JP2019152445A - Abnormality reducing facility for nuclear reactor and method for determining fixing of control rod - Google Patents

Abstract

To provide such an abnormality reducing facility as an ATWS reducing facility which can determine fixing of a control rod while suppressing increase of a repairing cost.SOLUTION: An ATWS reducing facility 31 for performing relaxation processing on the ATWS of the nuclear reactor in a nuclear reactor cooling system includes a control circuit 50, which acquires an output parameter as a parameter related to output of the nuclear reactor cooling system and a breaker open signal output when the nuclear reactor trip breaker is in an open state and determines that the control rod in the nuclear reactor is fixed if the output of the nuclear reactor cooling system is maintained according to the acquired output parameter.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an abnormality mitigation facility for a reactor that performs mitigation measures in the event of an abnormality in a nuclear reactor and a method for determining sticking of a control rod.

  Conventionally, when an abnormal event occurs from when an abnormality occurs in the reactor until the reactor trips, the abnormality is judged, and after the abnormality is judged, mitigation measures such as runback and control rod insertion are performed. A system is known (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 11-030893

  By the way, in the revised new regulatory standards, it is now mandatory to install ATWS mitigation facilities for nuclear plants that are to be restarted. ATWS is an abbreviation for “Anticipated Transient Without Scram”, meaning a reactor trip failure event during abnormal transient changes during plant operation, and ATWS mitigation equipment prevents significant damage to the core when an ATWS event occurs The facility is installed to maintain the soundness of the primary cooling system pressure boundary. Here, one of the causes of ATWS is failure of physical insertion of the control rod due to mechanical sticking of the control rod. When directly detecting the mechanical sticking of the control rod, it can be detected by a control rod position indicating device that detects the position of the control rod, but when used as a part of the ATWS mitigation equipment, It is necessary to ensure the earthquake resistance of the control rod position indicating device. In other words, when a structure that directly detects the mechanical sticking of the control rod is adopted, new equipment is added to realize the structure, earthquake resistance of the equipment is secured, or installation space is secured. It is not realistic because it requires major renovation.

  Accordingly, an object of the present invention is to provide an abnormality mitigation facility for a nuclear reactor and a method for determining sticking of a control rod that can determine whether or not the control rod is stuck while suppressing an increase in repair cost.

  An abnormality mitigation facility for a nuclear reactor according to the present invention is an abnormality mitigation facility for a reactor that performs mitigation measures for an abnormality in a reactor included in a primary cooling system, an output parameter that is a parameter related to the output of the primary cooling system, and a nuclear reactor A circuit breaker signal, which is a signal indicating an open / closed state of a circuit breaker that performs a trip, the acquired circuit breaker signal indicates an open state of the circuit breaker, and from the acquired output parameter of the primary cooling system When the output is maintained, a control unit for determining that the control rod in the nuclear reactor is fixed is provided.

  Further, the control rod sticking judgment method of the present invention is a control rod sticking judgment method executed in a control unit for judging the sticking of the control rod inserted into and removed from the fuel in the nuclear reactor included in the primary cooling system. The sticking of the control rod is determined based on a plant parameter obtained from a detector provided in a nuclear facility including the nuclear reactor, which is different from a detector that detects the behavior of the control rod. In this case, as the plant parameter, an acquisition step of acquiring an output parameter that is a parameter related to the output of the primary cooling system and a circuit breaker signal that is a signal indicating a switching state of a circuit breaker that performs a reactor trip, When the output of the primary cooling system is maintained from the output parameter acquired in the acquisition step, and the acquired circuit breaker signal indicates the open state of the circuit breaker, the control rod in the reactor is fixed. And a sticking determination step of determining

  According to these configurations, normally, when the circuit breaker is opened, the control rod is inserted into the fuel in the nuclear reactor, and the output of the primary cooling system is reduced. However, even if the circuit breaker is open, if the primary cooling system output is maintained (output does not decrease), it can be determined that the control rod is not inserted into the fuel, and the control rod in the reactor is It can be determined that it is fixed. At this time, when determining the sticking of the control rod, it is not necessary to add a device or the like by acquiring the output parameter with an existing detector, so that an increase in the repair cost can be suppressed.

