Radioactive material monitoring device and radioactive material monitoring method

Abstract

To provide a radioactive material monitoring device capable of accurately detecting the concentration of radioactive materials in a liquid to be detected. [Solution] A radioactive material monitoring device comprising a flow channel through which a liquid to be detected flows, a counter unit that counts signals based on radiation generated from within the flow channel, and an analysis unit that calculates the concentration of radioactive material in the liquid to be detected based on the radiation count rate obtained from the counter unit, wherein the analysis unit includes a background correction unit that calculates a background value from the count rate based on the volume of the liquid to be detected in the flow channel and the count rate obtained from the counter unit, and a concentration calculation unit that calculates the concentration of radioactive material in the liquid to be detected based on the background value calculated by the background correction unit and the count rate obtained from the counter unit.

Description

Technical Field

[0001] The present invention relates to a monitoring device for radioactive substances and a method for monitoring radioactive substances

Background Art

[0002] As a technique for monitoring radioactive substances in water, there is a technique described in Patent Document 1 below. In this Patent Document 1, it is described that "the sensitive area of the detection surface is wide, tritium water as a measurement sample is introduced into a thin hollow sampling container, and two detection units, a first detection unit and a second detection unit, are arranged close to each other and opposed to each other on both sides (detection surfaces) sandwiching the sampling container. Each detection unit is provided with a solid scintillator other than a plastic scintillator arranged close to the sampling container." According to this technique, it is said that the tritium concentration can be accurately detected by simultaneously detecting the scintillation light generated due to radiation in two detection units arranged opposite to each other with the sampling unit interposed therebetween

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the technique described in Patent Document 1, although the detection sensitivity of tritium can be improved due to the large surface area of the sampling container in contact with tritium water, the influence of tritium adhering as a contaminant on the surface of the large-area sampling container becomes large. That is, when contaminants adhere to the surface of the sampling container, the detection unit cannot distinguish between the signal from the contaminants and the signal from the radioactive substances in the detection liquid such as tritium water, and it has been difficult to accurately detect the concentration of the radioactive substances in the detection liquid

[0005] Therefore, the present invention aims to provide a radioactive material monitoring device and a radioactive material monitoring method that can accurately detect the concentration of radioactive material in a liquid to be detected. [Means for solving the problem]

[0006] To solve the above problems, for example, the configuration described in the claims may be adopted. The present invention includes multiple means for solving the above problems, but to give one example, a radioactive material monitoring device comprising a flow channel through which a liquid to be detected is passed, a counter unit that counts signals based on radiation generated from within the flow channel, and an analysis unit that calculates the concentration of radioactive material in the liquid to be detected based on the radiation count rate obtained from the counter unit, wherein the analysis unit comprises a background correction unit that calculates a background value from the count rate based on the volume of the liquid to be detected in the flow channel and the count rate obtained from the counter unit, and a concentration calculation unit that calculates the concentration of radioactive material in the liquid to be detected based on the background value calculated by the background correction unit and the count rate obtained from the counter unit. [Effects of the Invention]

[0007] The present invention provides a radioactive material monitoring device and a radioactive material monitoring method that can accurately detect the concentration of radioactive material in a liquid to be detected. [Brief explanation of the drawing]

[0008] [Figure 1] This is a diagram showing the configuration of a radioactive material monitoring device according to the first embodiment. [Figure 2] This diagram illustrates the relationship between the volume of liquid in the flow path and the count rate caused by contamination. [Figure 3] This is a flowchart illustrating a method for monitoring radioactive materials according to an embodiment. [Figure 4] This figure shows the relationship between the liquid volume in the flow path and the counting rate in a radioactive material monitoring device. [Figure 5] This is a diagram showing the main components of a radioactive material monitoring device according to a modified example of the first embodiment. [Figure 6] This is a diagram showing the configuration of a radioactive material monitoring device according to the second embodiment. [Figure 7] This is a diagram showing the configuration of a radioactive material monitoring device according to the third embodiment. [Figure 8] This is a diagram showing the configuration of a radioactive material monitoring device according to the fourth embodiment. [Modes for carrying out the invention]

[0009] Hereinafter, embodiments to which the present invention is applied will be described in detail with reference to the drawings. In each embodiment, the same components are denoted by the same reference numerals, and redundant descriptions are omitted.

