JP3522799B2 - Radioactivity detection system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radioactivity detection system for detecting the radioactivity of an object, and particularly by associating the lower limit of detection radioactivity with the time required for detection, the shortest time required. The present invention relates to a radioactivity detection system that can realize the above and accelerate the detection of radioactivity.

[0002]

2. Description of the Related Art Generally, in the field of detecting the radioactivity of a subject, the radioactivity detection is performed by sampling the radioactivity of the subject for a predetermined sampling time and then counting the sampled radioactivity for a predetermined counting time. The system is widely used.

FIG. 7 is a block diagram showing the construction of this type of radioactivity detection system. This radioactivity detection system
When the start switch 1 is turned on, the pump 3 operates for the sampling time set in the sampling time setting device 2.

The pump 3 sucks air through the air filter 4, the inspection container 6 in which the vitrified body 5 as the subject is housed, and the radioactivity adsorption filter 7, and discharges the air to the duct 8.

Here, the radioactivity leaking from the vitrified body 5 is accumulated on the radioactivity adsorption filter 7 along with the sucked air during the sampling time. The starting switch 1, the sampling time setting device 2, the pump 3, and the radioactivity adsorption filter 7 constitute a sampling device 9.

After the sampling is completed, the radioactivity adsorption filter 7 is carried to the analyzer 10. In the analyzer 10, the radioactivity adsorption filter 7 is housed in the shielding container 12 having the radioactivity detector 11. The radioactivity detector 11 counts the radioactivity of the radioactivity adsorption filter 7 and sends the count output signal to the calculator 14 in the data processing device 13. Calculator 14
After the parameter setting by the parameter setting device 15 and the counting time setting by the counting time setting device 16 are finished, the counting output signal is converted into the radioactivity (Bq) and the converted data is sent to the display device 17. The display 17 displays this converted data as the analysis result.

The sampling time in the sampling device 9 and the counting time in the analysis device 10 are individually set for the convenience of operation of each device 9, 10.

[0008]

However, in the radioactivity detection system as described above, the sampling time and the counting time are individually set, so that the total time required for summing these times can be minimized. However, there is a problem that measurement is wasted.

Further, this causes a problem in that a delay occurs in the entire process of the vitrified body inspection facility. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a radioactivity detection system that can minimize the time required for radioactivity detection and improve the radioactivity detection speed.

[0010]

According to a first aspect of the present invention, the radioactivity of a subject is sampled for a sampling time (t1) set in a first timer, and the sampled radioactivity is sampled in a second time. by only analyzing device detects counting time set in the timer (t2), the amount
Lower limit of activity (AL), sensitivity coefficient (K) of analyzer
Sampling efficiency (ε), glass solid as the subject
Based on the number (N) of the reduction body, the cross detection limit leakage amount of radioactivity represented by the following formula [1] (CL) met radioactive detection system for measuring the radioactivity of the subject, the sampling time ( t1), the counting time (t2) and the detection limit leakage amount of radioactivity (following calculation equation showing the relationship CL) [2] is stored in advance, the detection limit leakage radioactivity
When the measurement condition data (K, ε, N) defining (CL) is input, the sampling time is calculated based on the measurement condition data (K, ε, N) and the arithmetic expression [2].
(T1) and the sampling time to the sum to minimize the counting time (t2) (t1 _MIN) and calculate the counting time (t2 _MIN), the calculated sampling time (t1 _MIN) and counting time ( t2 _MIN ) is a radioactivity detection system including minimum time setting means for setting the first and second timers. [1] CL = 60 · AL / (ε · N · t1) [Bq / book · time] However, AL = K / (t2) ^1/2 [Bq] [2] t1 = 60 · K / {CL · ε ・ N ・ (t2) ^1/2 } [Time]

In the invention according to claim 2, the radioactivity of the subject is sampled for the required time (T) set in the first timer, and the sampled radioactivity is sent to the second timer. When the analyzer detects for the set required time (T), the detection lower limit radioactivity (AL) of the analyzer, the sensitivity coefficient (K), the sampling efficiency (ε), the vitrified body as the analyte A radioactivity detection system for measuring the radioactivity of the subject exceeding the detection lower limit leak radioactivity (CL) shown in the following formula [1] based on the number (N) of
And the following arithmetic expression [2] showing the relationship between the detection lower limit leak radioactivity (CL) is stored in advance, and the measurement condition data (K, ε,
N) is input, the measurement condition data (K, ε,
Based on N) and the mathematical expression [2], wherein the calculating the required time (T) is such that the shortest required time (T _MIN), the required time (T _MIN) the first and in which the calculated It is a radioactivity detection system provided with a shortest time setting means for setting a second timer.

