JP2013113772A - Reactor cooling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reactor cooling device capable of minimizing an energy loss in a turbine without losing a cooling function of a reactor even though an amount of steam generation in a reactor drops in an emergency.SOLUTION: A reactor cooling device 10 relating to this invention includes a plurality of turbines 222 for power storage driven by steam introduced from a reactor 2, a power storage part 21 for storing power by driving the turbines 222 for power storage, a cooling system pump 26 for supplying cooling water to the reactor 2 by being driven by the power of the power storage part 21, a flow rate detection part 16 for detecting a flow rate R of the steam introduced into the turbines 222 for power storage, and a control part 19 for controlling the number of turbines 222 for power storage to be driven on the basis of a detection value of the flow rate detection part 16.

Description

  The present invention relates to a nuclear reactor cooling apparatus that supplies cooling water to a nuclear reactor by driving a pump with a turbine.

  A boiling water nuclear reactor widely used for power generation is a nuclear reactor that boiles light water with thermal energy generated by a fission reaction and extracts it as high-temperature and high-pressure steam. In this boiling water reactor, it is necessary to maintain the reactor cooling so that the reactor will not melt even if the cooling water is lost due to damage to the piping of the cooling system that cools the reactor. In view of this, this boiling water reactor is provided with a reactor cooling device called a reactor core isolation cooling system (RCIC: Reactor Core Isolation Cooling System).

  In this reactor isolation cooling system, steam extracted from the reactor is introduced into the turbine. And a cooling water is supplied with respect to a nuclear reactor by driving a pump with the motive power obtained by the turbine (for example, refer patent document 1).

JP 2011-226783 A

  However, in the reactor isolation cooling system as the conventional reactor cooling device, the pump for supplying the cooling water is driven by the turbine as described above, and this turbine is driven by the steam generated in the reactor. The Therefore, when the amount of steam generated in the reactor becomes a certain value or less in an emergency, the pump is stopped by stopping the turbine, thereby causing a problem that the cooling function of the reactor is lost.

  In addition, in the conventional reactor isolation cooling system as the reactor cooling device, if the amount of steam generated in the reactor decreases in an emergency, the turbine operates in a region with poor thermal efficiency, resulting in a problem of increased energy loss. is there. In particular, when a large power generation turbine is used as the turbine for cooling the reactor isolation system, the thermal efficiency of the turbine is particularly deteriorated, so that the problem of the energy loss becomes significant.

  The present invention has been made in view of such circumstances, and its purpose is to prevent the loss of the reactor cooling function even if the amount of steam generated in the reactor is reduced in an emergency. An object of the present invention is to provide a reactor cooling apparatus capable of minimizing energy loss in a turbine.

  In order to achieve the above object, the present invention employs the following means. That is, the reactor cooling device according to the present invention includes a plurality of power storage turbines that are driven by steam introduced from a nuclear reactor, a power storage unit that is stored by driving the power storage turbine, and power of the power storage unit. A cooling system pump that supplies cooling water to the nuclear reactor by being driven, a detection unit that detects a state quantity of steam introduced into the power storage turbine, and a plurality of values based on detection values of the detection unit And a control unit for controlling the number of driven turbines for power storage.

  According to such a configuration, surplus power that has not been used to drive the power storage turbine is stored in the power storage unit while a certain amount of steam is generated in the nuclear reactor during normal operation. When the amount of steam generated in the nuclear reactor when the abnormality occurs decreases to a certain level or less, the cooling system pump is driven by the power stored in the power storage unit. Thus, even when an abnormality occurs, the cooling water is supplied to the reactor by the cooling system pump, so that the cooling function of the reactor can be maintained. In addition, since the controller appropriately controls the number of power storage turbines driven according to the steam state quantity, energy loss in the power storage turbine can be minimized.