[0010] ≪First Embodiment≫ Figure 1 is a diagram showing the configuration of a radioactive material monitoring device 1 according to the first embodiment. The monitoring device 1 shown in Figure 1 is a device for continuously measuring the concentration of radioactive material contained in the liquid to be detected L1 online.

[0011] Radioactive materials are nuclides that emit radiation. While there are no particular restrictions on the type of nuclide, examples include strontium-90 (Sr-90) and yttrium-90 (Y-90). The emitted radiation is not particularly limited, but examples include particle beams such as alpha rays, beta rays, and neutron beams, and electromagnetic waves such as X-rays and gamma rays. Furthermore, the liquid to be detected, L1, usually contains the nuclide in a dissolved or dispersed state. The portion of the liquid to be detected, excluding the nuclide, is not particularly limited as long as it is a liquid, but examples include aqueous solutions (such as brine) of treated water from a nuclear plant, seawater, or brackish water, although freshwater may also be used.

[0012] The monitoring device 1 for measuring the concentration of radioactive substances in the detection liquid L1 as described above includes a flow path 10, a phosphor 20, a light detection unit 30, a counter unit 40, an analysis unit 50, and a control unit 60. These are as follows.

[0013] <Flow path 10> The flow path 10 is a flow path for allowing the detection liquid L1 to flow through, and communicates with a supply path 11 and a discharge path 12 of the detection liquid L1. The supply path 11 and the discharge path 12 each have a valve and can adjust the supply amount and the discharge amount. Thereby, the flow path 10 can adjust the liquid amount of the detection liquid L1 in the flow path 10 by adjusting either the supply amount of the detection liquid L1 from the supply path 11 or the discharge amount of the detection liquid L1 from the discharge path 12.

[0014] The connection positions of the supply path 11 and the discharge path 12 to the flow path 10 shall be positions where the liquid amount of the detection liquid L1 in the flow path 10 can be adjusted. For this reason, for example, the discharge path 12 is preferably provided in contact with the bottom surface 10a of the flow path 10, thereby enabling the liquid amount of the detection liquid L1 in the flow path 10 to be adjusted within a range of zero or more. Also, the connection position of the supply path 11 to the flow path 10 is not particularly limited, but it is preferable that the supply port of the detection liquid L1 is arranged close to the bottom surface 10a of the flow path 10. Thereby, the mixing of bubbles into the detection liquid L1 due to the fall of the detection liquid L1 is prevented, and the measurement accuracy of the concentration of radioactive substances is improved.

[0015] Also, the flow path 10 shall be configured such that at least the wall surface (here, the bottom surface 10a) where the phosphor 20 described below is arranged is made of a material that transmits radiation. Furthermore, the flow path 10 shall be made of a material that does not have flexibility. Thereby, by adjusting the liquid amount of the detection liquid L1 in the flow path 10, the liquid level height [h] of the detection liquid L1 in the flow path 10 is controlled.

[0016] Note that the size of the flow path 10 is assumed to be a shape (size) considering the range of the radiation handled here. For example, in the case of α-rays and β-rays, since the range is short, a small flow path 10 can be used.

[0017] <Phosphor 20> The phosphor 20 emits photons by interacting with the radiation (e.g., β-rays) emitted from the flow path 10. Such a phosphor 20 is, for example, disposed on the bottom surface 10a side of the flow path 10 and provided in contact with the outer wall of the flow path 10, so that β-rays can be detected efficiently. However, the phosphor 20 does not necessarily have to be in contact with the flow path 10. For example, an air layer or a light-transmitting resin such as a light guide may be disposed between the phosphor 20 and the flow path 10.

[0018] Such a phosphor 20 is not particularly limited as long as it is composed of a composition that exhibits luminescence. Luminescence includes, for example, photoluminescence by light such as ultraviolet rays, radioluminescence by radiation, cathodoluminescence by an electron beam, electroluminescence by an electric field, and chemiluminescence by a chemical reaction.

