Self-output radiation detector, radiation measurement system, and method for manufacturing self-output radiation detector

Abstract

To solve the problem that there is a possibility that a gap is generated between an emitter case and a collector under high temperature in a furnace and the emitter case is broken by vibration in a self-output type radiation detector.SOLUTION: A fixing member 106A formed of a material whose linear expansion coefficient is equal to or larger than those of an emitter case and a collector and whose neutron total cross section and attenuation coefficient are equal to or smaller than those of the emitter is interposed between the emitter case 103 and the collector 104 to fix the emitter case at high temperature in a reactor to improve vibration resistance.SELECTED DRAWING: FIG. 3A

Description

[Technical Field]

[0001] The present invention relates to a self-powered radiation detector for measuring reactor power in a boiling water nuclear power plant, a radiation measurement system, and a method for manufacturing a self-powered radiation detector. [Background technology]

[0002] Self-powered radiation detectors do not require a power supply such as the application of a voltage. These radiation detectors measure the current value that flows when the number of electrons in the material that makes up the detector changes due to irradiation with radiation. These radiation detectors are called self-powered gamma ray detectors (SPGDs) or self-powered neutron ray detectors (SPNDs) depending on the type of radiation they measure. Here, we will mainly use SPGDs as an example, but the basic concept and structure are the same for SPNDs.

[0003] In an SPGD, electrons are ejected from the emitter, the sensitive part of the detector, when irradiated with gamma rays and reach the collector. At this time, to replenish the electrons lost in the emitter, electrons move from the ground to the emitter via a conductor, causing a current to flow. Patent Document 1 discloses a typical SPGD configuration that uses an emitter, an emitter case that encloses the emitter, a collector, and a conductor to measure current. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2020-067312 Summary of the Invention [Problem to be solved by the invention]

[0005] In the self-powered gamma ray detector described in Patent Document 1, the collector is made of a material with a higher linear expansion coefficient than the emitter case. Therefore, at high temperatures inside the furnace, the collector expands more than the emitter case, resulting in a gap between the emitter case and the collector. The emitter case is not fixed except for its connection to the conductors, so it may be damaged by vibrations inside the furnace. Furthermore, since self-powered gamma ray detectors require detection of particularly weak signals, even slight vibrations can affect signal detection, and further improvements are desired. The present invention has been made in consideration of the above-mentioned demands, and has as its object to provide a self-powered radiation detector, a radiation measurement system, and a method for manufacturing a self-powered radiation detector that can fix the emitter case and collector even if they expand, and can prevent damage to the emitter case. [Means for solving the problem]

[0006] By sandwiching a fixing member between the emitter case and the collector, made of a material whose linear expansion coefficient is equal to or greater than that of the emitter case and the collector, and whose neutron total cross section and / or attenuation coefficient is equal to or less than that of the emitter, the fixing member expands at high temperatures inside the furnace, filling the gap between the emitter case and the collector and fixing the emitter case. [Effects of the Invention]