  The primary cooling system includes a steam generator that exchanges heat with the secondary cooling system, and the control unit acquires a water level parameter that is a parameter related to a coolant level in the steam generator. When it is determined from the acquired water level parameter that the coolant level is lower than the preset set water level and it is determined that the control rod in the reactor is fixed, the mitigation measures are It is preferable to output an instructing relaxation signal.

  According to this configuration, when the coolant in the steam generator is less than the set water level and the control rod is fixed, the mitigation measure by the abnormality mitigation facility can be executed. In other words, if the coolant in the steam generator is equal to or higher than the set water level, even if the control rod is fixed, it is possible to appropriately cool the nuclear reactor and to suppress unnecessary mitigation measures.

  Moreover, it is preferable that the said control part has a delay circuit which delays the time after the said circuit breaker open signal is output until it acquires.

  According to this configuration, since the acquisition of the circuit breaker open signal can be delayed by the delay circuit, the transition of the output parameter from when the circuit breaker open signal is output can be waited for the delayed time. it can. In other words, when the breaker open signal is output, the control rod is inserted into the fuel, and after that, the output of the primary cooling system decreases, so the control waits for the time until the output of the primary cooling system decreases. It can be determined whether or not the bar is stuck.

  Further, the output parameter includes a temperature difference between an inflow temperature of the coolant flowing into the reactor and an outflow temperature of the coolant flowing out from the reactor, and a neutron measurement device that measures neutrons generated in the reactor It is preferable that it is at least one of the measured values.

  According to this configuration, since it is possible to use a parameter that is less susceptible to factors other than the sticking of the control rod as the output parameter, it is possible to appropriately determine the sticking of the control rod.

FIG. 1 is a schematic configuration diagram of a nuclear facility according to the present embodiment. FIG. 2 is a configuration diagram around the reactor shutdown device according to the present embodiment. FIG. 3 is a diagram of a control circuit provided in the control device of the abnormality alleviating facility according to this embodiment.

  Embodiments according to the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by this embodiment. In addition, constituent elements in the following embodiments include those that can be easily replaced by those skilled in the art or those that are substantially the same. Furthermore, the constituent elements described below can be appropriately combined, and when there are a plurality of embodiments, the embodiments can be combined.

[This embodiment]
FIG. 1 is a schematic configuration diagram of a nuclear facility according to the first embodiment. A nuclear facility (nuclear facility) 1 has a nuclear reactor 2. As the nuclear reactor 2, for example, a pressurized water reactor (PWR) is used. A nuclear facility 1 using this pressurized water reactor 2 includes a reactor cooling system (primary cooling system) 100 including the reactor 2 and a turbine system (secondary cooling system) 200 that exchanges heat with the reactor cooling system 100. It consists of. In the reactor cooling system 100, a primary coolant flows, and in the turbine system 200, a secondary coolant flows.

  The reactor cooling system 100 has a steam generator 4 connected to the reactor 2 via a cold leg 3a and a hot leg 3b. The hot leg 3b is provided with a pressurizer 5, and the cold leg 3a is provided with a primary coolant pump 6. The reactor 2, the cold leg 3 a, the hot leg 3 b, the steam generator 4, the pressurizer 5, and the primary coolant pump 6 are accommodated in the reactor containment vessel 7.

  The nuclear reactor 2 is a pressurized water nuclear reactor as described above, and the inside is filled with the primary coolant. The primary coolant is light water in which boron used as a neutron moderator is dissolved. In the nuclear reactor 2, a large number of fuel assemblies 8 are accommodated in the reactor vessel 10, and a large number of control rods 9 for controlling the nuclear fission of the fuel assemblies 8 are inserted into and removed from the fuel assemblies 8. It is provided as possible. The control rod 9 is driven in the insertion / removal direction with respect to the fuel assembly 8 by the control rod driving device 20. When the control rod 9 is inserted into the fuel assembly 8 by the control rod driving device 20, the nuclear reaction in the fuel assembly 8 decreases and stops. On the other hand, when the control rod 9 is pulled out by the control rod driving device 20, the nuclear reaction in the fuel assembly 8 increases and becomes a critical state. The control rod drive device 20 is configured to insert the control rod 9 into the fuel assembly 8 when the supply of electric power is cut off and the electric power is lost.