[0019] Specific examples of the phosphor 20 include, for example, NaI, CsI, LiI, SrI2, Bi4Ge3O as the base material 12 、Bi4Si3O 12 、CdWO4, PbWO4, ZnS, CaF2, LuAG, LuAP, Lu2O3, Y3Al5O 12 、YAlO3, Lu2SiO5, LYSO, Y2SiO5, Gd2SiO5, BaF2, CeF3, CeBr3, CsF, LiF, Gd2O2S, LaBr3, CeBr3, Gd3Al2Ga3O 12Light-transmitting materials such as Cs2LiYCl6, Cs2HfI6, ScTaO4, LaTaO4, LuTaO4, GdTaO4, YTaO4, InBO3, Y2O2S, ZnSiO4, and sialon phosphors can be used. In addition, the matrix material made of such light-transmitting materials may contain rare earth elements such as La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, or elements or ions such as Tl, Na, Ag, W, Cu, Al, Au, Mn, CO3, or fluorescent materials.

[0020] More specific examples of phosphor 20 include InBO3:Tb, InBO3:Eu, ZnS:Cu, ZnS:Al, ZnS:Au, Y2O2S:Eu, Y2O2S:Tb, and ZnSiO4:Mn. Furthermore, the valency of the elemental ions contained in phosphor 20 is not particularly limited as long as it is usable for luminescence; for example, monovalent, divalent, trivalent, tetravalent, etc., can be used. In addition, as phosphor 20, for example, organic phosphors such as complexes, organic compounds, and plastic scintillators can also be used.

[0021] The above-described method for producing the phosphor 20 can employ, for example, the floating zone method, the Czochralski method (pulling method), the micro-pulling method, the Bridgman method, the Bernoulli method, or organic synthesis.

[0022] <Photodetector 30> The photodetector 30 is a detector that converts photons transmitted from the phosphor 20 into electrical pulse signals. Such a photodetector 30 is not particularly limited as long as it can convert photons into electrical pulse signals, and can employ, for example, a photomultiplier tube, a photodiode, an avalanche photodiode, an image sensor, etc.

[0023] <Counter section 40> The counter unit 40 is a measuring device that counts the electrical pulse signal input from the photodetector unit 30 as radiation generated within the flow path. The counter unit 40 outputs the counted value of the electrical pulse signal to the analysis unit 50. For example, a digital signal processor or a multi-channel analyzer can be used as such a counter unit 40.

[0024] <Analysis section 50> The analysis unit 50 is connected to the counter unit 40 and is a device that calculates the concentration of radioactive material contained in the detected liquid L1 based on the measured values ​​output from the counter unit 40, and is composed of a computer. The computer may be a personal computer equipped with a CPU (Central Processing Unit), memory such as ROM (Read Only Memory) and RAM (Random Access Memory), and a network interface as needed. Such an analysis unit 50 includes the functional units of a storage unit 51, a background correction unit 52, and a concentration calculation unit 53.

[0025] [Storage section 51] The memory unit 51 maintains a database of [count rate-concentration] that associates the count rate of the electrical pulse signal based on the output from the counter unit 40 with the concentration of the radioactive substance in the detected liquid L1. The count rate is the count value per unit time, and hereafter, the count rate based on the count value output from the counter unit 40 will simply be referred to as the count rate obtained from the counter unit 40 or the measured value of the count rate.

[0026] [Background correction unit 52] The background correction unit 52 corrects the background value based on the volume of the detected liquid L1 in the flow path 10 and the count rate obtained from the counter unit 40. Here, the background value is the count rate of radiation emitted from radioactive material attached to the inner wall of the flow path 10, which is the count rate caused by contamination in the flow path 10 (contamination-induced count rate), among the count rates obtained from the counter unit 40.

[0027] Such a background correction unit 52 is intended to store data on the liquid volume dependence of the count rate caused by radioactive material adhering to the inner wall of the flow path 10, i.e., the count rate caused by contamination. The background correction unit 52 is also intended to store data on the liquid volume dependence of the count rate caused by radioactive material in the detected liquid L1 within the flow path 10. Note that the liquid volume in the liquid volume dependence of each data refers to the volume of the detected liquid L1 within the flow path 10.

[0028] Figure 2 illustrates the relationship between the liquid volume in the channel 10 and the count rate caused by contamination, showing two states: (1) when the volume of the detected liquid L1 in the channel 10 is low, and (2) when the volume of the liquid is high. As shown in Figure 2, in the state of low liquid volume (1), radiation r1 to r3 emitted from radioactive materials C1 to C3 attached as contaminants to the inner wall of the channel 10 reaches the phosphor 20 without being attenuated by the detected liquid L1. In contrast, in the state of high liquid volume (2), radiation r1 and r3 emitted from radioactive materials C1 and C3 attached to the inner wall of the channel 10 at a position far from the phosphor 20 are shielded by the detected liquid L1 before reaching the phosphor 20.

