JPS61275505A - Regulation valve warming control and device thereof - Google Patents

Abstract

PURPOSE:To enable stabilized control, when a housing of a regulation valve vapor chamber is warmed by a specified temperature rise by regulating valve opening of a regulation valve warming valve, by controlling the warming valve according to temperature comparison results between main vapor and inner surface of the housing. CONSTITUTION:When controlling warming, a computer 20 performs subtraction between output signal S1 from a temperature sensor 15 for detecting temperature of an inner surface metal of a regulation valve vapor chamber 6a and output signal S3 from a main vapor temperature sensor 12 to obtain a temperature difference DELTAT1 and determines if the DELTAT1 is between lower temperature limit -epsilon2 and upper temperature limit epsilon1 representing warming finish. When DELTAT1<-epsilon2, regulation valve warming valve is made to fully close and when -epsilon2<DELTAT1<epsilon1, the warming valve is made to fully open. And when DELTAT1>epsilon1, namely when the main vapor temperature is excessively higher than that of the said inner surface, opening and closing of the warming valve 5 is controlled so that a pressure difference between a vapor chamber target pressure calculated from the said inner surface temperature and an actual pressure falls within an allowable range.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention is directed to a nuclear power plant in which a control valve that adjusts the flow rate of main steam to the main turbine is installed at the time of boosting the pressure of the reactor, particularly during the step of boosting the pressure of the reactor and starting the turbine. The present invention relates to a control valve warming control method and apparatus that performs warming until just before the warming.

[Technical background of the invention and its problems]

Generally, in a nuclear power plant, in order to improve safety and operability, the entire plant is operated in a related manner by a plant automatic control system using a process computer system.

The range of automatic control of the plant by this automatic plant control system is from the time of reactor startup, mid-term turbine startup, merging, feedwater pump switching, plant startup with increased output, constant plant operation, output reduction, feedwater pump switching, disconnection. , covers all aspects up to the shutdown of the nuclear reactor and plant shutdown.

Conventionally, devices such as those shown in FIGS. 5 to 8 have been used to perform warming control of the regulator valve from the reactor pressurization process to just before turbine startup.

FIG. 5 shows the plant system of the part involved in regulating valve warming.

In the figure, steam generated by nuclear heating in a reactor pressure vessel 1 is sent to a main turbine 3 through a main steam line 2, and is used to rotate the main turbine 3. The main steam line 2 is provided with a main steam isolation valve 4, a regulating valve warming valve 5, and a regulating valve 6 in order from the upstream side to adjust the amount of main steam flowing into the main turbine 3. Further, the steam supplied to rotate the main turbine 3 is cooled and condensed in a condenser 7. Further, a drain line 8.9 is provided which leads the drain to the condenser 7 from the upstream side of each of the regulating valve warming valve 5 and the regulating valve 6.
Each drain line 8.9 is provided with a warming valve seat front drain valve 8a and a regulating valve front drain valve 9a.

In FIG. 6, only the parts that operate related to warming the control valve 6 are exaggerated. That is, during this warming, the control valve 6 is fully open, the control valve seat front drain valve 9a is fully open, and the main steam isolation valve 4 is fully open.

In FIG. 6, reference numeral 6a indicates a steam chamber of the control valve 6.

The main steam from the reactor pressure vessel 1 passes through the main steam line 2 and has its flow rate controlled by a warming valve 5.
It flows into the steam chamber 6a, and flows out to the condenser 7 through the drain line 9, which is the only outlet path since the regulating valve 6 is fully open.

When actually warming the regulating valve 6, the valve opening degree of the regulating valve warming valve 5 is controlled, and the amount of main steam flowing into the steam chamber 6a is adjusted to form the steam chamber 6a. The temperature of the housing 6b is raised to a predetermined temperature at a predetermined temperature increase rate.

The main steam used to raise the temperature of the casing 6b of the steam chamber 6a is kept at a constant pressure of about 40a* in the room by the vacuum pump 10.
It is sucked into the condenser 7 held before and after the Hgabs.

