Radiation monitor

Abstract

Provided is a radiation monitor that comprises: a radiation detection unit including a solid phosphor that emits photons in response to incident radiation; a flow path through which flows a liquid to be detected provided inside the phosphor; and a light detection unit that detects the photons emitted from the phosphor and converts the photons into an electrical signal. The flow path has a portion the periphery of which is covered with the phosphor in a cross section in a direction orthogonal to the flow direction of the liquid to be detected.

Description

Radiation monitor

[0001] The present invention relates to a radiation monitor.

[0002] Radiation measurement devices using, for example, liquid scintillators, ionization chambers, solid scintillators, etc., are used to measure radiation from nuclides in liquids such as water. Generally, beta rays generated from Sr-90 or Y-90 have a short maximum range in liquids, approximately 1.1 cm. For this reason, badge measurements are performed by sampling. For example, a radiation monitor has been proposed in which a sampling container through which the liquid to be detected passes is placed between two opposing flat solid scintillators (see, for example, Patent Document 1). In this radiation monitor, the solid scintillator is excited by radiation emitted from the liquid to be detected, and the photons generated by the solid scintillator are measured to determine the concentration of the radioactive material. Such radiation monitors using solid scintillators are expected to be a method capable of online measurement of radionuclides in liquids such as water.

[0003] Japanese Patent Application Laid-Open No. 2007-178336

[0004] However, in the radiation monitor described in Patent Document 1, photons are generated within the flat surface of the scintillator disposed opposite the sampling container, and therefore the amount of photons generated is small, resulting in low detection sensitivity.

[0005] In order to solve the above-mentioned problems, the present invention provides a radiation monitor capable of improving detection sensitivity.

[0006] The above and other objects of the present invention and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[0007] The radiation monitor of the present invention comprises a radiation detection unit including a solid phosphor that emits photons in response to incident radiation, a flow path through which a detectable liquid flows provided within the phosphor, and a light detection unit that detects the photons emitted from the phosphor and converts them into an electrical signal. The flow path has a portion that is surrounded by the phosphor in a cross section perpendicular to the flow direction of the detectable liquid.

[0008] The radiation monitor of the present invention comprises a radiation detection unit having a solid phosphor that emits photons in response to incident radiation, a flow path provided within the phosphor through which a detectable liquid from the outside flows, and a photodetection unit that detects the photons emitted from the phosphor and converts them into an electrical signal. The flow path communicates from the inlet for the detectable liquid disposed in the phosphor to the outlet for the detectable liquid by at least one of a straight flow path portion in which the flow portion for the detectable liquid is formed in a straight line and a curved flow path portion in which the flow portion is formed in a curved line.

[0009] According to the present invention, it is possible to provide a radiation monitor capable of improving detection sensitivity.

[0010] Problems, configurations, and effects other than those described above will become clear from the following description of the embodiments.

[0011] FIG. 1 is a diagram showing a schematic configuration of a radiation monitor according to a first embodiment. FIG. 2 is a cross-sectional view of the radiation monitor shown in FIG. 1 taken along line A-A. FIG. 3 is a cross-sectional view of the radiation monitor shown in FIG. 1 taken along line B-B. FIG. 4 is a cross-sectional view (corresponding to line A-A) of a radiation monitor according to a second embodiment. FIG. 5 is a cross-sectional view (corresponding to line B-B) of a radiation monitor according to a second embodiment. FIG. 6 is a cross-sectional view (corresponding to line A-A) of a radiation monitor according to a third embodiment. FIG. 7 is a cross-sectional view (corresponding to line B-B) of a radiation monitor according to a third embodiment. FIG. 8 is a cross-sectional view (corresponding to line A-A) of a radiation monitor according to a third embodiment. FIG. 9 is a cross-sectional view (corresponding to line A-A) of a radiation monitor according to a third embodiment. FIG. 10 is a cross-sectional view (corresponding to line A-A) of a radiation monitor according to a third embodiment. FIG. 11 is a cross-sectional view (corresponding to line A-A) of a radiation monitor according to a fourth embodiment. FIG. 12 is a cross-sectional view (corresponding to line B-B) of a radiation monitor according to a fourth embodiment. FIG. 13 is a cross-sectional view (corresponding to line A-A) of a radiation monitor according to a fourth embodiment. FIG. 14 is a cross-sectional view (corresponding to line A-A) of a radiation monitor according to a fourth embodiment. FIG. 15 is a cross-sectional view (corresponding to line B-B) of a radiation monitor according to a fourth embodiment. FIG. 16 is a cross-sectional view (corresponding to line A-A) of a radiation monitor according to a fifth embodiment. FIG. 17 is a cross-sectional view (corresponding to line A-A) of a radiation monitor

[0012] An example of a radiation monitor according to an embodiment of the present invention will be described below with reference to the drawings. Note that the present invention is not limited to the following example. In each of the drawings described below, common members are given the same reference numerals. Furthermore, in the drawings used in this specification, identical or corresponding components are given the same reference numerals, and repeated explanations of these components may be omitted.

