JP2006177883A - Device and method for inspecting surface contamination - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently and automatically determine existence of radiation contamination of a measuring object while moving it, and to accurately and efficiently measure the contamination of the measuring object with a high reliability as circumstances demand. <P>SOLUTION: The device for inspecting surface contamination measures the discharge radiation dose from the measured object while moving the measuring object on a conveyer. The device 10 comprises a radiation detecting means 23 for measuring discharge radiation dose while changing the measuring part according to the movement of the measuring object 11, a monitoring and determining means 20 for monitoring the increase trend of the measurement value from the radiation detecting means 23, and a motor speed control means 18 for controlling a motor for driving the conveyer to reduce or change the conveyer speed or stop the conveyer when the increase trend of the measurement value is recognized by the monitoring and determining means 20. When the increase trend of the measurement value is recognized by the monitoring and determining means 20, the discharge radiation dose from the measuring object 11 is measured by reducing the conveyer speed or stopping the conveyer, and the existence of the radiation contamination of the measured object is determined. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a radiation inspection technique in which an object to be measured is mounted on a conveyor and continuously inspected for contamination while the object to be measured is subjected to contamination inspection. The present invention relates to a surface contamination inspection apparatus and an inspection method thereof.

  2. Description of the Related Art Conventionally, as this type of surface contamination inspection apparatus, there is an unloading monitor apparatus that performs measurement of contamination while an object to be measured such as an article unloaded from a radiation control area such as a nuclear facility is mounted on a conveyor.

  In this carry-out monitor device, it is required to improve the radiation detection sensitivity in order to strengthen radiation management for an object to be measured such as an article taken out from a recent radiation management area.

In order to improve the radiation detection sensitivity, as described in JP-A-6-148334 (see Patent Document 1) and JP-A-6-64714 (see Patent Document 2), it responds to changes in the background level. There is a radiation monitor that automatically sets the optimum contamination counting time and adjusts the conveyance speed of the object to be measured to improve the workability of contamination inspection.
JP-A-6-148334 JP-A-6-64714

  In conventional surface contamination inspection equipment used for radiation monitors, it is necessary to reduce the speed of the conveyor in order to improve the radiation detection sensitivity of the object to be measured and to obtain high detection sensitivity. If the conveyor speed is reduced, the measurement time becomes longer. Therefore, there is a problem that it takes a long time to measure the contamination of the object to be measured.

  In addition, in order to obtain high radiation detection sensitivity, it may be possible to install a lead shield to reduce the influence of the background radiation level. However, the addition of a lead shield increases the weight of the device and facilitates installation. Not.

  The present invention has been made in consideration of the above-mentioned circumstances, and efficiently and automatically determines the presence or absence of radiation contamination of the object to be measured while moving it, and the contamination measurement of the object to be measured is highly reliable and flexible. It is an object of the present invention to provide a surface contamination inspection apparatus and an inspection method thereof that can accurately and efficiently measure while maintaining the above.

  The present invention determines the presence or absence of contamination from the rising tendency of the radiation count rate during the measurement of radiation contamination of the object to be measured. It is in providing a contamination inspection apparatus and its inspection method.

  In order to solve the above-described problems, a surface contamination inspection apparatus according to the present invention is a surface contamination inspection apparatus that measures the amount of radiation emitted from a measurement object while moving the measurement object on a conveyor. The radiation detection means for measuring the radiation dose while changing the measurement site according to the movement of the monitor, the monitoring judgment means for monitoring the rising tendency of the measurement value from the radiation detection means, and the rising tendency of the measurement value by this monitoring judgment means Motor speed control means for controlling the motor for driving the conveyor so as to decelerate, change over or stop the conveyor speed, and when the monitoring judgment means shows an increase in the measured value, the conveyor speed Is set to decelerate, switch or stop control, and measure the amount of radiation emitted from the object to be measured to determine the presence or absence of contamination of the object to be measured. A.

  Further, the surface contamination inspection method according to the present invention is the surface contamination inspection method for measuring the radiation dose emitted from the object to be measured while moving the object to be measured on the conveyor in order to solve the above-described problem. Measuring the radiation dose emitted from the measurement object while changing the measurement site in accordance with the movement of the measurement object, monitoring the rising trend of the measurement signal from the measurement object to be measured, and increasing the measurement signal A motor control to decelerate, switch or stop the conveyor speed when a trend is recognized, and to decelerate, switch or stop the conveyor speed when a rising trend of the measurement signal is recognized from the object to be measured In this method, the amount of radiation emitted from the object to be measured is measured to determine whether the object to be measured is contaminated.

