JP2014106103A - Radioactivity screening device and radioactivity screening method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform screening of radioactivity of a sample safely and without wasting time.SOLUTION: A radioactivity screening device 1 comprises: a mass weighing unit 3 weighing mass of a container holding a sample; a radiation measurement unit 2 measuring energy distribution of radiation intensity from the sample; an input unit 6 inputting a holding condition of the sample to the container; a computing determination unit 10 calculating radioactivity of the sample on the basis of weighed mass and the measured energy distribution of the radiation intensity, and comparing and determining with a specified value; and a display 7 displaying the determination result. The computing determination unit 10 can comprise: a total emissive power calculation unit 11 calculating total emissive power of the sample from the energy distribution of the radiation intensity; an activity concentration calculation unit 12 estimating mass of edible parts on the basis of the volume of the container, the mass and a sample classification, and calculating an activity concentration of the sample from a total emissive power; and a determination unit 13 comparing the activity concentration and an appointed specified value and determining whether the activity concentration is within the specified value.

Description

  Embodiments described herein relate generally to a radioactivity screening apparatus and a radioactivity screening method using the radioactivity screening apparatus.

  Contamination of foodstuffs including agricultural products and aquatic products is feared by radioactive materials. Food safety inspection includes fine inspection / confirmation inspection and screening inspection. Whereas the precision inspection and confirmation inspection are inspections for measuring the contamination value of the measurement object, the screening inspection determines whether the contamination of the measurement object (sample) is larger or smaller than a certain reference value. It is an inspection to do. The latter inspection is mainly used for self-inspection by a contractor.

  When measuring a sample in a container and calculating the radioactivity concentration, it is necessary to obtain a conversion constant for converting the count value to radioactivity in order to calculate the radioactivity concentration based on the count value of the measurement result. There is.

  Usually, it has been necessary to obtain a conversion constant based on the result of measurement using a radiation source having the same shape and density as the object to be measured and having already known nuclide and radioactivity. However, since the shape of the sample is various in the screening test, it is not realistic to prepare a radiation source for each shape of the sample.

  As a countermeasure when a radiation source having the same shape as the sample cannot be prepared, a technique is disclosed that uses the radioactivity conversion constant recorded according to the density, height, and dimensions of the object imaged by the camera. The method requires an imaging device, and cannot be applied to measurement in a state in which a plurality of samples are overlapped so that many samples are put in a container and measured together.

Japanese Patent No. 4831829

About test method of radioactive material in food, March 15, 2012, Director of Food Safety Department, Ministry of Health, Labor and Welfare Radioactive cesium screening method in food, Ministry of Health, Labor and Welfare, Pharmaceutical Food Bureau, Food Safety Department, Monitoring and Safety Division, March 1, 2012

  As one of the self-examination of food radioactivity inspection, inspection using a simple inspection device based on the screening method by the laws of the Ministry of Health, Labor and Welfare is carried out. Since the conventional simple inspection device has to take out the edible portion of the sample and uniformly fill the container, for example, for a sample (fruit, vegetable, fish) whose shape is not constant, take out the edible portion. It was necessary to perform pretreatment such as mincing. For this reason, it took time for pre-processing before measurement, and there was a problem that the measured sample could not be sold.

  Therefore, there has been a demand for a screening test method that does not require time-consuming pre-processing as in the prior art and enables a safe determination.

  Considering uncertainty such as errors caused by the measurement method and the method of calculating the radioactivity based on the count value, the calculated radioactivity differs from the actual radioactivity within a certain range. Although there will be, here, the safe side means that the side with the higher radioactivity is evaluated.

  An embodiment of the present invention has been made to solve the above-described problems, and an object thereof is to perform screening of a radioactivity level on the safe side without taking time for pretreatment.

  In order to achieve the above-described object, an embodiment of the present invention measures the mass of a container containing a sample in a radioactivity screening apparatus for determining the magnitude of a radioactivity defined value of a sample of a target food. A mass measurement unit; a radiation measurement unit that measures an energy distribution of radiation intensity from the sample; an input unit that inputs a storage condition of the sample in the container; a storage condition that is input by the input unit; and the mass The calculation determination unit that calculates the radioactivity of the sample based on the mass that is the measurement result measured by the measurement unit, and the energy distribution of the radiation intensity measured by the radiation measurement unit, and performs a comparison determination with a specified value, And a display unit for displaying a determination result in the calculation determination unit.