[0029] Therefore, the count rate due to contamination in the flow path 10 depends on the volume of liquid in the flow path 10. More specifically, the count rate due to contamination depends on the liquid level height [x] obtained from the volume of liquid, and the higher the liquid level height [x], the lower the count rate, and this relationship can be expressed as a logarithmic function.

[0030] Therefore, the background correction unit 52 shown in Figure 1 stores data on the liquid volume dependence of the count rate due to contamination and the liquid volume dependence of the count rate due to radioactive material in the detected liquid L1 in the flow path 10, in order to correct the background value. The liquid volume is the volume of the detected liquid L1 in the flow path 10. This data is for each device, each nuclide, and each type of radiation being measured. The background correction unit 52 calculates the background value based on the stored data and the measured count rate obtained from the counter unit 40.

[0031] Such a background correction unit 52 has a program for calculating background values ​​and performs the calculation of background values ​​according to this program. The procedure for calculating background values ​​by the background correction unit 52 will be explained in detail in the following method for monitoring radioactive materials.

[0032] [Concentration calculation unit 53] The concentration calculation unit 53 calculates the concentration of the radioactive substance contained in the detected liquid L1 based on the [counting rate - concentration] database held by the storage unit 51, the counting rate obtained from the counter unit 40, and the background value calculated by the background correction unit 52. The procedure for calculating the concentration of the radioactive substance by the concentration calculation unit 53 will be explained in detail in the following section on the radioactive substance monitoring method.

[0033] <Control Unit 60> The control unit 60 adjusts the flow rate of the detected liquid L1 in the flow path 10 by controlling the valves of the supply path 11 and the discharge path 12. In particular, the control unit 60 changes the amount of liquid in the flow path 10 by controlling at least one of the valves of the supply path 11 and the discharge path 12 at a predetermined timing. The timing at which the amount of liquid in the flow path 10 is changed is the timing at which the background correction unit 52 calculates the background value.

[0034] Furthermore, this control unit 60 is composed of a computer and may be integrated with the computer that constitutes the analysis unit 50 described earlier.

[0035] =Methods for monitoring radioactive materials= Next, the method for monitoring radioactive materials using the monitoring device 1 described above will be explained. Figure 3 is a flowchart of the method for monitoring radioactive materials according to the embodiment. This flowchart shows the procedure for correcting background values ​​in the monitoring of radioactive materials. This procedure is performed by the CPU of the analysis unit 50 of the monitoring device 1 shown in Figure 1 reading a predetermined program from ROM and expanding it into RAM, and then the CPU executing the expanded program. The method for monitoring radioactive materials will be explained below in accordance with the flowchart in Figure 3, with reference to Figure 1 and other figures.

[0036] First, in monitoring radioactive materials, the control unit 60 controls the valves provided in the supply passage 11 and the discharge passage 12 to set the volume of the liquid to be detected L1 in the flow path 10 to the first liquid level height [x1]. In this state, the concentration calculation unit 53 obtains the count rate measurement value from the counter unit 40 and calculates the concentration of radioactive material in the liquid to be detected L1, thereby continuing to monitor the radioactive material in the liquid to be detected L1. During this monitoring, background value correction is performed as shown in the flowchart of Figure 3.

[0037] <Background value correction> [Step S101] In step S101, the control unit 60 determines whether it is time to correct the background value. The control unit 60 determines that it is time for correction (YES) if it has been continuously monitoring the concentration of radioactive material in the detected liquid L1 for, for example, 24 hours, and proceeds to the next step S102.

[0038] [Step S102] In step S102, the control unit 60 adjusts the liquid volume in the flow path 10 to a volume sufficient to correct the background value. At this time, the control unit 60 controls the valves provided in the supply path 11 and the discharge path 12 to adjust at least one of the amount of detected liquid L1 supplied from the supply path 11 and the amount of detected liquid L1 discharged from the discharge path 12. This changes the liquid volume of detected liquid L1 in the flow path 10 to a second liquid level [x2] which is different from the first liquid level [x1] during monitoring.