In order to perform this warming well, the reactor pressure sensor 11 measures the pressure in the reactor pressure vessel 1 and the temperature of the main steam in the main steam line 2 as instrumentation equipment that monitors and measures the predetermined amount of each part. Main steam temperature sensor 12 to measure
, a control valve steam chamber pressure sensor 13 that measures the pressure inside the steam chamber 6a of the control valve 6, a control valve steam chamber outer surface metal temperature sensor 14 that measures the metal temperature of the casing 6b of the steam chamber 6a from inside and outside, and a control valve steam An indoor metal temperature sensor 15 is provided.

However, when the operator manually warms the control valve 6, the inner surface temperature of the housing 6b, which is displayed by the control valve steam chamber inner metal temperature sensor 15, is monitored every 15 minutes based on the operator's experience. However, it is necessary to open and close the warming valve 5 appropriately, which places a very heavy burden on the operator.

Therefore, conventionally, as shown in FIGS. 7 and 8, the regulating valve 6 is warmed by an automatic control system using a process computer.

In other words, as shown in FIG. A predetermined driving amount of the regulating valve warming valve 5 is determined and an opening signal S is output as a signal S2 from the regulating valve warming valve opening setting device 18 to drive the regulating valve warming valve 5 to open and close.

This control program 17 determines the drive amount of the regulating valve warming valve 5 according to the flowchart shown in FIG. In other words, the inner metal temperature sensor 1 of the control valve steam chamber
From the signal S1 sent from 5, the casing 6 of the steam chamber 6a
Calculate the rate of change in the internal temperature of b itself using a method such as the least squares method, and if the rate of change is 80°C/H or more, generate a signal S2 for closing drive (-α%) and increase the temperature to 60°C/H. If it is below, generate the same drive (-α%) signal S2,
If the temperature is greater than or equal to 60° C./H and less than or equal to 80° C./H, a signal S2 for maintaining the current driving amount (0%) is generated.

However, when automatically controlling the warming of the regulator valve 6 using this conventional method, there are the following two problems.

The first problem is that the calculated rate of change in the internal temperature of the casing 6b of the steam chamber 6a itself varies.

This sampling of the rate of change of the internal temperature of the housing 6b itself is calculated as follows: 1
The current limit is about 6 points in the past at 5 second intervals. However, due to the characteristics of the thermocouple that serves as the temperature sensor, errors such as fluctuations occur in the signal S1, making it extremely difficult to adjust the rate of change within a reasonable range, resulting in variations in the rate of change. Ta.

Second, the rate of increase, or rate of change, of the internal temperature of the casing 6b of the steam chamber 6a itself varies depending on the state of the pressure inside the reactor pressure vessel 1, so the control valve Opening/closing the warming valve 5, IJIII
L..., there is a possibility that proper warming cannot be performed.

FIG. 9 shows the time course of the warming of the regulator valve 6 during a normal reactor pressurization process. In a nuclear reactor, operating the control rods in a degassed state heats the core and generates steam.
The steam is saturated, and the rise in reactor pressure and reactor water temperature show almost the same trend. Therefore, in a normal pressure increasing process, the main steam temperature t1 gradually increases as the furnace pressure increases. The rate of increase in the main steam temperature t1 is limited to a maximum of 55° C./H in the case of a boiling water reactor.

A normal control valve A-ming operation is performed by gradually opening the control valve A-ming valve 5. Its operating range starts from the current furnace pressure of 7 K'l/crA and main steam temperature of about 160°C. In this case, the steam chamber 6a
The internal temperature t2 of the casing 6b itself was determined by the fact that the rate of increase in the main steam temperature was approximately 30° C./H. Therefore, it does not change suddenly and increases gradually. Furthermore, the external surface temperature t3 of the housing 6b itself has a similar rate of increase. Then, the valve opening degree 0 of the adjusting valve warming valve 5 is simultaneously driven by +0%, and the pressure P in the steam chamber 6a is also gradually increased.

However, the warming of the regulator valve 6 in a nuclear coupler is not limited to the above-mentioned normal pattern, but also when the warming operation is started after the reactor pressure reaches the rated pressure, or when the reactor reaches the rated pressure and then goes subcritical once. In some cases, warming operations may be started after inspecting the inside of the reactor containment vessel. In these cases, since the furnace pressure conditions for starting warming are different from those in the normal pattern, the inner temperature t2 of the bell body 6b of the steam chamber 6a fluctuates violently.

