JPH02102483A - Area monitor for automatic calibration - Google Patents

Abstract

PURPOSE:To calibrate a detector automatically and to improve measurement accuracy by providing an SSD type detector, a light emitting element, and a multiplexer. CONSTITUTION:A pulse signal from the SSD type detector 11 is counted by a counter 16 for actual measurement and the counted valueis converted into a dosage rate by using conversion constants corresponding to channels, so that the dosage rate is displayed in order. In calibration mode, one channel is selected by the multiplexer 14 under the command of a calibration mode execution part 18 and the output of the detector 11 of the channel is inputted to the counter 17 for calibration. At the same time, a pulsating current is sent from the circuit 18 to the light emitting element 12 incorporated in the detector 11 to make the element 12 emits light with constant brightness. The sensor of the detector 11 is excited to send the pulse signal. This signal is counted by the counter 17, whose counted value is inputted to the circuit 20; and the circuit 20 subtracts the measured value in actual measurement mode from the last counted value of the circuit 20 to find the counted value of light emission by the element 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an area monitor that monitors the radiation dose within a building of a nuclear facility.

(Prior Art) A conventional area monitor is shown in FIG. In the figure, (1) is
An SSD type detector, (2) a pulse amplifier, (3) a multiplexer, (4) an actual measurement counter, and (5) a monitor unit.

In this area monitor, the radiation dose rate [a+R/h] being measured and the count rate (c
ps) is set, and the dose rate is displayed in proportion to the number of pulses input from the SSD type detector (1) to the actual measurement counter (4).

Conventionally, in order to determine the value of this conversion constant, it has been calculated by irradiating radiation onto the SSD type detector (1) using a reference calibration radiation source and determining the count rate at that time.

(Problem to be solved by the invention) In the case of the method for determining the conversion constant as described above, the SSD type detector (1) is brought to the calibration room, or the radiation source for calibration is brought to the detector. The calibration work was difficult. There is also the problem that the area monitor loses its function during calibration.

Therefore, it is an object of the present invention to realize an automatically calibrated area monitor that improves measurement accuracy since the detector can be calibrated even during measurement and the conversion constant is constantly updated. be.

[Structure of the invention]

(Means for Solving the Problems) The automatic calibration type area monitor of the present invention uses an SSO type detector with a built-in light emitting element in the detection part, and also uses a counter to count pulse signals from this detector for actual measurement. A counter for calibration and a counter for calibration are provided via a switching circuit, and a channel consisting of multiple channels is selected during calibration mode, which utilizes free time during the processing cycle of actual measurement mode, and the pulse signal from that detector is executed. A calibration mode execution circuit is provided that has the function of switching from the measurement counter to input to the calibration counter and at the same time sending a pulsed current to the light emitting element built in the detector to cause the light emitting element to emit light. , Furthermore, the calibration mode execution circuit performs a calibration process for calculating the conversion constant for each channel using the count value of the measurement counter and the count value of the calibration counter for each channel. It is configured to include an arithmetic circuit that converts the counted value of the actual measurement counter into a dose rate for each channel using the latest updated conversion constant for each channel, and outputs the converted value. be done.

(for production) In the automatic calibration type area monitor of the present invention.

In the actual measurement mode, the pulse signals from the SSD type detector obtained sequentially from each channel at a fixed processing cycle are counted by the actual measurement counter, and converted into a dose rate using the conversion constant corresponding to each channel in the arithmetic circuit. Convert and display sequentially.

In calibration mode at the end of the processing cycle after each channel has been scanned.

One channel of each channel is selected by a command from the calibration mode execution circuit, and the output of the detector of this channel is switched to be input to the calibration counter, and at the same time, the output of the detector of this channel is input to the light emitting element built in the detector. A four-pulse current is sent from the calibration mode execution circuit to cause the light emitting element to emit light at a constant brightness. The sensor of the SSD type detector is excited by the light energy of this emitted light and emits a pulse signal.

This pulse signal is counted by a calibration counter, and the counted value is input to an arithmetic circuit. The arithmetic circuit calls the stored count value of the previous actual measurement mode of the relevant channel, subtracts the count value of the actual measurement mode from the count value of the current calibration counter, and calculates the count value due to the light emission of the light emitting element. Find the count value.

