JPS62182403A - Thermal stress monitoring method for turbine rotor - Google Patents

Abstract

PURPOSE:To perform life control over a rotor so accurately, by setting a rotor surface temperature in a reheating part from the measured value of an inner surface metal temperature in a high pressure first stage after-steam chest, and performing calibration by a reheat steam temperature at need. CONSTITUTION:A thermocouple 20 is installed in an internal casing 11 corresponding to a high pressure stage after-steam chest 18. Another thermocouple 28 is installed in an external casing 10 of a reheating part 13. On the basis of the measured value of the thermocouple 20, surface temperature distribution of a reheating part rotor is found. Calibration takes place according to the measured value of the thermocouple 28. With this constitution, in due consideration of the influence of leaked steam out of an intermediate gland part 30, thermal stress of the rotor can be monitored so that life control is accurately performable.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to thermal stress monitoring and techniques for a turbine rotor in a high- and intermediate-pressure integrated turbine, and particularly to a method for monitoring thermal stress of a turbine rotor for monitoring thermal stress in an intermediate-pressure turbine rotor. Regarding the method.

[Technical background of the invention and its problems]

A steam turbine rotor such as a high-intermediate pressure integrated steam turbine is exposed to high-temperature steam. For example, when starting a steam turbine, the heat transfer coefficient from the steam to the turbine rotor increases as the steam pressure temperature increases, and the surface metal of the turbine rotor increases. The temperature is at an upper bound. On the other hand, since the temperature inside the turbine rotor rises due to heat conduction from the rotor surface, the rotor interior tl! The temperature rises later than the rotor surface temperature. As a result, a large temperature difference occurs between the inner and outer surfaces of the turbine rotor, creating thermal stress.

Recently, commercial steam turbines used in nuclear power plants and thermal power plants have become larger due to the demand for larger capacity, and the rotor diameter of the turbine rotor has become larger. Therefore, as the temperature of the turbine rotor rises, the temperature difference increases, and the generated thermal stress also tends to increase. Furthermore, with the increase in base-load operation plants such as nuclear power plants, thermal power plants have become increasingly important as power plants for load adjustment in response to fluctuations in electricity demand. forced to drive. In order to ensure safe operation of these thermal power plants, thermal stress monitoring of turbine rotors exposed to high-temperature steam from steam turbines is becoming increasingly important.

The reality is that thermal stress in turbine rotors is measured using unit computers and separate thermal stress monitoring devices.

By the way, the places in a steam turbine where the thermal stress is the most severe are the places where the steam temperature changes greatly from turbine startup to full load operation, and in particular, the places in the high-pressure first stage and the first reheating stage of the steam turbine. It is known that severe thermal stress acts on the rotor surface at the root of the turbine impeller. For this reason, in steam turbines, thermal stress monitoring of the turbine rotors of the high-pressure first stage and the first stage of the reheating section is extremely important, and is listed as one of the turbine operation monitoring items.

Calculation of rotor thermal stress based on the temperature difference between the inside and outside surfaces of the turbine rotor can be derived if the temperature distribution inside the turbine rotor is known, since the shape of the turbine rotor can generally be approximated to an infinite cylinder. , for example, can be derived from the basic material mechanics equation described in "Unsteady Thermal Stress of Steam Turbine Rotor" in Journal of the Japan Society of Mechanical Engineers, Vol. 74, No. 627, Page 402, and is expressed by the following equation.

Here, σ: Tangent line J3 and axial stress on the turbine rotor surface σb: Tangent line and axial stress on the turbine rotor bore (center hole) surface β: Linear expansion coefficient C: Boisson's ratio E: Longitudinal elastic modulus ■ = Turbine rotor Surface temperature Tb: Turbine rotor bore surface temperature T: Turbine rotor volume average temperature (3) R: Turbine rotor outer radius R: Turbine rotor inner radius.

On the other hand, it is known that the temperature distribution inside the turbine rotor approximates a one-dimensional heat conduction problem only in the radial direction of the rotor (thick-walled cylinder), ignoring heat movement in the rotor axial direction. Various methods have been proposed to obtain the temperature distribution for heat conduction in the radial direction of the rotor, and among them, the calculation method using the difference method described in JP-A No. 54-28904 is relatively accurate. It is widely used as a method suitable for GW IN processing.