Further, in the invention corresponding to claim 3, the filter paper is continuously delivered by the driving unit, a gas containing radioactivity is passed through the filter paper to attach the radioactivity to the filter paper, and the attachment. When the analyzer detects the radioactivity thus caused for the required time (T) set in the timer,
Lower limit of detection of the analyzer Based on the activity level (AL), the sensitivity coefficient (K), the sampling efficiency (ε), and the number (N) of vitrified solids as the analyte, the lower limit of detection shown in the following formula [1] A radioactivity detection system for measuring the radioactivity of the gas which exceeds the leak radioactivity (CL), wherein the required time (T) and the detection lower limit leak radioactivity (C)
L) is stored in advance and the measurement condition data (K, ε, N) that defines the detection lower limit leak radioactivity (CL) is input, the measurement condition data ( K, ε, N) and the calculation formula [2], the required time (T _MIN ) is calculated so as to _{minimize the} required time (T), and the calculated required time (T _MIN )
Is stored in the required time setting means for setting the timer, and the reference value of the measured radioactivity, the reference value and the measured radioactivity are compared, the radioactivity is the reference by the comparison result. When the value exceeds the value, a sending speed control command is sent to the drive unit so as to increase the sending speed of the filter paper, and when the radioactivity does not exceed the reference value according to the comparison result, the sending speed of the filter paper is changed. It is a radioactivity detection system provided with a sending speed control means for sending a sending speed control command to the drive unit so as to slow it down.

[0013]

Therefore, according to the invention corresponding to claim 1, the sampling time (t
1) , counting time (t2) and detection lower limit leak activity
The measurement condition data is provided with a minimum time setting means in which an arithmetic expression indicating the relationship of (CL) is stored in advance, and the minimum time setting means defines the detection lower limit leak radioactivity (CL).
When (K, ε, N) is input, measurement condition data
Based on (K, ε, N) and the arithmetic expression, the sampling time (t1 _MIN ) and the counting time (t ) are set so as to minimize the sum of the sampling time (t1) and the counting time (t2).
2 _MIN ) and the calculated sampling time (t
Since 1 _MIN ) and counting time (t2 _MIN ) are set in the first and second timers, the time required for detecting radioactivity can be minimized and the detection speed of radioactivity can be improved.

Further, the invention according to claim 2 is provided with a shortest time setting means in which an arithmetic expression showing the relationship between the required time (T) and the lower limit of detection leak activity (CL) is stored in advance.
Moreover, this minimum time setting means is
When the measurement condition data (K, ε, N) defining (CL) is input, the required time (T) should be minimized based on the measurement condition data (K, ε, N) and the calculation formula. Since the required time (T _MIN ) is calculated and the calculated required time (T _MIN ) is set in the first and second timers, sampling and radioactivity detection can be performed at the same time in addition to the effect of claim 1. .

Further, the invention according to claim 3 is provided with a required time setting means in which an arithmetic expression showing a relation between the required time (T) and the detected lower limit leak radioactivity (CL) is previously stored, and the required time setting means is provided. However, the lower limit of detection leak activity (C
When the measurement condition data (K, ε, N ) that specifies L) is input, it is necessary to minimize the required time (T) based on the measurement condition data (K, ε, N) and the calculation formula. time
(T _MIN ) is calculated, the calculated required time (T _MIN ) is set in a timer, and the delivery speed control means stores the reference value of the measured radioactivity, and the reference value and the measured radioactivity are stored. When the radioactivity amount exceeds the reference value based on this comparison result, a delivery speed control command is sent to the drive unit to increase the delivery speed of the filter paper, and when the radioactivity amount does not exceed the reference value based on the comparison result. Since the sending speed control command is sent to the drive unit so as to slow down the sending speed of the filter paper, it is possible to detect the radioactivity in the shortest required time corresponding to the fluctuation of the background.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. Before that, the detection lower limit leak radioactivity CL, sampling time t1 and counting time t required for radioactivity detection will be described.
2 will be described with reference to FIG.

