JP4575278B2 - Feed water heater drain pump up system - Google Patents

Description

  The present invention relates to a feed water heater drain pump-up system of a nuclear power plant.

  One means for improving the plant efficiency of a nuclear power plant is a feed water heater drain pump up system. During normal operation, this system stores in the drain tank the hot drain that is generated when the condensate in the condensate pipe is heated by the feed water heater, and the drain in the drain tank is connected to the condensate pipe. It is fed into the condensate pipe by a drain pump through the pipe. The feed water heater drain pump-up system improves the plant efficiency of a nuclear power plant by supplying high-temperature drain into the condensate pipe and using it for increasing the condensate temperature (for example, Patent Documents). 1).

JP 11-344595 A

  By the way, the above-mentioned feed water heater drain pump up system stops the function by stopping the drain pump in the case of load interruption, etc., so that the high temperature drain remains in the drain pipe downstream of the drain pump. become. In addition, the feed water heater uses the steam supplied from the turbine during normal operation to heat the condensate. However, if the supply of steam from the turbine is stopped due to load interruption or the like, the heating capacity is weakened and the The temperature of the condensate staying in the water pipe gradually decreases with time. In this way, the condensate in the condensate pipe becomes relatively cooler than the drain in the drain pipe.

  In such a case, for example, if the drain pipe is connected from below the condensate pipe at the connection point between the condensate pipe and the drain pipe, the condensate is contained in the drain pipe where the drain is retained due to a difference in specific gravity or the like. The condensate at low temperature that has stayed in the pipe may flow in. Condensate flowing into the drain pipe in this manner causes a significant water temperature difference (about 50 to 100 ° C.) in the drain pipe. This temperature difference causes the drain piping to expand and contract due to thermal deformation, and the influence may extend to surrounding equipment.

  An object of the present invention is to provide a drain pump-up system for a nuclear power plant that can suppress damage to drain piping that occurs when steam is no longer supplied to a feed water heater due to load interruption or the like.

(1) In order to achieve the above object, the present invention heats the condensate conduit for circulating the condensate supplied from the condenser to the reactor, and the condensate in the condensate conduit with steam. A feed water heater, a drain line for circulating the drain generated in the feed water heater, a connection part where the drain line connects to the condensate pipe, and a drain in the drain pipe to the condensate pipe A drain pump that pumps toward the passage, and is a flow path that goes down toward the downstream side in the drain circulation direction at at least one point in the route of the drain pipe line from the outlet of the drain pump to the connection portion. The condensate staying in the condensate pipe is prevented from flowing into the drain pipe when the temperature of the condensate in the condensate pipe decreases due to the stop of the steam supply to the feed water heater. Suppose that it has a downward slope part for doing.

  (2) The above (1) preferably further includes a low-pressure feed water heater to which steam is supplied from a low-pressure turbine, and the feed water heater is a high-pressure feed water heater to which steam is supplied from a high-pressure turbine, and the connection The section is located upstream of the high-pressure feed water heater and downstream of the low-pressure feed water heater.

  (3) The above (1) preferably further includes a high-pressure feed water heater to which steam is supplied from a high-pressure turbine, and the feed water heater is a low-pressure feed water heater to which steam is supplied from a low-pressure turbine, and the connection The section is located upstream of the low-pressure feed water heater and downstream of the condenser.

  According to the present invention, it is possible to prevent the drain pipe from being damaged by preventing the inflow of condensate even at the time of load interruption or the like, so that stable operation of the nuclear power plant can be ensured.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic view of a nuclear power plant equipped with a feed water heater drain pump-up system of the present invention.

