JPH0447291A - Nuclear reactor output monitor - Google Patents

Abstract

PURPOSE:To monitor events produced in a nuclear reactor to contrive the improvement of safety and an availability factor by estimating production phenomena in the nuclear reactor from a mutual relationship between the difference of signals between neutron detectors and the position of the detectors in the nuclear reactor. CONSTITUTION:Several local output monitor system (LPRM) signals 6 selected so as not to have deviation in respective spatial distribution in channels (CH) 2a-2f of an average output monitor system 2 of a device 1 are input to be averaged so as to monitor 2g on the basis of output signals. In addition, in CH3a-3d of an axial output monitor system 3 the same axial height of respective LPRM signals 6 is input to be averaged. Further, in CH4a-4d of a radial output monitor system 4 the LPRM signals 6 from the positions closest to respective maximum output bundle and three points which are the positions quartly symmet rical with the former positions are input to be averaged respectively. Fast phenomena can be estimated on the basis of sign rows of the signal from a neutron detector and the estimation of long-term and periodical phenomena is made possible according to statistical processing of the signals from the detector.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention (Industrial Application Field) The present invention relates to a reactor power monitoring device used for monitoring the reactor power of a boiling water nuclear reactor.

(Prior Art) Conventionally, in order to operate a nuclear power plant safely, stably, and effectively, a large number of parameters have been detected and measured and used for operation control.

For example, among many instrumentation signals, particularly important output signals include a local output monitor system (hereinafter referred to as LPRM) and an average output monitor system (hereinafter referred to as APRM). In other words, the LPRM has 4 signals in the axial direction for about 16 fuel assemblies (43X in the 1.1 million kilowatt class).
4) APRM is the average of several of these, and is usually measured over several channels (1
It is equipped with 100,000 kilowatt class (6 channels).

In addition, LPRM is used during control rod operation.
Rod block monitor system that selects several rods and averages them (
There is also an APRM (hereinafter referred to as RBM), but conventionally, during normal operation, this APRM has been used to monitor the reactor output.

(Problem to be solved by the invention) However, since APRM averages LPRM, although it represents the output change of the entire reactor core, there are cases where detection of local events is overlooked, or Because it captures only macroscopic changes, it has been difficult to interpret the phenomenon physically and structurally. For this reason, unnecessary scrams and the like were performed to ensure safety, which could lead to a decrease in the operating rate.

The present invention has been made in response to such conventional circumstances, and allows for more accurate monitoring of events occurring within a nuclear reactor than in the past, thereby improving safety and operating efficiency. The aim is to provide a nuclear reactor power monitoring device that can achieve the desired results.

C. Configuration of the Invention (Means for Solving the Problems) That is, the present invention provides a reactor power monitoring device that monitors the reactor power based on signals from a large number of neutron detectors arranged in the reactor. , comprising means for estimating a phenomenon occurring within the nuclear reactor from the relative relationship between the difference in signals between the neutron detectors and the position within the reactor where these neutron detectors are arranged. It is characterized by

(Function) The reactor power monitoring device of the present invention having the above configuration is capable of detecting a It is equipped with a means to estimate the phenomena occurring inside the reactor.

Note that such phenomena can be estimated quickly by, for example, converting the signal from a neutron detector into a code string and matching this code string with a code string stored in a database. Estimates of long-term periodic phenomena can be made by statistically processing the signals from the detectors.

Therefore, events occurring within the nuclear reactor can be monitored more accurately than in the past, and safety and operation rates can be improved.

(Embodiment) Hereinafter, one embodiment of the nuclear reactor power monitoring device of the present invention will be described with reference to the drawings.

FIG. 1 shows the configuration of the reactor power monitoring system of this embodiment.
The average power monitoring system 2, the axial power monitoring system 3, and the radial power monitoring system 4 each include a core 5, an axial power monitoring system 3, and a radial power monitoring system 4.
(for example, 43×4 in the 1.1 million kilowatt class)
) The LPRM signal 6 from the neutron detector located in the neutron detector is input.

The average output monitoring system 2 is provided with, for example, six channels 2a to 2f, and these channels 28
~2f, several LPRM signals 6 selected so that their spatial distributions are not biased are input and averaged. The average output monitoring section 2g is configured to perform monitoring based on these averaged signal outputs.