  In addition, the embodiment of the present invention includes a calculation determination unit that calculates the radioactivity of the sample based on the measurement result of the mass and radiation intensity of the sample of the target food and performs a comparison determination with a specified value, a mass database, a container A computer having a database including a volume database, a background database, and a conversion constant database, a mass measuring unit for measuring the mass in the storage unit, a radiation measuring unit for measuring the radiation intensity, and a storage condition for the sample are input. In the radioactivity screening method using the radioactivity screening apparatus, the input unit accepts the sample storage conditions, and the storage unit stores the sample stored in a container. The storing step for receiving and storing, and the mass measuring unit includes the sample. A mass measuring step for measuring the mass of the filled container, a radiation intensity measuring step for measuring the radiation intensity from the sample by the radiation measuring unit, and an operation determining unit for emitting radiation based on the measurement result of the radiation intensity. A radioactivity calculation step for calculating a radioactivity, and a determination step for determining whether or not the radioactivity of the sample is lower than a determination value by comparing the calculated radioactivity with a determination value. It is characterized by having.

  According to the embodiment of the present invention, the radioactivity level can be screened on the safe side without taking time for the pretreatment.

It is a block diagram which shows the structure of the radioactivity monitor in the radioactivity screening apparatus which concerns on the 1st Embodiment of this invention. It is the II-II arrow front view of FIG. 3 which shows the external shape of the radioactivity screening apparatus which concerns on the 1st Embodiment of this invention. It is a side view which shows the external shape of the radioactivity screening apparatus which concerns on the 1st Embodiment of this invention. It is a flowchart which shows the procedure of the radioactivity monitoring method using the radioactivity screening apparatus which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the structure of the radioactivity monitor in the radioactivity screening apparatus which concerns on the 2nd Embodiment of this invention. It is a flowchart which shows the procedure of the radioactivity monitoring method using the radioactivity screening apparatus which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the radioactivity monitor in the radioactivity screening apparatus which concerns on the 3rd Embodiment of this invention. It is a list which shows the example of the edible rate data for every fish kind used for the radioactivity monitor in the radioactivity screening apparatus which concerns on the 3rd Embodiment of this invention.

  Hereinafter, a radioactivity screening apparatus according to an embodiment of the present invention will be described with reference to the drawings. Here, the same or similar parts are denoted by common reference numerals, and redundant description is omitted.

[First Embodiment]
FIG. 1 is a block diagram showing a configuration of a radioactivity monitor in the radioactivity screening apparatus according to the first embodiment of the present invention.

  The radioactivity screening apparatus 1 includes a radiation measurement unit 2, a mass measurement unit 3, a calculation determination unit 10, an input unit 6, and a display unit 7. The radioactivity screening apparatus 1 includes a mass database 21, a container volume database 22, a background database 23, and a conversion constant database 24.

  The functions performed by the operation determination unit 10 and each of the above databases are realized by causing a general-purpose computer to read and execute program codes describing instruction codes for executing these functions. The program code may be stored in a storage medium such as a CD-ROM, a hard disk, or a memory card that can be read by a computer.

  The radiation measuring unit 2 measures the intensity of radiation from a sample of a target food (hereinafter referred to as “sample”) stored in a container. The radiation measurement unit 2 includes one or more radiation detectors 2a for measuring radiation, and a measurement unit 2b including a radiation detection signal processing circuit for obtaining an energy spectrum based on a signal from the radiation detector 2a. .

  By providing a radiation detection signal processing circuit for each radiation detector 2a, an energy spectrum is obtained for each radiation detector 2a. The energy spectrum may be obtained after summing up the output results of the respective radiation detectors 2a.

  When measurement is performed using two radiation detectors 2a, the radiation detectors 2a are installed so as to be point-symmetric in order to reduce the influence of uneven distribution of radioactive contamination contained in the sample. It is not limited to point symmetry. An appropriate arrangement may be set when a specific arrangement is desirable depending on the shape of the container and the arrangement of the container storage location.

  Radiation measurement is performed for a predetermined time. A user interface for changing the measurement time by the user may be provided, and the predetermined time may be changed for each measurement target.

  Examples of the radiation detector 2a of the radiation measuring unit 2 include an ionization chamber, a NaI scintillation detector, a BGO scintillation detector, a Ge semiconductor detector, a CdTe or CdZnTe semiconductor detector, a SiC semiconductor detector, and a plastic scintillation detector. Is used.

  The radiation measurement unit 2 includes a shielding material around the radiation detector 2a in order to reduce the influence from the surrounding environment. A shielding material may be provided if necessary in consideration of the surrounding environment. The count value processed by the radiation detection signal processing circuit of the measurement unit 2b is output to the arithmetic determination unit 10.

