JP3373642B2 - Dust radiation monitor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dust radiation monitor used in a radiation handling facility such as a nuclear power plant, and more particularly to a dust radiation monitor which is small and lightweight and easy to handle.

[0002]

2. Description of the Related Art A mobile dust radiation monitor is installed at various places in a nuclear facility to collect dust radioactivity contained in the air and to determine the state of radioactivity in the air from the dust radioactivity concentration of the collected sample. It is being managed. In general,
This dust radiation monitor connects a pump to the sampling pipe, collects dust in the air with a filter paper installed in the sampling pipe, measures the radiation contained in the dust, and measures the radiation in the air based on its intensity. It is a method to measure the radioactivity concentration of.

FIG. 6 is a block diagram of a conventional dust radiation monitor. This dust radiation monitor sucks the air to be measured into the piping system including the dust collecting portion by the suction force of the pump 51, and at the same time, the flow rate adjusting valve so that the flow rate detected by the flow meter 52 installed in the piping system becomes constant. Adjust 53. At this time, when the filter paper 54, which is a dust collecting member, is continuously fed by the filter paper constant speed drive unit 55, dust is collected on the filter paper surrounded by the shielding lead 56. Radioactivity in the collected dust is detected by the radiation detector, and its output is measured by the counting rate meter 57. This counting rate is proportional to the dust radioactivity concentration, so
This is multiplied by a proportional constant and displayed as the dust radioactivity concentration on the display unit 58. At this time, the display unit 58 continuously displays the radiation count rate or the radioactivity concentration as an instantaneous value. Therefore, this dust radiation monitor is of a type in which the filter paper is continuously fed at a constant speed.

[0004]

By the way, in the above-mentioned dust radiation monitor for continuously sending the filter paper, since the output result is continuously displayed, the time constant of the counting rate meter is short. Also,
Since the filter paper is sent continuously, the amount of dust collected on the filter paper is small. Under such conditions, from the viewpoint of ensuring detection sensitivity, thicken the shielding lead in order to remove radiation other than the sample to be measured, and reduce the suction capacity of the pump to collect a large amount of dust in a short time. Must be big.

Therefore, in the dust radiation monitor of the type in which the filter paper is continuously moved, the thickness of the shielding lead is increased to about 30 to 50 mm in order to satisfy the above-mentioned requirements.
A large pump is used to secure a large sampling amount (about 200 l / min). As a result, the entire device becomes larger (up to 1500 W x 1000 D x 1000 H
[Mm]), and the weight was about 200 kg. The present invention has been made in view of such a situation, and an object thereof is to provide a dust radiation monitor that is lightweight, has excellent portability, and can improve detection accuracy.

[0006]

In order to achieve the above object, the invention according to claim 1 collects dust in the air to be measured on a dust collecting member to count radiation, and counts this radiation value. In the dust radiation monitor for continuously monitoring by calculating the dust activity concentration of the measured air based on the above, the dust collecting member driving means for intermittently moving the dust collecting member is different from the dust collecting member driving means.
Under the following environment, the dust is collected and accumulated on the dust collecting member while the dust collecting member is stopped by the dust collecting member driving means, and the radiation of the accumulated dust is counted and integrated, and the counted integrated value and the measured air are measured. It is calculated in consideration of the half-life effect of substances contained in the product and the elapsed time from the start of dust collection.
Save multiple correction factors and use the same environmental conditions as the above environmental conditions.
If there is a case,
It is a dust radiation monitor provided with a radioactivity concentration calculation means for continuously calculating the dust radioactivity concentration using a correction coefficient corresponding to the environmental conditions .

[0007]

Further, in the invention according to claim 2 , the dust in the air to be measured is collected on the dust collecting member to count the radiation, and the dust radioactivity concentration of the air to be measured is determined based on the counted value. A dust radiation monitor for calculating and continuously monitoring is provided with a calibration dust radiation monitor and a calibration dust radiation monitor, and the calibration dust radiation monitor collects dust in the measured air. First dust collecting member driving means for intermittently moving the dust member, and the dust is accumulated and accumulated on the dust collecting member while the dust collecting member is stopped by the first dust collecting member driving means, and Radiation of accumulated dust is cumulatively counted, and the dust radioactivity concentration, which is the calibration data, is continuously calculated by using the count cumulative value and the first correction coefficient obtained in advance in a state where the correct radioactivity concentration can be calculated. , Said cover A first radioactivity concentration calculating means for transmitting to a positive dust radiation monitor, and the dust radiation monitor for calibration intermittently moves a dust collecting member for collecting dust in the air to be measured. Second dust collecting member driving means, receiving means for receiving the calibration data transmitted from the calibration dust radiation monitor, and the dust collecting while the dust collecting member is stopped by the second dust collecting member driving means. Dust is accumulated and accumulated on the member, and the radiation of the accumulated dust is counted and integrated.In consideration of this accumulated count value, the half-life effect of substances contained in the measured air, and the elapsed time from the start of dust collection. In synchronization with the second radioactivity concentration calculation means for continuously calculating the dust radioactivity concentration using the obtained second correction coefficient, the calibration data received by the receiving means, and the received calibration data. The second A correction coefficient calibration storage means for calibrating and storing the second correction coefficient on the basis of the dust radioactivity concentration calculated by the radioactivity concentration calculation means is provided, and the correction coefficient calibration storage means is provided when measuring the radioactivity concentration. It is a dust radiation monitor that continuously calculates the dust radioactivity concentration based on the correction coefficient that is calibrated and stored in.

