Steam turbine facility operation method

Abstract

This steam turbine facility operation method is for operating a steam turbine facility that includes a high-pressure turbine to which steam generated by using heat generated by a nuclear reactor is supplied, and a low-pressure turbine to which steam discharged from the high-pressure turbine is supplied, said method including a step for driving the high-pressure turbine and the low-pressure turbine under output conditions of 500 MW or less and steam conditions in which the ratio of the difference between the inlet pressure of the low-pressure turbine and the outlet pressure of the low-pressure turbine to the difference between the inlet pressure of the high-pressure turbine and the outlet pressure of the low-pressure turbine is 0.16 or less.

Description

Steam turbine equipment operation method

[0001] This application claims priority to Japanese Patent Application No. 2024-133980, filed with the Japan Patent Office on August 9, 2024, the contents of which are incorporated herein by reference.

[0002] Generally, in steam turbines for nuclear power plants, the temperature and pressure of steam at the inlet of the low-pressure turbine are lower than in steam turbines for thermal power plants, and the steam becomes wet soon after entering the low-pressure turbine, resulting in a high degree of wetness at the outlet of the low-pressure turbine. High steam wetness in steam turbines leads to increased moisture loss and erosion due to water droplets, so measures must be taken.

[0003] Patent Document 1 discloses a nuclear power plant in which a steam pipe with a larger diameter than conventional is provided between a high-pressure turbine and a low-pressure turbine. By using such a steam pipe with a larger diameter than conventional, the low-pressure turbine inlet pressure is reduced compared to conventional cases, slowing the steam flow rate and lengthening the residence time of steam in a moisture separator heater provided in the steam pipe, thereby improving the performance of the moisture separator heater.

[0004] International Publication No. 2017 / 029911

[0005] In a steam turbine for a nuclear power plant, when trying to suppress the effects (wetness loss and erosion) caused by high steam wetness, it is possible to reduce the steam pressure at the low-pressure turbine inlet as described in Patent Document 1, or to increase the steam temperature at the low-pressure turbine inlet.

[0006] However, the temperature of the steam at the inlet of the low-pressure turbine is limited by factors such as the temperature of the heat source for reheating the steam flowing from the high-pressure turbine to the low-pressure turbine, and so there is a limit to how high it can be increased. Also, as described in Patent Document 1, the steam pressure at the inlet of the low-pressure turbine can be reduced by increasing the diameter of the piping between the high-pressure turbine and the low-pressure turbine, but if the piping diameter is increased, it becomes difficult to manufacture a large-capacity valve that fits the piping, so there is a limit to how low the steam pressure at the inlet of the low-pressure turbine can be reduced.

[0007] For this reason, conventional nuclear power plants operate steam turbine equipment under operating conditions where the steam in the steam turbine has a relatively high wetness. To combat this, a drain catcher is installed on the first stage of the low-pressure turbine. The drain catcher includes a recess in the wall of the casing, and is designed to catch and collect water droplets that are thrown radially outward by the centrifugal force of the rotor blades.

[0008] Meanwhile, there is an increasing demand for small modular reactors (SMRs), which are smaller and designed for lower power output than conventional nuclear reactors. In low-power nuclear power plants using SMRs or the like, it is desirable to operate steam turbines under conditions that can suppress the effects of steam wetness (wetness loss and erosion).

[0009] In view of the above circumstances, at least one embodiment of the present invention aims to provide a method for operating steam turbine equipment that can reduce the risk of steam wetness and erosion in steam turbine equipment in a low power range.

[0010] According to at least one embodiment of the present invention, there is provided a method for operating steam turbine equipment including a high-pressure turbine supplied with steam generated using heat generated in a nuclear reactor, and a low-pressure turbine supplied with steam discharged from the high-pressure turbine, the method comprising the steps of driving the high-pressure turbine and the low-pressure turbine under steam conditions where a ratio of a difference between an inlet pressure of the high-pressure turbine and an outlet pressure of the low-pressure turbine to a difference between an inlet pressure of the low-pressure turbine and an outlet pressure of the low-pressure turbine is 0.16 or less, and under an output condition of 500 MW or less.

