JPH01185492A - Feed water tubing circulating facility in nuclear power plant - Google Patents

Abstract

PURPOSE:To control corrosion by connecting a piece of final stage feed water heater downstream side tubing and a piece of reactor coolant purifying device downstream side tubing by a piece of bypass tubing while a separation valve is provided between a final stage feed water heater and the bypass tubing and circulating purifying system circulating water. CONSTITUTION:A separation valve 9 is provided in the downstream side of a final stage feed water heater 24 while a reactor coolant purifying system 3 and a piece of feed water tubing 4 are connected by a piece of bypass tubing 5. When the valve 9 and a reactor coolant purifying system valve 15 are closed and a bypass tubing inlet valve 6, a bypass tubing outlet valve 7 and a reactor pressure vessel outside separation valve 16 are opened, reactor coolant purifying system circulating water is circulated by a reactor coolant purifying system pump 11 through the tubing 4, 5. Therefore, the water is circulated and stored in the tubing 4 and corrosion from the tubing 4 at the time of plant stop can be controlled.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides equipment that can circulate water within the water supply piping using circulating water from the reactor coolant purification system in order to suppress corrosion of the water supply piping during shutdown of a nuclear power plant. This relates to water supply piping circulation equipment in nuclear power plants equipped with

[Conventional technology]

Conventional nuclear power plants, for example,
There is one described in the 4081 publication. When the plant is stopped, the supply/condensate system 18 is operated as shown in Fig. 2.
The reactor pressure vessel outer isolation valve 16 is closed, and the feed/condensate recirculation valve 23 of the feed/condensate recirculation system 17 is opened. By bypassing the water supply pump 22, the condensate pump 20 operates the condensate desalination device 21. Circulating storage is performed in which the water returns to the condenser 19 via the feed water heater 23. However, the water supply piping 4 after the final stage feed water heater is a connecting piping that connects the reactor building and the turbine building, and when performing circulation operation including this piping, large-diameter piping must reciprocate between the buildings. The problem was that it was necessary. However, no particular consideration was given to the amount of impurities brought into the reactor due to corrosion of this piping and the contribution of secondary system piping to the increase in the dose rate, as it was judged to be sufficiently low compared to the contribution from other systems. Ta. However, in recent years in nuclear power plants, the overall dose rate from Plan 1 has been decreasing due to improvements in sub-system piping materials and the establishment of radiation exposure reduction technology, so the contribution from water supply piping can no longer be ignored. It's coming.

[Problem to be solved by the invention]

In the above conventional nuclear power plant, when the plant is stopped, the piping from the condenser to the final stage feedwater heater is
Corrosion of the supply and condensate system piping is suppressed by storing the water in circulation using supply and condensate circulation piping, or by draining water from the system. However, the piping after the final stage feed water heater does not have circulation piping and cannot be stored in circulation. Also, since there is no drain line, water cannot be drained and stored dry, and water accumulates inside the pipes, causing corrosion. Therefore, rust generated during shutdown at the time of startup of a nuclear power plant is carried into the reactor and becomes radioactive, which poses a problem of increasing the dose rate of secondary system piping.

The purpose of the present invention is to provide a water supply piping circulation system that allows for circulation storage or drained dry storage of piping after the final stage feed water heater, as well as piping upstream of the final stage feed water heater, when a nuclear power plant is shut down. An object of the present invention is to provide a plant that can suppress corrosion of water supply piping when a nuclear power plant is shut down and reduce rust brought in when the nuclear power plant is started up by providing equipment.

[Means to solve the problem]

The above purposes are (a) nuclear reactor, (b) turbine, (C) generator, (d) condenser, condensate purification device to remove impurities in condensate, feed water heater to heat feed water, and nuclear reactor. A feed/condensate system with feed/condensate recirculation piping installed to suppress corrosion of the feed/condensate system during shutdown, and (e) reactor, including a reactor purification system to remove impurities in reactor water. In a nuclear power plant whose main component is a reactor coolant purification system, a bypass piping is provided that connects the final stage feed water heater downstream piping and the reactor coolant purification device downstream piping,
This is achieved by providing an isolation valve between the final stage feed water heater side connection portion of the bypass piping and the final stage feed water heater.

[Effect]

In order to suppress corrosion in the water supply piping when the plant is shut down, the present invention is equipped with piping in which circulating water from the reactor coolant purification system is circulated through the water supply piping. In such cases, the water in the water supply pipe can be drained by the second pipe after circulation, and the water supply pipe can be stored dry.

Next, Figure 3 shows changes in the amount of corrosion due to differences in the environment inside the piping in a nuclear power plant. The amount of corrosion when stored dry, C indicates the amount of corrosion when the inside of the pipe is @ring pipe.

In state A, corrosion progresses rapidly over time. On the other hand, if circulation storage is carried out according to the present invention, corrosion will hardly progress as shown in C.

Also, by draining water and storing it dry, C
It has a sufficient corrosion inhibiting effect compared to the full water condition.

〔Example〕

Embodiment 1 As shown in FIG. 1, an isolation valve 9 is installed downstream of the final stage feed water heater to isolate the feed water pipe 4 from the feed/condensate recirculation system.
The reactor coolant purification system 3 and the water supply pipe 4 are connected to each other by a bypass pipe 5.

