JP3984038B2 - Boiling water nuclear power plant - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In the present invention, water is poured into the RPV in an emergency where the piping of the reactor pressure vessel (RPV) is broken and the amount of water for cooling the reactor core in the RPV decreases beyond the range of transient changes assumed during normal operation. In particular, the present invention relates to a boiling water nuclear power plant equipped with an emergency core cooling system (ECCS) for cooling the core, and more particularly to a boiling water nuclear power plant having functions other than emergency water injection in ECCS.
[0002]
[Prior art]
The configuration of ECCS provided in a conventional boiling water nuclear power plant will be described.
[0003]
FIG. 1 shows the ECCS configuration of a conventional 1.35 million KWe class improved boiling water nuclear power plant (hereinafter referred to as ABWR). FIG. 2 schematically shows the ECCS configuration.
[0004]
The outline of the nuclear power plant shown in FIG. 1 will be described.
[0005]
A reactor pressure vessel (RPV) 9 having a fuel assembly in the core is accommodated so as to be entirely enclosed in a reactor containment vessel (PCV) 8. The internal space of the PCV 8 that stores the RPV 9 is divided into a dry well 19 and a pressure suppression chamber (S / C) 20. The dry well 19 is a space where the cooling water is discharged as an air-water mixture in the event of losing a large amount of cooling water in the RPV. The air-water mixture discharged to the dry well 19 is led to a pressure suppression pool (S / P) 11 in the S / C 20 through a vent pipe (not shown), and is cooled and condensed to increase the pressure in the PCV. Suppress.
[0006]
The condensate storage tank (CST) 10 placed outside the dry well 19 can also be placed in the dry well 19.
[0007]
The S / P 11 communicates with the RPV 9 through a pipe 42, a residual heat removal system (RHR system) pump 45, an RHR system heat exchanger 46, and a pipe 47. The RPV 9 has a flow path that returns to the RPV 9 again through the pipe 44, the pipe 42, the RHR pump 45, the RHR heat exchanger 46, and the pipe 47. These are each provided with three sections of power supply systems (A, B, C), and constitute a low-voltage ECCS.
[0008]
A reactor isolation cooling system (RCIC system) pump 30 driven by the turbine 24 injects water of CST 10 or S / P 11 into the RPV 9 through the pipe 26, the pipe 28, and the pipe 32. This belongs to the power supply system A. The HPCF pump 13 injects CST10 or S / P11 water into the RPV 9 via the pipe 26, the pipe 15, the pipe 14, and the pipe 18. The HPCF pump 13 is provided with two sections of a power supply system (B, C). The high-pressure core water injection system (RCIC system) pump 30 and the HPCF system pump 13 constitute a high-pressure ECCS.
[0009]
The above ABWR ECCS is designed not only to function as an emergency water injection facility but also to have several functions for regular use, and is designed to satisfy the following conditions: .
[0010]
First, the drive power for dynamic equipment such as pumps is supplied from three independent power sources, and second, the operating point for high pressure and low flow rate (necessary for small and medium breakage of piping connected to the RPV) Operational state, because the water level drops while the pressure inside the RPV remains high) and a low-pressure, high-flowing operating point (operating state required when the pipe connected to the RPV is severely ruptured. At the same time, the water level in the RPV decreases rapidly.) Third, it is possible to inject water at both, and thirdly, when a transient water level decrease in the RPV that may occur during normal operation occurs, The ability to operate at a low flow point and supply makeup water into the RPV, fourth, the ability to remove residual heat generated in the reactor when the reactor is shut down, and fifth, the ability to cool the PCV during an accident .
[0011]
A conventional ECCS for satisfying the above requirements will be described with reference to FIG.
[0012]
The ECCS 1 is composed of three sections: an A-system ECCS 2, a B-system ECCS 3, and a C-system ECCS 4. Drive power for dynamic devices such as the pumps 13, 30, 45 and motor valves shown in FIG. 1 is supplied from the A system power supply system 5, the B system power supply system 6, and the C system power supply system 7. The A system power system 5, the B system power system 6, and the C system power system 7 are independent power systems.