[0007] According to the present invention, the emitter case is fixed by the fixing member, which reduces the possibility of damage due to vibration. Furthermore, since the material of the fixing member has a neutron total cross section and / or attenuation coefficient equal to or less than that of the emitter, the fixing member is less likely to interact with neutrons and gamma rays than the emitter, which prevents a decrease in current measurement sensitivity. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a configuration diagram schematically showing a radiation measurement system according to the present invention. [Figure 2A] FIG. 2 is a cross-sectional view schematically illustrating the configuration of the SPGD according to the first embodiment. [Figure 2B] FIG. 2 is a cross-sectional view of the SPGD according to the first embodiment taken along line IIB-IIB. [Figure 2C] FIG. 2 is a schematic diagram showing a fixing member used in the SPGD according to the first embodiment. [Figure 3A] 1 is a schematic diagram showing, in partial cross section, the configuration of an SPGD provided with a fixing member according to a first embodiment. [Figure 3B] 3B is a cross-sectional view of the SPGD provided with the fixing member of FIG. 3A taken along line IIIB-IIIB. [Figure 4A] FIG. 10 is a schematic diagram showing, in partial cross section, the configuration of an SPGD provided with a fixing member according to a second embodiment. [Figure 4B] 4B is a cross-sectional view of the SPGD with the fixing member of FIG. 4A taken along line IVB-IVB. [Figure 5A] FIG. 11 is a schematic diagram showing, in partial cross section, the configuration of an SPGD provided with a fixing member according to a third embodiment. [Figure 5B] 5B is a cross-sectional view of the SPGD provided with the fixing member of FIG. 5A along the line VB-VB. [Figure 6A] FIG. 10 is a schematic diagram showing, in partial cross section, the configuration of an SPGD provided with a fixing member according to a fourth embodiment. [Figure 6B] 6B is a cross-sectional view of the SPGD with the fixing member of FIG. 6A taken along the line VIB-VIB. [Figure 6C] FIG. 10 is a perspective view schematically illustrating a fixing member and an installation hole according to a fourth embodiment, separated from each other. [Figure 6D] FIG. 10 is a schematic cross-sectional view of a first application example of a fixing member according to a fourth embodiment. [Figure 6E] FIG. 10 is a schematic cross-sectional view of a second application example of the fixing member according to the fourth embodiment. [Figure 6F] FIG. 10 is a schematic cross-sectional view of a third application example of the fixing member according to the fourth embodiment. [Figure 7A] FIG. 10 is a schematic diagram showing, in partial cross section, the configuration of an SPGD provided with a fixing member according to a fifth embodiment. [Figure 7B] 7B is a cross-sectional view of the SPGD with the fixing member of FIG. 7A taken along line VIIB-VIIB. [Figure 8] FIG. 13 is a perspective view schematically illustrating, with a portion thereof omitted, an SPGD provided with a fixing member according to a sixth embodiment. [Figure 9] FIG. 13 is a perspective view schematically illustrating, with a portion thereof omitted, an SPGD provided with a fixing member according to a seventh embodiment. [Figure 10A] 10 is a schematic diagram showing, in partial cross section, the configuration of an SPGD provided with a fixing member according to a first modified example. FIG. [Figure 10B] 10B is a cross-sectional view of the SPGD provided with the fixing member of FIG. 10A taken along line VIIIB-VIIIB. [Figure 11A] FIG. 10 is a schematic cross-sectional view of an SPGD equipped with a fixing member according to a second modified example. [Figure 11B] 11B is a cross-sectional view of the SPGD provided with the fixing member of FIG. 11A taken along line VIIIB-VIIIB. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that identical components are designated by the same reference numerals, and redundant descriptions may be omitted. The present invention is not limited to the following embodiments. In each drawing, the components may be exaggerated to different dimensions for clarity. Furthermore, each drawing shows a cross-sectional portion and other components together for clarity. Furthermore, the fixing member shown in each drawing is shown with a gap between the emitter case and the collector for clarity. However, the fixing member is interposed between the fixing member and the emitter case, and between the fixing member and the collector, without any gap. In other words, the fixing member is present in the gap. Furthermore, in each drawing, the plane of the fixing member facing the collector or the emitter case is a curved surface with the same curvature as the curved surface of the collector or the emitter case.

[0010] Furthermore, although self-powered radiation detectors include SPGDs and SPNDs, the following description will be given taking an SPGD as an example. Furthermore, the material of the fixing member 106A must have a neutron total cross section, which indicates the interaction probability with neutrons, and / or an attenuation coefficient, which indicates the interaction probability with gamma rays, that is at least equal to or less than that of the emitter 102. Therefore, the fixing member 106A may have a neutron total cross section that is equal to or less than that of the emitter 102, an attenuation coefficient that is equal to or less than that of the emitter 102, or both a neutron total cross section and an attenuation coefficient that are equal to or less than that of the emitter 102. Here, the neutron cross section is defined as the sum of all types of cross sections, such as the neutron absorption cross section and scattering cross section, for a certain substance. The SPGD 101 is used in a configuration such as a radiation measurement system 300 in a nuclear power plant, for example. 1, a radiation measurement system 300 uses an SPGD 101 disposed inside a reactor 301 to control the control rods 201 in the reactor 301 and the recirculation pump 304 of the reactor 301 via a central signal processor 303, a computer 308, a reactor control panel 309, etc. This radiation measurement system 300 is used to monitor the state of the fuel in the reactor by controlling the control rods 201 and the recirculation pump 304. As an example, the radiation measurement system 300 includes a preamplifier 305, a reactor power control panel 302, a control rod operation panel 306, and a reactor protection system panel 307 in order to control the state of the fuel in the reactor using signals from the SPGD 101.

[0011] The preamplifier 305 receives and amplifies the signal from the SPGD 101 and sends the amplified signal to the central signal processor 303. The reactor power control panel 302 controls the recirculation pump in accordance with the reactor power control signal from the central signal processor 303. The control rod operation panel 306 operates the control rods 201 in accordance with the control rod withdrawal element signal from the central signal processor 303. The reactor protection system panel 307 shuts down the reactor 301 in accordance with the scram signal from the central signal processor 303.

[0012] 2A and 2B show the basic configuration of an SPGD that detects radiation used in the radiation measurement system of the above-mentioned nuclear reactor 301. The SPGD 101 includes an emitter 102, which is a sensitive part, an emitter case 103 that encloses (contains) the emitter, a collector 104, and a conducting wire 105. Because there is a potential difference between the emitter 102 and the collector 104, they are insulated from each other by an emitter case 103 made of an insulating material to prevent electrical contact between the two components. Generally, the emitter case 103 is made of alumina, an insulating material, and the collector 104 is made of stainless steel, and stainless steel has a higher linear expansion coefficient than alumina. Therefore, at high temperatures in the furnace, the collector 104 expands more than the emitter case 103, creating a gap between the emitter case 103 and the collector 104. When a gap is created, the emitter case 103 is not fixed except for its connection to the conductor 105, and vibrations can cause it to break.