[0009]

Therefore, in the invention corresponding to claim 1, since the dust collecting member is moved intermittently by the dust collecting member driving means, the dust collecting member is stopped while the dust collecting member is stopped. Dust is continuously collected and accumulated, and with it,
The radiation of accumulated dust can be counted and integrated. That is, by considering the integration of each count rate that is continuously measured, it is possible to cancel the dispersion of the individual measurement results. Further, since the dust is accumulated and accumulated, the counting rate measurement error decreases as the amount of accumulated dust increases. Due to such an accumulation effect of counting and an accumulation effect of dust, the dust radioactivity concentration can be detected more accurately than in the conventional method.

However, by intermittently operating the dust collecting member, the half-life of radioactivity cannot be ignored in the dust collecting time. Therefore, the effect of elapsed time is compensated by using a correction coefficient that takes into account the half-life and the like, instead of multiplying the count rate by a mere proportional constant as in the conventional case. And although the dust collection and counting are accumulated, the dust radioactivity concentration is continuously calculated, so it is possible to continuously display the dust radioactivity concentration that reflects the current air dust radioactivity concentration. The state of the radiation concentration of the measured air can be grasped.

Moreover, even when the dust radioactivity concentration is measured with a detection accuracy equal to or higher than that of the conventional one, the sampling amount is small, the shielded lead can be thinned, and the pump can be downsized, which is small and lightweight and portable. Can be excellent.

[0012]

Further, in the invention according to claim 2, a dust radiation monitor using a correction coefficient which is known in advance to be able to calculate an accurate dust radioactivity concentration is used as a calibration device, and the dust radiation monitor from this calibration device is used. If the measurement result is used as calibration data and the calibration data is compared with the dust activity concentration measured by the dust radiation monitor for calibration in synchronization with the calibration data, the correction coefficient in that environment can be easily calculated. Required to. Therefore, normally, the radioactivity concentration can be accurately measured by using the newly obtained correction coefficient at the time of measurement.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a block diagram showing an embodiment of a dust radiation monitor according to the present invention. This dust radiation monitor includes a pump 1 for sucking air to be measured through a piping system including a dust collecting unit, a flow rate transmitter 2 for measuring an air flow rate and sending out the measured value, and a dust in the sucked air. Filter paper 3 which is a dust collecting member for collecting dust, filter paper drive unit 4 which is a dust collecting member driving means for intermittently moving filter paper 3, and filter paper 3
A radiation detector 5 that detects radiation from the dust collected above, and a radioactivity concentration is calculated based on the detection output from the radiation detector 5, the flow rate from the flow rate transmitter 2 and the correction coefficient and displayed on the display unit 6. The data processing unit 7 is a radioactivity concentration calculating means. Further, the shielding lead is thinned or removed to the extent that the dust radioactivity concentration can be measured with a detection accuracy equal to or higher than the conventional one, and the pump is further downsized.

Next, the operation of the dust radiation monitor thus constructed will be described. Filter paper 3 with filter paper drive unit 4
After being moved, the pump 1 sucks the measured air during the stop period of the filter paper 3 to continuously collect and accumulate dust on the filter paper 3.

At this time, since the dust radiation is continuously measured, the data processing unit 7 can cancel the dispersion of the individual measurement results by considering the integration of each count rate in the continuous measurement. Furthermore, since the dust is collected and accumulated, the measurement error of the count rate becomes smaller as the amount of accumulated dust increases. Here, the dust radioactivity concentration is calculated based on the correction coefficient that takes into account the elapsed time from the start of dust collection and the flow rate value from the flow rate transmitter 2. Therefore, from such a function, the detection accuracy of the radioactivity concentration can be improved.