  The mass measuring unit 3 measures the mass of the container in which the sample is stored. Examples of the mass measurement method include a load cell method, an electromagnetic method, and a tuning fork method.

  The mass database 21 records the mass measured by the mass measurement unit 3. The mass database 21 may store only recently measured mass results as measured mass, or may record a plurality of previously measured results in consideration of using or referring to the mass measured later. Good. In the case of recording the result measured in the past, for example, it may be recorded together with one or more information of time, number of times, and user input value for easy use or reference later.

  The input unit 6 is an interface for the user to input sample storage conditions. Storage conditions include, for example, the filling height of the sample in the container and the edible rate of the sample.

  Here, the edible rate is the mass (hereinafter referred to as “edible mass”) of the portion of meat other than the bones and internal organs, that is, the portion that can be normally eaten (hereinafter referred to as “edible portion”). The ratio to the total mass of

  The input unit 6 may further include an interface for inputting or selecting a container type when there are a plurality of container types.

  Enter the value directly in the dialog box as an interface for entering the sample fill height. It is not limited to directly inputting a numerical value. For example, in the method of selecting from the filling heights displayed as candidates and the operational premise of filling the sample to a predetermined filling height, the container into which the sample is placed is given a symbol or color as an identifier, Alternatively, the identifier may be displayed as a candidate and selected.

  Enter the values directly into the dialog as an interface for entering the edible rate of the sample. In addition, it is not limited to inputting a numerical value directly. For example, a method may be used in which one or more of the edible rate, the type of sample, the classification, the name, or the shape of the sample are displayed as candidates and selected from them.

  When displaying candidates, for example, the candidates to be displayed may be recorded in the apparatus in advance, or publicly available information may be acquired and displayed via a network.

  As an interface for inputting the container type, any one or more of the height, width, depth, size, and identifier assigned to the container is directly input into the dialog box. The method is not limited to this method. For example, a method of displaying and selecting one or more of the height, width, depth, size, identifier attached to the container, or a photograph or picture of the container as a candidate may be used.

  In addition, when a different conversion constant is used for each type of measurement sample, an interface for selecting the type of measurement sample may be added. The type of measurement sample is entered directly in the dialog box. The method is not limited to this method. For example, any one or more of the sample type, classification, name, or shape may be displayed as candidates and selected from them.

  In addition, when the determination is made using the determination threshold value input by the user, a numerical value is input to the dialog as an interface for inputting the determination threshold value. In addition, it is not limited to inputting a numerical value directly. For example, a method may be used in which a plurality of determination threshold values are displayed as candidates and selected from them.

  A separate interface is provided for each input target. In addition, it is not limited to providing separately. For example, the same interface may be provided.

The container volume database 22 is a database that records at least the container mass from the relationship between the sample filling height and the sample volume. Record the vessel mass in relation to the sample fill height and volume relationship as shown in equation (1). It should be noted that one or more sets may be recorded as an aggregate such that the container mass from the sample volume and the filling height is one set.
Sample volume = A x filling height (1)
Here, A is a predetermined constant.

  When an interface for inputting a container type is provided, a container volume database is prepared for each container type input or selected by the user through the input unit 6. The method is not limited to this method. Even if the container mass and the container type from the relational expression of the sample volume and the filling height are recorded in association with each other, the container mass and the container type from the sample volume and the filling height are set as one set. One or more sets may be recorded as an aggregate.

  In addition, in the premise of the operation of filling the sample to a predetermined filling height, when the symbol or color attached to the container into which the sample is placed is input as an identifier in the input unit 6 instead of the filling height. Instead of the filling height, the identifier and the container mass from the sample volume are recorded in association with each other.

  In addition, on the premise of the operation of filling the sample with the container mass, the sample volume and the predetermined filling height, the conversion constant, the sample type, and the edible rate are recorded in advance on the container using an IC tag or barcode. In addition, by reading it before starting the measurement, a configuration that does not require a database may be realized.

  The background database 23 records the energy spectrum output from the radiation measurement unit 2 when measured without a sample.

