Self-powered detector

Abstract

By having a fast response, this enables the realization of a self-powering detector capable of detecting radiation with high sensitivity even in low-dose-rate environments. [Solution] The device comprises an emitter 11, a collector 14 positioned outside the emitter 11, an insulating material container 12 that insulates the emitter 11 and the collector 14, a cable 15 having a conductor 13 connected to the emitter 11 and insulating material 15a covering the conductor 13, a current measuring device 20 that measures the current value flowing between the cable 15 and the collector 14, and an electron supply unit 21 that supplies electrons to one or more of the insulating material 15a constituting the insulating material container 12 and the cable 15.

Description

Technical Field

[0001] The present invention relates to a self-powered detector for monitoring dose rate.

Background Art

[0002] Patent Document 1 describes a self-powered detector including a metal emitter, a collector, a current measurement unit, a conductor electrically connecting the emitter and the current measurement unit, a housing frame housing the current measurement unit, and an electron supply unit for supplying electrons to the current measurement unit. The emitter, collector, current measurement unit, conductor, housing frame, and electron supply unit are insulated from the ground, and the current measurement unit measures the current flowing between the electron supply unit and the emitter.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The self-powered detector as described in Patent Document 1 above is a detector that measures the radiation dose by measuring the current flowing according to the change in the number of electrons in the substance constituting the detector without requiring the application of voltage.

[0005] Self-powered detectors are called self-powered gamma-ray detectors (SPGD) and self-powered neutron detectors (SPND) for each type of radiation to be measured. In this specification, mainly SPGD will be taken as an example for explanation, but the basic concept and structure are the same for SPND as well.

[0006] Self-powered gamma-ray detectors measure the current generated by the decrease in the number of electrons in the emitter, which occurs when electrons are ejected from the emitter due to gamma-ray irradiation. Similarly, self-powered neutron detectors measure the current generated by the change in the number of electrons in the emitter, which occurs when electrons are emitted from the emitter due to nuclear reactions between the emitter material and neutrons. Decay phenomena such as beta decay can also be used to increase or decrease the number of electrons in the emitter.

[0007] Thus, self-powered gamma-ray detectors and self-powered neutron detectors operate on similar principles and have almost identical structures. The differences between them are mainly due to differences in the emitter material.

[0008] However, no material exists that interacts only with gamma rays or only undergoes nuclear reactions with neutrons. Therefore, when a material that readily emits electrons through interaction with gamma rays is used as the emitter, it functions as a self-powered gamma-ray detector, and when a material that readily emits electrons through nuclear reactions with neutrons is used as the emitter, it functions as a self-powered neutron detector.

[0009] The current output resulting from interactions with gamma rays or nuclear reactions with neutrons inherently possesses a fast response.

[0010] When considering the application of self-power detectors to power monitoring in nuclear reactors, one possible method is to monitor the power by measuring neutrons or gamma rays generated in accordance with the reactor's output.

[0011] In such cases, immediate responsiveness is required for measurements in order to generate signals for scrams and alarms in response to reactor output.

[0012] However, after diligent research by the inventors, it became clear that electrons generated in the emitter and collector are stopped by the insulating material inside the detector and the insulating material inside the cable connecting the detector and the current measuring instrument, and that a time delay occurs in the output current value until the electrons flowing into the insulating material and the electrons flowing out of the insulating material reach an equilibrium state.

[0013] This is because the influence of electron inflow and outflow into the insulating material on the output current value of the SPGD or SPND is so weak that it cannot be ignored. However, although the factors causing the time delay in the output current value until equilibrium is reached are not fully understood, it is assumed that they are as follows.

[0014] (1) Electrons become trapped in lattice defects within the insulator, causing them to remain stationary within the insulator. (2) Until the number of electrons trapped in lattice defects in the insulator (inflow of electrons into the insulator) and the number of electrons trapped in the insulator that are ejected out of the insulator due to interaction with gamma rays and neutrons (outflow of electrons from the insulator) reach equilibrium, the current value measured by the ammeter will be lower than the true dose by the amount of electrons that are trapped.

[0015] Therefore, the inventor conceived that the above problem could be solved by using the state of equilibrium as the initial state, since the time response of the output current value to gamma rays, etc., is immediate when the electron inflow and outflow reach equilibrium. Thus, the inventor completed the present invention.

