JPS60173495A - Protective device for nuclear reactor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a boiling water reactor (hereinafter referred to as BWR) in which water supply is interrupted for some reason.

[This invention relates to a nuclear reactor protection device that safely and reliably shuts down a nuclear reactor when an abnormal situation occurs in which the degree of blackness decreases and control rods are not inserted. [Technical aspect of the invention and its problems] In a nuclear couplant, when an abnormal transient state or an erroneous operation by a vehicle operator occurs during operation, a nuclear reactor protection system that shuts down the reactor by fully inserting the control rods is provided. The equipment is set up. In a BWR, if an abnormality occurs in the turbine system, the turbine steam stop valve provided at the Coupin inlet of the main steam pipe is suddenly closed, and the steam is cut off, resulting in a turbine trip state. As a result, the pressure inside the BWH increases, and the voids in the core collapse. Since the general KBWR has a negative reactivity coefficient, when the voids are collapsed and reduced, a positive reactivity is given to the reactor and the reactor power increases. As a result, reactor power -1 signal, reactor pressure "high" signal and "turbine trip"
The reactor shutdown system is activated by all or any of the signals, the control rods are fully inserted, and the reactor is shut down. in this case,
When the pressure in the furnace reaches a set value or higher, the turbine steam stopper and the bypass pipe inserted in the bypass pipe that bypasses the turbine and leads to the condenser are opened, and at the same time, the bypass pipe inserted in the main steam pipe is opened. The safety valve does not open, suppressing the rise in pressure in the furnace.
1i11. By the way, when a transient state such as the above-mentioned turbine trip occurs, in case the reactor protection system does not operate due to a failure of the control rod drive system, etc., this system is installed.
A relaxation device is provided separately from the system. This slow-release [] device detects the pressure rise in the reactor, and uses the detected pressure (f=s) to stop the reactor coolant recirculation pump and also starts the neutron poison injection system pump, which is the reactor shutdown system. , when the reactor coolant recirculation pump is stopped, the coolant flow rate in the reactor is reduced to promote its boiling, the increased voids add negative reactivity to the reactor, and the reactor power is reduced. Furthermore, when neutron poison is injected, the reactor output gradually decreases, eventually reaching a shutdown state. In this way, the conventional mitigation device functions as a backup device in response to an abnormal event accompanied by an increase in the pressure of the reactor, even if the reactor shutdown system does not operate for some reason. However, according to recent findings, if an abnormal event occurs that significantly reduces the feed water conductivity to the reactor, which increases the reactor output, the reactor protection system will be activated. It has been found that even if the control rods are not inserted, the pressure inside the reactor will rise and the mitigation device will not operate, and therefore the backup function may not be fully demonstrated. [Purpose of the Invention] The present invention has been made by focusing on the above-mentioned circumstances in the W-1☆ technique, and is designed to ensure backup operation even in the event of an abnormal event such as a significant drop in reactor feed water temperature. The purpose of the present invention is to provide a nuclear reactor protection device that performs the above-mentioned purpose.
