JPH06201883A - Boiling water reactor facility - Google Patents

Abstract

(57) [Abstract] [Purpose] In a boiling water reactor facility, the facility of the emergency core cooling system is simplified, the operability is improved, the emergency power source is simplified, and the maintainability is improved. [Structure] The automatic depressurization system 14 is activated only by a signal set to a first water level L1 which is lower than the normal operating water level, and the emergency core cooling system is activated in response to the reactor water level low signal. It is composed only of a low-pressure water injection system provided with a pump 9 having a discharge pressure and a discharge flow rate that does not expose the core of the furnace. The reactor isolation cooling system RCIC, HPCF shall be the normal system, and the second is higher than the first water level and lower than the normal operating water level.
The pumps 1 and 3 having the discharge pressure and the discharge flow rate which do not reach the first water level in the reactor isolation event and are activated by receiving the signals set to the water levels L2 and L3 of the above are provided. The flow control valves 8a and 8b of the reactor isolation cooling system have an automatic flow control function.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boiling water reactor having a main steam system, a reactor isolation cooling system for replenishing cooling water when the reactor water level drops for some reason, and an emergency core cooling system. Regarding equipment.

[0002]

2. Description of the Related Art Conventionally, as described in the engineering safety equipment in Chapter 8 attached to the application for permitting installation of Kashiwazaki Kariwa Units 6 and 7, when a reactor using an internal pump in the recirculation system malfunctions. The system for supplying the reactor cooling water is composed of a reactor isolation cooling system (RCIC) and an emergency core cooling system (ECCS). The emergency core cooling system has two high pressure water injection systems (HPCF) and three low pressure water injection systems (LPFL). By using the reactor isolation cooling system as a high pressure water injection system, the high pressure water injection system is also 3 The system consists of three power supplies, three of which are connected to each of the three emergency power supplies, one for each high-pressure and low-pressure water injection system.

The capacity of these water injection systems is designed to be 50% of the required capacity in design, and in actuality, sufficient capacity can be secured if the high pressure / low pressure water injection systems of the two sections are started. . Therefore, in the unlikely event of a reactor failure, it is a strict assumption that the functional design is sufficient even if a failure occurs in the first power supply section.

RCIC uses a turbine-driven pump to reduce the reactor water level (L) during transients such as reactor isolation.
1) The reactor water level L2 is set higher than the normal operation water level and started at the reactor water level L2 to prevent the reactor water level from decreasing. Also, in the event of a loss of coolant, L2 is started, and cooling water is injected even when the reactor pressure is high.

The HPCF starts at the reactor water level L1.5 set between the water levels L1 and L2, and in the case of a coolant loss accident, injects cooling water from a state where the reactor pressure is high, similar to RCIC. . In addition, the HPCF will have an RCI during a transition.
Even if C does not start, it has a function of preventing the water level from lowering instead of RCIC.

On the other hand, the LPFL is activated when the reactor water level reaches L1, and similarly when the drywell pressure high signal is simultaneously output with a time delay of 30 seconds after reaching L1, an automatic depressurization system (ADS). After depressurizing the reactor, water is injected into the reactor, and it has the function of always maintaining the core flooded. This LPFL also has a residual heat removal function,
Not only decay heat removal after CA but also normal plant shutdown,
It has multiple functions such as pool cooling and containment spray.

The above RCIC, HPCF and LPFL are
Since it is used as ECCS, automatic flow rate adjustment is not performed, and when the start request is satisfied, water is injected into the reactor based on the water injection capacity of the system, and since the water injection capacity is excessive, the reactor water level rises. If it is too much, the operator manually stops it. However, since the RCIC is also a facility used during transition such as reactor isolation, the flow rate can be manually adjusted.

At the time of LOCA, no matter what kind of breakage is assumed, and even if the most severe single failure is assumed, exposure of the core should be avoided by injecting water by RCIC or HPCF while the reactor pressure is high. However, when the reactor water level reaches L1 and a drywell pressure high signal is output, ADS
Starts to lower the reactor pressure, and when the reactor pressure falls below approximately 2.8 Kg / cm ² , LPFL can be injected into the reactor, and finally the core is constantly submerged during the entire LOCA period. Maintained.

[0009]

As described above, the conventional water injection system at the time of abnormal operation of a nuclear reactor has the ability to include all events from transient events to accidents, and is highly reliable and highly versatile. It has a functional system configuration, and the safety of the boiling water reactor system can be sufficiently secured.

