JP6485090B2 - Radioactivity measuring device - Google Patents

Description

  The present invention relates to a radioactivity measuring apparatus that measures the radioactivity concentration of waste dust discharged from an incineration facility or the like.

  Conventionally, a radioactivity measuring device that collects waste dust in exhaust gas (high-temperature gas) discharged from an incineration facility and measures the radioactivity concentration of the waste dust is known (see, for example, Patent Document 1). The radioactivity measuring apparatus described in Patent Document 1 is such that a collection block on which filter paper is installed is installed on the lower side of the apparatus chamber, and is opposed to the collection block at a predetermined interval in the vertical direction. A detector is suspended above the chamber. Waste dust is collected by the exhaust gas in the collection block passing through the filter paper, and the radiation from the waste dust passes through the outer wall of the collection block and is detected by the detector.

  At this time, high-temperature exhaust is drawn from the incineration facility to the collection block through the intake pipe, but the detector is floating with respect to the collection block, so that heat is not directly transmitted from the collection block to the detector. . The air between the collection block and the detector is warmed by the hot air from the collection block, but because the cooling air is blown to the detector, the warmed air is replaced by the cooling air, No heat is generated between the detectors. Thus, sufficient measurement accuracy of the radioactivity concentration is secured by detecting the detector close to the collection block while suppressing the temperature rise of the detector.

JP-A-9-197049

  However, in the radioactivity measurement apparatus described in Patent Document 1, the detector is placed at a short distance from the collection block, so that the thermal conditions of the detector are severe. In addition, when the radioactivity measuring apparatus is assembled, it is difficult to position the detector suspended from the apparatus chamber, which causes problems that the assembling work becomes complicated and the cost increases.

  The present invention has been made in view of such a point, and provides a radioactivity measurement apparatus capable of measuring the radioactivity concentration of waste dust with a simple and inexpensive configuration while keeping the detector within an allowable temperature. With the goal.

The radioactivity measurement apparatus of the present invention is a radioactivity measurement apparatus for measuring the radioactivity concentration of waste dust contained in exhaust gas, and a collection block in which a collection space for collecting waste dust from exhaust gas is formed; , A detector arranged to detect radiation from waste dust below the collection block, a heat insulating material interposed between the collection block and the detector, and collection of the collection block A heater interposed between the collecting block and the heat insulating material so as to heat the space is provided, and the collecting block contacts the detector via the heat insulating material.

According to this configuration, since the heat from the collection block tends to go upward, the thermal condition of the detector located below the collection block can be relaxed. In addition, since the detector is installed below the collection block when the radioactivity measuring apparatus is assembled, the assembling work can be simplified and the cost can be reduced as compared with the configuration in which the detector is suspended from above. Moreover, since the heat from the collection block is insulated by the heat insulating material, the temperature of the detector does not rise greatly even if the detector is brought closer to the collection block. Therefore, the detection accuracy of radiation by the detector can be increased. Furthermore, the temperature drop of the exhaust gas in the collecting block can be suppressed, and the generation of corrosive gas can be suppressed. Further, since the heat of the heater is insulated by the heat insulating material, the temperature of the detector does not increase greatly even if the detector is brought closer to the heater. Therefore, generation | occurrence | production of corrosive gas can be suppressed in a collection block, and the detection accuracy of a radiation can be improved in a detector.

  Moreover, the said radioactivity measuring apparatus of this invention WHEREIN: The said heat insulating material and the said heater are formed in flat form or a sheet form. According to this configuration, the collection block and the detector can be brought close to each other in a state where the collection block is heated and heat insulation is ensured, and the detection accuracy of radiation by the detector can be improved.

  The radioactivity measurement apparatus according to the present invention further includes a cooling jacket that forms a cooling path between the collection block and the detector, and a detector cap that is attached to the detector inside the cooling jacket. The detector cap has a convex portion that abuts against the inner surface of the cooling jacket and forms a cooling path between the inner surface of the cooling jacket and the outer surface of the detector. According to this configuration, the detector with respect to the cooling jacket can be easily positioned by abutting the convex portion of the detector cap against the inner surface of the cooling jacket. Moreover, since the heat from the collection block is cooled by the cooling path between the collection block and the detector, an increase in the temperature of the detector is suppressed.