A feed water pump tli controller that stops the feed water pump when the temperature of the feed water to the reactor falls below a set value and the reactor output exceeds the set value, and a recirculation pump f that stops the recirculation pump. It is characterized by having any or all of 14 or all of the 'R1' controller and the neutron poison injection system activation signal generator that activates the neutron poison injection system. [Embodiments of the Invention] Below, embodiments of the present invention and their operations will be described with reference to the drawings. FIG. 1 shows a system diagram of a BWR equipped with the device of the present invention, in which a reactor core 3 is housed in a pressure vessel 2 housed within a containment vessel 1. A pJ circulation pump 4 installed in one part of the containment vessel is connected to a jet pump 6 in the pressure vessel 2 via a recirculation loop 5, and recycles the coolant in the reactor. I^ to control the reactor output by increasing or decreasing the flow rate of coolant flowing through the core t'A. The steam generated in the pressure vessel 3 is led to the main turbine 9 through the main steam pipe 7 and the main steam stop valve 8, where it does work and drives the turbine generator field, and then is led to the condenser 11. A bypass pipe 12 is connected between the main steam pipe 7 and the condenser [1], and a bypass valve 13 is inserted in this bypass pipe. has been done. The coolant that has been cooled to water in the condenser 11 is transferred to the water supply pipe 14
The water passes through the demineralizer 15, the feed water heater 16, the feed water temperature detector 17, and the feed water pump 18, and then returns to the pressure vessel 2. A part of the 3s air that has finished driving the main turbine 9 is led to the condensing water heater [6] through the feed water heating steam pipe 19, where it is used as a heat source, and then sent to the 4th water heater [1]. . 20 indicates a neutron poison injection system tank for storing neutron poison such as boric acid water. The neutron poisons in this tank can be pumped through the entire injection pipe 22 by starting the neutron poison injection system pump 2] when the control rod cannot be extended when the reactor needs to be shut down. The neutrons are injected into the reactor core 3, absorbing neutrons and reducing the reactor output. The above-mentioned BWR system is equipped with the following reactor sleep equipment. The output of the feed water temperature detector 17 inserted into the water supply pipe 14 and the output of the feed water temperature low setting 1 direct setting device 23 to which the low feed water temperature setting is set in advance are guided by the feed water temperature comparator 24 and compared. , the output of this comparator U is input to one input terminal of the AND gate 25. On the other hand, a recirculation flow rate detector 26 attached to the recirculation loop 5
detects the amount of recirculated driving water +%, and outputs the detected value to the reactor output high set value setting device 27. This setting device 27 automatically sets the reactor output height set value in accordance with the recirculation drive water flow rate at that point in time. This set value is used together with the reactor power detected by the reactor power detector 28 provided in the reactor core as well as by the reactor power comparator 2.
9 is led to the comparison, and the result is AND gate 2.
It is input to the other input terminal of 5. AND gate 25 determines whether the feed water temperature detected by feed water temperature detector 17 is below the feed water temperature low set value set by setting device 23 and the reactor power detected by reactor power detector 28 is , when the reactor output high set value set by the setting device 27 or more is reached, AND
If the conditions are satisfied, the recirculation pump frill Fl a=
3 (+, outputs the signal (, j) to the water supply pump controller 31 and the neutron poison injection system activation signal generator 32. Upon receiving the signal from the AND gate 25, the recirculation pump controller 30 starts recirculation. The pump 4 is stopped, and the water supply pump controller 31 stops the water supply pump 18. Furthermore, the neutron poison injection system start signal generator 32 starts the neutron poison injection system pump 2 and is closed during normal operation. The injection well 22a is opened and the neutron poison stored in the neutron poison injection system tank 20 is injected into the reactor through the injection pipe 22. Based on the circulating driving water #t and the leaf signal, the reactor output high set value is automatically set from the recirculating driving water flow rate to the core output characteristic k shown in Fig. 2. This configuration is not an essential condition of the present invention, and in some cases, the reactor output high set value may be set to a constant value that does not depend on the recirculation drive water flow rate. The function will be explained. During reactor operation, if an abnormal event occurs that involves a large loss of heating of the feed water, and if for some reason it becomes impossible to insert the control rods, the water supply will be restored. The temperature decreases and the reactor output starts to rise. When the feed water temperature falls below the preset feed water temperature low set value and the reactor power exceeds the reactor output high set value, the feed water The water supply pump 18 stops operating in response to a command from the pump controller 31. As a result, the supply of cooling water to the reactor is stopped, and the void space inside the reactor increases, so the reactor output decreases. Furthermore, when the recirculation pump 4 is stopped by a command from the recirculation pump controller 30, the core flow rate decreases and the reactor output is drastically reduced. When the neutron blue material injection system pump 21 is activated by the command and the injection well 22a is opened, the neutron blue material is injected into the reactor core, giving negative reactivity to the reactor.
