Self-powered radiation detector, radiation detection system, and reactor power monitoring device

Abstract

To provide a self output type radiation detector, a radiation detection system, and an atomic reactor output monitoring device that can be added to a narrow region in a detector and can detect leakage of an emitter to the outside of a container from a remote position without newly adding a signal line for detection.SOLUTION: A self output type radiation detector 1 includes: a metal emitter 2 for discharging electrons by irradiation of radiation; a heat-resistance container 3 for sealing the metal emitter 2; a metal collector 7 for containing the metal emitter 2 and the heat-resistance container 3 in the inside; a coaxial cable 30 for connecting the metal emitter 2 to a core wire 13 and connecting the metal collector 7 to a metal sheath 14; and a metal accumulator 12 electrically connected to the metal collector 7.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a self-powered radiation detector, which is a type of radiation detector, a radiation detection system including the same, and a reactor power monitoring device. [Background technology]

[0002] As an example of a self-powered detector that can operate even if the emitter melts at high temperatures, Patent Document 1 describes a self-powered detector that has an emitter inside and a collector on the outside, with the emitter and collector insulated from each other. The self-powered detector has an emitter container that encloses the emitter, the emitter container is airtight, and the emitter mass and the volume of the emitter container are adjusted so that when the emitter melts due to high temperatures, the local emitter density inside the emitter container is constant regardless of the orientation of the self-powered detector. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-67312 A Summary of the Invention [Problem to be solved by the invention]

[0004] Self-powered radiation detectors do not require the application of a voltage; they simply measure the current generated when electrons are emitted from the emitter due to radiation. This makes them suitable for installation in relatively harsh environments.

[0005] The emitter material of the self-powered gamma ray detector, which is a type of self-powered detector, is suitable for those that easily emit electrons when irradiated with gamma rays and have a small cross section for nuclear reactions with neutrons. Such elements include Pb and Bi, but these elements have low melting points and may deform or melt in high-temperature environments such as inside a nuclear reactor. Similarly, if an element with a low melting point is used in a self-powered neutron detector to prioritize the emitter characteristics, the emitter may deform or melt.

[0006] Patent Document 1 discloses a self-powered radiation detector that has an emitter inside and a collector on the outside, with the emitter and collector insulated from each other, and that has a heat-resistant container that encloses the emitter and makes the heat-resistant container airtight (liquid-tight).

[0007] According to the self-powered radiation detector described in Patent Document 1, even if the emitter, which has a low melting point, melts in a high-temperature environment, the emitter is held within the container, making it possible to continue measuring radiation.

[0008] However, it is possible that the heat-resistant container may be damaged due to stress beyond what is expected caused by a high-temperature environment or mechanical factors. If the heat-resistant container is damaged, depending on the extent of the damage, the emitter material molten inside may leak out of the container.

[0009] When emitter leaks, the emitter shape inside the detector changes significantly, causing a change in the ratio of the current value to the radiation, i.e., the sensitivity, making it impossible to correctly convert the measured current value into the radiation intensity. In addition, if the leaked emitter leaks further outside the collector, the emitter material will diffuse into the environment outside the detector as a foreign object.

[0010] To avoid such a situation, it is effective to add a means of detecting leakage of emitter material. For example, if it is possible to detect that emitter material has leaked outside the container when a change occurs in the radiation measurement value, it can be determined that the measurement value by the detector is abnormal and not a change in the actual radiation intensity. This is expected to improve the reliability of the measurement value.

[0011] However, if a large detection sensor is added to detect leakage of emitter material outside the vessel, the detector itself will become larger, making it impossible to install the sensor in narrow spaces, such as inside a nuclear reactor, and so a different measure will be necessary.

[0012] Furthermore, installing additional signal lines to receive detection sensor signals from a remote location away from the site would incur costs for installation and costs for adding cable penetrations, leaving room for improvement.