Lower limit of detection leak activity of this system CL
(Bq / line · time) has the property of being inversely proportional to the sampling time t1 due to the integration effect of the radioactive adsorption filter and also proportional to the lower limit of detection activity AL (Bq) of the analyzer.

Here, the lower limit of detection activity AL (Bq) is inversely proportional to the 1/2 power of the counting time t2 as shown in the following equation (1). AL (Bq) = K / (t2) ^1/2 (1) where K is a sensitivity coefficient determined by the background count rate and the like.

Further, the lower limit of detection leak radioactivity CL is proportional to the lower limit of detection radioactivity AL and is inversely proportional to the sampling time t1 as shown in the following equation (2). CL = 60 · AL / (ε · N · t1) (2) where ε is the sampling efficiency and N is the number of vitrified bodies.

At this time, the total required time T required to detect the radioactivity is the sum of the sampling time t1 and the counting time t2 as shown in the following equation (3). T = t1 + t2 (3) Further, from these equations (1) to (3), the following (4)
The formula and the formula (5) are derived.

T1 = 60 · K / {CL · ε · N (t2) ^1/2 } (4) T = 60 · K / {CL · ε · N (t2) ^1/2 } + t2 (5) Here, by differentiating the equation (5) and setting it to zero, the counting time t2 _MIN that minimizes the total required time T can be calculated as shown in the following equation (6). Further, by substituting the counting time t2 into the equation (4), the sampling time t1 _MIN that minimizes the total required time T can be calculated as shown in the following equation (7). (DT / dt ² ) = 1-60 · K · t2 ^−3/2 / {2 · CL · ε · N} = 0 t2 _MIN = {60 · K / (2 · CL · ε · N)} ^{2 / 3} ... (6) t1 _MIN = 2 { _60.K / (2.CL .epsilon.N)} ^2/3 (7) In addition, t1 _MIN and t2 _MIN are expressed by the equations (6) and (7).
As shown in the equation, there is a relation of t1 _MIN = 2 · t2 _MIN .

Subsequently, the sampling time t1 _MIN and the counting time t2 _MIN that minimize the total required time.
The system of the present embodiment in which is applied to the detection of radioactivity will be described.

FIG. 1 is a block diagram showing the structure of a radioactivity detecting system according to the first embodiment of the present invention. The same parts as those in FIG. 7 are designated by the same reference numerals and their detailed description will be omitted.
Here, only different parts will be described.

That is, the system of this embodiment minimizes the total required time T, which is the sum of the sampling time t1 and the counting time t2. Specifically, specifically, the measurement parameter set in the parameter setting device 21 is set. Sampling time t1 that minimizes the total required time T by using
_{It is configured to include} a time calculator (minimum time setting means) 22 for calculating _MIN and counting time t2 _MIN .

Here, the parameter setting device 21 is used to set measurement parameters (measurement condition data) indicating the sensitivity constant K, the sampling efficiency ε, and the number N of vitrified solids, and these measurement parameters are set to the time calculator. 22 and the calculator 13 are provided. In addition, the parameter setter 21 determines the sensitivity coefficient K and the detection lower limit leak radioactivity CL by sampling time t1 ', counting time t2' and detection lower limit radioactivity AL 'which are tentative measurement conditions.
When is set, these temporary measurement conditions are
It has a function to give to 2.

The time calculator 22 stores the above-mentioned equations (1) to (7) in advance, and the parameter setter 21 measures the sensitivity parameter K, the sampling efficiency ε and the measured parameter indicating the number N of vitrified solids. Sampling time t that minimizes the total required time T by substituting these measurement parameters and temporary measurement conditions into the arithmetic expression
1 _MIN and counting time t2 _MIN are calculated, and this sampling time t1 _MIN is set in the sampling time setting device (first timer) 2, and counting time t2 _MIN is set in the counting time setting device (second timer) 16 It has a function to set.

