JPH1130693A - Transient relaxation system for nuclear reactor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid a scram and relax the subsequent behavior of a parameter even in the case of scram by judging abnormality at the time of the generation of an abnormal even from the generation of abnormality to a nuclear reactor up to the scram of the nuclear reactor, making a recalculating pup run back immediately after judgment, and inserting a selective control rod. SOLUTION: A container pressure signal a1 is taken into a judging circuit 20. The judging circuit 20 passes the input signal a1 through a timer 31 to obtain a container pressure signal a2 t-seconds before. Pressure deviation of difference between the detected container pressure signal a1 and the container pressure signal a2 t-seconds before is computed by an adder-subtractor 32. This pressure deviation is judged by a judging element 33, and in the case where deviation continues to exist for specified time, a container pressure increase signal a3 is outputted. A recirculating pump 16 is made to run back using this pressure increase signal a3, and a selective control rod is inserted in a nuclear reactor 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power generation plant in general, and more particularly to a boiling water nuclear power plant, and more particularly to the mitigation of a transient phenomenon from an abnormal occurrence to a scram. , A system that also mitigates post-scram transients.

[0002]

2. Description of the Related Art FIG. 3 shows a main system of a nuclear power plant.

[0003] In a nuclear power plant at the time of rated output operation, the steam generated in the reactor 1 passes through the turbine 3 via the main steam pipe 2 and is generated by the generator 4 connected to the turbine 3. I have. The steam after passing through the turbine 3 is returned to water by the condenser 5, pressurized by the low-pressure condensate pump 14 and the high-pressure condensate pump 15, and returned to the reactor by the feedwater pump 6. This loop maintains the rated power operation of the nuclear power plant.

If an abnormality occurs during the normal operation, a means for activating the recirculation pump run-back function by a signal shown in FIG. 4 to alleviate the abnormality is provided.
The signals shown in FIG. 4 will be described below.

[0005] A signal having a recirculation discharge valve opening of 90% or less is used to detect that the valve at the outlet of the recirculation pump 16 in the recirculation loop of the nuclear reactor has been closed. The flow rate from the circulation pump 16 is reduced to prevent the recirculation pump 16 from being damaged.

The operation of the power load unbalance relay is as follows.
This is a signal for detecting a difference between the output of the reactor 1 and the load of the generator 4, and is a signal generated when a power transmission line or the like is cut. Since this power load unbalance relay has a risk of reaching the overspeed of the main turbine 3, the reactor 1 is scrammed, the recirculation pump 16 is run back, and the reactor water level after the scram is maintained stable.

Similarly, the scram signal is also an interlock for keeping the reactor water level stable after the scram.

When the water level of the condenser 5 drops, the main turbine 3 trips, and a reactor scram occurs.
The recirculation pump 16 is run back to keep the reactor water level stable after the scram.

[0009] A signal at a low supply water flow and a reactor water level L4 or lower is an interlock for preventing a reactor scram due to a decrease in the reactor water level, and raises the reactor water level by a recirculation pump runback.

The above-mentioned interlocks are provided in the existing power plant. Based on these interlocks, in the scram avoidance integrated control system (Japanese Patent Application Laid-Open No. 61-160088), when the process value reaches a certain set value, it is reset. A function is built to run back the circulation pump and insert a selection control rod.

Using the above interlock, the plant behavior at the time of the following event will be described.

(1) When the Containment Vessel Pressure Increases In the event that steam leaks into the containment vessel 7, the containment vessel pressure gradually increases. For example, when steam leaks from the main steam pipe 2 shown in FIG. 3 at the point x, the pressure in the containment vessel 7 rises as shown in FIG. 5 (dotted line), and then the containment vessel pressure high alarm is set. The value f is reached and a containment pressure high alarm is issued. At that time, the operator confirms the occurrence of the alarm, and at time h immediately after the time of the alarm generation, performs an operation to manually run back the recirculation pump 16 to reduce the reactor power. If the leakage of steam continues thereafter, the pressure in the containment vessel 7 further rises, reaches the scram set value g, and the reactor 1 scrams.