  Further, in the reactor cooling apparatus according to the present invention, the control unit controls the number of power storage turbines driven so as to drive each power storage turbine with maximum thermal efficiency and discard the remaining steam. It is characterized by doing.

  According to such a configuration, all the power storage turbines to be driven are driven with the maximum thermal efficiency. Therefore, energy loss in the power storage turbine can be minimized.

  Further, in the reactor cooling device according to the present invention, the control unit drives the power storage turbine with maximum thermal efficiency, and drives the power storage turbine with the remaining steam. The number of driving turbines for power storage is controlled.

  According to such a configuration, since the power storage turbine is driven with the maximum thermal efficiency, energy loss in the power storage turbine can be minimized. Moreover, since one power storage turbine is driven by the remaining steam, there is no waste of steam.

  Moreover, the reactor cooling device according to the present invention is characterized in that the control unit controls the number of driven turbines for power storage so that power storage in the power storage unit is completed earliest.

  According to such a configuration, when an abnormality occurs during power storage in the power storage unit, the maximum power at that time is stored in the power storage unit. Therefore, the cooling system pump can be driven to supply cooling water to the nuclear reactor for the longest time after the occurrence of the abnormality.

  Further, the reactor cooling device according to the present invention is provided with a flow rate adjustment valve that adjusts an amount of steam introduced into each of the power storage turbines, and the control unit controls the operation of the flow rate adjustment valve to control the power storage. The number of turbines driven is controlled.

  According to such a configuration, the power storage turbine is driven by opening the flow rate adjusting valve widely and introducing a large amount of steam to drive the power storage turbine, while the flow rate adjusting valve is narrowed down to reduce the amount of steam introduced. Can be stopped. Thereby, the drive number of the turbines for electrical storage can be easily controlled only by controlling the opening degree of the flow regulating valve.

  Further, the reactor cooling device according to the present invention is provided with an on-off valve for switching introduction or stop of steam into each of the electric storage turbines, and the control unit controls the operation of the on-off valve to control the electric storage Controlling the number of driven turbines.

  According to such a configuration, the power storage turbine is driven by opening the on-off valve and introducing steam, while the power storage turbine is stopped by closing the on-off valve and stopping the introduction of steam. it can. Accordingly, the number of power storage turbines driven can be easily controlled only by controlling the opening / closing of the on / off valves.

  The reactor cooling device according to the present invention is characterized in that the state quantity of steam is a flow rate of steam.

  According to such a configuration, the state quantity of steam can be measured easily and accurately.

  According to the reactor cooling device of the present invention, even if the amount of steam generated in the reactor is reduced in an emergency, the cooling function of the reactor is not lost, and the energy loss in the turbine is minimized. Can do.

It is a mimetic diagram showing the whole reactor cooling device composition concerning an embodiment of the present invention. It is a functional block diagram which shows the function structure of the control part which concerns on embodiment of this invention. It is a graph which shows an example of the characteristic curve of the turbine for electrical storage memorized by the database concerning the embodiment of the present invention. It is a flowchart which shows the flow of the process in the control part which concerns on embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. First, the configuration of the reactor cooling device according to the embodiment of the present invention will be described. FIG. 1 is a schematic diagram illustrating an overall configuration of a nuclear power plant 1 including a reactor cooling device 10 according to the present embodiment.

  As shown in FIG. 1, a nuclear power plant 1 includes a boiling water reactor 2 (hereinafter simply referred to as “reactor 2”) and a main turbine 4 connected to the reactor 2 via a main steam pipe 3. And a reactor cooling device 10 for cooling the reactor 2.

(Reactor)
As shown in FIG. 1, the nuclear reactor 2 includes a nuclear reactor pressure vessel 5, a pair of pressure suppression chambers 6, and a nuclear reactor containment vessel 7 that stores these.