  A series of operations in the reactor cooling system 100 of the nuclear facility 1 will be described. When the fuel assembly 8 is fissioned in the nuclear reactor 2 while controlling the fission reaction by the control rod 9, thermal energy is generated by the fission. When the primary coolant in the nuclear reactor 2 is heated by this thermal energy, the heated primary coolant is sent to the steam generator 4 through the hot leg 3b by the primary coolant pump 6. The high temperature primary coolant passing through the hot leg 3b is pressurized by the pressurizer 5 to suppress boiling, and flows into the steam generator 4 in a state of high temperature and pressure. The high-temperature and high-pressure primary coolant flowing into the steam generator 4 is cooled by exchanging heat with the secondary coolant, and the cooled primary coolant is passed through the cold leg 3a by the primary coolant pump 6 to the nuclear reactor. Sent to 2. Then, the cooled primary coolant flows into the reactor 2, so that the reactor 2 is cooled. Thus, the primary coolant circulates between the nuclear reactor 2 and the steam generator 4.

  The turbine system 200 includes a turbine 12 connected to the steam generator 4 via the steam pipe 11, a condenser 13 connected to the turbine 12, and a water supply pipe 14 connecting the condenser 13 and the steam generator 4. A water supply pump 15 interposed between the two. The turbine 12 is connected to a generator 16.

  A series of operations in the turbine system 200 of the nuclear facility 1 will be described. When steam flows from the steam generator 4 into the turbine 12 via the steam pipe 11, the turbine 12 rotates. When the turbine 12 rotates, the generator 16 connected to the turbine 12 generates power. Thereafter, the steam flowing out of the turbine 12 flows into the condenser 13. The condenser 13 has a cooling pipe 17 disposed therein, and one of the cooling pipes 17 is connected to a water intake pipe 18 for supplying cooling water (for example, seawater). A drain pipe 19 for draining the cooling water is connected to. The condenser 13 cools the steam flowing in from the turbine 12 by the cooling pipe 17, thereby returning the steam to a liquid. The secondary coolant that has become liquid is sent to the steam generator 4 via the water supply pipe 14 by the water supply pump 15. The secondary coolant sent to the steam generator 4 becomes steam again by exchanging heat with the primary coolant in the steam generator 4.

  In addition, the nuclear facility 1 includes a control system 300 that controls the reactor cooling system 100 and the turbine system 200. The control system 300 includes a safety protection system facility 30 and an ATWS mitigation facility (abnormality mitigation facility) 31 in addition to a central control facility (not shown).

  As shown in FIG. 2, the safety protection system 30 controls each device provided in the nuclear facility 1 so that the nuclear facility 1 is safely stopped when an abnormality occurs in the nuclear facility 1.

  FIG. 2 is a configuration diagram around the reactor shutdown device according to the present embodiment. The control system 300 of the nuclear facility 1 has a nuclear reactor stop device 35 that makes an emergency stop of the nuclear reaction of the nuclear reactor 2 assuming that an abnormality occurs in the nuclear reactor 2. The reactor shutdown device 35 includes the safety protection system facility 30, the reactor trip circuit breaker 37, the control rod drive device 20, and the control rod 9.

  The safety protection system 30 is a so-called digital facility equipped with an arithmetic device such as a CPU and a storage device such as an HDD, and by executing various programs stored in the storage device by the arithmetic device, the safety of the nuclear facility 1 It is a facility that can control the protection system. The safety protection system is a functional system having functions of stopping the nuclear reaction of the nuclear reactor 2, cooling the nuclear facility 1, and preventing leakage of radioactive materials from the nuclear facility 1. The safety protection system 30 has a high operation guarantee so that the safety protection system 30 can operate reliably and can operate even in a severe environment.

  Various detection sensors arranged in the nuclear facility 1 are connected to the safety protection system 30, and whether or not an abnormality has occurred in the nuclear facility 1 based on the detection signals output from the various detection sensors. Judging. When the safety protection system 30 determines that an abnormality has occurred in the nuclear facility 1, the safety protection system 30 outputs a reactor trip signal for stopping the reactor 2 to the reactor trip breaker 37.