[0011] According to at least one embodiment of the present invention, there is provided a method for operating a steam turbine facility in a low power range, which can reduce the risk of steam loss and erosion due to steam wetness.

[0012] Fig. 1 is a schematic diagram showing a steam turbine facility according to an embodiment. Fig. 2 is a schematic diagram showing the configuration of a nuclear reactor according to an embodiment. Fig. 3 is a schematic diagram showing the configuration of a turbine blade of a steam turbine according to an embodiment. Fig. 4 is an is-s diagram showing the relationship between specific enthalpy and specific entropy during expansion of a working fluid (steam) in several low-pressure turbines.

[0013] Hereinafter, several embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present invention.

[0014] (Configuration of Steam Turbine Facility) Fig. 1 is a schematic diagram showing an example of steam turbine facility to which an operation method according to some embodiments is applied. Fig. 2 is a schematic diagram showing the configuration of a nuclear reactor according to one embodiment. Fig. 3 is a schematic diagram showing the configuration of turbine blades of a steam turbine according to one embodiment.

[0015] As shown in FIG. 1 , a steam turbine facility 1 according to one embodiment includes a steam generating unit 2 for generating steam by utilizing heat generated in a nuclear reactor 100 ( FIG. 2 ), a high-pressure turbine 6 to which steam (main steam) from the steam generating unit 2 is supplied, and a low-pressure turbine 10 to which steam discharged from the high-pressure turbine 6 is supplied.

[0016] Steam (main steam) generated in the steam generating section 2 is guided to a high-pressure turbine 6 via a high-pressure steam line 4. A valve 5 for adjusting the flow rate of steam supplied to the high-pressure turbine 6 may be provided on the high-pressure steam line 4. The steam whose temperature and pressure have been reduced after performing work in the high-pressure turbine 6 is discharged from the high-pressure turbine 6 and guided to a low-pressure turbine 10 via a low-pressure steam line 8. A valve 9 for adjusting the flow rate of steam supplied to the low-pressure turbine 10 may be provided on the low-pressure steam line 8.

[0017] The low-pressure steam line 8 is provided with a reheat section 20 for reheating steam flowing from the outlet of the high-pressure turbine 6 to the inlet of the low-pressure turbine 10. The reheat section 20 may include a moisture separator heater configured to remove moisture contained in the steam and heat the steam. As shown in FIG. 1 , the reheat section 20 may be configured to heat the low-pressure steam line 8 using steam generated in the steam generating section 2 as a heat source. In the exemplary embodiment shown in FIG. 1 , main steam from the steam generating section 2 is supplied to the reheat section 20 via a branch line 18 branching off from the high-pressure steam line 4.

[0018] The steam, whose temperature and pressure have dropped after performing work in the low-pressure turbine 10, is discharged from the low-pressure turbine 10 and guided to the condenser 16. In the condenser 16, the steam is condensed by heat exchange with a coolant (seawater, etc.), and condensate is generated. The condensate generated in the condenser 16 is returned to the steam generating section 2 via a condensate line 14.

[0019] 1 , the steam turbine equipment 1 may include a generator 12 connected to the rotating shafts of the high-pressure turbine 6 and the low-pressure turbine 10 and configured to be rotationally driven by the high-pressure turbine 6 and the low-pressure turbine 10. In other words, the steam turbine equipment 1 may be a power generation plant.

[0020] 2 , the nuclear reactor 100 includes a primary cooling loop 30 through which primary cooling water (primary coolant) flows, and a pressure vessel (reactor vessel) 32, a pressurizer 34, a steam generating unit (steam generator) 2, and a primary coolant pump (coolant pump) 38 provided in the primary cooling loop 30. The primary coolant pump 38 is configured to circulate the primary coolant in the primary cooling loop 30. The pressurizer 34 is configured to pressurize the primary coolant in the primary cooling loop 30 so that the primary coolant does not boil. The pressure vessel 32, the pressurizer 34, the steam generating unit 2, and the primary coolant pump 38 are housed in a reactor containment vessel 40.

