JPS59180493A - Control rod withdrawal monitoring device - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a control rod withdrawal monitoring device for a boiling water nuclear reactor.

[Technical background of the invention and its problems]

The core of a boiling water reactor is constructed as shown in FIGS. 1 to 4. In other words, in the figure! ... is a control rod, which has a cross-shaped cross section.

Four fuel assemblies 2 are loaded around the control rods 1, and a unit cell J as shown in FIG.
...is configured. Furthermore, these unit cells l...
・ is arranged in a lattice shape as shown in Figure 742, and the η-opening core shown in Figure 3 is formed.In addition, one square surrounded by a broken line in Figure 3 is one unit cell. In addition, neutron detector assemblies 4 of the power system (LPRM) are inserted into this reactor core (here, one for every four unit cells J). Inside the neutron detector assembly L... there are four stages in the vertical direction of the reactor core (as shown in Figure 4).
These four neutron detectors 5... are provided. The neutron flux within the reactor core is detected by these neutron detectors 5, and from this neutron flux, the output of the reactor and O.
A power distribution is detected.

By the way, when the above-mentioned control sI... is extracted, if the extraction operation is inappropriate, the output of the reactor core may increase excessively, and the integrity of the fuel may be impaired. For this reason, a control rod withdrawal monitoring device (RBM) is provided that prevents the withdrawal of control rods 1 if the core power increases excessively due to inappropriate control rod operation. When one control rod I to be operated is selected, the withdrawal monitoring device detects the collective weight of four control rods surrounding the selected control rod I as shown in Fig. 4, that is, a total of 16 neutrons. neutron detectors 5... are selected, and the signals from these neutron detectors 5... are averaged to monitor the output of the area surrounded by these neutron detectors 5..., and the output of this area is set to a predetermined value. For example, if the output exceeds 105% of the output before the control rod is operated (this is configured to prevent the control rod l from being withdrawn).

Furthermore, in order to increase reliability, this control rod withdrawal monitoring device is divided into two independent systems, A system and B system. Then, half of the 16 neutron detectors 5... are selected to belong to the A system and 8 each to belong to the A system and B system, and each of the neutron detectors 5... The signals are averaged to determine the output, and if any one of the outputs determined by the A system 2B exceeds the above 105%, withdrawal of the control rod 1 is prevented. Note that the neutron detectors 5 belonging to the broken line in FIG. 3 are indicated by black circles, and the neutron detectors 5 belonging to the B system are indicated by white circles. In addition, if some of these neutron detectors 5... break down, this will exclude this faulty neutron detector and average the signals from the remaining healthy neutron detectors 5... configured to monitor.

By the way, the output distribution in the area surrounded by the neutron detectors 5 is not necessarily uniform. Therefore, if the neutron detector 5... in the high output part fails, ζ
Since this neutron detector is excluded and the signals from the remaining neutron detectors 5 are averaged, an output lower than that of the actual I-sensor is detected. Incidentally, FIG. 5 shows an example of analysis of such characteristics. That is, curve a in FIG. 5 shows the relationship between the amount of control rod withdrawal and the detected output when there is no failure in the neutron detector 5...
%lb is for the case where one neutron detector 5... located in the high output part has failed, and curve C is for the case where two neutron detectors 11 have failed.
It is the same. As is clear from FIG. 5, for example, if two neutron detectors .sigma.. in the high-output section fail, an error of 1 to 2 notches will occur in the amount of control rod withdrawal. Of course, the actual control rod withdrawal monitoring device is divided into two systems, the A system and the B system, as mentioned above, so the A system is used.

Unless such a failure occurs in both systems of system B, there will be no error in preventing control rod withdrawal, but if the control rod withdrawal monitoring device (which is a safety equipment) That is not a good thing.

[Purpose of the invention]

The present invention has been made based on the above circumstances, and its purpose is to ensure that the control rod is accurately prevented from being withdrawn even if the neutron detector -Yl' is out of order. An object of the present invention is to provide a withdrawal monitoring device.