  In the surface contamination inspection apparatus and the inspection method thereof according to the present invention, the rising trend of the measured value from the radiation detecting means for measuring the emitted radiation dose while changing the measurement site according to the movement of the measurement object such as an article is monitored, When this upward tendency is recognized, the conveyor speed can be reduced or stopped to make a precise measurement, and the presence or absence of contamination of the object to be measured can be accurately and efficiently determined.

  Embodiments of a surface contamination inspection apparatus and an inspection method thereof according to the present invention will be described with reference to the accompanying drawings.

  FIG. 1 and FIG. 2 are a plan view and a side sectional view showing a first embodiment of a surface contamination inspection apparatus according to the present invention. The surface contamination inspection apparatus 10 is applied to an article removal monitor apparatus that performs a radiation contamination inspection while an object to be measured 11 such as an article or member carried out from a radiation control area is mounted on a conveyor 12 and continuously moved. 11 is used as a surface contamination measuring device.

  The surface contamination inspection apparatus 10 has a conveyor 12 for carrying out the object to be measured provided in an article conveyance path 13 for carrying out the object to be measured from a radiation management area such as a nuclear facility. A flexible endless conveyor belt 16 is wound around the conveyor 12 between the driving roller 14 and the driven roller 15, and the object to be measured 11 is placed on the conveyor belt 16 and conveyed. .

  The drive roller 14 of the conveyor 12 is rotationally driven by a drive motor 19 that is controlled by acceleration / deceleration (variable) by a motor speed controller 18 as a motor speed control means, and the conveying speed of the conveyor belt 16 is driven by the motor of the drive motor 19. Is controlled. The operation of the motor speed controller 18 is controlled by a control signal from the process control display device 20 which is a monitoring determination unit. As the drive motor 19, for example, a reversible motor is used.

  The processing control display device 20 is connected to a pair of radiation detectors 23 (23a, 23b) as radiation detection means. The radiation detectors 23 are installed in pairs so as to bend the object to be measured 11 conveyed on the conveyor belt 16. The radiation detection signal detected by the radiation detector 23 is input to the processing control display device 20 for signal processing, and the processing result is displayed on the display unit of the processing control display device 20 as a radiation count rate value.

  Further, the presence or absence of passage of the measurement object 11 is detected by the position detection sensors 25 and 26 in the measurement object 11 conveyed on the conveyor belt 16. As the position detection sensors 25 and 26, for example, a light transmission type detection sensor is used. However, a reflection type detection sensor may be used, and the position detection sensors 25 and 26 are arranged in the longitudinal direction of the conveyor belt 16 at a predetermined interval. The position detection sensors 25 and 26 are disposed, for example, on the entrance side and the exit side of the radiation detectors 23a and 23b, respectively.

  The conveyor belt 16 may be formed of a flexible belt-like belt or chain, and the portion on which the object to be measured 11 is placed may be formed of a gold steel shape. The conveyor belt 16 is formed by wrapping a plurality of belt belts, for example, narrow belt belts on the left and right sides, passing a support wire between the belt belts, and a plurality of small rollers on the belt belts. It may be arranged and a wire mesh tray placed on a small roller. By providing the conveyor belt 16 with a wire mesh tray, the presence or absence of surface contamination can be detected even in the case of the object to be measured 11 that emits radiation with low transmission power from the lower surface of the object to be measured 11 by the radiation detector 23 installed below. It can be detected accurately.

  The object to be measured 11 is conveyed on the conveyor 12 by the operation of the surface contamination inspection apparatus 10 shown in FIGS. When the tip of the object to be measured 11 reaches the position of the position detection sensor 25 for starting measurement, the surface contamination of the object to be measured 11, that is, measurement of the emitted radiation dose is started, and measurement signals are received from the radiation detectors 23 a and 23 b. Is output.

  Further, when the rear end of the object to be measured 11 passes the position of the position detection sensor 26 for measurement completion, the radiation measurement by the surface contamination inspection apparatus 10 is completed.

  The surface contamination inspection apparatus 10 performs radiation measurement while a part or all of the object to be measured 11 exists in a measurement area defined by the position detection sensors 23a and 23b. The measurement is interrupted.

  On the other hand, when the position detection sensor 23a for starting measurement detects the object to be measured 11 and measurement is started, the speed of the conveyor 12 is initialized to a predetermined value, and the conveyor belt 16 is driven to travel. Here, the predetermined value is not the background count rate (BG value) before the start of measurement by the surface contamination detection device 10, but a numerical value calculated using the following detection limit expression that displays the radiation detection sensitivity calculation expression. Say.