When calculating the temperature distribution using the finite difference method, care must be taken in setting the initial conditions and reading the change over time in the turbine rotor outer surface temperature. The initial conditions are set based on the fact that the maximum thermal stress occurs generally during the (p) half of the turbine startup process.
Assuming that the initial 111J value has a small effect on the maximum thermal stress and that the entire steam turbine is in a state of thermal equilibrium just before the turbine starts, it is possible to read the typical metal surface temperature of the steam turbine and maintain a uniform temperature distribution. That's enough.

However, after the steam turbine is started, it is practically impossible to directly measure the outer surface temperature of the rotationally driven turbine rotor. For this reason, the temperature of the inner metal of the turbine casing that is in contact with the same steam as the steam that contacts the outer surface of the turbine rotor is measured, and this temperature is used as the turbine rotor surface temperature or as a reference temperature for deriving the turbine rotor surface temperature. There are many things to do.

As such turbine casing inner metal temperature, the high pressure first stage steam riser inner metal temperature and the reheat steam chamber inner metal temperature of the reheating section are used, corresponding to the turbine rotor parts where the maximum thermal stress occurs. be done. The former measures the synergistic effect between main steam temperature changes and turbine speed characteristics, while the latter measures reheat steam temperature changes and interpolates each measured value with thermal stress in a monitoring device to determine the steam turbine's performance. The severity of transient changes can be monitored.

However, in high- and intermediate-pressure integrated steam turbines, the results of temperature measurement tests on the actual turbine rotor during operation indicate that leakage steam from the high-pressure section flows into the reheating section through the intermediate gland, causing reheating. The temperature change on the outer surface of the turbine rotor near the first stage of the hot section is not the turbine casing inner metal temperature measured with a thermocouple, that is, the reheat steam temperature change, but the temperature change on the outer surface of the turbine rotor near the first stage of the high pressure section. It is strongly affected by the steam temperature after the first stage.

Therefore, the temperature distribution of the turbine rotor of the high and intermediate pressure integrated steam turbine reheating section is as shown in FIG.
In the calculation method, the temperature distribution of the turbine rotor in the high-pressure section and the reheat section is determined by measuring the inner metal temperature of the post-stage inner surface and the inner metal temperature of the reheat steam chamber, and then the thermal stress of each turbine rotor is calculated. The thermal stress may be far different from the actual hot part horn value. However, until now, it has not been clear to what extent the influence of the high-pressure first-stage post-stage steam temperature that acts on the reheating section should be taken into account.

After that, a similar r measurement test using an actual turbine rotor was carried out, for example, in "Thermal and Nuclear Power Generation" magazine, Vol. 30, No. 3, No. 2.
“New starting method for steam turbines” described on page 35
Based on this, the influence of the steam temperature after the first stage for high pressure has been quantitatively evaluated. As a result, as shown in FIG. 8, it has become clear that the method of determining the thermal stress of the turbine rotor based on the reheated steam temperature cannot accurately monitor the thermal stress.

Therefore, if the thermal stress of the turbine rotor is determined by method 1 shown in FIG. In other words, a huge mistake was made in the life management of the turbine rotor, and unexpected repair work had to be performed within the life of the turbine rotor.

[Purpose of the invention]

This invention was made in consideration of the above-mentioned circumstances, and dramatically improves the accuracy of thermal stress monitoring of the turbine rotor of a high- and intermediate-pressure integrated turbine, and enables accurate long-term maintenance management and life management of the turbine rotor. It is an object of the present invention to provide a method for monitoring thermal stress of a turbine rotor.

[Summary of the invention]

A method for monitoring thermal stress of a turbine rotor according to the present invention includes a method for monitoring thermal stress of a high-intermediate pressure integrated turbine rotor housed in a turbine casing that includes a high-pressure section and a reheating section in the axial direction. In the method for detecting the inner metal temperature of the steam chamber after the first stage of the high pressure cylinder,
The surface temperature of the turbine rotor in the reheating section is set from the measured value of the inner metal knitting of the stage steam chamber, and the thermal stress of the turbine rotor is monitored for the influence of leakage steam flowing from the high pressure section to the reheating section via the intermediate gland section. It is characterized by the fact that it is incorporated into

[Embodiments of the invention]

Hereinafter, an embodiment of the method for monitoring thermal stress of a turbine rotor according to the present invention will be described with reference to the attached drawing F1.