  In the radioactivity measurement apparatus of the present invention, the cooling jacket includes an upstream cooling path for cooling the outer surface of the detector, and a downstream cooling path for cooling between the collection block and the detector. Are formed, and the upstream cooling path and the downstream cooling path communicate with each other on a center line extending vertically through the detector. According to this configuration, the outer surface of the detector is cooled by the fluid in the cooling path on the upstream side, and this fluid flows through the cooling path on the downstream side, thereby cooling the heat from the collection block toward the detector. Therefore, the detector in the cooling jacket can always be kept below the allowable temperature.

  Further, in the radioactivity measuring device of the present invention, in the collection space of the collection block, exhaust dust is collected from the exhaust by the filter paper as exhaust gas is drawn from above toward the filter paper, and the filter paper Radiation from the waste dust accumulated on the upper surface is detected from the back side of the filter paper by the detector. According to this structure, the radiation which permeate | transmitted the filter paper from the waste dust can be detected from the lower side by the detector. Moreover, since exhaust dust passes through the filter paper from above and waste dust accumulates on the upper surface of the filter paper, the exhaust dust is not scattered within the collection block.

  In the radioactivity measurement apparatus of the present invention, the collection block includes an inlet channel that draws exhaust gas into the collection space, and an outlet flow that exhausts the exhaust gas from the collection space on the side of the inlet channel. A path, and a circular flat channel that is eccentric toward the outlet channel so as to connect the collection space and the outlet channel are formed. According to this configuration, the exhaust drawn into the collection space spreads in the circular flat flow path, but a smooth exhaust flow is created by the flat flow path being eccentric toward the outlet flow path. Since there is no place where the flow of high-temperature exhaust gas is small in the circular flat flow path, the temperature in the flat flow path does not partially drop. Therefore, the temperature drop in the flat flow path can be suppressed and the generation of corrosive gas can be prevented.

  In the radioactivity measurement apparatus of the present invention, the collection block is formed with a notch to which a filter paper holder holding the filter paper can be attached, and the notch sandwiches the collection space. It is notched inward from the outer peripheral position facing the outlet channel. According to this configuration, the portion where the temperature is lowered by the notch can be separated from the outlet channel, and the temperature drop in the outlet channel can be suppressed.

  According to the present invention, by disposing the detector below the collection block, the thermal conditions of the detector can be eased and the assembly work of the radioactivity measuring apparatus can be simplified. Therefore, the radioactive concentration of waste dust can be measured with a simple and inexpensive configuration while keeping the detector within the allowable temperature.

It is a perspective view of the radioactivity measuring apparatus which concerns on this Embodiment. It is sectional drawing of the radioactivity measuring apparatus of FIG. It is explanatory drawing of the collection block which concerns on this Embodiment. It is explanatory drawing of the detector which concerns on this Embodiment. It is explanatory drawing of the detection operation of the radiation by the detector which concerns on this Embodiment. It is a heat distribution figure of the radioactivity measuring apparatus which concerns on this Embodiment. It is a relationship diagram between the distance from the detector surface and the temperature according to the present embodiment.

  Hereinafter, the radioactivity measurement apparatus according to the present embodiment will be described with reference to the accompanying drawings. FIG. 1 is a perspective view of the radioactivity measuring apparatus according to the present embodiment. FIG. 2 is a cross-sectional view of the radioactivity measurement apparatus of FIG. Note that the radioactivity measurement apparatus is not limited to the configuration shown in FIGS. 1 and 2. The radioactivity measurement apparatus shown in FIGS. 1 and 2 is only an example, and can be changed as appropriate.

  As shown in FIG. 1A and FIG. 1B, the radioactivity measurement apparatus 1 according to the present embodiment extracts a part of the exhaust gas (hot gas) discharged from the chimney 2 (see FIG. 2) of the incineration facility. It is configured to measure the concentration of contained radioactive material. The frame 10 of the radioactivity measuring apparatus 1 has a four-leg frame structure made of stainless steel (for example, SUS304), and upper and lower two-stage installation portions 11 and 12 are formed inside. The upper installation section 11 is provided with a collection block 20 that collects waste dust in the exhaust from the chimney 2 of the incineration facility, and the lower installation section 12 detects radiation from the radioactive material contained in the waste dust. A detector 40 is installed.

  A rectangular frame-shaped support plate 13 is formed on the frame 10 so as to surround the four legs between the upper and lower installation portions 11 and 12. In the upper installation section 11, the collection block 20 is covered by a box-shaped lead shield 14 installed on the support plate 13, and in the lower installation section 11, the periphery of the detector 40 is covered by a hollow cylindrical lead shield 15. ing. The radiation accuracy from the outside is shielded by the lead shields 14 and 15, so that the detection accuracy by the detector 40 is improved. In addition, an exhaust pipe 37 and an exhaust pipe 38 for exhaust are connected to the collection block 20, and an intake pipe 63 and an exhaust pipe 64 for instrument air are connected to the cooling jacket 50 attached to the detector 40. Yes.