Next, the operation of such a radioactivity detection system will be described. Now, the parameter setting device, when the measurement parameters ε, N and temporary measurement conditions t1 ′, t2 ′, AL ′ are set by the operator's operation as shown below, these ε, N, t1 ′, t2 are set. ′, AL ′ is a time calculator 22
Give to.

Measurement parameters: ε = 0.1, N = 3
(Book). Temporary measurement conditions ... t1 '= 300 (min), t2' = 120
(Min), AL '= 1.1 (Bq).

The time calculator 22 substitutes the given AL 'and t2' into the equation (1) to calculate the sensitivity coefficient K. That is, K = 12 is obtained from 1.1 = K / (120) ^1/2 .

Similarly, the time calculator 22 substitutes the given ε, N and t1 'into the equation (2) to calculate the detected lower limit leak activity CL as shown below. CL = 1.1 / (0.1 × 3 × 300/60) = 0.7
4 (Bq / line · time) Subsequently, the time calculator 22 substitutes these sensitivity coefficients K = 12 and CL = 0.74 into the equation (4) as shown below.

(T1 / 60) = 12 / {0.74 × 0.
1 × 3 × (t2) ^1/2 } ∴t1 × (t2) ^1/2 = 3244 As described above, since there is a relation of t1 _MIN = 2 · t2 _MIN , the time calculator 22 is T = Calculate t1 _MIN and t2 _MIN that minimize t1 + t2.

That is, 2 · (t2 _MIN ) ^1/2 = 324
From step 4, t2 _MIN = 138 (minutes) is calculated. Also, t1
_MIN = 2 · t2 _MIN = 276 (minutes) is calculated. The total required time T _{MIN at} this time is 414 (minutes).

Further, the time calculator 22 sets the calculated sampling time t1 _MIN in the sampling time setter 2 and sets the counting time t2 _MIN in the counting time setter 16. Hereinafter, as described above, the sampling device operates the pump 3 for the set sampling time t1 _MIN to adsorb the radioactivity of the vitrified body 5 to the radioactivity adsorption filter 7. In the analyzer, the radioactivity of the radioactivity adsorption filter 7 is detected for the counting time t2 _MIN , the arithmetic unit 14 converts it into the amount of radioactivity (Bq), and the converted data is displayed on the display unit 17 as the analysis result.

As described above, the present system can detect the radioactivity of the vitrified body 5 in the shortest total required time T _MIN . As described above, according to the first embodiment, when the time calculator 22 receives the measurement parameter that defines the detection lower limit leak radioactivity CL, the sampling is performed based on the measurement parameter and the previously stored calculation formula. The sampling time t1 _MIN and the counting time t2 _MIN are calculated so as to minimize the sum of the time t1 and the counting time t2, and the calculated sampling time t1 _MIN is set in the sampling time setter 2 and the counting time t2 _MIN.
Is set in the counting time setter 16, the time required for detecting the radioactivity can be minimized and the radioactivity detection speed can be improved.

Next, a radioactivity detection system according to the second embodiment of the present invention will be described. FIG. 3 is a block diagram showing the configuration of this radioactivity detection system. The same parts as those in FIG. 1 are designated by the same reference numerals, detailed description thereof will be omitted, and only different parts will be described here.

That is, in the system of this embodiment, the radioactive adsorption filter 7 for sampling and the detector are integrated,
It is an online analysis type that detects the accumulated radioactivity at the same time as sampling the radioactivity.
In contrast to the system shown in FIG. 2, the shield container 12 having the radioactivity detector 11 can be sucked by the pump 3 and has the radioactivity adsorption filter 23 and the radioactivity detector 24.
Instead of this, the shielding container 25 is arranged in front of the pump 3.

Here, the radioactivity adsorption filter 23 is shown in FIG.
As shown in, since the radioactivity from the vitrified body 5 is gradually accumulated, the radioactivity contributes so that the denominator of the equation (2) becomes 1/2.

