JPH036324B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a cross-around piping system for a nuclear power plant, and particularly relates to the protection of a cross-around piping safety valve.

[Background of the invention]

Figure 4 shows the basic configuration of a boiling water reactor (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 reheater 7 is installed in the middle of the cross-around piping 22 to remove moisture from the steam to improve the efficiency of the low-pressure turbine 9 and prevent piping corrosion due to moisture. In the figure, 2, 3, 4, 5 are valves, 10 is a condenser, 1
2, 13, and 15 are pumps, and 14 is a feed water heater.

Steam generated in the nuclear reactor 1 is normally supplied to the steam turbines 6 and 9, but is guided to the turbine bypass pipe 23 at the time of plant startup, shutdown, or emergency.

Two butterfly valves 8A and 8B are provided at the inlet of the low pressure turbine 9. 8A serves as an intermediate steam stop valve and 8B serves as an intercept valve. The purpose of installing the two butterfly valves 8A and 8B is to block the steam during load or disconnection and to protect the low pressure turbine 9 from overspeed. Two butterfly valves 8A and 8B are placed very close to the low pressure turbine 9 and limit the amount of steam between these valves and the casing of the low pressure turbine 9 to a minimum. That is, the uncontrolled steam energy that causes the low-pressure turbine 9 to overspeed during load interruptions or emergency interruptions is reduced.

The role of the intercept valve 8B is to prevent the large volume of steam stored in the cross-around pipe 22 from causing the low-pressure turbine 9 to speed up and fall into a dangerous situation. This valve can be opened to the maximum pressure of the cross-around piping 22, and can also perform speed regulating control after a load is applied or the valve is disconnected.
In this way, when one butterfly valve 8B is fully closed as an intercept valve when the load is interrupted, the flow of steam to the low pressure turbine 9 is stopped. Furthermore, since the leaked steam is sufficiently small compared to the no-load steam amount, it does not accelerate the low-pressure turbine or prevent the low-pressure turbine 9 from decelerating after the load is interrupted. Valve 8B can be tripped by an emergency device.

On the other hand, the butterfly valve 8 as an intermediate steam stop valve
A is fully closed when the emergency device is reset, remains fully open during normal operation, and is suddenly closed when the emergency governor is activated or the master trip is activated. The valve 8A is provided as a second stage protection device (backup protection device) against steam energy stored in the cross-around pipe 22 due to the inoperation of the intercept valve 8B or failure of the normal speed governor. However, valve 8A is also fully closed in the event of an emergency or disconnection device activation, either due to a normal shutdown or an electrical trip.

Moisture separation reheater 7 and piping 22 are affected by the pressure increase that occurs when two butterfly valves 8A and 8B installed in the inlet piping of low-pressure turbine 9 suddenly close.
A cross-around piping safety valve 11 is provided to protect the condenser 1 through the safety valve exhaust pipe 16.
It is designed to exhaust to 0. FIGS. 5 and 6 show how this valve is installed in the middle of the cross-around piping 22.

The head portion of the safety valve 11 penetrates the operating floor 18,
It ends up on the driving floor 18. For this reason, it was necessary to install a shield 24 on the driving floor. Note that 19 is the end of the rising portion of the cross-around piping 22.

To lower the level of such cross-around piping safety valve 11, cross-around piping 22
In other words, the installation level or nozzle level of the moisture separator reheater 7 to be connected may be lowered.

However, as shown by the dotted line in FIG. 7, it is necessary to remove the tube for inspection of the feed water heater 14 in case of emergency and install the moisture separator reheater 7 so as not to encroach on the space. Furthermore, considering the space for installing other equipment in the turbine building, it is impossible to lower the level of the moisture separator reheater 7 itself.

Furthermore, the cross-around piping 22 must be connected from the top of the moisture separator reheater 7 for the following reason. As shown in FIG. 8, the heated steam coming out of the moisture separator reheater 7 is heated by the moisture separator reheater 7 and moves upward. Therefore, the cross-around piping 22 must be taken out from the upper side of the moisture separator reheater 7. For this reason, the sixth
It is not possible to lower the level of the cross-around piping 22 than shown in the figure.

Furthermore, in FIG. 6, it is also possible to lower only the cross-around piping at the portion where the safety valve 11 is installed. However, this is not preferable because not only does a low point occur in the cross-around piping 22, but also the space for drawing out the tube of the feed water heater 15 is invaded as described above.

In short, the planning limitations for cross-around piping include limiting the installation level of the moisture separator reheater and the outlet nozzle level to the piping, avoiding the beam under the operating floor, and not encroaching on the space for drawing out the tube of the low-pressure feedwater heater. , etc., and the level of cross-around piping was determined, so the level of safety valves installed in cross-around piping was also determined.

In this conventional safety valve arrangement method,
The head of the safety valve penetrated through the operating floor and was exposed above the operating floor, so a safety valve shield was installed above the operating floor just for that purpose. Therefore, when disassembling and inspecting the safety valve, it was necessary to disassemble the shield, which required a lot of man-hours. In addition, because there are protective structures on the operating floor and when the crane is operated, it is necessary to take sufficient care to avoid damage when operating the crane, which is inconvenient and difficult. Ta.

[Purpose of the invention]

The object of the present invention is to safely replace the safety valves that were conventionally installed in the middle of cross-around piping, with their heads protruding onto the operating floor and requiring shielding, which obstructed work on the operating floor. The objective is to provide a cross-around piping system located under the operating floor.