  A nuclear power plant shown in FIG. 1 circulates a boiling water reactor 1 that generates steam, a high-pressure turbine 2 that is supplied with steam generated in the reactor 1, and steam extracted from the high-pressure turbine 2. Steam pipes 4a and 4b, a low pressure turbine 5 to which steam after being supplied to the high pressure turbine 2 is supplied, steam pipes 7a to 7d for circulating the steam extracted from the low pressure turbine 5, and a low pressure A condenser 8 for condensing steam extracted from the turbine 5 and the like; a condensate pipe 9 for circulating the condensate in the condenser 8 to the reactor 1; and a condensate in the condensate pipe 9 Low pressure condensate pump 10, high pressure condensate pump 11, and feed water pump 12 for pumping water to the reactor 1 and low pressure feed water for heating the condensate in the condensate pipe 9 by steam from the steam pipes 7a to 7d Heaters 6a-6d and steam pipes 4a, 4 High pressure feed water heaters 3a, 3b for heating the condensate in the condensate pipe 9 with steam from the high pressure feed water heaters for supplying the drain generated in the high pressure feed water heaters 3a, 3b to the condensate pipe 9 A drain pump up system (hereinafter referred to as an HPDPU system) 13 and a connection portion 17 where the drain from the HPDPU system 13 joins the condensate in the condensate pipe 9 are provided.

  In the following description, for convenience of explanation, the drain flow path is referred to as “drain piping” as described above. In other words, the term “drain pipe” used here does not indicate the pipe itself formed by parts such as pipes and joints, but the drain distribution path formed by configuring these various pipe parts ( Let's show the drain line). The same applies to the condensate pipe 9 and the condensate distribution path is the condensate pipe line.

  The high-pressure feed water heaters 3a and 3b include a heating pipe through which condensate flows, and the steam (heating steam) extracted from the high-pressure turbine 2 is guided to the outside of the heating pipe via the steam pipes 4a and 4b. Yes. In the high-pressure feed water heaters 3a and 3b, the heating steam contacts the heating pipe and exchanges heat to indirectly heat the condensed water flowing through the heating pipe. As described above, the high-pressure feed water heaters 3 a and 3 b improve the thermal efficiency of the plant by heating in advance before supplying the condensate to the nuclear reactor 1. Further, the heated steam that has heated the condensate in the high-pressure feed water heaters 3a and 3b is condensed and drained after heat exchange, and accumulates in the high-pressure feed water heaters 3a and 3b.

  Moreover, since it overlaps, detailed description is abbreviate | omitted, but the low-pressure feed water heaters 6a-6d are also heated by the steam extracted from the low-pressure turbine 5 through the steam pipes 7a-7d, similarly to the high-pressure feed water heaters 3a, 3b. Condensate is heated and drainage generated at that time is stored.

  The HPDPU system 13 includes a high-pressure drain tank 14 that collects the drain generated in the high-pressure feed water heaters 3 a and 3 b, a drain pipe 15 for circulating the drain, and the high-pressure drain tank 14 through the drain pipe 15. And a high-pressure drain pump 16 for pumping the drain. A drain pipe 15 is connected to the high-pressure feed water heaters 3a and 3b, and a high-pressure drain tank 14 is connected to the downstream side in the drain circulation direction. The outlet of the high-pressure drain tank 14 is connected to the inlet of the high-pressure drain pump 16 via the drain pipe 15. The outlet of the high pressure drain pump 16 is connected to the condensate pipe 9 at the connection portion 17 via the drain pipe 15, and the drain generated in the high pressure feed water heaters 3 a and 3 b is recovered in the condensate pipe 9. The water is supplied to the nuclear reactor 1 together with water.

  A condenser pipe 9 is connected to the condenser 8. A low pressure condensate pump 10 and a high pressure condensate pump 11 are connected to the condensate pipe 9 in order from the upstream side in the condensate flow direction. A low-pressure feed water heater 6a is connected to the downstream side of the high-pressure condensate pump 6, and low-pressure feed water heaters 6b, 6c, and 6d are connected in order from the upstream. The condensate pipe 9 exiting from the low-pressure feed water heater 6 d is further extended and connected to the feed water pump 12 through a connection portion 17 with the HPDPU system 13. Further, high-pressure feed water heaters 3a and 3b are connected in order to the downstream side of the feed water pump 12, and the reactor 1 is connected to the downstream side.

