JP2014173991A - Specific radioactivity inspection system of fish - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a specific radioactivity inspection system of a fish in which a whole individual fish can be continuously and efficiently inspected, and capable of sorting the fish for each specific radioactivity with sufficient accuracy.SOLUTION: A specific radioactivity inspection system 1 of a fish according to the present invention includes: a weight measuring table 3 for performing individual identification and also performing weight measurement of a plurality of fishes; a belt conveyer 4 for conveying the plurality of fishes in a row in a predetermined conveying direction A; a plurality of radiation detectors 7 positioned below the plurality of fishes to be conveyed and arranged side by side in the conveying direction A; a pair of radiation shielding walls 16, 17 positioned on the right and left sides of the plurality of fishes subjected to radiation detection and provided along the conveying direction A; radiation shielding members 11, 14 provided to surround the underside and both left and right sides of the radiation detector 7; a control part 6 for individually calculating the specific radioactivity of the fish based on individual identification information, a weight measuring result, and a radiation detection result; and a sorter 5 for sorting the fish based on the calculation result of the specific radioactivity.

Description

  The present invention relates to a specific activity inspection system for inspecting the specific activity of fish.

  Conventionally, as a device for inspecting clothes for radiation contamination, a radiation contaminant sorting device described in Japanese Patent Application Laid-Open No. 58-139090 is known. This apparatus includes a transport means for transporting clothes, a plurality of radiation detectors arranged in the transport direction, a signal processing circuit that adds and integrates signals from each radiation detector, and radiation from signals from the signal processing circuit. And sorting means for sorting clothes that are contaminated with water, and an object is to efficiently perform a radiation contamination inspection of a large amount of clothes.

JP 58-139090 A

  At present, fish grown in the sea contaminated by nuclear power accidents may contain radioactive cesium, and sometimes fish whose radioactive contamination exceeds the standard value is landed at the fishing port, and there are restrictions on the fishing grounds where they were landed. Has been done. The problem of fish contamination is related not only to consumer safety, but also to fishermen's willingness to work and livelihoods. For this reason, there is a strong demand for the development of an inspection system that gives consumers peace of mind by individually and efficiently inspecting fish for radiation contamination, as well as motivates producers and contributes to the recovery of fishing ports.

  In addition, the standard for shipping fish by the country has become stricter after the earthquake, and it is necessary to appropriately measure whether or not radiation of the same level as the level of natural radiation originates from fish. It is also possible to measure in an environment where radioactive materials (cesium 134, 137) from nuclear power plants are present even in trace amounts, and shield as much as possible background radiation emitted from radioactive materials other than fish. There is a need.

  Conventionally, such a radiation contamination inspection of fish has been performed by using a radiation detector with a small container and grinding the fish. However, when the fish is crushed, even if there is no radiation contamination, the fish cannot be returned to the market after that, which has been a problem in performing a total inspection of the fish.

  On the other hand, as a device for inspecting fish for radiation contamination, a device having one radiation detector on a gate provided so as to straddle a belt conveyor has been developed. In this device, a plurality of fish are put in a foamed polystyrene box or the like and passed under the gate, so that the radioactive contamination of the plurality of fish can be inspected collectively.

  However, since it is assumed that the apparatus having such a configuration is measured in units of boxes, it is not possible to efficiently measure fish one by one, and to accurately locate each contaminated fish one by one. It is necessary to repeat the inspection many times. In addition, since there is only one radiation detector, the inspection takes time and there is a problem that no countermeasures are taken for background radiation.

  Therefore, the present invention aims to provide a specific radioactivity inspection system for fish that can inspect the specific radioactivity continuously and efficiently, and can accurately classify fish by specific radioactivity. To do.

  In order to solve the above-mentioned problems, the present invention is a specific radioactivity inspection system for inspecting specific radioactivity of a plurality of fish, wherein individual labeling means for individually labeling a plurality of fish and individual weight measurement of the plurality of fish are performed. A weight measuring unit; a conveying unit configured to convey a plurality of fish in a row in a predetermined conveying direction; and a plurality of radiation detectors provided below the plurality of fishes conveyed by the conveying unit and arranged in the conveying direction. A pair of radiation shielding walls located on the left and right sides of a plurality of fish whose radiation is detected by the radiation detector and provided along the transport direction, and radiation shielding provided so as to surround the lower side and the left and right sides of the radiation detector. A calculation means for individually calculating the specific activity of the fish based on the member, the individual labeling information of the individual labeling means, the weight measurement result of the weight measuring means, and the radiation detection results of a plurality of radiation detectors; Release Characterized in that it comprises a sorting means for sorting fish on the basis of the ability of the calculation result.