[0021] The pressure vessel 32 contains fuel rods containing pellet-shaped nuclear fuel (e.g., uranium fuel, MOX fuel, etc.), and the primary coolant in the pressure vessel 32 is heated by the thermal energy generated by the nuclear fission reaction of this fuel. The pressure vessel 32 is provided with control rods for absorbing and adjusting the number of neutrons generated in the reactor core containing the nuclear fuel in order to control the reactor power. The primary coolant heated in the pressure vessel 32 is sent to the steam generating section 2, and by heat exchange, heats the secondary coolant (secondary coolant) flowing in a secondary cooling loop including the high-pressure steam line 4, the low-pressure steam line 8, and the condensate line 14, thereby generating steam.

[0022] In some embodiments, the nuclear reactor 100 may include a small modular reactor (SMR). A small modular reactor is a small nuclear reactor that can be transported to an installation site after manufacturing, and has a lower output than the reactors used in general nuclear power plants (output: approximately 1000 MW or more), with the output of a power plant using a small modular reactor being approximately 500 MW or less.

[0023] The small modular reactor may be a small modular reactor using a light water reactor, a molten salt reactor, or a high-temperature gas reactor. The light water reactor as a small modular reactor may be a miniaturized version of a conventional pressurized water reactor (PWR) or a boiling water reactor (BWR), or an integrated pressurized water reactor (iPWR) in which a steam generator and reactor internals are integrated. Note that the reactor 100 shown in FIG. 2 is an example of a pressurized water reactor (PWR).

[0024] 3 is a partial schematic diagram of a low-pressure turbine 10 according to one embodiment. As shown in FIG. 3, the low-pressure turbine 10 includes stationary blades 101 (101A, 101B), an outer ring 102, an inner ring 103, rotor blades 104 (104A, 104B), and a disk 105.

[0025] The inner ring 103 is an annular member provided along the circumferential direction of the turbine rotor. The inner ring 103 has a hollow portion 115 therein. The outer ring 102 is an annular member provided radially outside the inner ring 103 along the circumferential direction of the turbine rotor. The stator vanes 101 are supported by a casing 110 via the outer ring 102. A plurality of stator vanes 101 are fixedly provided between the outer ring 102 and the inner ring 103 along the circumferential direction of the turbine rotor. A plurality of rotor blades 104 are attached to the outer periphery of a disk 105 along the circumferential direction of the turbine rotor.

[0026] A typical low-pressure turbine 10 includes rows of multiple stator vanes and rotor blades arranged along the axial direction. The low-pressure turbine 10 shown in Fig. 3 includes a front stage stator vane 101A, a front stage rotor blade 104A, a rear stage stator vane 101B, and a rear stage rotor blade 104B. The rear stage stator vane 101B and the rear stage rotor blade 104B are located downstream of the front stage stator vane 10A and the front stage rotor blade 104A in the axial direction.

[0027] At least some of the multiple stages of stator vanes 101 are provided with moisture recovery structures 106. In the exemplary embodiment shown in Figure 3, the rear stage stator vane 101B includes a drain catcher 107 as the moisture recovery structure 106. The drain catcher 107 includes a protrusion 108 that protrudes radially outward from the upstream end of the outer ring 102.

[0028] During operation of the steam turbine equipment 1, if the working fluid flowing through the low-pressure turbine 10 is wet steam, moisture (water droplets) 120 contained in the steam is scattered radially outward by the rotation of the front-stage rotor blades 104A. The drain catcher 107 captures the scattered moisture, thereby preventing water droplets from flowing into the rear-stage stator blades 101B. This reduces the moisture in the rear stages of the low-pressure turbine 10.