  As shown in FIG. 2, the sampling nozzle 4 protrudes on the downstream side (the upper side in the drawing) of the chimney 2, and the high-temperature exhaust gas taken in by the sampling nozzle 4 is sent to the collection block 20 through the intake pipe 37. The collection block 20 is formed with a collection space 27 for collecting waste dust from the exhaust gas by the filter paper 26. The filter paper 26 is attached to a filter paper holder 25 that can be attached to and detached from the collection block 20. By attaching the filter paper holder 25 to the collection block 20, the collection space 27 is formed in the collection block 20 and the filter paper 26 is set in the collection space 27. As the exhaust gas passes through the filter paper 26, the waste dust in the exhaust gas is collected by the filter paper 26 and deposited on the upper surface.

  An exhaust pipe 38 is connected to the upstream side (the lower side in the figure) of the chimney 2, and the exhaust gas that has passed through the filter paper 26 is returned to the chimney 2 from the collection block 20 through the exhaust pipe 38. In addition, when the exhaust gas is cooled, corrosive gases such as nitrogen oxides NOx and sulfur oxides SOx are generated and the piping and equipment are deteriorated. . In this case, a flat plate-like heater 70 is attached to the lower surface of the collection block 20, and the collection space 27 is heated. Further, a belt-like heater 71 is attached to the outer peripheral surface of the collection block 20 so that the collection block 20 is heated from the outside.

  A detector 40 is arranged below the collection block 20 so as to face the filter paper 26. The detector 40 detects radiation (mainly γ rays) from radioactive substances contained in the waste dust on the upper surface of the filter paper 26. The detector 40 is equipped with a cooling jacket 50 that forms a cooling path around the detector 40. Instrument air is supplied to the cooling jacket 50 through the intake pipe 63 to cool the detector 40, and the cooled instrument air is discharged from the cooling jacket 50 through the exhaust pipe 64. The surface temperature of the detector 40 is kept at an allowable temperature of 40 ° C. or lower by instrument air flowing in the cooling jacket 50.

  Between the collection block 20 and the detector 40, a flat heat insulating material 75 such as silicon sponge is interposed. The heat insulating material 75 is disposed on the lower surface of the heater 70, and heat from the collection block 20 and the heater 70 is insulated by the heat insulating material 75, and the temperature rise of the detector 40 is suppressed. By providing the heat insulating material 75 between the collection block 20 and the detector 40, the collection block 20 can be heated by the heater 70, while the detector 40 can be suppressed to an allowable temperature by the cooling jacket 50. Yes. Further, since the heater 70 and the heat insulating material 75 are formed in a flat plate shape, the detection accuracy of the radiation is improved by bringing the detector 40 closer to the filter paper 26.

  In addition, the radioactivity measuring apparatus 1 is provided with a control unit (not shown) that controls each part of the apparatus. The controller adjusts the flow rate of exhaust gas, adjusts the flow rate of instrument air, adjusts the temperature of the heaters 70 and 71, and measures the radioactivity concentration based on the detection result of the detector 40. The control unit is configured by a processor, a memory, and the like that execute various processes. The memory is composed of one or a plurality of storage media such as a ROM (Read Only Memory) and a RAM (Random Access Memory) depending on the application. In the present embodiment, stable instrument air is used for cooling the detector 40, but cooling air from a cooling fan may be used for cooling the detector 40.

  By the way, in the general radioactivity measurement apparatus, unlike the radioactivity measurement apparatus 1 which concerns on this Embodiment, the detector is attached above the collection block. This is because the waste dust is deposited on the upper surface of the filter paper so that the dust is not scattered in the collection block, and it is necessary to bring the detector closer to the waste dust from the upper side in order to improve detection accuracy. is there. However, since the hot air from the collecting block tends to move upward, the thermal conditions of the detector are severe. Here, when the present inventors detected the radiation of waste dust with a detector from the back side of the filter paper, it was discovered that sufficient detection accuracy could be obtained even from the back side of the filter paper.