The conversion constant database 24 records the relationship between the sample mass, the sample volume, and the radioactivity conversion constant determined in advance. As for the relationship between the sample mass, the filling height, and the sample volume, the relational expressions shown in the formulas (2), (3), and (4) are recorded, and the formula to be used is selected from these. Note that the relational expressions shown in Expression (2), Expression (3), and Expression (4) are shown as examples, and are not limited to these. If an appropriate relational expression is obtained empirically, it can be changed. Also good. Further, for example, the sample volume, the sample mass, and the radioactivity conversion constant may be recorded as one set, and one or more sets may be recorded as an aggregate. The bulk density in each equation is a value obtained by dividing the sample mass by the sample volume.
Radioactivity conversion constant = bulk density × fa1 (sample mass) + fa2 (sample mass)
(2)
Here, fa1 and fa2 are constants whose values are uniquely determined by a predetermined sample mass.
Radioactivity conversion constant = (1-e ^Y ) × fb 2 (sample mass) (3)
However, Y = −fb1 (sample mass) × bulk density Here, fb1 and fb2 are constants whose values are uniquely determined by a predetermined sample mass.
Radioactivity conversion constant = bulk density ² × fc1 (sample mass)
+ Bulk density × fc2 (sample mass) + fc3 (sample mass) (4)
Here, fc1, fc2, and fc3 are constants whose values are uniquely determined by a predetermined sample mass.

The relationship between the sample mass, sample volume, and radioactivity conversion constant is determined by the following method.
First, a model simulating the same measurement system (position and density) as the radioactivity monitor is created in a virtual space. The sample volume, the radioactivity and distribution of the sample, the sample mass are set, and the simulation is performed under the conditions set in this way. For example, a conversion constant is obtained from the radiation count value measured by the radiation measurement unit 2 calculated by the simulation, that is, the simulation count value, and the radioactivity of the set sample, that is, the set radioactivity, by Equation (5).
Radioactivity conversion constant = set radioactivity / simulation count (5)
In addition, when different radioactivity conversion constants are defined for each nuclide, the relationship between the nuclide, sample volume, sample mass, and radioactivity conversion constant is recorded.

When a different radioactivity conversion constant is determined for each container type, the relationship between the container type, sample mass, sample volume, and radioactivity conversion constant presented to the user by the input unit 6 is recorded.
When a different radioactivity conversion constant is determined for each sample type, the relationship between the sample type, sample mass, sample volume, and radioactivity conversion constant presented to the user by the input unit 6 is recorded.

In addition, when the conversion constant data for each sample type is prepared, or when the container type is added and recorded as one set, the sample filling height may be used instead of the sample volume.
In addition, on the assumption of the operation of filling the sample to a predetermined filling height, the conversion constant database 24 may record only the relationship between the sample mass and the radioactivity conversion constant.

The operation determination unit 10 includes a total radioactivity calculation unit 11, a radioactivity concentration calculation unit 12, and a determination unit 13.
The total radioactivity calculation unit 11 calculates the count value of the energy range of one or more nuclides to be monitored from the integrated value for a predetermined time in a predetermined region on the energy spectrum obtained by the radiation measurement unit 2. The integrated value is calculated as the total count value of the monitor nuclide.

  From the total count value of the monitor nuclides, the measurement result in the absence of the sample recorded in the background database 23 is referred to, and the influence value is subtracted to obtain the count value of the monitor target. The total count value of the energy range of the nuclide to be monitored is calculated by the following first integration method. The method is not limited to this method. You may calculate by the 2nd integration method and the 3rd integration method shown below.

  First integration method: For a nuclide whose presence is confirmed by a peak search after obtaining an integrated value in a predetermined energy range, an abundance ratio or a predetermined presence obtained from the peak count or peak detection efficiency The ratio is obtained by multiplying the integrated value of the count by the existence ratio.

  Second integration method: For a nuclide whose existence is confirmed by a peak search within a predetermined energy range, a portion determined to be a peak is extracted and a peak area is calculated for each peak.

  Third integration method: From the peak center corresponding to the energy of the target target nuclide determined in advance, a peak region is set on both sides using a predetermined formula, and the area of the region is calculated. You may consider the influence of the scattering area | region set to the both outer sides with respect to the total count number of the said energy area | region.

  When there are a plurality of detectors in the radiation measuring unit 2, the calculation is performed by the following first total count value integration method. The method is not limited to this method. You may calculate by the integration method of the 2nd total count value shown below.

  First total count value integration method: From spectrum data obtained by a plurality of detectors, reference spectrum data is selected as reference spectrum data, and the target nuclide predetermined for other spectrum data is selected. In accordance with the peak, the difference between the gain and the zero point is obtained from the reference spectrum, the difference is corrected, the spectra are added up, and the total coefficient value of the nuclide to be monitored is obtained from the added up spectrum. At this time, if the spectrum data of the detector with the lowest energy resolution is used as the reference spectrum data, and the parameters necessary for calculating the total count value of the nuclide to be monitored are different for each detector, those of the reference spectrum data are used. use.