[0013] The description will be given in the following order: 1. Configuration of a radiation monitor (first embodiment) 2. Configuration of a radiation monitor (second embodiment) 3. Configuration of a radiation monitor (third embodiment) 4. Configuration of a radiation monitor (fourth embodiment) 5. Configuration of a radiation monitor (fifth embodiment) 6. Configuration of a radiation monitor (sixth embodiment)

[0014] 1. Configuration of Radiation Monitor (First Embodiment) A first embodiment of a radiation monitor will be described. Fig. 1 shows a schematic configuration (perspective view) of a radiation monitor 1 according to the first embodiment. Fig. 2 shows a cross-sectional view of the radiation monitor 1 shown in Fig. 1 taken along line A-A, and Fig. 3 shows a cross-sectional view of the radiation monitor 1 taken along line B-B. As shown in Fig. 1, the radiation monitor 1 has a radiation detection unit 2 and a light detection unit 6. The radiation detection unit 2 and the light detection unit 6 that constitute the radiation monitor 1 will be described below.

[0015] 1 and 2, the radiation detection unit 2 is composed of a phosphor 3 and a flow path 4. The flow path 4 is formed within the phosphor 3, and a detectable liquid 5 flows through the flow path 4. The phosphor 3 interacts with β rays from the detectable liquid 5 within the flow path 4, causing it to emit photons.

[0016] (Phosphor) The phosphor 3 is made of a solid composition to form the flow path 4 inside. The phosphor 3 is not particularly limited as long as it is a composition that exhibits luminescence, and examples of such luminescence include photoluminescence due to light such as ultraviolet light, radioluminescence due to radiation, cathode luminescence due to an electron beam, electroluminescence due to an electric field, and chemiluminescence due to a chemical reaction. Specifically, the phosphor 3 may be made of, for example, NaI, CsI, LiI, or SrI as a base material. ２ , Bi ４ Ge ３ O １２ , Bi ４ Si ３ O １２ , CdWO ４ , PbWO ４ , ZnS, CaF ２ , LuAG, LuAP, Lu ２ O ３ , Y ３ Al５ O １２ , YAlO ３ , Lu ２ SiO ５ ,LYSO,Y ２ SiO ５ , Gd ２ SiO ５ , BaF ２ , CeF ３ , CeBr ３ , CsF, LiF, Gd ２ O ２ S, LaBr ３ , CeBr ３ , Gd ３ Al ２ Ga ３ O １２ , Cs ２ LiYCl ６ , Cs ２ HfI ６ , ScTaO ４ , LaTaO ４ , LuTaO ４ , GdTaO ４ , YTaO ４ ,InBO ３ , Y ２ O ２ S, ZnSiO ４ and a light-transmitting material such as a sialon phosphor, and a rare earth element such as La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, or Y, or a rare earth element such as Tl, Na, Ag, W, Cu, Al, Au, Mn, or CO ３ Examples of light-transmitting materials include those containing elements, ions, and fluorescent materials such as InBO. ３ : Tb, InBO ３ :Eu, ZnS:Cu, ZnS:Al, ZnS:Au, Y ２ O ２ S: Eu, Y ２ O ２ S: Tb, ZnSiO ４ : Mn and the like.

[0017] The valence of the element ion contained in the phosphor 3 is not particularly limited as long as it can be used for luminescence, and can be, for example, monovalent, divalent, trivalent, tetravalent, etc. Furthermore, as the phosphor 3, for example, an organic phosphor such as a complex, an organic compound, a plastic scintillator, etc. can also be used.

[0018] (Flow path) The radiation detection unit 2 includes two phosphors 3 bonded together. Each phosphor 3 has a symmetrical semicircular groove on one of its main surfaces. The phosphors 3 are bonded together with the positions of the semicircular grooves aligned, forming a tubular cavity inside the phosphor 3. This tubular cavity has openings 43, 44 at two locations: one at an arbitrary position on the surface of the phosphor 3 and another at another position on the surface. The tubular cavity communicates with the openings 43, 44. The communicating cavity inside the phosphor 3 is the flow path 4 through which the detectable liquid 5 containing radioactive nuclides flows. Therefore, the radiation detection unit 2 has a flow path 4 formed by a tubular cavity formed inside the phosphor 3.

[0019] A detectable liquid 5, indicated by an arrow in Fig. 2, is supplied from the outside to the flow path 4. In Fig. 2, the direction of the arrow indicates the flow direction of the detectable liquid 5. The detectable liquid 5 flows into the flow path 4 from one opening 43 (inlet). The detectable liquid 5 then passes through the flow path 4 and is discharged from the other opening 44 (outlet). In the radiation monitor 1 shown in Fig. 1, the phosphor 3 is formed as a rectangular parallelepiped, as an example. The shape of the phosphor 3 is not particularly limited, and may be any shape as long as it allows the flow path 4 to be formed therein and allows the light detection unit 6 to detect photons.