[0013]
The three sections have two systems, one for each of the high-pressure ECCS and the low-pressure ECCS. The A-system ECCS 2 includes a reactor isolation cooling system (RCIC system) as a high-pressure ECCS and a residual heat removal system (RHR system) as a low-pressure ECCS. The B-system ECCS 3 includes one high-pressure core water injection system (HPCF system) as a high-pressure ECCS and one RHR system as a low-pressure ECCS. The C-system ECCS 4 also includes one HPCF system as a high-pressure ECCS and one RHR system as a low-pressure ECCS.
[0014]
The relationship between the pump performance of these high-pressure ECCS and low-pressure ECCS is shown in FIG. FIG. 3 shows the pump flow rate on the horizontal axis and the pump head on the vertical axis. The operating point of the ECCS pump required when the pipe connected to the RPV is small or small is the operating point 71, and the operating point of the ECCS pump required when the pipe is connected to the RPV is the operating point 72. In other words, the ECCS may be constituted by a pump having a performance curve passing through these two points. However, since a pump having a performance curve that can cover both of the two operating points with one unit is difficult to manufacture and disadvantageous in terms of cost, the conventional technology uses a high-pressure ECCS pump (a pump having a performance curve 73). And a low pressure ECCS pump (a pump having a performance curve 74). As the power source configuration must be divided into three categories, the conventional technology had a total of 6 series of ECCS in the boiling water nuclear power plant.
[0015]
[Problems to be solved by the invention]
In the conventional technology, a boiling water nuclear power plant has a total of six systems as ECCS in order to satisfy the four requirements shown in the conventional technology. However, ECCS is not only a system that is basically not used during normal operation, but also a system with high equipment costs because a high safety grade is required. Therefore, it is economically disadvantageous to install a multi-system ECCS in one plant.
[0016]
In view of the above problems, an object of the present invention is to improve the economic efficiency of a nuclear power plant by making the number of ECCS systems as simple as possible.
[0017]
[Means for Solving the Problems]
The present invention is an emergency in which a pipe communicating with an RPV and flowing through a fluid such as water is broken and the amount of water for cooling the core in the RPV is reduced beyond the range of transient changes assumed during normal operation. Sometimes, in a boiling water nuclear power plant equipped with an emergency core cooling system (ECCS) that injects water into the RPV and cools the core, the ECCS has three systems each having one pump that injects water into the RPV. In addition, the drive power supply of each pump is an independent three-part power supply system, and at least two of the three systems are provided with heat exchangers that cool the cooling water injected into the RPV. .
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings illustrating examples of the present invention. The embodiment of the present invention is shown in FIGS. 4, 5, 12, and 13, but the present invention will be explained in comparison with the conventional example in the main points.
[0019]
FIG. 4 shows an ECCS configuration of a 700,000 Kwe class improved boiling water nuclear power plant (about half the electrical output of the improved boiling water nuclear power plant shown in the prior art) as an embodiment of the present invention. Yes.
[0020]
FIG. 5 schematically shows the configuration of an ECCS that is an embodiment of the present invention. As in the prior art, the ECCS 81 is composed of three sections of an A-system ECCS 82, a B-system ECCS 83, and a C-system ECCS 84.
[0021]
Each of them supplies driving power for a dynamic device such as a pump or an electric valve from an A system power supply system 85, a B system power supply system 86, and a C system power supply system 87. The A-system power supply system 85, the B-system power supply system 86, and the C-system power supply system 87 are independent power supply systems. The A-system ECCS 82 includes one RHR system that is a low-pressure ECCS. The B-system ECCS 83 also includes one RHR system that is a low-pressure ECCS. The C ECCS 84 includes one HPCF system which is a high pressure ECCS. Therefore, there are only three ECCS in total.
[0022]
Here, in order to deepen the understanding of the present invention, the conventional examples shown in FIGS. 6, 7, 8, 9, 10, and 11 will be referred to.
