JPS6275295A - Monitor device for local oscillation of 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 3. Ftm Description of the Invention [Technical Field of the Invention] The present invention provides a system for detecting local vibrations in a nuclear reactor in which signals from a local power detection device of a nuclear reactor are automatically processed. Related to monitoring equipment.

[Technical Background of the Invention 1] 1 and its Problems] In general, when designing a nuclear reactor or nuclear power plant, it is important to understand whether a disturbance occurs when the reactor is in steady operation or during output h57 according to the design specifications. If the output flow rate, etc. fluctuates due to additional or internal causes, but it gradually approaches a stable value, the reactor is judged to be in a stable state.

However, in the operating range of a nuclear reactor with high output and low flow rate, stability deteriorates, and the output flow rate of the reactor may oscillate. The iron is not operated in such an operating range to avoid the oscillation phenomenon of the nuclear reactor.

However, in recent years, there have been demands from the viewpoint of the stability of nuclear power plants to expand the operating range and to review the maintainability of uC, which is more than sufficient for conventional construction, and stability is critical to A3 in the design standards. It has become an important presence.

On the other hand, the stability of a nuclear reactor is tied to the health of the fuel in the event of oscillation, and in this sense, monitoring the thermal output of the reactor core is necessary to confirm the stability of the reactor. Although it is effective, the thermal output of the reactor is monitored by multiple local power detection devices placed at equal intervals between the channel boxes of the fuel assemblies that make up the reactor core. The average output signal (hereinafter referred to as LPRM signal) is averaged over the entire core.
Hereinafter, this will be referred to as the APIIM signal. ).

However, in the APRM signal of the local horn detection device,
Monitoring of core instability caused by oscillations in the entire reactor core Although it is possible to monitor core stability, it is not possible to monitor local oscillations that occur in specific fuel assemblies within the reactor core, so-called Di1-Synnel stability. .

In addition to channel oscillation, there is also regional oscillation, in which the core does not vibrate as a unit and the phase difference of vibration is positive or negative depending on the region.
It is difficult to monitor so-called higher-order mode oscillations using only the averaging signal that averages the core output signal. In other words, it is necessary to constantly monitor local output signals, but because the number of signals is enormous, this cannot be done by the operator himself.

[Purpose of the invention]

The present invention has been made in view of the above points, and automatically processes local J signals. The object of the present invention is to provide a vibration monitoring device 61 for the 1a location of a nuclear reactor, which is capable of quickly informing operators of local vibrations of the nuclear reactor.

[Summary of the invention]

The present invention automatically processes signals from local power detection devices placed at equal intervals in the core of a nuclear reactor, constantly monitors the stability of the local core from the periodicity and oscillation of the signal,
This is a local imaging monitoring device for a nuclear reactor that predicts the location of oscillation when it occurs and notifies the operator of the location.

[Embodiments of the invention]

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

In the drawings, reference numeral 1 indicates a nuclear reactor, and inside this nuclear reactor 1, a reactor core 2 composed of a large number of fuel assemblies is formed. A plurality of local power detection devices 3.3', 3'', etc. are provided at equal intervals between the fuel assemblies of the reactor core 2 to detect the local thermal output of the reactor. The output detection device 3゜3', 3''... consists of four neutron detectors (hereinafter referred to as T''
It's called LPRM. )4.4', 4''... The local output signal F!i(
The LPPM signal 5''3) is sent to the low-pass filter 5,
High frequency irregular noise components included in the LPPM signal are removed. Considering that the frequency of the vibration between the target and J is 111Z or less, the frequencies of 1 to A in the low-pass filter 5 are 5 t-1z Pi! It is set to 132. The signal from which high frequency components have been cut by the low-pass filter 5 is digitally converted from the analog LPRM signal by the A/D converter 6, and then
It is sent to an averaging device 7.

The averaging device 7 is composed of a memory, an adder, and a divider, and calculates the average value of the digital LPRM Buddhist symbols. The digital LPRM signal and the average value signal are sent to a differentiator 8, where a (g difference value) between the digital LPPM signal and the average value signal is calculated.The deviation value signal from the differentiator 8 is sent to a comparator 9. , the maximum value and the minimum value are obtained by comparing the deviation value with the time series value.The signal from the comparison device 9 is sent to an operation q consisting of a memory, an adder and a divider.
is sent to the device 10, where pe is calculated from the difference between the maximum value and the minimum value.
The ak to Peak value Pi is determined.