  The nuclear reactor trip circuit breaker 37 cuts off the electric power supplied to the control rod drive device 20 based on the nuclear reactor trip signal output from the safety protection system facility 30.

  The reactor shutdown device 35 outputs a reactor trip signal from the safety protection system facility 30 to the reactor trip breaker 37. Then, the reactor trip breaker 37 enters an open state in which the power supply is cut off based on the input reactor trip signal, and cuts off the electric power supplied to the control rod drive device 20. When the electric power supplied to the control rod driving device 20 is cut off, the support state of the control rod 9 is released, so that the control rod 9 falls to the fuel assembly 8 by its own weight. Then, when the control rod 9 is inserted into the fuel assembly 8, the nuclear reaction of the fuel is reduced, and the nuclear reactor 2 is stopped.

  The ATWS mitigation facility 31 is a facility that performs mitigation measures for a failure event of a reactor trip that is performed when the nuclear facility 1 is abnormal. The ATWS mitigation facility 31 has a control circuit 50 that detects a failure event. When executing the mitigation measure, the ATWS mitigation facility 31 detects the failure event by the control circuit 50 and executes the mitigation measure corresponding to the detected failure event. Specifically, failure events include failure to open the reactor trip circuit breaker, loss of safety protection facility functions, and physical insertion failure due to mechanical sticking of control rods.

The ATWS mitigation facility 31 receives various plant data and parameters, and the control circuit (control unit) 50 detects a failure event based on the plant data. The plant data input to the ATWS mitigation facility 31 includes a detected temperature T _cold of the primary coolant on the inflow side of the reactor 2, a detected temperature T _hot of the primary coolant on the outflow side of the reactor 2, and a reactor 2 (not shown) Measurement value (NIS) of neutron measuring device provided inside, breaker open signal (breaker signal) which is detection signal of open state of reactor trip breaker 37, detected water level in steam generator 4, auxiliary water supply equipment There is an operation signal etc.

Further, the control system 300 including the ATWS mitigation facility 31 generates various data based on these plant data. The plant data is generated, for example, a detected temperature _{T cold} and the detected temperature _T arithmetic mean is a mean detected temperature Tave of _hot, the detected temperature _{T cold} and the temperature difference ΔT is the difference between the detected temperature _{T hot.} Here, the measurement value (NIS) and the temperature difference ΔT of the neutron measurement apparatus are handled as output parameters of the reactor 2 (reactor cooling system 100) related to the output of the reactor cooling system 100.

  FIG. 3 is a diagram of a control circuit provided in the control device of the abnormality alleviating facility according to this embodiment. In FIG. 3, there are four systems (four loops) in which four steam generators 4 are installed for one nuclear reactor 2. In FIG. 3, the configuration of the four systems is described, but the configuration of the three systems may be used and is not particularly limited. As shown in FIG. 3, the control circuit 50 includes a first control circuit 51 that detects loss of function of the safety protection system facility 30, a second control circuit 52 that detects failure to open the reactor trip breaker 37, And a third control circuit 53 for detecting a physical insertion failure due to mechanical fixation of the rod 9. The control circuit 50 has a circuit breaker open signal, an operation signal of auxiliary water supply equipment, a measurement value (NIS), an output parameter of the reactor 2 such as a temperature difference ΔT, and a use mode using the ATWS mitigation equipment 31 Input values etc. are input.

  The first control circuit 51 includes a first majority circuit 61, a first timer 62, a first NOT circuit 63, a second NOT circuit 64, a first AND circuit 65, an OR circuit 67, and an AND circuit 68. And a first output maintaining circuit 66.