[0020] The flow path 4 is a tubular hollow portion formed within the phosphor 3, and is therefore surrounded by the phosphor 3. That is, the flow path 4 has a portion whose entire periphery is covered by the phosphor 3 in a cross section perpendicular to the flow direction of the detection liquid 5. Although the radiation monitor 1 shown in FIG. 1 has the entire flow path 4 covered by the phosphor 3, this is not limited thereto. It is sufficient that at least a portion of the periphery of the flow path 4 is covered by the phosphor 3. Therefore, the flow path 4 may have a portion that is not covered by the phosphor 3, or a portion whose periphery is not covered by the phosphor 3.

[0021] The flow path 4 has a straight flow path section 41 whose flow portion is formed in a straight line and a curved flow path section 42 whose flow portion is formed in a curved line. The flow path 4 is connected from the inlet to the outlet by a combination of the straight flow path section 41 and the curved flow path section 42. Therefore, in the configuration shown in FIG. 2 , the test liquid 5 flows into the straight flow path section 41 from an opening 43 (inlet) at the bottom of the drawing. The test liquid 5 then flows from the straight flow path section 41 into the curved flow path section 42. The test liquid 5 then flows from the curved flow path section 42 into the straight flow path section 41 at the top of the drawing and is discharged from an opening 44 (outlet). Note that the flow path 4 may be formed only with the straight flow path section 41 or only with the curved flow path section 42. Furthermore, in the flow path 4, the straight flow path sections 41 may be directly connected to each other, or the curved flow path sections 42 may be directly connected to each other.

[0022] The flow path 4 shown in FIG. 2 has a non-linear, folded shape formed by a combination of a straight flow path portion 41 and a curved flow path portion 42. However, the shape of the flow path 4 is not limited to this. For example, the flow path 4 may have an inlet and an outlet formed on another surface of the phosphor 3, and the inlet and outlet are linearly connected. The flow path 4 may also have a configuration in which multiple straight flow path portions 41 are arranged in parallel positions, a configuration in which the straight flow path portions 41 are arranged in a twisted position, or a configuration in which multiple curved flow path portions 42 form multiple folded sections. Furthermore, in the radiation monitor 1 shown in FIG. 1, the flow path 4 is arranged in two dimensions by the straight flow path portion 41 extending in the x-axis direction and the curved flow path portion 42 extending in the y-axis direction, but is not limited to this shape. For example, the flow path 4 may be formed by a three-dimensionally arranged cavity in which at least one of the straight flow path portion 41 and the curved flow path portion 42 extends in the z-axis direction. In this way, the flow path 4 may be linearly or non-linearly connected from the inlet to the outlet by at least one of the straight flow path portion 41 and the curved flow path portion 42 .

[0023] The cross-sectional shape of the flow path 4 is not particularly limited as long as it allows the detection liquid 5 to pass through it. For example, by making the inner diameter of the flow path 4 1.1 cm or less, it is possible to reduce the attenuation of β rays in water and improve the detection sensitivity of β rays. Furthermore, although the flow path 4 shown in FIGS. 1 and 3 has a cylindrical cross section, the cross-sectional shape of the flow path 4 is not limited thereto. The cross-sectional shape of the flow path 4 may be an ellipse or a polygonal shape such as a rectangle or a square. Furthermore, it is preferable that the inner diameter of the flow path 4 is a constant value. It is also preferable that the cross-sectional shape of the flow path 4 does not change. By not changing the inner diameter or cross-sectional shape, the radiation monitor 1 can stabilize the detection sensitivity.

[0024] (Method of Manufacturing the Radiation Detector) The phosphor 3 can be manufactured using, for example, the floating zone method, the Czochralski method (pulling-up method), the micro-pulling-down method, the Bridgman method, the Bernoulli method, organic synthesis, or the like. The flow path 4 can be manufactured using a method capable of microfabrication of the phosphor 3. For example, a semicircular groove is formed on the surface of the phosphor 3 using mechanical processing, chemical reaction, or the like. Then, the processed surfaces of the phosphors 3 with the grooves formed thereon are bonded together. This allows the manufacture of a radiation detector 2 having a flow path 4 formed inside the phosphor 3. Furthermore, if nonlinear processing is difficult due to the material of the solid phosphor, the difficult-to-process portion may be formed using a material other than phosphor to relatively reduce the difficulty of processing. In this way, the radiation detector may be realized by combining phosphor and a material other than phosphor. Furthermore, as an example of a folded shape, a folded shape can be described as a shape having a flow path whose dimension is longer than the sum of the vertical and horizontal dimensions of the processed surface. This allows a photodetector to be installed near the light source, thereby improving detection efficiency.