  According to the specific radioactivity inspection system according to the present invention, by arranging a plurality of radiation detectors along the transport direction and detecting the radiation of the fish while being transported on it, individually over the same time as the transport time, The detection result similar to the case where the radiation of fish is detected can be obtained, and the whole fish can be inspected continuously without processing the fish. Further, in this specific radioactivity inspection system, individual labels and weights of a plurality of fish arranged in a row are measured, and the specific radioactivity Bq obtained by dividing the radioactivity Bq of individual fish obtained from the radiation detection result by the weight kg of the fish. Since / kg can be obtained, it is possible to efficiently classify fish according to specific activity. In addition, according to the specific radioactivity inspection system, the radiation shielding member is located below the fish, and the pair of radiation shielding walls are located on the left and right of the fish, thereby shielding radiation from the ground or a concrete floor toward the fish. Therefore, the radiation detection background can be reduced and the radiation from the fish can be detected with high accuracy. Moreover, according to this specific radioactivity inspection system, it is possible to facilitate the monitoring, trouble handling, and maintenance of the state of fish transport by opening the upper part of the fish being transported. Furthermore, according to this specific radioactivity inspection system, since the radiation detector is located below the fish, it is possible to detect the radiation of the fish regardless of the size of the fish compared to the case where the radiation detector is located above or to the side of the fish. The distance of the vessel can be minimized, and the accuracy of radiation detection can be improved. As described above, according to the specific activity inspection system, it is possible to inspect the specific activity continuously and efficiently, and to classify the fish according to the specific activity with high accuracy.

The specific activity inspection system according to the present invention may further include a stainless steel cover that covers at least the upper surfaces of the plurality of radiation detectors.
According to this specific radioactivity inspection system, it is possible to improve the durability of the equipment by appropriately protecting the radiation detector, and to cope with frequent washing for maintaining hygiene, which is useful as a fish inspection system. It is a configuration.

Further, in the specific radioactivity inspection system according to the present invention, the calculation means has a position detection sensor for detecting whether or not the fish is passing through a predetermined position in the transport means, and the calculation means includes the position detection sensor. Based on the detection result, the tip arrival time and the end arrival time of the fish may be recognized.
According to this specific radioactivity inspection system, a simple position detection sensor can recognize the arrival time and end arrival time of a fish to grasp the position of each individual fish, simplifying the system configuration and manufacturing cost of the system It is advantageous for reduction of

Further, in the specific radioactivity inspection system according to the present invention, the computing means recognizes the position of the individual fish based on the individual label information of the individual labeling means and the transport speed of the transport means, and the radiation detector detects radiation. Alternatively, it may be counted as radiation detection of a fish located closest to the radiation detector.
According to this specific radioactivity inspection system, the position of individual fish can be easily grasped based on the conveyance speed without performing detailed position detection, and the result of radiation detection is appropriately used as the detection result of individual fish. Can be counted. This contributes to simplification of the system configuration and reduction of the manufacturing cost of the system.

Further, in the specific activity inspection system according to the present invention, when the calculation means determines that the radiation detector at a position equidistant from the preceding and following fish has detected the radiation, the radiation of the fish whose head is close to the radiation detector. You may count as detection.
According to this specific radioactivity inspection system, considering the structure of the fish, it is more likely to detect radiation from the head than the fish tail. By doing so, detection errors can be avoided and the reliability of radiation detection can be improved.

The specific radioactivity inspection system according to the present invention may further include a pair of guides arranged on the left and right of the fish being transported by the transport means.
According to this specific radioactivity inspection system, when measuring live fish one by one, it is possible to prevent the fish from moving during the measurement and changing its position with a pair of left and right guides, thereby improving measurement accuracy. be able to.

In the specific activity inspection system according to the present invention, the radiation detector is a scintillator that emits light upon incidence of radiation, a light guide that transmits light generated by the scintillator, and a signal according to light input through the light guide. The output photomultiplier tube may be provided, and the scintillator and the photomultiplier tube may be arranged so as not to overlap each other when viewed from the vertical direction.
According to this specific radioactivity inspection system, since the scintillator and the photomultiplier tube are arranged so as not to overlap when viewed from the vertical direction, even if radiation enters from the lower ground through the photomultiplier tube, Reaching the scintillator is avoided. Therefore, according to this specific radioactivity inspection system, since the radiation background can be reduced, the accuracy of detecting the radiation of fish can be improved.
Even when the scintillator and the photomultiplier tube are connected in series, the scintillator can be mounted by reducing the diameter of the photomultiplier tube and installing a shield larger than the photomultiplier tube directly under the photomultiplier tube. The ground can be hidden directly.

In the specific activity inspection system according to the present invention, the light guide may connect a plurality of scintillators to one photomultiplier tube.
According to this specific activity inspection system, the number of required photomultiplier tubes can be reduced, so that the manufacturing cost of the system can be greatly reduced.

  According to the specific activity inspection system according to the present invention, it is possible to inspect the specific activity continuously and efficiently, and to classify the fish according to the specific activity with high accuracy.