In the arithmetic device 10, the amplitude Pea in a certain period
k to Peak Ia P i is multiplied by the number of trees in the LPRM, and these 1 cycles are stored in the memory 11. The signal of the arithmetic bag v110 is sent to the comparator 12, where the Peak to Peak value P1 is compared against a preset alarm level PAI, and P1
If the value exceeds the set alarm level value, the L
P P P The other four trees located on the four sides of M P R
The Peak to Peak l1rl of M is pulled out from the memory 11J: and its fraction is compared and calculated by the comparator 13, and the signal is sent to a cathode ray tube (CRT) 1-1 as a display device for display.

Next, I will explain the action.

The cause of the local vibration is a thermo-hydraulic flow called density wave vibration caused by a feedback phenomenon that occurs between the cold moon flow inside the fuel assembly and the pressure loss between the fuel assembly entrance and exit. It is known that local oscillations occur when the power distribution has a large downward peak because of the oscillations in the thermal output produced by J and nuclear fission.

Therefore, numbers are assigned to the local power monitoring devices that exist in the reactor core (usually 20 to 50), and the LPRM signal q from the lowest position detector (LPRM) of the first local power monitoring device is
(t). Since the LPRM signal from the lowest position detector is an analog display signal and has a vibration period of IHz or less, it is sampled at an interval of about 10 times per second.

LPRM from local output monitoring device 3.3', 3''...
After high frequency components are removed from the signal by a low-pass filter 5, the signal is sent to a Δ/D converter 6, where it is sampled as a digital LPRM signal that is easy to process. The sampling interval is set to approximately Δt=0.1 seconds. In this way, the L I) RM signal Yi(
h) are sequentially sent to the averaging device 7, and a3 is added to the time series.
The average value Y1 is calculated.

On the other hand, the digital L P P M signal Yi (h) and the average value signal Yi are sent to the differentiator 8, and the deviation (Yi (
h)-Yi) is determined. This deviation is compared with the previous time series deviation value in a comparator 9, and the maximum &+ J3 and minimum values are calculated. The maximum and minimum values are sent to an arithmetic unit, where the difference between the maximum and minimum values yields 1) eak
to Peak 1ifj P i is calculated.

The above-mentioned P eak to P cak value PiG is stored in the memory 11 and compared with a preset alarm level PAI- by the comparator 12, and the P cak
t.

When an LPRM whose PeakIItiPi exceeds the alarm level PAL is found, the peak t of the other four LPRMs located around that LPRM is detected.

The peak value is extracted from the memory 11, the value is compared by the comparator 13, and the fuel bundle between the LPRM with the largest vibration In and the alarm level P^[ is estimated to be the oscillation bundle, and its signal is CRT14
The information will be sent and displayed to inform the operator.

In addition, if there is a neutron detector whose signal cannot be detected due to a malfunction, etc., the LPPM signals from the 4 channels of neutron detectors surrounding that detector are monitored, and the average value of the amplitude of those LPRM signals is determined by the other detectors. If it is confirmed that the signal is higher than the actual signal, the position of that 72-tar is displayed.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to quickly and automatically detect a localized oscillation state, which was difficult to detect using only the conventional PPM signal.

[Brief explanation of drawings]

The drawing is a schematic diagram of a local vibration monitoring device for a nuclear reactor according to the present invention. DESCRIPTION OF SYMBOLS 1... Nuclear reactor, 2... Core, 3... Local power detection device, 5... Low pass filter, 7... Averaging device, 8... Differentiator, 9... Comparison device , 10... Arithmetic device, 12... Comparator.

Claims (1)

[Claims] A plurality of local power detection devices arranged at equal intervals in the core of a nuclear reactor, and a differentiator that samples signals from a position below the local power detection device in the axial direction of the reactor core and calculates the deviation from the average value of the signal. , a memory device for determining and storing the amplitude and time from the peak value of the deviation of the differentiator, a device for monitoring periodicity and oscillation from the stored values, and a display device for determining and displaying the position of the oscillation channel. Local vibration monitoring device for nuclear reactors.