JP4922679B2 - Control rod pull-out monitoring device - Google Patents

Description

  The present invention relates to a control rod withdrawal monitoring device that monitors a withdrawal operation of a control rod of a boiling water reactor.

  In a boiling water reactor (BWR), the reactor power is controlled by the flow rate of cooling water (hereinafter referred to as the core flow rate) and the insertion / extraction of control rods. For example, if a certain control rod is excessively pulled out due to an erroneous operation, the reactor power will rise rapidly locally, and the fuel cladding tube (hereinafter abbreviated as fuel) constituting the fuel rod may be thermally damaged. There is. In order to prevent such fuel damage, the nuclear reactor plant is provided with a control rod withdrawal monitoring device that monitors the withdrawal of the control rod.

  The control rod pull-out monitoring device outputs an LPRM signal output by detecting a neutron flux from a local output region monitor (hereinafter referred to as LPRM) arranged at various locations in the reactor, and a core flow rate detector in the reactor. The control rod pull-out is monitored based on the core flow rate signal and the position signal indicating the coordinate position of the operation control rod output from the control rod operation monitoring device (hereinafter referred to as RC & IS).

  In such a configuration, when a control rod to be operated is first selected, an LPRM signal around the control rod selected by a position signal from RC & IS is selected, and control rod pull-out monitoring is performed based on the LPRM signal. A control rod monitoring value to be used (hereinafter referred to as RBM value) is calculated. On the other hand, based on the core flow rate signal from the core flow rate detector, a control rod withdrawal prevention set value (hereinafter referred to as RBL value) using the core flow rate as a variable is calculated.

  Next, the RBL value and the RBM value are compared in a comparator. For example, when the control rod is excessively pulled out due to a malfunction of the operator, and the RBM value rises to reach the RBL value, the control rod is prevented from being pulled out. A signal is output to RC & IS. When the RC & IS receives the control rod withdrawal prevention signal, the RC & IS outputs a control rod stop request signal to the control rod drive device and stops the withdrawal of the control rod.

  In such a control rod pull-out monitoring device, normally, a plurality of RBL values (for example, three) are prepared. When the RBM value reaches the RBL value and the control rod pull-out is stopped, for example, the RBL value is set. An RBL value setup function is provided for switching to a higher level and releasing control rod withdrawal prevention.

  As an example of a control rod pull-out monitoring device, for example, a technique for improving the detection performance of output increase due to operation of a control rod by using an LPRM detection signal selected from a predetermined combination among a plurality of LPRMs is disclosed. (See Patent Document 1).

  In addition, when the RBL value setup function works for one control rod, it is possible to manually set up another control rod having a reactor power level lower than the RBL value and within a predetermined range. A technique for reducing the number of setups is disclosed (see Patent Document 2).

JP 57-136197 A JP 2000-162356 A

  By the way, in the conventional control rod pull-out monitoring device, a plurality of RBL values calculated based on the core flow rate are all set in the vicinity of the rated output of the reactor, and the RBL values are not requested to be changed by the operator. As long as it is a fixed value.

  Therefore, when the reactor power is in a low power state, for example, when an adverse condition such as malfunction due to the operator pulling out the control rod overlaps and the RBM value rises rapidly, the control rod It is conceivable that the extraction is not stopped and a part of the fuel becomes thermally intense due to a local increase in output.

  As described above, from the viewpoint of fuel protection, it is desired to appropriately determine the RBL value of each output region condition and manage the RBM value from the low output state to the rated output state. In this regard, in the conventional control rod pull-out monitoring device, for example, there is room for improvement in monitoring of control rod pull-out in a low output state.

  The present invention provides a control rod operation that suppresses a local power increase associated with a control rod pull-out operation and enables a safer reactor operation in an operation region from a low power state to a rated power state of a nuclear reactor. It is an object to provide a monitoring device.

In order to solve the above problems, a control rod pull-out monitoring device according to the present invention includes a neutron flux detector for detecting a neutron flux around the control rod, and a neutron flux signal output from the neutron flux detector. The local output signal processing unit for calculating the control rod monitoring value of the control rod, the first control rod withdrawal prevention set value obtained based on the reactor core flow rate and the control rod monitoring value are compared, and the control rod monitoring value Is obtained by adding the set value to the first stop means for stopping the pulling operation of the control rod and the control rod monitoring value of the current control rod when the first control rod withdrawal prevention set value is reached. When the control rod monitoring value reaches the second control rod withdrawal prevention setting value by comparing the second control rod withdrawal prevention setting value and the control rod monitoring value of the subsequent control rod axial position, And a second stop means for stopping the operation of pulling out the control rod.