This will be further explained with reference to FIG. 10, which shows the time course of the warming of the regulator valve 6 when the reactor is at rated pressure. When the reactor is at rated pressure, the main steam temperature is also constant at around 280°C. After the opening degree 0 of the adjusting valve warming valve 5 exceeds the opening temperature of 40%, when the adjusting valve warming valve 5 is driven to open by α%, the pressure P in the steam chamber 6a becomes the furnace pressure of 65 kg/ cII, suddenly, e.g. 10Kg/c
It also increases around i. At this time, the inner surface temperature t of the housing 6b
2 rises with a time delay of 1 to 2 minutes, and rises by more than 20°C, resulting in a rate of change that easily exceeds 80°C/H. When this rate of change is measured and the warming valve 5 is immediately driven to close by 1 α%, the pressure P in the steam chamber 6a drops rapidly from about 10 Kl/tyl to 20 K9/cd, and at the same time the inner temperature of the housing 6b decreases. The rate of change at t2 is also 60
A phenomenon occurs in which the temperature drops below ℃/H. Therefore, the housing 6b
The inner surface temperature t2 repeats an uncontrolled hunting phenomenon and becomes extremely unstable.

On the other hand, it is conceivable to shorten the sampling interval of the rate of change of the internal temperature [ft2] of the housing 6b, but conversely, the internal temperature t
This method cannot be used because it would differentiate the steady fluctuations and noise of 2.

Therefore, the conventional method shown in FIGS. 7 and 8 cannot suitably adapt to all furnace pressure conditions, and also cannot stably control the rate of increase in the internal temperature of the casing 6b of the steam chamber 6a. I couldn't.

[Purpose of the invention]

The present invention has been made in consideration of these points,
It is an object of the present invention to provide a method and apparatus for warming a regulating valve that can stably perform warming control of a regulating valve in any state of the reactor pressure in a nuclear reactor in a nuclear reactor.

[Summary of the invention]

Control valve warming 1lII which is the first invention of the present invention
Method 11 is a regulating valve warming control method in which the valve opening degree of a regulating valve warming valve that controls the flow rate of main steam is adjusted to raise the temperature of the casing of the steam chamber of the regulating valve at a predetermined temperature increase rate, The temperature of the main steam supplied to the chamber and the inner surface temperature of the casing are measured and compared, and if the temperature of the main steam is higher than the inner surface temperature of the casing, the target temperature of the steam room calculated from the inner surface temperature is determined. The pressure is compared with the actual pressure in the steam chamber fed back, and the warming valve is adjusted so that the pressure difference is within an allowable range, and the temperature of the main steam is lower than the inner surface temperature of the housing. If the difference between the temperature of the main steam and the inner surface temperature of the casing is within a predetermined range, the warming valve is fully opened. .

A moderator valve warming control device, which is a second invention of the present invention, includes a moderator valve having a steam chamber into which main steam flows, and a moderator that controls the amount of main steam flowing into the steam chamber by adjusting the valve opening degree. A regulating valve warming & 13 control device having a regulating valve warming valve that raises the temperature of the casing of the steam chamber at a predetermined rate of temperature rise by a regulating valve steam chamber pressure sensor that measures the pressure of the steam chamber, and an inner surface of the casing. A metal temperature sensor on the inner surface of the control valve steam chamber is installed to measure the temperature, and a main steam temperature sensor is installed to measure the temperature of the main steam flowing into the steam chamber. The control valve warming valve is set to I? A process computer that controls closing, compares the main steam temperature with the inner surface temperature of the casing, and if the temperature of the main steam is too high than the inner surface temperature of the casing, the target pressure of the steam chamber calculated from the inner surface temperature. and the actual pressure in the steam chamber input as feedback, and open and close the adjusting valve warming valve so that the pressure difference is within an allowable range, and if the temperature of the main steam is lower than the inner surface temperature of the housing. A process computer is provided to fully open the moderation valve warming valve, and to fully open the moderation and subtraction warming valve when the difference between the temperature of the main steam and the internal humidity of the housing is within a predetermined range. Features.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 4.

FIG. 1 shows an embodiment of a regulating valve warming control device according to the second aspect of the present invention, in which the same parts as in the prior art are denoted by the same reference numerals.

FIG. 2 shows a 1iIJ all program for determining and outputting the driving amount of the regulating valve warming valve 5 according to the regulating valve warming control method which is the first invention of the present invention. It is attached.