  Second total count value integration method: For each of a plurality of detectors, obtain a total coefficient value for each nuclide to be monitored, select a maximum value, add up, or calculate an average value. Numerical value.

Since the total radioactivity calculation unit 11 extracts the measured mass recorded in the mass database 21 from the container volume database 22, the total radioactivity calculation unit 11 obtains the sample mass from the container mass using Equation (6).
Sample mass = measured mass-to container mass (6)
The conversion constant database 24 is calculated from the sample volume extracted from the container volume database 22 and the sample mass using the filling height input by the input unit 6 or the symbol or color representing the selected filling height or filling height as an identifier. The conversion constant is extracted from. Using the extracted conversion constant and the count value to be monitored, for example, the total radioactivity is obtained using Equation (7).
Total radioactivity = Conversion constant x Monitored value (7)

  In addition to sample mass and sample volume, if different conversion constants are prepared for each container type, different conversion constants are prepared for each container type, and for each nuclide, different conversion constants are prepared for each nuclide and sample type. If so, the conversion constant is extracted using the sample type.

  Further, for example, the data of the container volume database 22 is discretely recorded, and the filling height equal to the filling height input by the input unit 6 is found from the filling heights recorded in the container volume database 22. If not, the sample volume recorded together with the filling height closest to the filling height recorded in the container volume database 22 is extracted as the sample volume. The method is not limited to this method.

  For example, one set of container masses from the filling height and sample volume satisfying the following conditions 1 and 2 is extracted, and the sample volume is calculated by linear interpolation using equation (8), for example. May be.

(Condition 1): Input filling height <filling height value in container volume database 22 (condition 1 filling height value) and (input filling height−filling height value in container volume database 22) ² minimum.

(Condition 2): Input filling height> filling height value in the container volume database 22 (condition 2 filling height value) and (user input filling height−filling height value in the container volume database 22) ² Is the smallest.

Sample volume = volume satisfying condition 2+ (condition 1 filling height value−condition 2 filling height value) × (user input filling height−condition 2 filling height value) × (sample volume satisfying condition 1−condition 2 Sampling sample volume) (8)
If the data of the conversion constant database 24 is recorded discretely and the data equal to the sample volume and the sample mass is not recorded, the closest sample mass and sample volume pair is searched similarly to the sample volume. Use the conversion constant. The method is not limited to this method. For example, a conversion constant may be obtained by extracting a plurality of sets of sample masses and sample volumes and performing linear interpolation using a method similar to obtaining the sample volume from the container volume database.

The total radioactivity calculation unit 11 calculates the total radioactivity according to Equation (9) using the count value of the nuclide to be monitored and the conversion constant.
Total radioactivity = Count value of nuclide to be monitored x Conversion constant (9)
The calculated total radioactivity is input to the radioactivity concentration calculation unit 12.

The radioactivity concentration calculation unit 12 uses the measured mass recorded in the mass database 21, the container mass extracted from the container volume database 22, and the edible rate input or selected from the input unit 6 to obtain an equation ( The edible mass is calculated according to 10).
Edible mass = (measured mass-to container mass) x edible rate (10)

The radioactivity concentration calculation unit 12 calculates the radioactivity concentration by the equation (11) using the total radioactivity and the edible mass output from the total radioactivity calculation unit 11.
Radioactivity concentration = total radioactivity / edible mass (11)

  The determination unit 13 calculates the radioactivity concentration output from the radioactivity concentration calculation unit 12, the determination threshold value recorded in advance, or the determination threshold value input by the input unit 6 and the radioactivity concentration calculation unit 12. The value obtained by dividing the measurement lower limit calculated using the spectrum data recorded in the background database 23 and the spectrum input from the radiation measurement unit 2 by the edible mass, Compare the measurement lower limit concentration with the measured radioactivity concentration, and output the judgment result.

The display unit 7 displays the determination result in the determination unit 13 of the calculation determination unit 10. When it is determined that the measured radioactivity concentration is smaller than the determination threshold value, a content indicating that there is no contamination is displayed.
As contents meaning that there is no contamination, for example, at least one of a character with no contamination or a symbol or color meaning it is displayed.

When it is determined that the measured radioactivity concentration is smaller than the measurement lower limit concentration, the contents indicating the measurement lower limit are displayed.
As contents meaning the measurement lower limit, for example, at least one of a measurement lower limit letter, a symbol or color meaning the same, or a measurement lower limit concentration is displayed.
One or more values obtained by dividing a predetermined measurement lower limit value by edible mass are displayed.