[0039] The liquid level [x] of the liquid to be detected L1 within the flow path 10 depends on the volume of the liquid to be detected L1 within the flow path 10. Therefore, the liquid level [x] of the liquid to be detected L1 can be calculated based on the volume of liquid in the flow path 10 adjusted by the amount of liquid to be detected L1 supplied from the supply path 11 and the amount of liquid to be detected L1 discharged from the discharge path 12. Consequently, it is not necessary to directly measure the liquid level [x].

[0040] [Step S103] In step S103, the background correction unit 52 obtains a measured value of the counting rate from the counter unit 40 with the changed liquid volume.

[0041] [Step S104] In step S104, the background correction unit 52 determines whether or not it has completed acquiring the measured values ​​for correcting the background value. At this time, if the background correction unit 52 has acquired two counting rates corresponding to two different liquid level heights [x1] and [x2] from the counter unit 40, it determines that it has completed acquiring the measured values ​​for correcting the background value and proceeds to step S105. Otherwise, it returns to step S102, changes the liquid volume in the flow path 10 in step S102, and continues with the subsequent steps.

[0042] [Step S105] In step S105, the background correction unit 52 calculates a background value based on the two count rate measurements obtained from the counter unit 40, the liquid volume in the flow path 10 at the time these measurements were obtained (liquid level [x1], [x2]), and the data it holds. The measured count rate at the first liquid level [x1] is assumed to be the value immediately before adjusting the liquid volume in the flow path 10 in step S102.

[0043] Figure 4 shows the relationship between the liquid volume in the flow path and the count rate in a radioactive material monitoring device, and is a graph showing the count rate against the liquid level height [x] of the flow path 10. The measured value function C(x), shown by the solid line, is a logarithmic function showing the measured value of the count rate obtained from the counter unit 40, and shows the dependence of the measured value on the liquid volume.

[0044] Furthermore, the background value function Bg(x), shown by the dashed line, represents the background value of the measured value C(x) that is caused by contamination due to radiation from radioactive material adhering to the inner wall of the flow path 10. This background value function Bg(x) is data relating to the liquid volume dependence of the contamination-induced counting rate and is held by the background correction unit 52.

[0045] Furthermore, the objective value function Af(x), shown by the dashed line, represents the objective value of the count rate derived from radiation from the radioactive material in the detected liquid L1. This objective value function Af(x) is data relating to the liquid volume dependence of the count rate caused by the radioactive material in the detected liquid L1 within the flow path 10, and is held by the background correction unit 52.

[0046] Of these, the count rate in the objective value function Af(x) increases with the rise in the liquid level [x] of the detected liquid L1, and the shielding effect in the detected liquid L1 also increases, so it tends to saturate above a certain liquid level [x]. On the other hand, the count rate in the background value function Bg(x), as explained earlier using Figure 2, decreases with the rise in the liquid level [x] of the detected liquid L1, and tends to saturate above a certain surface height [x], with the count rate being maximum when the liquid level [x] = 0. The measured value function C(x) is expressed as the sum of the objective value function Af(x) and the background value function Bg(x). Furthermore, the position in the direction of the count rate of these functions changes depending on the concentration of the radioactive material.

[0047] The objective function Af(x) and background function Bg(x) described above are expressed as logarithmic functions. From this, the background correction unit 52 calculates the position of the objective function Af(x) and background function Bg(x) in the direction of the count rate by solving the simultaneous equations (1) and (2) below, based on the measured values ​​of the count rate at two liquid level heights [x1] and [x2]. Also, in equations (1) and (2), as an example, the liquid level heights [x1]=1 and [x2]=0.2.

[0048]

number

[0049] Based on the above, the background value function Bg(x), i.e., the background value at each liquid level height [x], is calculated.

[0050] Furthermore, since the objective function Af(x) is also calculated here, monitoring to measure the concentration of radioactive material in the detected liquid L1 is not interrupted, as will be shown later.

[0051] [Step S106] Returning to Figure 3, in step S106, the background correction unit 52 updates the background value held in the concentration calculation unit 53 to the background value (background function) calculated in step 105 and terminates the process.