However, in the conventional equipment, since the high-pressure water injection system is also ECCS, the water injection capacity may become excessive at the time of reactor isolation or LOCA with a small fracture area. In such a case, the operator manually operates the RCIC. It is necessary to stabilize the reactor water level by adjusting the flow rate or by manually stopping and starting the HPCF. Such operator operation does not pose a safety problem, but it is an operator operation in an abnormal state of the reactor, and it is desirable to reduce it as much as possible.

Both the high-pressure water injection system and the low-pressure water injection system are E
Since it has a CCS function, a highly reliable and large capacity emergency power supply is required. Further, ECCS requires a great deal of maintenance work such as a surveillance test during operation and a pre-startup test during regular inspection.

An object of the present invention is to provide a boiling water reactor facility which simplifies the facility of the emergency core cooling system and improves the operability.

Another object of the present invention is to provide a boiling water nuclear reactor facility which simplifies an emergency power source and improves maintainability.

[0014]

To achieve the above object, the present invention provides a reactor isolation cooling system and an emergency core cooling system for supplying cooling water to a reactor pressure vessel at the time of an abnormality, and a reactor pressure. In a boiling water reactor facility including an automatic depressurization system connected to a gas phase portion of a vessel, the automatic depressurization system is set to a first reactor water level lower than a normal operation water level, and only a reactor water level low signal is set. And the emergency core cooling system is started by receiving the reactor water level low signal, and a low pressure injection equipped with a pump having a discharge pressure and a discharge flow rate that does not expose the reactor core. It is composed only of water systems.

Further, the reactor isolation cooling system is started by receiving a reactor water level low signal set to a second reactor water level higher than the first reactor water level and lower than the normal operation water level, In the reactor isolation event, the high pressure water injection system is provided with a pump having a discharge pressure and a discharge flow rate that do not reach the first reactor water level.

In the boiling water reactor facility, preferably, three systems of the low pressure water injection system for the emergency core cooling system are provided, and one system or two systems of the high pressure water injection system for the reactor isolation cooling system are provided.

Preferably, the high pressure water injection system of the reactor isolation cooling system is a regular system.

Further, preferably, a flow rate control valve having an automatic flow rate adjusting function is arranged in the high pressure water injection system of the reactor isolation cooling system.

Further, preferably, the high pressure water injection system pump of the cooling system during reactor isolation is a pump driven by a steam turbine, and a generator is connected to this pump so that electricity generated by the generator is isolated during reactor isolation. Supply to the control system of the cooling system.

[0020]

The automatic depressurization system (ADS) is activated only by the reactor water level low signal set to the first reactor water level lower than the normal operating water level, and the emergency core cooling system (ECCS) is activated.
By receiving only the low reactor water level signal, the low pressure water injection system (LPFL) provided with a pump having a discharge pressure and a discharge flow rate that does not expose the reactor core, If it is not possible to secure stable conditions, the reactor core will always be submerged by promptly depressurizing the reactor with ADS and replenishing with ECCS. Therefore, AD
System for injecting S at high pressure before startup (high-pressure water injection system: R
CIC, HPCF) can be used as a normal system for transient use instead of ECCS, which allows ECCS to be configured only with a system using a pump with a low discharge pressure, and the number of systems is smaller than in the past. Therefore, the boiling water reactor facility can be simplified and the operability can be improved.

Further, by making the high-pressure water injection system a regular system, it is not always necessary to provide an emergency power supply, and it is possible to simplify the equipment such as the emergency power supply and improve the maintenance and inspection. Further, since an emergency power source is not required, it is possible to configure the system by using a drive source other than electric or steam drive, for example, a means such as gas turbine drive, and the system design can be simplified. Even if the cause of reactor isolation is the loss of all AC power, the high-pressure water injection system can continue to operate without expecting electricity from other systems, so the reactor water level can be secured at high pressure. Will improve.

Further, by disposing a flow rate control valve having an automatic flow rate adjusting function in the high pressure water injection system (RCIC), it is possible to enhance the water level maintaining ability during a transition.

Furthermore, the high-pressure water injection system is a pump driven by a steam turbine, a generator is connected to this pump, and the electricity generated by this generator is supplied to the control system, so that the high-pressure water injection system has a self-generating function. The water level can be maintained even when all AC power is lost, and the water level maintenance function can be enhanced.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In FIG. 1, a pressure vessel 4 contains a core 2 loaded with nuclear fuel, and the core output is controlled by inserting and removing a control rod (not shown). Pressure vessel 4
The steam generated in 1 is sent to a turbine (not shown) through the main steam pipe 7, and the steam after driving the turbine is returned to the pressure vessel 4 through a condenser and a water supply pipe (not shown). For the nuclear reactor configured in this way, the emergency core cooling system (E
A CCS) and an automatic depressurization system (ADS) 14 are provided.

