JPH0319885B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method and an apparatus for shutting off steam supplied to a low pressure turbine in a nuclear power plant.

[Background of the invention]

The valve means interposed between the high-pressure turbine and the low-pressure turbine of a nuclear power plant is provided to cut off the supplied steam in an emergency, and is generally composed of two valves arranged in series. It is called an intermediate valve.

The above combination intermediate valve for a low pressure steam turbine is a large and heavy member disposed near the inlet of the low pressure steam turbine.

A combination intermediate valve in a nuclear power plant is
Conventionally, valves have generally been installed on the operating floor, requiring a large installation space, and the construction cost is high because this large member (combined intermediate valve) must be shielded.

Figure 2 shows the basic configuration of a boiling water reactor power plant (BWR plant).

The main steam generated in the reactor 1 is transferred to the main steam pipe 20,
It is guided to the high pressure turbine 6 by a turbine lead pipe 21. Exhaust gas from the high pressure turbine 6 is guided to the low pressure turbine 9 by a cross-around pipe 22.
Further, a moisture separator 7 is installed along the route of the cross-around piping 22, and by removing moisture from the steam, the efficiency of the low-pressure turbine 9 is improved and erosion due to moisture is prevented.

As mentioned above, steam generated in the reactor 1 is supplied to the steam turbines 6 and 9, but in the event of plant startup, shutdown, or emergency, it is guided to the turbine bypass pipe 23, and after depressurizing excess steam, it is dumped to the condenser 10. be done.

A combination intermediate valve 8 is provided at the inlet of the low air turbine 9. Conventionally, as shown in FIG.
Two types of valves were assembled in one casing. Although these valves shared a common casing, they used completely different functions and control methods.

The intermediate steam stop valve 24 and the intercept valve 2
The purpose of installing the turbine 5 is to block the steam during load or interruption and protect the low pressure turbine 9 from overspeeding. By placing the combination intermediate valve 8 very close to the low pressure turbine 9 as shown in FIG. 3, the amount of steam between the combination intermediate valve 8 and the casing of the low pressure turbine 9 is restricted to a minimum. , the uncontrolled steam energy that overspeeds the low-pressure turbine 9 during load cut-off or emergency cut-off is reduced.

The purpose of the intercept valve 25 is to prevent the large volume of steam stored in the cross-around pipe 22 from overspeeding the low-pressure turbine 9 in the event of an emergency shutdown, resulting in a dangerous situation. Further, the intercept valve 25 can be opened to the maximum pressure of the cross-around piping 22, and can also perform speed regulating control after load cutoff. In this way, when the load cutoff intercept valve 25 is fully closed, the flow of steam to the low pressure turbine 9 is stopped, but since the leaked steam is sufficiently small compared to the no load steam amount, the low pressure turbine is not accelerated. Also, the deceleration of the low-pressure turbine 9 is not hindered after the load is cut off. Further, the intercept valve 25 is an emergency device (not shown).
It has a structure that can be tripped by

The intermediate steam stop valve 24 is fully closed when the emergency device is reset, and remains fully open during normal operation.
The emergency governor (not shown) is actuated or a master trip (not shown) is actuated to quickly close the valve. The intermediate steam stop valve 24 is provided as a second stage protection device (backup protection device) against steam energy stored in the cross-around piping 22 due to the inoperation of the intercept valve 25 or failure of the normal speed governor. ing. However, the intermediate steam stop valve 24
It is also fully closed in the event of an emergency or disconnection device activation, either due to a normal shutdown or an electrical trip.

As mentioned above, the combination intermediate valve 8 is a very large valve in which two types of valves, namely the intercept valve 25 and the intermediate steam stop valve 24 are combined.
As shown in FIG. 3, a large installation space is required. Further, since the combination intermediate valve 8 is installed on the operating floor, a large-sized shield is required.

[Purpose of the invention]

The present invention was made in view of the above circumstances, and
A method capable of shutting off steam supplied to a low-pressure steam turbine in a nuclear power plant with a small and lightweight member, and requiring only a small shielding structure, and a shutoff device suitable for carrying out the above method. This is what we are trying to provide.

[Summary of the invention]

In order to achieve the above object, the shutoff method of the present invention is a method of shutting off steam supplied to a low pressure turbine of a nuclear power plant using a combination intermediate valve.
The cross-around pipe of the low-pressure turbine is led to the lower side of the operating floor as a vertical pipe near the inlet of the low-pressure turbine, and two butterfly valves are installed in a portion of the cross-around pipe that includes at least either a horizontal portion or a vertical portion. is arranged to block steam flowing into the low-pressure turbine.