The manual run-back operation by the operator of the recirculation pump 16 is a means for reducing the reactor power to about 40% and relaxing the behavior of the reactor water level and pressure after scram. As shown in FIG. 4, the current interlock of the recirculation pump runback does not correspond to the case where the pressure of the containment vessel 7 rises. And an increase in the pressure of the storage container 7 is suppressed.

However, the pressure in the containment vessel 7 at the run-back start time point h at which the operator starts to run back the recirculation pump 16 manually is a value immediately before the scram set value g is reached. Even if the back is started, the reactor output is close to the rated value, so the pressure drop cannot be completed in time, reaches the scram set value g, and reaches the reactor scram i. As described above, when the pressure in the containment vessel 7 rises, the operator cannot respond in time, so that not only does the scram occur, but also an ECCS activation signal is generated, and a recovery response operation in the event of an accident is required. .

(2) When the pool water temperature in the pressure suppression chamber rises In the event that the relief safety valve is stuck open, the pool water temperature in the pressure suppression chamber rises. For example, when the release safety valve 8 shown in FIG. 3 is stuck open, the steam from the nuclear reactor is guided to the suppression chamber 9, and the pool water temperature in the suppression chamber 9 rises. In the case of such an event, as shown in FIG. 6, when the pool water temperature of the pressure suppression chamber 9 reaches the water temperature high alarm set value m, an alarm is generated.
The operator detects that the pool water temperature is high. Thereafter, the operator manually runs back the recirculation pump 16 at 1 to reduce the reactor power and reduce the mismatch between the steam flow rate and the feed water flow rate. As a result, the outflow of steam from the relief safety valve 8 is reduced, and the rise of the pool water temperature in the pressure suppression chamber 9 is reduced.

If this operation is not performed, or if the operation cannot keep up, the flow rate of steam corresponding to 100% output flows from the relief valve 8 to the pressure suppression chamber 9, so that the flow rate of water supply is equal to the flow rate corresponding to 100% output. Try to hold. Further, as shown in FIG. 7, the water level of the condenser 5 decreases with the maintenance of the supply water flow rate, so that the low-pressure condensate pump 14 and the high-pressure condensate pump 15 shown in FIG. In addition, with these trips, the water supply pump 6 also trips, leading to a total loss of water supply. When the condenser 5 water level falls, the recirculation pump 16 runs back due to the condenser water level interlock shown in FIG. 3, but the reactor water level drops rapidly and the automatic In addition to the scram, it is necessary to secure the water level by using a cooling system when the reactor is isolated.

(3) Condenser Vacuum Degree When the circulating water pump 10 trips, the condenser vacuum degree drops. For example, when the circulating water pump 10 shown in FIG. 3 trips and the degree of vacuum of the condenser 5 decreases, as shown in FIG. Is output. In such a case, the operator causes the recirculation pump to run back at time s. However, when the degree of vacuum of the condenser 5 is close to the set value of the trip of the turbine 3, the condenser reaches the condenser vacuum low / low set value q and reaches the turbine trip u. Further, due to the turbine trip, the main steam stop valve 12 shown in FIG. 3 is closed to reach the reactor scram. Further, since the turbine bypass valve does not open, heat removal by the condenser 5 cannot be performed. As a result, the water level of the condenser 5 also drops, leading to a total loss of water supply.

As described above, in the case where the relief safety valve 8 is stuck open and the case where the degree of vacuum of the condenser is lowered, the scrum causes the event to spread to the total water supply loss and the turbine trip event, respectively.

In order to detect these abnormalities and mitigate the event, it is necessary to reduce the reactor power. As a method of reducing the reactor power, in addition to a method of reducing the recirculation flow rate, a control rod is used. There is a means to insert. The means for inserting the control rod is a function added from the viewpoint of avoiding the core from becoming in an unstable area when the recirculation pump is tripped, and is called a selective control rod. The operation logic of this function is shown in FIG. The selected control rod has a reactor power of 3
It operates when 5% or more is detected and one or more recirculation pumps are tripped. When the above three events occur, the logic of the selection control rod does not trip because the recirculation pump does not trip, so that the support cannot be expected.