1 is a schematic plan view showing an embodiment of a specific radioactivity inspection system according to the present invention. It is a schematic side view of the specific radioactivity inspection system shown in FIG. It is a partial expanded sectional view for demonstrating arrangement | positioning of a radiation detector. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 3. It is a figure of the whole specific radioactivity inspection system including a building. (A) It is a figure which shows the detection of the tip arrival time [N, ts1] in the Nth fish. (B) It is a figure which shows the detection of the terminal arrival time [N, tm1] in the Nth fish. It is a figure for demonstrating the radiation detection from a fish. It is a figure for demonstrating determination of the fish which detected the radiation by the control part. It is a figure for demonstrating the case where the radiation detector 7 located in equidistant with the front and back fish detects a radiation. It is an explanatory graph for calculating radioactivity from radiation detection. (A) It is a top view which shows the radiation detector which concerns on a 1st modification. (B) It is a side view which shows the radiation detector which concerns on a 1st modification. (A) It is a top view which shows the radiation detector which concerns on a 2nd modification. (B) It is a side view which shows the radiation detector which concerns on a 2nd modification. It is a side view which shows the radiation detector which connected the scintillator and the photomultiplier tube in series using the photomultiplier tube of a small diameter.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

  The specific activity inspection system 1 shown in FIGS. 1 and 2 is a system that continuously and individually inspects a plurality of fish for specific activity Bq / kg. The specific radioactivity inspection system 1 includes a slope table 2 into which fish is introduced, a weight measuring table 3 for measuring the weight of the fish, a belt conveyor 4 for conveying the fish in a predetermined conveying direction A, and a sorting machine for separating the fish. 5 and a control unit 6 for controlling them. In each figure, a symbol S is used to indicate a fish.

  The slope base 2 is a base that is inclined so that the fish slides down toward the exit at the tip. The width of the slope table 2 is narrowed as it approaches the outlet 2a that is a belt conveyor, and the outlet 2a has a width that allows only one fish to pass through. The plurality of fish thrown into the slope table 2 gently slide down toward the exit 2a, are separated one by one through the exit 2a, and rest on the exit 2a. The fish that has been separated and stopped at the outlet 2a is measured by the weight measuring table and sent to the belt conveyor 4, and then placed on the weight measuring table 3 by the belt conveyor.

  The weight measuring table 3 is weight measuring means for measuring individual weights of fish. The weight measuring table 3 has a function of an individual marking means for measuring the weight of the fish with a built-in weighing scale and individually marking the fish. The weight measuring table 3 performs individual marking of fish according to the order of measurement. The weight measurement table 3 sends the individual marker data and the weight measurement data of the fish to the control unit 6. The weight measuring table 3 sends the measured fish quickly to the next belt conveyor 4 by tilting the table or moving the table or moving the surface of the table.

  Further, the weight measuring table 3 may determine the direction of the fish (whether the head is front or back) by measuring the weight balance. In this case, the weight measuring table 3 sends the fish direction data linked to the individual marker data to the control unit 6. The gravity measuring means preferably has a structure in which the weight of each fish is instantaneously measured and the fish is continuously sent to the belt conveyor 4 as much as possible without any gaps. Since (weight measurement time) × (velocity of the belt conveyor 4) is the distance between the fish on the belt conveyor 4, this distance must be longer than the length of one fish. Accordingly, the weight measurement time becomes (length of one fish) / (speed of the belt conveyor 4) or more. For example, if the length of the fish is 0.3 m and the speed of the belt conveyor is 0.75 m / second, the weight measurement time needs to be 0.4 seconds or more. Therefore, when the weight measurement time is 1 second, the distance between fishes is 0.45 m. A configuration may be adopted in which after measuring the weight in a short time, the measuring table is tilted and the fish is sent forward softly in a short time, or the surface of the table is moved and sent out. Further, when moving the surface of the table in the weight measuring table, the moving speed is preferably the same as the moving speed of the belt conveyor 4. Thereby, inspection efficiency can be raised.

  The belt conveyor 4 is a conveying means that conveys fish toward the sorter 5. The belt conveyor 4 includes an endless belt that circulates, and the forward path is on the upper side and the return path is on the lower side. The length from the entrance to the exit of the belt conveyor 4 can be, for example, about 9 m. Moreover, the conveyance direction A of the belt conveyor 4 may be bent instead of a straight line. A plurality of radiation detectors 7 are arranged below the fish conveyed to the belt conveyor 4.

  Hereinafter, the radiation detector 7 will be described. FIG. 3 is a partial enlarged cross-sectional view for explaining the arrangement of the plurality of radiation detectors 7. 4 is a cross-sectional view taken along line IV-IV in FIG. As shown in FIGS. 3 and 4, a large number (for example, 40) of radiation detectors 7 are provided so as to be aligned in the transport direction A, and are located below the fish transported by the belt conveyor 4. . That is, the radiation detector 7 detects radiation from below the fish.

  The radiation detector 7 includes a scintillator 8, a light guide 9, and a photomultiplier tube 10. The scintillator 8 is a phosphor that converts incident radiation into light (visible light). The scintillator 8 generates light (scintillator light) by causing the internal crystal to be in an excited state according to the dose of incident radiation. The scintillator 8 generates light corresponding to the incident radiation.