ECCS consists of three low pressure water injection systems (LPF
L) 20, the power source and the device configuration are independent of each other. That is, each LPFL 20 has a power supply system including an on-site power supply and an independent emergency power supply 11, and a pump 9 that is connected to the power supply system and sucks cooling water from a water source 12. The pump 9 is a conventional 1350 MW internal pump. In order to prevent temporary exposure of the core in any boiling system reactor breakage or ADS depressurization, the rated discharge pressure should be at least 14 kg / cm ² or more. To do. The discharge flow rate is about 950 m ³ / h at a total head of 120 m, which is the same as the conventional one.
Which corresponds to 50% of the required design flow rate. Also, this L
A heat exchanger is directly connected to the PFL 20 in the same manner as in the conventional example so that residual heat can be removed at the same time when the LPFL is started. Further, each LPFL 20 is equipped with a pneumatically operated (AO) injection valve 8 that opens and closes in response to a low reactor water level signal from the water level gauge 6 to activate the LPFL.

On the other hand, the ADS 14 has a plurality of valves installed on the main steam system pipe 7, is activated only by the reactor water level low signal from the water level gauge 6, and passes through the exhaust pipe 13A to the pressure suppression pool of the containment vessel. The steam in the pressure vessel 4 is discharged.

The low reactor water level signal from the water level gauge 6 for activating the ADS 14 indicates that the first water level L1 is lower than the normal operating water level.
The reactor water level low signal from the water level gauge 6 that activates the injection valve 10 is also set to the same first water level L1.

On the other hand, FIG. 2 shows a cooling system for reactor isolation during cooling according to the present embodiment, which is an original cooling system for reactor isolation (RCIC) 21.
And a backup high pressure water injection system (HPCF) 22. The RCIC 21 includes a turbine 2 connected to the main steam pipe 7, a pump 1 driven by the turbine 2, and an electric drive (MO) flow control valve 8a whose opening is adjusted by a signal from a water level gauge 6. It is configured.
The HPCF 22 is an electrically driven pump 3, a power supply system including a local power supply for supplying power to the pump 3 and a diesel generator 11A, and an electrically driven (MO) flow control valve 8b whose opening is adjusted by a signal from a water level system 6. It consists of and.

As in the conventional case, the RCIC 21 is activated at a second water level L2 set above the first water level L1 and below the normal operation water level during a transition such as reactor isolation, and the discharge of the pump 1 is performed. The flow rate is about 180m ^{3 which} is the same as the conventional one.
/ H. In addition, in the event of a loss of coolant, etc.
It starts at the water level L2 and the cooling water is injected even when the reactor pressure is high.

The HPCF 22 has a third water level L similar to the conventional one set between the first water level L1 and the second water level L2.
It was started at 1.5, and the discharge flow rate of the electrically driven pump 3 was set to have a capacity of about 180 m ³ / h at high pressure (total head 890 m), and at the time of loss of coolant accident, the reactor pressure was the same as RCIC21. The cooling water is injected from the high level. Further, the HPCF 22 also has a function of preventing the water level from lowering in place of the RCIC even if the RCIC 22 does not start during a transition.

Since the RICI 21 and HPCF 22 do not need to be ECCS by installing the above emergency core cooling system, they are constructed as a normal system, and the flow rate control valves 8a and 8b have an automatic flow rate adjusting function as described above. I am making it. In addition to the on-site power source, the diesel generator 11A is connected to the electrically driven pump 3, but the ECCS
It is a diesel generator for safety because it does not have to be.

Next, the operation of this embodiment will be described in comparison with the conventional emergency core cooling system. FIG. 3 shows a system configuration of a conventional emergency core cooling system. The conventional emergency core cooling system consists of three systems of high-pressure water injection system (one system of RCIC30, HPCF3
1 is provided in two systems), a low-pressure water injection system (LPFL32) is also provided in three systems, and each of the high-pressure system and the low-pressure system is connected to the emergency power source 11 and optimized in an independent three-section configuration. Among them, the RCIC 30 is also used as a make-up water system during a transition such as reactor isolation. In these water injection systems, RCIC30 is the second water level L2, HPCF31 is the third water level L1.5, L
The PFLs 32 are each activated at the first water level L1, and are activated sequentially according to the size of the breakage opening. Further, since the above system is basically ECCS, the injection valve 10 does not have a function of automatically adjusting the flow rate, and a predetermined injection amount is injected into the reactor once a start request is made. There is. Therefore, when the injection capacity of the high-pressure water injection system is excessive at the time of a transition such as reactor isolation or when a small LOCA with a small breakage diameter is used, as shown in FIG.
0 or the HPCF 31 is activated and the water level continues to rise even after the water level is restored, and the operator must manually adjust the flow rate or manually stop the operation in order to keep the operation continued.