The reactor's power decreases and eventually shuts down. In the present invention, from the point of view of safety, it is desirable to have all of the above-mentioned water supply bong wholesale controller, recirculation pump unit, and neutron poison injection system start signal generator installed. , and possibly one or two of the
Alternatively, only e'jG may be performed. Since the nuclear reactor maintenance nail of the present invention functions as described above,
When the reactor output settles to a high output state when an abnormal event occurs, the problem disappears and the reactor can be reliably shut down. Figures 3 to 5 respectively show the above-mentioned effects of the present invention (6) in comparison with the prior art. As is clear from these figures, in the prior art, core #L
However, the present invention has the disadvantage that the amount remains constant regardless of the passage of time (Fig. 3), and the reactor output shifts to a high level as time passes and becomes stable at a high level (Fig. 4). In such cases, the core flow rate decreases rapidly (Figure 3), and the reactor output temporarily increases, but then begins to decline in a short period of time, and then decreases with time and core flow rate decreases (Figure 4, Figure 4). 5
figure). In addition, in a nuclear reactor plant to which the present invention is applied, if the control rod insertion operation is performed normally in the event described above, even if the feed water temperature decreases, the reactor output has already decreased sufficiently. Therefore, the device of the present invention will not operate, and if the cause of the above event is resolved, the plant can be restarted immediately without reducing its operating rate. [Effects of the Invention] As described above, the reactor retention system of the present invention can prevent control rods from being inserted in the event that an abnormal event involving a significant loss of feed water heating occurs during reactor operation. Even if this is not possible, it is possible to quickly reduce the reactor output and safely shut down the reactor by stopping the recirculation pump and feedwater pump and starting the neutron poison injection system. Therefore, the safety of the nuclear reactor and the soundness of the fuel are ensured, and the reliability of the nuclear couplant is greatly improved.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of a BWR system to which the present invention is applied, Fig. 2 is a graph showing a characteristic curve of a reactor output high set value setter,
3 to 5 are graphs showing changes in reactor core flow rate or reactor power in the conventional technology (dashed line) and the present invention (solid line), respectively. 1...Containment vessel, 2...Pressure vessel, 3 river reactor 11? . 4... Internal circulation pump, 5... Recirculation loop, 6...
・Jet pump, 7... Main steam pipe, 8... Main steam stop valve, 9... Main turbine, Io... Turbine photoelectric machine, [1... Double water B, 12... Bypass 1', +3
... Bypass q, +4... Water supply pipe, 15... Desalination device, [6... Feed water heater, 17... Feed water temperature detector, 18... Water supply pump, 19... Feed water heating steam pipe,
20... Neutron poison injection system tank, 21... Neutron poison injection system pump, 22... Injection piping, 22a...
Injection well, 23... Water supply temperature low setting price Uki, 24...
・Water supply IM ratio V device, 25...AND gate, 26・
... Re71^ Recirculation flow rate detector, 27... Reactor output high set value setting device, 28... Reactor output detector, 29...
IJ type sub-reactor output calibrator, 3o... Recirculation pump controller, 31... Feed water pump controller, 32... Neutron poison injection system start signal generator. Applicant's agent Kiyoshi Inomata

Claims (1)

[Claims] 1. In a boiling water reactor, a water supply pump that stops the water pump when the temperature of the water supplied to the reactor does not fall below a set temperature and when the reactor output exceeds a set value. a controller;
A nuclear reactor protection device comprising: a recirculation pump controller that stops a recirculation pump; and a neutron poison injection system start signal generator that starts a neutron poison injection system. A feed water temperature detector installed in the water supply pipe downstream of the inlet feed water heater; A feed water temperature comparator that compares the output of this detector with the output of the feed water temperature low set value setting device; A reactor output detector. a reactor power comparator that compares the output with the output of the reactor power high set value setting device; when the feed water temperature is not below the set temperature and the reactor power exceeds the set value, the feed water temperature comparator and The AND condition is satisfied by the output of the reactor power comparator,
The nuclear reactor according to claim 1, further comprising an AND circuit that sends an output signal to a feed water pump controller, a recirculation pump controller, or a neutron poison injection system activation signal generator. Protective device. 3. The reactor power high set value setter is configured to automatically set the reactor height set value from the recirculation driving water flow rate-core power characteristic based on the signal from the recirculation flow rate detector. A nuclear reactor protection device according to claim 2.