JPS62237011A - Steam turbine forcibly cooling device for nuclear power generation - Google Patents

Abstract

PURPOSE:To permit the forcibly cooling of a turbine casing by connecting the seat drain pipe of a main steam stop valve connected with a high pressure casing and an off-gas piping through a vacuum pump. CONSTITUTION:A main steam stop valve 7 is installed into a main steam inlet pipe 5 connected with a high pressure turbine inlet part 4, and a seat drain pipe 8 is connected with an off-gas pipe 12 for the communication between an air extracting device 11 and a funnel through a vacuum pump 23. After the turbine stop, an air stop valve 16 in a piping 15 is opened to operate the vacuum pump 23, and air is introduced into a casing 2, which is cooled. Therefore, the high pressure turbine can be cooled in a short time, and the generation of thermal stress and crack of a turbine rotor, etc. can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a steam turbine for nuclear power generation in which disassembly work can be started immediately after the high pressure turbine in the steam turbine for nuclear power generation is stopped.

[Conventional technology]

Forced cooling devices in steam turbines for thermal power generation include, for example, the "Turbine Cooling Device" described in Japanese Utility Model Publication No. 52-57281 and the "Steam Turbine Cooling Method and Method" described in Japanese Patent Publication No. 60-33968. "The device" etc. The above inventions each have excellent practical effects regarding the cooling method of steam turbines, but in the case of steam turbine prime movers for nuclear power generation, the inventions are difficult to achieve due to steam conditions specific to nuclear power generation and contamination by radiation. There are also difficult issues that have not been touched upon.

In a high-pressure turbine of a nuclear power turbine, the turbine casing has a structure that can be divided into an upper casing and a lower casing, as is well known, in order to facilitate periodic inspections or opening and inspection in emergencies. and,
The upper casing and lower casing are tightened together by bolts at the horizontal flange of each casing.

In addition, the turbine casing includes a turbine rotor, backing case, packing head, and diaphragm (not shown).
etc. are assembled with appropriate gaps maintained by fastening parts. Furthermore, metal heat insulation or inorganic heat insulation is maintained on the outside of the casing in order to prevent heat dissipation from the casing. The entire high-pressure turbine is usually covered with a shielding plate to block radiation.

On the other hand, in order to disassemble and inspect the high-pressure turbine during regular inspections or in emergency situations, it is necessary to disassemble the casing and disassemble each built-in component. If the metal temperature of the casing (high-pressure first stage stone) is not cooled to 150℃, thermal stress will be applied to the turbine rotor and turbine casing. Later, disassembly work began.

That is, the fact that disassembly work can only be started five minutes after the turbine has been stopped will unnecessarily lengthen the outage period.

Therefore, if the disassembly work can be started immediately after the turbine is stopped, the stoppage period can be shortened.

Nuclear power generation facilities have been constructed with a huge amount of investment, and must always be operated in a way that minimizes downtime.

Once the system starts operating, it generates huge profits (profits from selling electricity), so the economic gains and losses caused by the length of the outage period are immeasurably large. Therefore, a major challenge was how to minimize the period during which the turbine was stopped and generate a huge profit.

[Problem that the invention seeks to solve]

The present invention measures the metal temperature of the high-pressure turbine casing by connecting piping to the seat drain pipe of the main steam stop valve, which is connected to the casing via the main steam pipe, and by installing a vacuum pump in the middle of this piping.

The present invention provides a system for shortening the period during which the turbine is stopped by introducing air into the turbine chambers before and after the high-pressure turbine, thereby shortening the conventional natural cooling period of two days under the sun.

[Means for solving problems]

The feature of the present invention is that the metal temperature of the high-pressure turbine is not controlled by the natural cooling method, but is installed before and after the high-pressure turbine in a low-temperature part of the high-pressure turbine and connected to a moisture separator that has finished its work. Air is forced into the gap between the comb teeth of the shaft backing ring and the turbine rotor, and the seat drain pipe of the main steam stop valve is connected via the main steam inlet pipe connected to the casing. This pipe is connected to the off-gas pipe connected from the low-pressure turbine via the condenser to the off-gas equipment connected to the off-gas pipe, and the chimney installed in the turbine building via rare gas hold-up equipment. This is achieved by discharging the

[Effect]

The present invention connects the seat drain pipe of the main steam stop valve connected to the high-pressure casing and the off-gas piping via a vacuum pump, thereby forcibly feeding air into the high-pressure turbine casing. The reason is that the turbine casing can be forcedly cooled, and the metal temperature of the turbine casing can be brought to a temperature that allows the turbine to be opened in a short time after the turbine is stopped.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

It is. Moreover, FIG. 2 shows a schematic diagram of the air inlet section. The air inside the turbine chamber is used as cooling air 1 to pass through the comb teeth of the shaft backing part 3 before and after the high-pressure turbine 2 and the turbine rotor 2.
4 through the gap AA section in the turbine casing 2, which is a low-temperature section connected to the moisture separator 19 where the high-pressure turbine has finished its work. It passes through the high-pressure turbine inlet section 4, which is a high-temperature section at about 282° C., and is led to the main steam stop valve 7 via the main steam inlet pipe 5, the seat drain pipe 7, the low-pressure turbine 8, the condenser 10, and the air extractor. 11, and off-gas equipment 13. by connecting the vacuum pump 23 via the off-gas pipe 12 to the off-gas plumber 2 using the connecting pipe 15. Turbine building 17 via rare gas hold-up equipment 14
The cooling air 1 can be discharged to the atmosphere through the chimney 18 installed outdoors, and optimal cooling can be performed without applying thermal stress to the turbine casing 2, turbine rotor 24, etc. The connection to the off-gas plumber 2 is in the high pressure turbine 2 contaminated by radiation.
This is because sufficient consideration has been given to the exhaust treatment of the air that has passed through. In this case, the air stop valve 16 is kept closed during plant operation.