The apparatus of the present invention has a process meter of $11 as shown in FIG.
120 is provided with a control program 21 for determining the driving amount of the regulating valve warming valve 5 according to the method of the present invention and outputting it to the regulating valve warming valve opening setting device 18. The control program 21 calculates and determines the driving amount using not only the inner surface temperature signal S1 of the casing 6b of the steam chamber 6a itself from the regulating valve steam chamber inner surface metal temperature sensor 15, but also the main steam temperature sensor. 2, the pressure signal S4 in the steam chamber 6a from the control valve steam chamber pressure sensor 3, and the outer surface temperature signal S5 of the casing 6b itself from the control valve steam chamber outer surface metal temperature sensor 4. It is configured to be input to the program 21. Furthermore, in the present invention, the pressure signal S4 of the steam chamber 6a is the main target of υ1111, the inner surface temperature signal S is used auxiliary, and the main steam temperature signal S3 and the outer surface temperature signal 85 are also monitored. It is characterized by what it does.

Next, the operation of the apparatus of the present invention will be explained with reference to the method of the present invention and the control program 21 shown in FIG. 2 showing its contents.

First, in step ST1, the casing 6 of the steam chamber 6a sent from the regulating valve steam chamber inner surface metal temperature sensor 5
The internal temperature signal S1 of b is sampled every 5 minutes and at the same time the main steam temperature is sensed.

Next, in step ST2, the temperature difference ΔT1 is determined. That is, it is determined as follows whether the temperature difference ΔT1 is between the lower limit temperature difference -ε2 indicating completion of warming of the control valve 6 and the upper limit temperature difference ε1. This ε, -8
The value of 2 is set in advance.

If this temperature difference ΔT is -82°C or less, that is, if the main steam temperature becomes lower than the inner surface temperature of the housing 6b,
In step ST7, the warming valve 5 is rapidly opened and fully opened, and the internal temperature of the housing 6b is maintained so as not to drop. In such a case, subcritical operation may be performed to inspect the inside of the reactor containment vessel after the reactor rated pressure has been reached.

Furthermore, if the temperature difference ΔT1 is in the range of −ε2 × ΔT, <81, then the warming of the control valve 6 has been completed;
In step ST7, the control valve warming valve 5 is rapidly opened and fully opened, and the subsequent opening of the control valve 6 is awaited.

Further, when the temperature difference ΔT is 81 or more, the inner surface temperature of the casing 6b is lower than the main steam temperature, so the opening/closing control of the regulating valve warming valve 5 is performed as shown in steps ST3 to ST7, and the inner surface temperature of the casing 6b is is increased at a temperature increase rate of 60°C/H.

That is, in step ST3, the can is calculated by adding 5° C. to the internal humidity of the housing 6b. The temperature of this calculation is 5
This is the target inner surface temperature of the housing 6b after minutes.

Next, in step ST4, the target temperature calculated in step ST3 is compared with the steam table stored in the memory section of the process computer 20 and converted into pressure, and the target temperature of the pressure in the steam chamber 6a after 5 minutes is shall be.

Next, in step ST5, a pressure signal S4 inputted from the control valve steam chamber pressure sensor 3 based on the calculated target pressure.
The pressure difference ΔP is calculated by subtracting the actual actual pressure in the steam chamber 6a shown by .

This pressure difference ΔP is calculated every 5 seconds.

Next, in step ST6, the pressure difference ΔP is determined. That is, it is determined whether the magnitude of the pressure difference ΔP with respect to the target pressure after 5 minutes requires opening and closing of the regulating valve warming valve 5 by comparing it with positive and negative limit values ±ε. ε
3 indicates the upper limit where the actual pressure can be higher than the target pressure, -
Reference numeral 83 indicates a lower limit at which the actual pressure may be lower than the target pressure, and these limit values ±ε3 are set in advance.

If this pressure difference ΔP is larger than ε3, the steam chamber 6a
Since the actual pressure inside is too high than the target pressure, step ST
At step 7, the warming valve 5 is driven to close by a minute amount of 1 α%.

If the pressure difference ΔP is smaller than -83, the actual pressure in the steam chamber 6a is too low than the target pressure, so the warming valve 5 is driven to close by a very small amount α% in step ST7.