In order to solve such an event, a comprehensive scrum avoidance control system (Japanese Patent Application Laid-Open No. 61-160088) discloses a plant process amount such as APRM,
When the heat flux or the like becomes an appropriate value, the recirculation pump run-back and the selection control rod are inserted. Therefore, at the time of the above event, the process values, that is, the PCV pressure, the S / P water temperature, and the condenser vacuum are monitored, and the recirculation pump run-back and selection control rod insertion are performed before reaching the alarm set value. Let me.

[0021]

As described above, in the integrated scrum avoidance control system, when the process amount of the plant, for example, the APRM, the heat flux, etc. becomes an appropriate value, the recirculation pump run back and the selection control rod Insertion is being performed.

However, when the recirculation pump runback and the selection control rod are inserted with the set values, the fluctuation due to the abnormality cannot be detected in the early stage of the occurrence of the abnormality, and the corresponding control may not be performed in time.

In the case of the detection set value, a malfunction due to an erroneous signal of the detector is considered. In particular, when a process amount such as a reactor water level is detected, the reactor water level greatly fluctuates when the plant is started or stopped, and a malfunction may occur in this case.

When an impulse-like erroneous signal due to disturbance is input and reaches a set value, a malfunction occurs,
Since this is operated when it is not necessary, the output is reduced due to malfunction in operating the plant, which is not preferable.

An object of the present invention is to solve the above problem by detecting an abnormality at an early stage of an event using the abnormal parameter before reaching the scrum, and immediately running the recirculation pump. Back and insert a selection control rod to avoid scrum. Moreover, it is an object of the present invention to provide a system that does not cause a malfunction due to an error signal of the detector. Another object of the present invention is to provide a system that can alleviate the subsequent parameter behavior even when scrum is performed.

[0026]

SUMMARY OF THE INVENTION It is an object of the present invention to determine a deviation of a parameter fluctuating due to an abnormality from a steady value, and to output a determination signal when the deviation continues, and a recirculation pump based on the determination output. And a means for inserting a selection control rod.

Further, the object of the present invention is to provide a means for causing a recirculation pump to run back or a means for inserting a selection control rod, wherein the judgment output is such that the reactor is operating and a scram signal of the reactor is input. At least one of not
Achieved by having one logic.

According to the above-mentioned means, the fluctuation due to the abnormality can be detected in the early stage of the abnormality by monitoring the deviation of the parameter indicating the abnormality from the steady value. Thus, before the parameter indicating the abnormality reaches the scram set value, when the deviation from the steady value is output, the recirculation pump is run back and the selection control rod is inserted to avoid the reactor scram.

By monitoring that the deviation of the parameter indicating the abnormality from the steady-state value continues for a predetermined time or more, the parameter indicating the abnormality may fluctuate temporarily due to a detection error or disturbance. This disturbance can be eliminated by observing the duration of the deviation, thereby preventing unnecessary run-back of the recirculation pump and malfunction of insertion of the selection control rod. The tendency of the parameter change can also be determined based on the duration of the deviation.

When the recirculation pump is run back and the selective control rod is inserted, the rated output is not output when the plant is started and stopped. Therefore, it is not necessary to run back the recirculation pump. Runback and insertion of the selection control rod can be prevented by adding a condition that the reactor is operating and that no scram signal is input.

[0031]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the logic of an embodiment of the present invention. The present invention is applied by adding the new logic shown in FIG. 1 to the conventional logic (see FIG. 4). Hereafter, in nuclear power plants, 3
The following describes a case where the present invention is used with respect to two events.

(1) When the Containment Vessel Pressure Increases An event that the pressure signal in the containment vessel 7 increases may be caused by leakage from the main steam pipe 2 in the containment vessel 7. For example, assume a steam leak at a point X of the main steam pipe in FIG. FIG.
As shown in FIG. 7, the pressure in the storage container 7 gradually increases due to the vapor leakage. In this case, the existing container pressure signal a1 is detected by the existing signal detector a shown in FIG. The detected containment vessel pressure signal a1 is taken into the determination circuit 20. In the judgment circuit 20, the input containment vessel pressure signal a
1 through the timer 31 to the containment vessel pressure signal a2 t seconds ago.
Get. The storage container pressure high deviation of the difference between the detected storage container pressure signal a1 and the detected storage container pressure signal a2 t seconds ago is calculated by the adjuster 32. Next, the storage container pressure high deviation is determined by the determiner 33, and if there is a deviation, a storage container pressure high increase signal a3 is output, and an operation command for recirculation pump runback and selection control rod insertion is output.