  The reactor pressure vessel 5 plays a role of generating steam by a nuclear reaction of fuel. The reactor pressure vessel 5 is not shown in detail in FIG. 1, but is a steel vessel that can withstand high pressures. Inside, a fuel, a control rod, a jet pump, a steam separator, steam drying Containers are stored. As shown in FIG. 1, one end of the main steam pipe 3 is connected to the reactor pressure vessel 5.

  The pressure suppression chamber 6 serves to suppress an increase in the pressure inside the reactor containment vessel 7 when an abnormality occurs. That is, although not shown in detail in FIG. 1, water is always stored in these pressure suppression chambers 6. When the main steam pipe 3 is damaged or the like, the water vapor leaking from the main steam pipe 3 is condensed by being cooled to the pressure suppression chamber 6. As a result, the internal pressure of the reactor containment vessel 7 is prevented from increasing due to the water vapor filling.

  The reactor containment vessel 7 plays a role of confining radioactive materials released when the reactor pressure vessel 5 or various pipes are damaged. As shown in FIG. 1, the reactor containment vessel 7 is always in a state where water W is stored at the bottom thereof.

(Main turbine)
The main turbine 4 is driven by steam introduced from the nuclear reactor 2 through the main steam pipe 3. The main turbine 4 drives a generator (not shown) so that electric power can be obtained.

(Reactor cooling device)
The reactor cooling device 10 plays a role of cooling the reactor 2 using steam generated by the decay heat of the core in an emergency where all electric power is lost from the reactor 2. As shown in FIG. 1, the reactor cooling device 10 includes a branch steam pipe 11 through which steam flows, a branch steam pipe unit 12 provided along the branch steam pipe 11, and cooling water through which cooling water flows. A supply pipe 13 and a cooling water supply pipe unit 14 provided along the cooling water supply pipe 13 unit are provided.

  As shown in FIG. 1, the branch steam pipe 11 branches off from the main steam pipe 3, and its downstream end is introduced into the reactor containment vessel 7. Further, the branch steam pipe 11 has a first branch steam pipe 11A, a second branch steam pipe 11B, and a third branch steam pipe 11C by further branching into three at an intermediate portion thereof. On the other hand, the cooling water supply pipe 13 has an upstream end connected to the condensate storage tank 15 and a downstream end introduced into the reactor pressure vessel 5.

  As shown in FIG. 1, the branch steam pipe unit 12 is provided on the downstream side of the flow rate detection unit 16 that measures the flow rate (state quantity) of the steam flowing through the branch steam pipe 11 and controls the steam flow rate. A plurality of steam control valves 17, a pump drive unit 18 provided further downstream thereof, and a control unit 19 that controls the operation of the pump drive unit 18 according to the detection result of the flow rate detection unit 16. .

  As shown in FIG. 1, the pump drive unit 18 includes three power generation units 20 connected in parallel to the branch steam pipe 11 and one power storage unit 21 to which each of the power generation units 20 is connected. ing. The power generation section 20 includes a first power generation section 22 disposed in the first branch steam pipe 11A, a second power generation section 23 disposed in the second branch steam pipe 11B, and a first power section disposed in the third branch steam pipe 11C. Three power generation units 24 are provided.

  As shown in FIG. 1, the first power generation unit 22 includes a flow rate adjusting valve 221 that adjusts the opening degree of the first branch steam pipe 11 </ b> A, a power storage turbine 222 that is driven when steam is introduced, and a power storage turbine. And a generator 223 driven by 222. Similarly, the second power generation unit 23 and the third power generation unit 24 each include a flow rate adjustment valve 221, a power storage turbine 222, and a power generator 223. And the control part 19 shown in FIG. 1 is controlling the operation | movement of the flow volume adjustment valve 221 of the 1st electric power generation part 22, the 2nd electric power generation part 23, and the 3rd electric power generation part 24, respectively. Although not shown in detail in the drawing, an on-off valve that opens or closes the branch steam pipe 11 may be used instead of the flow rate adjustment valve 221 of the present embodiment.