Since the dust radioactivity concentration is continuously calculated, the dust radioactivity concentration reflecting the present air dust radioactivity concentration is continuously displayed. Next, the concept of the correction coefficient will be described in detail with reference to FIGS. 2 and 3.

In the monitor of the present invention, after the filter paper 3 is intermittently operated, dust is continuously collected on the stopped filter paper 3. Therefore, the dust collection time is long and the half-life of radioactivity cannot be ignored. Therefore, instead of multiplying the count rate by a mere proportional constant as in the prior art, a correction coefficient that takes the half-life into consideration is used to compensate for the effect of the passage of time.

That is, in FIG. 2, when the half-life of the measured dust is infinite (Z in FIG. 2), the count rate measured is proportional to the elapsed time. In addition, when the half-life is short (X in FIG. 2), the increase of the counting rate becomes gradually slower with the passage of time. Further, for example, when a substance having a long half-life and a substance having a short half-life are mixed (Y in FIG. 2), the increase in the count rate also gradually slows, but the increase in the count rate becomes slower as in the case of X. I won't.

When the count rate curve has the characteristics shown in X, Y, and Z as described above, the correction coefficient characteristics are X and Y in FIG. 3, respectively.
Given as indicated by Y, Z. However, it is not easy to find out what kind of count rate curve it has under a certain environment, and a correction coefficient is created by repeating trial and error to some extent. However, once the correction coefficient is created, it is possible to calculate the correct radioactivity concentration with the correction coefficient under the same environment. Therefore, this correction coefficient is saved and used again in the same environment. .

As described above, according to the present embodiment, the dust collecting member is intermittently sent out to accumulate the count and the dust, and use the correction coefficient in consideration of the influence of the half-life with the passage of time. Since the radioactivity concentration is compensated, the detection accuracy increases.
This means that even if the dust radioactivity concentration is measured with the same or higher detection accuracy as in the past, the sampling amount is small and the shielded lead can be thinned and the pump can be miniaturized. Can be lighter,
The portability can be improved. The dust radiation monitor of the present embodiment can be reduced in total weight to about 50 to 60 kg, and the flow rate transmitter 2 is used to send the flow rate to the data processing unit 7. Therefore, the flow rate required for the conventional monitor. The control valve can be deleted, and the dust radioactivity concentration can be calculated correctly even if the flow rate fluctuates for some reason.

Next, another embodiment of the present invention will be described. FIG. 4 is a configuration diagram showing another embodiment of the dust radiation monitor according to the present invention. The same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. Only different parts will be described here.

In FIG. 4, reference numeral 21 denotes a dust radiation monitor for calibration, and the data processing section 7a of this monitor receives the calibration data from the calibration dust radiation monitor 22 and calibrates the correction coefficient and the calibration. The dust radiation monitor is the same as the dust radiation monitor according to the first embodiment except that a function of storing the corrected correction coefficient is added. Further, the calibration dust radiation monitor 22 gives a correction coefficient known to calculate a correct radioactivity concentration in advance, and outputs the radioactivity concentration calculated in the data processing unit 7b, that is, the calibration data to the dust radiation to be calibrated. It has a function of sending to the monitor 21 and is mounted on the moving carriage 23. Further, the dust radiation monitor for calibration 21 and the dust radiation monitor for calibration 22 are respectively provided with air intake ports 8a and 8b for collecting the same air to be measured.

Next, the operation of the dust radiation monitor thus constructed will be described. After the same air is taken in through the air intake ports 8a and 8b, the radioactivity concentration is measured in each dust radiation monitor by the same procedure as in the previous embodiment. Here, the radioactivity concentration calculated in the calibration dust radiation monitor 22 is sent to the dust radiation monitor for calibration 21 as calibration data. The data processing unit 7a of the to-be-calibrated dust radiation monitor 21 compares the sent calibration data with the radioactivity concentration calculated by the to-be-calibrated dust radiation monitor 21 to calibrate the correction coefficient,
save.

In normal use, the dust radiation monitor for calibration calculates the radiation concentration using the correction coefficient calibrated as described above. Further, in the present embodiment, the dust radiation monitor according to the present invention is used as the calibration dust radiation monitor 22, but the calibration dust radiation monitor 22 has a function of calculating a correct radioactivity concentration and sending calibration data. It suffices to do so, and for example, a conventional dust radiation monitor of a type that continuously feeds filter paper at a constant speed, and a calibration data transmission function may be added.