[0016] The objective of the present invention is to realize a self-powering detector that has high-speed response capabilities and can detect radiation with high sensitivity even in low-dose-rate environments. [Means for solving the problem]

[0017] The present invention includes a plurality of means for solving the above problems. For example, it includes an emitter, a collector disposed outside the emitter, an insulating material for insulating the emitter and the collector, a cable having a core wire connected to the emitter and a cable insulating material covering the periphery of the core wire, a current measurement unit for measuring the value of the current flowing between the cable and the collector, and an electron supply unit for supplying electrons to any one or more of the insulating material and the cable insulating material constituting the cable.

Advantages of the Invention

[0018] According to the present invention, by having a high-speed response, it is possible to realize a self-output type detector that can detect radiation with high sensitivity even in a low dose rate environment. Problems, configurations, and effects other than those described above will be clarified by the description of the following embodiments.

Brief Description of the Drawings

[0019] [Figure 1] It is a schematic cross-sectional view showing the basic concept of the self-output type detector of Example 1. [Figure 2] It is a schematic cross-sectional view showing the basic concept of the self-output type detector of Modified Example 1 of Example 1. [Figure 3] It is a schematic cross-sectional view showing the basic concept of the self-output type detector of Modified Example 2 of Example 1. [Figure 4] It is a schematic cross-sectional view showing the basic concept of the self-output type detector of Modified Example 3 of Example 1. [Figure 5] It is a schematic cross-sectional view showing the basic concept of the self-output type detector of Example 2. [Figure 6] It is a schematic view showing an example of the output signal of the self-output type detector of Example 2.

Modes for Carrying Out the Invention

[0020] Hereinafter, an embodiment of the self-output type detector of the present invention will be described with reference to the drawings. In the drawings used in this specification, the same or corresponding components are denoted by the same or similar reference numerals, and repeated descriptions of these components may be omitted.

[0021] <Example 1> Example 1 of the self-output type detector of the present invention will be described with reference to FIGS. 1 to 4. FIG. 1 is a schematic diagram showing the basic conceptual configuration of the self-output type detector 1 of Example 1. FIG. 2 is a schematic diagram showing the basic conceptual configuration of the self-output type detector with a function of controlling the amount of electron supply. FIG. 3 is a schematic diagram showing the basic conceptual configuration of the self-output type detector with a function of monitoring the amount of electron supply and controlling the amount of electron supply. FIG. 4 is a schematic diagram showing the basic conceptual configuration of the self-output type detector capable of switching the electron supply timing.

[0022] The self-output type detector 1 shown in FIG. 1 is composed of an emitter 11, an insulating material container 12, a conducting wire 13, a collector 14, a cable 15, a housing 16, a current measuring device 20, an electron supply unit 21, an output unit 26, etc.

[0023] The emitter 11 is a member made of a metal such as lead (Pb), and is enclosed in an internal space provided in the insulating material container 12 at the center of the self-output type detector 1. This emitter 11 is dedicated to detecting either gamma rays or neutrons, and is electrically insulated from the collector 14 by the insulating material container 12 or the like. In this embodiment, the emitter 11 will be described in the form for gamma rays. The emitter 11 is electrically connected to the conducting wire 13 of the cable 15.

[0024] The collector 14 is provided outside the emitter 11 and the insulating material container 12, and is a cylindrical member made of a metal different from the emitter 11, and is electrically connected to the shield wire 15b of the cable 15. Note that it does not necessarily have to be made of metal and may be non-metal, but when the electron supply unit 21 described later is a voltage applying device, it is desirable that a part thereof contains metal.

[0025] The insulating material container 12 is provided between the emitter 11 and the collector 14, and insulates the emitter 11 and the collector 14.

[0026] The conductor 13 is the core wire of the cable 15 and is electrically connected to the emitter 11. Outside the housing 16, it is covered with insulating material 15a. The cable 15 may be a coaxial cable or an MI cable. The cable 15 is electrically connected to the current measuring device 20.

[0027] The housing 16 is a metal component that covers the outer periphery of the self-output type detector 1, excluding the area where the cable 15 is located or the part of the collector 14.

[0028] The current measuring device 20 measures the current flowing between the cable 15 and the collector 14, and calculates the gamma-ray intensity (neutron intensity) from the measured current value.

[0029] The interaction between the emitter 11 and gamma rays causes electrons to be ejected from within the emitter 11, resulting in a shortage. To compensate for this shortage, electrons are supplied from the ground connected to the current measuring device 20. This flow of electrons is measured by the current measuring device 20. Therefore, the current value correlates with the number of electrons ejected by the interaction between the emitter and gamma rays, i.e., the dose rate.

[0030] The electron supply unit 21 supplies electrons to one or more of the insulating material 15a constituting the insulating material container 12 and the cable 15. One means of supplying electrons is, for example, voltage application using a voltage application device.