  The first majority circuit 61 receives a water level low (narrow region) signal that is output when the detected water level of the steam generator 4 is lower than a predetermined water level. Since the reactor cooling system 100 that cools the reactor 2 has a four-system (four-loop) configuration with redundancy, four steam generators provided in the four-system reactor cooling system 100 are provided. 4, a low water level (narrow region) signal can be input to the first majority circuit 61. The first majority circuit 61 outputs an abnormality occurrence signal that an abnormality has occurred in the nuclear facility 1 when at least three water level low (narrow) signals among the four inputs are inputted. . In addition, when the reactor cooling system 100 is, for example, three systems, the first majority circuit 61 receives the nuclear facility 1 when at least two water level low (narrow) signals among the three inputs are input. An abnormality occurrence signal is output assuming that an abnormality has occurred.

  The first timer 62 receives the abnormality occurrence signal output from the first majority circuit 61. The first timer 62 is connected in series to the first majority circuit 61 and delays the output of the abnormality occurrence signal input through the first majority circuit 61 by a preset time. That is, the first timer 62 outputs the abnormality occurrence signal when the abnormality occurrence signal is continuously input beyond the set time, while the abnormality occurrence occurs when the input of the abnormality occurrence signal is within the set time. Block signal output.

  The first NOT circuit 63 receives an operation signal related to activation of a water supply pump as an auxiliary water supply device that operates by power of the turbine 12. When the operation signal is input, the first NOT circuit 63 blocks the output of the abnormality occurrence signal from the first NOT circuit 63, assuming that the safety protection system facility 30 is operating. On the other hand, when the operation signal is not input, the first NOT circuit 63 outputs an abnormality occurrence signal that the safety protection system facility 30 is not operating.

  The second NOT circuit 64 receives an operation signal related to activation of a water supply pump as an auxiliary water supply device that is operated by an external power supply or an emergency power supply. When the operation signal is input, the second NOT circuit 64 blocks the output of the abnormality occurrence signal from the second NOT circuit 64, assuming that the safety protection system facility 30 is operating. On the other hand, when the operation signal is not input, the second NOT circuit 64 outputs an abnormality occurrence signal that the safety protection system facility 30 is not operating.

  The first AND circuit 65 receives the abnormality occurrence signal output from the first timer 62, the abnormality occurrence signal output from the first NOT circuit 63, and the abnormality occurrence signal output from the second NOT circuit 64. The first AND circuit 65 outputs an abnormality occurrence signal when all abnormality occurrence signals are input, but does not output an abnormality occurrence signal when any abnormality occurrence signal is not input. That is, when the first AND circuit 65 detects that the water level of the steam generator 4 is abnormal even though the safety protection system 30 is not functioning, the first AND circuit 65 outputs an abnormality occurrence signal.

  The first output maintaining circuit 66 includes an OR circuit 67 and an AND circuit 68. The abnormality occurrence signal output from the first AND circuit 65 is input, and the input value of the use mode of the ATWS mitigation facility 31 is input. . The OR circuit 67 receives an abnormality occurrence signal output from the first AND circuit 65 and receives a mitigation action operation signal output from the AND circuit 68. The OR circuit 67 outputs a mitigation measure operation signal when at least one of the abnormality occurrence signal and the mitigation measure operation signal is input. On the other hand, the OR circuit 67 does not output the mitigation measure operation signal when the abnormality occurrence signal and the mitigation measure operation signal are not input. The AND circuit 68 receives the mitigation measure operation signal output from the OR circuit 67 and the input value of the use mode of the ATWS mitigation facility 31. The AND circuit 68 outputs the mitigation measure operation signal when the mitigation measure operation signal and the input value are input, and outputs the mitigation measure operation signal when at least one of the mitigation measure operation signal and the input value is not input. Do not output. For this reason, as long as the input value of the use mode of the ATWS mitigation facility 31 is inputted, the first output maintaining circuit 66 continues to output the inputted mitigation measure operation signal.

  When the mitigation measure operation signal is output from the first control circuit 51, the ATWS mitigation facility 31 operates a water supply pump as an auxiliary water supply device. As described above, when the first control circuit 51 detects the loss of function of the safety protection system facility 30, the ATWS mitigation facility 31 executes the mitigation measure for the ATWS based on the mitigation measure operation signal.

  The second control circuit 52 includes a third NOT circuit 71, a second timer 72, a second AND circuit 73, and a second output maintaining circuit 74.