  According to this, in addition to the first stopping means using the first control rod withdrawal prevention set value (first RBL value) determined based on the core flow rate, the set value is set to the current control rod monitoring value. The second stopping means using the second control rod pull-out prevention set value (second RBL value) determined by addition can be used in combination. That is, for example, when the control rod monitoring value (RBM value) is in the low output state, the control rod pull-out is monitored using the second stopping means, while when the control rod monitoring value is near the rated output state, the first stopping means is Since double monitoring can be performed using the second stopping means, safer reactor operation can be realized.

  In this case, when the driving operation of the control rod is stopped by the second stopping means, the second control rod withdrawal prevention set value is updated based on the newly calculated control rod monitoring value, and the control rod It is preferable to provide a function for canceling the stop of the driving operation.

  Further, the second stopping means is provided with monitoring means for simultaneously monitoring the driving operations of the selected control rods.

  According to the present invention, in the operation region from the low power state of the nuclear reactor to the rated power state, it is possible to suppress a local increase in output due to the operation of pulling out the control rod, thereby realizing a safer reactor operation.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram for explaining an example of a control rod pull-out monitoring system for a nuclear reactor to which the present invention is applied.

  The control rod withdrawal monitoring device of the present embodiment monitors the control rod operation of a boiling water reactor, and includes a conventional control rod withdrawal monitoring device 101 and a control rod withdrawal monitoring auxiliary device 1 which is a feature of the present invention. Each is arranged independently, and the pulling of the control rod 103 in the nuclear reactor 102 is double monitored.

  The control rod withdrawal monitoring device 101 and the control rod withdrawal monitoring auxiliary device 1 are each electrically connected to the RC & IS 108, and the RC & IS 108 is electrically connected to the control rod drive mechanism 116.

  A plurality of fuels 104 and control rods 103 are arranged in the core of the nuclear reactor 102, and a plurality of LPRMs 105 are evenly arranged around the fuel 104 and the control rod 103 as shown in FIG. The LPRM 105 outputs a signal obtained by detecting the neutron flux in the furnace as a local output. A plurality of core flow rate detectors 111 for detecting the core flow rate are arranged in the core.

  The control rod 103 is inserted and pulled out along the axial direction by the control rod driving mechanism 116 controlled based on a command from the RC & IS 108, and the axial position, that is, the insertion depth is changed. When the insertion depth of the control rod 103 changes, the local power of the core changes, and the local power is detected by the LPRM 105.

  LPRM signals 118-1 to 118-n output from the LPRM 105 and control rod operation signals 9, 117 output from the RC & IS 108 are input to the control rod pull-out monitoring auxiliary device 1 and the control rod pull-out monitoring device 101 for control. A core flow rate signal 119 output from the core flow rate detector 111 is input to the rod withdrawal monitoring device 101.

  The control rod pull-out monitoring device 101 calculates an RBM value and an RBL value based on the LPRM signals 118-1 to 118-n and the core flow rate signal 119, respectively, and compares them to determine whether or not the control rod 103 is stopped. Judging. On the other hand, the control rod pull-out monitoring auxiliary device 1 calculates an RBM value and an RBL value based on the LPRM signals 118-1 to 118-n and compares them to determine whether or not the control rod 103 is stopped. .

  In such a configuration, for example, when the control rod 103 is excessively pulled out due to an erroneous operation by an operator or the like, and there is a risk of the fuel 104 being damaged due to a rapid increase in local power in the reactor 102, At least one of the control rod withdrawal monitoring auxiliary device 1 and the control rod withdrawal monitoring device 101 outputs control rod withdrawal prevention signals 8 and 114 to the RC & IS 108.

  When the RC & IS 108 receives at least one of the control rod withdrawal prevention signals 8 and 114, the RC & IS 108 outputs a control rod stop request signal 115 to the control rod drive mechanism 116 to stop the control rod withdrawal.