  2 is a front view of the radioactivity screening apparatus according to the first embodiment of the present invention as viewed from the direction of arrows II-II in FIG. FIG. 3 is a side view showing the outer shape of the radioactivity screening apparatus according to the first embodiment of the present invention.

  In the radioactivity screening apparatus 1, each component is housed in a housing 8, and the entire apparatus is integrated. In the housing 8, a storage portion 9 is provided as a space for storing the sample storage container 5. The sample storage container 5 is stored in the storage unit 9 in a state where the sample is stored, and is mounted on the mass measuring unit 3. Two radiation detectors 2 a are arranged on both side surfaces of the container 5. The housing 8 has casters 8a and is movable. In addition, it is not restricted to a caster. For example, a fixed type may be used.

  The number of radiation detectors 2a is not limited to two. One unit may be used depending on the amount of the sample that can be stored in the container. Further, in the case of a large size, three or more units may be used in order to further improve the measurement accuracy.

  The container 5, the mass measuring unit 3, and the radiation detector 2a are accommodated in the shielding body 4 to suppress the influence of external radiation. A measuring unit 2b and a computer 30 are housed outside the shielding body 4.

  The computer 30 has functions of an operation determination unit 10, a mass database 21, a container volume database 22, a background database 23, and a conversion constant database 24.

  FIG. 4 is a flowchart showing the procedure of the radioactivity monitoring method using the radioactivity screening apparatus according to the first embodiment of the present invention.

First, the input sample storage conditions are received by the input unit 6 (step S1).
After step S1, the radioactivity screening apparatus 1 receives and stores the sample stored in the container 5 (step S2).

Since the container 5 is mounted on the mass measuring unit 3 in step S2, mass measurement by the mass measuring unit 3 is performed (step S3).
After step S3, the radiation intensity is measured by the radiation measuring unit 2 (step S4).

Based on the output measurement result in step S3 and the radiation intensity measurement result in step S4, the total radioactivity concentration of the sample is calculated in the total radioactivity calculation unit 11 of the operation determination unit 10 (step S5).
After Step 5, the radioactivity concentration calculation unit 12 of the calculation determination unit 10 calculates the radioactivity concentration based on the total radioactivity concentration and the edible mass (Step S6).

After step S6, the determination unit 13 of the calculation determination unit 10 determines whether or not the radioactivity concentration obtained in step S6 is smaller than a specified value (step S7).
The determination result in the determination unit 13 in step S7 is displayed on the display unit 7 (step S8).

  According to the present embodiment configured as described above, the radioactivity level can be screened on the safe side without taking time for sample pretreatment.

[Second Embodiment]
FIG. 5 is a block diagram showing the configuration of the radioactivity monitor in the radioactivity screening apparatus according to the second embodiment of the present invention.

  This embodiment is a modification of the first embodiment. The radioactivity screening apparatus 1 further has a systematic error database 25. The operation determination unit 10 further includes a systematic error correction unit 14.

The systematic error database 25 is a database that records systematic errors calculated in advance. Systematic errors are systematic errors caused by specific factors. For example, errors due to simulation, errors due to how the sample is filled, errors in radiation intensity measurement due to errors in the position where the container is placed, and individual errors determined by simulation The error which the contamination difference of the individual gives to the measurement result can be considered.
Further, when there are a plurality of errors, the systematic error may be obtained using, for example, Expression (12).

Systematic error = ((X1 ² ) + (X2 ² ) + (X3 ² ) +...) ^1/2 (12)
(X1, X2, X3,... Are errors due to respective factors.)
The radioactivity concentration calculation unit 12 calculates the radioactivity concentration of the edible part from the total radioactivity input from the total radioactivity calculation unit 11 and the edible mass obtained by referring to the mass database 21 and the container volume database 22. calculate.

Further, the systematic error correction unit 14 uses the systematic error obtained by referring to the systematic error database 25 to calculate the corrected radioactivity concentration by, for example, Expression (13).
Radioactivity concentration = total radioactivity / edible mass / (1-system error) (13)
The calculated radioactivity concentration after correction is output to the display unit 7.

FIG. 6 is a flowchart showing the procedure of the radioactivity monitoring method using the radioactivity screening apparatus according to the second embodiment of the present invention. A step (S9) in which the systematic error correction unit 14 evaluates the systematic error and corrects the radioactivity concentration is further added to the first embodiment.
In this way, by correcting the calculated radioactivity value in consideration of systematic errors, further safety evaluation and determination can be performed.

