JPS586909B2 - Dust “Ai” radioactivity monitoring device - Google Patents

Description

[Detailed description of the invention] The present invention relates to a dust radioactivity monitoring device.

This type of conventional dust radioactivity measuring device has a configuration as shown in FIG.
The sample is made into a constant flow rate and sampled onto the filter paper 13.

This sampling time T is determined by the time set by the marker 14. At that time, the filter paper is kept stationary at the position of the radiation detector 15, and is then moved when the dust collection is completed to sample and collect the gas at the next measurement location. Solenoid valve 1 to dust
1a, 11b, 11c and filter paper 13 are controlled by a control device 16.

The output of the detector 15 when measured under such control has an output pattern as shown in FIG. 2 over time.

That is, the detector output gradually rises from the start of dust collection, reaches its maximum when the time T set by the timer has elapsed, and returns to the level at which there is no dust collection radioactivity due to the movement of the F paper.

The gas measurement at the next measurement location also gradually increases from the start of dust collection, and reaches its peak when the time T set by the timer has elapsed.

Since the value at this highest point is proportional to the dust radioactivity concentration in the sampled gas, monitoring this value makes it possible to monitor the dust radioactivity concentration at each location.

However, when measuring with an apparatus configured in this way, there are the following drawbacks.

■Results cannot be known until after the set dust collection time has elapsed, regardless of whether the dust radioactivity concentration is high or low.

■ As the radioactivity concentration in dust increases, the radioactivity intensity to the detector increases proportionally, so if a Geiger-Mueller counter (GM counter) is used for the detector, for example, it may cause missed counts or the phenomenon of breathing. This may increase errors and shorten the life of the detector.

■ The radioactivity intensity accumulated on the r paper after dust collection is proportional to the dust radioactivity concentration in the gas at the measurement location, so the next measurement value after the previous high concentration dust collection measurement , the radiation emitted from the radioactivity accumulated on paper E the previous time penetrates the shield and acts on the detector, and the calculated value includes that amount,
The purpose of the present invention, which may cause measurement errors, is to measure the radioactivity intensity of collected dust at a certain value or below a certain value, that is, the time from the start of dust collection until it reaches a preset value, and to calculate the measured value and arrival time. To provide a dust radioactivity monitoring device which determines the radioactivity concentration in dust from the above and prevents unnecessary accumulation of radioactivity on furnace paper.

An embodiment of the present invention will be described below with reference to the drawings, in which devices having the same functions as those in FIG. 1 are designated by the same reference numerals.

The device of the present application includes a device that samples gas at each measurement point on the filter paper 13, a circuit that measures radiation of dust on the sampled filter paper, and a device that uses the sampling device and the F paper drive device based on the output of the radiation measurement circuit. The sampling device is configured to collect dust under certain conditions from the gas at the location to be measured, and includes a pump 12 that suctions at a constant flow rate and a plurality of electromagnetic valves 13a, 13b, 13.
c. Under the control of the control device 16', the solenoid valve corresponding to the location to be measured is operated for a certain period of time from among the plurality of solenoid valves, and the gas at each measurement point is collected on the furnace paper. do.

The radiation measurement circuit includes a radiation detector 15 for detecting radioactivity collected on paper F, a level setter 17, a comparison circuit 18, and a time measurement circuit 19, and assumes that the radiation detection output level is greater than the level setting signal. The discrimination signal is given to the control device 16' as a control command for the next step, and the discrimination signal is given to the time measurement circuit 19 to which the dust collection start time signal of the control device 16' is given, so that the dust collection start time is determined. The control device 16', which measures the time spent at the set level based on the time and level arrival time, receives a control command signal for the radiation measurement circuit and sends a signal to the sampling device to open the solenoid valve corresponding to the next measurement point. , a signal for feeding out a predetermined amount of furnace paper and keeping it stationary to the furnace paper drive device 20, and a dust collection start time signal to the time measuring circuit 19, respectively.

Note that the output of the time measurement circuit 19 and the level setting circuit 17
The level signal is led to a calculation unit 21 which calculates the radioactivity intensity and outputs the result to a recorder 26.

The operation of the device configured in this way will be explained.

When the comparison circuit 18 issues a control command signal for the next step, the control device 16' gives a signal to the filter paper drive device 20, the sampling device and the time measurement circuit 19 to measure the gas at the next measurement point. .

A filter paper 13 that is not yet contaminated is placed at the position of the radiation detector 15.
is sent and stopped, the pump 12 is also activated, and the gas at the next measurement point begins to be collected on the filter paper through the opened electromagnetic valve corresponding to the next measurement point.

As time passes, the amount of collected dust increases, and if it contains radioactive substances, the output level of the radiation detector 15 increases, and when it reaches a predetermined set level, the comparator circuit 18 controls the amount of dust collected. A control command signal for the next step is given to the device 16', and a level arrival time signal is given to the time measuring circuit 19.