As shown in FIG. 2, details of the decision unit 33 are as follows. A deviation from the adder / subtractor 32 in FIG. 1 is judged by a deviation judging unit 41. If there is a deviation, a clock pulse is gated 42 and stored in a counter 43. A preset counter is used as the counter 43, and when the counter value reaches the initially set counter value, the storage container pressure high increase signal a3 is output. If the deviation determiner 41 determines that there is no deviation during the counting of the counter 43, the counter 43 is reset and no signal is output. When the containment vessel pressure high increase signal a3 is output, an operation command for the recirculation pump runback and selection control rod insertion is output. According to the containment container pressure increase signal a3, malfunction due to an erroneous signal can be prevented.

In the present invention, since it is a precondition that the recirculation pump is run back before the reactor scrams, the reactor scram signal w1 is not inputted.
And the reactor mode switch makes a determination based on the logic using the signal w2 of the "operation" position, and if the containment vessel pressure high increase signal a3 is output, the recirculation pump 16 is run back h1 as shown in FIG. At the same time, the selection control rod is inserted under the same conditions.

The runback of the recirculation pump and the insertion of the selection control rod can suppress the pressure in the storage container (solid line), and can avoid scrum. Further, the reactor output can be reduced by the runback of the recirculation pump and the insertion of the selection control rod. By setting the reactor power in a reduced state, even if the scram is performed, the behavior of the subsequent parameters can be reduced.

In addition, even when the above-mentioned vapor leakage in the containment vessel is large and the parameter fluctuates rapidly and reaches the scrum, the present invention can also output the fluctuating parameter, in this case, the deviation of the pressure in the containment vessel. At that time, the recirculation pump is immediately run back and the selection control rod is inserted as in the case where the pressure in the storage container increases over time immediately. As a result, the reactor power before the scram can be reduced, so even if a reactor scram occurs due to a sudden change in parameters, the reactor power is reduced in advance, so the reactor water level after the scram , The change in pressure is alleviated.

(2) When the pool water temperature in the suppression chamber 9 rises The events in which the pool water temperature in the suppression chamber 9 rises include:
There is an event in which the relief safety valve 8 sticks while being opened. In this event, the main steam flow rate also flows out to the pressure suppression chamber 9, so that a large supply water flow rate must be secured. If an attempt is made to maintain a flow rate corresponding to 100% output as the feed water flow rate, the water level of the condenser 5 shown in FIG. 3 drops, and the low-pressure condensate pump 14 and the high-pressure condensate pump 15 trip in this order. Since the water supply pump 6 also trips, the total water supply is lost. When the water level in the condenser 5 drops, the recirculation pump runs back in time with the condenser water level low as shown in FIG. 4 but cannot catch up with it. At the same time, it is necessary to secure the water level by using a cooling system at the time of reactor isolation.

In order to avoid this automatic scrum, in the present invention, an existing signal detector b shown in FIG. 3 detects the pressure suppression chamber pool water temperature signal b1. The detected pressure suppression chamber pool water temperature signal b1 is taken into the determination circuit 21 shown in FIG. The determination circuit 21 obtains a pressure suppression chamber pool water temperature signal b2 t seconds ago through the timer 34 based on the input pressure suppression chamber pool water temperature signal b1. The controller 35 calculates the difference between the detected pressure suppression chamber pool water temperature signal b1 and the pressure suppression chamber pool water temperature signal b2 t seconds before the pressure suppression chamber water temperature high deviation.
Calculate with. Next, the pressure suppression chamber pool water temperature high deviation is determined by the determiner 36, and if there is a deviation, a pressure suppression chamber water temperature high increase signal b3 is output, and the recirculation pump run back and the operation command for selection control rod insertion are issued. Is output.