  In addition, in the connection part 17 in FIG. 1, although the symbol of the exit side of the drain piping 15 is shown connecting to the condensate piping 9 toward the downward direction from the upper direction of the figure, this is shown. Is expressed from the upper side of the condensate pipe 9 (details will be described later with reference to FIG. 2).

  In FIG. 1, two high-pressure feed water heaters 3a and 3b are shown, but the number of high-pressure feed water heaters is not particularly limited to this. Similarly, the number of low-pressure feed water heaters is not limited to the four units 6a to 6d shown in the figure.

Next, the vicinity of the connecting portion 17 will be described in detail with reference to FIG.
FIG. 2 is a cross-sectional view schematically showing the vicinity of the connecting portion 17 in the present embodiment. The same parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted. FIG. 2 is a view showing a cross section in a plane orthogonal to the axial direction (condensate flow direction) of the condensate pipe 9 in the vicinity of the connecting portion 17, and the vertical direction in the figure corresponds to the vertical vertical direction. Further, FIG. 3 and FIG. 4 used in the following description are shown in the same manner.

  As shown in FIG. 2, the drain pipe 15 includes a downward gradient portion 18 that is a flow path that descends in the vertical direction toward the downstream side in the drain circulation direction in the path from the outlet of the high-pressure drain pump 16 to the connection portion 17. Yes. The downstream side of the descending slope portion 18 is joined to the condensate pipe 9 at the connection portion 17 so that during normal operation, drain is supplied from the drain pipe 15 into the condensate pipe 9 by the high-pressure drain pump 16. Yes. The descending slope portion 18 is for preventing the condensate accumulated in the condensate pipe 9 from flowing into the drain pipe 15.

  Next, the operation and action of the nuclear power plant configured as described above will be described.

First, the basic operation during normal operation will be described.
Steam generated by the nuclear reactor 1 is supplied to the high-pressure turbine 2. The supplied steam gives a shaft rotational force to the high-pressure turbine 2, and a generator (not shown) is driven by this shaft rotational force. The steam supplied to the high pressure turbine 2 is also supplied to the low pressure turbine 5. Similarly, this steam gives a shaft rotational force to the low-pressure turbine 5 to drive the generator. Thus, the steam supplied to the turbines 2 and 5 is discharged to the condenser 8, where it is condensed and condensed in the condenser 8 by cooling means such as seawater.

  The condensate in the condenser 8 is pumped by the low-pressure condensate pump 10 toward the reactor 1 through the condensate pipe 9 in order to be supplied again into the reactor 1. The condensate boosted by the low-pressure condensate pump 10 is further boosted by the high-pressure condensate pump 11 and fed to the low-pressure feed water heaters 6a to 6d. The condensate is heated by the heating steam in these low-pressure feed water heaters 6 a to 6 d, further heated by the drain that merges at the connection portion 17, and sent to the high-pressure feed water heaters 3 a and 3 b by the feed water pump 12. Condensate heated by the heating steam in the high-pressure feed water heaters 3a and 3b and further heated is again introduced into the nuclear reactor 1 and boiled to become steam.

  On the other hand, the HPDPU system 13 collects the drain generated in the high-pressure feed water heaters 3 a and 3 b in the high-pressure drain tank 14. Further, the drain collected in the high-pressure drain tank 14 is pressurized by the high-pressure drain pump 16, and the drain having a relatively high temperature (about 20 ° C. higher) than the condensate at the connection portion 17 is disposed above the condensate pipe 9. It is supplied into the pipe 9 so as to flow in.

  Next, the operation and action in the case of load shedding according to the present embodiment will be described.

  When the supply of steam to the high-pressure turbine 2 is stopped due to load interruption or the like, the supply of heating steam to the high-pressure feed water heaters 3a and 3b through the steam pipes 4a and 4b is also stopped. When the supply of steam from the steam pipes 4a and 4b is stopped in this way, the condensate heating capacity of the high-pressure feed water heaters 3a and 3b decreases with the passage of time, for example, a condensate pipe that was about 160 ° C. during normal operation. The temperature of the condensate in 9 gradually decreases to about 40 ° C. over time. At this time, since the operation of the high-pressure drain pump 16 in the HPDPU system 13 is also stopped, the drain existing in the drain pipe 15 on the downstream side of the high-pressure drain pump 16 is maintained in the drain pipe 15 while maintaining a temperature of about 180 ° C. It stays in the state.