Since simultaneous sampling and simultaneous measurement are performed, the relationship of t1 = t2 = T is established. Based on this relationship, the total required time T _MIN is expressed by the following expression (8) based on the expression (4).

T _MIN = t1 _MIN = t2 _MIN = { _60K / ((1/2) CL ・ εN)} ^2/3 (8) This equation (8) is used as the shortest time setting means. Is previously stored in the time calculator 26.

As described above, when the measurement parameters ε, N and the temporary measurement conditions t1 ', t2', AL 'are set by the parameter setting unit 15, the time calculator 26 determines the sensitivity coefficient K based on these parameters. And detection lower limit leak activity CL
To calculate. In addition, T _MIN obtained by the equation (8) based on the sensitivity coefficient K and the detection lower limit leak radioactivity CL
Are set in the sampling setting device 2 and the counting time setting device 16.

Hereinafter, in the same manner as described above, the system of this embodiment is
The pump 3 is operated for the set required time T _MIN to adsorb the radioactivity of the vitrified body 5 to the radioactivity adsorption filter 23, and at the same time, the radioactivity of the radioactivity adsorption filter 23 is detected for the required time T _MIN and calculated. Vessel 14 is the amount of radioactivity (Bq)
And the converted data is displayed on the display unit 17 as the analysis result.

As described above, the present system can detect the radioactivity of the vitrified body 5 in the shortest total required time T _MIN . As described above, according to the second embodiment, when the time calculator 26 receives the measurement parameter that defines the detection lower limit leak activity CL, the required time T is minimized based on the measurement parameter and the calculation formula. The required time T _MIN is calculated as follows, and the calculated required time T is
_MIN for sampling time setting device 2 and counting time setting device 1
Since it is set to 6, the same effect as that of the first embodiment can be obtained even in the online analysis type detection system different from that of the first embodiment.

Further, according to the second embodiment, since the measurement is carried out simultaneously with the sampling of the radioactivity, the radioactivity can be detected in a shorter time than the first embodiment. next,
A radioactivity detection system according to a third embodiment of the present invention will be described with reference to the drawings.

FIG. 5 is a block diagram showing the structure of this radioactivity detection system. This radiation detection system is applied to an intermittent feed type dust monitor, has a ventilation passage 31 through which a gas containing radioactivity flows downward from above, and a filter paper 32 that runs a filter paper 32 across the ventilation passage 31.
It is equipped with a traveling mechanism.

In this traveling mechanism, a winding roller 34, which is intermittently driven to rotate by a motor 33, winds a filter paper 32 which is intermittently unwound from an unwinding roller 35 and travels across an air passage 31. Is.

The filter paper 32 is unwound from the unwinding roller 35 and serves to scavenge the radioactivity in the gas flowing through the ventilation passage 31 when traversing the ventilation passage 31, and this radioactivity is placed to detect the radioactivity. It passes through the lower part of the container 36 intermittently and is wound up by the winding roller 34.

The radioactivity detector 36 detects the radioactivity placed on the lower filter paper 32 and gives a count output signal to the calculator 37. The calculator 37 converts the count output signal given from the radioactivity detector 32 into a radioactivity amount (Bq),
The conversion result is given to the time calculator 38 and the display 39.

The time calculator 38 stores the formula (8) and the reference value of the amount of radioactivity, calculates the shortest total required time T _MIN as described above, and based on the calculation result, the motor 33.
It has a function to turn on and off. Further, the time calculator 38 has a function of comparing the conversion result of the radioactivity amount (Bq) received from the calculator 37 with a reference value and controlling the motor 33 on / off based on the comparison result. The off time of the motor 33 is the total required time T _MIN .

Upon receiving the conversion result from the calculator 37, the display 39 displays the amount of radioactivity shown in the conversion result. Next, the operation of such a radioactivity detection system will be described.

The time calculator 38 calculates the shortest total required time T _MIN as described above, and calculates the calculated required time T _MIN.
The motor 33 is off controlled by _MIN . When the required time T _MIN elapses, the time calculator 38 turns on the motor 33 to move the filter paper 32, which has absorbed the radioactivity in the ventilation passage 31, to the lower side of the radioactivity detector 36, and the time required again. Time T
_The motor 33 is off controlled by _MIN .