Further, the steam cutoff device of the present invention, which has been created to be suitable for carrying out the above-mentioned method, uses a combination intermediate valve for a low-pressure turbine of a nuclear power plant, which is composed of an intermediate steam stop valve and an intercept valve, to supply steam. In this shutoff device, the above-mentioned intermediate steam stop valve and intercept valve are each constituted by a butterfly valve, and the cross-around pipe in which the combined intermediate valve is installed is installed under the operating bed with each vertical pipe near the low-pressure turbine inlet. The invention is characterized in that the two butterfly valves are provided in at least one of a vertical piping section and a horizontal piping section of the cross-around pipe.

[Embodiments of the invention]

FIG. 1 shows an embodiment of the apparatus of the present invention configured to carry out the method of the present invention. This example is
This is an example of the conventional device shown in FIG. 2 improved by applying the present invention.

The difference from FIG. 2 (conventional example) is that instead of the combination intermediate valve (conventional type) 8, two butterfly valves 16a and 16b are arranged in series, and the combination intermediate valve according to the present invention is constructed. 16 was constructed.

FIG. 4 shows the above two butterfly valves 16a, 1.
6b is an explanatory diagram schematically depicting it. These 2
Of the butterfly valves 16a and 16b, the steam inlet side 16a of the low pressure turbine 9 functions as an intercept valve, and the other butterfly valve 16b functions as an intermediate steam stop valve. Now, FIG. 4 shows a case where the combination intermediate valve 8 (FIG. 3) is installed at the same position.

FIG. 5 shows the arrangement of the butterfly valve 16. The cross-around pipe 22 is connected to the low-pressure turbine 9, and the cross-around pipe 22 coming out of the casing of the low-pressure turbine 9 immediately becomes a vertical pipe 22a, penetrates the turbine floor 18, and is disposed below the operating floor. . In this example, the butterfly valve 16 is installed in the middle of the cross-around piping 22 arranged below the operating floor. Here, two butterfly valves 16a and 16b are arranged across the curved part of the pipe, but they can also be arranged in the straight pipe part 22a. Furthermore, the safety valve 19 shown in this figure is provided to protect the moisture separator and piping from a pressure increase that occurs in the low-pressure turbine inlet piping when the butterfly valve suddenly closes.

In this embodiment, the cross-around piping 22 at the inlet of the low-pressure turbine 9 is immediately a vertical pipe, and no valve is installed above the turbine floor 18, which is the operating floor. The space for the piping system is
Compared to the conventional combination intermediate valve 8, it can be significantly reduced by 50% or less.

Therefore, the cross-around piping 22 on the driving floor needs to be shielded, but as described above, the shielded space and the amount of shielded material can be reduced to 50% or less in proportion to the reduction of the space.

Next, with reference to FIGS. 8 and 9, a state in which the shielding of the end and end combination intermediate valve portion can be done on a small scale by applying the present invention will be explained.

FIG. 8 shows the tight space 26 around the conventionally installed combination intermediate valve 8.
The figure shows the shielded space 26' of the butterfly valve 16 according to the invention when installed under the operating floor.

Comparing FIG. 8 and FIG. 9, the following effects can be expected. First, as mentioned above, by reducing the shielded space above the driving floor to less than 50%, conversely,
Free space above the driving bed increases significantly.

One of the ripple effects of these efforts is a significant improvement in the ease of disassembling and inspecting valves. Conventionally, when disassembling and inspecting the combination intermediate valve 8, it was necessary to disassemble the shielding structure around it, but by installing the butterfly valve under the operating floor, the shielding structure 26' can be removed. The valve can be disassembled and inspected without being disassembled, and the number of man-hours required for disassembling and inspecting the valve can be reduced. Further, since there is no need to disassemble the shielding structure 26, radiation is not scattered onto the operating floor, and sufficient safety in radiation management can be achieved. Further, the possibility that the shielded space becomes an obstacle when operating a crane or the like on the operating floor is sufficiently reduced, and maintenance and inspection on the operating floor can be improved.

The weight reduction effect of the combined intermediate valve portion in this example will be specifically explained. The conventional combination intermediate valve 8 was a heavy member weighing about 20 tons, but the butterfly valve 16a in this example,
16b has a total weight of about 8 tons, and the weight reduction rate of the device is more than 50%.