On the other hand, in this embodiment, the RCIC 21, HP
Since CF22 is not ECCS, it can be equipped with flow rate control valves 8a and 8b having an automatic flow rate adjusting function, and the reactor water level can be promptly changed according to the water level signal of the water level gauge 6 without expecting manual operation by the operator. Held stable to.

Further, in the reactor isolation cooling system, it is difficult to maintain the water level, and the cooling water loss accident (LOC
In the case of A), in the conventional example, even if any single failure is assumed, sufficient cooling water is injected into the furnace by any combination of the high pressure water injection system (RCIC30, HPCF31) and the low pressure water injection system (LPFL32). The LPFL 32 is activated when the reactor water level reaches the first water level L1, and similarly, if the drywell pressure high signal is simultaneously output with a time delay of 30 seconds after reaching the first water level L1, the ADS 14A is activated. After depressurizing the reactor, water is injected into the reactor so that the core can be flooded without being exposed.

In the case of this embodiment, the core is actually flooded by the combination of the high-pressure water injection systems 21 and 22 and the low-pressure water injection system 20 as in the conventional example, but based on the guideline of the safety evaluation of the reactor. High pressure water injection system 21,2 which is not ECCS
Even if the operation of No. 2 is not expected, since the ADS 14 is activated only by the low water level signal of the first water level L1, the injection of the LPFL 20 is started before the core is exposed as shown in FIG. It will always be flooded.

Further, in the conventional example, when the high-pressure water injection systems 30 and 31 cannot perform their predetermined functions at the time of reactor isolation or a very small LOCA, the dry well pressure high signal is not output, and therefore, FIG. 6 is shown. As described above, since the ADS 14A does not automatically start even when the water level reaches the first water level L1, the operator needs to manually start the ADS 14A.
In this embodiment, since the ADS 14 is automatically activated only by the water level signal of the first water level L1, it is not necessary to expect the operator's operation even in such a case.

Furthermore, although it is an extremely rare event,
Even if a scrum signal is generated during a transient, if a scrum failure event (ATWS) occurs, conventionally, an operator manually throttles the feedwater flow rate in order to suppress the reactor output as much as possible,
The water level is controlled, but in this embodiment, ATWS is used.
The water supply can be stopped according to the occurrence, and the water level can be automatically controlled using the RCIC 21.

The second embodiment of the present invention will be described with reference to FIG. In this embodiment, the LPFL 20 has four lines,
At the same time as improving the reliability of the system, since one system is redundant, it is possible to continue operation of the plant even if it becomes inoperative during operation.

A third embodiment of the present invention will be described with reference to FIG. In the present embodiment, the configuration of the emergency core cooling system can be used in either FIG. 1 or FIG. 7, and the RC for driving the pump 1 by the steam turbine 2 in the reactor isolation cooling system is used.
It is composed of an IC 21 and an HPCF 22A for driving the pump 3 by the gas turbine 15. In the case of the present embodiment, since the electrically driven pump is not used, it is possible to eliminate the need for power supply equipment for security as compared with the first embodiment, and it is possible to greatly simplify the power supply system.

A fourth embodiment of the present invention will be described with reference to FIG. In this embodiment, the cooling system for reactor isolation is configured to drive the pump 1 by the gas turbine 15, and the electric drive is set to 1
It is a systematic one. The electrically driven pump 3 is usually driven by a local power source, but a diesel generator 11A is also provided in order to improve the reliability of the power source. However, since it is a regular system, there is no need to use it as an emergency power source, so maintenance and inspection can be simplified. On the other hand, since there is no steam drive, there is no need to introduce drive steam from the main steam system pipe 7.
The main steam system can be simplified. For the emergency core cooling system, either the first or second embodiment may be used as in the third embodiment.