  In this embodiment, in addition to the conventional control rod withdrawal monitoring device 101, the control rod withdrawal monitoring auxiliary device 1 is provided independently, so that control can be performed in any operating region of the reactor from the low power state to the rated power state. The increase in the power output of the nuclear reactor due to the rod drawing can be suppressed to a predetermined range. This makes it possible to improve the control rod pull-out monitoring capability in the low power state of the nuclear reactor as compared with the control rod pull-out monitoring of the conventional control rod pull-out monitoring device 101 alone. In addition, since the control rod withdrawal monitoring auxiliary device 1 and the conventional control rod withdrawal monitoring device 101 can perform double control rod withdrawal monitoring even in the vicinity of the rated output of the reactor, the control rod withdrawal monitoring is higher than before. Ability can be realized.

  Hereinafter, the conventional control rod withdrawal monitoring device 101 and the control rod withdrawal monitoring auxiliary device 1 will be described in detail.

  The control rod pull-out monitoring apparatus 101 includes an LPRM signal processing unit 107, an RBL computing unit 110, a comparator 113, and a man-machine interface (hereinafter referred to as MMI) 120.

  In the control rod withdrawal monitoring device 101, the fuel from the LPRM 105 is used to prevent the fuel 104 from being damaged due to excessive withdrawal of the control rod 103 due to, for example, an operator's erroneous operation, and a rapid increase in the local output of the reactor 102. The LPRM signals 118-1 to 118-n in the reactor relating to the generation of heat quantity 104, the core flow signal 119 from the core flow detector 111, and the control rod operation signal 117 from the RC & IS 108 are input.

  Since the control rod withdrawal monitoring device 101 uses the LPRM signal around the control rod 103 to be subject to withdrawal monitoring, the central portion of the nuclear reactor 102 is adjacent to the periphery of one control rod 103 4. The LPRM signals of three or two LPRM assemblies 106 are input to one LPRM assembly 106, that is, the LPRM signals of 16 LPRMs 105 and the periphery of the reactor wall of the reactor 102. The LPRM assembly 106 refers to a group of LPRMs 105 arranged in parallel to the axial direction of the control rod.

  In the process of selecting the LPRM signal around the selected control rod among the LPRM signals 118-1 to 118-n, the LPRM signal processing unit 107 receives the control rod operation signal 117 from the RC & IS 108, and the micro in the LPRM signal processing unit 107 An arithmetic unit represented by a processor performs the operation by selecting the LPRM signal around the selected control rod among the LPRM signals 118-1 to 118-n from the control rod operation signal 117. The LPRM signal processing unit 107 performs calculation processing on the LPRM signal selected for control rod pull-out monitoring, and calculates an RBM value 109. The RBM value 109 is updated every calculation cycle of the LPRM signal selection unit 107.

  The RBL computing unit 110 receives the core flow rate signal 119 from the core flow rate detector 111 of the nuclear reactor 102, and calculates the RBL 112 having the core flow rate as a function based on the core flow rate signal 119.

  The calculated RBM value 109 and RBL value 112 are input to the comparator 113. The comparator 113 compares the RBM value 109 with the RBL value 112, and when the RBM value 109 reaches the RBL value 112 by pulling out the control rod, outputs a control rod pullout prevention signal 114 to the RC & IS 108. When the RC & IS 108 receives the control rod withdrawal prevention signal 114, the RC & IS 108 outputs a control rod stop request signal 115 to the control rod drive mechanism 116, and the control rod drive mechanism 116 stops the control rod withdrawal.

  The control rod pull-out monitoring device 101 has a plurality of RBL values 112 (usually three) in the RBL computing unit 110. For example, if there is an RBL setup request 121 by an operator's request in the MMI 120, It has a function of switching to the RBL value. For this reason, when the RBM value 109 reaches the RBL value 112 and the control rod is prevented from being pulled out, the setup request 121 is used to set up an upper RBM value to exclude the control rod withdrawal prevention. However, the highest RBM value cannot be set up.

  This RBL setup function is an extended function of the control rod withdrawal monitoring device 101, which monitors the RBM value 109 and the core flow rate signal 119 calculated by the LPRM signal processing unit 107, and the control rod withdrawal monitoring device 101 performs RBL setup by itself. The RBL value 112 is changed without the operator's operation from the MMI 120.

  When the reactor power is lowered with the control rod inserted, the control rod withdrawal monitoring device 101 monitors the RBM value 109 and the core flow rate signal 119, sets the RBL value by itself, and sets the lower RBL. Can be changed to a value.