2 is used as the decision unit 36. The difference between the pressure suppression chamber pool water temperature signal b1 calculated by the regulator 35 and the pressure suppression chamber pool water temperature signal b2 t seconds before is shown in FIG. When there is a deviation, the clock pulse is gated 42 and counted by the counter 43, and the continuation of the presence of the deviation is observed. A water temperature high increase signal b3 is output. This outputs an operation command,
Activate recirculation pump runback and selective control rod insertion.

In the present invention, since it is a precondition that the reactor operates before the scram, the reactor scram signal w1
Is not input, and the reactor mode switch determines based on the logic using the signal w2 of the “operation” position, and when the above-described pressure suppression chamber water temperature high increase signal b3 is output,
As shown in FIG. 6, the recirculation pump 16 is run back 11 and the selection control rod is inserted under the same conditions. As a result, the temperature of the pressure suppression chamber pool water maintains the normal operation state (solid line). Further, as shown in FIG. 7, the power supply and the condensate pump do not trip (solid line), and the reactor power can be reduced.

When the opening of the relief valve is large, the S / P water temperature rises sharply and the main steam pressure decreases due to a decrease in the reactor power. Is likely to lead to a scrum. Therefore, even when the S / P water temperature, the reactor pressure, or the main steam pipe pressure fluctuates and reaches scram, according to the present invention, the recirculation pump is immediately run when the deviation of the fluctuating parameter is output. At the same time, the control rod is inserted. As a result, the reactor power before the scram can be reduced, so even if a reactor scram occurs due to a sudden change in parameters, the reactor power is reduced in advance, so the reactor water level after the scram , The change in pressure is alleviated.

(3) When the Degree of Vacuum in the Condenser is Reduced As an event that the degree of vacuum in the condenser 5 is lowered, a trip of the circulating water pump 10 can be considered. Also in this case condenser 5
The main turbine trip is prevented by incorporating the vacuum degree signal into the logic.

In order to discover this state, the operator is notified by an alarm that the degree of vacuum of the condenser 5 is reduced. If the operator performs a response earlier than manually reducing the output, the operator will trip the turbine during the response operation, leading to the reactor scram. Further, since the turbine bypass valve does not open, heat removal by the condenser 5 cannot be performed. As a result, the water level in the condenser also drops, leading to a total loss of water supply.

According to the present invention, the condenser signal c1 is detected by the existing signal detector c shown in FIG. 3 in order to avoid the loss of the reactor scram and the total supply water. The detected condenser vacuum degree signal c1 is taken into the determiner 22 shown in FIG. The determiner 22 obtains a condenser vacuum signal c2 t seconds before the input condenser vacuum signal c1 through the timer 37. The difference between the detected condenser vacuum signal c1 and the condenser vacuum signal c2 t seconds before is calculated by the adjuster 38. The condenser vacuum degree low deviation is determined by the determiner 39, and if there is a deviation, a condenser vacuum degree low decrease signal c3 is output, and an operation command for recirculation pump run-back and selection control rod insertion is output. .

2 is used as the decision unit 39. The difference between the condenser vacuum signal c1 calculated by the adder 38 and the condenser vacuum signal c2 t seconds before is shown in FIG. As a result of the determination by the determiner 41, if there is a deviation, the clock pulse is gated 42, and the continuation of the presence of the deviation is observed by counting with the counter 43. c3 is output. As a result, an operation command is output, and the recirculation pump runback and the selection control rod insertion are operated.

In the present invention, since it is a precondition that the reactor is operated before the scram, the reactor scram signal w
1 is not input, and the reactor mode switch determines based on the logic using the signal “w2” of the “operation” position,
When the condenser vacuum degree decrease / decrease signal c3 is output, the recirculation pump 16 is run back s1 as shown in FIG. 8, and the selection control rod is inserted under the same conditions.

As described above, according to the present invention, each event can be dealt with at the initial stage when an abnormal event occurs, so that it is possible to prevent the operator from delaying the response and spreading the event. Further, even when the reactor scrams due to a sudden change in parameters, the reactor output can be reduced in advance, so that transient changes after the scram can be mitigated.