[0031] In this case, for the insulating material container 12, electrons are supplied to the interior of the insulating material container 12 by tunneling current when a high voltage is applied, either by connecting the emitter 11 to the anode and the collector 14 to the cathode, or by connecting the collector 14 to the anode and the emitter 11 to the cathode. For the insulating material 15a, electrons are supplied to the interior of the insulating material 15a by tunneling current when a high voltage is applied, either by connecting the conductor 13 to the anode and the shield wire 15b to the cathode, or by connecting the shield wire 15b to the anode and the conductor 13 to the cathode.

[0032] The above means is just one example, and the electronic supply means are not limited to this.

[0033] In this embodiment, the self-outputting detector 1 supplies electrons to the insulating material container 12 and insulating material 15a by the electron supply unit 21 in advance before measuring gamma rays, thereby equating the inflow and outflow of electrons in the insulating material container 12 and insulating material 15a, and thus reducing the time delay during measurement compared to conventional methods.

[0034] The output unit 26 outputs and displays at least one of the following: the output value of the current measuring device 20, or the amount of electrons supplied by the electron supply unit 21.

[0035] Figure 2 shows an example configuration of a self-outputting detector 1A in modification 1 of this embodiment. This configuration adds an electron supply control unit 22A that controls the amount of electrons supplied by the electron supply unit 21, and a database 23 that stores the amount of electrons supplied, to the configuration of the self-outputting detector 1 shown in Figure 1.

[0036] The amount of electrons required for electron inflow and outflow to reach equilibrium in the insulating container 12 and insulating material 15a varies depending on the material, dimensions, and connection method of each component constituting the self-output type detector, including the insulating container 12 and insulating material 15a. Furthermore, if there is an excess of electrons, electrons accumulate at the interface between the insulating container 12 and insulating material 15a and metals such as the emitter 11 and collector 14, resulting in a charged state. This generates a current without interaction with gamma rays, leading to the measurement of an apparent current value, which may leave room for improvement in accuracy.

[0037] Therefore, a database 23 is provided that stores the required amount of electrons supplied by the electron supply unit 21, and the electron supply control unit 22A can control the amount of electrons supplied based on the amount of electrons supplied stored in the database 23 by referring to this database.

[0038] The method for controlling the amount of electrons supplied can be, for example, by the applied voltage and application time if the electron supply unit 21 is a voltage application device. In this case, the database 23 stores the specifications of the self-output type detector 1, such as its material and dimensions, the specifications of the cable 15, and the applied voltage and application time corresponding to their connection method. If the electron supply unit 21 is a gamma-ray source as described later, it can be controlled from the relationship between dose and irradiation time. The above control method is just one example, and the electron supply control method is not limited to this.

[0039] Figure 3 shows an example configuration of a self-outputting detector 1B of modification 2 of this embodiment. This configuration adds an electron supply amount monitoring unit 24 that monitors the amount of electrons supplied by the electron supply unit 21, and an electron supply control unit 22B that controls the amount of electrons supplied by the electron supply unit 21 based on the amount of electrons monitored by the electron supply amount monitoring unit 24, to the configuration of the self-outputting detector 1 shown in Figure 1.

[0040] The electron supply monitoring unit 24 monitors the impedance between the emitter 11 and collector 14 of the self-output type detector 1B, which may change due to electron supply, or the supply voltage value and current value of the electron supply unit 21. When the monitored value reaches an indicator value that shows the equilibrium state of electron inflow and outflow to the insulating material container 12 and insulating material 15a, the electron supply is terminated. Conversely, if there is an excess of electrons supplied during supply, the supply amount can be adjusted by performing reverse control. This ensures that electrons are supplied to the insulating material container 12 and insulating material 15a without excess or deficiency.

[0041] While not limited to the self-powered detector 1B shown in Figure 3, the electron supply unit 21 can also be used as a gamma-ray source (or a neutron source if the self-powered detector is for neutron detection) as an electron supply method. By pre-irradiating with gamma rays before measuring the target gamma rays, an equilibrium state of electron inflow and outflow is created in the insulating material container 12 and insulating material 15a. The gamma-ray source for pre-irradiating with gamma rays can be, for example, a standard source, a gamma-ray irradiation device, or a nuclear reactor.

[0042] In this case, the electron supply monitoring unit 24 may monitor the current value of the current measuring device 20. Equilibrium can be achieved by irradiating with gamma rays until the current value reaches an equilibrium state, i.e., a constant output value for a constant dose rate.

[0043] Figure 4 shows an example of the configuration of a self-output type detector 1C in modification 3 of this embodiment. This configuration is one in which the electron supply unit 21C is a voltage application device, and a circuit switching unit 25 is added to switch the electrical connection destination of the conductor 13 between the current measuring device 20 and the electron supply unit 21C.