[0029] (Method of Operating Steam Turbine Facility) Next, a method of operating the steam turbine facility 1 according to some embodiments will be described. In some embodiments, the inlet pressure P Ｈ１ and the outlet pressure P of the low-pressure turbine 10 Ｌ２ The difference between Ｈ１ -P Ｌ２ ) the inlet pressure P of the low-pressure turbine 10Ｌ１ and the outlet pressure P of the low-pressure turbine 10 Ｌ２ The difference between Ｌ１ -P Ｌ２ ) ratio (P Ｌ１ -P Ｌ２ ) / (P Ｈ１ -P Ｌ２ In some embodiments, the high-pressure turbine 6 and the low-pressure turbine 10 are driven under steam conditions where the ratio (P Ｌ１ -P Ｌ２ ) / (P Ｈ１ -P Ｌ２ The high-pressure turbine 6 and the low-pressure turbine 10 are driven under steam conditions where the ratio of the heat transfer coefficient (HPC) to the heat transfer coefficient (HPC) is 0.15 or less or 0.14 or less, and under an output condition of 500 MW or less.

[0030] Fig. 4 is an is-s diagram showing the relationship between specific enthalpy (vertical axis) and specific entropy (horizontal axis) during expansion of a working fluid (steam) in several low-pressure turbines. The graph in Fig. 4 includes isothermal lines LT1 (250°C) and T2 (350°C), isobars LP1 (0.005 MPa(a)), LP2 (0.5 MPa(a)), and LP3 (1.0 MPa(a)), as well as isohumidity lines LM0 (saturation line), LM1 (10%), and LM2 (15%). Note that (a) in the pressure unit notation means absolute pressure.

[0031] 4 are expansion lines (curves showing changes in the state quantities of steam) from the inlet (points A1 to C1) of the low-pressure turbine to the outlet (points A2 to C2). Curve A is the expansion line of the low-pressure turbine 10 of the steam turbine equipment 1 (a low-output nuclear power plant such as an SMR) according to the above-described embodiment, curve B is the expansion line of the low-pressure turbine of a steam turbine equipment in a conventional nuclear power plant (one example) with a relatively high output, and curve C is the expansion line of the low-pressure turbine of a steam turbine equipment in a conventional thermal power plant (one example).

[0032] As shown in the graph of FIG. 4, in a conventional nuclear power plant (curve B), the steam temperature (inlet temperature T Ｌ１) is about 250°C. In a conventional nuclear power plant (curve B), the steam pressure of the low-pressure turbine varies from the inlet pressure (about 1.0 MPa(a)) to the outlet pressure (about 0.005 MPa(a)). The wetness of the steam at the outlet of the low-pressure turbine is about 15%.

[0033] In a conventional thermal power plant (curve C), the temperature of the steam at the inlet of the low-pressure turbine (point C1 on the graph) is approximately 350°C. In a conventional thermal power plant (curve C), the steam pressure of the low-pressure turbine varies from the inlet pressure (approximately 1.0 MPa(a)) to the outlet pressure (approximately 0.005 MPa(a)). The wetness of the steam at the outlet of the low-pressure turbine is approximately 10%.

[0034] In a conventional nuclear power plant, the inlet pressure P Ｈ１ is about 5.5 MPa (a), so in conventional nuclear power plants, the above pressure ratio (P Ｌ１ -P Ｌ２ ) / (P Ｈ１ -P Ｌ２ ) is about 0.18. In addition, the inlet temperature T Ｈ１ is about 270°C.

[0035] In contrast, according to the method of the above embodiment, the above pressure ratio (P Ｌ１ -P Ｌ２ ) / (P Ｈ１ -P Ｌ２ Since the steam turbine equipment 1 is operated under steam conditions where the temperature T Ｌ１is set to the same as that of a conventional nuclear power plant (for example, about 250°C), the expansion line (curve A) will be similar to the curve B of the conventional nuclear power plant, which is shifted parallel along the isothermal line, and the dryness / superheat of the steam at the inlet of the low-pressure turbine can be increased and the wetness of the steam at the outlet of the low-pressure turbine can be reduced. In other words, the wetness at the low-pressure turbine can be made the same as that of a conventional thermal power plant.

