JPS6252496A - Method and device for measuring neutron in nuclear reactor - 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 [Field of Application of the Invention] The present invention relates to a method and apparatus for measuring nuclear reactor neutrons.

[Background of the invention]

In boiling water reactors and heavy water moderation reactors, multiple neutron detectors are placed in the reactor core to improve the measurement level, and the reactor output is determined by averaging the detection signals of each neutron detector. is being measured. In order to improve reliability, the reactor neutron measuring device used to measure the reactor output divides the detection signal of the neutron detector into two systems (for example, A system and B system), and performs detection for each system. Average the signals independently,
We are trying to understand the operating status of the nuclear reactor. Figure 5 is a block diagram of an example of such a nuclear reactor neutron measuring device, with two systems, A system and B system, yxh, IAI to IA n
is an A-system neutron detector, IBI~IBn is a B-system neutron detector, and 2 people and 2B are each a neutron detector IAI~
An averaging circuit that averages the signals of lAn and neutron detectors IBI to IBn, 3A and 3B are averaging circuits 2, respectively.
This is a comparator that operates a contact when the output of human and 2B exceeds the standard value and inputs a signal to the reactor protection device JF4 indicating that the reactor output has become abnormally high. The device 4 is configured to perform a scram (reactor output suppression operation) when the comparators 3A and 3B of the A system and B system operate simultaneously.

In Figures 6 and 7, the number of neutron detectors installed is 10.
FIG. 6 is an explanatory diagram of a conventional neutron detection method used in a relatively small number of nuclear reactors, such as 0 or less. FIG. 6 shows the arrangement of a neutron detector, and FIG. In Fig. 6, those labeled with numerals 1 to 8 are neutron detectors, and in Fig. 7, 5A1, 5A2, 5A
3 and 5A4 are A-system neutron detectors each consisting of 8 neutron detectors, 5B1.5B2, 5f33, 5B4
6 respectively indicate B-type neutron detectors, which are eight neutron detectors, and the numbers 1 to 8 written on these neutron detectors correspond to the numbers 1 to 8 in FIG. There is. 61.62...67.68 are averaging circuits, for example, the averaging circuits 61 and 65 include the A-system neutron detector 5A.
The configuration results of the neutron detector 5B1 of the 1 and B systems are input. 71, 72...77.7B are comparators that compare the outputs of the averaging circuits 61, 62...67.68 with a reference value, and 8 is a comparator 61, 62...67.68.
9 is a neutron detector 5A1゜5A2, 5A3, 5A4, 5B1, 582, 583゜5
This is a limiter that suppresses the output signal of B4, and is provided to prevent the reactor from erroneously scramming even if the neutron detector exhibits an abnormality indicating a high output.

In other words, the number of neutron detectors installed is 100 in this way.
In reactors with a relatively small number of neutrons or less, it is not possible to divide neutron detectors into two groups in terms of neutron detection accuracy, so neutron detectors are shared between system A and system B to improve detection accuracy. However, as a result, abnormalities could not be detected quickly and accurately, and there were problems such as a failure of a single neutron detector resulting in a false scram.

In addition, Practical Text Series & 1, Overview of Light Water Reactor Power Plants, edited and published by Nuclear Safety Research Association, October 31, 1982, pages 55-56.

Related technology is disclosed.

[Purpose of the invention]

It is an object of the present invention to eliminate the above-mentioned problems and provide a method and apparatus for measuring nuclear reactor neutrons with high reliability without sharing a neutron detector.

[Summary of the invention]

The present invention collects neutron measurement values from a plurality of neutron detectors uniformly installed around the radial center of a nuclear reactor core for each group in which the plurality of neutron detectors are divided into groups. In a neutron measurement method that transmits an output control signal based on the result of comparing the averaged output with a predetermined setting value, the group is divided into two through the radial center of the reactor core. The first feature is that the neutron detectors of each of the two reactor cores are divided into four groups in the radial direction around the radial center, and are uniformly installed around the radial center of the reactor core. a plurality of neutron detectors, an averaging circuit that averages the measured neutron values for each group of the plurality of neutron detectors, and an output of the averaging circuit that is determined in advance. In the nuclear reactor neutron measuring device, the averaging circuit includes a comparator for comparing with a set value set in the nuclear reactor, and the averaging circuit detects the neutron detectors of each of the 1/2 core divided into two through the radial center of the reactor core. A second feature is that it is an averaging circuit for neutron detectors in groups divided into four in the radial direction around the radial center.

That is, the present invention divides a nuclear reactor into eight regions, connects the neutron detectors placed in each region to one averaging circuit, and forms an output signal for each region. It is designed to perform output suppression by combining out-of-two logic circuits, and is used in nuclear reactors where the number of neutron detectors is 100 or less and where local output fluctuations may occur due to malfunction of control rods. This makes it possible to accurately and quickly detect anomalies with a limited number of neutron detectors, and also enables output control that does not cause false scrams in the event of a single neutron detector failure. .

[Embodiments of the invention]

Examples will be described below.