[0013] The present invention has been made to solve the above-mentioned problems, and its purpose is to provide a self-powered radiation detector, a radiation detection system, and a reactor power monitoring device that can be added to a narrow area inside the detector and that can detect emitter leakage outside the vessel from a remote location without adding a new detection signal line. [Means for solving the problem]

[0014] The present invention includes a number of means for solving the above problems. One example of the means is a device comprising: a metallic emitter that emits electrons when irradiated with radiation; a heat-resistant container that seals the emitter; a metallic collector that contains the emitter and the heat-resistant container inside; a signal cable that connects the emitter to a positive electrode and the collector to a negative electrode; and a metal reservoir that is provided on the collector on the side of the internal space that contains the emitter and the heat-resistant container and is electrically connected to the collector. The metal reservoir is disposed around the heat-resistant container. It is characterized by the above. Effect of the Invention

[0015] According to the present invention, it is possible to add a detector to a narrow area inside the detector, and it is possible to detect leakage of the emitter outside the container from a remote position without adding a new detection signal line. Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a configuration diagram of a self-powered radiation detector according to a first embodiment. [Diagram 2] FIG. 11 is a diagram showing a second example of the shape of a metal reservoir as a modified example of the self-powered radiation detector of the first embodiment. [Diagram 3] FIG. 11 is a modification of the self-powered radiation detector of the first embodiment, showing a third example of the shape of the metal reservoir. [Figure 4] FIG. 11 is a diagram showing a fourth example of the shape of a metal reservoir as a modification of the self-powered radiation detector of the first embodiment. [Diagram 5] FIG. 11 is a diagram showing a fifth example of the shape of a metal reservoir as a modification of the self-powered radiation detector according to the first embodiment. [Figure 6] FIG. 11 is a configuration diagram of a detection system according to a second embodiment. [Figure 7] FIG. 11 is a configuration diagram of a detection system according to a third embodiment. [Figure 8] A typical example of the reflection coefficient ρ when TDR measurements are performed on a normal detector and when there is a short circuit in the detector. [Figure 9] FIG. 11 is a configuration diagram of a reactor power monitoring device according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, embodiments of the self-powered radiation detector, radiation detection system, and reactor power monitor 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 description of these components may be omitted.

[0018] In the following explanation, we will mainly explain self-powered gamma ray detectors, but the same applies to self-powered neutron detectors. If a material with a large cross section for neutrons, a low probability of interaction with gamma rays, and a low melting point can be used for the emitter, it is promising as a self-powered neutron detector to be installed in a high-temperature environment such as inside a furnace, as in Example 4 described later.

[0019] <Example 1> A self-powered radiation detector according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 5. FIG.

[0020] First, the overall configuration of the self-powered radiation detector will be described with reference to Fig. 1. Fig. 1 is a configuration diagram of the heat-resistant self-powered radiation detector shown in this embodiment.

[0021] As shown in FIG. 1, a self-powered radiation detector 1 has, at its center, a metal emitter 2 that emits electrons when irradiated with radiation, sealed inside a substantially cylindrical heat-resistant container 3.

[0022] A metal terminal portion 4 and an airtight terminal 6 made of a ceramic base are attached to the bottom of the heat-resistant container 3 .

[0023] The metal collector 7 coaxially contains the metal emitter 2, heat-resistant container 3, and airtight terminal 6 inside. Insulating materials 10, 11 are sandwiched between the heat-resistant container 3 and the metal collector 7 to insulate them from each other and to maintain a constant distance between them. A leading end plug 8 is welded to the top of the metal collector 7, and a trailing end plug 9 is welded to the bottom, sealing the inside of the metal collector 7.

[0024] Furthermore, a coaxial cable 30 consisting of a core wire 13, a metal sheath 14, and an insulating material 15 that provides insulation between the core wire 13 and the metal sheath 14 is attached to the termination plug 9. The core wire 13 is electrically connected to the metal terminal portion 4 of the airtight terminal 6, and the metal sheath 14 is electrically connected to the metal collector 7. The metal emitter 2 is connected to the core wire 13, and the metal collector 7 is connected to the metal sheath 14.

[0025] The metal reservoir 12 is made of metal, and is disposed and fixed vertically below the metallic emitter 2 so as to be electrically connected to the metallic collector 7. The metal reservoir 12 is shaped so as to coaxially cover the lower part of the heat-resistant container 3 and the outside of the airtight terminal 6.

[0026] The operation of the self-powered radiation detector 1 configured in this manner will be described below.