[Summary of the Invention] The present invention provides a neutron detector of a number of plates provided in a reactor core, a control rod to be extracted without selecting a control rod, and 2) a control rod selection circuit for extraction.
The symmetrical control rod selection circuit selects the control rod selected by this extraction control rod selection circuit (this is the control f!1) and the signal from the upper 4C neutron detector selects the extraction control rod. a faulty neutron detector determination circuit for determining a malfunctioning neutron detector among a plurality of neutron detector groups surrounding each of the control rods selected by the control rod selection circuit and the symmetrical control rod selection circuit, and each of the above controls. Specify the control rod at the position IIIR+K where the number of malfunctioning neutron detectors in each group of neutron detectors surrounding each of these control rods is small. fU!I (A'
It is checked whether the withdrawal order of 4"A is the same as the above-mentioned withdrawal position 41, and if the control rod withdrawal order is not according to the above-mentioned withdrawal position rlfi, it outputs the !if information and prevents the control rods from being withdrawn. +11i'i order monitoring circuit and sub-111
When the withdrawal iVA order of 14@ is in accordance with the above-mentioned withdrawal order, it is monitored whether the withdrawal amount of the control rod that is withdrawn from the second or later is less than or equal to the withdrawal 11- of the first control rod operated2. The control rod is equipped with a withdrawal amount monitoring circuit that prevents the withdrawal operation of the control rod when the withdrawal amount of the control rod that is withdrawn from the second control rod exceeds the withdrawal amount of the first control rod operated. Therefore, when the control rod to be operated is selected, the control rod 1613 selects the control rod whose position is symmetrical to the pupil, and the neutron detector group surrounding each control rod is selected. Because of the small number of neutron detectors in This manipulated fti!I (
The withdrawal amount of II salary or less is regulated.

Therefore, the number of out of the 150 control rods that are out of order among the neutron detectors surrounded by the control rods is the smallest, to the extent that the shadows N on the reactor core are mutually symmetrical (this is equivalent). Since the control rod is pulled out first, this control rod is pulled out under accurate pulling q vision, and the second and subsequent control rods are pulled out. Since it is regulated to be less than the amount of rod withdrawal, even if there are many neutron detectors in the group of neutron detectors surrounding the control rod that is withdrawn from the second time onwards, the output will rise to excessive K. The control rod withdrawal is monitored reliably and positively. Note that the ftjt control collar and fuel assembly are symmetrical with respect to the reactor core (generally, the two center lines ζ of the reactor core are perpendicular to each other). The arrangement of the control rods (i.e., the control rod pattern) inserted into the core during operation is also symmetrical with respect to these center wire numbers, and changes in the control rod pattern, etc. In order to operate the control rods, the control rods are operated in a continuous curve one by one in mutually symmetrical positions. Even if you change from the specified order, these controls gll, j'
Since Mt has an equivalent effect on the reactor core, it has no effect on the operation of the reactor.

An embodiment of the present invention will be described below with reference to FIGS. 6 to 10. That is, 101 in the figure represents a control rod, which has a cross-shaped cross section.

Four fuel assemblies 102 are loaded around the control rods 101, forming a unit grid 103 as shown in FIG. Furthermore, these unit lattices 103 are arranged in a lattice shape as shown in FIG. 7 to form a core structure as shown in FIG. 8. In addition, one square surrounded by a broken line in Fig. 8 corresponds to one unit cell tO.
a... is shown. In addition, a unit lattice 103 is provided in this core.
Output system (LPRM,) at a ratio of one for every four...
A neutron detector assembly 10Δ... is inserted.

Inside these neutron detector aggregates 104, there are four neutron detectors 10 arranged in four stages in the vertical direction of the reactor core shown in FIG.
5... is provided. And this 11. The neutron flux within the reactor core is detected by the neutron detectors i o s .

A control rod withdrawal 1 monitoring device is provided to monitor the amount of withdrawal of the control rods 101 when the control rods 101 are operated. Explain. That is, 705 in the figure is the neutron detector described above, and these neutron detection 5105
... are sent to the faulty neutron detector determination circuit 106, respectively. Reference numeral 107 is a control rod selection circuit for selecting a control rod to be operated by an operator. This extraction control selection circuit 107
The control rod selection signal from the symmetric control rod selection circuit 1098 is sent via the withdrawal order monitoring circuit 108 to the symmetrical control rod selection circuit 1098. The symmetrical control rod selection circuit 109 selects a control rod located at a symmetrical position to the selected control rod. Note that FIG. 8 shows the specific relationship between these control rods. That is, this core has four control rods 101... and fuel assemblies roz... which are symmetrical about the X-X center line and the Y-Y center line, which are perpendicular to each other.
・is placed. Therefore, if 101a in the figure is the selected control rod, then the symmetrical control rod is 10.
1b, l0IC.