  According to the pump driving means 18 configured as described above, the electric power generated by the first power generation unit 22, the second power generation unit 23, and the third power generation unit 24 is stored in the power storage unit 21. And the cooling system pump 26 which comprises the cooling water supply pipe unit 14 mentioned later is driven by the electric power of this electrical storage part 21 being supplied.

  As shown in FIG. 1, the cooling water supply pipe unit 14 includes the condensate storage tank 15, a cooling water control valve 25 for controlling the flow rate of the cooling water, and a cooling system pump 26 provided on the downstream side thereof. Have. Here, in the condensate storage tank 15, condensate obtained by cooling the steam after driving the main turbine 4 and returning it to water is stored as cooling water for the reactor 2. The cooling system pump 26 is driven by the power storage unit 21 constituting the pump driving means 18. As a result, the cooling system pump 26 pumps the cooling water from the condensate storage tank 15 through the cooling water supply pipe 13 and injects the cooling water into the reactor pressure vessel 5.

(Control part)
The control unit 19 plays a role of controlling the number of driven power storage turbines 222. As shown in FIG. 1, the control unit 19 is electrically connected to the flow rate detection unit 16. Further, the control unit 19 is also electrically connected to the flow rate adjustment valve 221 constituting the third power generation unit 24 from the first power generation unit 22. Thereby, based on the detection result input from the flow rate detection unit 16, the control unit 19 transmits an electric signal for controlling the operation from the first power generation unit 22 to the flow rate adjustment valve 221 of the third power generation unit 24. Output. That is, the control unit 19 increases the opening of the flow rate adjustment valve 221 and increases the amount of steam introduced for the power storage turbine 222 to be driven. On the other hand, the control unit 19 reduces the amount of steam introduced by lowering the opening of the flow rate adjustment valve 221 for the power storage turbine 222 to stop driving. Thus, the control unit 19 can arbitrarily control the number of power storage turbines 222 driven according to the steam flow rate in the branch steam pipe 11.

  Next, the functional configuration of the reactor cooling apparatus 10 according to the embodiment of the present invention will be described. FIG. 2 is a functional block diagram showing a functional configuration of the control unit 19. The control unit 19 includes an input reception unit 191 that receives a detection result from the flow rate detection unit 16, a determination unit 193 that compares the received detection result with a threshold value stored in advance in the database 192, and determines the magnitude thereof, and according to the determination result And an output unit 194 for outputting a signal for controlling the operation from the first power generation unit 22 to the flow rate adjustment valve 221 of the third power generation unit 24.

  Here, the database 192 stores in advance the thermal efficiency characteristics of the power storage turbine 222. FIG. 3 is a graph showing an example of a characteristic curve of the power storage turbine 222 stored in the database 192, wherein the horizontal axis represents the flow rate of steam introduced into the power storage turbine 222, and the vertical axis represents the power storage turbine 222. Each shows thermal efficiency. According to this figure, the power storage turbine 222 has the highest thermal efficiency when the steam flow rate is the threshold value X, that is, the energy loss is minimized. The thermal efficiency of the power storage turbine 222 gradually decreases as the steam flow rate becomes smaller than the threshold value X. Similarly, the thermal efficiency of the power storage turbine 222 gradually decreases as the steam flow rate exceeds the threshold value X.

  Next, the process flow of the reactor cooling apparatus 10 according to the embodiment of the present invention will be described. FIG. 4 is a flowchart showing the flow of processing in the control unit 19. First, the control unit 19 acquires the steam flow rate R in the branch steam pipe 11 by controlling the flow rate detection unit 16 (S1). Then, the control unit 19 compares the acquired steam flow rate R with the threshold value X (shown in FIG. 3) stored in advance in the database 192 (S2).