Figures 1, 2, and 3 are explanatory diagrams of one embodiment. 64 neutron detectors are installed in the core of this nuclear reactor, and these 64 neutron detectors are The entire core is divided into eight regions, passing through the radial center of the core and divided into approximately 45-degree intervals. Figure 2 shows the region division of the neutron detector, and shows the region to which each neutron detector belongs.There are 64 neutron detectors installed in the entire reactor core, so a single region consists of 8 neutron detectors. Consists of a neutron detector. In FIG. 1, numerals 1 to 8 indicate neutron detectors, and neutron detectors belonging to the same group are given the same numerals.

Figure 3 is an explanatory diagram of the configuration of a neutron measuring device having neutron detectors grouped as shown in Figure 1.
2...107, 108 are one group of neutron detectors each containing eight neutron detectors, 111, 112
...117 and 118 are the neutron detectors 101 and 118, respectively.
102...107, 108 detection value averaging circuit, 1
21, 122...127°128 is the averaging circuit 111
, 112...117° A comparator to which the outputs of 118 are input, 13 is an averaging circuit 111, 112...117, 11
8 outputs are comparators 121, 122...127, 128
The figure shows a nuclear reactor protection system in which input is made through a 1-out-of-2 logic. Note that the averaging circuits 111 and 112
. . 117, 118 have independent neutron detectors 101, 102, .

FIG. 4 shows the effect of this embodiment, and shows the signal of the neutron measuring device and the output increase curve around the control rod when a control rod pull-out accident occurs.

The horizontal axis of this figure shows the control rod retraction tip position starting from the initial position, and the vertical axis shows the output of 1.0 at the initial position.
It is shown as follows. The detection area of the present invention (1/8 area) and the conventional detection area (1/4 area) for X and Yrt, respectively.
, Z (black circle) indicates the position of the control rod to be pulled out, control rod peripheral output, neutron monitor signal in the case of the present invention, monitor signal in the case of the present invention (when one monitor is bypassed), neutron monitor in the conventional case The conventional monitor signal (when one monitor is bypassed) is shown.

In the case of the control rod withdrawal event shown in Figure 4, the average of eight 1/8 area neutron detectors of the present invention is compared to the case of averaging eight 1/4 area neutron detectors of the conventional method. It can be seen that the output value increases closer to the peripheral output of the control rods when the control rod is activated, and the event can be detected more effectively and quickly. Furthermore, even if multiple neutron detectors (the number determined based on the core design) fail and are bypassed, the reactor's output suppression operation is normally activated, so even when multiple neutron detectors are bypassed, the neutron detector It is desirable that the accuracy of
As is clear from the comparison between the embodiment of the present invention and the conventional case, even if one neutron detector is in a bypass state, the error is small and it is found that the device is excellent as an output suppression device.

According to this embodiment, the core is virtually divided into eight parts, and 1/8
An independent averaging circuit is provided for each region, and the output of this averaging circuit is used to create 1) 17 out-of-2 logic within the X reactor protection device, so it is possible to use the same number of neutron detectors as before. In addition to being able to perform output suppression operations with higher precision than conventional methods, the neutron detectors are not shared, so even if one neutron detector fails and emits an abnormally high signal, unnecessary equipment can be removed. There is an effect that unnecessary output suppression operation does not occur without providing it.

In the above-mentioned embodiment, a case has been described in which an output suppression operation such as a scram is performed based on the neutron measurement results, but the neutron measurement results can be used for output control in general.

〔Effect of the invention〕

The present invention makes it possible to provide a highly reliable nuclear reactor neutron measurement method and apparatus without sharing a neutron detector, and has great industrial effects.

[Brief explanation of the drawing]

1 and M2 are explanatory diagrams of one embodiment of the nuclear reactor neutron measuring device of the present invention, FIG. 3 is a block diagram, and FIG. 4 is an explanatory diagram showing the effects in comparison with the conventional case. Fifth
The figure is a block diagram of a conventional nuclear reactor neutron measurement device, FIG. 6 is an explanatory diagram of another example, and FIG. 7 is a block diagram. 101.102...107,108...one group of neutron detectors, 111,112...117°1
18... Averaging circuit (of the detected values of one group of neutron detectors), 121, 122... 127, 1 (one person for f power) 1 Fixed # 2 Eye # 4 Mouth

Claims (1)

[Claims] 1. Measured values of neutrons by a plurality of neutron detectors uniformly installed around the radial center of the reactor core are divided into groups. In a reactor neutron measurement method that transmits an output control signal based on the result of comparing the averaged output for each group with a predetermined set value, the group A method for measuring nuclear reactor neutrons, characterized in that the neutron detectors of each of the 1/2 reactor cores, which are divided into two, are divided into four groups in the radial direction around the radial center. 2. Averaging the measured values of neutrons for each group of multiple neutron detectors uniformly installed around the radial center of the reactor core, and for each group of the multiple neutron detectors. In a nuclear reactor neutron measurement device having an averaging circuit that compares the output of the averaging circuit with a predetermined setting value, the averaging circuit A nuclear reactor neutron characterized in that it is an averaging circuit of neutron detectors in a group in which the neutron detectors of each of the 1/2 core divided into two are divided into four in the radial direction around the radial center. Measuring device.