101d. Note that this core is located along the X-X center line *Y-
Since the control rods 101a are symmetrical about the y center line, they are located at symmetrical positions.

The effects of power changes and the like on the reactor core due to the operations of 101b, 10IC, and 101d are equivalent to each other. and,
Control rods 10 selected by the symmetrical control rod selection circuit 109
1 a, 10 lb, 10 IC.

A signal specifying 10Zd is sent to the faulty neutron detector determination circuit 106. Then, this faulty neutron detector discrimination circuit 106 operates on these control rods 101a, 101b, 10
Select 16 groups of neutron detectors each surrounding Zc and 101d, and calculate the shape of the i word p! from the neutron detector 105 of these neutron detector groups. Determine the number of malfunctioning neutron detectors from i. The failed neutron detector determination circuit 106 sends a signal indicating the number of failed neutron detectors in each neutron detector group to the extraction order setting display circuit 110. This extraction order setting display circuit 110 is connected to each of the control rods 101a, 101b, 101.
c.

Comparing the number of failures in the neutron detector group surrounding 101d, the number of failures is smaller; 1d# above 1b1'' rod 701a.

The extraction order of 101b, 10IC, and 101d is set.

This drawing order is displayed on a display (not shown), and a signal indicating the drawing order is sent to the drawing order monitoring circuit 10.
8ζ will be sent. -This extraction order monitoring circuit lθ8 is the control rod mentioned above! 01B.

It monitors whether the extraction operation order of ZOIb, 10IC, and 101d is in accordance with the above-mentioned extraction order, and if it is in accordance with the extraction order, sends a signal to the control rod drive mechanism 111 to execute the control rod extraction operation, and If the withdrawal is not in the 110th order, a signal is sent to the control withdrawal prevention mechanism 112 to prevent the control rod from being withdrawn. In addition, when a control rod withdrawal operation is executed, as in the conventional case (in this case, the output increase is monitored based on the signal from the neutron detector 105 surrounding the operated control rod, and the output is not increased excessively). This will prevent the withdrawal of the control rod 8. Also, the amount of withdrawal of the control rod that was pulled out first is sent to the withdrawal monitoring circuit 113 and stored. If the amount exceeds the withdrawal amount of the first operated control rod, a control rod withdrawal prevention signal is sent from this withdrawal check circuit lZ3 to the control rod withdrawal prevention mechanism 112, and withdrawal of the control rod is prevented. , the amount of control rods that are pulled out from the second one onward is regulated.

〔Effect of the invention〕

The present invention includes a plurality of neutron detectors provided in a reactor core, a withdrawal control rod selection circuit for selecting a control rod to be withdrawn,
A symmetrical control rod selection circuit selects a control rod located symmetrically to the control rod selected by the extracted control rod selection circuit, and a symmetrical control rod selection circuit receives signals from the neutron detector. a faulty neutron detector discrimination circuit for discriminating a faulty neutron detector among a plurality of neutron detector groups surrounding each of the selected control rods; The 16th position display circuit for specifying the 11th position of the neutron detector in each group of neutron detectors surrounding the bar and displaying the 11111th position of the neutron detector that has failed, and the operation Monitor whether the control rod withdrawal order is as per the above-mentioned 11th order of control rod withdrawal.
a withdrawal order monitoring circuit that issues a notification and prevents withdrawal of the control rods if the order is not in accordance with the above-mentioned withdrawal order;
When the control rod withdrawal order is the above-mentioned withdrawal + 111' first order, monitor whether the withdrawal amount of the control rod that is pulled out second or later is less than or equal to the withdrawal amount of the control rod that is operated first. Control j that will be pulled out after the 24th! 1. This is to commemorate the withdrawal amount monitoring circuit which prevents the control rod from being withdrawn if the withdrawal amount of the control rod exceeds the withdrawal end of the control rod that was first operated. Therefore, when the control rod to be operated is selected 744, the fit! ! The control rods are selected, and each control rod in a symmetrical position to each other (f, which is the small number of defective neutron detectors in the group of neutron detectors surrounding them) + further control rods. The withdrawal order is set, and the second is 14 (the withdrawal amount of the control rod to be withdrawn is the first operated ii;
The withdrawal amount is regulated to be less than 14 rods.

