JPS58106483A - Radiation measuring device - Google Patents

Abstract

PURPOSE:To improve measurement sensitivity without decreasing the moving speed of a sample of measurement by using plural radiation detectors. CONSTITUTION:Radiation from a moving sample 11 of measurement is detected by plural, e.g. two radiation detectors 12 and 13, whose detection pulses are processed by integrating circuits 18 and 19, an adding circuit 20, etc., controlled through waveform shaping circuits 16 and 17, and a timer 21 to measure the radiation. In this case, since two detectors 12 and 13 are used, integration time T is twice as long as when only one detector is used on condition that the sample speed is unchanged, thereby increasing the sensitivity by 2<1/2> times on the basis of an equation. Thus, the measurement sensitivity is improved without reducing the moving speed of the sample of measurement.

Description

[Detailed description of the invention] Technical field of invention The present invention relates to improvements in radiation measuring devices.

Technical Background of the Invention Generally, in order to measure the radiation = t of a plurality of radioactive substances, a method is used in which a radiation detector is fixed, the radioactive substance is placed on a measuring stand, and the measuring stand is passed near the radiation detector. . According to this means, radiation measurements of a large number of radioactive substances can be carried out efficiently.

Therefore, a conventional example of this type of measuring device is shown in FIG. 1 and will be explained. Reference numeral 1 denotes a measuring stand that moves at a constant speed in the direction of the arrow, and a measurement sample 2 is placed on this measuring stand 1. This measurement sample 2 is passed directly under the radiation detector 3 by the measurement stage 1 at the above-mentioned constant speed. The radiation detector 3 has a detection surface 4 having a detection length A, and when the measurement sample 2 passes through this detection surface 4, the radiation of IIJ1 measurement sample 2 is detected. And the detected radiation #violet depends on the dose.
The radiation detection signal a3 is output as a signal. The waveform of this signal is shaped by a waveform shaping circuit 5 connected to the radiation detector 3, and then integrated over a predetermined integration time by an integration counting circuit 6 connected to the shaping circuit 5 to determine the counting rate. can get.

Further, the count rate determined by the radiation detector 3 of the above-mentioned apparatus is expressed in FIG. 2, with the count rate K on the vertical axis and the time t on the horizontal axis. The shaded area in this figure indicates the radiation intensity proportional to the measurement sample 2. Note that tl is an integrated time, which corresponds to the time obtained by dividing the detection length A by the moving speed of the measuring table 1. In addition, the counting rate level other than the shaded area is measured sample 6.
This is the ground count rate from other sources. In this way, radiation measurement is usually accompanied by one-round counting of Parafugu, and the radiation of the measurement sample is measured in addition to this.

By the way, the sensitivity of a device that measures radiation is a measure of the statistically significant difference between the data obtained when measuring a measurement sample and the background count rate. In other words, the value at which this significant difference can be recognized is defined as the sensitivity of the device. Generally speaking, this can be expressed as the following formula.

Sensitivity = sieve;] - (1) In other words, the smaller the pack ground count rate RBG or the larger the integration time T, the better the sensitivity1.Therefore, the sensitivity of the conventional device +1 is as follows. Define time t1 in Figure 2.
It is determined by the area of the pack ground counting rate at the time of measurement and the area of the counting rate when measuring the measurement sample (the shaded area in the figure).

Problems with the Background Art In order to improve the sensitivity of the apparatus configured as described above, it is conceivable to slow down the moving speed of the measurement sample, which is a factor determining the sensitivity, or to lengthen the detection length of the radiation detector. However, slowing down the moving speed of the measurement table is not preferable because radioactive materials are left on the measurement table for a long time. Furthermore, although increasing the detection length allows for a longer integration time, it also increases the detection background count rate, which has the disadvantage that sensitivity cannot be improved as a result.

OBJECTS OF THE INVENTION An object of the present invention is to provide a radiation measurement device that can improve the sensitivity of radiation measurement without slowing down the moving speed of a measurement sample.