[0036] Furthermore, in the above-described embodiment, a low-power nuclear reactor such as a small modular reactor is used and is operated under low-power conditions of 500 MW or less, so even if the inlet pressure of the low-pressure turbine 10 is lowered as described above, the volumetric flow rate of steam does not become too large, and the diameter of the pipe connected to the inlet of the low-pressure turbine 10 (the pipe constituting the low-pressure steam line 8) does not become excessively large. Therefore, the size of the valve 9 provided on the pipe can be set within a range that can be realistically manufactured.

[0037] As described above, according to the method of the embodiment, in the steam turbine equipment 1 for a nuclear power plant, the inlet pressure P Ｈ１ and the outlet pressure P of the low-pressure turbine 10 Ｌ２ The inlet pressure P of the low-pressure turbine 10 relative to the difference Ｌ１ and the outlet pressure P of the low-pressure turbine 10 Ｌ２ Ratio of the difference (ratio of pressure difference) (P Ｌ１ -P Ｌ２ ) / (P Ｈ１ -P Ｌ２The high-pressure turbine 6 and the low-pressure turbine 10 are driven under steam conditions where the ratio (ρ) of the moisture content of the low-pressure turbine 10 to the moisture content of the low-pressure turbine 10 is 0.16 or less, 0.15 or less, or 0.14 or less, and under an output condition of 500 MW or less. Therefore, the wetness fraction in the low-pressure turbine can be lowered compared to steam turbines in the high-power range (e.g., over 1000 MW) for conventional nuclear power plants. Therefore, the risk of moisture loss and erosion due to the wetness of the steam can be reduced in the steam turbine equipment 1 for low-power nuclear power plants. Furthermore, in the method according to the above embodiment, the wetness fraction in the low-pressure turbine 10 is comparable to that of conventional low-pressure turbines for thermal power plants, so that the same design concepts as low-pressure turbines for thermal power plants can be applied. For example, the installation position of the moisture recovery structure can be designed similarly to that of low-pressure turbines for thermal power plants. Therefore, the development costs for low-pressure turbines for low-power nuclear power plants can be reduced.

[0038] In some embodiments, the inlet pressure P of the low-pressure turbine 10 Ｌ１ Alternatively, in some embodiments, the high-pressure turbine 6 and the low-pressure turbine 10 may be driven under steam conditions in which the inlet pressure P Ｌ１ The high-pressure turbine 6 and the low-pressure turbine 10 may be driven under steam conditions in which the pressure is 0.5 MPa(a) or more and 0.6 MPa(a) or less.

[0039] In the above embodiment, the inlet pressure P Ｌ１ Since the high-pressure turbine 6 and the low-pressure turbine 10 are driven under steam conditions where the inlet pressure P of the low-pressure turbine 10 is 0.5 MPa(a) or more or 0.4 MPa(a) or more, the plant performance can be improved while keeping the steam flow rate at the valve 9 provided in the inlet pipe of the low-pressure turbine 10 (piping constituting the low-pressure steam line 8) within an appropriate range. Ｌ１Since the high-pressure turbine 6 and the low-pressure turbine 10 are driven under steam conditions where the pressure difference is 0.7 MPa(a) or less or 0.6 MPa(a) or less, the pressure difference ratio can be easily set to 0.16 or less, 0.15 or less, or 0.14 or less in a steam turbine facility 1 with an output of 500 MW or less that uses a small modular reactor or the like. Therefore, according to the method of the above embodiment, in a steam turbine facility 1 for a low-power nuclear power plant, the performance of the plant can be improved while reducing the risk of wetness loss and erosion caused by wet steam.

[0040] In some embodiments, the inlet temperature T Ｌ１ The high-pressure turbine 6 and the low-pressure turbine 10 are driven under steam conditions in which the temperature of the steam is 220°C or higher and 280°C or lower.