[0027] When the self-powered radiation detector 1 in Fig. 1 is placed in a radiation environment, it is irradiated with radiation and emits electrons from the metallic emitter 2. Some of the emitted electrons are absorbed again by the metallic emitter 2, while the remaining electrons are emitted outside the metallic emitter 2.

[0028] When electrons are emitted, the same amount of electrons as the emitted electrons flow into the metallic emitter 2 via the core wire 13 of the coaxial cable and the metallic terminal portion 4 of the airtight terminal 6 in order to balance the charges.

[0029] Here, the number of electrons emitted per unit time from the metallic emitter 2 is roughly proportional to the amount of radiation irradiated, so the intensity of the irradiated radiation can be measured by measuring this flowing current.

[0030] When the self-powered radiation detector 1 is placed in a high-temperature environment, there is a possibility that the metallic emitter 2 will melt. However, since the molten metallic emitter 2 is sealed in the heat-resistant container 3, its shape will not change significantly, and the number of electrons emitted per unit by radiation will not change significantly, so no special measures need to be taken.

[0031] Next, an operation will be described in the case where the heat-resistant container 3 inside the self-powered radiation detector 1 is damaged due to a high-temperature environment or mechanical factors.

[0032] If the metal emitter 2 sealed inside is melted, and the heat-resistant container 3 is damaged for some reason, the molten metal emitter 2 will leak out of the heat-resistant container 3.

[0033] However, in the self-powered radiation detector 1 of this embodiment, the leaked metal emitter 2 accumulates in the gap between the metal reservoir 12 and the heat-resistant container 3. Since the metal reservoir 12 is electrically connected to the metal collector 7, the metal emitter 2 and the metal collector 7 are electrically short-circuited at this time.

[0034] Then, in order to balance the charge, the metallic emitter 2, which has emitted electrons due to irradiation with radiation, receives a supply of electrons not from the core 13 of the coaxial cable 30 but from the short-circuited metallic collector 7. As a result, no current is generated in the core 13, and the measured current becomes almost zero, thereby detecting a leak.

[0035] On the other hand, in the case of a conventional heat-resistant self-powered radiation detector that does not have a metal reservoir 12, if leakage occurs from the metal emitter 2, the measured radiation value will change depending on the amount of leakage, but in this case it may be difficult to distinguish this from a change in the amount of radiation in the environment.

[0036] In this way, in this embodiment, when a certain amount of leakage occurs from the metallic emitter 2, it shorts out with the metallic collector 7, and the measured radiation value becomes zero, making it possible to detect the leakage separately from changes in the amount of radiation in the environment.

[0037] Next, modified examples of the self-powered radiation detector of this embodiment will be described with reference to Fig. 2 to Fig. 5. Fig. 2 to Fig. 5 are diagrams showing modified examples of the self-powered radiation detector.

[0038] The heat-resistant self-powered radiation detector 1A shown in FIG. 2 differs from the self-powered radiation detector 1 in FIG. 1 in that the shape of the insulating material 10A is different, and the insulating material 10A extends to the vicinity of the terminal plug 9 at the bottom of the detector.

[0039] Further, an insulating spacer 16 for fixing the position of the heat-resistant container 3 is provided below the airtight terminal 6 .

[0040] The metal reservoir 12 is attached in a disk-like shape to the metal collector 7 directly above the terminal end plug 9, i.e., below the heat-resistant container 3, so as not to interfere with the extended insulating material 10 and the insulating spacer 16.

[0041] In the self-powered radiation detector 1A, if the metal emitter 2 leaks from the heat-resistant container 3, it accumulates in the metal reservoir 12A through the gap between the insulating material 10A and the insulating spacer 16, or through the inside of the insulating spacer 16. This causes a short circuit between the metal emitter 2 and the metal collector 7, making it possible to detect the leakage of the metal emitter 2.

[0042] In the configuration example of the self-powered radiation detector 1 shown in Fig. 1, when radiation is irradiated onto the metal reservoir 12 during normal radiation detection, electrons are emitted from the metal reservoir 12 and are absorbed by the nearby metal emitter 2, which may reduce the net number of electrons emitted by the radiation and reduce the generated current value. This means that the sensitivity decreases, but according to the configuration of Fig. 2, the metal reservoir 12A is installed away from the metal emitter 2, so this decrease in sensitivity is minimized and radiation can be measured with higher accuracy.