  As a result, when the flow rate R is smaller than twice the threshold value X (R <2X), the control unit 19 drives only one of the three power storage turbines 222 (S3). That is, the control unit 19 introduces steam at a flow rate of the threshold value X into the power storage turbine 222 by increasing the opening degree of the flow rate adjustment valve 221 corresponding to one power storage turbine 222. On the other hand, the control unit 19 stops the introduction of steam to each of the power storage turbines 222 by lowering the opening degrees of the flow rate adjusting valves 221 corresponding to the remaining two power storage turbines 222. As a result, one power storage turbine 222 is driven with the maximum thermal efficiency, and the remaining two power storage turbines 222 are stopped.

  Further, as a result of the comparison in S <b> 2, when the steam flow rate R is two times or more than the threshold value X and smaller than three times (2X ≦ R <3X), the control unit 19 includes two of the three power storage turbines 222. Only the base is driven (S4). That is, the control unit 19 introduces steam at a flow rate of the threshold value X into each of the power storage turbines 222 by increasing the opening degree of the flow rate adjusting valve 221 corresponding to the two power storage turbines 222. On the other hand, the controller 19 stops the introduction of steam to the power storage turbine 222 by lowering the opening of the flow rate adjustment valve 221 corresponding to the remaining power storage turbine 222. As a result, the two power storage turbines 222 are each driven with the maximum thermal efficiency, and the remaining one power storage turbine 222 is stopped.

  When the steam flow rate R is larger than three times the threshold value X (R> 3X) as a result of the comparison in S2, the controller 19 drives all three power storage turbines 222 (S5). That is, the controller 19 introduces steam at a flow rate of the threshold value X to each of the power storage turbines 222 by increasing the opening degree of the flow rate adjusting valve 221 corresponding to all three power storage turbines 222. As a result, all three power storage turbines 222 are each driven with maximum thermal efficiency.

  Finally, the control unit 19 discards the remaining steam other than the steam introduced into the power storage turbine 222 (S6). Thus, the process by the control unit 19 ends. Instead of discarding the remaining steam as in the present embodiment, the other power storage turbine 222 may be driven using the remaining steam. In this case, the power storage turbine 222 driven by the remaining steam does not maximize the thermal efficiency, so that energy loss occurs. However, since the remaining steam is used without being discarded, there is an advantage that the steam is not wasted.

  According to such processing by the control unit 19, all the power storage turbines 222 to be driven are driven with the maximum thermal efficiency. Therefore, energy loss in the power storage turbine 222 can be minimized. Further, since the power generation unit 20 that supplies power to the power storage unit 21 is made redundant, when a failure or the like occurs in any of the power generation units 20, only the power generation unit 20 is stopped and another power generation unit 20 is stopped. It is possible to continue power storage for the power storage unit 21 using. Thereby, the reliability of the reactor cooling device 10 can be improved. In the case where an on-off valve is used instead of the flow rate adjusting valve 221 as described above, steam may be introduced into the power storage turbine 222 at a flow rate of the threshold value X when the on-off valve is opened.

  In the present embodiment, the number of power storage turbines 222 to be driven is determined so that the power storage turbines 222 are driven with the maximum thermal efficiency. However, instead of this, for example, the number of power storage turbines 222 to be driven may be determined so that power storage in the power storage unit 21 is completed earliest. That is, the number of power storage turbines 222 driven may be determined so that the total amount of power generated per unit time by the first power generation unit 22, the second power generation unit 23, and the third power generation unit 24 is maximized. In this way, when an abnormality occurs during power storage in the power storage unit 21, the power storage unit 21 stores the maximum power at that time. Therefore, the cooling system pump 26 can be driven and cooling water can be supplied to the nuclear reactor 2 for the longest time after the occurrence of abnormality.

  In addition, as another means for determining the number of power storage turbines 222 to be driven, the drive algebra may be determined so that steam generated in the nuclear reactor 2 is evenly introduced to all the power storage turbines 222. In this way, there is an advantage that the control of the flow rate adjustment valve 221 by the control unit 19 can be simplified.