FIG. 2 shows a high-intermediate pressure integrated steam turbine in which the method for monitoring thermal stress of a turbine rotor according to the present invention is implemented. Internal casing 11
A high-pressure section 12 and a reheating section 13 are formed to face each other in the axial direction in the internal casing 11, and a high-intermediate pressure integrated turbine rotor 14 is accommodated therein. Main steam from a boiler (not shown) is guided from a main steam pipe 15 protruding from the outer casing 1o to the nozzle box 16, trapping the inner casing 11. The high pressure first stage is transmitted from the nozzle formed in the nozzle box 16 and the high pressure first stage impeller 17.
The main steam guided into the nozzle box 16 is passed from the nozzle to the high pressure first stage impeller 17.
It is ejected towards. When the ejected main steam passes through the turbine impeller 17, it performs the work of imparting rotational force to the turbine impeller 17, drops by 'fiA degree, and enters the high pressure cylinder 1 installation steam chamber 18 (Fig. 3). You will be guided. This steam is sequentially guided from the first-stage steam chamber to the second-stage and subsequent turbine stages to perform similar work, and then exits from the casing 10.11 and is reheated in a reheater (not shown).

Furthermore, as shown in FIG. 3, the internal casing 11 corresponding to the high-pressure first-stage impeller chamber 18 is provided with a thermal lightning pair 20 as a temperature detector for measuring the inner metal temperature of the first-stage steam chamber. This thermal lightning pair 20 measures fA degree changes in the steam chamber after the first stage of the high-pressure cylinder.By this temperature detection, the high-pressure portion surfaces 21a, 21b of the turbine rotor 14,
The local maximum thermal stress occurring in areas such as 21c is monitored.

On the other hand, reheat steam heated in a reheater (not shown) is guided from a reheat steam pipe 23 protruding from the outer casing 10 to a reheat steam chamber 24, and then from this reheat steam chamber 24 to a reheat steam chamber 24. It is sent to the first stage turbine impeller 26 through the hot section first stage nozzle 25 and is applied to the first stage turbine impeller 26 . The reheat section first stage nozzle 25 and the first stage turbine impeller 26 constitute the first stage turbine stage of the reheat section, and the reheat steam that has done work in the first stage turbine impeller 26 is then reheated. It is sequentially guided to the turbine stages after the second stage of the hot section.

On the other hand, the temperature change of the reheating steam is detected by a thermal lightning pair 28 as a temperature detector installed in the outer casing 10, and the temperature of the inner surface metal of the reheating steam chamber 24 is detected by this thermal lightning pair 28. There is.

By the way, in the actual turbine rotor 14 of the high-intermediate pressure integrated turbine, leaked steam from the high pressure section 12 flows into the reheat section 13 through the intermediate gland 30, so that the turbine rotor near the first stage turbine stage of the reheat section Outer surface 31a, 3
The temperature change in 1b is not affected by the change in the reheated steam temperature measured by the thermocouple 28, but is strongly influenced by the steam humidity after the first stage of the high-pressure cylinder measured by the thermal lightning pair 20.

From this point of view, the thermal stress monitoring device, as shown in Figure 1,
The thermal lightning pair 20 measures the metal temperature of the first stage aft surface of the high pressure cylinder in the high pressure first stage steam chamber 18 to determine the high pressure part turbine rotor temperature distribution and the reheat part turbine rotor temperature distribution, and then calculate the reheat steam temperature. The thermal stress of the turbine rotor in the high pressure section and the reheat section is calculated, taking into consideration as necessary.

That is, the high pressure section 1 of the turbine rotor 14, which is not shown in FIG.
Thermal stresses of the rotor outer surfaces 21a, 21b, 21c of No. 2 and the rotor outer surfaces 31a, 31b of the reheating section 13 are determined. At that time, the turbine rotor surface temperature of the reheating section 13 is
It is desirable to proceed with the thermal stress calculation by considering a heat transfer coefficient of a predetermined value as a delay element in the measured value of the inner metal temperature of the steam chamber with one high pressure cylinder installed.

Next, the principle of temperature distribution measurement for determining the hot part of the turbine rotor will be explained using a general difference method as an example.

Figure 5 shows the turbine rotor 1 whose thermal stress is to be calculated.
FIG. 4 is a diagram in which the axis-perpendicular cross section of No. 4 is divided into elements for calculation of the difference method. From this element division diagram, time τ + Δτ of element i
The temperature at J3 is expressed by the following equation.