Summary of the Invention In order to achieve the above object, the present invention uses a plurality of radiation detectors to sequentially detect the radiation of one radioactivity measurement sample in a radiation measurement device that measures radiation of a moving radioactivity measurement sample. Then, the amount of radiation detected by these detectors according to the detection time is counted and integrated, and the two are added later, and this added value is used as the radiation intensity of the radioactivity measurement sample. It is a ray measuring device.

Embodiment of the Invention An embodiment of the invention will be described with reference to FIGS. 3 and 4. Note that FIG. 3 is a configuration diagram, and FIG. 4 is a diagram showing measurement data.

In FIG. 3, reference numeral 10 denotes a measurement table that moves at a constant speed in the direction of the arrow, and a measurement sample 11 is placed on this measurement table 10. Then, the measurement sample 1 is placed directly above the measurement sample 11 passing through.
Radiation detectors 12 and 13 that output a radial signal according to the amount of radiation a of 1 are arranged in a straight line in the direction of movement of the measurement table 10, with their respective detection surfaces 14 and 15 facing the measurement table 1θ. It is installed in Note that the detection surfaces 14 and 15 have a detection length in the moving direction B of the measuring table 1θ. Waveform shaping circuits 16 and 17 for shaping the waveforms of the output signals are connected to the radiation detectors 12 and 13, respectively. Furthermore, these waveform shaping circuits 16 and 17 include an integration counting circuit 18.
19 are connected to each other. An adding circuit 20 for adding the outputs of these integrating counting circuits 18 and 19 is connected to both integrating counting circuits 18 and 19. The timer circuit 21 that determines the timing of starting and stopping the integration of the integration counting circuits 18 and 19 and the addition timing of the addition circuit 20 is connected to the integration counting circuit 1.
8° 19 and the adder circuit 20.

Next, the operation of the apparatus configured as described above will be explained.

When the measurement sample 11 first enters the range of the detection surface 14 of the radiation detector 12 due to the movement of the measurement table 10, the timer circuit 21 causes the integration counting circuit 18 to perform an integration operation. Therefore, this integration counting circuit 18 integrates the signal outputted from the radiation detector 12 according to the radiation dose of the measurement sample 11 via the waveform shaping circuit 16. This cumulative time is
The time required for the measurement sample 11 to escape from the range of the detection surface 14 corresponds to the time obtained by dividing the detection length B of the detection surface 14 by the moving speed of the measurement table 10. After the above time has elapsed, the output of the integration counting circuit 18 is held in the adding circuit 20, and the timer circuit 2
1 causes the integration counting circuit 18 to stop the integration. Furthermore, when the measurement sample 11 moves and enters the range of the detection surface 15 of the radiation detector 13, the integration counting circuit 19 starts integration by the timer circuit 21 in the same way as above, and after the same integration time as above has passed, the same counting is performed. The output of the circuit 19 is input to the adding circuit 20, and the timer circuit 20 stops the integration.

After the measurement sample 11 passes through the two radiation detectors 12 and 13, the addition circuit 20 adds the counting rates of the integration counting circuits 18 and 19 in response to a timing signal from the timer circuit 21.

Note that the integration timing of the integration counting circuits 18 and 19 of the timer circuit 21 and the addition timing of the addition circuit 20 depend on the moving speed of the measuring table 10, the detection length B of the detection surfaces '14 and J5, and the distance between the two side surfaces 14 and 15. You can easily set it up.

The count rate response curve obtained from each radiation detector 12 and 13 with the above configuration is shown in FIG. 4(a).

It will look like (b). The vertical axis represents the counting rate, and the horizontal axis represents the time T. ) is measured by the radiation detector 12, and (b) is measured by the radiation detector 13.

In addition, the shaded area represents the amount proportional to the radiation intensity measured by both detectors 12 and 13, and time T1 is the amount proportional to the radiation intensity measured by both detectors 12 and 13.
Shows the cumulative time of 8.19.