[0023]
FIG. 6 shows the system configuration of the HPCF system. The water in the condensate storage tank (CST) 10 or the pressure suppression pool (S / P) 11 is led to the HPCF pump 13 through the pipe 12 or the pipe 15, respectively (this switching is performed by opening and closing the motorized valve 16 and the motorized valve 17). The pressure is increased by the pump 13 and then injected into the RPV through the pipe 14 and the pipe 18.
[0024]
FIG. 7 shows the system configuration of the RCIC system. The steam generated in the RPV 9 is guided to the turbine 24 directly connected to the RCIC pump 30 through the pipe 22 and the pipe 23 branched from the main steam pipe 21 and driven. Exhaust gas from the turbine 24 is discharged to the S / P 11 through a pipe 25. The RCIC pump 30 uses the water of CST10 or S / P11 as the water source through the pipe 26 and the pipe 28 (this switching is performed by opening and closing the motorized valve 27 and the motorized valve 29), respectively. The pressure is increased and injected into the RPV 9 through the pipe 31 and the pipe 32. The HPCF pump 13 and the RCIC pump 30 that are high-pressure ECCS are high-pump pumps that can inject water into the RPV even near the normal plant operating pressure.
[0025]
FIG. 8 shows the system configuration of the RHR system and the ADS during RPV water injection. The water of the S / P 11 is led to the RHR pump 45 through the pipe 42, and is pressurized by the RHR pump 45 and injected into the RPV 9 through the pipe 47. The RHR pump 45 is a low-pressure ECCS and is a low pressure pump that assumes that water is poured into the RPV 9 when the pressure inside the RPV 9 is near atmospheric pressure, so that water cannot be poured when the pressure inside the RPV 9 is high. In such a case, the RPV 9 internal pressure is reduced by the ADS 49 before the RHR pump 45 is started. The ADS forcibly opens the main steam relief valve 49 installed in the main steam pipe 21 that guides the steam generated in the RPV 9 to the turbine side by means of an accumulator. It is a system that discharges into P11.
[0026]
The activation logic of the ADS is shown in FIG. Both the condition 65 that “the water level in the RPV 9 has fallen below the specified value” and the condition 66 that “the pressure in the dry well 19 has become higher than the specified value” are satisfied, and “the low-pressure ECCS is activated. When the condition 68 of “Yes” is satisfied, the operation 67 of “ADS49 activation” is executed.
[0027]
FIG. 10 shows the system configuration in the reactor residual heat removal operation mode when the RHR system is stopped. FIG. 10 shows a state in which the motor-operated valve 41 is closed and the motor-operated valve 43 is opened from FIG. The water in the RPV 9 is led from the pipe 44 to the RHR pump 45 through the pipe 42, the pressure is increased by the RHR pump 45, and the water is cooled by passing through the RHR heat exchanger 46, and then returned to the RPV 9 through the pipe 47. Cooling water is supplied to the RHR heat exchanger 46 through a pipe 61 and is discharged from the pipe 62.
[0028]
FIG. 11 shows the system configuration in the RHR system containment vessel cooling operation mode during an accident. FIG. 11 shows a state in which the motor-operated valve 67 and the motor-operated valve 68 are closed from FIG. 8, and the motor-operated valve 63, the motor-operated valve 64, the motor-operated valve 65, and the motor-operated valve 66 are opened. The S / P water is led to the RHR pump 45 through the pipe 42, and after being pressurized by the RHR pump 45, the water is discharged from the sparger 101 and the sparger 102 to the dry well 105 and the S / C 20 through the pipe 69 and the pipe 70, respectively. .
[0029]
The relationship between the pump performance of these high-pressure ECCS and low-pressure ECCS is shown in FIG. FIG. 12 shows the pump flow rate on the horizontal axis and the pump head on the vertical axis. The operating point of the ECCS pump required when the pipe connected to the RPV is small or small is the operating point 91, and the operating point of the ECCS pump required when the pipe is connected to the RPV is the operating point 92. By reducing the plant output to 100 MWe or less, the required flow rate of the low-pressure ECCS is reduced, and the performance curve 93 of the HPCF pump can pass through these two points. This eliminates the need for the low-pressure ECCS for the C ECCS, and makes it possible to configure only one HPCF system.