The radioactivity detector 36 detects the radioactivity on the filter paper 32 while the motor 33 is off, and sends a count output signal to the calculator 37. The calculator 37 converts this count output signal into the amount of radioactivity (Bq), and the conversion result is displayed on the display unit 3.
9 and the time calculator 38. The display 39 displays the amount of radioactivity shown in this conversion result.

The time calculator 38 compares the amount of radioactivity shown in the conversion result with a prestored reference value of the amount of radioactivity. As a result, when the detected amount of radioactivity is higher than the reference value, the motor 33 Of the motor 33 by moving the filter paper 32 to measure the radioactivity on the next filter paper 32 and changing the total required time T _MIN to a short value by a predetermined unit time during the measurement. Reduce the off time.

On the other hand, as a result of comparing the activity amount shown in the conversion result with the previously stored reference value of the activity amount, if the detected activity amount is lower than the reference value, the time calculator 3
In No. 8, the off control of the motor 33 is continued for a predetermined unit time to measure the radioactivity on the filter paper 32, and at the time of measurement, the total required time T _MIN is changed to a long value by a predetermined unit time. The off time of the motor 33 is extended.

As a result, even if the background BG (cps) at the installation location of the system fluctuates and the total required time T _MIN deviates, the total required time T _MIN is changed in response to the background fluctuation. Therefore, the radioactivity can be detected in the optimum total required time T _MIN . The change of the total required time T _MIN corresponds to the correction of the sensitivity coefficient K contained in the numerator of the equation (8) and proportional to (BG) ^1/2 .

Hereinafter, the system of this embodiment repeats the above-mentioned processing to intermittently detect the radioactivity in the gas. As described above, according to the third embodiment, the time calculator 38
Since the shortest total required time T _MIN is set based on the equation (8) to control the motor 33 to turn on and off, and the total required time T _MIN is changed based on the detected radioactivity, the second In addition to the effect of the embodiment described above, the radioactivity can be detected in the shortest total required time T _MIN corresponding to the fluctuation of the background.

Next explained is a radioactivity detection system according to the fourth embodiment of the present invention. FIG. 6 is a block diagram showing the configuration of this radioactivity detection system. The same parts as those in FIG. 5 are designated by the same reference numerals, detailed description thereof will be omitted, and only different parts will be described here.

That is, the system of the present embodiment is a continuous filter paper feed type dust monitor for continuously detecting the radioactivity adhering to a filter paper while continuously sending the filter paper across a ventilation path through which a gas containing radioactivity flows. This is applied to the system shown in FIG. 5, and instead of the ventilation passage 31 for flowing the gas from the upper side to the lower side, the gas containing radioactivity is passed downward from the lower side via the filter paper 32 again. It has a ventilation passage 41 which flows to reach the above, and is arranged above the filter paper 32 facing the ventilation passage 41.

Since the continuous filter paper feed system is used, the time calculator 42 as the required time setting means and the delivery speed control means controls the motor 33 not by the on / off control but by the rotation speed control.

That is, the time calculator 42 stores the formula (8) and the reference value of the radioactivity, calculates the shortest total required time T _MIN as described above, and based on the calculation result, the rotation speed of the motor 33. It has a function to control. Further, the time calculator 42 compares the conversion result of the radioactivity amount (Bq) received from the calculator 37 with the reference value, and sends a rotation speed control command to the motor 33 based on the comparison result, so that this motor It has a function of controlling the rotation speed of 33.

Next, the operation of the system of this embodiment will be described. The radioactivity detector 36 detects radioactivity on the moving filter paper 32 and sends a count output signal to the calculator 37.

The calculator 37 converts the count output signal into the amount of radioactivity (Bq) and sends the conversion result to the display 39 and the time calculator 42. The display 39 displays the amount of radioactivity shown in this conversion result.