[0043] 3 shows another heat-resistant self-powered radiation detector 1B in which a metal reservoir 12B made of metal is formed coaxially so as to cover the entire side surface of an insulating heat-resistant container 17 made of insulating material, and is disposed around the insulating heat-resistant container 17. An end of the metal reservoir 12B is electrically connected to a metallic collector 7.

[0044] Since the insulating heat-resistant container 17 is not electrically short-circuited with the metallic collector 7 even when it comes into contact with the metal reservoir 12B, the metallic emitter 2 is not electrically short-circuited in the normal state.

[0045] 3, even if leakage of the metallic emitter 2 occurs in any part of the heat-resistant container 3, a small amount of the metal will come into contact with the metallic reservoir 12B and short-circuit with the metallic collector 7. Therefore, it is possible to detect a smaller leakage than with the configuration of FIG.

[0046] 4 shows a configuration of another heat-resistant self-powered radiation detector 1C in which a metal collector 7 is disposed so as to surround an insulating heat-resistant container 17 made of an insulating material with a gap provided between them. A metal reservoir 12C is formed in a disk shape and attached to the metal collector 7 directly below an airtight terminal 6 that constitutes one end of the insulating heat-resistant container 17.

[0047] If the metal emitter 2 leaks from the side or top of the insulating heat-resistant container 17, it will come into direct contact with the nearby metal collector 7, causing an electrical short circuit between the metal emitter 2 and the metal collector 7, making it possible to detect the leakage. Also, if the leakage occurs from the bottom of the airtight terminal 6, the metal emitter 2 and the metal collector 7 will be short circuited via the metal reservoir 12C, making it possible to detect the leakage.

[0048] 4, the metal reservoir 12C and the insulating material 10 are not required between the insulating heat-resistant container 17 and the metal collector 7, so it is possible to reduce the outer diameter of the detector while still achieving the leakage detection function. This makes it possible to improve the reliability of radiation measurement in narrower spaces.

[0049] The configuration of yet another heat-resistant self-powered radiation detector 1D shown in FIG. 5 is the same as that of the self-powered radiation detector 1C shown in FIG. 4, except that, instead of the disk-shaped metal reservoir 12, an insulating spacer 16 and a metal mesh metal reservoir 18 attached to the upper surface of the spacer 16 are used.

[0050] As described in the configuration example of Figure 2, if there is a metal that emits electrons when exposed to radiation near the metallic emitter 2, the emitted electrons will be absorbed by the metallic emitter 2, reducing the measured current value and decreasing the sensitivity of the radiation measurement.

[0051] In the configuration of Figure 5, the metal reservoir 18 uses a metal mesh instead of a metal plate, which makes it possible to reduce the number of electrons emitted from the metal reservoir 18 while maintaining the detection performance of the leaked metal emitter 2, and to prevent a decrease in the sensitivity of radiation measurement.

[0052] Next, the effects of this embodiment will be described.

[0053] The self-powered radiation detectors 1, 1A, 1B, 1C, and 1D of the first embodiment of the present invention described above include a metal emitter 2 made of metal that emits electrons when exposed to radiation, a heat-resistant container 3 that seals the metal emitter 2, an insulating heat-resistant container 17, a metal collector 7 made of metal that contains the metal emitter 2, the heat-resistant container 3, and the insulating heat-resistant container 17 inside, a coaxial cable 30 that connects the metal emitter 2 to a core wire 13 and connects the metal collector 7 to a metal sheath 14, and metal reservoirs 12, 12A, 12B, 12C, and 18 that are electrically connected to the metal collector 7.

[0054] This makes it possible to detect damage to the heat-resistant container caused by high-temperature environments or mechanical factors from a remote location without making the detector larger or adding a detection signal line. That is, when measuring radiation in a high-temperature, narrow space, measurement failures caused by leakage from the metal emitter 2 can be directly detected, making it possible to distinguish between changes in the original measurement value and malfunctions. Therefore, it is possible to detect the possibility that the metal emitter 2 leaking from the heat-resistant container 3 and insulating heat-resistant container 17 will further leak from the metal collector 7 and become foreign matter and disperse outside the detector.

