JPS6126893A - Detector for abnormality of neutron detector - 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 an abnormality detection device for an in-core neutron detector of a nuclear reactor.

[Background of the invention]

In a power reactor, a large number of neutron detectors are installed inside the reactor in order to measure the reactor power and monitor deviations from thermal limit values due to local increases in power. A neutron detector has a neutron detection section and a cable section that transmits signals from the detection section. This difference in specific heat between the detection part and the cable part causes the gas sealed inside the detector to leak, affecting the sensitivity of the detector and often causing abnormal values in the detector value. are doing.

If the abnormal value of this detector is large, compare the value of that detector with the value of the detector when the detector gain is calibrated, and detect an abnormality of the detector based on the large difference. The method is currently in use. However, in this method, gain calibration is normally performed only about once a month for atomic couplants because it corrects for the slow deterioration of detector sensitivity over time due to neutron irradiation. This gain calibration is carried out by two operators and takes about five hours each time, so it is difficult to shorten the interval between calibrations compared to the current interval. Furthermore, since the main purpose is to monitor sensitivity deterioration due to neutron irradiation, it is not sufficient to monitor sensitivity changes of individual detectors. Also, if the change in the detector value is so small that it cannot be detected by this method but occurs suddenly, the detector value is periodically fetched and compared with the previous value and the current value to evaluate the deviation. A method of detecting an abnormality may also be considered. However, with this method,
It is difficult to detect an abnormality when the value of the detector changes slowly.

[Purpose of the invention]

An object of the present invention is to provide a means and apparatus capable of detecting an abnormality in a neutron detector even when the value of the neutron detector changes small and slowly.

[Summary of the invention]

The feature of the present invention is that the value of the neutron detector placed in the reactor when the reactor output becomes constant is set as a reference value, and the deviation between that value and the current value of the detector is evaluated. This is to detect an abnormality in the detector.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

The neutron detector signal 7 and the generator power signal 8 are converted into a neutron detector value and a generator power value by the plant status input section 3, and read into the abnormality detection section 2. The control rod position signal 9 writes information into the storage unit 5 when the control rod position changes according to the plant status input unit 3. When the operator requests initialization of the abnormality detector from the operator operation panel 6, the information is written into the storage device 5. The abnormality detection unit 2 determines whether the neutron detector is abnormal based on the value of the neutron detector, the generator power amount, and the information in the storage unit 5. If an abnormality is detected, an alarm message is printed on the typewriter 4 and the storage unit Write the information in 5.

FIG. 2 is a flow diagram showing the abnormality detection process.

In block 110, it is determined whether there is a request to initialize the abnormality detection device. If there is an initialization request, initialization processing 14Q is executed. The initialization request is requested when the operator determines that the output distribution of the reactor has changed due to a change in Zenon, or when it is necessary to set the reference value of the abnormality detection device to the current value. Initialization processing 140 sets the reference value of the generator power and the detector smoothing value to current values. If there is no initialization request, it is determined in block 120 whether or not the furnace output is constant. The determination of constant furnace output is evaluated based on the deviation of the generator power from the reference value as follows.

I GMWIE GltWBAS I > it
' -- (1) G E: Generator power GMVBAS: Generator power reference value ε1': Furnace output change determination value If equation (1) is satisfied, it is determined that the furnace output is changing. Here, ε1' is defined as the change judgment value ε1 at rated output converted to the current output, and is expressed by equation (2).6 RGMwE: Rated generator power ε1: Furnace output change judgment value ε1 at rated The value may be set in consideration of noise (mainly plant noise).

If it is determined that the furnace output has changed, initialization processing 140 is performed. If so, block 130 is performed. In block 130, it is determined whether the value of the detector that was determined to be input abnormal during the previous execution has returned to normal during the current execution, and in that case, initialization processing 14'O is performed. Otherwise block 150 is performed. Block 150 performs the calculation of a detector smoothing value.

The detector values are smoothed to minimize the influence of noise and improve the accuracy of the input data. Smoothing uses the exponential smoothing method, and is expressed as equation (3).

α ・・・・・・・・・ (3) RPAVG (N, L): Detection m smoothing value RLP
(N, L): Detector value α: Smoothing coefficient [N, L are detector coordinates] Here, the detector value RPL (N.

When L) is abnormal (RLP (N, L)=O), the smoothing value is also set to 0.

Next, in block 160, the elapsed time since the furnace output became constant is determined. This is because even if it is determined that the furnace output is constant, the detector smoothing value does not become effective until a certain amount of time has elapsed. A time for this validity is specified, and block 170 is executed exactly when the specified time is reached. Block 170 sets baselines for generator power and detector values.

RPBAS (N, L) = RPAVG (N, L) ・
... (4) GMWBAS = GMWE
・・・・・・・・・ (5) RPBAS (
N, L): Reference value of the detector value From the next time onward, block 180 is executed. Block 180 determines whether the detector is abnormal. The detector is determined to be abnormal when the following formula (6) holds true.

+ 1 RPAVG(N,L)l -RPRAS(N
, L) l > E 2' (6) ε2': Detector abnormality judgment value Equation (6) indicates that the detector is abnormal if the deviation between the current detector value and the reference value is greater than the judgment value ε2'. It is determined that there is.

Here, 127 is the judgment value ε2 at the rated output converted to the current output level, and is expressed by equation (7).

ε2: The detector abnormality determination value ε2 at the rated time only needs to take into account the fluctuation in the value of the detector at the rated time, and the influence of noise can be ignored.

If formula (6) holds true, block 190 is executed.

In block 190, the smoothing value of the detector determined to be abnormal is set to a negative value to set an abnormal state.

RPAVG (N, L) = -I RPAVG (N, L)
1-...= (8) Next, in block 120, an alarm message is printed for the abnormality detector. Blocks 180-210 are performed for all detectors. In block 180, if the detector long value is abnormal,
T*SRPAVG(N,L)=Onodo@Ha Formula (6) is not judged. The abnormality determination shown in FIG. 2 is always executed at regular intervals to monitor the abnormality of the detector.

〔Effect of the invention〕

As described in detail above, according to the present invention, it is possible to detect an abnormality in the detector even if the abnormality appears as a slight and slow change in value.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the apparatus of the present invention, and FIG. 2 is a flowchart showing the abnormality detection process of the present invention. 1... Neutron detector abnormality detection device, 7... Neutron detector signal, 8... Generator power signal, 9... Control rod position signal.

Claims (1)

[Claims] 1. A nuclear power plant has a plant status input section, an abnormality detection section, a storage device, and an operator's control panel, and is capable of measuring the current value and the value of the neutron detector installed in the reactor when the reactor output becomes constant. A neutron detector abnormality detection device characterized in that a neutron detector with a large deviation from a value is determined to be abnormal.