[0044] In this self-outputting detector 1C, the circuit switching unit 25 sets the electrical connection destination of the conductor 13 to the electron supply unit 21C when supplying electrons to the insulating material container 12 or insulating material 15a before gamma ray detection, and sets the electrical connection destination of the conductor 13 to the current measuring device 20 when gamma ray detection is performed.

[0045] Furthermore, the circuit switching unit 25 of the self-output type detector 1C in modified example 3 shown in Figure 4 can also be applied to the self-output type detector 1A shown in Figure 2 and the self-output type detector 1B shown in Figure 3.

[0046] Next, the effects of this embodiment will be described.

[0047] The self-output type detector 1 of Embodiment 1 of the present invention described above comprises an emitter 11, a collector 14 disposed outside the emitter 11, an insulating material container 12 that insulates the emitter 11 and the collector 14, a cable 15 having a conductor 13 connected to the emitter 11 and insulating material 15a covering the conductor 13, a current measuring device 20 that measures the current value flowing between the cable 15 and the collector 14, and an electron supply unit 21 that supplies electrons to one or more of the insulating material 15a constituting the insulating material container 12 and the cable 15.

[0048] This allows electrons to be supplied in advance to create an equilibrium state of electron inflow and outflow in the insulating material container 12 and insulating material 15a, thereby suppressing the time delay of the output current value compared to conventional detector configurations and enabling a faster response than before.

[0049] Furthermore, by including electron supply control units 22A and 22B that control the amount of electrons supplied by the electron supply unit 21, it is possible to prevent electrons from being supplied more than necessary at times when supply is not needed, thereby improving the accuracy of the measurement results.

[0050] Furthermore, the system includes a database 23 that stores the amount of electrons supplied by the electron supply unit 21. The electron supply control unit 22A controls the amount of electrons supplied based on the amount of electrons supplied stored in the database 23, thereby enabling electron supply tailored to the configuration of the detector and the measurement environment.

[0051] Furthermore, the detector is further equipped with an electron supply amount monitoring unit 24 that monitors the amount of electrons supplied by the electron supply unit 21. The electron supply control unit 22B controls the amount of electrons supplied based on the amount of electrons monitored by the electron supply amount monitoring unit 24, thereby ensuring that electrons are supplied without excess or deficiency, and thus enabling a more responsive detector.

[0052] Furthermore, if the electron supply unit 21C is a voltage application device, a circuit switching unit 25 is provided to switch the electrical connection destination of the conductor 13 between the current measuring device 20 and the electron supply unit 21C, thereby enabling the supply of electrons to the insulating material container 12 and insulating material 15a only at the most appropriate timing.

[0053] Furthermore, by providing an output unit 26 that outputs either the output value of the current measuring device 20 or the amount of electrons supplied by the electron supply unit 21, detection results and other information can be obtained.

[0054] <Example 2> Embodiment 2 of the self-output type detector of the present invention will be described with reference to Figures 5 and 6. Figure 5 is a schematic diagram showing the basic conceptual configuration of the self-output type detector of Embodiment 2. Figure 6 is a schematic diagram showing an example of time-series data of current output in the self-output type detector. Note that the configuration already shown will not be explained.

[0055] The self-outputting detector 1D shown in Figure 5 has an electron supply unit 21D which is either a gamma-ray source or a neutron source. It is configured to be the same as the self-outputting detector 1 described in Example 1, but with the addition of a calculation unit 27 that calculates the time required to reach stable output from the output current value of the current measuring device 20, and a signal correction unit 28 that corrects the output value based on the calculation result of the calculation unit 27. Furthermore, the output unit 26D outputs either the time required to reach stable output or the corrected output value, or at least one of these.

[0056] As described above, the electron supply unit 21D of the self-output type detector 1 in Example 2 is a gamma-ray source, and the electron supply method is irradiation with gamma rays to be measured.

[0057] In the self-output type detectors 1, 1A, 1B, and 1C of Example 1, the measurement was started after the detectors were brought into equilibrium beforehand. However, in the self-output type detector 1D of this embodiment, the calculation unit 27 calculates the time required for the electron inflow and outflow in the insulating material container 12 and insulating material 15a to reach equilibrium based on the transient response of the current value during measurement, the signal correction unit 28 corrects the current value, and outputs the signal to the output unit 26D.

[0058] Figure 6 shows an example of the time variation of current measurement. It is assumed that the dose rate changes instantaneously at the irradiation start point, and then becomes constant thereafter.