[0055] <Example 2> Second Embodiment A radiation detection system according to a second embodiment of the present invention will be described with reference to Fig. 6. Fig. 6 is a configuration diagram of the detection system according to the second embodiment of the present invention.

[0056] A radiation detection system 40 shown in Fig. 6 uses the self-powered radiation detector 1 shown in Fig. 1, with its core wire 13 and metal sheath 14 connected to a switch 19. A picoammeter 20, which is a measuring instrument for measuring minute DC currents, and an ohmmeter 21 for detecting short circuits in the self-powered radiation detector 1 are connected to the switch 19, and a control device 22 is also attached.

[0057] In the radiation detection system 40, when measuring radiation, the switch 19 is switched based on a control signal from the control device 22, thereby connecting the core wire 13 and the metal sheath 14 to the picoammeter 20 and measuring the current value corresponding to the radiation, thereby measuring the radiation.

[0058] Furthermore, if a radiation measurement value close to zero is observed, a control signal from the control device 22 causes the switch 19 to connect the core wire 13 and the metal sheath 14 to the resistance meter 21, i.e., connects the resistance meter 21 to the self-powered radiation detector 1.

[0059] As a result, by checking the resistance value of the resistance meter 21, it is possible to check whether there is a short circuit between the metallic emitter 2 and metallic collector 7 of the self-powered radiation detector 1. Therefore, it is possible to determine whether the environmental radiation is actually close to zero, or whether there is a short circuit between the metallic emitter 2 and metallic collector 7, resulting in a radiation measurement value close to zero.

[0060] Alternatively, when measurements are taken in an environment where the radiation level is close to zero, the switch 19 may be switched to the resistance meter 21 side by the control device 22 at regular time intervals to periodically check the normal state of the detection system. This makes it possible to constantly check that the detection system is normal and that the radiation level is close to zero.

[0061] Although Figure 6 describes the case where the self-powered radiation detector 1 shown in Figure 1 is used, the self-powered radiation detector used in this embodiment 2 is not limited to the self-powered radiation detector 1 shown in Figure 1, and any of the self-powered radiation detectors 1A, 1B, 1C, and 1D shown in Figures 2 to 5 can be used.

[0062] The radiation detection system 40 of the second embodiment of the present invention includes the self-powered radiation detectors 1, 1A, 1B, 1C, and 1D of the first embodiment described above, and therefore provides substantially the same effects.

[0063] <Example 3> A radiation detection system according to a third embodiment of the present invention will be described with reference to Figures 7 and 8. Figure 7 is a configuration diagram of the detection system according to the third embodiment of the present invention, and Figure 8 is a diagram showing a typical example of the reflection coefficient ρ when TDR measurement is performed on a normal detector and the reflection coefficient ρ when a short occurs within the detector.

[0064] A radiation detection system 40A shown in Fig. 7 uses the self-powered radiation detector 1 shown in Fig. 1, and connects its core wire 13 and metal sheath 14 to a switch 19. A picoammeter 20, which is a measuring instrument for measuring minute DC currents, and a TDR (time domain reflectometry) measuring instrument 23 for detecting short circuits in the self-powered radiation detector 1 are connected to the switch 19, and a control device 22 is also attached.

[0065] As in the second embodiment, in the radiation detection system 40A, when measuring radiation, the switch 19 is switched based on a control signal from the control device 22, and the core wire 13 and the metal sheath 14 are connected to the picoammeter 20 to measure the current value corresponding to the radiation, thereby measuring the radiation.

[0066] Moreover, if a radiation measurement value close to zero is observed, the switch 19 is switched by a control signal from the control device 22 to connect the core wire 13 and the metal sheath 14 to the TDR measurement device 23. The TDR measurement device 23 confirms that the metal emitter 2 and the metal collector 7 are short-circuited inside the detector based on the reflection coefficient obtained by TDR measurement instead of the resistance value measurement by the resistance meter 21.