Tiτ+Δ' −T + 'r+ ΔT + ' ”
""" (4)・Δτ Here, ΔT1 is the element i・Δτ at time Δτ
This temperature rise ΔT1 is the − corner (
T, -T, +1)...It is expressed as (5).

However, D is the heat flow rate between each element.

This heat Q flow rate is expressed by the following equation.

(6) where λ: heat transfer coefficient of the turbine rotor material α: heat transfer coefficient of the outer surface of the turbine rotor R.: radius ζ of the rotor to element i.

Also, the heat capacity C, of element i is C1 = 2πR1ΔRC, 7... (7) 1 or However, C: Specific heat of turbine rotor material γ: Specific weight of turbine rotor material It is expressed as

Therefore, from the above equations, if the initial temperature distribution Ti° at time τ=O is known, it is possible to calculate the temperature of element i after Δτ time, Nff1ΔT1 above Δτ degrees, based on the initial temperature distribution. can. From this, the temperature T of element 1 at any time τ+Δτ,
r+′! 1r can be found. However, temperature T1
Since the heat transfer coefficient α of the outer surface of the turbine rotor and the heat transfer coefficient α are time-related variables, care must be taken. The temperature T1 is the steam temperature in contact with the turbine rotor surface, and the heat transfer coefficient α is determined from the pressure and temperature of the steam and the relative speed between the steam and the turbine rotor on the turbine rotor surface, and is determined according to the operating state of the turbine. It becomes a function of time.

Now, if the heat transfer coefficient α of the outer surface of the turbine rotor is set to α=■ or a sufficiently large value, then the lower surface temperature of the turbine rotor and the steam temperature T1 become equal. As this steam temperature T1, the inner metal temperature of the steam chamber after the high pressure first stage is adopted for the high pressure section 12, and the inner metal temperature of the reheat steam chamber for the reheating section 13, and these metal temperatures are approximately The conventional method is to use it as the turbine rotor surface temperature. The method for monitoring thermal stress of a turbine rotor according to the present invention includes
For the reheating section 13, the internal metal temperature of the high-pressure first stage steam chamber is basically adopted, and the reheating section 13 is calibrated using the reheating steam temperature as necessary.

In addition, the main steam temperature is used instead of the inner metal temperature of the steam chamber after the high-pressure first stage, and the reheat steam temperature is used instead of the inner metal temperature of the reheat steam chamber, and appropriate corrections are made to these to determine the required turbine temperature. It has long been known to calculate the steam temperature T1 at the rotor surface.

Next, a method for monitoring hot part horns of a turbine rotor will be described based on the prior art and the method based on the present invention.

Figures 6 (A) and (B) show graphs that organize the temperature measurement data of the actual turbine rotor of a high-medium pressure integrated turbine; Figure 6 (A) is a temperature record graph of the actual turbine rotor; FIG. 6(B) is a graph showing the heat bath force meter R+a for each temperature distribution of the combinations shown in FIG. 6(A).

First, in FIG. 6 (△), the temperature curve a is a plot of the actual measured value of the inner metal temperature of the reheat steam chamber (the rotor surface temperature of the reheat section turbine rotor at the reheat steam temperature M), Code b , b .

b3 is the heat transfer coefficient α of the turbine rotor 14 of 200 kca.
l/rd-hr-'C1500kcal/TI1
．． -hr-'C and 10000kcal/TIt-h
This is a calculated temperature curve plotting the reheating section turbine rotor surface temperature calculation 0α based on the high-pressure first stage steam chamber inner surface metal temperature when r-℃ is different, and the symbol C
1 is a graph plotting actual surface temperature measurements of the turbine rotor bore portion 33a of the reheating section 13, and d is a graph plotting the turbine rotor bore temperature πtRl calculated based on the inner metal temperature of the reheating steam chamber. It is. Also,
Code e, e2. Since e3 plots the turbine rotor bore thermometer values determined based on the inner metal temperature of the high-pressure first stage steam chamber, the heat transfer coefficient α of the turbine rotor is 200 kcal/TIt-hr・'C1500
kcal/rd-hr-'C110000kcal
/ rrt・hr・℃ is a graph.

As is clear from FIG. 6(A), the change in the measured temperature curve C of the turbine rotor bore 14a is completely different from the reheat steam chamber inner metal temperature a, that is, the turbine rotor bore temperature change trend of the reheat steam lti. 57, and it is not possible to find a correction method necessary to make them coincide.