  Therefore, in the radioactivity measurement apparatus 1 according to the present embodiment, the detector 40 is disposed below the collection block 20 to relax the thermal conditions of the detector 40. In addition, by installing the detector 40 below the collection block 20, the assembly work can be simplified and the cost can be reduced as compared with the configuration in which the detector 40 is suspended from above when the radioactivity measurement apparatus 1 is assembled. Is possible. Further, the collection block 20 is in contact with the detector 40 via the heat insulating material 75. For this reason, the height position of the filter paper 26 from the detector 40 can be easily positioned based on the contact surface of the detector 40 during assembly.

  With reference to FIG.3 and FIG.4, a collection block and a detector are demonstrated in detail. FIG. 3 is an explanatory diagram of the collection block according to the present embodiment. FIG. 4 is an explanatory diagram of the detector according to the present embodiment. 3A is a perspective view of the collection block, FIG. 3B is a sectional view of FIG. 3A, and FIG. 3C is a perspective view of the internal flow path of the collection block. 4A is a cross-sectional perspective view of the detector and the cooling jacket, and FIG. 4B is a perspective view of the detector upper portion and the detector cap.

  As shown in FIG. 3A, the collection block 20 is made of stainless steel (for example, SUS304) having high corrosion resistance, and has a substantially cylindrical block body 21 partially cut away from the outer periphery toward the center. Yes. A filter paper holder 25 can be attached to the notch 22 of the block main body 21, and the filter paper 26 (see FIG. 3B) is inserted into the collecting block 20 by inserting the tip end side of the filter paper holder 25 from the notch 22 toward the center of the block main body 21. ) Is set. A joint 23 connected to an intake pipe 37 (see FIG. 1) is provided at the center of the block main body 21. This collection block 20 is installed on a base member 24 formed in a plate shape with PEEK material.

  As shown in FIG. 3B, an annular holding portion 28 that holds the filter paper 26 is formed on the tip side of the filter paper holder 25. The inside of the holding part 28 is opened, and the filter paper 26 is horizontally installed on the holding part 28 so as to close the opening. The opening of the filter paper holder 25 forms a collection space 27 for collecting waste dust with the filter paper 26 in the collection block 20. The joint 23 is formed with an inlet channel 31 that draws exhaust gas into the collection space 27, and the block body 21 is formed with an outlet channel 32 that discharges exhaust gas from the collection space 27 at the side of the inlet channel 31. Has been. In addition, a circular flat channel 33 that connects the collection space 27 and the outlet channel 32 is formed on the lower surface side of the block body 21.

  A depression 34 is formed on the lower surface of the block main body 21, and an installation space 39 in which the heater 70 and the heat insulating material 75 are installed is formed by the depression 34 and the opening of the base member 24. A heater 70 is installed in the installation space 39 so as to be interposed between the block main body 21 and the heat insulating material 75, and the collection space 27 of the block main body 21 is heated by the heater 70. In this case, since the bottom wall of the block main body 21 is formed to be thin (for example, 1 mm) by the amount of the depression 34, the flow path of the collection block 20 can be effectively heated by the heater 70. . A tape-like heater 71 is also wound around the outer peripheral surface of the block main body 21.

  Although the block main body 21 is heated from the outer peripheral side by the heater 71, the portion of the block main body 21 where the notch 22 is formed is not heated. That is, the temperature of the filter paper holder 25 decreases toward the base end side away from the center of the block main body 21. As shown by a two-dot chain line in FIG. 3C, if a circular flat flow channel 35 is formed concentrically with the inlet flow channel 31, the exhaust drawn into the collection space 27 spreads into the flat flow channel 35. However, the flow of the high-temperature exhaust gas becomes worse near the position P away from the outlet flow path 32. Further, since the vicinity of the position P is the base end side of the filter paper holder 25 that is not heated by the heater 71, the temperature of the exhaust gas may be lowered and corrosive gas may be generated.

  Therefore, in the present embodiment, as shown by the solid line in FIG. 3C, the flat flow path 33 of the block body 21 is formed eccentrically toward the outlet flow path 32 so as to connect the collection space 27 and the outlet flow path 32. Yes. A smooth exhaust flow is created by the circular flat channel 33 being eccentric toward the outlet channel 32. Since there is no place where the flow of exhaust gas is small in the circular flat flow path 33, the temperature in the flat flow path 33 does not partially decrease. Moreover, since the flat flow path 33 is formed avoiding the vicinity of the position P where the temperature tends to decrease, the temperature of the exhaust gas in the flat flow path 33 is difficult to decrease. Thus, the temperature drop in the flat flow path 33 is suppressed and the generation of corrosive gas is prevented.