[0052] <Measurement of radioactive material concentration> After the above, the concentration calculation unit 53 calculates the count rate derived from radiation from the radioactive material in the liquid under detection L1 based on the measured count rate obtained from the counter unit 40, the liquid level height [x] at the time the measurement was taken, and the updated background function Bg(x). The liquid level height [x] at this time may be the liquid level height [x2] adjusted in step S102, or it may be any height. Then, based on the calculated count rate, the liquid level height [x] at the time the count rate was measured, and the [count rate-concentration] database held in the storage unit 51, the concentration of the radioactive material in the liquid under detection L1 is calculated. As a result, monitoring of the radioactive material in the liquid under detection L1 can be continued without interruption.

[0053] <Effects of the First Embodiment> According to the first embodiment described above, it is possible to calculate the background value caused by contamination originating from radiation from radioactive materials adhering to the inner wall of the flow path 10 without interrupting monitoring. This simplifies the correction of the background value, and for example, frequent correction can improve the measurement accuracy of the radioactive material concentration in the detected liquid L1. Furthermore, by accurately correcting the background value at a high frequency, an accurate radioactive material concentration can always be obtained, thus extending the replacement cycle of the part of the flow path 10 to which radioactive materials adhere. As a result, the operating cost of the monitoring device 1 can be reduced.

[0054] Furthermore, the data relating to the liquid level height dependence of the counting rate of the background correction unit 52 described above is assumed to be data for each device, each nuclide, and each type of radiation being measured. When there is variation in the concentration distribution of radioactive material adhering to each part of the inner wall of the flow path 10, it is preferable to obtain logarithmic function data based on experiments that take this variation into account. This makes it possible to calculate the background value more accurately and to further improve the measurement accuracy of the concentration of radioactive material.

[0055] Furthermore, in step S101 described above, as an example, it was determined that the timing for background value correction was YES if the concentration of radioactive material in the detected liquid L1 was continuously monitored for 24 hours. However, since the background value can be calculated without interrupting monitoring, by configuring the system to calculate the background value more frequently, it becomes possible to perform monitoring with background value correction in near real time.

[0056] Furthermore, in step S102 shown in Figure 3, the flow of liquid into the channel 10 may be stopped, and the amount of liquid in the channel 10 may be adjusted to 0, i.e., liquid level [x2] = 0. In this case, the objective value function Af(x) and the background value function Bg(x) can be calculated using only the measured count rate at liquid level [x2] = 0. However, in this case, the measurement of the concentration of radioactive material in the liquid to be detected L1 will be interrupted. Therefore, monitoring of radioactive material will resume when a predetermined amount of liquid is supplied into the channel 10.

[0057] <Variation> Figure 5 is a diagram showing the main components of a radioactive material monitoring device according to a modified example of the first embodiment. As shown in Figure 5, the placement of the phosphor 20 relative to the flow path 10 may be along the side wall 10b of the flow path 10, and the other configurations are the same.

[0058] Figure 5 illustrates the relationship between the liquid volume in the channel 10 and the contamination-induced count rate, showing two states: (1) when the volume of the detected liquid L1 in the channel 10 is low, and (2) when the volume of the liquid is high. As shown in Figure 5, in the low-volume state (1), radiation r1~r3',r3'' emitted from radioactive materials C1~C3',C3'' attached as contaminants to the inner wall of the channel 10 reaches the phosphor 20 without being attenuated by the detected liquid L1. In contrast, in the high-volume state (2), radiation r1,r3'' emitted from radioactive materials C1,C3'' attached to the inner wall of the channel 10 at a position far from the phosphor 20 is shielded by the detected liquid L1 before reaching the phosphor 20.

[0059] Therefore, the count rate due to contamination in the flow path 10 depends on the liquid level height [x] obtained from the liquid volume in the flow path 10, and the higher the liquid level height [x], the lower the count rate, and this relationship can be expressed as a logarithmic function, just as in the configuration of the first embodiment.

[0060] Therefore, a monitoring method can be implemented using the same analysis unit 50 as described in the first embodiment, with the addition of the same background value correction. This will allow the same effects as in the first embodiment to be obtained.

[0061] ≪Second Embodiment≫ Figure 6 is a diagram showing the configuration of the radioactive material monitoring device 2 according to the second embodiment. The difference between the monitoring device 2 of the second embodiment shown in Figure 6 and the monitoring device 1 of the first embodiment shown in Figure 1 is that multiple discharge passages 12 are provided at different heights in the flow path 10. The other configurations are the same, so a description of the similar configurations is omitted here.