Here, a NaI (Tl) phosphor obtained by doping sodium iodide NaI with a small amount of thallium Tl is used as the scintillator 8. NaI (Tl) phosphors are useful because they have high sensitivity to gamma rays, have sufficient light emission, and can be obtained at a relatively low cost. In addition, as the scintillator 8, BGO [Bi ₄ Ge ₃ Ol ₂ ], GSO [Gd ₂ (SiO ₄ ) O], LSO [Lu ₂ (SiO ₄ ) O] or the like having a short decay time may be employed. In addition, the scintillator 8 has selected the column shape from a cost viewpoint, The diameter can be about 5 cm.

  The light guide 9 is a light transmission member that guides light generated by the scintillator 8 to the photomultiplier tube 10. The light guide 9 may be formed by processing a material that transmits light, such as acrylic resin, but may be configured by bundling a plurality of glass fibers, quartz fibers, or other fiber strands. The light guide 9 connects the lower end of the scintillator 8 and the upper end of the photomultiplier tube 10. Since the radiation detector 7 employs a photomultiplier tube 10 having a smaller diameter than the scintillator 8, the light guide 9 is formed in a funnel shape that tapers from the scintillator 8 toward the photomultiplier tube 10. ing.

  The photomultiplier tube 10 is an electronic device that outputs a signal corresponding to input light. When light enters the photocathode of the photomultiplier tube 10, photoelectrons are emitted from the photocathode, and the photoelectrons collide with the primary dynode to emit a plurality of secondary electrons. Thereafter, the secondary electrons are successively multiplied while being accelerated by the potential difference between the plurality of dynodes, and sent to the control unit 6 as a signal of sufficient output.

  Thus, the photomultiplier tube 10 transmits the detection of the radiation by the radiation detector 7 to the control unit 6 by changing the light generated in the scintillator 8 by the radiation emitted from the fish into an electrical signal. As the photomultiplier tube 10, a tube having a diameter smaller than that of the scintillator 8 can be adopted from the viewpoint of cost reduction. A photomultiplier tube 10 having the same diameter as that of the scintillator 8 may be used.

  A radiation shielding member 11 is provided so as to surround the lower side and the left and right sides of the radiation detector 7. The radiation shielding member 11 is a bowl-shaped lead member extending along the conveyance direction A, and a plurality of radiation detectors 7 are arranged at equal intervals therein. In addition, you may shield between the some radiation detectors 7 with a lead member, respectively. The bowl-shaped radiation shielding member 11 is disposed on a pedestal 12 that also extends along the transport direction A.

  The pedestal 12 includes a pair of left and right long members 12A and 12B having a U-shaped cross section, and a plurality of connecting rods 12C that connect the pair of left and right long members 12A and 12B at a central height. Yes. Two connecting rods 12 </ b> C are provided along the conveying direction A at predetermined intervals. A space is formed between the long members 12A and 12B having a U-shaped cross section, and the radiation detector 7 is located above the space. The pedestal 12 is supported by legs 13 provided at equal intervals in the transport direction A.

  The lower end of the photomultiplier tube 10 in the radiation detector 7 is exposed on the lower surface of the radiation shielding member 11 and is connected to the control unit 6 through a wiring (not shown). In order to prevent radiation from entering from the exposed portion, an auxiliary radiation shielding member 14 is provided below the photomultiplier tube 10. The radiation shielding member 14 is a plate-like lead member extending in the transport direction A so as to cover the lower ends of the plurality of photomultiplier tubes 10, for example. The radiation shielding member 14 is disposed on the leg portion 13 between the pair of left and right long members 12A and 12B constituting the base 12.

  In FIG. 4, the auxiliary radiation shielding member 14 is arranged on the leg portion 13, but the arrangement position is not limited to the leg portion 13. For example, the auxiliary radiation shielding member 14 may be arranged below the leg portion 13, It may be installed against the floor. The radiation detector 7 is surrounded by the radiation shielding member 11 and the radiation shielding member 14 on the lower side and the left and right sides.

  The radiation detector 7 is covered with a stainless steel cover 15 on the upper surface and both left and right sides. The stainless steel cover 15 is made of a stainless steel plate having a thickness of about 2 mm, for example, and is bent into a U-shape opened downward. The stainless steel cover 15 is disposed so as to cover the radiation detector 7 and the radiation shielding member 11 from above, and is provided extending in the transport direction A so as to cover all of the plurality of radiation detectors 7. That is, the radiation detector 7 detects the radiation of the fish through the stainless cover 15 and the belt of the belt conveyor 4.

  In addition, a pair of radiation shielding walls 16 and 17 that shield radiation are located on the left and right sides of the fish on the belt conveyor 4. The pair of radiation shielding walls 16, 17 are lead walls provided on the left and right sides of the belt conveyor 4 along the conveyance direction A, and are supported by a frame 18 provided so as to straddle the belt conveyor 4. . The radiation directed from the side toward the fish (and the radiation detector 7) is shielded by these radiation shielding walls 16 and 17.