  Next, the control rod withdrawal monitoring auxiliary device 1 will be described.

  The control rod withdrawal monitoring auxiliary device 1 is provided independently of the control rod withdrawal monitoring device 101 and constructs a double control rod withdrawal monitoring system.

  FIG. 2 is a block diagram for explaining the signal processing contents of the control rod withdrawal monitoring auxiliary device 1 of FIG.

  The control rod pull-out monitoring auxiliary device 1 includes an LPRM signal processing unit 2, an adder 5, a comparator 7, and an MMI 10.

  LPRM signals 118-1 to 118-n output from LPRM 105 and control rod operation signal 9 output from RC & IS 108 are constantly input to LPRM signal processing unit 2 for control rod pull-out monitoring.

  When the control rod 103 to be operated is selected, the control rod withdrawal monitoring auxiliary device 1 monitors LPRM signal processing by an arithmetic processing unit represented by a microprocessor in the LPRM signal processing unit 2 in order to monitor the control rod withdrawal. The LPRM signal 118-1 to 118-n input to the unit 2 has a function of selecting an LPRM signal around the selection control rod.

  In the LPRM signal processing unit 2, the selected LPRM signal is averaged and corrected to calculate an RBM value, and the calculation cycle of the LPRM signal processing unit 2 (a cycle that does not interfere with the control rod pull-out monitoring. For example, 100 ms. ) Is updated every time and control rod pull-out is monitored in real time.

  The LPRM signal processing unit 2 stores the RBM value at the time when the control rod 103 is selected among the calculated RBM values in the memory as the RBM initial value 4-1, and outputs it to the adder 5, and then The RBM value 4-2 calculated every calculation cycle is output to the comparator 7.

  The adder 5 includes an RBM initial value 4-1 output from the LPRM signal processing unit 2 and, for example, a ΔRBM value 11 (for example, an RBM initial value 4-1) set by the ΔRBM setting function 13 of the MMI 10 by an operator. RBL value 6 is calculated by adding 3 to 7% of the above and the RBL value 6 is output to the comparator 7.

  When the RBL value 6 is input, the comparator 7 compares the RBM value 4-2 with the RBL value 6, and when the RBM value 4-2 reaches the RBL value 6, the control rod pull-out prevention signal is sent to the RC & IS 108. 8 is output. When the control rod withdrawal prevention signal 8 is input, the RC & IS 108 outputs a control rod stop request signal 115 to the control rod drive mechanism 116, and the control rod drive mechanism 116 stops the control rod withdrawal.

  The LPRM signal processing unit 2 has a function of monitoring the control rod withdrawal even when the operation control rod is changed or the withdrawal / insertion operation is changed. For example, when an operation control rod is changed, if the control rod operation signal 9 output from the RC & IS 108 is input and it is recognized that the operation control rod has been changed, the LPRM signal used for monitoring the control rod pull-out is converted into the LPRM signal. A selection is made again from 118-1 to 118-n, the RBM initial value stored in the memory in the LPRM signal processing unit 2 is updated, and the RBM initial value 4-1 and the RBM value 4-2 are updated. Here, the new RBL value 6 is set by adding ΔRBM to the RBM initial value 4-1 at the start of control rod extraction or insertion.

  Further, the control rod pull-out monitoring auxiliary device 1 simultaneously inputs a plurality of control rod operation signals 9 to the LPRM signal processing unit 2 so that a plurality of control rod pull-out monitorings can be simultaneously handled. It has a function of selecting an LPRM signal and calculating a plurality of independent RBM initial values 4-1 and RBM values 4-2.

  In this case, the adder 5 calculates an RBL value 6 for each of a plurality of independent RBM initial values 4-1, and outputs the RBL value 6 to the comparator 7. When the RBL value 6 is input, the comparator 7 individually compares the RBM value 4-2 and RBL value 6 of each control rod. When any RBM value 4-2 reaches the RBL value 6, By outputting the control rod withdrawal prevention signal 8 to the RC & IS 108, a plurality of operated control rod withdrawals are stopped.

  According to the control rod pull-out monitoring auxiliary device 1 of the present embodiment, when the reactor power is in a low output state, for example, even if the RBM value suddenly increases due to a malfunction caused by the operator pulling out the control rod, the RBM initial stage The RBM value can be managed with the RBL value 6 obtained by adding ΔRBM to the value 4-1 as the upper limit set value. As a result, the change in the RBM value can be detected more appropriately, the control rod can be pulled out, and the safety of the reactor operation can be improved.