[0062] Each discharge passage 12 has a valve, which can be opened and closed by the control unit 60. In this case, the control unit 60 changes the liquid level [x] of the detected liquid L1 in the flow path 10 by controlling the valves of the multiple discharge passages 12. In other words, the control unit 60 can adjust the liquid level (liquid level [x]) of the detected liquid L1 in the flow path 10 to a predetermined value by deciding which discharge passages 12 at which heights are opened and which are closed.

[0063] In this case, the background correction unit 52 determines the liquid level [x] of the detected liquid L1 and calculates the background value based on which heights of the discharge passages 12 the control unit 60 has opened and which heights of the discharge passages 12 have closed.

[0064] As a result, the control unit 60 can adjust the volume (liquid level [x]) of the detected liquid L1 in the flow path 10 to a predetermined value without having to finely control the supply amount from the supply path 11 and the discharge amount from the discharge path 12, and without having to measure the liquid level [x] in the flow path 10. This also makes it possible to easily calculate the background value.

[0065] ≪Third Embodiment≫ Figure 7 is a diagram showing the configuration of the radioactive material monitoring device 3 according to the third embodiment. The difference between the monitoring device 3 of the third embodiment shown in Figure 7 and the monitoring device 1 of the first embodiment shown in Figure 1 is that it has a liquid level measuring unit 70. The other configurations are the same, so a description of the similar configurations is omitted here.

[0066] The liquid level measurement unit 70 is not limited in its measurement method as long as it can measure the liquid level height [x] of the liquid to be detected L1 in the flow path 10. For example, pressure type, guide pulse type, capacitance type, float type, differential pressure type, radio wave type, and ultrasonic type can be used. In addition, the liquid level measurement unit 70 may be a camera or a mass meter. Furthermore, the liquid level measurement unit 70 does not necessarily need to be in contact with the flow path 10, and both contact type and non-contact type can be used.

[0067] In this case, the background correction unit 52 corrects the background value based on the liquid level height [x] of the liquid to be detected L1 in the flow path 10, as measured by the liquid level measurement unit 70. This enables correction of the background value based on an accurate liquid level height [x], thereby improving the measurement accuracy of the radioactive material concentration in the liquid to be detected L1. Furthermore, in this configuration, even if the liquid level height [x] of the liquid to be detected L1 in the flow path 10 changes unintentionally, the background correction unit 52 can still calculate the background value.

[0068] ≪Fourth Embodiment≫ Figure 8 is a diagram showing the configuration of the radioactive material monitoring device 4 according to the fourth embodiment. The difference between the monitoring device 4 of the fourth embodiment shown in Figure 8 and the monitoring device 1 of the first embodiment shown in Figure 1 is that multiple phosphors 20 are arranged along multiple different outer wall surfaces that constitute the flow path 10. The other configurations are the same, so a description of the similar configurations is omitted here.

[0069] The multiple phosphors 20 are arranged, for example, along the bottom surface 10a and the top surface 10c of the channel 10, facing each other on either side of the channel 10, as shown in the figure. Alternatively, the multiple phosphors 20 may be provided on the side of the channel 10 with respect to the bottom surface 10a, or on the side of the channel 10 with respect to the top surface 10c, or on the side facing each other on either side of the channel 10. While these phosphors 20 can efficiently detect beta rays by being in contact with the outer wall of the channel 10, they do not necessarily need to be in contact with the channel 10. As explained in the first embodiment, an air layer or a light-transmitting resin such as a light guide may be placed between the phosphors 20 and the channel 10.

[0070] As described above, by arranging multiple phosphors 20 on different surfaces of the channel 10, radiation from radioactive materials attached to the inner wall of the channel 10 can be efficiently detected. This makes it possible to calculate a highly accurate background value and improve the accuracy of measuring the concentration of radioactive materials in the liquid L1 to be detected.

[0071] Furthermore, this fourth embodiment can be combined with the second or third embodiment, and the respective effects can be obtained by combining them.