  The fish is preferably arranged in the middle of the belt conveyor 4 in order to detect radiation with high accuracy. Although various methods can be considered as a method of arranging in the middle of the belt conveyor 4, a pair of guides may be provided on the left and right of the fish conveyed by the belt conveyor 4 as the simplest configuration. The pair of left and right guides are made of, for example, foamed polystyrene, and can be disposed inside the radiation shielding walls 16 and 17 in accordance with the width of the fish. By providing such a guide, when measuring live fish one by one, it is possible to prevent the fish from moving and changing position during measurement, and to improve measurement accuracy. In addition, by providing a connecting member that spans the pair of guides so that the pair of guides can be handled integrally, the guide can be easily attached to and detached from the system. However, it is necessary to prepare a guide that matches the width of the fish in advance.

  In addition, the radiation shielding walls 16 and 17 may be used as a guide. For example, the interval between the radiation shielding walls 16 and 17 may be configured to be adjustable, and the fish is arranged in the middle of the belt conveyor 4 by adjusting the interval between the radiation shielding walls 16 and 17 according to the width of the fish. Can do. It should be noted that the movable radiation shielding walls 16 and 17 whose distance can be adjusted need only be the entrance portion of the belt conveyor 4. Moreover, the structure which provides the sensor which detects the width | variety of a fish, and changes the radiation shielding walls 16 and 17 and the width | variety of a guide automatically may be sufficient.

  Next, FIG. 5 is a diagram showing the entire specific radioactivity inspection system including the building 20. The building 20 shown in FIG. 5 is devised to prevent radiation from entering from above the fish. Specifically, by using a material that does not contain a radioisotope that generates gamma rays as a building material on the ceiling side of the building 20, incidence of radiation from the ceiling can be prevented. Therefore, concrete concrete as a building material is not used because it contains potassium 40. Also, wood is not used because it contains potassium 40. The iron containing cobalt 60 is not used. Therefore, by using aluminum, copper, stainless steel, plastic, or iron that does not contain cobalt 60 as a material for the ceiling and side walls, which does not contain a radioisotope that generates gamma rays, It is possible to prevent radiation other than cosmic rays from entering. Thereby, the background by the radiation which comes from the building 20 is dropped, and the accuracy of the radiation detection of fish by the radiation detector 7 can be improved. The building 20 is not necessarily included in the specific radioactivity inspection system 1.

  Then, the test | inspection of the specific radioactivity of the fish in the control part 6 is demonstrated. The control unit 6 individually recognizes the fish according to the order of conveyance based on the individual marker data sent from the weight measuring table 3. The control unit 6 includes a number of energy spectrum data arrays. The control unit 6 labels the fish numbers in the order of transportation, assigns them to the data array of the numbers corresponding to the fishes, and stores data relating to the fishes.

  The controller 6 detects the position of the fish by position detection sensors 21, 22, and 23 provided at the entrance, middle, and exit of the belt conveyor 4, respectively. The position detection sensors 21, 22, and 23 detect whether or not the fish is passing through a predetermined installation position of each sensor. The control unit 6 recognizes the tip arrival time [N, ts1] and the end arrival time [N, tm1] of the Nth fish in the transport order based on the detection result of the entrance position detection sensor 21. In the case of the (N + 1) th fish, [N + 1, ts1] and end arrival time [N + 1, tm1] are obtained.

  Here, FIG. 6A is a diagram illustrating detection of the tip arrival time [N, ts1] in the Nth fish. FIG. 6B is a diagram illustrating detection of the end arrival time [N, tm1] in the Nth fish. As shown in FIG. 6 (a), the tip arrival time [N, ts1] of the Nth fish means the time when the tip of the Nth fish (for example, the tip of the head) is detected by the entrance position detection sensor 21. ing. Similarly, the end arrival time [N, tm1] of the N-th fish is the time when the end of the N-th fish (for example, the tail end) is detected by the entrance position detection sensor 21 (for example, the detection of the N-th fish by the laser is performed). It means the time when it was interrupted.

  The control unit 6 stores the tip arrival time [N, ts1] and the end arrival time [N, tm1] of the Nth fish in the entrance position detection sensor 21 in the fish data array. The control unit 6 knows the conveyance speed of the belt conveyor 4 and uses the fish tip arrival time [N, ts1] and terminal arrival time [N, tm1] to determine the position Z () of the Nth fish at time t ( N, t) is calculated.

  The control unit 6 acquires fish size (length) data by referring to the transport speed of the belt conveyor 4 at the fish tip arrival time [N, ts1] and the terminal arrival time [N, tm1]. May be. The detection result of the entrance position detection sensor 21 is also used as a start flag for fish radiation detection, and radiation detection by the radiation detector 7 is started at the same time when the first fish enters the belt conveyor 4.

  Further, the control unit 6 determines that the leading edge arrival time [N, ts2] and the terminal arrival time [N, tm2] in the intermediate position detection sensor 22, and the leading edge arrival time [N, tm3] and the terminal arrival time in the outlet position detection sensor 23. Based on [N, tm3], it is confirmed whether or not there is an error in the calculation result of the position of the fish.