The water supply piping 4 after the final stage feed water heater includes a final stage feed water heater downstream isolation valve 9 and a reactor coolant purification system isolation valve 15.
By closing the bypass piping inlet valve 6, bypass piping outlet valve 7, and opening the reactor pressure vessel outer isolation valve 16, the reactor coolant purification system pump 11 drains the reactor coolant purification system circulating water. However, it becomes possible to circulate through the bypass pipe 5 and the water supply pipe 4. According to this embodiment, the inside of the water supply pipe 4 is circulated and stored, making it possible to suppress corrosion from the water supply pipe 4 when the nuclear power plant is shut down.

As a result, it is possible to suppress the amount of impurities brought into the reactor at the time of startup of a nuclear power plant, and to suppress the increase in the dose rate of the secondary system piping due to impurities being activated in the reactor and adhering to the primary system piping. It becomes possible.

Example 2 In this example, after the circulation storage of Example 1 during a long-term shutdown of a nuclear power plant, the water supply piping 4 after the final stage feed water heater is
The dry storage of can be made possible by the following. The bypass pipe 5 of the first embodiment is provided with a bypass pipe drain valve 8 for draining system water, and the water supply pipe 4 is further provided with a water supply pipe vent valve. To drain water from the water supply pipe 4, close the reactor pressure vessel outer isolation valve 16, the final stage feed water heater downstream isolation valve 9, and the bypass pipe inlet valve 6, and close the bypass pipe drain valve 8, bypass line outlet valve 7, and This is possible by opening the water supply pipe vent valve 10. According to this embodiment, the water supply pipe 4 is drained and stored in a dry manner.
Similarly, when starting up a nuclear power plant, the amount of impurities brought into the reactor is suppressed, and the impurities are activated within the reactor and -
It becomes possible to suppress an increase in the dose rate of the secondary system piping due to adhesion to the secondary system piping.

〔Effect of the invention〕

According to the present invention, it is possible to suppress rust generated from water supply piping when a nuclear power plant is shut down, and to suppress import of impurities into the reactor when the nuclear power plant is started.

This has the effect of reducing the a content ratio of the primary system piping due to activation of impurities within the reactor. For example, if the water supply piping is kept full of water as usual during a three-month plant shutdown,
Approximately 8 kg of corrosion occurs. When this is stored in circulation according to the present invention, about 0.1 kgL does not corrode. Furthermore, even when stored without water, the amount of corrosion is 0.6 kg, which is sufficiently small compared to conventional products.

Since the amount of corrosion from the feedwater piping is equivalent to about one-third of the amount of impurities brought into the feedwater, if the amount of corrosion from the piping after the final stage feedwater heater is reduced by this invention, it will be possible to reduce the amount of corrosion to the reactor. The amount of impurities brought in can be reduced to two-thirds.

Furthermore, considering that the dose rate of the secondary system piping is proportional to the amount of impurities brought into the reactor, if the amount of corrosion from the piping after the final stage feedwater heater is reduced by the present invention, the radiation dose rate of the secondary system piping will be reduced. The a content rate can also be reduced to about two-thirds.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a nuclear power plant according to the present invention, FIG. 2 is a schematic diagram of a conventional plant, and FIG. 3 is a graph showing changes in the amount of corrosion under various conditions. 1... Nuclear reactor, 3... Reactor coolant purification system piping, 5
...Bypass piping, 6...Inlet valve of bypass piping,
7... Outlet valve of bypass piping, 8... Drain valve of bypass piping, 9... Final stage feed water heater downstream isolation valve, 1
3... Reactor coolant purification system filtration salt theory device, 19...
Condenser, 24... Feed water heater. Article 1 Kuchigyu 3m Gin (Nitsu)

Claims (1)

[Claims] 1. (a) nuclear reactor, (b) turbine, (c) generator, (
d) condenser, condensate purification device for removing impurities in condensate;
A feedwater/condensate system that has a feedwater heater that heats the feedwater and feed/condensate recirculation piping installed to suppress corrosion of the feedwater/condensate system during reactor shutdown, and (e) reactor and reactor water. In a nuclear power plant whose main component is a reactor coolant purification system including a reactor purification device that removes impurities,
A bypass piping is provided that connects the downstream piping of the final stage feedwater heater and the downstream piping of the reactor coolant purification device, and a connecting portion of the bypass piping on the final stage feedwater heater side and the final stage feedwater heater are provided. Water supply piping circulation equipment in a nuclear power plant, characterized by having an isolation valve installed between them. 2, (a) nuclear reactor, (b) turbine, (c) generator, (
d) Condenser, a condensate purification device that removes impurities in condensate. A feedwater/condensate system that has a feedwater heater that heats the feedwater and feed/condensate recirculation piping installed to suppress corrosion of the feedwater/condensate system during reactor shutdown, and (e) reactor and reactor water. In a nuclear power plant whose main component is a reactor coolant purification system including a reactor purification device that removes impurities,
A bypass piping is provided that connects the downstream piping of the final stage feedwater heater and the downstream piping of the reactor coolant purification device, and a connecting portion of the bypass piping on the final stage feedwater heater side and the final stage feedwater heater are provided. A water supply piping circulation system in a nuclear power plant, characterized in that an isolation valve is provided between the bypass piping and a water drain piping is provided in a part of the bypass piping.