  3A and 3C, the notch 22 of the block main body 21 is notched inward from the outer peripheral position facing the outlet flow path 32 with the collection space 27 interposed therebetween. With this configuration, the vicinity of the position P where the temperature is likely to decrease due to the above-described notch 22 can be separated from the outlet channel 32, and the temperature decrease in the outlet channel 32 is suppressed. Details of the heat distribution of the collection block 20 will be described later.

  As shown in FIG. 4A, the detector 40 has a cylindrical exterior made of Duracon (registered trademark) (POM: Polyoxymethylene), and is configured to detect radiation from radioactive substances contained in waste dust. Has been. A stainless steel (for example, SUS304) cooling jacket 50 is attached to the detector 40 so as to leave a gap around the detector 40. Below the cooling jacket 50 is a thick base 51 in which a rectangular flange 52 is formed. By installing the flange 52 of the base part 51 in the installation part 12 (see FIG. 1) of the frame 10, the detector 40 is erected below the collection block 20.

  On the outer peripheral surface of the base portion 51, an inlet channel 61 for drawing cooling instrument air around the detector 40 is provided. The lower surface of the base 51 is opened so that the detector 40 can be accommodated in the cooling jacket 50, and a detector presser 65 made of resin (for example, MC nylon (registered trademark)) is attached to the opening for detection. The container 40 is prevented from coming off. The detector presser 65 abuts on the outer peripheral surface of the detector 40 and also contacts the inner peripheral surface of the base portion 51, so that not only the gap between the cooling jacket 50 and the detector 40 is sealed, but also the cooling jacket. The detector 40 is positioned at the center of 50. Above the base 51 of the cooling jacket 50 is a thin inner cylinder 53 that covers the detector 40.

  The upper part of the cooling jacket 50 has a double structure in which a thin outer cylinder part 54 is formed outside the inner cylinder part 53. A cooling path 55 (upstream cooling path) for cooling the outer surface of the detector 40 is formed by the inner cylinder portion 53, and the space between the collection block 20 (see FIG. 5A) and the detector 40 is cooled by the outer cylinder portion 54. A cooling path 56 (downstream cooling path) is formed. An opening is formed in the center of the upper surface of the inner cylinder portion 53, and the upper and lower cooling paths 55 and 56 are communicated with each other on the center line passing through the detector 40 vertically. Further, the outer cylinder portion 54 is provided with an outlet flow path 62 for discharging the instrument air for cooling the detector 40 from the cooling path 56.

  As shown in FIGS. 4A and 4B, a detector cap 45 made of resin (for example, polyvinyl chloride) is attached to the upper portion of the detector 40. The detector cap 45 has a bottomed cylindrical shape having an upper bottom, and is provided with convex portions 48 protruding outward from the cap peripheral surface 46 and protruding upward from the cap upper surface 47 at four locations on the outer peripheral portion. The upper surface of each convex portion 48 protrudes from the cap upper surface 47 by a desired width of the cooling path 55, and the side surface of the convex portion 48 protrudes from the cap peripheral surface 46 by the gap between the inner cylinder portion 53 and the cap peripheral surface 46. When each convex portion 48 abuts against the inner surface of the inner cylinder portion 53, the detector 40 is positioned on the cooling jacket 50, and a cooling path 55 is formed between the inner cylinder portion 53 and the detector 40.

  As described above, the detector cap 45 is attached to the upper portion of the detector 40 and pushed into the cooling jacket 50, whereby the detector 40 can be easily positioned in the cooling jacket 50. Therefore, the assembly work of the detector 40 with respect to the cooling jacket 50 can be simplified. The convex portion 48 is formed to a size that does not hinder the flow of instrument air in the cooling passage 55, and does not adversely affect the cooling effect in the cooling jacket 50. In addition, each convex part 48 should just be provided in the cooling jacket 50 so that the detector 40 can be positioned, and is not limited to the structure provided at equal intervals in the circumferential direction as shown to FIG. 4B.

  The radiation detection operation by the detector will be described with reference to FIG. FIG. 5 is an explanatory diagram of the radiation detection operation by the detector according to the present embodiment. FIG. 5A shows the detection state of radiation by the detector, and FIG. 5B shows the cooling state of the detector.