  FIG. 7 is a diagram for explaining detection of radiation from fish. As shown in FIG. 7, each radiation detector 7 is connected to the control unit 6 via an amplifier 25 and an MCA [Multi-Channel Analyzer] 26. The control unit 6 stores the positions of the plurality of radiation detectors 7 as map data, and when a radiation detection signal is output from the Mth radiation detector 7 at the time t from the entrance of the belt conveyor 4, The position D (M) of the Mth radiation detector 7 is obtained from the map data, and the position of each fish at time t... Z (N−1, t), Z (N, t), Z (N + 1, t Compare with. The control unit 6 determines the fish whose position at time t is closest to the position D (M) of the Mth radiation detector 7 and counts it as radiation detection from the fish.

  Here, FIG. 8 is a diagram for explaining determination of a fish whose radiation has been detected by the control unit 6. As shown in FIG. 8, the control unit 6 specifically relates to the position Z (N, t) of the Nth fish, specifically, the tip position Z1 (N, t) and the end position Z2 (N, t) of the Nth fish. It is recognized as. The tip position Z1 (N, t) and the end position Z2 (N, t) of the Nth fish are, for example, the tip arrival time [N, ts1] and the tip arrival time [N, tm1] and the conveyance speed of the belt conveyor 4.

  When the control unit 6 receives a radiation detection signal from the Mth radiation detector 7 at time t in the state shown in FIG. 8, each position D (M) of the Mth radiation detector 7 and each of the time t Based on the position of the fish, the fish closest to the Mth radiation detector 7 is determined.

  Specifically, the control unit 6 determines that the position D (M) of the Mth radiation detector 7 is between the end position Z2 (N, t) of the Nth fish and the tip position Z1 (N + 1, t) of the N + 1th fish. And is closest to the end position Z2 (N, t) of the Nth fish. In this case, the control unit 6 determines that the fish closest to the position D (M) of the Mth radiation detector 7 is the Nth fish, and the signal received from the Mth radiation detector 7 is N Count as radiation detection from the second fish. The description of fish position recognition and determination by the control unit 6 described above is merely an example, and fish position recognition and determination may be performed by other methods.

  FIG. 9 is a diagram for explaining a case where the radiation detector 7 located at the same distance from the front and rear fishes detects the radiation. As shown in FIG. 9, the control unit 6 determines that the position D (M) of the Mth radiation detector 7 that has detected radiation is the end position Z2 (N, t) of the Nth fish and the tip position of the N + 1th fish. When it is determined that they are equidistant from Z1 (N + 1, t), the fish orientation data obtained from the weight measuring table 3 is considered. The control unit 6 determines the N + 1 fish whose head is close to the Mth radiation detector 7 among the Nth fish and N + 1th fish located at the same distance as the closest fish, and the radiation of the N + 1th fish. Count as detection. Note that the equidistant determination is not limited to a strict one but includes an error of several millimeters or several centimeters.

  Further, even if the fish orientation data is not acquired by the weight measuring table 3 or the like, if the fish orientation is unified by manual work or the like, the fish orientation data is uniformly distributed to the control unit 6 in advance. By making this setting, the same determination can be made.

  Considering that the detection sensitivity of the gamma rays is inversely proportional to the square of the distance between the radiation source and the radiation detector 7 with respect to the interval between the fish to be conveyed, as shown in FIG. By setting the distance of one diameter, radiation from a plurality of fish is prevented from being detected in a mixed manner. For large fish, as shown in FIG. 8, it is preferable to place a distance corresponding to two diameters of the radiation detector 7 between the fish.

  In this way, the radiation detection of the Nth fish is counted, and the energy spectrum of the fish shown in FIG. 10 is acquired. When the radiation detection of the Nth fish is completed (for example, when the Nth fish passes in front of the exit position detection sensor 23), the total lane count is calculated for the Nth fish. Thereafter, the radioactivity Bq of the Nth fish is obtained by calculation excluding the influence of the background. The control unit 6 calculates the specific activity Bq / kg of the Nth fish by dividing the activity Bq by the weight kg.

  Moreover, the control part 6 controls the sorter (sorting means) 5 and sorts fish. The sorter 5 is a three-way sorting conveyor for sorting fish into three according to specific radioactivity. The sorter 5 includes switching valves 30 and 31 for switching the course of the fish. By changing the positions of the switching valves 30 and 31, the fish are sorted by specific activity. The control unit 6 separates the fish having a specific activity of 20 Bq / kg or less, the fish having a specific activity of more than 20 Bq / kg and not more than 100 Bq / kg, and a fish having a specific activity of more than 100 Bq / kg.

  Then, the effect of the fish specific radioactivity test | inspection system 1 which concerns on this embodiment is demonstrated.

  According to the specific radioactivity inspection system 1 for fish according to the present embodiment, a plurality of radiation detectors 7 are arranged along the conveyance direction A, and the radiation of the fish is detected while being conveyed thereon, thereby the same time as the conveyance time. It is possible to obtain the same detection result as when the radiation of fish is individually detected by applying, and to continuously inspect the whole fish without processing the fish.

  Moreover, in this specific activity inspection system 1, the individual labeling and weight measurement of a plurality of fish arranged in a line are performed, and the specific activity Bq obtained from the radiation detection result is divided by the weight kg of the fish to obtain the specific activity. Since Bq / kg can be obtained, it is possible to efficiently classify fish according to specific radioactivity. Moreover, according to the specific radioactivity inspection system 1, the radiation shielding members 11 and 14 surrounding the radiation detector 7 are located below the fish, and the pair of radiation shielding walls 16 and 17 are located on the left and right of the fish. Since the radiation from the concrete floor to the fish can be shielded, the radiation detection background can be reduced and the radiation from the fish can be detected with high accuracy.