  The third NOT circuit 71 receives a circuit breaker open signal from the safety protection system 30. When the circuit breaker open signal is input, the third NOT circuit 71 does not output the abnormality occurrence signal from the third NOT circuit 71 and the circuit breaker open signal is input, assuming that the reactor trip circuit breaker 37 is activated. If not, the abnormality trip signal from the third NOT circuit 71 is output on the assumption that the reactor trip breaker 37 is not operating.

  The second timer 72 uses the abnormality occurrence signal output from the first majority circuit 61 of the first control circuit 51, and this abnormality occurrence signal is input. The second timer 72 is connected in series to the first majority circuit 61, and delays the output of the abnormality occurrence signal input through the first majority circuit 61 by a preset time. In other words, the second timer 72 outputs an abnormality occurrence signal when an abnormality occurrence signal is continuously input beyond the set time, while an abnormality occurs when the abnormality occurrence signal is input within the set time. Block signal output.

  The second AND circuit 73 receives the abnormality occurrence signal output from the third NOT circuit 71 and the abnormality occurrence signal output from the second timer 72. The second AND circuit 73 outputs an abnormality occurrence signal when all abnormality occurrence signals are input, and does not output an abnormality occurrence signal when any abnormality occurrence signal is not input. That is, when the second AND circuit 73 detects that the water level of the steam generator 4 is abnormal even though the reactor trip breaker 37 is not in the open state, the second AND circuit 73 outputs an abnormality occurrence signal.

  The second output maintaining circuit 74 has the same configuration as the first output maintaining circuit 66, includes an OR circuit 67 and an AND circuit 68, and receives an abnormality occurrence signal output from the second AND circuit 73. The input value of the use mode of the ATWS mitigation facility 31 is input. Note that the second output maintaining circuit 74 has the same configuration as the first output maintaining circuit 66, and thus the description thereof is omitted. And as long as the input value of the use mode of ATWS mitigation equipment 31 is inputted, the 2nd output maintenance circuit 74 continues outputting the inputted mitigation measure operation signal.

  The third control circuit 53 includes a second majority circuit 81, a third timer (delay circuit) 82, a third AND circuit 83, a third majority circuit 84, a fourth AND circuit 85, And a three-output maintaining circuit 86. The second majority decision circuit 81 and the third majority decision circuit 84 are configured when the reactor cooling system 100 has four systems, like the first majority decision circuit 61. When the furnace cooling system 100 has three systems, a configuration corresponding to the three systems may be used.

  The second majority circuit 81 outputs an output abnormality when the measured value (NIS) or the temperature difference ΔT as an output parameter of the reactor 2 is abnormal, that is, when the output of the reactor 2 does not decrease. A signal is input. When measured values (NIS) are used as reactor output parameters, a plurality of output abnormality signals based on a plurality of measured values (NIS) output from a neutron measuring device provided in the reactor 2 are Input to the deciding circuit 81 is possible. Further, when the temperature difference Δ is used as the output parameter of the nuclear reactor 2, a plurality of output abnormality signals based on the temperature difference ΔT obtained from the four reactor cooling systems 100 having redundancy are displayed. Input to the decision circuit 81 is possible. Then, the second majority circuit 81 outputs an abnormality occurrence signal assuming that an abnormality has occurred in the nuclear facility 1 when at least three output abnormality signals among the four inputs are inputted.

  The third timer 82 receives a circuit breaker open signal from the safety protection system facility 30. The third timer 82 delays the output of the input circuit breaker open signal by a preset set time. That is, the third timer 82 outputs the circuit breaker open signal when the circuit breaker open signal is continuously input beyond the set time, while the circuit breaker open signal is input within the set time. The circuit breaker open signal is not output.

  The third AND circuit 83 receives the abnormality occurrence signal output from the second majority circuit 81 and the circuit breaker open signal output from the third timer 82. In the third AND circuit 83, when the abnormality occurrence signal and the circuit breaker open signal are input, even if the reactor trip circuit breaker 37 is in the open state, the output of the reactor 2 is abnormal (does not decrease). An abnormality occurrence signal is output assuming that the control rod 9 is stuck. On the other hand, the third AND circuit 83 does not output the abnormality occurrence signal when at least one of the abnormality occurrence signal and the circuit breaker open signal is not input.