  As shown in FIG. 5A, exhaust gas is drawn into the collection space 27 of the collection block 20 from above by the inlet channel 31, and waste dust D is discharged from the exhaust by the filter paper 26 installed horizontally in the collection space 27. It is collected. Thereby, the waste dust D is accumulated on the filter paper 26, and radiation is emitted from the radioactive material contained in the waste dust D. The detector 40 is disposed below the collection block 20 so as to face the filter paper 26, and the radiation from the waste dust D on the filter paper 26 is detected from the back side of the filter paper 26 by the detector 40. Thus, the radiation emitted from the waste dust D and transmitted through the filter paper 26 is detected by the detector 40.

In this case, a heater 70, a heat insulating material 75, a cooling jacket 50, and a detector cap 45 are interposed between the filter paper 26 and the detector 40. The nuclide to be measured is ¹³⁷ Cs or the like, and γ rays are detected. In this case, gamma rays that have passed through these inclusions can be detected by the detector 40. In addition, since these inclusions are formed to be thin, the distance between the waste dust D deposited on the filter paper 26 and the detector 40 can be reduced, and the detection accuracy is improved. When radiation is detected by the detector 40, the detection result is output from the detector 40 to a control unit (not shown), and the control unit measures the radioactivity concentration based on the detection result.

  The exhaust gas that has passed through the filter paper 26 is discharged from the outlet channel 32 through the flat channel 33 while warming the channel in the collection block 20. A plate-like heater 70 is interposed between the collecting block 20 and the heat insulating material 75 in order to suppress the temperature drop of the exhaust, and the collecting space 27 of the collecting block 20 is heated by the heater 70. In this case, since the heat of the heater 70 is insulated by the heat insulating material 75, the temperature rise of the detector 40 due to the heat of the heater 70 is suppressed. Thus, by interposing the heat insulating material 75 between the heater 70 and the detector 40, the temperature rise of the detector 40 is suppressed without moving the detector 40 away from the filter paper 26. Therefore, the collection block 20 can be heated by the heater 70 in a state where sufficient detection accuracy is secured in the detector 40.

  As shown in FIGS. 5A and 5B, a cooling jacket 50 is attached to the detector 40, and a flow path is formed around the detector 40 by the cooling jacket 50. As described above, the cooling path 55 for cooling the outer surface of the detector 40 is formed by the inner cylinder portion 53 of the cooling jacket 50, and the cooling path 56 for cooling the space between the detector 40 and the collection block 20 by the outer cylinder portion 54. Is formed. When instrument air is drawn into the cooling path 55 from the inlet channel 61 (see FIG. 4A), the instrument air flows upward along the outer surface of the detector 40 along the cooling path 55. At this time, the instrument air flows while taking heat from the outer surface of the detector 40.

  The instrumentation air flows from the cooling path 55 of the inner cylinder part 53 into the cooling path 56 of the outer cylinder part 54 through the opening at the center of the upper surface of the detector 40. As the instrument air spreads radially in the cooling path 56, an air layer is formed by the instrument air between the heat insulating material 75 and the detector 40. At this time, the instrument air flows while taking heat from the heater 70 and the collection block 20 that have passed through the heat insulating material 75. In this way, the outer surface of the detector 40 is cooled by the instrument air flowing through the cooling path 55, and the heat toward the detector 40 from the collection block 20 and the heater 70 is cooled by the instrument air flowing through the cooling path 56. Is done. Therefore, the inside of the cooling jacket 50 is always kept below the allowable temperature of the detector 40. The instrument air is discharged from the cooling passage 56 to the outside through the outlet passage 62.

  As described above, the radiation measuring device 1 can be divided into the high temperature region and the low temperature region by the heat insulating material 75 and the cooling jacket 50. Therefore, in the high temperature region on the upper side of the apparatus, the inside of the collection block 20 can be heated by the heater 70 to suppress the generation of corrosive gas due to the temperature drop of the exhaust. On the other hand, the detector 40 can be cooled by the cooling jacket 50 in the low temperature region on the lower side of the apparatus, and can be kept within an allowable temperature at which sufficient detection accuracy can be obtained. Moreover, since the hot air from the collection block 20 tends to go upward, the thermal conditions of the detector 40 are relaxed by arranging the detector 40 below the collection block 20.

  Here, with reference to FIG.6 and FIG.7, the heat distribution of a radioactivity measuring apparatus is demonstrated. FIG. 6 is a heat distribution diagram of the radioactivity measurement apparatus according to the present embodiment. FIG. 7 is a relationship diagram between the distance from the detector surface and the temperature according to the present embodiment. 6A shows the temperature distribution of the perspective view of the collection block, and FIG. 6B shows the temperature distribution of the cross-sectional view of FIG. 6A. FIG. 7 shows the relationship between the distance and the temperature along the line AA in FIG. 6B.