  Moreover, according to this specific radioactivity test | inspection system 1, it can also make monitoring of a fish conveyance state, troubleshooting, and maintenance easy by opening the upper direction of the fish to be conveyed. Furthermore, according to this specific radioactivity inspection system 1, since the radiation detector 7 is located below the fish, the fish can be detected regardless of the size of the fish as compared with the case where the radiation detector 7 is located above or to the side of the fish. And the radiation detector 7 can be minimized, and the accuracy of radiation detection can be improved. As described above, according to the specific radioactivity inspection system 1, it is possible to inspect the specific radioactivity continuously and efficiently, and to classify the fish according to specific radioactivity with high accuracy. Therefore, according to the specific radioactivity inspection system 1, since the whole fish is inspected individually, it is possible to give the consumer a greater security and damage the fish compared to the case where a plurality of fish are inspected together. By inspecting the whole thing continuously, it is possible to motivate producers and contribute to the reconstruction of fishing ports.

  Moreover, according to this specific radioactivity inspection system 1, by providing the stainless steel cover which covers the upper side and the left and right sides of the plurality of radiation detectors 7, it is possible to appropriately protect the radiation detectors 7 and improve the durability of the equipment. At the same time, it can cope with frequent washing to maintain hygiene and is useful as a fish inspection system.

  Further, according to the specific radioactivity inspection system 1, the control unit 6 recognizes the fish tip arrival time and the terminal arrival time by the position detection sensors 21 to 23, and uses the conveyance speed of the belt conveyor 4 to determine the position of each individual fish. Since it is possible to recognize the position of the fish with a simple configuration, it is possible to easily grasp the position of individual fish based on the conveyance speed without performing detailed position detection, The result of radiation detection can be appropriately counted as the detection result of individual fish. This is advantageous for simplifying the system configuration and reducing the manufacturing cost of the system.

  Moreover, according to this specific radioactivity inspection system 1, when it is determined that the radiation detector at the same distance from the front and rear fish has detected radiation, the radiation detection of the fish whose head is close to the radiation detector is counted. . In this way, considering the fish structure, there is a higher possibility of detecting radiation from the head than the fish tail, so misdetection is avoided by counting as radiation detection of fish that is near the head among equidistant fish. The reliability of radiation detection can be improved.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above-described embodiment. Here, FIG. 11A is a plan view showing the radiation detector 40 according to the first modification, and FIG. 11B is a side view showing the radiation detector 40 according to the first modification. .

  As shown in FIGS. 11A and 11B, the radiation detector 40 according to the first modification includes a circular scintillator 41, a light guide 42, and a photomultiplier tube 43. A radiation shielding member 44 is provided between the radiation detectors 40.

  The radiation detector 40 according to the first modified example is arranged so that the scintillator 41 and the photomultiplier tube 43 do not overlap each other when viewed from the vertical direction as shown in FIG. For this reason, the light guide 42 is formed in an obliquely deformed funnel shape, and connects the scintillator 41 and the photomultiplier tube 43 located obliquely below the scintillator 41.

  According to the radiation detector 40 configured in this way, as compared with the conventional case where the scintillator and the photomultiplier tube are arranged in series (vertical), as shown in FIG. Gamma rays entering from below 43 do not reach the scintillator 41, and the background caused by gamma rays from the ground can be greatly reduced. Furthermore, if the diameter of the photomultiplier tube 43 is reduced, the background can be further reduced. Therefore, according to the specific activity inspection system provided with the radiation detector 40 according to the second modification, the radiation background can be reduced, so that the reliability of the radiation detection of fish can be improved.

  When the scintillator 41 and the photomultiplier tube 43 are arranged so as not to overlap each other when viewed from the vertical direction as in the radiation detector 40 according to the first modification, the auxiliary is provided below the photomultiplier tube 43. There is no need to provide a radiation shielding member (radiation shielding member 14 in FIG. 4).

  Subsequently, a radiation detector 50 according to a second modification will be described. FIG. 12A is a plan view showing a radiation detector 50 according to the second modification, and FIG. 12B is a side view showing the radiation detector 50 according to the second modification.

  As shown in FIGS. 12A and 12B, the radiation detector 50 according to the second modified example is composed of two scintillators 51 and 52, a light guide 53, and a photomultiplier tube. In addition, the radiation shielding member 55 covers the portions other than the upper surfaces of the scintillators 51 and 52 and the lower surface of the photomultiplier tube 54.

  In the radiation detector 50 according to the second modification, one photomultiplier tube 54 is provided for the two scintillators 51 and 52. That is, the light guide 53 connects the lower surfaces of the two scintillators 51 and 52 and the upper surface of one photomultiplier tube 54. Also in the radiation detector 50, as shown in FIG. 12A, the two scintillators 51 and 52 and the one photomultiplier tube 54 are arranged so as not to overlap each other when viewed from the vertical direction.

