JPS63200099A - Method of detecting state of abnormality of control rod - 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] (Industrial Application Field) The present invention generally relates to nuclear reactors, and particularly relates to a method for detecting abnormal conditions in control rods by measuring the reactivity of a nuclear reactor. be.

``Technology from 16'C'' Core shape during reactor operation! Various methods are known for understanding the power deviation of the M reactor using an external neutron east detector, including the following, which target light water-moderated and pressurized wooden reactors. (constant) monitoring, ■ (regular) power distribution measurement using reactor ν1 neutron east detection 2; ■ core outlet temperature monitoring using in-reactor thermocouple, ■ measurement of boron concentration in secondary coolant, ■ outside-core neutron east Axial offset monitoring using a detector; ■Monitoring of the control rod position using control rod position indicating instrumentation; These methods can be used to perform daily core management and detect abnormal conditions.
An investigation is underway to determine the cause.

[Problem to be Solved by the Invention 1] However, the above method does not allow control rod clusters to fall or be pulled out, which has a large effect of adding reactivity to the reactor core! Although the probability of detecting a control rod is high, it is possible to detect a control rod abnormality in the event of a relatively small reaction to the reactor core, such as the fall of several control rod elements, or within the accuracy of the control rod position indicating device. system 0
It is said that the detectability is extremely low in cases such as when 1 is not 13 times.
The C1 question was iF>.

Therefore, the present invention aims to provide control that can be detected with high reliability even in the event of a control abnormality with a low reactivity effect on the reactor core, and a detection method for normal conditions (3). It is something to do.

[Problems and Means and Effects for Solving the Problems] For the purpose stated above, the control rod abnormal state detection method according to the present invention uses a reactivity meter to detect a current signal from a neutron flux detector representing the neutron density in the reactor core. By inputting it into the reactivity meter and solving the nuclear dynamic characteristic equation, +ii directly detects the reaction bottom of the reactor core based on the current signal and inputs it to the judgment circuit. The judgment circuit section compares the change in reactivity with a set change in reactivity to constantly monitor rapid changes in reactivity in the event of a control rod abnormality.

A signal from the control rod control system may be input to the 1υ1 circuit, and if it is input, it is possible to check whether the change in reactivity calculated by the reactivity meter is due to control system operation such as control rod operation. judgment can also be made.

[Example] Next, control rod abnormality according to the present invention! The method for detecting pu is described in detail in connection with the accompanying drawings, which illustrate an yA location in which the method is carried out.

FIG. 1 shows a schematic block 1A of an apparatus implementing the present invention, in which a neutron east detector 2 placed outside the reactor core 1 (of course, it may be placed inside the reactor), an amplifier, a filter The reactivity signal output from the reactivity meter 3 is input to a judgment circuit section 4 and a recording section 5.

Further, the judgment circuit unit 4 calculates whether the reactivity signal from the reactivity meter 3 is equal to or higher than the set reactivity, and whether, for example, the rate of change of reactivity addition over 17 days is greater than the setting 1+I'I or fi. It includes an arithmetic unit 4a such as a computer or an arithmetic circuit, and a logic circuit 4b connected to the operation unit 4a,
The signal 6 of the control rod drive system, which is issued to instruct the insertion or withdrawal of the control rod 8 from the reactor core 1, is sent not only to the drive system of the control rod 8 (not shown) but also to the logic circuit 4b described above. There is. Reference numeral 7 indicates an alarm signal generated when the logic circuit 4b of the determination circuit section 4 determines that there is an abnormal state.

In the above configuration, the detector current indicating the neutron density obtained by the neutron east detector 2 is converted into a reactivity change by solving the nuclear dynamic characteristic equation in the reactivity meter 3, and this reactivity change is The signal is input to the 7A n section 4a of the first cut circuit section 4 and the recording section 5. Figure 3 shows an example of a specific reactivity change, where region A shows the change including noise 7 during normal operation, and region B shows the reaction bottom during a short period of time T due to normal operation of the control rods 5 and 4. 1. Region C represents the change in reactivity due to subsequent changes in the average temperature of the primary coolant, etc.
E is the set reactivity change. For this reaction bottom 1, when the reactivity is higher than the set reactivity and the time rate of change of reactivity addition is higher than the set value, the No. 13 is output from the base portion 4a to the logic circuit 4b. logic fence 4
Since the control rod control system signal 6 is also input to the IJ as described above, the judgment circuit section 4 determines, based on this signal 6,
It is determined whether the reactivity change signal from the reactivity meter 3 is due to the operation of the control rod control system or to an abnormal condition such as abnormal operation of the control rod, falling of the control rod, or malfunction. That is, the logic circuit 4b of the judgment circuit section 4 determines that when there is a signal from the calculation section 4a and there is no control rod control system signal 6, the reactivity change is equal to or higher than the no(z level) and equal to or higher than the set reactivity change E.
Moreover, the reactivity addition is fast control in yj1 hour'I゛3114 5°+, normal! I suddenly decided that alarm 1.3
No. 7 is emitted. Thus, the control txa
A rapid change in reactivity was observed at all times, indicating a control rod abnormality! be detected reliably.

The above description has been about the case where the present invention is implemented in a relatively small core using a single detector and a single reactivity meter, but in a large core, the number of control rods is large. , neutral j−
A bundle detector 1j is also installed at several g-points): In L O, as shown in Fig. 2, for example! 4 Upper and lower 2 minutes arranged in a symmetrical position; It'+I: l1 of s'r
The summation box of the No. 15 current 3 outside the furnace from the detectors 2a to 2d of t4 (the summing box of t4t 1i)
It is possible to send it to the reactivity meter 3 of i-, and make a double publication in the judgment section h'δ section 11. In addition, there is also information that is useful for determining the constant position of the control rod in the reactor -° at 4 (F).
In the J Taiba α, the second garden is connected to the reac- tivity meters 3a to 3d and the recording units 5a to 5d are connected to each of the detectors 2n to 2d, as shown by the Tadashi line, and 1'J1 is disconnected. In circuit section 4, ↑11 'I' indicates not only the abnormal state of the control rod but also the abnormal position.
You can also learn about IJ. In the embodiment shown in FIG. 2 as well, the 'I'lJ section 1'il &'3 section 4 can be constructed in the same manner as in the embodiment shown in FIG.

1-Effects of the Invention 1 As described in 2 above, according to the present invention, since the reactivity meter is connected to the neutron flux detection device and the change in reactivity is directly monitored at all times along with its magnitude, ill f It becomes possible to quickly and accurately detect normal conditions, and to respond quickly to abnormal conditions.

[Brief explanation of the drawing]

No. 117] is a control rod abnormality according to the present invention! Schematic block IA showing an example of a device implementing the melon detection method, second
FIG. 31A is a schematic block diagram showing another example of an apparatus for implementing the method for detecting a full control rod abnormal state according to the present invention.
1 is a diagram showing a graph of changes in reactivity detected by the reactivity meter of the apparatus shown in FIGS. 1 and 2. FIG. ■...Reactor core 2...Neutron east detection word 2a,
2b, 2c, 2 d-, neutron east detector 3...reactivity 31 4...judgment circuit section 3m, 3b, 3c,:
Jd-Reactivity 3F Figure 1 Figure 2

Claims (1)

[Claims] inputting a current signal from a neutron east detector representing the neutron density of the reactor core to a reactivity meter, detecting a change in the reactivity of the core based on the current signal in the reactivity meter, and inputting the detected change in the reactivity of the core to a judgment circuit; A method for detecting an abnormal state of a control rod, comprising comparing the reactivity change with a set reactivity change in the judgment circuit.