  In such a case, for example, if the drain pipe 15 is connected to the condensate pipe 9 from below at the connection portion 17, the temperature difference between the drain in the drain pipe 15 and the condensate in the condensate pipe 9 Due to the specific gravity difference that occurs, condensate having a low specific gravity that has been lowered flows into the drain pipe 15 so as to flow backward. Since drain at about 180 ° C. remains in the drain pipe 15 into which the condensate at low temperature has flowed, a significant temperature difference of about 50 ° C. to 100 ° C. occurs depending on the location in the drain pipe 15. This temperature difference causes the drain pipe 15 to expand and contract to such an extent that it cannot occur during normal operation due to thermal deformation, and the influence may extend to equipment disposed around. For example, drain pipes are thermally deformed, resulting in gaps in the flanges connecting the joints between the pipes, causing water leakage, and fasteners (supports) that support the pipes. May be deformed.

  On the other hand, this embodiment suppresses the occurrence of the above-described problem by providing the descending slope portion 18 in the drain pipe 15. That is, the drain pipe 15 in the present embodiment is provided with a gradient portion 18 that is a flow path that descends in the vertical direction toward the downstream side in the drain circulation direction in the path from the outlet side of the high-pressure drain pump 16 to the connection portion 17. . Thereby, even when the temperature of the condensate in the condensate pipe 9 is lowered due to load interruption or the like and the specific gravity thereof is increased, the drain pipe in which the drain having a relatively low specific gravity as compared with the condensate remains. It is difficult for condensate having a large specific gravity to flow into 15. As a result, it is possible to prevent occurrence of a location that causes a significant temperature difference in the drain pipe 15 on the outlet side of the high-pressure drain pump 16, and therefore, it is possible to suppress the drain pipe from being thermally deformed and damaged by the temperature difference.

Next, the effect of the present invention will be described.
As described above, according to the present invention, the condensate having a low temperature is provided even when the supply of the heating steam to the high-pressure feed water heaters 3a and 3b is stopped due to load interruption or the like by providing the down-gradient portion 18 in the drain pipe 15. Can be prevented from flowing into the drain pipe 15. Accordingly, it is possible to suppress the occurrence of a significant temperature difference in the pipe 15 that causes the drain pipe 15 to be thermally deformed, and it is possible to suppress the drain pipe from being damaged. In addition, since the damage to the drain pipe 15 is suppressed in this way, it is also possible to prevent the equipment around the drain pipe from being affected, so that the nuclear plant can be operated stably even in the case of load interruption or the like. can do.

  In the above description, the HPDPU system 13 that collects the drain in the high-pressure feed water heaters 3a and 3b and joins the condensate has been described, but the present embodiment is the same in the low-pressure feed water heaters 6a to 6d. Of course, the present invention can also be applied to a so-called low-pressure feed water heater drain pump-up system that collects the generated drain and joins it with condensate. That is, after the drain generated in the low-pressure feed water heaters 6a to 6d is collected in the tank, the pressure is increased by the pump, and the drain pipe is connected to the condensate pipe 9 upstream of the low-pressure feed water heater 6a and downstream of the condenser 8. The present invention can also be applied to a system in which a connecting portion to be connected is provided and the drain is joined with condensate through the connecting portion, and the same effect as in the present embodiment can be obtained.

Next, a modification of the present embodiment will be described.
3 and 4 are cross-sectional views schematically showing the vicinity of the connecting portion 17 in a modification of the present embodiment. The same parts as those in the previous figures are denoted by the same reference numerals, and description thereof is omitted.

  In FIG. 3, the drain pipe 15 includes a downward gradient portion 18 </ b> A that is a flow path that goes down toward the downstream side in the drain circulation direction. In FIG. 4, the drain pipe 15 is provided with a downward gradient portion 18 </ b> B that is a horizontal pipe and is a flow path that goes down toward the downstream side in the drain circulation direction.