[0067] A method for detecting the occurrence of a short circuit inside the detector by TDR measurement will be described below with reference to Fig. 8. During measurement, the TDR measurement device 23 inputs a step voltage to the self-powered radiation detector 1. The step voltage propagates through the coaxial cable 30 via the switch 19.

[0068] Here, the characteristic impedance at each position of the coaxial cable 30 is Z L If the characteristic impedance at the entrance of the coaxial cable is Z0, then the reflected voltage is calculated by multiplying the incident step voltage by the reflection coefficient ρ from each position. The reflection coefficient ρ is defined by the following equation (1).

[0069]

number

[0070] That is, it can be expressed as the following equation (2).

[0071]

number

[0072] The reflection coefficient ρ at each position is evaluated by measuring the time elapsed after the step voltage is injected, the velocity coefficient, which is the ratio of the speed of the voltage propagating through the coaxial cable 30 to the speed of light, and the voltage at each time inside the TDR measuring device 23. As can be seen from the above formula (1), Z L The reflection coefficient ρ becomes 0 at the position where Z0 is equal to Z1.

[0073] Figure 8 shows a typical example of the reflection coefficient ρ when a TDR measurement is performed on a normal detector with a velocity factor of 0.6, and when the metallic emitter 2 and metallic collector 7 are short-circuited within the detector.

[0074] In the normal state where the self-powered radiation detector 1 is not short-circuited, the metallic emitter 2 and the metallic collector 7 are close to each other but are completely insulated from each other. In this state, the TDR measurement shows a characteristic impedance Z L As becomes infinite, the reflection coefficient approaches 1.

[0075] On the other hand, when the self-powered radiation detector 1 is short-circuited inside, the characteristic impedance Z L becomes 0, so the reflection coefficient asymptotically approaches -1. If this change in reflection coefficient occurs inside the self-powered radiation detector 1, it can be detected that a short circuit has occurred inside the self-powered radiation detector 1.

[0076] If the configuration of the radiation detection system 40 of Example 2 is used, it is not possible to distinguish between, for example, a short circuit between the core wire 13 and the metal sheath 14 that occurs at the midpoint of the cable and a short circuit that occurs inside the self-powered radiation detector 1.

[0077] However, by using the configuration of the radiation detection system 40A of this embodiment that uses the TDR measuring instrument 23, it is possible to distinguish and detect a short circuit that occurs at the midpoint of the cable from a short circuit that occurs within the detector, making it possible to detect with high reliability a short circuit between the metallic emitter 2 and the metallic collector 7 due to emitter leakage that occurs inside the detector.

[0078] Note that Figure 7 also describes the case where the self-powered radiation detector 1 shown in Figure 1 is used, but the self-powered radiation detector used in this embodiment 3 is not limited to the self-powered radiation detector 1 shown in Figure 1, and any of the self-powered radiation detectors 1A, 1B, 1C, and 1D shown in Figures 2 to 5 can be used.

[0079] The radiation detection system 40A according to the third embodiment of the present invention also provides substantially the same effects as those of the radiation detection system 40 according to the second embodiment described above.

[0080] Furthermore, by using the TDR measurement device 23 as the short circuit detector, it is possible to identify whether the short circuit occurs inside the self-powered radiation detector 1 or at a different location, making it easier to deal with the problem.

[0081] <Example 4> A reactor power monitoring device according to a fourth embodiment of the present invention will be described with reference to Fig. 9. Fig. 9 is a configuration diagram of a reactor power monitoring device according to a fourth embodiment of the present invention.

[0082] The reactor power monitoring device in Figure 9 includes the radiation detection system 40A described in Example 3, fission ionization chambers 104a, 104b, 104c, and 104d installed inside the in-reactor instrumentation tube 102, a neutron flux monitor 106 connected to the fission ionization chambers 104a, 104b, 104c, and 104d, and a power monitoring device 107 connected to a self-powered radiation detector 1 in the radiation detection system 40A and monitoring the reactor power.

[0083] Note that the radiation detection system 40 described in the second embodiment may be used instead of the radiation detection system 40A described in the third embodiment.

[0084] Four self-powered radiation detectors 1 shown in Figure 1 are installed at different heights inside an in-core instrumentation tube 102 installed inside a pressure vessel 101 of a nuclear reactor (self-powered radiation detector 1a, self-powered radiation detector 1b, self-powered radiation detector 1c, and self-powered radiation detector 1d from the vertically downward direction).