The detection limit A based on the detection sensitivity calculation formula is

It is represented by Here, the unit (cps) represents count / sec.

  Next, the operation of the surface contamination inspection apparatus 10 according to the present invention will be described.

  The surface contamination inspection apparatus 10 moves when the measurement object 11 enters the measurement area of the conveyor 12 as the measurement object 11 such as an article conveyed on the conveyor belt 16 of the conveyor 12 moves. The radiation detector 23 (23a, 23b) measures the radiation dose emitted from the device under test 11 while relatively changing the measurement site of the device under test 11 and moves the measurement signal (measured value). The data is output to the process control display device 20 as a monitoring determination unit.

  When a measurement signal (radiation count rate value signal) from the radiation detector 23 (23a, 23b) that measures the radiation dose emitted from the object to be measured 11 is input to the processing control display device 20, the processing control display device 20 The rising tendency of the measurement signal (radiation count rate value signal) from the detector 23 (23a, 23b) is monitored, and when the rising tendency is recognized, a control signal is output to the motor speed controller 18, and this motor The speed controller 18 controls the motor so that the motor drive of the drive motor 19 is decelerated or stopped.

  By the motor control of the drive motor 19, the conveyor belt 16 of the conveyor 12 is caused to reduce (decelerate) the conveyor speed, and the amount of radiation emitted from the measurement object 11 on the conveyor 12 is radiated while the conveyor speed is reduced. Precise measurement is performed with the detector 23 over time, and the presence / absence and degree of radiation contamination are judged by the processing control display device 20 and displayed on the display unit.

  In the surface contamination inspection apparatus 10, when the measurement signal (measurement value: radiation count rate value signal) from the radiation detector 23 (23a, 23b) shows an upward tendency during the surface contamination measurement of the object 11 to be measured, The process control display device 20 monitors the upward trend, and when the upward trend of the measurement signal exceeds a required value, the motor speed controller 18 is controlled to operate, and the drive motor 19 is controlled to decelerate or stop.

  By the deceleration / stop control of the drive motor 19, the conveyor 12 can reduce or stop the conveyor speed. As shown in FIG. 3, the conveyor 12 is controlled in normal measurement mode operation (for example, the conveyor speed exceeds 20 mm / sec and is controlled to about 200 mm / sec, preferably 80 mm / sec, as shown in FIG. 3). ) Enters contamination measurement mode operation (for example, the conveyor speed is controlled to 0 to 20 mm / sec, preferably 20 mm / sec), and precise measurement over time with high radiation measurement accuracy is stably performed in the contamination measurement mode operation. It is.

  FIG. 3 is a time chart schematically showing the measurement operation by the surface contamination inspection apparatus 10.

[Normal measurement mode]
As can be understood from this time chart, the measurement of the object to be measured 11 conveyed on the conveyor 12 is started in the normal measurement mode. In the normal measurement mode, the contamination measurement is performed in a state where the conveyor speed v is high and the probability that a false alarm is transmitted is high and the reliability factor k is low. The symbol P in FIG. 3 is measurement data in the normal measurement mode, and it can be seen from the measurement data P that the data varies greatly during the normal mode operation and the reliability is low. Further, symbol Q is measurement data in the contamination measurement mode, and the data variation in the contamination measurement mode is small from the measurement data Q, indicating that the reliability is high.

  In the normal measurement mode operation by the surface contamination inspection apparatus 10, for example, when the reliability factor k = 1.5 and the detection limit A = 0.8 are set, the measurement time Ts is 5 seconds and the conveyor speed v is 80 mm / sec. Radiation measurement of the DUT 11 can be performed at high speed.

[Contamination measurement mode]
When an upward trend is recognized in the measurement signal (radiation count rate value signal) from the radiation detector 23 measured in the normal operation mode, the processing control display device 20 automatically determines and processes this upward trend. When the processing control display device 20 determines that the object to be measured 11 is likely to be contaminated, the operation is switched to the contamination measurement mode with a high reliability k although the conveyor speed v is slow.

  In this contamination measurement mode, for example, when the reliability factor k = 3 (3σ) and the detection limit A = 0.8 is set, the measurement time Ts is about 20 seconds and the conveyor speed v is 20 mm / sec. By operating the surface contamination inspection apparatus 10 in this contamination measurement mode, it is possible to accurately measure the presence / absence / degree of radiation contamination of the measurement object 11 with high accuracy and efficiency over time.

[Determining whether the measurement signal from the radiation detector shows an upward trend]
The method of determining whether or not the measurement signal (radiation count rate value signal) from the radiation detector 23 shows an upward trend is that the current measurement value exceeds the previous measurement value at the radiation detector 23, When this higher measurement result is continued N times (N ≧ 2), it is determined that the measurement signal (radiation count rate value signal) tends to increase as shown in FIGS.