The time calculator 42 compares the amount of radioactivity shown in this conversion result with a prestored reference value of the amount of radioactivity. As a result, when the detected amount of radioactivity is higher than the reference value, the motor 33 Filter paper 3 while controlling the rotation speed of
2 is moved to measure the radioactivity on the filter paper 32, and at the time of measurement, the total required time T _MIN is changed to a value shorter by a predetermined unit time.

On the other hand, as a result of comparing the activity amount shown in the conversion result with the previously stored reference value of the activity amount, when the detected activity amount is lower than the reference value, the time calculator 4
In No. 2, the rotation speed of the motor 33 is reduced by a predetermined unit speed to measure the radioactivity on the filter paper 32, and at the time of measurement, the total required time T _MIN is changed to a long value by a predetermined unit time. .

In the same manner as in the third embodiment, the above processing is repeated to continuously detect the radioactivity in the gas. According to the fourth embodiment, the time calculator 42 is
Since the shortest total required time T _MIN is set based on the equation (8) to control the rotation speed of the motor 33 and the total required time T _MIN is changed based on the detected radioactivity, In addition to the effects of the third embodiment,
Radioactivity can be detected continuously. In addition, the present invention can be modified in various ways without departing from the scope of the invention.

[0065]

As described above, according to the first aspect of the present invention, the arithmetic expression indicating the relationship among the sampling time (t1) , the counting time (t2) and the lower limit of detection leak activity (CL) is stored in advance. When the minimum time setting means is provided and the measurement condition data (K, ε, N) that defines the detection lower limit leak radioactivity (CL ) is input, the measurement condition data (K, ε, based on N) and arithmetic expressions, sampling time (t1) and counting time (t2) the sum sampling time so as to minimize the (t1 _MIN) and counting time (t2 _MIN) is calculated, the calculated sampling time ( since t1 _MIN) and a total of several hours (t2 _MIN) and to set the first and second timers, to minimize the time required for radioactivity detection, radioactive detection system capable of improving the detection rate of radioactivity It can provide.

According to the invention of claim 2, the required time is
(T) and a detection lower limit leak radioactivity (CL) are stored in advance with a minimum time setting means in which an arithmetic expression is stored.
When the measurement condition data (K, ε, N) defining (CL) is input, the required time (T) should be minimized based on the measurement condition data (K, ε, N) and the calculation formula. Since the required time (T _MIN ) is calculated and the calculated required time (T _MIN ) is set in the first and second timers, in addition to the effect of claim 1, sampling and radioactivity detection can be performed simultaneously. A radioactivity detection system can be provided.

Further, according to the invention corresponding to claim 3, the required time (T) and the detection lower limit leak radioactivity (C
L) is provided with a required time setting means in which an arithmetic expression is stored in advance, and the required time setting means defines measurement condition data (K, ε, N) that defines the detection lower limit leak activity (CL ).
When is input, the required time (T _MIN ) is calculated so as to minimize the required time (T) based on the measurement condition data (K, ε, N) and the arithmetic expression, and the calculated required time
(T _MIN ) is set in the timer, the delivery speed control means stores the reference value of the measured radioactivity, compares the reference value with the measured radioactivity, and the radioactivity amount is used as the reference based on the comparison result. When the value exceeds the value, a sending speed control command is sent to the drive unit to increase the sending speed of the filter paper, and when the radioactivity amount does not exceed the reference value according to the comparison result, the driving unit slows the sending speed of the filter paper. Since the transmission speed control command is transmitted to the radioactivity detection system, it is possible to provide a radioactivity detection system capable of detecting the radioactivity in the shortest required time corresponding to the fluctuation of the background.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a radioactivity detection system according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining a time required for detecting radioactivity in the example.

FIG. 3 is a block diagram showing the configuration of a radioactivity detection system according to a second embodiment of the present invention.

FIG. 4 is a diagram for explaining a time required for detecting radioactivity in the example.

FIG. 5 is a block diagram showing a configuration of a radioactivity detection system according to a third embodiment of the present invention.

FIG. 6 is a block diagram showing the configuration of a radioactivity detection system according to a fourth embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a conventional radioactivity detection system.