Here, if the radiation detectors 12, 13, the moving speed of the measurement table 10, and the measurement sample 11 of this embodiment are completely the same as those of the conventional apparatus shown in FIG.
The count rate response curve obtained from 3 is also the same. When compared with the conventional device under the above conditions, Figures 2 and 4 (
a).

As is clear from (b), the amount of data obtained from the measurement sample during measurement (the shaded area in each figure) is twice as much in this example as compared to the conventional one. That is, a statistically significant difference in the above definition of sensitivity is twice as significant, resulting in an improvement in sensitivity.

Now, within the above conditions, the detection length of the detection surface 4 of the radiation detector 3 of the conventional configuration is determined by the radiation detection section 12.13 of this embodiment.
If the length corresponding to the sum of the detection lengths of the detection surfaces 14 and 15 is multiplied by 92, the time for the measurement sample to pass through the detection surfaces will be doubled, and the data obtained will also be doubled. However, since the detection length is doubled, the surface of the pack ground that receives radiation is also doubled, and as a result, the pack ground counting rate also doubles. Therefore, the above-mentioned statistically significant difference is unchanged from the original detection length and does not lead to any improvement in sensitivity. This can be expressed in the form of cutting allowance (1) as follows.

Sensitivity in this example is closed by 2.
) However, k is a proportionality coefficient, RBG is a background counting rate, and T is each integrated time when the radiation detectors 3, 12, and 13 are the same. In addition, the coefficient 2 represents the number of radiation detectors in equation (2), and the coefficient 2 represents the number of radiation detectors in equation (3).
) shows the multiple of the detection length of the detector in equation (3) with respect to the detection length per one radiation detector in equation (3).

As mentioned above, even if the detection length is lengthened, the sensitivity cannot be improved, but by using two or 10- or more radiation detectors as in the embodiment of the present invention, the moving speed of the measuring table can be increased. Sensitivity can be improved without slowing down. Note that when a plurality of sensors are used, the sensitivity is expressed by replacing the coefficient 2 in equation (2) with the number of devices used.

Further, the present invention does not only use one set of radiation detectors as in the above embodiment, but can expand the effect by arranging a plurality of sets as shown in FIG. 5, for example.

Note that the figure only shows the arrangement of the detection surface of the radiation detector. In the figure, reference numerals 30'-1 and 30'-2 represent a pair of radiation detectors that are integrated and counted by the integrating and counting circuit system A, and have detection surfaces 3θ-1 and 30-2 inside them. Similarly, the integration counting circuit system B has a detection surface 31-1.31.
-2 radiation detectors, 91' -1, 3
1'-2 is connected, and the integration counting circuit system C has a set of radiation 1 and 1° detectors 32'-1 and J2'-2 each having a detection surface 32-1 and 32-2. is connected. Then, move the measurement sample in the direction of the arrow.

Then, in the movement direction, one set of radiation detectors in the circuit system A is used to form an area (2), one set of radiation detectors in the circuit system B is used to form an area (2), and one set of radiation detectors in the circuit system C is used to form an area A measurement area is formed.

If you move the measurement sample with the above configuration, the measurement area■@
If the measurement sample moves to one of the areas O, the radiation detector and integration counting circuit system of that area will be transferred to the third area.
Radiation is measured in the same way as the configuration device shown in the figure. In addition, the count rate response curves measured in each region ■@O are shown in Figure 6 (A) (
B) It will look like (C). The vertical axis shows the counting rate, and the horizontal axis shows time T, and (a), (b), and (c) are the areas ■0θ, respectively.
The shaded area indicates data proportional to radiation intensity. Further, T2 is an integrated time. The shaded portions are finally added in each of the circuit systems A, B, and C.