[0072] It should be noted that the present invention is not limited to the embodiments and modifications described above, and includes a variety of further modifications. For example, the embodiments described above are described in detail for the purpose of clearly illustrating the present invention, and are not necessarily limited to those having all the configurations described. Furthermore, it is possible to replace parts of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add configurations from other embodiments to the configuration of one embodiment. In addition, it is possible to add, delete, or replace parts of the configuration of each embodiment with other configurations. [Explanation of symbols]

[0073] 1, 2, 3, 4… Monitoring devices 10…flow channel 10a...Bottom 10b…Side wall 10c... Top surface 11...Injection path 12...Discharge path 20...Phosphor 30... Light detection unit 40... Counter section 50…Analysis department 51...Storage section 52... Background correction section 53...Concentration calculation section 60... Control Unit 70…Liquid level measurement part C1,C2,C3,C3',C3"…Radioactive material L1...Detected liquid r1,r2,r3,r3',r3”…Radiation

Claims

1. A channel through which the liquid to be detected is passed, A counter unit that counts signals based on radiation generated within the aforementioned flow path, The system includes an analysis unit that calculates the concentration of radioactive material in the detected liquid based on the radiation count rate obtained from the counter unit, The aforementioned analysis unit, A background correction unit calculates a background value from the count rate that is attributable to radioactive material adhering to the inner wall of the flow path, based on the volume of the liquid to be detected in the flow path and the count rate obtained from the counter unit. The system includes a concentration calculation unit that calculates the concentration of radioactive material in the detected liquid based on the background value calculated by the background correction unit and the counting rate obtained from the counter unit. A device for monitoring radioactive materials.

2. The background correction unit stores data relating to the liquid volume dependence of the count rate due to radioactive material adhering to the inner wall of the flow path and the count rate due to radioactive material in the detected liquid within the flow path, and calculates the background value based on the count rate obtained from the counter unit and the aforementioned data. A monitoring device for radioactive materials according to claim 1.

3. The background correction unit calculates the background value based on multiple counting rates obtained from the counter unit at multiple time points in time when the volume of the liquid to be detected in the flow path is different. The radioactive material monitoring device according to claim 2.

4. The background correction unit calculates the background value based on the counting rate obtained from the counter unit when the volume of the detected liquid in the flow path becomes zero. The radioactive material monitoring device according to claim 2.

5. The background correction unit uses the liquid level height of the liquid to be detected in the flow path as the volume of the liquid to be detected in the flow path. A monitoring device for radioactive materials according to claim 1.

6. The control unit changes the amount of liquid in the flow path by controlling at least one of the amount of liquid to be detected supplied to the flow path and the amount of liquid to be detected discharged from the flow path at a predetermined timing. The background correction unit calculates the background value when the amount of liquid in the flow path changes due to control by the control unit. A monitoring device for radioactive materials according to claim 1.

7. The aforementioned flow path has a plurality of discharge passages that communicate at different heights, The control unit controls the valves of the plurality of discharge passages, thereby changing the liquid level height as the liquid volume of the detected liquid in the flow path. The radioactive material monitoring device according to claim 6.

8. The system includes a liquid level measuring unit for measuring the liquid level height of the liquid to be detected within the flow path, The background correction unit calculates the background value based on the liquid level before and after the change in liquid level, and the counting rate obtained from the counter unit, when the liquid level obtained from the liquid level measurement unit changes. A monitoring device for radioactive materials according to claim 1.

9. A phosphor that emits photons in response to radiation generated from within the aforementioned channel, The system comprises a photodetector that converts photons emitted from the phosphor into electrical pulse signals that are counted in the counter unit, The phosphor is arranged along the multiple outer wall surfaces that constitute the flow path. A monitoring device for radioactive materials according to claim 1.

10. A monitoring method for radioactive materials, comprising a channel through which a liquid to be detected flows, a counter unit that counts signals based on radiation generated within the channel, and an analysis unit that calculates the concentration of radioactive material in the liquid to be detected based on the radiation count rate obtained from the counter unit, The background correction unit of the analysis unit calculates the background value from the count rate that is attributable to radioactive material adhering to the inner wall of the flow path, based on the volume of the liquid to be detected in the flow path and the count rate obtained from the counter unit. The concentration calculation unit of the analysis unit calculates the concentration of the radioactive substance in the detected liquid based on the background value and the counting rate obtained from the counter unit. Methods for monitoring radioactive materials.

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