  Also, when control rod withdrawal is prevented in the control rod withdrawal monitoring auxiliary device 1, the RBM value is updated according to the operator's request in the control rod withdrawal prevention exclusion function 3 of the MMI 10 in order to ensure the operability of the nuclear reactor. The signal 12 is output to the LPRM signal processing unit 2, the RBM initial value 4-1 stored in the memory of the LPRM signal processing unit 2 is updated, and the RBL value 6 is updated in the adder 5 accordingly. . As a result, the control rod can be continuously pulled out. In this case, the control rod withdrawal prevention exclusion function 3 sends the control rod withdrawal prevention signal 8 to the control rod withdrawal prevention exclusion function 3 so that the RBM value update signal 12 is output only when the control rod withdrawal prevention signal 8 is output. It is designed to be entered.

  As described above, in this embodiment, by adopting the control rod withdrawal monitoring auxiliary device 1, the reactor power range of the control rod withdrawal monitoring is changed from the low power state to the rated output only from the vicinity of the conventional rated power region. Since the power can be expanded to any power range in the state, the increase in the power output of the nuclear reactor due to the pulling of the control rod can be suppressed to a predetermined range. Then, by constructing a double control rod extraction monitoring system independently of the conventional control rod extraction monitoring device 101, more safe reactor operation can be realized.

  Further, even if the control rod withdrawal monitoring assisting device 1 is prevented from being pulled out, the control rod withdrawal prevention can be excluded at the request of the operator via the MMI 10, so that the conventional operability of the nuclear reactor can be eliminated. Can be secured.

  In the present embodiment, the control rod pull-out monitoring device 101 and the control rod pull-out monitoring auxiliary device 1 are arranged side by side to perform double control rod pull-out monitoring. If the control rod pull-out monitoring auxiliary device 1 has the function, the output increase of the reactor due to the control rod pull-out can be suppressed to a predetermined range in any output range from the low power state to the rated power state, which is safer Highly reliable reactor operation can be realized.

It is a block diagram explaining an example of the control rod pull-out monitoring system of the nuclear reactor formed by applying the present invention. It is a block diagram explaining the signal processing content of the control-rod extraction monitoring auxiliary | assistance apparatus of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Control rod withdrawal monitoring auxiliary device 2,107 LPRM signal processing unit 3 Control rod withdrawal prevention exclusion function 4-1 RBM initial value 4-2,109 RBM value 5 Adder 6,112 RBL value 7,113 Comparator 10,120 Man-machine interface (MMI)
11 ΔRBM value 13 ΔRBM setting function 101 Control rod withdrawal monitoring device 102 Reactor 103 Control rod 104 Fuel 105 LPRM
108 Control rod operation monitoring device (RC & IS)
110 RBL computing unit 111 core flow rate detector 116 control rod drive mechanism 118-1 to 118-n LPRM signal

Claims (3)

In the control rod withdrawal monitoring device that stops the withdrawal operation of the control rod according to the output level of the boiling water reactor,
A neutron flux detector for detecting a neutron flux around the control rod; and a local output signal processor for calculating a control rod monitoring value of the control rod by inputting a neutron flux signal output from the neutron flux detector; ,
The first control rod withdrawal prevention set value obtained on the basis of the reactor core flow rate is compared with the control rod monitoring value, and the control rod monitoring value becomes the first control rod withdrawal prevention set value. First stopping means for stopping the pulling operation of the control rod when reached,
A second control rod withdrawal prevention setting value obtained by adding a set value to the control rod monitoring value of the control rod at the present time, and a control rod monitoring value of an axial position of the control rod thereafter In comparison, the control rod pull-out is further provided with second stop means for stopping the pull-out operation of the control rod when the control rod monitoring value reaches the second control rod pull-out prevention set value. Monitoring device. When the control rod withdrawal operation is stopped by the second stopping means, the second control rod withdrawal prevention set value is updated based on the newly calculated control rod monitoring value, and the control rod 2. The control rod pull-out monitoring device according to claim 1 , wherein the stop of the pull-out operation is released. It said second stop means, the control rod withdrawal monitoring device as claimed in claim 1 or 2, characterized in that it comprises a monitoring means for monitoring the extraction operations of the plurality of control rods which are selected simultaneously.

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