In response to this signal, the plow control device 16' provides a signal to the filter paper drive device 20, the sampling device, and the time measuring circuit 19 with an initial state command.

If such control is performed, the output of the radiation detector will have a pattern as shown in FIG. 4, and the final level of radiation detected by the radiation detector 15 will not exceed the set level.

If so, the intensity of the radiation collected on the furnace paper will not exceed the set level of radioactive material.

The strength of radioactivity contained in the gas dust collected at each measurement point is
The set level value and the time required to reach the predetermined level measured by the time measuring circuit are substituted into the calculation formula as variables, and the calculation unit 21 calculates the value, and records the value on the recording paper.

With this configuration, ■ If the radioactivity concentration of the gas being sampled is high,
In FIG. 4, the pattern is 22, and when the concentration is low, the pattern is 23. Therefore, the higher the concentration, the shorter the time it takes to reach the set level, making it possible to collect dust in a short time.

In addition, in many cases, a single monitoring device monitors dust radioactivity in multiple rooms by switching solenoid valves, which takes a lot of time for one measurement cycle, but with this invention, the concentration There is an advantage that the higher the value, the shorter the time required for one cycle of measurement.

■ As shown in Figure 4, even if the radioactivity concentration in the dust increases, the radioactivity concentration collected on the door paper remains constant, and the amount of collected dust is determined by the limit that can be detected by the detector and the measurement error. As long as it is within the permissible range of
Even if a tube is used, measurements can be made without reaching the breathing area of the detector, and the amount of radiation irradiated to the detector is small, which has the advantage of extending the life of the GM counter tube.

■ Since the required amount of collected dust is within the limit that can be detected by the detector and the allowable range of measurement error, there is less shielding of radiation from the previously collected radioactivity, and the dust radioactivity concentration can be reduced. Since the amount of dust collected is the same whether the temperature is high or low, it has the advantage that even if there is an influence, it remains constant and is easy to evaluate.

As described above, the present invention detects that the radioactivity intensity of the substance collected on the filter paper has reached the set intensity, collects the gas at the next measurement point on a new filter paper, and sets the setting after starting the dust collection. Since the circuit is configured to measure the radioactivity concentration of the gas, the higher the radioactivity concentration at each measurement point, the more time it takes to reach the set level. If the setting level is set based on the good characteristics of the radiation detector, it is possible to measure the radioactivity concentration accurately without the phenomenon of breathing or miscounting. Since the concentration does not exceed the set concentration, the influence of the radioactivity collected on the tear paper last time and the time before the previous time is small, and the radioactivity concentration collected on the filter paper remains constant even if it is affected, so compensation is not required. easy to do,
More accurate measurement results can be obtained.

In the present invention, it is described that when the level of the radiation detector exceeds the level of the level setting device, the next step is to collect the next gas on the E paper, but the radioactivity collected on the filter paper is If the concentration of gas is low or the half-life is short, a phenomenon may occur in which the set level is not reached at any time. If a control command for forcibly proceeding to the next step is given to the control device 16' after the set time of the timer, the measurement time can be managed even more easily.

In addition, the background level subtractor or baseline shift circuit 25 is connected to the detector 15 and the detector output comparison judgment circuit 1.
8 or between the level setting device 17 and the arithmetic circuit 21, the background level unrelated to dust collection can be subtracted and the value output purely based on the radioactivity in the dust. By calculating the arrival time from the start of dust collection until reaching that value, it is possible to correct measurement errors caused by the presence of background.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the configuration of an embodiment of a conventional dust radioactivity monitoring device, Fig. 2 is a diagram illustrating the output of the detector in the operation of Fig. 1, and Fig. 3 is an embodiment of the present invention. Figure 4 is a diagram showing the configuration of the detector, Figure 5 is a diagram for explaining the output of the detector,
FIG. 6 is a diagram showing another embodiment. 13...Filter paper, 15...Radiation detector, 16'...Control device, 17...Level setter, 18...Comparison Circuit, 19...
・Time measurement circuit, 20... Teardrop drive device, 21
......Calculation unit, 26...Recorder.

Claims (1)

[Claims] 1. Collect the gas at the selected measurement point on the furnace paper, measure this dust with a measurement circuit including a radioactivity detector, and then collect the gas at the next measurement point on the discharged furnace paper. In a device that measures the radioactivity of the dust and measures the radioactivity concentration of the gas at each measurement point, the measurement circuit includes a setting circuit that sets the radioactivity level, and a setting value that sets the output value of the radioactivity detector. A measuring device that measures the time from the start of dust collection until the output of the radiation measuring device reaches the set value, and a measuring device that measures the amount of dust collected on P paper based on the set level and the output of the time measuring device. It is characterized by comprising an arithmetic circuit for calculating the radioactivity concentration contained in the gas at a point, and controlling a filter paper feeding mechanism based on a comparison judgment signal so as not to collect gas having a radioactivity concentration higher than a predetermined value on the filter paper. Dust radiation monitoring device.