  Apart from the determination of the increasing tendency of the counting rate, it can also be determined that the measurement signal from the radiation detector 23 is increasing with the determination method shown in FIG. In the determination method shown in FIG. 5B, when the radiation count rate reaches a predetermined forecast set value and the state where the forecast set value is reached N times (N ≧ 2), the count rate tends to increase. Judge that there is.

  When the processing control display device 20 automatically determines that the measurement signal (radiation count rate value signal) from the radiation detector 23 tends to increase, a control signal is output to the motor speed controller 18, and this motor speed. The controller 18 decelerates or stops the motor drive of the drive motor 19. By the motor drive control of the drive motor 19, the conveyor speed of the conveyor 12 is controlled to be reduced or stopped from the normal set speed. At this time, the conveyor speed of the conveyor 12 is controlled in accordance with the speed setting formula shown in FIG.

By the speed setting formula of the conveyor 12, the conveyor speed v is

It is represented by

  When the rising trend of the measurement signal (radiation count rate value signal) from the radiation detector 23 (23a, 23b) continues further, an alarm is issued as shown in the flowchart of FIG. The measurement by is completed.

At that time, the final contamination warning from the surface contamination inspection apparatus 10 is determined based on the value of k = 3 (3σ), which has a high reliability factor k. 3σ indicates the degree of deviation value in the Gaussian distribution.

  If the reliability factor k is set low, the probability of issuing a false alarm at the safe side increases, but the conveyor speed v can be set fast, improving the processing efficiency and reducing the contamination state of the DUT 11 in a time-saving and efficient manner. Can be measured.

  On the other hand, when an increasing tendency of the measurement signals (radiation count rate value signals) from the radiation detectors (23a, 23b) is recognized, the reliability factor k is set to be high (k = 3 (3σ)) and more accurate. It is possible to carry out radiation measurement with precise time.

  This surface contamination inspection method for the measurement object 11 is a method for detecting and measuring the radiation dose emitted from the measurement object while moving the measurement object 11 on the conveyor 12.

  In this surface contamination inspection method, a step of measuring the radiation dose emitted from the measurement object 11 while changing the measurement site in accordance with the movement of the measurement object 11, and a rising tendency of the measurement signal from the measurement object 11 to be measured And a step of controlling the motor so as to decelerate or stop the conveyor speed when a rising trend of the measurement signal is recognized, and when a rising trend of the measurement signal from the object to be measured 11 is recognized, This is a measurement method in which the conveyor speed is decelerated or switched or stopped and the amount of radiation emitted from the object to be measured 11 is measured to determine the presence or degree of contamination of the object to be measured.

  Further, in the surface contamination inspection apparatus 10 for the object to be measured 11 and its inspection method, if the reliability k is set low, the probability of issuing a false alarm on the safe side increases, but the processing speed can be increased and there is no radiation contamination. Therefore, it is possible to realize time-saving and efficient measurement. When an upward trend is observed in the measurement signal from the radiation detector 23, the reliability k is set high (k = 3) to 3σ, and it is possible to stably perform more accurate and precise inspection with high reliability over time. it can. It realizes an efficient and rational surface contamination inspection method, and has a great commercial advantage.

  According to the surface contamination inspection apparatus 10 and the inspection method thereof, the contamination inspection (radiation measurement) of the object to be measured 11 can be performed efficiently and rationally, and by realizing an efficient and rational contamination inspection method. There are also significant commercial advantages.

  Next, a second embodiment of the surface contamination inspection apparatus will be described with reference to FIG.

  FIG. 6 is a flowchart showing a second embodiment of the surface contamination inspection apparatus according to the present invention, and the apparatus configuration of the surface contamination inspection apparatus is not different from the surface contamination inspection apparatus 10 shown in FIGS. 1 and 2. Therefore, the same components are denoted by the same reference numerals and description thereof is omitted.

  This surface contamination inspection apparatus decelerates the conveyor 12 when a rising tendency of the measurement signal (radiation detection signal, radiation count rate value signal) detected by the radiation detector 23 is confirmed. Even if the conveyor 12 is set to decelerate, if the upward trend of the radiation count rate continues, the conveyor 12 is stopped, and the overrun time (conveyance time) from the detection of contamination of the measured object 11 to the determination is determined. Then, the conveyor 12 is reversely operated to reverse the contamination detection point (section where contamination is estimated). That is, a control signal is output from the process control display device 20 to the motor speed controller 18 so as to return the conveyor 12 to the contamination position estimated by the moving speed and the delay time.