As described above, according to this embodiment, the calibration dust radiation monitor 21 and the calibration dust radiation monitor 22 are provided.
Since the correction coefficient of the dust radiation monitor to be calibrated is calibrated and stored based on the calibration data from the calibration dust radiation monitor 22, the correction coefficient can be easily calibrated. The dust radiation monitor of the present embodiment is effective when there are individual differences even in the same device and it is better to slightly correct the correction coefficient, or when the conventional correction coefficient cannot be used as it is because the pump capacity is different. The dust radiation monitor of this embodiment can be reduced in total weight to about 100 to 120 kg.

Further, if a conventional dust radiation monitor of the type that continuously sends filter paper at a constant speed is used as the calibration dust radiation monitor, calibration of the correction coefficient can be further simplified.

Further, regarding the correction between the correction coefficient at a certain elapsed time and the correction coefficient at another elapsed time,
By performing the interpolation as shown in FIG. 5, a more accurate radioactivity concentration can be calculated.

[0029]

As described above in detail, according to the present invention, it is possible to provide a dust radiation monitor which is lightweight, has excellent portability, and can improve detection accuracy.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a dust radiation monitor according to the present invention.

FIG. 2 is a characteristic diagram showing the relationship between the elapsed time from the dust collection start time and the radiation count rate.

FIG. 3 is a characteristic diagram showing a relationship between a correction coefficient and an elapsed time from a dust collection start time.

FIG. 4 is a configuration diagram showing another embodiment of the dust radiation monitor according to the present invention.

FIG. 5 is a diagram showing a method of interpolation between correction coefficients by expanding the relationship between elapsed time and correction coefficients.

FIG. 6 is a configuration diagram of a conventional dust radiation monitor.

[Explanation of symbols]

1 ... Pump, 2 ... Flow rate transmitter, 3 ... Filter paper, 4 ...
Filter paper drive section, 5 ... Radiation detector, 6 ... Display section, 7, 7
a, 7b ... Data processing unit, 8a, 8b ... Air intake port, 21 ... Dust radiation monitor for calibration, 22 ... Dust radiation monitor for calibration.

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01T 1/167

Claims (2)

(57) [Claims] 1. The dust in the air to be measured is collected on a dust collecting member to count radiation, and the concentration of dust activity in the air to be measured is calculated based on the counted value and continuously monitored. In a dust radiation monitor, dust collecting member driving means for intermittently moving the dust collecting member and dust collecting on the dust collecting member while the dust collecting member is stopped by the dust collecting member driving means in different environments in advance. Multiple corrections that are calculated by accumulating and cumulatively accumulating the radiation of the accumulated dust, and taking into consideration the effect of the half-life due to the accumulated value and the substances contained in the measured air and the elapsed time from the start of dust collection. The coefficient is saved and the same as the above environmental conditions
Under the environmental conditions, among the stored correction factors
And a radioactivity concentration calculating means for continuously calculating the radioactivity concentration of dust by using a correction coefficient corresponding to the environmental conditions . 2. The dust in the air to be measured is collected on a dust collecting member to count radiation, and the concentration of dust activity in the air to be measured is calculated based on the counted value and continuously monitored. The dust radiation monitor is provided with a calibration dust radiation monitor and a calibration dust radiation monitor, and the calibration dust radiation monitor intermittently moves a dust collection member that collects dust in the measured air. First dust collecting member driving means, and the dust is accumulated and accumulated on the dust collecting member while the dust collecting member is stopped by the first dust collecting member driving means, and the radiation of the accumulated dust is counted and integrated. , The dust radiation concentration to be the calibration data is continuously calculated by using the first correction coefficient obtained in advance in a state in which the counted integrated value and the correct radiation concentration can be calculated, and the dust radiation monitor for calibration is calibrated. Sent to And a first activity concentration calculating means for, the object to be calibrated dust radiation monitor, second to move the dust collecting member to the dust collecting dust of the object to be measured in air intermittently
Dust collecting member driving means, receiving means for receiving the calibration data transmitted from the calibration dust radiation monitor, and the dust collecting member while the dust collecting member is stopped by the second dust collecting member driving means. Dust accumulated and accumulated on the top, and the radiation of the accumulated dust is counted and integrated, and it is calculated in consideration of the accumulated value and the half-life effect of substances contained in the measured air and the elapsed time from the start of dust collection. The second radioactivity concentration calculating means for continuously calculating the dust radioactivity concentration using the second correction coefficient, the calibration data received by the receiving means, and the calibration data received in synchronization with the calibration data. Correction coefficient calibration storage means for calibrating and storing the second correction coefficient on the basis of the dust radioactivity concentration calculated by the second radioactivity concentration calculating means; Proofreading A dust radiation monitor characterized by continuously calculating a dust radioactivity concentration based on a correction coefficient which has been calibrated by an existing means and stored.