  The third majority circuit 84 receives a water level low (wide area) signal that is output when the detected water level of the steam generator 4 is lower than a predetermined water level. Note that the water level low (wide area) signal can also be input to the third majority circuit 84 corresponding to the four steam generators 4 in the four systems, similarly to the water level low (narrow area) signal. Then, the third majority circuit 84 outputs an abnormality occurrence signal that an abnormality has occurred in the nuclear facility 1 when at least three water level low (wide area) signals among the four inputs are inputted.

  The fourth AND circuit 85 receives the abnormality occurrence signal output from the third AND circuit 83 and the abnormality occurrence signal output from the third majority circuit 84. The fourth AND circuit 85 outputs an abnormality occurrence signal when all abnormality occurrence signals are input, and does not output an abnormality occurrence signal when any abnormality occurrence signal is not input.

  The third output maintaining circuit 86 has the same configuration as the first output maintaining circuit 66 and the second output maintaining circuit 74, includes an OR circuit 67 and an AND circuit 68, and outputs an abnormality output from the fourth AND circuit 85. The generation signal is input and the input value of the use mode of the ATWS mitigation facility 31 is input. Note that the third output maintaining circuit 86 has the same configuration as the first output maintaining circuit 66 and the second output maintaining circuit 74, and thus description thereof is omitted. And as long as the input value of the use mode of ATWS mitigation equipment 31 is inputted, the 3rd output maintenance circuit 86 continues outputting the inputted mitigation measure operation signal.

  The control circuit 50 also includes a first OR circuit 54 to which the mitigation measure operation signal output from the second control circuit 52 and the mitigation measure operation signal output from the third control circuit 53 are input. The first OR circuit 54 outputs a mitigation measure operation signal when at least one of the alleviation measure operation signals is input. On the other hand, the first OR circuit 54 does not output the mitigation measure operation signal when all the mitigation measure operation signals are not input among all the mitigation measure operation signals.

  When the mitigation measure operation signal is output from the first OR circuit 54, the ATWS mitigation facility 31 performs a turbine trip operation or performs a closing operation of a steam isolation valve (not shown) provided in the steam pipe 11. To do. Thus, when the second control circuit 52 detects that the reactor trip breaker 37 has failed to open, the ATWS mitigation facility 31 executes the mitigation measures for the ATWS based on the mitigation measure operation signal. Further, when the third control circuit 53 detects a physical insertion failure due to the mechanical sticking of the control rod, the ATWS mitigation facility 31 executes the mitigation measures for the ATWS based on the mitigation measure operation signal.

  As described above, the control circuit 50 acquires the output parameter of the nuclear reactor 2 and the circuit breaker open signal from the safety protection system facility 30 when detecting the physical insertion failure due to the mechanical fixation of the control rod 9. (Acquisition process). The acquired output parameters and plant parameters such as the circuit breaker open signal are different from the parameters for directly detecting the behavior of the control rod 9. Thereafter, the control circuit 50 obtains the circuit breaker open signal and determines that the control rod 9 in the reactor 2 is fixed when the output of the reactor 2 does not decrease from the output parameter (sticking determination step). ). When the control circuit 50 detects a physical insertion failure due to mechanical sticking of the control rod 9, the control circuit 50 executes a mitigation measure for the ATWS.

  As described above, according to this embodiment, the physical insertion failure due to the mechanical sticking of the control rod 9 based on the output parameter of the reactor 2 and the circuit breaker opening signal from the safety protection system facility 30 is prevented. Can be detected. At this time, in determining whether the control rod 9 is fixed, it is not necessary to add a device by acquiring the output parameter with an existing detector.

  Moreover, according to this embodiment, when the water level in the steam generator 4 is less than the set water level and the control rod 9 is fixed, the mitigation measures by the ATWS mitigation facility 31 can be executed. In other words, if the water level in the steam generator 4 is equal to or higher than the set water level, even if the control rod 9 is fixed, the reactor 2 can be appropriately cooled, and execution of unnecessary mitigation measures can be suppressed. it can.