  According to the present embodiment configured as described above, the radioactivity level can be screened on the safe side without taking time for sample pretreatment.

[Third Embodiment]
FIG. 7 is a block diagram showing the configuration of the radioactivity monitor in the radioactivity screening apparatus according to the third embodiment of the present invention. This embodiment is a modification of the second embodiment and further includes a food database 26.

  The food database 26 records sample type data corresponding to the type of sample. Sample type data includes an edible rate.

  FIG. 8 is a list showing an example of edible rate data for each fish type used for the radioactivity monitor in the radioactivity screening apparatus according to the third embodiment of the present invention. FIG. 8 shows a case where the target food is fish, but as shown in the figure, the edible rate varies greatly depending on the type of fish. Here, the type means the type of fish, such as mackerel, skipjack, horse mackerel, etc. when the food is fish.

Since the sample type data is recorded in the food database 26, the input unit 6 does not need to input the edible rate of the sample or the like for the storage condition, and only the type needs to be specified. When the type is designated by the input unit 6, the radioactivity concentration calculation unit 12 reads the edible rate according to the type from the food database 26 and performs calculation.
According to the present embodiment configured as described above, the user's input is reduced.

[Other Embodiments]
As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. For example, although each embodiment showed the case where the foodstuff made into fish was fish, it is not limited to this. For example, sea urchins and shellfish may be used. Fruits and vegetables may also be used.

Moreover, you may combine the characteristic of each embodiment. For example, the features in the third embodiment may be combined with the first embodiment.
Furthermore, these embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention.
These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Radioactivity screening apparatus, 2 ... Radiation measurement part, 2a ... Radiation detector, 2b ... Measurement unit, 3 ... Mass measurement part, 4 ... Shielding body, 5 ... Container, 6 ... Input part, 7 ... Display part, 8 ... Case, 8a ... Caster, 9 ... Storage part, 10 ... Calculation determination part, 11 ... Total radioactivity calculation part, 12 ... Radioactivity concentration calculation part, 13 ... Determination part, 14 ... System error correction part, 21 ... Mass Database, 22 ... Container volume database, 23 ... Background database, 24 ... Conversion constant database, 25 ... System error database, 26 ... Food database, 30 ... Computer

Claims (16)