In addition, when the pressure difference ΔP is 1ε3≦ΔP≦ε3, the actual pressure in the steam chamber 6a is within the allowable range compared to the target pressure, so the driving amount of the regulating valve warming valve 5 is determined in STEP ST7. is set to 0% to maintain the current valve opening.

Next, in step ST8, before outputting the drive output, the outer surface temperature signal S5 from the regulating valve steam chamber outer surface metal temperature sensor 4 and the regulating valve steam chamber inner surface metal temperature sensor 5 are detected.
The deviation temperature ΔT2 from the inner surface temperature signal S1 is calculated.

Next, in step 8T9, the calculated deviation temperature ΔT
is larger than the allowable range ε4, the control is stopped and an alarm is generated. On the other hand, if the deviation temperature 6 is smaller than the allowable range ε4, the drive amount determined by the stirrup ST7 is outputted to the adjusting valve warming valve opening setting device 18 as a signal S6.

As a result, the regulating valve warming valve opening setting device 18 controls the regulating valve warming valve 5 according to the signal S6, and a predetermined amount of main steam is fed into the steam chamber 6a of the regulating valve 6, and the warming valve be done.

Next, with reference to FIG. 3, a description will be given of the time history of various quantities during the time of the adjustment valve wa--tang according to the present embodiment.

This figure shows the warming of the regulator valve 6 during operation at a constant rated pressure of the nuclear reactor, which can be said to be the most severe condition, and the main steam temperature t1 is constant at around 280°C. The target pressure Po calculated from the inner surface temperature t2 of the casing 6b of the steam chamber 6a of the control valve 6 is updated every 5 minutes. The opening degree O of the adjusting valve warming valve 5 is adjusted every 5 seconds or so to control the steam chamber pressure P of the steam chamber 6a so as to reach the target pressure Po. Since the steam is saturated, the temperature rise is almost the same as the trend of the steam chamber pressure P, and the inner surface temperature t2 of the casing 6b of the steam chamber 6a can be stably raised at a temperature increase rate of 60° C./H. . In this case, since pressure is used for control, the time delay in temperature rise becomes irrelevant.

Next, the time history of various quantities when the regulating valve warming valve 5 is suddenly closed and opened will be explained with reference to FIG.

As the furnace pressure rises, the regulator valve 6 is warmed, and the main steam 8! When the main steam temperature t1 and the inner surface temperature t2 of the casing 6b of the steam chamber 6a become close to each other after the temperature t1 has risen to a certain extent, the valve opening degree of the warming valve 5 becomes 0.
is fully opened. 1 of the process computer 20 at the same time. II
Since the program processing by the III program 21 is also stopped, the load on the computer 20 is reduced. After that, the main steam temperature ti,
falls, and the temperature difference ΔT1 with the inner surface temperature t2 of the housing 6b
When becomes ΔT - ε2, the regulating valve warming valve 5 becomes fully open. This protects the metal temperature of the housing 6b of the regulating valve 6 from lowering. After that, the inspection work is completed and warming control is started again. In addition, 40%
The reason why the regulating valve warming valve 5 is opened all at once is because there is play in the opposite valve 5, and in reality steam enters the steam chamber 6a of the regulating valve 6 from 40%.

As described above, the warming control of the control valve 6 performed in this embodiment is performed by controlling the steam chamber 6a of the control valve 6, which follows minute opening/closing operations of the control valve warming valve 5 almost without any time delay.
The internal pressure is used as the main feedback amount,
By controlling the calculation loop based on this feedback using a direct digital control method (DDC method) such as a 5-second period, it is possible to prevent the pressure inside the steam chamber 6a of the control valve 6 from rising rapidly.

Furthermore, in a range where the temperature deviation ΔT2 between the inner and outer surfaces of the casing 6b of the steam chamber 6a becomes so large that the metal of the regulator valve 6 cannot be protected, the warming control is stopped and an alarm is output. This allows personnel to be notified of abnormalities, further improving reliability.

Further, the warming valve 5 can be opened and opened quickly. As a result, if the temperature of the main steam to be supplied falls below the inner surface temperature of the casing 6b of the steam room 6a during the pressure reduction process during inspection inside the reactor containment vessel, which is unique to nuclear power, the direct valve 5 is suddenly closed and the casing 6b is closed. It can protect your metal from lowering its temperature. In addition, the main steam temperature and the housing 6b
When the internal temperature of the DC υ 1111 approaches, the counter valve 5 is suddenly opened to indicate that warming has been completed, and the DCυ 1111 processing is stopped, thereby reducing the load on the computer.