  In addition, according to the present embodiment, since the acquisition of the breaker open signal can be delayed by the third timer 82, the transition of the output parameter of the reactor 2 from when the breaker open signal is output is delayed. You can wait for the amount of time you let me. That is, when the circuit breaker open signal is output, the control rod 9 is inserted into the fuel assembly 8, and thereafter, the output of the reactor cooling system 100 decreases, so the output of the reactor cooling system 100 decreases. It is possible to determine whether or not the control rod 9 is fixed by waiting for the time until.

  In addition, according to the present embodiment, by using the measured value (NIS) or the temperature difference ΔT as the output parameter, it is possible to make it difficult to receive factors other than the sticking of the control rod 9. Adherence can be appropriately determined.

DESCRIPTION OF SYMBOLS 1 Nuclear power plant 2 Reactor 3a Cold leg 3b Hot leg 4 Steam generator 5 Pressurizer 6 Primary coolant pump 7 Containment vessel 8 Fuel assembly 9 Control rod 10 Reactor vessel 11 Steam pipe 12 Turbine 13 Condenser 14 Feed pipe DESCRIPTION OF SYMBOLS 15 Water supply pump 16 Generator 20 Control rod drive device 30 Safety protection system equipment 31 ATWS mitigation equipment 35 Reactor stop device 37 Reactor trip circuit breaker 50 Control circuit 51 First control circuit 52 Second control circuit 53 Third control circuit 54 First OR circuit 61 First majority circuit 62 First timer 63 First NOT circuit 64 Second NOT circuit 65 First AND circuit 66 First output maintaining circuit 67 OR circuit 68 AND circuit 71 Third NOT circuit 72 Second Timer 73 Second AND circuit 74 Second output maintaining circuit 81 Second majority circuit 82 Third timer Ma 83 third AND circuit 84 third majority circuit 85 fourth AND circuit 86 the third output maintaining circuit

Claims (6)

In the nuclear reactor anomaly mitigation facility that performs mitigation measures for reactor anomalies included in the primary cooling system,
An output parameter that is a parameter related to the output of the primary cooling system and a circuit breaker signal that is a signal indicating a switching state of a circuit breaker that performs a reactor trip are acquired, and the acquired circuit breaker signal is an open state of the circuit breaker And a control unit that determines that the control rod in the reactor is fixed when the output of the primary cooling system is maintained from the acquired output parameter. Anomaly mitigation equipment. The primary cooling system includes a steam generator that exchanges heat with the secondary cooling system,
The control unit obtains a water level parameter that is a parameter related to a coolant level in the steam generator, and determines that the coolant level is less than a preset set water level from the acquired water level parameter. The abnormality mitigation facility for a reactor according to claim 1, wherein when it is determined that the control rod in the reactor is fixed, a mitigation signal instructing the mitigation measure is output.   The reactor abnormality mitigation facility according to claim 1, wherein the control unit includes a delay circuit that delays a time from when the circuit breaker open signal is output until acquisition.   The output parameter is measured by a neutron measuring device that measures a temperature difference between an inflow temperature of the coolant flowing into the reactor and an outflow temperature of the coolant flowing out of the reactor, and neutrons generated in the reactor. The abnormality mitigation facility for a nuclear reactor according to any one of claims 1 to 3, wherein at least one of the values is set. A control rod sticking judgment method executed in a control unit for judging sticking of a control rod inserted into and removed from fuel in a nuclear reactor included in a primary cooling system,
A control rod that determines sticking of the control rod based on a plant parameter obtained from a detector provided in a nuclear facility including the nuclear reactor, which is different from a detector that detects the behavior of the control rod. Sticking judgment method. An acquisition step of acquiring, as the plant parameter, an output parameter that is a parameter related to the output of the primary cooling system, and a circuit breaker signal that is a signal representing a switching state of a circuit breaker that performs a reactor trip,
When the output of the primary cooling system is maintained from the output parameter acquired in the acquisition step, and the acquired circuit breaker signal indicates the open state of the circuit breaker, the control rod in the reactor is fixed. 6. The method for determining sticking of a control rod according to claim 5, wherein a sticking judging step for judging that the control rod is present.

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