[0030]
On the other hand, the A system ECCS and the B system ECCS strengthen the ADS start condition, and the high pressure ECCS can be deleted by setting the start pressure of the low pressure system ECCS higher than that of the prior art, and the RHR system is a low pressure system ECCS. Only the configuration was adopted. The strengthening of the ADS activation condition is shown in FIG. FIG. 13 is a diagram showing the ADS activation logic as in FIG. That is, in the present invention, either the condition 65 “the water level in the RPV 9 has dropped below the specified value” or the condition 66 “the pressure in the dry well 19 has become higher than the specified value” is satisfied, and When the condition 68 that “low-pressure ECCS is activated” is satisfied, an operation 67 “ADS 49 is activated” is executed.
[0031]
As described above, since the starting conditions of the ADS 49 are relaxed, the starting of the ADS and the water injection into the PRV by the RHR system (low pressure system ECCS) can be performed more reliably even when the pressure in the RPV 9 is high. Furthermore, the set value of the RPV internal pressure when the low-pressure ECCS is started up was raised.
[0032]
This is because, unlike the HPCF system, which starts the pump immediately upon detecting a decrease in the water level in the RPV 9, and can start water injection into the RPV 9, the RHR system detects the decrease in the water level in the RPV, and then the ADS 49 is activated. This is because, since the pressure in the RPV 9 is lowered until the pressure reaches the RHR system operable pressure and the water is injected into the RPV 9, it takes a little time to start water injection compared to the HPCF system. Therefore, by raising the pressure set value in the RPV for starting the RHR system, the time difference until the start of water injection was reduced, and the necessity of installing a high-pressure system ECCS such as the HPCF system was reduced.
[0033]
As described above, the present invention provides a boiling water nuclear power plant including an ECCS having a configuration in which only one system of a high-pressure ECCS or a low-pressure ECCS is installed in each of the three sections of the ECCS.
[0034]
The main features of the present invention described above are as follows.
[0035]
The first feature is that the ECCS has a total of three systems, one for each power supply section, and two or more of them can be injected into the RPV from the pump through the heat exchanger.
[0036]
With this, boiling with ECCS with the number of systems reduced to the same number as the power supply category, and with the function of removing decay heat generated in the core when the reactor is shut down and the function of cooling the containment vessel in the event of an accident Can provide water nuclear power plants.
[0037]
The second feature is that the ECCS is composed of one high-pressure ECCS and two low-pressure ECCS for a total of three systems, and the “water level in the RPV is lower than a specified value” or “the PCV The ADS activation condition is that any one of “the pressure in the dry well is higher than a predetermined value” and that “the low-pressure ECCS is activated” is established.
[0038]
This realizes the first means by the high-pressure system ECCS and the low-pressure system ECCS, and an ECCS configuration having a function of injecting makeup water into the RPV when the water level in the RPV decreases transiently during normal operation. Can provide.
[0039]
The third feature is that, in the ECCS configuration described in the first feature, the starting pressure of the low pressure ECCS is larger than ½ of the starting pressure of the high pressure ECCS and smaller than the normal operating pressure of about 7 MPa (gage). That is.
[0040]
As a result, in addition to the effects of the second feature, the low pressure ECCS can start water injection into the RPV as quickly as the high pressure ECCS in the event of a break in the piping connected to the RPV. A boiling water nuclear power plant having an ECCS is provided.
[0041]
The fourth feature is that the electrical output of the power plant is set to 1 million KWe or less in the ECCS configuration described in the first feature or the second feature.
[0042]
Thereby, the boiling water nuclear power plant of the suitable plant output level which implement | achieves the 1st characteristic or the 2nd characteristic can be provided.
[0043]
【The invention's effect】
According to the present invention, the economic efficiency of a nuclear power plant can be improved with a simple configuration.
[Brief description of the drawings]
FIG. 1 relates to a conventional example, and is a schematic diagram showing an entire RPV and ECCS piping system.
FIG. 2 relates to a conventional example, and is a schematic diagram in which ECCS is summarized in relation to a power supply system.