[Summary of the invention]

The feature of the present invention is that the cross-around piping safety valve is connected to the moisture separator reheater as shown in FIG.
It is located under the operating floor of the turbine building.
When the arrangement of the present invention is adopted, the conventional safety valve head portion penetrates through the operating floor and protrudes above the operating floor, thereby eliminating the need for any protection. As a result, the free space on the operating floor of the turbine building has been expanded,
In addition to improving the workability of maintenance and inspection on the operating floor, the space and structures on the operating floor are reduced, the number of man-hours required for disassembling and inspecting safety valves is reduced, and sufficient radiation control can be achieved to improve safety. becomes higher.

[Embodiments of the invention]

1 and 2 show an embodiment in which a safety valve 11 is installed in the moisture separator reheater 7. FIG. A safety valve 11 is installed in the body of the moisture separator reheater 7, from which a safety valve exhaust pipe 16 is connected to the condenser 10.
When the safety valve 11 operates, steam escapes to the exhaust pipe 16 to protect the body of the moisture separator and reheater 7, and also to release steam from the moisture separator and reheater 7 to the two butterfly valves 8.
It also protects the cross-around piping 22 leading up to.

There is sufficient space above the moisture separator reheater 7 to install the safety valve 11.
There is no contact with the lower side of 8.

In this embodiment, the safety valve 11 is installed directly on the moisture separator reheater 7, so the safety valve 11 does not penetrate through the operating floor 18 and the head portion does not come out above the operating floor 18, which is different from conventional operation. The space occupied by the safety valve 11 on the floor 18 is no longer needed at all.

Therefore, conventionally, the safety valve 11 required a shield, but in this embodiment, no special shield is required at all.

In the conventional safety valve arrangement, it was necessary to shield the head portion of the safety valve 11 with a shield 24, as shown in FIGS. 5 and 6. Therefore, when disassembling and inspecting the safety valve 11, it was necessary to disassemble the shield 24, but with the arrangement of the safety valve 11 in this embodiment, this is not necessary, and disassembly and inspection can be carried out by simply pulling up the hatch 25. Put it to work.

The conventional method of disassembling the shield 24 and then disassembling and inspecting the safety valve 11 not only takes a lot of man-hours, but also involves a large number of disassembly steps, which increases the potential for danger in the work, but the safety valve according to the present invention In the arrangement No. 11, it is only necessary to pull up the hatch 25, so that the number of work steps and the danger potential of the work can be sufficiently reduced.

In addition, with the conventional safety valve arrangement, there was a sag on the operating floor, so when operating a crane, etc., it was necessary to be careful to avoid the sag. However, with the safety valve arrangement of the present invention, Since it is a hatch, there will be no obstruction when operating a crane or the like on the operating floor, and maintenance and inspection work on the operating floor will be much easier.

〔Effect of the invention〕

According to the present invention, the cross-around piping safety valve does not penetrate through the operating floor and is disposed below the operating floor, resulting in the following effects.

1. There is no need to shield the cross-around piping safety valve on the operating floor, reducing the amount of material to be shielded.

2. The cross-around piping safety valve can be disassembled and inspected simply by raising the hatch on the operating floor, reducing the number of work hours and the potential for dangerous work.

3. A cross-around piping safety valve is placed below the operating floor, which increases the free space above the operating floor, eliminates obstacles when operating cranes, etc., and improves the efficiency of maintenance and inspection work on the operating floor.

[Brief explanation of the drawing]

Fig. 1 is a plan view of an embodiment of a cross-around piping system according to the present invention, Fig. 2 is a partial side sectional view, Fig. 3 is a basic system configuration diagram of a BWR plant adopting the present invention, and Fig. 4 is a plan view of an embodiment of a cross-around piping system according to the present invention. The basic system configuration diagram of a conventional BWR plant, Fig. 5 is a plan view of a conventional cross-around piping system, Fig. 6 is a partial side sectional view, Fig. 7 is a plan view of the operation under-floor arrangement of the BWR plant turbine building, and Fig. 8 is a plan view of a conventional cross-around piping system. The figure shows the basic structure of a moisture separation reheater. 1... Nuclear reactor, 6... High pressure turbine, 7... Moisture separation reheater, 8A, 8B... Butterfly valve, 9
...Low pressure turbine, 10 ... Condenser, 11 ... Cross-around piping safety valve, 14 ... Feed water heater, 16 ... Safety valve exhaust pipe, 18 ... Operating floor, 1
9...Piping rising section, 20...Main steam pipe, 21...Turbine lead pipe, 22...Cross-around piping, 23...Turbine bypass pipe,
24...Safety valve, 25...Hatsuchi.

Claims (1)

[Claims] 1. Cross-around piping that guides the exhaust gas from the high-pressure turbine of Atomic Kaplaton to the low-pressure turbine placed on the operating floor, and a moisture pipe placed in the middle of this piping under the operating floor to remove moisture from the steam. A separation reheater, an intermediate steam stop valve and an intercept valve that are installed downstream from the separation reheater near the low-pressure turbine inlet to cut off steam to the low-pressure turbine in the event of a load interruption or an emergency interruption; A cross-around consisting of a cross-around piping safety valve to protect the moisture separation reheater and cross-around piping from the pressure increase when the valve closes suddenly, and a safety valve exhaust pipe that releases the exhaust from this valve to the condenser. A cross-around piping system characterized in that a cross-around piping safety valve is attached to a moisture separation reheater, and the head of the safety valve is located below the operating floor. 2. The cross-around piping system according to claim 1, characterized in that a hatch is provided on the operating floor directly above the head of the cross-around piping safety valve, and maintenance and inspection of the safety valve is performed from this hatch.