On the other hand, the turbine rotor bore temperature e, e3. based on the high pressure first stage steam chamber metal temperature. By appropriately adjusting the heat transfer coefficient α of the turbine rotor 14, e4 can obtain extremely good consistency with the actually measured temperature curve C of the turbine rotor. Based on a large amount of measured data, for example, the heat transfer coefficient α is between 300 and 1000.
It has been found preferable to use a turbine rotor of kcal/yd-hr-'C.

Next, from the heat bath horn curves △, B, C, and D of the turbine rotor shown in Figure 6 (B), the thermal stress change trend is determined based on reheat steam (based on reheat steam temperature, etc.). Thermal stress curve A is the same as that of high-pressure steam-based thermal stress curves B, C,
It is completely different from D, and there is no correlation between the point of maximum thermal stress generation and its magnitude. Therefore, the maximum thermal stress required for life management of the turbine rotor 14 must be monitored on a steam basis after the island pressure first stage, which can be matched to the actually measured bore temperature of the turbine rotor.

Next, other embodiments of the invention will be described.

Fig. 7 shows an enlarged view of the first stage of the reheating section from the intermediate gland section 30 in the high-intermediate pressure integrated turbine. Hot steam can flow as shown by the broken line Sb.

In this case, the steam that controls the temperature of the rotor surface of the turbine rotor 14 in the reheating section 13 is partially affected by [F] of the reheating steam as well as leaked steam from the high pressure section.

Therefore, the steam temperature T1 is T = m7 + nTn3
+zm (8) I FSI Where, T: Leakage steam temperature from the high pressure section SI T: Reheat steam temperature ST m, n: Can be determined from coefficients determined by design conditions. Therefore, by appropriately determining the coefficients m and n, the influence of leaked steam and reheated steam can be taken into consideration.

In this case, the measured value of the inner metal temperature of the high-pressure steam chamber may be the first stage post-steam temperature determined by taking into account operating parameters such as main steam temperature, main steam pressure, and turbine load. Further, the measured value of the inner metal temperature of the reheating steam chamber of the reheating section may be the reheating steam chamber steam temperature determined from operating parameters such as the reheating steam temperature and the reheating steam pressure, and may be −b.

(Effects of the Invention) As described above, in this invention, the surface temperature of the turbine rotor in the reheating section is set from the measured value of the inner metal temperature of the steam chamber after the high-pressure first stage, and the intermediate gland section is connected to the rod from the high-pressure section. By incorporating the influence of leaked steam flowing into the reheating section into the monitoring of thermal stress in the turbine rotor, the accuracy of thermal stress monitoring of the turbine rotor, especially the intermediate pressure rotor (reheating rotor) section, can be dramatically improved. Therefore, long-term maintenance management and rotor life management of the turbine rotor can be performed accurately and accurately.