When a plurality of circulating water pumps are stopped, the degree of vacuum of the condenser begins to rapidly decrease, leading to a turbine trip. Along with this, the reactor scrams. For this reason, even when the condenser vacuum degree suddenly decreases and reaches the scrum, according to the present invention, at the time when the deviation of the fluctuating parameter is output, the recirculation pump is run back and the selection control rod is moved. Insert. As a result, the reactor power before the scram can be reduced, so even if a reactor scram occurs due to a sudden change in parameters, the reactor power is reduced in advance, so the reactor water level after the scram , The change in pressure is alleviated.

The events leading to the reactor scram are other than those described above, and there are a plurality of composite events. The present invention can be applied to any event.

Although the deviation criterion unit 41 uses 0 as a criterion, it may be based on a set value of 0 or more. Other circuits can be used to determine the continuation of the presence of the deviation.

[0052]

As described above, according to the present invention, abnormal events can be dealt with at the early stage of occurrence, and the following effects can be expected.

For an event in which the pressure in the containment vessel increases, the rise and change in the pressure in the containment vessel can be detected at the beginning of the event by the high pressure increase signal. As a result, the run-back of the recirculation pump and the insertion of the selection control rod can be achieved in the early stage of the occurrence of the abnormal event, and the reactor can be put into a low power state to reduce the increase in the pressure of the containment vessel. In addition, a scram can be avoided, and even if a scram occurs, the reactor power is reduced, so that the burden on the operator is reduced and erroneous operation can be prevented.

Further, when the containment vessel pressure high deviation continues, the containment vessel pressure increase signal is used as the run-back of the recirculation pump and the insertion signal of the selection control rod. Malfunctions of recirculation pump runback and insertion of the selection control rod can be prevented.

In the event that the release safety valve is stuck open, the rise in the pool water temperature in the pressure suppression chamber can be detected at the beginning of the event by a high water temperature increase signal, and the degree of vacuum in the condenser decreases. The event can be detected at the beginning of the event by the condenser vacuum reduction signal, and the corresponding control can make the reactor power low and avoid the scram.

Further, it is possible to prevent a malfunction of the recirculation pump run-back and the insertion of the selection control rod due to an erroneous signal.

Further, even if an automatic scram is performed due to a sudden change in parameters, the reactor output is reduced due to the recirculation pump run-back and the insertion of the selective control rod. Slows down.

[Brief description of the drawings]

FIG. 1 is a logic diagram of one embodiment of the present invention.

FIG. 2 is a partial configuration diagram of a determination circuit of FIG. 1;

FIG. 3 is a configuration diagram of a nuclear power plant.

FIG. 4 is a logic diagram of a recirculation pump run-back function and selection control rod insertion of a conventional nuclear power plant.

FIG. 5 shows a conventional behavior when the pressure of the containment vessel increases and a trend graph in the case of the present invention.

FIG. 6 shows a conventional behavior when the water temperature of the pressure suppression chamber rises and a trend graph in the case of the present invention.

FIG. 7 is a graph showing a conventional behavior of a water supply flow rate when the water temperature of the pressure suppression chamber increases, and a trend graph in the case of the present invention.

FIG. 8 shows a conventional behavior when the degree of vacuum of the condenser is reduced and a trend graph in the case of the present invention.