[0025] [Light Detector] The light detector 6 is disposed adjacent to the phosphor 3 of the radiation detection unit 2. The radiation monitor 1 continuously measures the radiation dose in the detection target liquid 5 in the flow path 4, for example. The light detector 6 detects photons generated by the phosphor 3. The light detector 6 converts the photons generated by the phosphor 3 into an electrical pulse signal. There are no particular limitations on the light detector 6 as long as it is capable of converting photons into an electrical pulse signal, and for example, a photomultiplier tube, an avalanche photodiode, or the like can be used.

[0026] [Detection Liquid] The detection liquid 5 contains a nuclide that emits radiation. The nuclide is not particularly limited, but examples include Sr-90 and Y-90. The emitted radiation is not particularly limited, but examples include particle rays such as α-rays, β-rays, and neutron rays, and electromagnetic waves such as X-rays and γ-rays. Of these, the emitted radiation is preferably α-rays and β-rays. The detection liquid 5 contains the nuclide in a dissolved or dispersed state. The portion of the detection liquid 5 excluding the nuclide is not particularly limited as long as it is liquid, and may be, for example, nuclear plant treated water, seawater, brackish water, or other aqueous solution (brine water, etc.), but may also be fresh water.

[0027] [Water Flow Direction / Arrangement Direction] In the radiation monitor 1, when the y-axis direction is the vertical direction, the detectable liquid 5 is supplied from the opening 43 at the bottom (below the y-axis) of the flow path 4 to the opening 44 at the top (above the y-axis) as shown by the arrow in FIG. 2 . By supplying the detectable liquid 5 in this direction, the flow path 4 can be filled with the detectable liquid 5 without creating any cavities. As a result, the area adjacent to the phosphor 3 and the detectable liquid 5 can be increased. Note that the flow direction of the detectable liquid 5 is not particularly limited. For example, when the y-axis direction is the vertical direction, the detectable liquid 5 may be supplied from the opening 44 at the top (above the y-axis) of the flow path 4 to the opening 43 at the bottom (below the y-axis). This supply direction eliminates the need for a pressure device such as a pump to supply the detectable liquid 5, thereby eliminating mechanical vibration noise caused by the pressure device and improving measurement accuracy.

[0028] 2, the radiation detector 2 is arranged so that the linear flow path portion 41 is aligned in the y-axis direction. In the radiation monitor 1, the arrangement direction of the radiation detector 2 is not particularly limited, and for example, the radiation detector 2 may be arranged so that the x-axis direction or the z-axis direction is the vertical direction. Alternatively, the radiation detector 2 may be arranged at an angle, with any direction between the x-, y-, and z-axis directions being the vertical direction. When the radiation detector 2 is arranged in this manner, the detectable liquid 5 is supplied from one of the openings 43, 44 arranged in the horizontal direction, and the detectable liquid 5 is discharged from the other opening.

[0029] In the radiation monitor 1 configured as described above, the periphery of the flow path 4 is covered with the phosphor 3. Therefore, the radiation monitor 1 can increase the surface area of ​​the phosphor 3 in contact with the detectable liquid 5 compared to a conventional configuration using a flat-plate solid scintillator. That is, in a conventional configuration using a flat-plate solid scintillator, the flow path 4 has at least a portion that is not adjacent to the phosphor 3 in the cross section perpendicular to the flow direction of the detectable liquid 5. Therefore, radiation emitted in the direction not adjacent to the phosphor 3 does not enter the solid scintillator (phosphor), resulting in detection loss. In contrast, in the radiation monitor 1 of the present embodiment described above, the phosphor 3 covers the entire periphery of the flow path 4 in the cross section, thereby increasing the probability that radiation emitted from the detectable liquid 5 will enter the phosphor 3. In particular, the bending of the flow path 4 makes it easier for radiation emitted in the flow direction to enter the phosphor 3. Furthermore, the radiation monitor 1 has a folded shape formed by combining a straight flow path section 41 and a curved flow path section 42. The folded shape of the radiation monitor 1 allows the length of the flow path 4 to be increased. This increases the area of ​​contact between the detection liquid 5 and the phosphor 3 in the flow path 4 of the radiation monitor 1, increasing the probability of reaction between the phosphor 3 and radiation. Therefore, by having the flow path 4 formed within the phosphor 3, the radiation monitor 1 increases the probability of reaction between the phosphor 3 and radiation, improving detection sensitivity.