  As shown in FIGS. 6A and 6B, the collection block 20 is heated from below by a plate-like heater 70 and is heated from the side by a tape-like heater 71 (see FIG. 6B). For this reason, the temperature near the installation of the heaters 70 and 71 is heated to 120 ° C. or higher. In this case, the temperature of the notch 22 and the filter paper holder 25 in the notch 22 of the collection block 20 is lower than the temperature in the vicinity of the heater 71 installation by the amount not heated by the heater 71. Here, since the flow path of the collection block 20 is formed at a location heated to 120 ° C. or more by the heaters 70 and 71, the temperature of the exhaust does not become 120 ° C. or less, and corrosive gas is generated. Is suppressed.

  On the other hand, as shown in FIG. 7, between the surface of the detector 40 and the exhaust in the collection block 20, the detector cap 45, the air layer of instrument air, the outer cylinder portion 54 of the cooling jacket 50, and the heat insulating material 75, the heater 70, and the bottom wall of the collection block 20 are interposed. The back side of the heater 70 which is 10 mm or more away from the surface of the detector 40 is 120 ° C. or more, and the temperature is lowered to around 40 ° C. by the heat insulating material 75 located 6 mm to 10 mm from the surface of the detector 40. The temperature of the outer cylinder portion 54 located 5 to 6 mm from the surface of the detector 40 is not substantially changed, and the temperature is lowered to 40 ° C. or less by the air layer of instrument air located 1 to 5 mm from the surface of the detector 40. doing.

  In this way, by interposing the heat insulating material 75 and the cooling jacket 50, a location of 120 ° C. or higher and a location of 40 ° C. or lower are created between the surface of the detector 40 and 16 mm. Therefore, it is possible to suppress the generation of corrosive gas in the collection block 20 and to suppress the surface temperature of the detector 40 to an allowable temperature.

  As described above, in the radioactivity measurement apparatus 1 according to the present embodiment, since the heat from the collection block 20 tends to be directed upward, the detector 40 is installed by installing the detector 40 below the collection block 20. The thermal conditions can be relaxed. Moreover, since the detector 40 is installed below the collection block 20 when the radioactivity measuring apparatus 1 is assembled, the assembling work is simplified and the cost is reduced as compared with the configuration in which the detector 40 is suspended from above. be able to. In addition, since the heat from the collection block 20 is insulated by the heat insulating material 75, the temperature of the detector 40 does not rise greatly even if the detector 40 is brought closer to the collection block 20. Therefore, the detection accuracy of the radiation by the detector 40 can be increased.

  In addition, this invention is not limited to the said embodiment, It can change and implement variously. In the above-described embodiment, the size, shape, and the like illustrated in the accompanying drawings are not limited to this, and can be appropriately changed within a range in which the effect of the present invention is exhibited. In addition, various modifications can be made without departing from the scope of the object of the present invention.

  For example, in this Embodiment, although the structure which the radioactivity measuring apparatus 1 was installed in incineration equipment was demonstrated, it is not limited to this structure. The radioactivity measuring apparatus 1 may be installed in any facility as long as the radioactivity concentration of waste dust can be measured.

  Moreover, in this Embodiment, it was set as the structure by which the heat insulating material 75 is interposed between the collection block 20 and the detector 40, However, It is not limited to this structure. A sufficient gap may be provided between the collection block 20 and the detector 40 in place of the heat insulating material 75 interposed.

  In the present embodiment, the heater 70 and the heat insulating material 75 are formed in a plate shape, but the heater 70 and the heat insulating material 75 may be formed in a sheet shape. In addition, the shape of the heater 70 and the heat insulating material 75 is not particularly limited as long as the heater 70 and the heat insulating material 75 have a thickness that does not hinder the detection of radiation by the detector 40.

  Moreover, in this Embodiment, although the collection block 20 was set as the structure heated with the heaters 70 and 71, it is not limited to this structure. If the collection block can be heated sufficiently by only the high-temperature exhaust drawn into the collection block 20, only one of the heaters 70 and 71 may be provided, or both may not be provided.

  Further, in the present embodiment, the detector 40 is cooled by the instrumented air in the cooling jacket 50, but is not limited to this configuration. The cooling jacket 50 may be supplied with a fluid that can cool the detector 40. For example, the cooling jacket 50 may be supplied with liquid instead of gas.