FIG. 3 is a performance curve diagram of an ECCS pump according to a conventional example.
FIG. 4 is a schematic diagram showing an overall RPV and ECCS piping system in an example according to an embodiment of the present invention.
FIG. 5 is a schematic diagram illustrating ECCS in relation to a power supply system in an example according to an embodiment of the present invention.
FIG. 6 is a diagram illustrating a system configuration of an HPCF system according to a conventional example.
FIG. 7 is a diagram showing a system configuration of an RCIC system according to a conventional example.
FIG. 8 is a diagram showing a system configuration in an RHR RPV water injection mode according to a conventional example.
FIG. 9 is a block diagram illustrating the activation principle of an ADS system according to a conventional example.
FIG. 10 relates to a conventional example and is a diagram showing a system configuration in an RHR system stop-time cooling mode.
FIG. 11 relates to a conventional example and is a diagram showing a system configuration in an RHR containment vessel cooling mode.
FIG. 12 is a performance curve diagram of an ECCS pump in an example according to the embodiment of the present invention.
FIG. 13 is a block diagram showing an activation principle of an ADS system in an example according to the embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1,81 ... ECCS, 2,82 ... A system ECCS, 3,83 ... B system ECCS, 4,84 ... C system ECCS, 8 ... Reactor containment vessel, 9 ... Reactor pressure vessel (RPV), 10 ... Recovery Water storage tank, 11 ... suppression pool (S / P), 13 ... high pressure core water injection (HPCF) pump, 19 ... dry well, 20 ... pressure suppression chamber (S / C), 21 ... main steam piping, 24 ... Reactor isolation cooling system (RCIC system) turbine, 30 ... RCIC system pump, 45 ... Residual heat removal system (RHR system) pump, 46 ... RHR system heat exchanger, 49 ... Automatic decompression system (ADS), 73, 93 ... high-pressure ECCS pump performance curve, 74, 94 ... low-pressure ECCS pump performance curve, 101 ... dry well sparger, 102 ... S / C sparger.

Claims (3)

A reactor pressure vessel (RPV) having a fuel assembly in the core, and an airtight vessel that encloses the RPV as a whole and seals the radioactive material so that it does not leak to the outside even if the radioactive material is released from the RPV. A reactor containment vessel (PCV) having the functions of: a condensate storage tank, a pressure suppression pool, the RPV, the condensate storage tank, and the pressure suppression pool, and a fluid such as water is distributed. It has an automatic decompression system (ADS) that operates to lower the pressure in the RPV in an emergency, and an amount of water that cools the reactor core in the RPV when the piping breaks is assumed during normal operation. In the case of an emergency that decreases beyond the range of transient change, in a boiling water nuclear power plant equipped with an emergency core cooling system (ECCS) that injects water into the RPV to cool the core,
The ECCS has three systems each having one pump for injecting water into the RPV, and the drive power supply of each pump is an independent three-part separate power supply system, and at least two of the three systems are used. The system is equipped with a heat exchanger that cools the cooling water poured into the RPV in the previous term,
In the ECCS, one system is a high pressure system, the remaining two systems are low pressure systems, a high pressure pump is used for the high pressure system, and a low pressure pump is used for the low pressure system.
Water injection into the RPV by the high pressure ECCS is possible even when the pressure in the RPV is equal to the pressure during normal operation, and water injection into the RPV by the low pressure ECCS is performed when the pressure in the RPV is normal operation. The ADS is operated under the condition that the water level in the RPV is lower than a specified value or the pressure in the PCV (dry well) storing the RPV is lower than a specified value. Boiling water nuclear power plant, which is established when “the low-pressure system ECCS is activated”. What is described in claim 1
The boiling water nuclear power plant is characterized in that the pressure at which the low-pressure ECCS is activated is greater than ½ of the pressure at which the high-pressure ECCS is activated and lower than the pressure during normal operation. In the boiling water nuclear power plant according to claim 1 or 2 ,
A boiling water nuclear power plant characterized in that the power generation output of the power plant is 1 million KWe or less.

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