[0030] 2. Configuration of Radiation Monitor (Second Embodiment) Next, a second embodiment of the radiation monitor will be described. The radiation monitor of the second embodiment differs from the radiation monitor of the first embodiment described above only in the configuration of the flow path. Therefore, detailed description of the same configuration as the radiation monitor of the first embodiment will be omitted. FIGS. 4 and 5 show a schematic configuration of a radiation monitor 1A according to the second embodiment. The radiation monitor 1A shown in FIG. 4 corresponds to the cross-sectional view of the radiation monitor 1 shown in FIG. 1 taken along line A-A. The radiation monitor 1A shown in FIG. 5 corresponds to the cross-sectional view of the radiation monitor 1 shown in FIG. 1 taken along line B-B. The radiation monitor 1A shown in FIGS. 4 and 5 differs from the radiation monitor 1 shown in FIG. 1 only in the flow path 4, but the outer shape of the phosphor 3 and the configuration of the light detection unit 6 are the same.

[0031] 4 and 5 has a flow path 4 in a phosphor 3 that constitutes a radiation detection unit 2. As shown in Fig. 4, the flow path 4 has openings 43 and 44 on opposing surfaces where the light detection unit 6 is not disposed. The detectable liquid 5 flows into the flow path 4 from one opening 43 (inlet), passes through the flow path 4, and is discharged from the other opening 44 (outlet).

[0032] The flow path 4 has three straight flow path sections 41, each having a linear flow portion, and two curved flow path sections 42, each having a curved flow portion. The straight flow path sections 41 of the flow path 4 are connected by the curved flow path sections 42. The flow path 4 is extended in two dimensions by connecting the straight flow path sections 41 extending in the x-axis direction with the curved flow path sections 42 extending in the y-axis direction. In other words, the two curved flow path sections 42 form two turning points in the flow path 4.

[0033] As described above, in the radiation monitor 1A, the flow path 4, which is connected from the opening 43 (inlet) to the opening 44 (outlet), is formed in the phosphor 3 by the linear flow path portion 41 and the curved flow path portion 42 that are connected to each other. That is, the flow path 4 of the radiation monitor 1A is entirely surrounded by the phosphor 3 in a cross section perpendicular to the flow direction of the detection liquid 5, similar to the first embodiment described above.

[0034] As in the radiation monitors 1 and 1A of the first and second embodiments described above, the flow path 4 can have any shape as long as it is formed within the phosphor 3. In the radiation monitors 1 and 1A, the length of the flow path 4 covered by the phosphor 3 can be increased, thereby increasing the surface area of ​​the phosphor 3 that comes into contact with the detectable liquid 5. This increases the probability of the phosphor 3 reacting with radiation. Furthermore, while the radiation monitors 1 and 1A have a folded shape that connects the straight flow path section 41 and the curved flow path section 42, the number of straight flow path sections 41 and the curved flow path section 42 is not limited, and the flow path 4 can be made longer by increasing the number of foldings. Note that, although only one flow path 4 that connects within the phosphor 3 is shown in this embodiment, other flow paths that do not connect to the flow path 4 may be formed within the phosphor 3.

[0035] 3. Configuration of Radiation Monitor (Third Embodiment) Next, a third embodiment of the radiation monitor will be described. The radiation monitor of the third embodiment differs from the radiation monitor of the second embodiment described above only in that the radiation monitor of the third embodiment has a configuration in which a contamination prevention layer is provided in the flow path. Therefore, detailed description of the configuration similar to that of the radiation monitors of the first and second embodiments described above will be omitted.

[0036] Figures 6 and 7 show a schematic configuration of a radiation monitor 1B according to the third embodiment. The radiation monitor 1B shown in Figure 6 corresponds to a cross-sectional view of the radiation monitor 1 shown in Figure 1 taken along line A-A. The radiation monitor 1B shown in Figure 7 corresponds to a cross-sectional view of the radiation monitor 1 shown in Figure 1 taken along line B-B. The radiation monitor 1B shown in Figures 6 and 7 has a flow path 4 with a shape similar to that of the radiation monitor 1A shown in Figures 4 and 5.

[0037] 6 and 7 has a flow path 4 in a phosphor 3 that constitutes a radiation detection unit 2. Furthermore, the radiation monitor 1B has a contamination prevention layer 7 on the wall surface of the flow path 4. That is, in the radiation monitor 1B, the contamination prevention layer 7 is interposed between the detection target liquid 5 and the phosphor 3 in the flow path 4.

[0038] The contamination prevention layer 7 contacts the inner surface of the flow path 4, and can prevent contamination of the phosphor 3 due to the flow of the detectable liquid 5 inside the contamination prevention layer 7. Normally, when the detectable liquid 5 is supplied into the flow path 4, radioactive nuclides contained in the detectable liquid 5 adhere to the inner wall of the flow path 4. As a result, the inner wall of the flow path 4 is contaminated by the radioactive nuclides in the detectable liquid 5 being supplied. Furthermore, the contamination of the inner wall of the flow path 4 by these nuclides increases with the supply amount and supply time of the detectable liquid 5. When the surface is contaminated by nuclides, radiation originating from the nuclides (contamination) attached to the inner surface of the flow path 4 is mixed into the radiation from the radioactive material in the detectable liquid 5, which is the object of measurement by the radiation monitor 1B, resulting in so-called contamination.