High-temperature, high-pressure steam from the nuclear reactor (not shown) is transferred to main steam pipe 1.
5 to the high pressure turbine 2.

A steam control valve 6 and a main steam stop valve 7 are installed in the middle of the main steam 5, and the main steam enters the high-pressure turbine 2 through these. The steam that has worked in the high pressure turbine 2 is transferred to the cross-around pipe 20. It is conducted via a moisture separator 19 and a combined intermediate valve 21 to a low-pressure turbine 9 where it performs work.

Further, the steam that has completed its work in the low pressure turbine 9 is discharged to the condenser 10, where it is condensed.

Among the turbines 2 and 3, the high-pressure turbine 2 in particular uses high-temperature steam, and therefore requires a very long time to cool down when the turbine is stopped, so the cooling device of the present invention is applied here.

That is, the air introducing means operates the vacuum pump 23 to supply the air in the turbine chamber to the high-pressure turbine 2 prior to opening when the turbine is stopped.

The operating means is to close the main steam stop valve 79 combination intermediate valve 21 that occurs when the turbine is stopped, and close the cross-around pipe 2.
Drain pipe from 022. Steam control valve seat drain pipe 22
．． The drain pipe 22 of the main steam inlet pipe is fully opened, and after each drain is discharged, each is closed, and the air stop valve 16 of the piping 15 is closed.
By opening the casing and operating the vacuum pump 23 to introduce air into the casing 2, cooling inside the casing is started.

This air valve 16 can cool the high-pressure turbine 2 while flowing in the opposite direction to the steam inflow direction during operation, that is, from the low-temperature part on the outlet side toward the low-temperature part on the inlet side. 2. Thermal stress and cracks in the turbine rotor 24 can be prevented.

Figure 4 shows the cooling characteristics of the turbine. By implementing the present invention, things that could only be decomposed after the turbine was stopped using conventional natural cooling can now be decomposed in about two days, reducing the shutdown period to three days. It became possible to shorten the

In this case, ``adjust the opening of the vacuum pump so that the temperature drop of the turbine metal follows the same temperature drop rate (approximately 5℃/Hz)'' and ``the difference in elongation is the tendency for rotor short-circuiting.'' Please check the differential extensometer carefully.
It is necessary to thoroughly check that the turning equipment is being operated continuously.

Therefore, by repeating the above operations, it is possible to achieve gentle cooling by applying a sudden temperature difference to each part, thereby preventing cracks and excessive thermal stress. Without causing any difference in elongation,
Cooling is completed when the metal temperature of the casing reaches 150° C. At this point, the operation of the forced cooling device is stopped and one decomposition is performed. In other words, this configuration can achieve this by introducing air into the casing, and cannot at all be achieved by introducing air from the upstream side of the turbine.

Figure 3 shows the details of the gap between the comb teeth of the shaft backing part and the turbine rotor, and the steam inflow to the high-pressure turbine 2 is routed from the low-temperature part to the high-temperature part by the vacuum pump 23, as shown by the mark. .

〔Effect of the invention〕

According to the present invention, a high-pressure turbine can be cooled by installing only a vacuum pump for forcibly feeding air, piping connecting the vacuum pump, and a main valve for disassembling this piping during operation. This can be done in a short time, making it possible to avoid thermal stress and cracks in the casing, turbine rotor, etc., allowing efficient cooling and shortening downtime.

[Brief explanation of drawings]

Fig. 1 is a system M diagram of an embodiment of the present invention, Fig. 2 is a schematic diagram of the air inlet section, Fig. 3 is a detailed view of the
The figure shows the cooling characteristics of the present invention and the conventional cooling characteristic. 1... Cooling air.

Claims (1)

[Claims] 1. During periodic inspection of the high-pressure turbine of a steam turbine for nuclear power generation, or when stopping and disassembling the steam turbine in an emergency, the gap between the turbine rotor and the shaft backing ring comb teeth before and after the high-pressure turbine. In order to exhaust the air forcibly introduced from the high-pressure turbine from inside the high-pressure turbine, connect it to the already installed main steam stop valve seat drain pipe together with a vacuum pump via an air exhaust pipe,
and an off-gas installed to lower the concentration of radiation-contaminated gas in the turbine and safely discharge it to the atmosphere through the air exhaust piping, a low-pressure turbine, a condenser, and an air extractor. A forced cooling system for a steam turbine for nuclear power generation, which is connected to an exhaust pipe, and is led to an off-gas facility and a rare gas hold-up facility, and is then discharged to the atmosphere.