Then, a moving average is obtained using past data of this count value, a conversion constant is calculated based on this, and the conversion constant is updated. Then, in the next actual measurement mode, the counted value is converted into a dose rate using this updated conversion constant.

(Example) The present invention will be described in detail below based on an example shown in one drawing.

Fig. 1 shows an automatic calibration type area monitor according to an embodiment of the present invention. In Fig. 1, (11) is an SSD type detector with a built-in light emitting element (12), and is provided with channels from 1 to 32. There is. For example, an LED is used as the light emitting element (12). (13) is a pulse amplifier that amplifies the pulse signal from the SSD type detector. (
14) is a multiplexer which switches and outputs the pulse signal from the SSD type detector (11) of each channel via the pulse amplifier (13) at predetermined time intervals. (16)
is an actual measurement counter, and (17) is a calibration counter, which is connected to the output terminal of the multiplexer (14) via the switching circuit (15) and counts the pulse signals from the SSD type detector (it). (18) is a calibration mode execution circuit, which selects a channel from a plurality of channels based on a program using a multiplexer (14) in a calibration mode that utilizes the remaining time of the processing cycle after the actual measurement of each channel is completed, and selects the SSD type. A command is given to the switching circuit (15) to switch the pulse signal from the detector (11) from the actual measurement counter (16) and input it to the calibration counter (17), and at the same time, the SSD type detector (11) It has a function of controlling a switching circuit (19) so as to be connected to a lead to a light emitting element (12) built in the light emitting element (12), and sending a pulsed current to the light emitting element (12) to cause it to emit light. This pulsed current then flows through the light emitting element (
12) so that the pulse signal output from the SSD type detector (11) due to the light emission is equivalent to the pulse signal output from the SSD type detector (11) when receiving radiation from the calibration radiation source. It is verified in advance and set to a predetermined value. (20) is an arithmetic circuit that calculates the count value of the measurement counter (16) and the calibration counter (17) for each channel.
) Calibration processing for calculating the conversion constant of the channel using the counted value of Using the latest conversion constant for each channel, the count value of the actual measurement counter (16) is converted into a dose rate for each channel and output. This output is sent to an indicating/recording instrument (not shown) for indicating/recording.
recorded.

The operation of the automatic calibration type area monitor according to one embodiment of the present invention configured as described above will be described below. As shown in Figure 2, this area monitor has a processing cycle of 300m5ec.
Measurements are being made from channels 32 to 32, but the time spent on actual measurement is approximately 280 ssec, and the remaining 20 m5 ec is idle time. The area monitor of this embodiment uses this free time to perform calibration.

In the actual measurement mode, as shown in FIG. 3, measurements are performed sequentially from channel 1 to channel 32.

During that time, the pulse signal from the SSD type detector (11) of each channel via the pulse amplifier (13) is sequentially input to the actual measurement counter (16) one channel at a time using the multiplexer (14). The count value counted in (16) is converted into a dose rate using a conversion constant corresponding to each channel in the arithmetic circuit (20) and output, and the dose rate for each channel is sequentially displayed and recorded.

Each time the actual measurement of each channel is completed, the remaining 20 vas
During ec, select one channel per processing cycle,
In this calibration mode, in which calibration is performed sequentially from one channel, the multiplexer (14) selects the SSD of one channel based on a command from the calibration mode execution circuit (18).
A pulse signal is output from the shape detector (11), and a command is also given to the switching circuit (15) to switch the output of the multiplexer (14) from the actual measurement counter (16) and connect it to the calibration counter (17). . At the same time, the calibration mode execution circuit (18) controls the switching circuit (19) to connect the lead to the light emitting element (12) of the one-channel SSD type detector (11) to the calibration mode execution circuit (18), A pulsed current is sent to the light emitting element (12) and the light emitting element (1
2) to emit light at a constant brightness. As a result, the sensor of the one-channel SSD type detector (11) is excited by the light energy of the emitted photoelectric element (12) and emits a pulse signal. This pulse signal is counted by a calibration counter (17), and the counted value is input to an arithmetic circuit (20). The arithmetic circuit (20) calls the stored count value C1 of the previous actual measurement mode of one channel, subtracts C1 from the current count value of the calibration counter (17), and calculates the value of the light emitting element (12). ) count value n 1= (K
Knee C engineering) is found. Furthermore, in order to reduce measurement errors due to statistical fluctuations, a moving average (10 data) of this count value n is calculated, a conversion constant is determined based on it, and the conversion constant is updated. Then, in the next one-channel actual measurement mode, the updated conversion constant is used to convert the count value into a dose rate and output it. This single channel dose rate is displayed and recorded.