[0041] According to the above-described embodiment, the inlet temperature T Ｌ１ is about the same as that of a conventional nuclear power plant, a configuration similar to that of a conventional nuclear power plant can be adopted as a configuration for reheating steam flowing from the outlet of the high-pressure turbine 6 to the inlet of the low-pressure turbine 10. Therefore, according to the above-described embodiment, it is possible to relatively easily reduce the risk of wetness loss and erosion caused by wetness of steam as described above.

[0042] In some embodiments, the low-pressure turbine 10 includes a front stage stator vane 101A that does not have a moisture recovery structure (such as a drain catcher), and a rear stage stator vane 101B that is provided downstream of the front stage stator vane 101A and has a moisture recovery structure 106 (a drain catcher 107 in FIG. 3 ), as shown in Fig. 3 for example. Drain (moisture such as water droplets) inside the low-pressure turbine 10 is recovered by the moisture recovery mechanism 106 provided in the rear stage stator vane 101B of the low-pressure turbine 10.

[0043] The forward stage stator vanes 101A are upstream stator vanes 101 including the first stage stator vanes 101 among the multiple stages of stator vanes 101, and the rearward stage stator vanes 101B are downstream stator vanes 101 including the final stage stator vanes 101 among the multiple stages of stator vanes 101. In some embodiments, of the multiple stages of stator vanes 101 of the low-pressure turbine 10, the forward stage stator vanes 101A including the first stage stator vanes 101 may not be provided with a moisture recovery structure (drain catcher, etc.), and the rearward stage stator vanes 101B including the final stage stator vanes 101 may be provided with a moisture recovery structure (drain catcher, etc.).

[0044] In the method according to the above embodiment, the wetness in the low-pressure turbine 10 is comparable to that of a conventional low-pressure turbine for a thermal power plant, so the same design concept as that of a low-pressure turbine for a thermal power plant can be used. For example, as described above, a configuration can be adopted in which the moisture recovery structure 106 (drain catcher 107, etc.) is not provided on the front stage stator vanes 101A but only on the rear stage stator vanes 101B, as in a typical low-pressure turbine for a thermal power plant. This reduces the development costs of a low-pressure turbine for a low-power nuclear power plant. Therefore, in the steam turbine equipment 1 for a low-power nuclear power plant, the risk of wetness loss and erosion due to steam wetness can be reduced at low cost.

[0045] In some embodiments, steam from the high-pressure turbine 6 is introduced to the low-pressure turbine 10 via piping provided between the high-pressure turbine 6 and the low-pressure turbine 10 and having a diameter of 50 inches or more. That is, the diameter of the piping constituting the low-pressure steam line 8 provided between the high-pressure turbine 6 and the low-pressure turbine 10 may be 50 inches or more.

[0046] According to the above-described embodiment, the diameter of the pipe for guiding steam from the high-pressure turbine 6 to the low-pressure turbine 10 is 50 inches or more, so in the steam turbine equipment 1 with an output of 500 MW or less, the above-described pressure difference ratio (P Ｌ１ -P Ｌ２ ) / (P Ｈ１ -P Ｌ２) can be easily set to 0.16 or less, 0.15 or less, or 0.14 or less. Therefore, according to the above-described embodiment, it is possible to reduce the risk of wetness loss and erosion caused by wetness of steam in the steam turbine equipment 1 of a low-power nuclear power plant.

[0047] The contents described in each of the above embodiments can be understood, for example, as follows.

[0048] [1] At least one embodiment of the present invention relates to a method for operating a steam turbine facility (1), which includes a high-pressure turbine (6) to which steam generated by utilizing heat generated in a nuclear reactor (100) is supplied, and a low-pressure turbine (10) to which steam discharged from the high-pressure turbine is supplied, the method comprising: Ｈ１ ) and the outlet pressure of the low-pressure turbine (P Ｌ２ ) to the inlet pressure (P Ｌ１ ) and the outlet pressure of the low-pressure turbine (P Ｌ２ ) and the ratio of the difference (P Ｈ１ -P Ｌ２ ) / (P Ｌ１ -P Ｌ２ driving the high-pressure turbine and the low-pressure turbine under steam conditions such that a ratio of ρ / ρ of the high-pressure turbine to ρ / ρ of the low-pressure turbine is 0.16 or less and under an output condition of 500 MW or less.