  Further, in the present embodiment, the upper portion of the cooling jacket 50 is formed in a double structure by the inner cylinder portion 53 and the outer cylinder portion 54, but is not limited to this configuration. The upper portion of the cooling jacket 50 may be formed with a single structure or a triple structure as long as a cooling path is formed between the collection block 20 and the detector 40.

  In the present embodiment, the convex portions 48 are provided at four locations on the outer peripheral portion of the detector cap 45, but the position, number, and shape of the convex portions 48 are not particularly limited. The convex portion 48 only needs to be able to abut against the inner surface of the cooling jacket 50 and form a cooling path between the inner surface of the cooling jacket 50 and the outer surface of the detector 40.

  Further, in the present embodiment, the collection space 27 and the outlet channel 32 are communicated with each other in the collection block 20 through the circular flat channel 33, but the present invention is not limited to this configuration. Any shape of flow path may be formed in the collection block 20 as long as a smooth flow of exhaust gas can be created from the collection space 27 to the outlet flow path 32.

  Further, in the present embodiment, the cutout 22 of the collection block 20 is cut out inward from the outer peripheral position facing the outlet flow path 32 with the collection space 27 interposed therebetween. It is not limited. The notch 22 only needs to be formed so that the filter paper holder 25 can be attached to the collection block 20.

  In the present embodiment, the collection block 20 is configured to collect the waste dust from the exhaust by the filter paper 26, but is not limited to this configuration. The collection block 20 may be configured to have a dust collection unit capable of collecting waste dust from the exhaust, and the filter paper 26 is an example thereof, and dust may be collected by a filter or the like.

  As described above, the present invention has an effect that it is possible to measure the radioactive concentration of waste dust with a simple and inexpensive configuration while keeping the detector within an allowable temperature. This is useful for a radioactivity measuring device that measures the radioactivity concentration of discharged waste dust.

DESCRIPTION OF SYMBOLS 1 Radioactivity measuring apparatus 20 Collection block 21 Block main body 22 Notch 25 Filter paper holder 26 Filter paper 27 Collection space 31 Inlet flow path 32 Outlet flow path 33 Flat flow path 40 Detector 45 Detector cap 48 Convex part 50 Cooling jacket 55 Cooling path on the upstream side 56 Cooling path on the downstream side 70 Heater 75 Heat insulating material D Waste dust

Claims (7)

A radioactivity measuring device for measuring the radioactivity concentration of waste dust contained in exhaust gas,
A collection block in which a collection space for collecting waste dust from the exhaust is formed;
A detector arranged to detect radiation from waste dust below the collection block;
A heat insulating material interposed between the collection block and the detector ;
A heater interposed between the collection block and the heat insulating material so as to heat the collection space of the collection block ;
The radioactivity measuring apparatus, wherein the collection block is in contact with the detector through the heat insulating material. The radiation measuring apparatus according to claim 1 , wherein the heat insulating material and the heater are formed in a flat plate shape or a sheet shape. A cooling jacket forming a cooling path between the collection block and the detector;
A detector cap mounted on the detector inside the cooling jacket;
Wherein the detector cap claim 1, wherein a convex portion forming the cooling passages between the outer surface of the inner surface and the detector of the cooling jacket abuts against the inner surface of the cooling jacket is formed or The radioactivity measurement apparatus according to claim 2 . The cooling jacket is formed with an upstream cooling path for cooling the outer surface of the detector, and a downstream cooling path for cooling between the collection block and the detector,
The radioactivity measurement apparatus according to claim 3 , wherein the upstream cooling path and the downstream cooling path communicate with each other on a center line that vertically penetrates the detector. In the collection space of the collection block, exhaust dust is collected from the exhaust by the filter paper as the exhaust is drawn from above toward the filter paper, and the radiation from the waste dust deposited on the upper surface of the filter paper The radioactivity measuring apparatus according to claim 1 , wherein the radioactivity measuring apparatus is detected from the back side of the filter paper by a detector. The collection block includes an inlet channel that draws exhaust gas into the collection space, an outlet channel that exhausts exhaust gas from the collection space at a side of the inlet channel, the collection space, and the outlet flow The radioactivity measuring apparatus according to claim 5 , wherein a circular flat flow path that is eccentric toward the outlet flow path is formed so as to connect the paths. The collection block is formed with a notch to which a filter paper holder holding the filter paper can be attached,
The radioactivity measuring apparatus according to claim 6 , wherein the notch is notched inward from an outer peripheral position facing the outlet channel with the collection space interposed therebetween.

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