In the radioactivity screening device that determines the magnitude of the radioactivity of the target food sample,
A mass measuring unit for measuring the mass of the container containing the sample;
A radiation measurement unit for measuring an energy distribution of radiation intensity from the sample;
An input unit for inputting storage conditions of the sample in the container;
Calculate and specify the radioactivity concentration of the sample based on the storage conditions input at the input unit, the mass as the measurement result measured at the mass measurement unit, and the energy distribution of the radiation intensity measured at the radiation measurement unit A calculation determination unit for performing a comparison determination with a value;
A display unit for displaying a determination result in the calculation determination unit;
A radioactivity screening apparatus comprising: The calculation determination unit
A total radioactivity calculator that calculates the total radioactivity of the sample from the energy distribution of the radiation intensity;
Calculate the mass of the edible part based on the volume of the container, the mass and the sample type, and calculate the radioactivity concentration of the sample from this result and the calculated total radioactivity, and
A radioactivity determination unit that compares the radioactivity concentration with a specified value and determines whether the radioactivity concentration is within the specified value; and
The radioactivity screening apparatus according to claim 1, comprising: A mass database that records and stores the mass for a plurality of the samples;
A container volume database that records and stores the relationship between the filling height and volume in the container;
A conversion constant database that stores conversion data for converting the radiation intensity into the radioactive concentration based on the radiation intensity and the mass and the volume of the sample;
The radioactivity screening apparatus according to claim 1, further comprising:   The radioactivity screening apparatus according to claim 3, wherein the conversion data includes a conversion formula and a constant depending on a nuclide in the conversion formula. It further comprises a systematic error database for storing systematic error data that may occur when calculating radioactivity,
The calculation determination unit is a systematic error correction unit that calculates a corrected radioactivity concentration based on the radioactivity concentration value calculated by the radioactivity concentration calculation unit and the systematic error data stored in the systematic error database. Further having
The radioactivity screening apparatus according to any one of claims 2 to 4, wherein the radioactivity screening apparatus is characterized.   The systematic error correction unit normalizes the systematic error stored in the systematic error database and subtracts the normalized systematic error value from 1 to divide the radioactivity concentration value to correct radiation. The radioactivity screening apparatus according to claim 5, wherein the radioactivity concentration is calculated. The systematic error database stores at least two types of systematic errors,
The systematic error correction unit is a value obtained by standardizing at least two types of systematic errors stored in the systematic error database and subtracting the square root of the square sum of the standardized systematic error values from 1. Calculate the corrected radioactivity concentration by dividing the active concentration value.
The radioactivity screening apparatus according to claim 5.   The radioactivity screening apparatus according to claim 2, further comprising a food database that records sample type data corresponding to the type of the sample.   The said display part displays the content which shows that it is below a regulation value, when it determines with the said radioactivity concentration measurement value being within the said regulation value in the said radioactivity judgment part, It is characterized by the above-mentioned. The radioactivity screening apparatus according to any one of claims 2 to 8. The radiation measurement unit includes a first detector and a second detector provided symmetrically with respect to the center of the container,
The total radioactivity calculation unit is based on the reference spectrum data of the reference detector with respect to the spectrum data that is the energy distribution of the two radiation intensities acquired by the first detector and the second detector, Using the energy peak of the target nuclide recorded in advance as a base point, the difference between the reference spectral data and the spectral data of the first detector is obtained for the gain and the zero point, and the spectral data of the second detector is obtained. Then, after correcting the difference, a result obtained by adding the reference spectrum data and the spectrum data of the second detector is output as spectrum data.
The radioactivity screening apparatus according to any one of claims 2 to 9, wherein the radioactivity screening apparatus is characterized.   The total radioactivity calculation unit calculates the abundance ratio for each nuclide obtained from the peak count value or peak detection efficiency for the nuclide whose presence is confirmed by the peak search from the integrated value of the count in a predetermined energy range. By multiplying the value and subtracting the influence of the background, the count value per fixed time is obtained for each nuclide, the conversion constant recorded in the conversion constant database is extracted for each nuclide, and obtained for each nuclide. 11. The radioactivity for each individual nuclide contained in the sample is calculated by multiplying the count value per fixed time by the conversion constant, according to any one of claims 2 to 10. The radioactivity screening apparatus described.   The total radioactivity calculation unit subtracts the influence of the background from the integrated value of the count of the energy range determined to be the peak for the nuclide whose existence was confirmed by the peak search in the predetermined energy range. By calculating the count value per fixed time, extracting the conversion constant recorded in the conversion constant database for each nuclide, and multiplying the count value per fixed time determined for each nuclide by the conversion constant, The radioactivity screening apparatus according to any one of claims 2 to 11, wherein the radioactivity for each individual nuclide contained in the sample is calculated.   The total radioactivity calculation unit calculates a radioactivity ratio for each nuclide using a predetermined ratio of one or more nuclides from an integrated value of a count of one or more energy ranges determined in advance, By multiplying the integrated value by the radioactivity ratio and subtracting the influence of the background, a count value per fixed time is obtained for each of one or more nuclides, and the conversion constant recorded in the conversion constant database for each nuclide The radioactivity for each individual nuclide contained in the sample is calculated by extracting the value and multiplying the count per fixed time obtained for each nuclide by the conversion constant. The radioactivity screening apparatus according to claim 12. An operation determination unit that calculates the radioactivity of the sample based on the measurement result of the mass and radiation intensity of the target food and compares it with the specified value, a mass database, a container volume database, a background database, and a conversion constant Radiation comprising: a computer having a database including a database; a mass measuring unit for measuring the mass in the storage unit; a radiation measuring unit for measuring the radiation intensity; and an input unit for inputting the storage conditions of the sample. In a radioactivity screening method using a screening apparatus,
An input step in which the input unit receives a storage condition of the sample;
A storage step in which the storage unit receives and stores the sample stored in a container; and
A mass measuring step in which the mass measuring unit measures the mass of the container filled with the sample;
A radiation intensity measuring step in which the radiation measuring unit measures a radiation intensity from the sample;
The calculation determination unit calculates a radioactivity concentration based on the measurement result of the radiation intensity, and a radioactivity concentration calculation step,
A step of determining whether the calculation determination unit compares the calculated radioactivity concentration with a determination value to determine whether the radioactivity concentration of the sample is lower than a determination value;
A radioactivity screening method comprising:   The radioactivity screening method according to claim 14, wherein in the radioactivity concentration calculation step, the calculation determination unit includes a correction step in which the calculation determination unit corrects the edible rate. .   15. The method according to claim 14, further comprising a correction step in which the calculation determination unit performs systematic error evaluation and corrects the radioactive concentration after the radioactive concentration calculation step and before the determination step. The radioactivity screening method according to claim 15.

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