[0049] According to the method [1] above, in a steam turbine facility for a nuclear power plant, the high-pressure turbine and the low-pressure turbine are driven under steam conditions where the ratio (pressure difference ratio) of the difference between the inlet pressure of the low-pressure turbine and the outlet pressure of the low-pressure turbine to the difference between the inlet pressure of the high-pressure turbine and the outlet pressure of the low-pressure turbine is 0.16 or less, and under an output condition of 500 MW or less. Therefore, the wetness fraction in the low-pressure turbine can be lowered compared to steam turbines for conventional high-power nuclear power plants (e.g., over 1000 MW). Therefore, in a steam turbine facility for a low-power nuclear power plant, the risk of wetness loss and erosion due to wetness of steam can be reduced. Furthermore, with the method [1] above, the wetness fraction in the low-pressure turbine is comparable to that of a low-pressure turbine for a conventional thermal power plant, allowing the moisture removal mechanism of the low-pressure turbine for a thermal power plant to be used as is. Therefore, the low-pressure turbine for a conventional thermal power plant can be used in a nuclear power plant, thereby reducing the development cost of a low-pressure turbine for a low-power nuclear power plant.

[0050] [2] In some embodiments, in the method of [1] above, the high-pressure turbine and the low-pressure turbine are driven under steam conditions such that the inlet pressure of the low-pressure turbine is 0.4 MPa(a) or more and 0.7 MPa(a) or less.

[0051] In the method [2] above, the high-pressure turbine and the low-pressure turbine are driven under steam conditions where the inlet pressure of the low-pressure turbine is 0.4 MPa(a) or higher, thereby enabling the steam flow rate at the valve of the low-pressure turbine inlet piping to be kept within an appropriate range and improving plant performance. Furthermore, in the method [2] above, the high-pressure turbine and the low-pressure turbine are driven under steam conditions where the inlet pressure of the low-pressure turbine is 0.7 MPa(a) or lower, making it easier to achieve the above-mentioned pressure difference ratio of 0.16 or less in steam turbine equipment with an output of 500 MW or less. Therefore, in steam turbine equipment for low-power nuclear power plants, the method [2] above makes it possible to reduce the risk of wetness loss and erosion due to steam wetness while improving plant performance.

[0052] [3] In some embodiments, in the method of the above [1] or [2], the inlet temperature (T Ｌ１ The high-pressure turbine and the low-pressure turbine are driven under steam conditions in which the temperature of the high-pressure turbine is 220°C or higher and 280°C or lower.

[0053] According to the method of [3] above, since the inlet temperature of the low-pressure turbine is about the same as that of a conventional nuclear power plant, a configuration similar to that of a conventional one can be adopted for reheating the steam flowing from the outlet of the high-pressure turbine to the inlet of the low-pressure turbine. Therefore, according to the configuration of [3] above, it is possible to relatively easily reduce the risk of wetness loss and erosion caused by the wetness of the steam as described in [1] above.

[0054] [4] In some embodiments, in any of the methods [1] to [3] above, the low-pressure turbine includes a plurality of stages of stator vanes (101A, 101B) arranged in the axial direction, and the plurality of stages of stator vanes include: a front stage stator vane (101A) that does not have a moisture recovery structure (106); and a rear stage stator vane (101B) that is provided axially downstream of the front stage stator vane and has a moisture recovery structure (106), and the method of operating the steam turbine facility includes a step of recovering drain water in the low-pressure turbine by the moisture recovery structure.

[0055] According to the method [4] above, moisture is removed from the low-pressure turbine through slits provided in the stator vanes, as in conventional low-pressure turbines for thermal power plants, so that conventional low-pressure turbines for thermal power plants can be used in nuclear power plants. Therefore, the development costs of low-pressure turbines for low-power nuclear power plants can be eliminated, and the risk of moisture loss and erosion caused by steam moisture can be reduced at low cost in steam turbine equipment for low-power nuclear power plants.