[0059] As shown in Figure 6, when the system has not yet reached equilibrium, the current value at the start of irradiation is smaller than the output value at equilibrium, as shown in Figure 6. Furthermore, as the current value during measurement approaches equilibrium, the difference between the output value at equilibrium and the output current value decreases.

[0060] Therefore, the calculation unit 27 calculates the time constant of the transient response of the current from the measured current value until an equilibrium state is reached, thereby calculating the current value at the equilibrium state. The signal correction unit 28 then corrects the detected current value to determine the gamma ray dose. Furthermore, the corrected signal is output by the output unit 26D.

[0061] Furthermore, the calculation unit 27 and the signal correction unit 28 may each be mounted on the current measuring device 20 as a function of the current measuring device 20, or they may be integrated and mounted on the current measuring device 20 as a function of the current measuring device 20; there are no particular limitations.

[0062] The other configurations and operations are substantially the same as those of the self-output type detectors 1, 1A, 1B, and 1C in the aforementioned Example 1, and details are omitted.

[0063] In the self-output type detector 1D of Embodiment 2 of the present invention, substantially the same effects as those of the self-output type detectors 1, 1A, 1B, and 1C of Embodiment 1 described above can be obtained.

[0064] Furthermore, since the electron supply unit 21D is either a gamma-ray source or a neutron source, there is no need to prepare a separate electron supply source, which simplifies the configuration.

[0065] Furthermore, by further including a calculation unit 27 that calculates the time required from the output current value of the current measuring device 20 to a stable output, and a signal correction unit 28 that corrects the output value based on the calculation result of the calculation unit 27, the accuracy of the measurement results can be ensured even when the electron supply unit 21D is either a gamma ray source or a neutron source.

[0066] Furthermore, by providing an output unit 26D that outputs at least one of the following: the time required to achieve stable output, or the corrected output value, it becomes possible to acquire information about the measurement environment during irradiation.

[0067] <Other> Although several embodiments of the present invention have been described above, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of symbols]

[0068] 1, 1A, 1B, 1C, 1D: Self-powering detectors 11: Emitter 12: Insulating container (insulating material) 13: Conductor (core wire) 14: Collector 15: Cable 15a: Insulating material (cable insulation material) 15b: Shielded wire 16: Housing 20: Current measuring device (current measuring unit) 21,21C,21D:Electron supply section 22A, 22B: Electronic supply control unit 23: Database 24:Electronic supply amount monitoring department 25: Circuit switching section 26,26D: Output section 27: Arithmetic section 28: Signal Correction Section

Claims

1. Emitter and, A collector located outside the emitter, An insulating material that insulates the emitter and the collector, A cable having a core wire connected to the emitter and a cable insulating material covering the core wire, A current measuring unit that measures the current value flowing between the cable and the collector, The system includes an electron supply unit that supplies electrons to one or more of the insulating material and the cable insulating material constituting the cable. Self-powering detector.

2. In the self-output type detector according to claim 1, The system further comprises an electron supply control unit that controls the amount of electrons supplied by the electron supply unit. Self-powering detector.

3. In the self-output type detector according to claim 2, The system further includes a database that stores the amount of electrons supplied by the aforementioned electron supply unit, The electron supply control unit controls the amount of electrons supplied based on the amount of electrons stored in the database. Self-powering detector.

4. In the self-output type detector according to claim 2, The system further comprises an electronic supply amount monitoring unit that monitors the amount of electronics supplied by the aforementioned electronic supply unit, The electron supply control unit controls the amount of electrons supplied based on the amount of electrons monitored by the electron supply monitoring unit. Self-powering detector.

5. In the self-output type detector according to claim 1, If the electronic supply unit is a voltage application device, the circuit switching unit further includes a circuit switching unit that switches the electrical connection destination of the core wire between the current measurement unit and the electronic supply unit. Self-powering detector.

6. In the self-output type detector according to claim 1, The electron supply unit is either a gamma-ray source or a neutron source. Self-powering detector.

7. In the self-output type detector according to claim 6, A calculation unit that calculates the time required from the output current value of the current measuring unit to a stable output, The system further includes a signal correction unit that corrects the output value based on the calculation result of the calculation unit. Self-powering detector.

8. In the self-output type detector according to claim 7, The system further includes an output section that outputs at least one of the following: the time required to achieve stable output, or the corrected output value. Self-powering detector.

9. In the self-output type detector according to any one of claims 1 to 7, The system further comprises an output unit that outputs at least one of the following: the output value of the current measuring unit or the amount of electrons supplied by the electron supply unit. Self-powering detector.

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