(Modification)
In the present embodiment described above, water vapor generated in the nuclear reactor 2 in an emergency is used as the working fluid for driving the power storage turbine 222. Instead, a low boiling point medium having a lower boiling point than water is used. Can also be used as the working fluid. As the low boiling point medium, for example, pentane having a boiling point of about 36 ° C. can be used. According to this, since the amount of steam is less likely to decrease even at a lower temperature than when steam is used as the working fluid, the power storage turbine 222 can be driven to a lower temperature. Specifically, the reactor cooling apparatus 10 can be operated up to a temperature region that is about 60 ° C. lower than the case where the working fluid is water vapor.

  Further, in the present embodiment, the pump driving means 18 is constituted by the three power generation units 20, but the number of the power generation units 20 is not limited to this and can be arbitrarily changed. Further, in this embodiment, only one common power storage unit 21 is provided for the three power generation units 20, but the number of power storage units 21 is not limited to this, and the power storage units 21 are separately provided for each power generation unit 20. It may be provided. In this embodiment, the number of power storage turbines 222 to be driven is determined according to the flow rate of steam. However, the state quantity of steam according to the present invention is not limited to the flow rate of steam, and steam pressure or the like may be employed.

  The various shapes, combinations, operation procedures, and the like of the constituent members shown in the above-described embodiments are merely examples, and various changes can be made based on design requirements and the like without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 Nuclear power plant 2 Reactor 3 Main steam pipe 4 Main turbine 5 Reactor pressure vessel 6 Pressure suppression chamber 7 Reactor containment vessel 10 Reactor cooling device 11 Branch steam pipe 11A First branch steam pipe 11B Second branch steam pipe 11C Third branch steam pipe 12 Branch steam pipe unit 13 Cooling water supply pipe 14 Cooling water supply pipe unit 15 Condensate storage tank 16 Flow rate detection unit 17 Steam control valve 18 Pump drive means 19 Control unit 191 Input reception unit 192 Database 193 Determination unit 194 output unit 20 power generation unit 21 power storage unit 22 first power generation unit 221 flow rate adjustment valve 222 power storage turbine 223 generator 23 second power generation unit 24 third power generation unit 25 cooling water control valve 26 cooling system pump R flow rate W water X threshold

Claims (7)

A plurality of power storage turbines driven by steam introduced from a nuclear reactor;
A power storage unit that stores power by driving these power storage turbines;
A cooling system pump that supplies cooling water to the nuclear reactor by being driven by electric power of the power storage unit;
A detection unit for detecting a state quantity of steam introduced into the power storage turbine;
Based on the detection value of the detection unit, a control unit for controlling the number of driving of the plurality of power storage turbines;
A reactor cooling apparatus comprising:   2. The control unit according to claim 1, wherein the control unit controls the number of the power storage turbines to be driven so as to drive each of the power storage turbines with maximum thermal efficiency and to discard the remaining steam. Reactor cooling device.   The control unit controls the number of driving of the power storage turbines so that each power storage turbine is driven with the maximum thermal efficiency, and one power storage turbine is driven with the remaining steam. The reactor cooling apparatus according to claim 1.   2. The reactor cooling apparatus according to claim 1, wherein the control unit controls the number of driving of the power storage turbine so that power storage in the power storage unit is completed earliest. 3.   A flow rate adjusting valve that adjusts the amount of steam introduced into each of the power storage turbines is provided, and the control unit controls the number of driven power storage turbines by controlling the operation of the flow rate adjusting valve. The reactor cooling device according to any one of claims 1 to 4.   An opening / closing valve for switching between introduction or stoppage of steam to each of the storage turbines is provided, and the control unit controls the number of the storage turbines driven by controlling the operation of the opening / closing valves. The reactor cooling device according to any one of claims 1 to 4.   The reactor cooling apparatus according to any one of claims 1 to 6, wherein the state quantity of steam is a flow rate of steam.

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