Therefore, among the control rods located in symmetrical positions that have the same influence on the reactor core, the control rod with the least number of malfunctioning neutron detectors in the group of surrounding neutron detectors is selected. Since this control rod is pulled out at the first time, this control rod is pulled out under accurate withdrawal monitoring, and the amount of control rods that are pulled out is the same as the amount of control rods that are pulled out from the second time onwards. Since the amount of withdrawal is limited to the following, even if there are many malfunctioning neutral pre-detection detectors in the group of neutron detectors surrounding the control rod to be withdrawn, the output will be excessive ( The control rods will not rise, and the control rods will be reliably and accurately monitored with γS.The control rods,
The control rods are arranged symmetrically (generally, the core is arranged symmetrically with respect to the two orthogonal center lines), and the control rods inserted into the core during operation (i.e., the control rods are The control rods are also symmetrical about the center line, and when changing the control rod pattern, the control rods at symmetrical positions are successively operated one by one. Therefore,
In this way, there are ff1l symmetrical f! fil @
Even if the 1P sequence of operations in the IF frame is changed from the operator's specified 11 sequence, the effects of these control rods on the reactor core are the same, so there will be no effect on reactor operation. be.

[Brief explanation of drawings]

1 to 5 show conventional examples, φ, 1 is a plan view of a unit cell, FIG. 2 is a plan view of a part of the core, FIG. 3 is a schematic plan view of the core, Figure 5 is a schematic perspective view showing the arrangement of neutron detectors, and Fig. 5 is a diagram illustrating the error in the control rod withdrawal prevention operation depending on the number of failures of the neutron detector. 6 to 10 show an embodiment of the present invention, and FIG.
The figure is a plan view of the unit cell, Figure 7 is a plan view of a part of the core,
FIG. 8 is a plan view of the core, FIG. 9 is a schematic perspective view showing the arrangement of neutron detectors, and FIG. 10 is a schematic configuration diagram of a control rod withdrawal prevention device. 101... Control rod, 102... Fuel assembly, 105
... Neutron detector, 107... Extraction control rod selection circuit, 10B... Extraction order monitoring circuit, 109... Symmetrical control rod selection circuit, 110... Extraction order setting display circuit, 1
13... Pull-out amount monitoring circuit. Applicant's representative Patent attorney Suzue Takehiko Figure 3, Figure 4 Fi>,;3 , . 3 Figure 5 stock 9 cans l714-pu 4th 11 (notsu-) Figure 6 0 Figure 8 95 procedural amendments 1982 1] Dai-dono 1, Indicator of the incident! Susho 58-55945 No. 2 Name of the invention Control rod withdrawal monitoring device: (, Relationship with the case of the person who makes the compensation) Patent applicant (307) Tokyo Shibaura Electric Co., Ltd. agent

Claims (1)

[Claims] A plurality of neutron detectors installed in the reactor core, an extraction control rod selection circuit that selects a control rod to be extracted, and a control rod located at a symmetrical position to the control rod selected by this extraction control rod selection circuit. A symmetrical control rod selection circuit that receives signals from the neutron detector is connected to a plurality of neutron detector groups surrounding each of the control rods selected by the extraction control rod selection circuit and the symmetrical control and salary selection circuit. A faulty neutron detector discrimination circuit that identifies a faulty neutron detector, and a small number of faulty neutron detectors in each neutron detector group surrounding each of the above control rods. When specifying the withdrawal order in order ζ (the withdrawal order redundancy display circuit that displays the withdrawal order 11 here, and the order in which the control rods are withdrawn 11Ei based on the operator's operation 0), it is checked whether the withdrawal order is as described above A withdrawal order monitoring circuit that monitors the withdrawal order of control rods and outputs a suspicious alarm when the order of withdrawal of control rods is not according to the above-mentioned withdrawal tlt 4 and also prevents withdrawal of control rods, and when the order of withdrawal of control rods is according to the above-mentioned withdrawal order. monitors whether or not the amount of control rods that are pulled out from the second one onward is less than the amount of the first control rod that is pulled out. A control rod withdrawal monitoring device comprising: a withdrawal amount monitoring circuit that prevents the withdrawal operation of the control rod when the withdrawal amount of the operated control rod is exceeded;