In addition, the axial output monitoring system 3 includes four channels 3a.
~3d are provided. Normally, four neutron detectors in the reactor core 5 are arranged in one string with different heights in the axial direction, so in these channels 3a to 3d, among the LPRM signals 6, those having the same height in the axial direction Input and average. That is, for example, channel 3a receives only the LPRM signal 6 from the neutron detector located at the top stage, channel 3b receives only the LPRM signal 6 from the neutron detector located at the next stage, and channel 3C receives only the LPRM signal 6 from the neutron detector located at the next stage. Only the LPRM signal 6 from the neutron detector placed at the next stage is averaged, and in channel 3d, only the LPRM signal 6 from the neutron detector placed at the bottom stage is averaged. The axial output monitoring unit 3e is configured to perform monitoring based on these averaged signal outputs. That is, this axial output monitoring section 3
In e, the signals from channels 3a to 3d detect events that have the same response between axial monitors, such as pump trips and core stability, control rod operations or control rod movement events, and events originating from channel stability. Distinguish events that are correlated with causes such as local oscillation phenomena and differences in response between axial directions. In addition, even during an earthquake, differences in the response of the monitor between the axial directions occur due to differences in the axial void fraction distribution.

Furthermore, the radial output monitoring system 4 includes four channels 4.
channels a to 4d are provided, and these channels 4a to 4d are provided.
4d, the LPRM signal 6 from the part closest to the highest output bundle, and the LPRM signal 6 from three points 1/4 symmetrical to this part are input and averaged. The radial output monitoring unit 4e is configured to perform monitoring based on these averaged signal outputs. That is, the radial output monitoring section 4e independently monitors the signals from each channel 4a to 4d, and also monitors the channel stability based on the correlation between these signals and the local oscillation phenomenon based thereon.

Note that the monitoring in each of the above-mentioned monitoring units is performed as follows. That is, for fast events, the change in signal from a reference value is encoded into a relatively small number of patterns in terms of direction and magnitude. In order to remove components that do not affect the overall behavior, such as only directions (+) and (-), high frequency components, or irregular components, we change the sampling interval to, for example, (10+ + -10) → (10+ + + +) and correct it. Regarding the magnitude of change, it is divided into three categories (large, medium, and small) based on the ratio of the magnitude divided by the reference value.

According to such a method, the phase difference in response between each signal can be detected from the direction of change. In other words, it is possible to detect the delay in response based on the signal that changed to the direction of increase earliest, or using the signal of interest as a reference. Furthermore, by simplifying the codes representing the direction and magnitude of change, the phenomenon can be estimated by matching with the reference databases. The reference database is one in which the actual data already observed is encoded using the method described above, and the code strings and phenomena are made to correspond to each other.

Since it is unlikely that the code string of the database and the measured signal will perfectly match, when performing matching, first of all, consider the quick response and keep the interval used for matching as short as possible (the number of samples is about 5). Take a logical product.

For example, if 10 + + + Then judge.

On the other hand, statistical methods are applied to periodic phenomena. As a statistical method, the period is calculated from the delay time at which the absolute value of the coefficient value is maximum using the simplest correlation coefficient method, and it is detected whether the period is approximately constant and periodicity is recognized. If periodicity is found, then the history of amplitude changes is checked to see if the vibration phenomenon has grown.

In other words, the reactor power monitoring device of this embodiment can monitor events occurring inside the reactor more accurately than monitoring using conventional APRM, improving safety and improving operation rate. can be achieved.

[Effects of the Invention] As described above, the reactor power monitoring device of the present invention can monitor events occurring within the reactor more accurately than before, improving safety and improving operating efficiency. It is possible to improve the

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a nuclear reactor power monitoring device according to an embodiment of the present invention. 1... Reactor output monitoring device 2...
...Average output monitoring system 3...Axial output monitoring system 4...
...Radial power monitoring system 5...Core 6...LPRM signal Applicant: Toshiba Corporation

Claims (1)

[Claims] (1) In a reactor power monitoring device that monitors the reactor output based on signals from a large number of neutron detectors placed in the reactor, differences in signals between the neutron detectors and detection of these neutrons 1. A nuclear reactor output monitoring device comprising: means for estimating a phenomenon occurring within the reactor from a relative relationship with a position within the reactor where the reactor is placed.