In particular, in high- and intermediate-pressure integrated turbines that are frequently required to perform rapid startup and shutdown operations, the thermal stress of the rotor can be accurately monitored, which greatly improves the reliability of the startup and shutdown operations themselves.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the thermal stress monitoring method for a turbine rotor according to the present invention, FIG. 2 is a diagram showing a high-medium pressure integrated steam turbine to which the present invention is applied, and FIG. FIG. 4 is an axial sectional view showing the turbine rotor incorporated in the high- and intermediate-pressure integrated steam turbine; FIG. 5 is a cross-sectional view perpendicular to the axis of the turbine rotor. Diagram divided into elements for humidity distribution calculation by the difference method, Figure 6 (A> and (B)
) is a diagram showing the temperature measurement test data graph of the actual turbine rotor and a graph of the thermal stress of the turbine rotor calculated from the arrangement results. Figure 7 shows a modified example of the high-medium pressure integrated steam turbine. FIG. 8 is a block diagram showing a conventional method for monitoring thermal stress of a turbine rotor. 10.11...Casing, 12...High pressure part, 13
... Reheating section, 14... Turbine rotor, 14a...
・Turbine rotor bore, 15...Main steam pipe, 16...
・Nozzle box, 17...Turbine impeller, 18・
・・High pressure 1st stage rear steam chamber, 20.28・Thermocouple, 2
3... Reheat steam pipe, 24... Reheat steam room, 25...
- Reheat first stage nozzle, 26... Reheat first stage turbine impeller, 30... Intermediate gland section. A certain 1 Figure f; 2 Hard #α Sheep 3 Figure vine 5 Figure a certain 7 Figure hand 6 Illustration procedure ne 1n original (method) 6゜Showa 6
April 1st, 2015, Patent Office Commissioner Uga Michi Department
Sir,. 1. Indication of the case Patent Application No. 22993 of 1985 2. Name of the invention Method for monitoring thermal stress of turbine rotor 3. Person making the amendment Relationship to the case Patent applicant (307) Toshiba Corporation 4, Agent 〒 105 5. Date of amendment order Contents of the amendment in the "Claims" column of the specification subject to amendment 2. Claims 1. A high- and intermediate-pressure integrated turbine rotor is housed in a turbine casing that includes a high-pressure section and a reheat section in the axial direction.In order to monitor the thermal stress of this turbine rotor, the internal metal temperature of the steam chamber after the high-pressure first stage is measured. In the method for monitoring thermal stress of the turbine rotor, the surface temperature of the turbine rotor in the reheating section is set from the measured value of the inner metal temperature of the high-pressure first stage steam chamber, and the surface temperature of the turbine rotor in the reheating section is set from the measured value of the inner metal temperature of the high-pressure first stage steam chamber. A method for monitoring thermal stress of a turbine rotor, characterized in that the influence of leakage steam flowing into the turbine rotor is incorporated into the thermal stress monitoring of the turbine rotor. 2. Claims characterized in that when setting the surface temperature of the rotor of the reheating section, the heat transfer coefficient of a predetermined clay is taken into account as a delay factor in the measured value of the internal metal temperature of the steam chamber after the high-pressure first stage. The method for monitoring thermal stress of a turbine rotor according to item 1. 3. When setting the reheat gIi rotor surface temperature, the high pressure first
t1, which is obtained by adding the measured values of the internal metal temperature of the stage steam chamber and the internal metal temperature of the reheating section reheating steam chamber at an appropriate ratio, respectively.
A method for monitoring thermal stress in a turbine rotor according to claim 1, characterized in that a calculated temperature is used. 4. The measured value of the inner metal temperature of the steam chamber after the first stage is the first stage steam invasion temperature, which is determined by taking into account operating parameters such as main steam temperature, main steam pressure, turbine load, etc. A method for monitoring thermal stress of a turbine rotor according to claim 1 or 3. 5. The measured value of the inner metal temperature of the reheating steam chamber of the reheating section is the reheating steam chamber steam temperature determined from operating parameters such as the reheating steam temperature and the reheating steam pressure, as set forth in claim 3. A method for monitoring thermal stress in turbine rotors.

Claims (1)

[Claims] 1. A high- and intermediate-pressure integrated turbine rotor is housed in a turbine casing that includes a high-pressure section and a reheating section in the axial direction, and a high-pressure first In a turbine rotor thermal stress monitoring method that detects the inner metal temperature of the post-stage steam chamber, the turbine rotor surface temperature of the reheating section is set from the measured value of the inner metal temperature of the high-pressure first stage steam chamber, and the temperature is set from the high-pressure section to the intermediate gland. A method for monitoring thermal stress of a turbine rotor, characterized in that the influence of leakage steam flowing into a reheating section via a section is incorporated into thermal stress monitoring of a turbine rotor. 2. When setting the reheat section rotor surface temperature, a heat transfer coefficient of a predetermined value is taken into account as a delay factor in the measured value of the internal metal temperature of the steam chamber after the high-pressure first stage. A method for monitoring thermal stress of a turbine rotor according to scope 1. 3. When setting the reheating section rotor surface temperature, calculate the temperature by adding the measured values of the inner metal temperature of the steam chamber after the high pressure first stage and the inner metal temperature of the reheating steam chamber at an appropriate ratio. A thermal stress monitoring method for a turbine rotor according to claim 1, wherein the method is used. 4. The measured value of the inner metal temperature of the high-pressure first stage after-steam chamber is the first-stage after-steam temperature calculated in consideration of operating parameters such as main steam temperature, main steam pressure, and turbine load. The method for monitoring thermal stress of a turbine rotor according to item 1 or 3. 5. The measured value of the internal metal humidity in the reheating steam chamber of the reheating section is the reheating steam chamber steam temperature determined from operating parameters such as the reheating steam temperature and the reheating steam pressure, as set forth in claim 3. A method for monitoring thermal stress in turbine rotors.