[Description of Signs] 1 ... reactor, 2 ... main steam pipe, 3 ... turbine, 4 ... power generator, 5 ... condenser, 6 ... water supply pump, 7 ... container, 8 ...
Escape relief valve, 9: pressure suppression chamber, 10: circulating water pump,
11: Main steam isolation valve, 12: Main steam stop valve, 13: Main steam control valve, 14: Low pressure condensate pump, 15: High pressure condensate pump, 16: Recirculation pump, 20: Containment vessel pressure judgment circuit, Reference numeral 21: a circuit for determining the temperature of the water in the pressure suppression chamber, 22: a circuit for determining the degree of vacuum of the condenser, 31, 34, 37: a timer, 32,
35, 38 ... adder / subtractor, 33, 36, 39 ... determiner, 41
... Deviation determiner, 42. Clock pulse gate, 43. Counter, a. Containment vessel pressure detector, a1. Containment vessel pressure signal, a2. Containment vessel pressure signal t seconds ago, a3. b: Suppression chamber pool water temperature detector, b1: Suppression chamber pool water temperature signal, b2: Suppression chamber pool water temperature signal t seconds ago, b3: Suppression chamber pool water temperature high increase signal, c: Recovery Water vacuum detector, c1 ...
Condenser vacuum degree signal, c2 ... t seconds before condenser vacuum degree signal,
c3: Condenser vacuum lowering signal, d: Containment vessel pressure in reactor rated operation state, e: Steam leak occurrence time, f: Containment vessel pressure high alarm set value, g: Containment vessel pressure high scrum set value , H ... time point of the recirculation pump runback of the operator, h1
... System recirculation pump run-back and selection control rod insertion time, i ... Reactor scram time, j ... Pressure suppression chamber water temperature in reactor rated operation state, k ... Evacuation safety valve open sticking occurrence, l ... Operator At the time of the recirculation pump runback, l
1 ... Recirculation pump run back of the system and selection control rod insertion point, m ... High water temperature alarm set value in pressure suppression chamber, n ...
High and low water temperature setting values in the pressure suppression chamber, o: Condenser vacuum degree in reactor rated operation state, p: Condenser vacuum degree low alarm setting value,
q: condenser vacuum low / low set value, r: circulating water pump trip point, s ... operator recirculation pump run back point, s
1 ... At the time of system recirculation pump runback and insertion of selective control rod, u ... At the time of turbine trip.

Claims (7)

[Claims] In a system for mitigating a transient phenomenon from occurrence of an abnormality in a reactor to a reactor scram, a deviation from a steady value of a parameter fluctuating due to the abnormality is determined, and a determination signal is output based on continuation of the presence of the deviation. A transient mitigation system for a nuclear reactor, comprising: means for outputting a recirculation pump based on the determination output; means for causing a recirculation pump to run back; and means for inserting a selection control rod. 2. The transient mitigation system for a nuclear reactor according to claim 1, wherein the means for judging a deviation of the parameter from a steady-state value includes adding a timer, and determining a difference between the steady-state value and the parameter value at the time of extracting the timer. A transient mitigation system for a nuclear reactor, wherein a deviation is determined. 3. A transient mitigation system for a nuclear reactor according to claim 1, wherein said means for judging a deviation of said parameter from a steady-state value includes:
A containment vessel pressure signal two seconds ago is obtained, and a containment vessel pressure high deviation is calculated based on the detected containment vessel pressure signal and a containment vessel pressure signal t seconds ago, and the containment vessel pressure high deviation is determined. A transient mitigation system for a nuclear reactor, which outputs a containment vessel pressure high increase signal when the above is continued. 4. The transient mitigation system for a nuclear reactor according to claim 1, wherein the means for judging a deviation of the parameter from a steady-state value includes: Get the room pool water temperature signal,
Calculate the pressure suppression chamber pool water temperature high deviation from the detected pressure suppression room pool water temperature signal and the pressure suppression room pool water temperature signal t seconds ago, determine the pressure suppression room pool water temperature high deviation, and determine if there is a deviation. A transient mitigation system for a nuclear reactor, which outputs a signal for increasing the water temperature of the suppression pool when the pressure has continued for more than an hour. 5. The transient mitigation system for a nuclear reactor according to claim 1, wherein the means for determining a deviation of the parameter from a steady-state value includes a condenser vacuum signal through a timer.
A condenser vacuum degree signal before the second is obtained, and a condenser vacuum degree low deviation is calculated based on the detected condenser vacuum degree signal and the condenser vacuum degree signal before t seconds, and the condenser vacuum degree low deviation is calculated. A transient mitigation system for a nuclear reactor, wherein a deviation is determined, and a condenser vacuum degree reduction signal is output when a deviation continues for a predetermined time or more. 6. The transient mitigation system for a nuclear reactor according to claim 1, wherein the means for causing the recirculation pump to run back includes a condition that the scram signal of the reactor is not input to the judgment output of the judgment means. A transient mitigation system for a nuclear reactor, comprising logic for at least one of the conditions that the reactor mode switch is in an operating position. 7. The reactor transient mitigation system according to claim 1, wherein the means for inserting the selection control rod includes a condition that a scram signal of the reactor is not input to the judgment output of the judgment means. A transient mitigation system for a nuclear reactor, comprising logic for at least one of the conditions that the mode switch is in the operating position.