As described above, in the apparatus configured as shown in FIG. 5, the width of the radiation detection surface is increased (sum of valley widths of area ■@○). Therefore, it is possible to prevent radiation from not being detected at the edge of the detector (which occurs due to the fact that the detection surface of commonly used radiation detectors is small compared to the external size), and to ensure even measurement. It's a passable score.

Furthermore, the present invention can also be configured as shown in FIG. 6, in which the two integration counting circuits shown in FIG. 3 are combined into one (by means of a switching circuit). Components that are the same as those in FIG. 73 have the same numbers, and their explanation will be omitted. Waveform shaping circuit 16.17
A switching circuit 40 for switching the signals of both circuits 16 and 17 is connected to the output side of , and an integration counting circuit 41 for integrating and counting the signals selected by the circuit 40 is connected to this switching circuit 40. Furthermore, an adder circuit 42 is connected to this integration counting circuit 41. A timer circuit 43 that determines the operation timing of each of the switching circuit 40, the integration counting circuit 41, and the addition circuit 42 is connected to the three circuits 4θ, 41.42.

In the apparatus configured as described above, when the measurement sample 1 passes the detection surface 14, the timer circuit 43 switches the switching circuit 40 to the waveform shaping circuit 16 side.

13- The signals thus detected from the detection surface 14 are integrated and counted by the integration counting circuit 41. Then, it is held in the adder circuit 42. Next, when the measurement sample 1 passes the detection surface 15, the switching circuit 4θ is switched to the waveform shaping circuit 17 side by the timer circuit 43, and the detected 1+W is integrated and counted by the integration counter circuit 41. Furthermore, it is added to the accumulated count value held in the adder circuit 42.

As described above, in the configuration shown in FIG. 7, the same effect as in the configuration shown in FIG. 3 can be obtained with only one integration counting circuit.

In other words, the present invention can be modified in various ways without departing from the gist thereof.◎ Effects of the Invention According to the present invention, by using a plurality of radiation detectors, compared to using one identical radiation detector, Sensitivity can be improved in proportion to the square root of the number used. Therefore, there is no need to slow down the moving speed of the measurement sample, and there is no need to leave radioactive substances for a long time.Also, objects with low radiation doses can be easily measured, and furthermore, the radiation detector can be re-arranged. 4) It is possible to provide a radiation measurement device that enables high measurement.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of a conventional radiation measurement device, and Figure 2 is a 7
A count rate response curve diagram of the device having the configuration shown in the figure, FIG. 3 is a configuration diagram of one embodiment of the radiation measuring device according to the present invention, and FIG.
Figure 5 is a block diagram of the first modified example of the radiation measuring device according to the present invention; Figure 6 is a diagram of the count rate response curve of the apparatus configured as shown in Figure 5. , FIG. 7 is a configuration diagram of a second modification of the radiation measuring device according to the present invention. 12.13...Radiation detector, 18.19...Integration counting circuit, 20.42...Addition circuit, 21°43...
・Timer circuit. Applicant's agent Patent attorney Takehiko Suzue 15- Figure 2

Claims (2)

[Claims] (1) A number of detectors that sequentially detect an amount of radiation according to a predetermined detection time from one moving radioactivity measurement sample and 8 detectors each detecting the amount of radiation detected by each detector at a predetermined timing.
A radiation measuring device 0 characterized in that it is equipped with an integrating/subtracting means for adding up the integrated values of each integrated value, and the addition output of the adding means is used as the radiation intensity of the radioactivity measurement sample. (2) Multiple detection systems with multiple detectors that sequentially detect an amount of radiation according to a predetermined detection time from one moving radioactivity measurement sample are divided in a direction perpendicular to the moving direction of the radioactivity measurement sample. A means arranged for each measurement area, and a plurality of integrating/adding means for respectively integrating the detection amount of each detector of the plurality of detection systems arranged by this means at a predetermined timing and adding the respective integrated values. A radiation measuring device, characterized in that the summation output of each of the integrating/adding means is taken as the radiation intensity of the radioactivity measurement sample.