A fifth embodiment of the present invention will be described with reference to FIG. In this embodiment, a small generator 25 is connected to the turbine 2 of the RCIC 21B, and the direct or DC power supply 26 is used.
The electric control system of the RCIC 21 can be supplied via the. As a result, even when all AC power supplies cannot be expected, the electricity supply system does not stop, and reliability can be improved. For this imperfection, either the first or the second embodiment may be used for the emergency core cooling system.

[0042]

According to the present invention, the following effects can be obtained.

(1) The equipment of the emergency core cooling system is simplified and the operability is improved.

(2) Since the functional separation of the water injection system becomes clear, the handling of the system becomes simple.

(3) The capacity of the emergency power supply facility and the number of systems are simplified, and the maintenance and inspection is improved.

(4) In transients and accidents, manual water level control by operators or depressurization operation of the reactor becomes unnecessary,
The reactor will be easy to operate.

(5) Since the water level stabilization at the time of abnormality is performed by automatic control, the water level maintenance performance is improved.

(6) Compared with the conventional system, one or more HPCF lines are not required, and the facility economy is improved.

[Brief description of drawings]

FIG. 1 is a diagram showing an emergency core cooling system of a boiling water reactor facility according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a reactor isolation cooling system of a boiling water reactor facility according to a first embodiment of the present invention.

FIG. 3 is a diagram showing a conventional emergency core cooling system.

FIG. 4 is an explanatory diagram of reactor water level control during an abnormality by the conventional emergency core cooling system.

FIG. 5 is a diagram showing startup of the emergency core cooling system according to the first embodiment of the present invention during LOCA, as compared with a conventional one.

FIG. 6 is a diagram showing a start-up at the time of LOCA in the emergency core cooling system according to the first embodiment of the present invention when a high drywell pressure signal is not output, in comparison with a conventional one.

FIG. 7 is a diagram showing an emergency core cooling system according to a second embodiment of the present invention.

FIG. 8 is a diagram showing a reactor isolation cooling system according to a third embodiment of the present invention.

FIG. 9 is a diagram showing a reactor isolation cooling system according to a fourth embodiment of the present invention.

FIG. 10 is a diagram showing a reactor isolation cooling system according to a fourth embodiment of the present invention.

[Explanation of symbols]

 1 RCIC Pump 2 RCIC Turbine 3 Electric Drive Pump 4 Reactor Pressure Vessel 5 Core 6 Reactor Water Level Meter 7 Main Steam System Piping 8 Flow Control Valve 9 LPFL Pump 10 LPFL Injection Valve 11 Emergency Power Supply 12 Water Source 13 Heat Exchanger 14 ADS 15 Gas Turbine 20 Low Pressure Water Injection System (LPFL) 21 (Reactor Isolation Cooling System) RCIC 22 (High Pressure Water Injection System) HPCF

Claims (6)

[Claims] 1. A reactor isolation cooling system for supplying cooling water to a reactor pressure vessel in the event of an abnormality and an emergency core cooling system, and an automatic depressurization system connected to a gas phase portion of the reactor pressure vessel. In a boiling water reactor facility, the automatic depressurization system is activated only by the reactor water level low signal set to the first reactor water level lower than the normal operation water level, and the emergency core cooling system A boiling water reactor facility characterized by being configured only by a low-pressure water injection system equipped with a pump having a discharge pressure and a discharge flow rate that does not expose the reactor core when the reactor water level low signal is received. . 2. The boiling water reactor facility according to claim 1, wherein the reactor isolation cooling system is set to a second reactor water level higher than the first reactor water level and lower than the normal operation water level. And a high pressure water injection system equipped with a pump having a discharge pressure and a discharge flow rate that are activated upon receiving a reactor water level low signal and do not reach the first reactor water level in a reactor isolation event. Boiling water reactor equipment. 3. The boiling water reactor facility according to claim 2, wherein the low pressure water injection system for the emergency core cooling system is provided in three systems, and the high pressure water injection system for the reactor isolation cooling system is provided in one or two systems. Boiling water reactor facility characterized by being installed. 4. The boiling water nuclear reactor equipment according to claim 2, wherein the high pressure water injection system of the reactor isolation cooling system is a regular system. 5. The boiling water reactor facility according to claim 2, wherein a flow control valve having an automatic flow rate adjusting function is arranged in the high pressure water injection system of the reactor isolation cooling system. Reactor equipment. 6. The boiling water reactor facility according to claim 2, wherein the high pressure water injection system pump of the reactor isolation cooling system is a steam turbine driven pump, and a generator is connected to the pump to generate electricity. A boiling water reactor facility characterized by supplying electricity generated by the machine to the control system of the cooling system during reactor isolation.