  In the above-described embodiment, the down slope portion 18 which is a flow path that descends in the vertical direction toward the downstream side in the drain circulation direction is described as an example as a part for preventing the inflow of the low-temperature condensate. It is not limited only to this downward slope part 18 that can become a prevention part. For example, as shown in FIG. 3, when the drain pipe 15 is disposed horizontally with respect to the descending slope portion 18A that descends obliquely toward the downstream side in the drain circulation direction or the condensate pipe 9 as shown in FIG. However, the same effect as that of the present embodiment can be obtained by providing the downward gradient portion 18B, which is a flow path that goes down toward the downstream side in the drain circulation direction.

  2 to 4 show the case where the descending slope portions 18, 18 </ b> A, 18 </ b> B are provided at the outlet portion of the drain pipe 15 adjacent to the connection portion 17, the installation location is not limited to this. That is, in the path of the drain pipe 15 from the outlet side of the high-pressure drain pump 16 to the connection part 17, the flow of the low-temperature condensate is allowed to flow if at least one of the down-gradient parts is provided in the path. In such a case, the same effect as in the present embodiment can be obtained.

  In addition, it cannot be overemphasized that the specification change regarding the modified example of the above-mentioned downward slope part and its installation location is applicable also in the said low-pressure feed water heater drain pump up system.

It is a schematic diagram of a nuclear power plant provided with an embodiment of the invention. It is sectional drawing which showed typically the connection part vicinity of the condensate piping and drain piping in embodiment of this invention. It is sectional drawing which showed typically the connection part vicinity of the condensate piping and drain piping in the 1st modification of embodiment of this invention. It is sectional drawing which showed typically the connection part vicinity of the condensate piping and drain piping in the 2nd modification of embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1: Reactor 2: High pressure turbine 3a-b: High pressure feed water heater 4a-b: Steam pipe 5: Low pressure turbine 6a-d: Low pressure feed water heater 7a-d: Steam pipe 8: Condenser 9: Condensate piping DESCRIPTION OF SYMBOLS 10: Low pressure condensate pump 11: High pressure condensate pump 12: Feed water pump 13: High pressure feed water heater drain pump up system 14: High pressure drain tank 15: Drain piping 16: High pressure drain pump 17: Connection part 18: Down slope part 18A ~ B: Down slope part

Claims (3)

A condensate pipe for distributing the condensate supplied from the condenser to the reactor;
A feed water heater for heating the condensate in the condensate line with steam;
A drain line for circulating the drain generated in the feed water heater;
A connecting portion for connecting the drain line to the condensate line;
A drain pump for pumping the drain in the drain line toward the condensate line;
At least one point in the path of the drain pipe line from the drain pump outlet to the connecting portion, the flow path goes down toward the downstream side in the drain circulation direction , and the steam supply to the feed water heater is stopped by stopping the supply of steam. It has a downward slope portion for preventing condensate staying in the condensate pipe from flowing into the drain pipe when the temperature of the condensate in the condensate pipe decreases. Drain pump up system for feed water heater of nuclear power plant. In the feed water heater drain pump-up system of the nuclear power plant according to claim 1,
Furthermore, it is equipped with a low-pressure feed water heater that is supplied with steam from a low-pressure turbine,
The feed water heater is a high pressure feed water heater to which steam is supplied from a high pressure turbine,
The feed water heater drain pump-up system of a nuclear power plant, wherein the connecting portion is located upstream of the high pressure feed water heater and downstream of the low pressure feed water heater. In the feed water heater drain pump-up system of the nuclear power plant according to claim 1,
Furthermore, it is equipped with a high-pressure feed water heater that is supplied with steam from a high-pressure turbine,
The feed water heater is a low pressure feed water heater that is supplied with steam from a low pressure turbine,
The feed water heater drain pump-up system of a nuclear power plant, wherein the connecting portion is located upstream of the low-pressure feed water heater and downstream of the condenser.

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