[0039] The radiation monitor 1B has a contamination prevention layer 7 on the inner wall of the flow path 4, which prevents various substances from adhering (contaminating) to the phosphor 3. Furthermore, by providing the contamination prevention layer 7, even if contamination occurs, the contamination can be removed by removing and replacing the contamination prevention layer 7. Therefore, the radiation monitor 1B does not need to replace the phosphor 3 when contamination occurs, which makes it possible to reduce the cost of replacing the phosphor 3.

[0040] The contamination prevention layer 7 is not particularly limited as long as it allows the detection liquid 5 to pass through. The contamination prevention layer 7 may be formed, for example, from a hose or tube made of PVC (polyvinyl chloride) or other resin. Forming the contamination prevention layer 7 from a hose or tube makes it easy to remove and replace the contamination prevention layer 7. The contamination prevention layer 7 may also be formed from a coating layer or a vapor deposition layer on the groove portion of the phosphor 3 that forms the flow path 4. When the contamination prevention layer 7 is formed from a coating layer or a vapor deposition layer, it can be removed and replaced by peeling off the contamination prevention layer 7 and reforming it.

[0041] The contamination prevention layer 7 may also be made of a water-repellent material. For example, a water-repellent silicone resin or fluororesin may be applied to the surface of the contamination prevention layer 7 to impart water repellency to the inner wall surface of the contamination prevention layer 7. The water-repellent nature of the inner wall of the contamination prevention layer 7 can suppress adhesion of β-ray-emitting nuclides to the contamination prevention layer 7. This reduces the frequency with which the contamination prevention layer 7 needs to be replaced.

[0042] The stain-preventing layer 7 has a density of 1.0 g / cm ３ 2.0g / cm or more ３ It is preferable to use the following low density materials: ３ If the density of the contamination prevention layer 7 is 2.0 g / cm or more, it is easy to prevent contamination of the phosphor 3. ３ If the thickness of the anti-contamination layer 7 is 0.7 mm or less, the attenuation of β rays in the anti-contamination layer 7 can be reduced. Therefore, a decrease in the detection sensitivity of the radiation monitor 1B due to the anti-contamination layer 7 can be suppressed. Furthermore, the thickness of the anti-contamination layer 7 is preferably 0.7 mm or more and 3 mm or less. If the thickness of the anti-contamination layer 7 is 0.7 mm or more, the adhesion of nuclides to the phosphor 3 can be suppressed, and manufacturing becomes easier. Furthermore, if the thickness of the anti-contamination layer 7 is 3 mm or less, the attenuation of β rays in the anti-contamination layer 7 can be reduced. Therefore, a decrease in the detection sensitivity of the radiation monitor 1B due to the anti-contamination layer 7 can be suppressed.

[0043] An example of a method for manufacturing the anti-contamination layer 7 is shown in Figure 8. When the anti-contamination layer 7 is formed from a hose or a tube, the anti-contamination layer 7 can be placed inside the flow path 4 by sandwiching the anti-contamination layer 7 between two phosphors 3, as shown in Figure 8. When the anti-contamination layer 7 is formed from a coating layer, a vapor deposition layer, or the like, the anti-contamination layer 7 can be placed inside the flow path 4 by forming a layer of the desired material in the semicircular groove formed on the surface of the phosphor 3.

[0044] 4. Configuration of Radiation Monitor (Fourth Embodiment) Next, a fourth embodiment of the radiation monitor will be described. The radiation monitor of the fourth embodiment differs from the radiation monitor of the third embodiment described above only in the arrangement of the photodetector. Therefore, detailed description of the same configuration as the radiation monitors of the first, second, and third embodiments described above will be omitted.

[0045] Figures 9 and 10 show the schematic configuration of a radiation monitor 1C according to the fourth embodiment. Figures 11 and 12 show the schematic configuration of a radiation monitor 1D according to the fourth embodiment. The radiation monitors 1C and 1D shown in Figures 9 and 11 correspond to the cross-sectional view of the radiation monitor 1 shown in Figure 1 taken along line A-A. The radiation monitors 1C and 1D shown in Figures 10 and 12 correspond to the cross-sectional view of the radiation monitor 1 taken along line B-B. The radiation monitors 1C and 1D shown in Figures 9 to 12 have a flow path 4 and a contamination prevention layer 7 having the same shape as the radiation monitor 1A shown in Figures 6 and 7.