Furthermore, since the conventional combination intermediate valve 8 is installed at the low-pressure turbine steam inlet, the support structure for the combination intermediate valve had to be removed from the operating floor, which is the upper part of the turbine building. Ba,
Since two butterfly valves are installed under the operating floor, it is also possible to remove the support structure from one lower floor. This reduces the load applied to the operating floor of the turbine building, making it possible to rationalize the design of the turbine building frame.

In this embodiment, two butterfly valves 1
Although the butterfly valves 6a and 16b are installed in the horizontal piping section below the operating floor, one butterfly valve 16b may be installed in the vertical piping section, as shown in FIG.

In this case as well, since the length of the cross-around piping 22 installed on the driving floor is the same as in FIG. 5, exactly the same effect as described above can be expected.

In addition, depending on the surrounding situation of the cross-around pipe 22 under the driving floor, a butterfly valve 16a may be installed under the driving floor.
If it is not possible to install both butterfly valves 16b, it is permissible to install not only one butterfly valve 16b on the driving floor, but also to place both of them on the driving floor, as shown in FIG. However, in this case, although it can be expected that the arrangement space will be reduced and the amount of shielded objects will be reduced compared to the intermediate combination valve 8, the expected effects will be somewhat smaller than those of the embodiments described above and FIGS. 5 and 6.

〔Effect of the invention〕

As detailed above, according to the method of the present invention,
Steam supplied to a low-pressure steam turbine in a nuclear power plant can be shut off with a small and lightweight member, and the shutoff structure can be made smaller and lighter.

Further, according to the apparatus of the present invention, the above-described method of the invention can be easily implemented and its effects can be fully exhibited.

[Brief explanation of the drawing]

FIG. 1 is a steam system diagram of a nuclear power plant showing an embodiment of the apparatus of the present invention. FIG. 2 is a steam system diagram of a conventional nuclear power plant, and FIG. 3 is a sectional view of a conventional combined intermediate valve. FIG. 4 is a schematic diagram of the combination intermediate valve according to the present invention.
5 to 7 are partially cutaway perspective views showing one embodiment of the present invention, respectively. 8 and 9 are explanatory diagrams of the shielding means, in which FIG. 8 is a perspective view of a conventional technique, and FIG. 9 is a perspective view of one embodiment of the present invention. 1... Nuclear reactor, 6... High pressure turbine, 7... Moisture separator, 8... Conventional combination intermediate valve, 9...
Low pressure turbine, 10... Condenser, 11... Generator, 16... Combination intermediate valve according to the present invention, 16
a, 16b... Butterfly valve, 17... TIG mount, 18... Turbine floor, 19... Relief valve, 22
. . . Cross-around piping, 24 . . . Intermediate steam stop valve, 25 . . . Intercept valve, 26 . . .

Claims (1)

[Claims] 1. A method for shutting off steam supplied to a low-pressure turbine of a nuclear power plant using a combination intermediate valve,
The cross-around pipe of the low-pressure turbine is led to the lower side of the operating floor as a vertical pipe near the inlet of the low-pressure turbine, and two butterfly valves are installed in a portion of the cross-around pipe that includes at least either a horizontal portion or a vertical portion. A method for cutting off steam supplied to a low-pressure steam turbine, the method comprising: arranging the above to cut off steam flowing into the low-pressure turbine. 2 At least one of the two butterfly valves mentioned above.
2. A method for shutting off steam supplied to a low-pressure steam turbine according to claim 1, wherein the switch is provided on an operating bed near an inlet of the low-pressure turbine. 3. The number of butterfly valves provided on the operating floor is one, and the other butterfly valve is provided in the horizontal or vertical portion of the portion where the cross-around pipe is piped under the operating floor. A method for shutting off steam supplied to a low-pressure steam turbine according to claim 2. 4. In a supply steam cutoff device using a combination intermediate valve for a low-pressure turbine in a nuclear power plant, consisting of an intermediate steam stop valve and an intercept valve, each of the intermediate steam stop valve and intercept valve is configured with a butterfly valve. At the same time, the cross-around pipe in which the combination intermediate valve is to be provided leads the vicinity of the low-pressure turbine inlet to the lower side of the operating floor as a vertical pipe, and the two butterfly valves are connected to the vertical piping part and the horizontal piping part of the cross-around pipe. 1. A low-pressure steam turbine supply steam cutoff device, characterized in that the device is provided in at least one portion of the low-pressure steam turbine.