  The motor speed controller 18 controls the motor drive of the drive motor 19 to rotate it reversely to reversely operate the conveyor 12 and return the object to be measured 11 (conveyor 12) to the section where contamination is estimated. The re-measurement of the radiation dose emitted from the device under test 11 is performed, or the radiation measurement of the device under test 11 including this re-measurement is continued.

  This surface contamination inspection apparatus is effective when the radiation contamination range of the object to be measured 11 is narrow, and it is possible to realize the contamination inspection of the object to be measured 11 so as not to miss the radiation contamination section.

1 is a schematic plan view showing a first embodiment of a surface contamination inspection apparatus according to the present invention. FIG. 2 is a side sectional view taken along line AA in FIG. 1. The time chart which shows the concept of the contamination measurement of the to-be-measured object by the surface contamination inspection apparatus which concerns on this invention. Explanatory drawing of the switching by the reliability factor k in the contamination measurement of the to-be-measured object using the surface contamination inspection apparatus which concerns on this invention (When reliability factor k is high and k = 3 (3 (sigma)) setting, reliability factor k is low = 1. (Explanatory diagram showing comparison of NET count rate distributions when .5 (1.5σ) is set). (A) is a flowchart showing conveyor speed control in the surface contamination inspection apparatus according to the present invention, and (B) and (C) are methods for determining a rising tendency of a measurement signal (radiation count rate value signal) from the radiation detection means. The figure which each shows, (D) is a figure which shows the said conveyor speed setting type | formula. The flowchart figure which shows 2nd Embodiment of the surface contamination inspection apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Surface contamination inspection apparatus 11 Measured object 12 Conveyor 13 Article conveyance path 14 Drive roller 15 Followed roller 16 Conveyor belt 18 Motor speed controller (motor speed control means)
19 Drive motor 20 Processing control display device (monitoring judgment means)
23 (23a, 23b) Radiation detector (radiation detection means)
25 Position detection sensor 26 Position detection sensor

Claims (6)

In a surface contamination inspection device that measures the amount of radiation emitted from a measurement object while moving the measurement object on a conveyor,
Radiation detection means for measuring the radiation dose emitted while changing the measurement site according to the movement of the object to be measured;
Monitoring determination means for monitoring the upward trend of the measurement value from the radiation detection means;
A motor speed control means for controlling the conveyor driving motor so as to decelerate, switch or stop the conveyor speed when an upward trend of the measured value is recognized by the monitoring judgment means;
When the monitoring judgment means shows an upward trend in the measured value, the conveyor speed is reduced, switched or stopped, and the radiation dose from the measurement object is measured to determine whether the measurement object is contaminated. Surface contamination inspection device characterized by being set to. The monitoring judgment means judges the upward trend of the measurement value from the radiation detection means by the rate of change of the radiation count rate value, and outputs a control signal for changing or stopping the conveyor speed to the motor control means. The surface contamination inspection apparatus according to claim 1. The monitoring judgment means judges the increasing tendency of the measured value from the radiation detection means based on the number of times the radiation count rate signal exceeds a predetermined alarm set value, and outputs a control signal for changing or stopping the conveyor speed to the motor control means. The surface contamination inspection apparatus according to claim 1, characterized in that: The monitoring determination means sets the conveyor speed, which is variably controlled according to the rising tendency of the measurement value from the radiation detection means, to a value that can obtain a measurement time given by a reliability factor of statistical probability that satisfies a predetermined radiation detection sensitivity. 3. The surface contamination inspection apparatus according to claim 1, wherein the surface contamination inspection device is set and continuously measures the radiation dose from the object to be measured. The monitoring judgment means outputs a control signal to the motor control means so as to return the conveyor to the contamination position estimated by the moving speed and the delay time when the upward trend of the measurement value from the radiation detection means is recognized. 2. The surface contamination inspection apparatus according to claim 1, wherein radiation measurement of the object to be measured is continued. In the surface contamination inspection method for measuring the radiation dose emitted from the object to be measured while moving the object to be measured on the conveyor,
Measuring the amount of radiation emitted from the measurement object while changing the measurement site according to the movement of the measurement object;
Monitoring the upward trend of measured values from the measured object;
Motor control to reduce or switch or stop the conveyor speed when an upward trend of the measured value is recognized,
When an upward trend of the measured value is recognized from the measured object, the amount of radiation emitted from the measured object is measured by decelerating, switching or stopping the conveyor speed to determine whether the measured object is contaminated or not. A characteristic surface contamination inspection method.

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