in sequence corresponding to the secondary Na loop 7, further passes through the speed regulating valve 14, reaches the high pressure turbine 15, and the high pressure A steam circulation system 16 is provided which exits the turbine 15, passes through the reheater 9, reaches the low pressure turbine, and then returns to the feed water pump 13'.

FIG. 2 shows the system of the control device of this embodiment. In FIG. The comparator 18 communicates with the adder 21 via the proportional-integral operation regulator 20, and the temperature detector 17, the comparator 18, the evaporator outlet temperature setter 19, the proportional-integral operation Regulator 20 and adder 21 form a so-called compensation circuit.

A water supply signal generator 22, which is provided with respect to a central control unit (not shown), is electrically connected via a subtractor 23 and an adder 21 to a controller or rotational speed regulator 24, said rotational speed regulator 24 It is attached to the pump 12.

A pressure detector 25 provided in the steam circulation system 16 with respect to the regulating valve 14 is electrically connected to a proportional-integral operation regulator 27 and a pressure setting device 28 via a comparator 26, and The regulator 27 is in communication with the speed regulating valve 14 .

The regulating valve 14, the pressure detector 25, the comparator 26, the proportional-integral operation regulator 27, and the pressure setting device 28 together form a steam pressure control device 29, and the pressure setting device 28 is a regulator, that is, a proportional It is electrically connected to the subtractor 23 via a differential operation regulator 30.

First, to explain the normal operation of the plant (Fig. 1) to which this embodiment of the above-described configuration is applied, the nuclear reaction heat generated in the reactor core 1 is transferred to the liquid sodium flowing through the primary Na loop 4, which receives heat and rises. The warmed liquid sodium flows into the intermediate heat exchanger 5, where it transfers heat to the liquid sodium flowing through the secondary Na loop 7, and the temperature of the liquid sodium itself decreases to 1.
It passes through the next circulation pump 6 and returns to the core 1, and this cycle is repeated 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 steam circulation system 16, and further enters the evaporator 10, flows through the steam circulation system 16, and enters the feed water into the evaporator 10. Therefore, the 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 described above, in the steam circulation system 16, water flows in some parts and steam flows in some parts.

Next, the operation of this embodiment having the above-mentioned configuration will be explained by taking the startup time as an example.

The control rod 1 drive device 2 is controlled by receiving a command from a normal control device (not shown), and the reactor core 1 generates a required thermal output.

The primary circulation pump 6 and the secondary circulation pump operate appropriately to circulate liquid sodium in an amount corresponding to the thermal output of the reactor core 1 to the primary Na loop 4 and the secondary Na loop 7, respectively.

On the other hand, the water supply pump 12 receives a reference water supply signal from the water supply signal generator 22 and is controlled to rotate, and supplies predetermined water to the evaporator 10.
Steam (or water) that is supplied to the steam circulation system 16 and does not reach specified characteristics is discharged to the outside through a discharge system (not shown) provided in the steam circulation system 16.

Since the initial pressure of the steam circulation system 16 is raised to a predetermined pressure (for example, about 60 ata) in advance by a normal method, the steam pressure control device 29 controls the steam pressure from the initial pressure to a predetermined value exceeding the turbine input pressure. The pressure in the circulation system 16 is gradually increased with a uniform gradient.

This changing set pressure is output from the pressure setting device 28 as a function of time, and is compared with the pressure detected by the pressure detector 25 by the comparator 26, and a pressure deviation is output.

The pressure deviation is input to the proportional-integral operation regulator 27 and processed, and the valve opening of the speed regulating valve 14 is adjusted by the output thereof, and the pressure of the steam circulation system 16 is increased in accordance with the set pressure.

Simultaneously with the action of the steam pressure control device 29, the set pressure is sent to the proportional differential operation regulator 30, where an output signal of the sum of the term proportional to the pressure gradient and the term proportional to the pressure change, that is, a feedforward signal is generated. generated subtracter 23
Enter.

The feedforward signal has a negative effect on the reference signal, and the input from the subtractor 23 to the rotation speed regulator 24 is reduced by the amount of the feedforward signal, so that the rotation speed of the water pump 12 is reduced and the evaporator 10 The amount of water supplied to the evaporator 10 decreases, and therefore the amount of heat received per unit flow rate in the evaporator 10 increases.

Although a change in the boiling region occurs in the evaporator 10 due to the pressure increase caused by the action of the steam pressure control device 29, the flow rate of feed water is reduced in advance and during the pressure increase action by the action of the proportional differential operation regulator 30, so that steam circulation is prevented. The outlet temperature of the evaporator 10 of the system 16 is maintained at a predetermined value.

The compensation circuit including the temperature detector 17 etc. adds a compensation signal to the adder 21 by the action of the evaporator outlet temperature setter 19 which outputs the set temperature of the predetermined value, and complements the action by the feedforward signal described above. .

Although the above-mentioned set pressure is a rising pressure with a uniform gradient, it is of course possible to use other patterns, such as a variable pressure that rises stepwise, and the reference water supply signal does not need to be held constant but may be set gradually. It is also conceivable to increase it to

As mentioned above, according to this embodiment, the steam pressure control device 29
By proportionally differentiating the set pressure of the pressure setting device 28, the water supply flow rate is reduced prior to and in parallel with the pressure increase in the steam circulation system 16, thereby preventing a temperature drop due to pressure increase, and thus preventing the piping of the steam circulation system 16 from overheating. The plant can be started efficiently and quickly without causing excessive thermal stress, corrosion, etc. to the vessel 9, turbine, etc.

The control action of the evaporator outlet temperature at the time of startup according to this embodiment has been described in detail above, but at the time of shutdown, the pressure setting device 28
Those skilled in the art will readily understand that using a uniformly decreasing pressure as the set pressure will achieve the desired objective.

[Brief explanation of drawings]

FIG. 1 is a system diagram of a plant to which an embodiment of the present invention is applied, and FIG. 2 is a system diagram showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Core, 7... Secondary Na loop, 10... Evaporator, 12... Water supply pump, 14... Governor valve, 16
... Steam circulation system, 21 ... Adder, 22 ... Water supply signal generator, 23 ... Subtractor, 24 ... Rotation speed regulator, 25 ... Pressure detector, 26 ...・Comparator, 27・
...Proportional-integral action regulator, 28...Pressure setting device, 29
... Steam pressure control device, 30 ... Proportional differential operation regulator.

Claims (1)

[Claims] 1 A flow rate controller is provided upstream of the evaporator in a steam circulation system that flows through the evaporator in correspondence with the heat medium circulation system, and a steam pressure control device is provided in the steam circulation system downstream of the evaporator, including a pressure setting device. An atomic coupler comprising a control device, a water supply signal generator communicating with the flow rate controller via a subtracter, and communicating the pressure setting device with the subtractor via a regulator. Steam temperature control device.