[0056] [5] In some embodiments, in any of the methods [1] to [4] above, the method of operating a steam turbine includes a step of introducing steam from the high-pressure turbine to the low-pressure turbine through a pipe provided between the high-pressure turbine and the low-pressure turbine and having a diameter of 50 inches or more.

[0057] According to the method [5] above, since the diameter of the pipe for guiding steam from the high-pressure turbine to the low-pressure turbine is 50 inches or more, it is easy to make the pressure difference ratio 0.16 or less in steam turbine equipment with an output of 500 MW or less. Therefore, according to the method [5] above, it is possible to reduce the risk of wetness loss and erosion caused by wet steam in steam turbine equipment for low-power nuclear power plants.

[0058] The above describes an embodiment of the present invention, but the present invention is not limited to the above-described embodiment, and also includes forms in which the above-described embodiment is modified, or forms in which these forms are appropriately combined.

[0059] In this specification, expressions expressing relative or absolute arrangements, such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," not only strictly express such arrangements, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions expressing that things are in an equal state, such as "identical," "equal," and "homogeneous," not only express a state in which there is a strict equivalence, but also express a state in which there is a tolerance or a difference to the extent that the same function is obtained. Furthermore, in this specification, expressions expressing shapes such as a rectangular shape or a cylindrical shape not only express shapes such as a rectangular shape or a cylindrical shape in the strict geometric sense, but also express shapes including concave and convex portions, chamfered portions, etc., to the extent that the same effect is obtained. Furthermore, in this specification, the expressions "comprise," "include," or "have" a component are not exclusive expressions that exclude the presence of other components.

[0060] REFERENCE SIGNS LIST 1 steam turbine equipment 2 steam generation section 4 high-pressure steam line 5 valve 6 high-pressure turbine 8 low-pressure steam line 9 valve 10 low-pressure turbine 12 generator 14 condensate line 16 condenser 18 branch line 20 reheat section 30 primary cooling loop 32 pressure vessel 34 pressurizer 38 primary coolant pump 40 reactor containment vessel 100 reactor 101 stator vane 102 outer ring 103 inner ring 104 moving blade 105 disk 106 moisture recovery structure 107 drain catcher 108 protrusion 110 casing 120 moisture (water droplets)

Claims

1. A method for operating a steam turbine facility including a high-pressure turbine supplied with steam generated using heat generated in a nuclear reactor, and a low-pressure turbine supplied with steam exhausted from the high-pressure turbine, comprising the steps of driving the high-pressure turbine and the low-pressure turbine under steam conditions such that the ratio of the difference between the inlet pressure of the high-pressure turbine and the outlet pressure of the low-pressure turbine to the difference between the inlet pressure of the low-pressure turbine and the outlet pressure of the low-pressure turbine is 0.16 or less, and under output conditions of 500 MW or less.

2. A method for operating steam turbine equipment according to claim 1, wherein the high-pressure turbine and the low-pressure turbine are driven under steam conditions such that the inlet pressure of the low-pressure turbine is 0.4 MPa(a) or more and 0.7 MPa(a) or less.

3. A method for operating a steam turbine facility according to claim 1 or 2, wherein the high-pressure turbine and the low-pressure turbine are driven under steam conditions such that the inlet temperature of the low-pressure turbine is 220°C or higher and 280°C or lower.

4. A method for operating steam turbine equipment according to claim 1 or 2, wherein the low-pressure turbine includes multiple stages of stator vanes arranged in the axial direction, the multiple stages of stator vanes including: front stage stator vanes without a moisture recovery structure; and rear stage stator vanes provided axially downstream of the front stage stator vanes and having a moisture recovery structure, and the method includes a step of recovering drainage from within the low-pressure turbine using the moisture recovery structure.

5. A method for operating a steam turbine facility according to claim 1 or 2, comprising the step of introducing steam from the high-pressure turbine to the low-pressure turbine through a pipe provided between the high-pressure turbine and the low-pressure turbine and having a diameter of 50 inches or more.

Images