[Explanation of symbols]

1 ... Start-up switch, 2 ... Sampling time setting device, 3 ...
Pump, 4 ... Air filter, 5 ... Vitrified body, 6 ... Inspection container, 7, 23 ... Radioactive adsorption filter, 8 ... Duct,
11, 24, 36 ... Radioactivity detector, 12, 25 ... Shielding container, 14, 37 ... Computing device, 16 ... Counting time setting device, 1
7, 39 ... Display device, 21 ... Parameter setting device, 22, 2
6, 38, 42 ... Time calculator, 31, 41 ... Ventilation path, 3
2 ... Filter paper, 34 ... Winding roller, 35 ... Unwinding roller.

Claims (3)

(57) [Claims] 1. A radioactivity of a subject is sampled for a sampling time (t1) set in a first timer, and the sampled radioactivity is analyzed for a counting time (t2) set in a second timer. Based on the detection lower limit radioactivity (AL), the sensitivity coefficient (K), the sampling efficiency (ε), and the number (N) of the vitrified substances as the analyte, which are detected by the analyzer, [1]
A radioactivity detection system for measuring the radioactivity of the subject exceeding the detection lower limit leak radioactivity (CL) shown in (1), wherein the sampling time (t1) and the counting time (t2)
And the following arithmetic expression [2] showing the relationship between the detection lower limit leak radioactivity (CL) is stored in advance, and the measurement condition data (K, ε,
N) is input, the measurement condition data (K, ε,
N) and the calculation formula [2], the sampling time (t1 _MIN ) and the counting time (t2 _MIN ) are set so as to minimize the sum of the sampling time (t1) and the counting time (t2). A radioactivity detection system comprising a minimum time setting means for calculating and setting the calculated sampling time (t1 _MIN ) and counting time (t2 _MIN ) in the first and second timers. 2. The radioactivity of the subject is sampled for the required time (T) set in a first timer, and the sampled radioactivity is the required time (T) set in a second timer. Only by the analyzer detecting
Lower limit of detection of the analyzer Based on the activity level (AL), the sensitivity coefficient (K), the sampling efficiency (ε), and the number (N) of vitrified solids as the analyte, the lower limit of detection shown in the following formula [1] It is a radioactivity detection system which measures the radioactivity amount of the said subject which exceeded the leak radioactivity amount (CL), Comprising: The following calculation formula which shows the relationship between said required time (T) and said detection lower limit leak radioactivity amount (CL) [ 2] is stored in advance, and when the measurement condition data (K, ε, N) defining the detection lower limit leak radioactivity (CL) is input, the measurement condition data (K, ε, N) and the arithmetic expression Based on [2], the required time (T _MIN ) is calculated so as to _{minimize the} required time (T), and the calculated required time (T
A radioactivity detection system comprising a shortest time setting means for setting _MIN ) to the first and second timers. 3. A filter paper is continuously delivered by a drive unit, a gas containing radioactivity is passed through the filter paper to attach the radioactivity to the filter paper, and the attached radioactivity is set in a timer. When the analyzer detects only the required time (T), the lower detection limit activity (AL), sensitivity coefficient (K), sampling efficiency (ε) of the analyzer,
Based on the number (N) of vitrified substances as the test object, the lower limit of detection leak activity (C) shown in the following formula [1]
In the radioactivity detection system for measuring the radioactivity of the gas exceeding L), the following arithmetic expression [2] indicating the relationship between the required time (T) and the detection lower limit leak radioactivity (CL) is stored in advance. Then, when the measurement condition data (K, ε, N) that defines the detection lower limit leak activity (CL) is input, based on the measurement condition data (K, ε, N) and the arithmetic expression [2]. Te, wherein calculating the required time (T) is such that the shortest required time (T _MIN), and the required time setting means for setting the calculated required time (T _MIN) to said timer and said measured The reference value of the amount of radioactivity is stored, the reference value and the measured amount of radioactivity are compared, and when the amount of radioactivity exceeds the reference value by this comparison result, the delivery speed of the filter paper is increased. Sends a sending speed control command to the drive unit And a sending speed control means for sending a sending speed control command to the driving unit so as to slow down the sending speed of the filter paper when the radioactivity amount does not exceed the reference value according to the comparison result. Radioactivity detection system.