[0085] The self-powered radiation detectors 1a, 1b, 1c, and 1d used are assumed to be those shown in FIG. 1, but any one or more of the self-powered radiation detectors 1, 1A, 1B, 1C, and 1D shown in any of FIGS. 1 to 5 can be used in appropriate combination.

[0086] The lower part of the in-core instrumentation pipe 102 is constructed so that the cooling water 110 in the core does not flow out by a water seal 103. Each detector in the in-core instrumentation pipe 102 is connected to a picoammeter 20 and a TDR measuring instrument 23 by a coaxial cable 30 via a switch 19 equipped with a control device 22.

[0087] Fission ionization chambers 104a, 104b, 104c, and 104d are installed in the in-core instrumentation tube 102 at the same vertical height as the self-powered radiation detectors 1a, 1b, 1c, and 1d, respectively, and are connected to a neutron flux monitor 106 by a signal cable 105.

[0088] In addition, a power monitor 107 is connected to the neutron flux monitor 106 , the picoammeter 20 , the control device 22 and the TDR measurement device 23 .

[0089] The power monitoring device 107 is connected to the neutron flux monitor 106 to monitor the reactor power, and calculates the sensitivity of the neutron detector 104 based on the measurement value of the picoammeter 20 .

[0090] Next, the operation of the reactor power monitoring device thus configured will be described. In the reactor power monitoring device of this embodiment, the neutron flux in the reactor generates a current in the fission ionization chambers 104a, 104b, 104c, and 104d installed in the in-reactor instrumentation tube 102, and this current is measured by the neutron flux monitor 106 via the signal cable 105. The neutron flux monitor 106 multiplies the measured current value by a constant set for each detector to convert it into a neutron flux value, and sends the neutron flux value to the power monitoring device 107.

[0091] The power monitoring device 107 evaluates the reactor power based on the input neutron flux value, and checks the integrity of the fuel based on this reactor power, and also generates a signal to be used for activating a scram or the like in response to an abnormal change in reactor power during an accident, etc.

[0092] In parallel, the self-powered radiation detectors 1a, 1b, 1c, and 1d detect current corresponding to the radiation inside the reactor and pass it through the coaxial cable 30 to the picoammeter 20, where the current value is measured. The picoammeter 20 multiplies the measured current value by the sensitivity set for each detector to convert it into radiation intensity, and sends the radiation intensity to the power output monitoring device 107.

[0093] The output monitor 107, which has received the radiation intensity, compares the neutron flux value sent from the neutron flux monitor 106 with the radiation intensity sent from the picoammeter 20, calculates the amount of sensitivity degradation of the neutron flux value due to irradiation, and updates the constants for each detector built into the neutron flux monitor 106. This makes it possible to correct the sensitivity that is constantly and continuously degraded by irradiation, and to always obtain the correct neutron flux value according to the current values ​​of the fission ionization chambers 104a, 104b, 104c, and 104d.

[0094] The power monitor 107 also periodically outputs a command to the control device 22 connected to the switch 19 to switch to the TDR 23 side. At the same time, it sends a measurement command to the TDR 23, and confirms the normal state of the self-powered radiation detectors 1a, 1b, 1c, and 1d installed in the in-core instrumentation tube 102 by the operations shown in Figures 7 and 8. If a short circuit is confirmed in a detector, it stops comparing the radiation intensity from that detector with the neutron flux value from the neutron flux monitor 106, and displays a message that the metal emitter 2 of that detector is leaking.

[0095] By operating in this manner, the reactor power monitoring device shown in this embodiment can monitor the reactor power without using the measurement value when the metal emitter 2 leaks, thereby improving the reliability of the monitoring.

[0096] <Other> The present invention is not limited to the above-mentioned embodiment, but includes various modified examples. The above-mentioned embodiment has been described in detail to explain the present invention in an easily understandable manner, and the present invention is not necessarily limited to the embodiment having all of the described configurations.