  According to the radiation detector 50 configured in this way, the number of required photomultiplier tubes 54 can be reduced, so that the manufacturing cost of the system can be greatly reduced. Also, as shown in FIG. 12B, in this radiation detector 50 as well, gamma rays entering from below the photomultiplier tube 43 can be prevented from reaching the scintillators 51 and 52, so that gamma rays from the ground cause The background can be greatly reduced.

  FIG. 13 is a view showing a radiation detector 60 according to a third modification. As shown in FIG. 13, in the radiation detector 60 according to the third modification, a scintillator 61 and a small-diameter photomultiplier tube 63 are connected in the vertical direction via a light guide 62. In this radiation detector 60, a cylindrical lead shield (radiation) having a diameter larger than the diameter of the photomultiplier tube 63 is used so that the scintillator 61 is not directly seen through the photomultiplier tube 63 from below. A shielding member) 65 is placed. The cylindrical lead shield 65 is arranged as close as possible to the hole of the upper radiation shielding member 64 (the hole where the lower end of the photomultiplier tube 63 is exposed). Thereby, the background by the gamma ray from the ground can be made low. Note that if the diameter of the photomultiplier tube 63 is made smaller, the background can be further reduced.

  In the above-described embodiment, the individual marking of fish is performed on the weight measuring table 3, but the method of individual marking is not limited to that described above. For example, fish individual signs (for example, individual signs based on the order of conveyance) may be performed when the position is detected by the entrance position detection sensor 21.

  DESCRIPTION OF SYMBOLS 1 ... Specific radioactivity inspection system 2 ... Slope stand 2a ... Belt conveyor (exit) 3 ... Weight measuring stand (weight measuring means, individual labeling means) 4 ... Belt conveyor (conveying means) 5 ... Sorting machine (sorting means) 6 ... Control unit (calculation means) 7, 40, 50 ... Radiation detector 8, 41, 51, 52 ... Scintillator 9, 42, 53 ... Light guide 10, 43, 54 ... Photomultiplier tube 11, 14, 44 ... Radiation shielding Member 12 ... Base 13 ... Leg 15 ... Stainless steel cover 16, 17 ... Radiation shielding wall 18 ... Frame body 20 ... Building 21 ... Entrance position detection sensor 22 ... Intermediate position detection sensor 23 ... Exit position detection sensor 25 ... Amplifier 26 ... MCA 30, 31 ... switching valve

Claims (8)

A specific radioactivity inspection system for inspecting the specific activity of a plurality of fish,
Individual marking means for individually marking a plurality of fish,
A weight measuring means for individually weighing a plurality of fish;
Transport means for transporting a plurality of fish in a line in a predetermined transport direction;
A plurality of radiation detectors positioned below the plurality of fish transported by the transport means and provided side by side in the transport direction;
A pair of radiation shielding walls located on the left and right of the plurality of fish whose radiation is detected by the radiation detector, and provided along the transport direction;
A radiation shielding member provided to surround the lower side and the left and right sides of the radiation detector;
Calculation means for individually calculating the specific activity of the fish based on the individual label information of the individual marker means, the weight measurement result of the weight measurement means, and the radiation detection results of the plurality of radiation detectors;
Sorting means for sorting the fish based on the calculation result of the specific activity of the fish by the calculating means;
A specific radioactivity inspection system for fish, comprising:   The specific radioactivity inspection system for fish according to claim 1, further comprising a stainless steel cover covering at least upper surfaces of the plurality of radiation detectors. The arithmetic means has a position detection sensor for detecting whether or not the fish is passing through a predetermined position in the transport means,
The specific radioactivity inspection system for fish according to claim 1 or 2, wherein the calculation means recognizes the tip arrival time and the end arrival time of the fish based on a detection result of the position detection sensor. The calculation means recognizes the position of the individual fish based on the individual sign information of the individual sign means and the conveyance speed of the conveyance means,
The specific radioactivity inspection system for fish according to any one of claims 1 to 3, wherein when the radiation detector detects radiation, it counts as radiation detection for a fish located closest to the radiation detector.   5. The calculation unit according to claim 1, wherein, when it is determined that the radiation detector at a position equidistant from the preceding and following fish has detected radiation, the calculation means counts as radiation detection of fish whose head is close to the radiation detector. The specific radioactivity inspection system for fish according to any one of the above.   The specific radioactivity inspection system for fish according to any one of claims 1 to 5, further comprising a pair of guides arranged on the left and right of the fish being transported by the transport means. The radiation detector has a scintillator that emits light upon incidence of radiation, a light guide that transmits light generated by the scintillator, and a photomultiplier tube that outputs a signal according to light input through the light guide,
The specific radioactivity inspection system for fish according to any one of claims 1 to 6, wherein the scintillator and the photomultiplier tube are arranged so as not to overlap each other when viewed from the vertical direction.   The said light guide is a specific radioactivity inspection system of the fish of Claim 7 which has connected the said some scintillator with respect to one photomultiplier tube.

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