This completes one processing cycle, and as shown in Figure 3, the next processing cycle is to calibrate 2 channels, and the first processing cycle is to calibrate 3 channels, and so on. Once the calibration of all channels is completed, the calibration of all channels will be completed.

In this example, the time required to first calculate the moving average of 10 data is 300 m5 per channel.
EC
c is necessary. In other words, the time required for the first calibration from channel 1 to channel 32 is approximately 100 seconds.
becomes.

However, in the case of repeated calibrations, the past 9 data are stored, so it only takes 300m5ec per channel.
Calibration up to the channel is completed in about 10 seconds.

As described above, according to this embodiment, on-line automatic calibration of the area monitor detector is possible, and thereby the following effects can be obtained.

Calibration can be performed at any time even in the C83a room, and measurement accuracy is improved because the conversion constant is constantly updated.

(b) It is not necessary to carry the detector to the calibration room for calibration or to carry the calibration radiation source to the detector, and the amount of work is reduced.

(c) Calibration can be performed without interrupting the measurement of the area monitor, and the inconvenience of the occurrence of a state in which the monitoring function is lost is eliminated.

In addition, although the example mentioned above illustrated the case where the number of channels was 32, the number of channels is not particularly limited.

〔Effect of the invention〕

As described in detail above, according to the present invention, online automatic calibration of the area monitor detector becomes possible.

This provides the following effects.

(a) Calibration is possible at all times even during '114 calibration, and the conversion constant is constantly updated, improving 811 calibration accuracy.9
(b1 It is not necessary to carry the detector to the calibration room or carry the calibration radiation source to the detector for calibration, and the amount of work is reduced.

[c] Calibration is possible without interrupting the measurement of the area monitor, and the inconvenience of the monitoring function loss state is eliminated.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of an automatic calibration type area monitor according to an embodiment of the present invention, Fig. 2 is an explanatory diagram showing a breakdown of the processing cycle of the area monitor shown in Fig. Processing time chart FIG. 4 is a block diagram showing the configuration of a conventional area monitor. 11... SSOS horizontal device 13... Pulse multiplier 15... Switching circuit 17... Calibration counter 19... Switching circuit 12... Light emitting element 14... Multiplexer 16... Actual Measurement counter 18...Calibration mode execution circuit 20...Arithmetic circuit section 1.2 (20mSeC) 2nd cause Agent Patent attorney Norihiro Ogo Figure 3

Claims (1)

[Claims] A detection unit includes a plurality of channels of SSD type detectors with built-in light emitting elements, a pulse amplifier provided for each of these detectors, and a pulse signal from each of the SSD type detectors via the pulse amplifier at a predetermined time interval. an actual measurement counter and a calibration counter connected to the output terminal of the multiplexer via a switching circuit and counting pulse signals from the SSD type detector;
In the actual measurement mode, the switching circuit is controlled to connect the output end of the multiplexer to the actual measurement counter, and in the calibration mode, the switching circuit is controlled to connect the output end of the multiplexer to the calibration counter, and the program Based on this, the multiplexer is commanded to select a certain channel, and at the same time, the switching circuit is controlled to connect the lead to the light emitting element built in the SSD type detector of the selected channel, and a pulsed current is sent to the light emitting element. A calibration mode execution circuit that sends a signal to cause this light emitting element to emit light, and a calibration process that calculates a conversion constant for each channel using the count value of the actual measurement counter and the count value of the calibration counter for each channel. is executed for the specified channel from the calibration mode execution circuit at each processing cycle, and the count value of the actual measurement counter is converted to the dose rate for each channel using the latest conversion constant for each channel. An automatic calibration type area monitor that is equipped with an arithmetic circuit that converts and outputs.