[0097] It is also possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to add, delete, or replace part of the configuration of each embodiment with the configuration of another embodiment. [Explanation of symbols]

[0098] 1, 1A, 1B, 1C, 1D, 1a, 1b, 1c, 1d...Self-powered radiation detector 2…Metal emitter 3…Heat-resistant container 4...Metal terminal part 6...Airtight terminal 7…Metal collector 8…Tip plug 9…Terminal end plug 10,10A…insulation material 11...Insulation material 12, 12A, 12B, 12C, 18...Metal reservoir 13...Core wire (positive pole) 14...Metal sheath (negative electrode) 15…Insulation material 16...Insulating spacer 17...Heat-resistant insulating container 19…Switch 20...Picoammeter 21...Resistance meter 22...Control device 23…TDR measuring device 30...Coaxial cable (signal cable) 40,40A…Radiation detection system 101...Pressure vessels 102...Furnace instrumentation tube 103…Water seal part 104a, 104b, 104c, 104d... Fission chambers (neutron detectors) 105…Signal cable 106...Neutron flux monitor 107...Output monitoring device 110...Cooling water

Claims

1. A semiconductor device comprising: a metallic emitter that emits electrons when irradiated with radiation; a heat-resistant container that seals the emitter; a metal collector that contains the emitter and the heat-resistant container therein; a signal cable connecting the emitter to a positive terminal and the collector to a negative terminal; a metal reservoir provided on the collector on a side of the interior space including the emitter and the heat-resistant container and electrically connected to the collector; The metal reservoir is disposed around the heat-resistant container.

1. A self-powered radiation detector comprising:

2. A metal emitter that emits electrons when irradiated with radiation; a heat-resistant container that seals the emitter; a metal collector that contains the emitter and the heat-resistant container therein; a signal cable connecting the emitter to a positive terminal and the collector to a negative terminal; a metal reservoir provided on the collector on a side of the interior space including the emitter and the heat-resistant container and electrically connected to the collector; The heat-resistant container is made of an insulating material, The metal reservoir is formed in a disk shape below the heat-resistant container and is formed coaxially with the heat-resistant container so as to cover the side surface of the heat-resistant container.

1. A self-powered radiation detector comprising:

3. A metal emitter that emits electrons when irradiated with radiation; a heat-resistant container that seals the emitter; a metal collector that contains the emitter and the heat-resistant container therein; a signal cable connecting the emitter to a positive terminal and the collector to a negative terminal; a metal reservoir provided on the collector on a side of the interior space including the emitter and the heat-resistant container and electrically connected to the collector; The heat-resistant container is made of an insulating material, the collector is disposed so as to surround the heat-resistant container with a gap therebetween, The metal reservoir is formed in a disk shape below the heat-resistant container.

1. A self-powered radiation detector comprising:

4. A metal emitter that emits electrons when irradiated with radiation; a heat-resistant container that seals the emitter; a metal collector that contains the emitter and the heat-resistant container therein; a signal cable connecting the emitter to a positive terminal and the collector to a negative terminal; a metal reservoir provided on the collector on a side of the interior space including the emitter and the heat-resistant container and electrically connected to the collector; The metal reservoir is made of a metal mesh formed in a disk shape below the heat-resistant container.

1. A self-powered radiation detector comprising:

5. A self-powered radiation detector according to any one of claims 1 to 4; A control device; Switch, A picoammeter; a short detector within the self-powered radiation detector, The controller switches the switch so that either the picoammeter or the short detector is connected to the self-powered radiation detector. A radiation detection system comprising:

6. 6. The radiation detection system according to claim 5, The short circuit detector is a resistance meter or a TDR measuring instrument. A radiation detection system comprising:

7. A radiation detection system according to claim 5; a power monitoring device connected to the self-powered radiation detector in the radiation detection system and monitoring a reactor power; The self-powered radiation detector is installed inside an in-core instrumentation tube in a pressure vessel of a nuclear reactor. A reactor power monitoring device comprising:

8. 8. The reactor power monitor according to claim 7, A neutron detector installed inside the in-core instrumentation tube; a neutron flux monitor connected to the neutron detector; The power monitoring device is connected to the neutron flux monitor to monitor the reactor power and calculates the sensitivity of the neutron detector based on the measured value of the picoammeter. A reactor power monitoring device comprising:

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