As described above, according to this embodiment, the temperature of the housing of the steam chamber of the control valve can be stably raised regardless of the state of the reactor pressure, and safe and appropriate warming can be achieved. can be controlled.

Note that the warming control according to this embodiment can also be applied to warming control for warming turbine blades.

(Effects of the Invention) As described above, the present invention has the advantage that the regulating valve can be warmed stably under any condition of the reactor pressure.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the moderation valve warming control device of the present invention, FIG. 2 is a flowchart of a control program for carrying out the moderation valve warming control method of the present invention, and FIG. 3 is a block diagram showing an embodiment of the moderation valve warming control device of the present invention. Fig. 4 is a diagram similar to Fig. 3 when the warming valve is suddenly opened, and Fig. 5 is a system diagram of the plant involved in warming the control valve. Fig. 6 is an exaggerated view of only the parts that operate related to the adjustment valve warming, Fig. 7 is the same as the conventional figure 1, Fig. 8 is the same as the conventional figure 2,
FIG. 9 is a time history characteristic diagram of various quantities according to the conventional method in a normal reactor pressurization process, and FIG. 10 is a diagram similar to FIG. 9 when the reactor is at rated pressure. 5...Adjustment valve warming valve, 6...Adjustment valve, 6a
... Steam chamber, 6b... Housing, 12... Main steam temperature sensor, 13... Control valve steam chamber pressure sensor, 15...
- Adjustment valve steam chamber inner surface metal temperature sensor, 20... Process calculator, tl... Main steam temperature, t2... Inner surface temperature of the housing, Po... Target temperature, P... Pressure in the steam chamber. Applicant's agent Kiyoshi Inomata Figure 1 - 11 hours c) Figure 3'6'$4 Figure - 11111 (II) 1t' 5th
Figure 7 Figure 6Figure 7-m hour (minute) Figure 9

Claims (1)

[Claims] 1. Control valve warming control that adjusts the valve opening degree of the control valve warming valve that controls the main steam flow rate and raises the temperature of the casing of the control valve's steam chamber at a predetermined temperature increase rate. In the method, the temperature of the main steam fed to the steam chamber and the inner surface temperature of the casing are measured and compared, and if the temperature of the main steam is higher than the inner surface temperature of the casing, the temperature is calculated from the inner surface temperature. The calculated target pressure of the steam chamber is compared with the actual pressure of the steam chamber fed back, and the adjusting valve warming valve is opened and closed so that the pressure difference is within an allowable range, and the temperature of the main steam is adjusted. If the temperature is too low than the internal temperature of the housing, the warming valve is fully closed, and if the difference between the main steam temperature and the internal temperature of the housing is within a predetermined range, the warming valve is closed. A control valve warming control method characterized by fully opening the control valve. 2. A control valve having a steam chamber into which main steam flows, and controlling the amount of main steam flowing into the steam chamber by adjusting the opening degree of the valve to raise the temperature of the casing of the steam chamber at a predetermined rate of temperature rise. A moderation valve warming control device having a moderation valve warming valve that warms the temperature, comprising: a moderation valve steam chamber pressure sensor that measures the pressure in the steam chamber; a moderation valve steam chamber inner surface metal temperature sensor that measures the inner surface temperature of the casing; , and a main steam temperature sensor that measures the temperature of the main steam flowing into the steam chamber, and controls the opening and closing of the warming valve according to the relationship among the steam chamber pressure, the inner surface temperature of the housing, and the main steam temperature. The process calculator compares the main steam temperature and the inner surface temperature of the casing, and if the main steam temperature is too high than the inner surface temperature of the casing, the target pressure of the steam chamber calculated from the inner surface temperature is input as feedback. The temperature of the main steam is compared with the actual pressure in the steam chamber, and the warming valve is opened and closed so that the pressure difference is within the allowable range. The method is characterized by being provided with a process calculator that fully closes the valve warming valve and fully opens the moderation valve warming valve when the difference between the temperature of the main steam and the inner surface temperature of the casing is within a predetermined range. Adjustment valve warming control device.