[0046] As shown in FIGS. 9 to 12 , in the radiation monitors 1C and 1D, the photodetectors 6 can be arranged at any position relative to the phosphor 3. Increasing the number of photodetectors 6 allows for efficient detection of photons generated in the phosphor 3. In particular, arranging the photodetectors 6 to match the shape of the flow path 4 allows for efficient detection of photons generated in the phosphor 3. In the radiation monitor 1C shown in FIGS. 9 and 10 , the photodetectors 6 are arranged at six positions in total, three on each side of the phosphor 3 (x-axis direction in the drawing), in accordance with the position of the straight flow path section 41. In the radiation monitor 1D shown in FIGS. 11 and 12 , the photodetectors 6 are arranged at eight positions in total, three on each side of the phosphor 3 and one on each of the top and bottom surfaces of the phosphor 3 (y-axis direction in the drawing), in accordance with the position of the straight flow path section 41. In this way, increasing the number of connected photodetectors 6 in the radiation monitors 1C and 1D allows for efficient detection of photons generated in the phosphor 3, improving detection sensitivity. In the radiation monitors 1C and 1D, the photodetectors 6 are connected to surfaces other than the surface on which the openings 43 and 44 are formed, but the photodetectors 6 may be connected to the surface on which the openings 43 and 44 are formed. Furthermore, although the photodetectors 6 are arranged in parallel in the y-axis direction in the drawing, they may also be arranged in parallel in the x-axis direction or in parallel in both the x-axis and y-axis directions.

[0047] 5. Configuration of Radiation Monitor (Fifth Embodiment) Next, a fifth embodiment of a radiation monitor will be described. The radiation monitor of the fifth embodiment differs from the radiation monitor of the third embodiment described above only in that it has a light guide between the phosphor and the photodetector. Therefore, detailed description of the same configuration as the radiation monitors of the first, second, and third embodiments described above will be omitted.

[0048] Fig. 13 shows a schematic configuration of a radiation monitor 1E according to the fifth embodiment. The radiation monitor 1E shown in Fig. 13 corresponds to a cross-sectional view taken along line B-B of the radiation monitor 1 shown in Fig. 1. Note that the drawing of the radiation monitor 1E corresponding to the cross-sectional view taken along line A-A of the radiation monitor 1 shown in Fig. 1 is the same as Fig. 6, and therefore will not be shown here.

[0049] As shown in Fig. 13, in the radiation monitor 1E, a light guide 8 is connected between the light detecting unit 6 and the phosphor 3. The light guide 8 transmits photons generated in the phosphor 3 to the light detecting unit 6. The light detecting unit 6 detects the photons propagated by the light guide 8. The light guide 8 is installed so as to cover the entire surfaces of the phosphor 3 that face each other in the x-axis direction in the drawing. By covering the entire surfaces of the phosphor 3, it is possible to suppress loss of photons generated in the phosphor 3.

[0050] The light guide 8 is not particularly limited as long as it can transmit photons from the phosphor 3 to the photodetector 6, and can be made of glass, resin, etc. The shape of the light guide 8 is not particularly limited as long as it can efficiently transmit photons from the phosphor 3 to the photodetector 6.

[0051] The radiation monitor 1E has the light guide 8, and therefore can efficiently detect photons generated in the phosphor 3 without providing multiple light detecting units 6. Therefore, the radiation monitor 1E can improve the detection sensitivity of photons generated in the phosphor 3 and reduce the installation costs of the light detecting units 6.

[0052] 6. Configuration of Radiation Monitor (Sixth Embodiment) Next, a sixth embodiment of the radiation monitor will be described. The radiation monitor of the fifth embodiment differs from the radiation monitor of the second embodiment described above only in the shape of the flow path. Therefore, detailed description of the same configuration as the radiation monitors of the first and second embodiments described above will be omitted.

[0053] Fig. 14 shows a schematic configuration of a radiation monitor 1F according to the sixth embodiment. The radiation monitor 1F shown in Fig. 14 corresponds to a cross-sectional view of the radiation monitor 1 shown in Fig. 1 taken along line A-A. Note that, in the radiation monitor 1F, a view corresponding to a cross-sectional view of the radiation monitor 1 shown in Fig. 1 taken along line B-B is omitted because it is the same as Fig. 5. Furthermore, the light detection unit is not shown in Fig. 14.

[0054] As shown in Fig. 14, in the radiation monitor 1F, the flow path 4 formed in the phosphor 3 is formed in a non-linear shape using only linear flow path portions 41. The flow path 4 has three linear flow path portions 41 extending in the x-axis direction in the drawing and three linear flow path portions 41 extending in the y-axis direction. In the radiation monitor 1F, the flow path 4 is formed in the phosphor 3, and communicates from an opening 43 (inlet) to an opening 44 (outlet) by the linear flow path portions 41 extending in the x-axis direction and the y-axis direction, respectively. In the flow path 4, the linear flow path portions 41 extending in the x-axis direction and the linear flow path portions 41 extending in the y-axis direction intersect with each other and communicate with each other. Therefore, the flow path 4 is arranged in a lattice pattern in the phosphor 3, with the linear flow path portions 41 intersecting each other.

[0055] The detection target liquid 5 flows from an opening 43 (inlet) at the bottom of the drawing into a straight flow path section 41 extending in the x-axis direction. The detection target liquid 5 then branches from the straight flow path section 41 extending in the x-axis direction and flows into each of three connected straight flow path sections 41 extending in the y-axis direction. Furthermore, the detection target liquid 5 that flows into each straight flow path section 41 extending in the y-axis direction branches and merges into each of the intersecting straight flow path sections 41 extending in the x-axis direction, or flows directly downward in the y-axis direction. The detection target liquid 5 then flows from the curved flow path section 42 into the straight flow path section 41 at the top of the drawing and is discharged from an opening 44 (discharge port).

[0056] As in the radiation monitor 1F, the flow path 4 formed in the phosphor 3 may be formed only by a straight flow path section 41. Furthermore, the flow path 4 does not have to be formed by a single flow path 4 from the opening 43 (inlet) to the opening 44 (outlet). As described above, the flow path 4 can be formed by a combination of only straight flow path sections 41, a combination of only curved flow path sections 42, or a combination of straight flow path sections 41 and curved flow path sections 42. The flow path 4 can be made longer by having a turnback shape, a branching shape, or a merging shape. In the radiation monitor 1, by increasing the flow path length, the area where the detectable liquid 5 and the phosphor 3 are adjacent to each other in the flow path 4 is increased, thereby increasing the probability of the phosphor 3 reacting with radiation.

[0057] It should be noted that the present invention is not limited to the above-described embodiments and various modifications are possible. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to embodiments that include all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment. It is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to delete part of the configuration of each embodiment, or to add or replace other configurations.

[0058] 1, 1A, 1B, 1C, 1D, 1E, 1F... Radiation monitor, 2... Radiation detection unit, 3... Fluorescent material, 4... Flow path, 5... Liquid to be detected, 6... Light detection unit, 7... Contamination prevention layer, 8... Light guide, 41... Straight flow path portion, 42... Curved flow path portion, 43, 44... Openings

Claims

1. A radiation monitor comprising: a radiation detection unit including a solid phosphor that emits photons in response to incident radiation; a flow path through which a detectable liquid flows that is provided within the phosphor; and a light detection unit that detects the photons emitted from the phosphor and converts them into an electrical signal, wherein the flow path has a portion that is surrounded by the phosphor in a cross section perpendicular to the flow direction of the detectable liquid.

2. The radiation monitor according to claim 1, wherein the radiation detection unit is provided with a contamination prevention layer between the flow path and the solid phosphor.

3. The radiation monitor according to claim 2, wherein the contamination prevention layer is removable from the solid phosphor.

4. The radiation monitor according to claim 2, wherein the contamination prevention layer is water repellent.

5. The stain-preventing layer has a density of 2.0 g / cm ３ The radiation monitor according to claim 2 , wherein:

6. A radiation monitor as described in claim 1, wherein the flow path has a plurality of straight flow path sections in which the flow portion of the detectable liquid is formed in a straight line, and the straight flow path sections connect the inlet and outlet of the detectable liquid.

7. A radiation monitor as described in claim 6, wherein the flow path has a curved flow path portion in which the detection liquid flows, and the straight flow path portions are connected to each other via the curved flow path portion.

8. The radiation monitor according to claim 6, wherein the straight flow path portions of the flow path are directly connected to each other.

9. The radiation monitor according to claim 1, wherein the flow path has an inner diameter of 1.1 cm or less.

10. The radiation monitor according to claim 1, further comprising a light guide between the light detection unit and the phosphor.

11. A radiation monitor comprising: a radiation detection unit having a solid phosphor that emits photons in response to incident radiation; a flow path provided within the phosphor through which a detectable liquid from the outside flows; and a light detection unit that detects the photons emitted from the phosphor and converts them into an electrical signal, wherein the flow path connects from an inlet to an outlet of the detectable liquid placed in the phosphor by at least one of a straight flow path section in which the flow portion of the detectable liquid is formed in a straight line and a curved flow path section in which the flow portion is formed in a curved line.

12. The radiation monitor according to claim 11, wherein the flow path is non-linearly connected to the straight flow path portion and the curved flow path portion.

13. The radiation monitor according to claim 12, wherein the radiation detection unit includes a contamination prevention layer between the flow path and the solid phosphor.

14. The radiation monitor of claim 13, wherein the contamination prevention layer is removable from the solid phosphor.

15. A radiation monitor as described in claim 14, wherein the flow path is realized by bonding a groove shape formed on the processed surface of the radiation detection portion, and the contamination prevention layer is removable from the solid phosphor when the bonding is released.

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