[0013] Therefore, in the following first to sixth embodiments, measures to prevent damage caused by vibration due to the gap between the emitter case 103 and the collector 104 will be described. In this embodiment, a configuration will be described in which a fixing member is sandwiched between the emitter case 103 and the collector 104 as a vibration countermeasure for the SPGD 101. Note that the materials of the emitter case 103 and the collector 104 are not limited to those shown below. The SPGD 101 is disposed, for example, inside a measurement guide tube. In this embodiment, the inside of the measurement guide tube reaches a high temperature corresponding to the temperature inside the furnace, but the pressure inside the furnace is not directly applied to the SPGD 101.

[0014] [First embodiment] 3A and 3B show the configuration of an SPGD 101 equipped with fixing members 106A. In the configuration of Figures 3A and 3B, the SPGD 101 has three rod-shaped fixing members 106A, as shown in Figure 2C, sandwiched between the emitter case 103 and the collector 104. Fixing member 106A expands at high temperatures in the furnace, filling the gaps between emitter case 103 and fixing member 106A and between collector 104 and fixing member 106A, thereby fixing emitter case 103. At this time, the amount of expansion of fixing member 106A must be equal to or greater than the amount of expansion of the gap between emitter case 103 and collector 104. Therefore, the material of fixing member 106A must have a linear expansion coefficient at least equal to or greater than that of emitter case 103 and collector 104.

[0015] Furthermore, by incorporating the fixing member 106A into the SPGD 101, gamma rays that should interact with the emitter 102 may interact with the fixing member 106A, reducing the number of electrons that flow to the emitter 102 and potentially reducing the measurement sensitivity of the current value. Furthermore, when the fixing member 106A interacts with neutrons, electrons that are ejected from the fixing member 160A reach the emitter 102, reducing the number of electrons that should be replenished from the ground, thereby reducing the measurement sensitivity of the current value. For this reason, the material of the fixing member 106A must have a neutron total cross section, which indicates the probability of interaction with neutrons, and / or an attenuation coefficient, which indicates the probability of interaction with gamma rays, that is at least equal to or less than that of the emitter 102.

[0016] When using lead bismuth for the emitter 102, SUS304 for the collector 104, and alumina for the emitter case 103, the material for the fixing member 106A that satisfies the conditions of a linear expansion coefficient greater than or equal to that of the emitter case 103 and the collector 104, and a neutron total cross section and attenuation coefficient less than or equal to that of the emitter 102, is, for example, aluminum. An example of the dimensions of each member when aluminum is used for fixing member 106A is shown below. The inner diameter ds' of the collector, the outer diameter de' of the emitter case, and the outer diameter df' of fixing member 106A when the temperature rises by ΔT are expressed by equations (1), (2), and (3) using the inner diameter ds of collector 104 before expansion, the outer diameter de of emitter case 103 before expansion, the outer diameter df of fixing member 106A before expansion, the linear expansion coefficient αs of SUS304, the linear expansion coefficient αe of alumina, and the linear expansion coefficient αf of aluminum. ds'=ds+αsΔTds Equation (1) de'=de+αeΔTde Equation (2) df'=df+αfΔTdf Equation (3)

[0017] If the inner diameter ds of collector 104 before expansion is 13 mm, the outer diameter de of emitter case 103 before expansion is 5 mm, the linear expansion coefficient αs of SUS304 is 17.3 × 10-6 [1 / °C], the linear expansion coefficient αe of alumina is 9.042 × 10-6 [1 / °C], and the temperature change ΔT is 300°C, using equations (1) and (2), the inner diameter ds' of collector 104 after expansion will be 13.07 mm, the outer diameter de' of emitter case 103 will be 5.01 mm, and the gap between emitter case 103 and collector 104 will be 4.03 mm. If the outer diameter of the fixing member 106A before expansion is 4 mm and the linear expansion coefficient αe of aluminum is 23×10 −6 [1 / °C], then using equation (3), the outer diameter df′ of the fixing member 106A after expansion will be 4.03 mm.

[0018] Since the gap of 4.03 mm between emitter case 103 and collector 104 after expansion is equal to the outer diameter of fixing member 106A after expansion, 4.03 mm, it can be seen that fixing member 106A fills the gap between emitter case 103 and collector 104 when expanded. The material of the emitter 102, lead-bismuth, is an alloy of lead and bismuth, and the total neutron cross section of aluminum is about one-third smaller than that of lead and bismuth. Furthermore, the density of aluminum, which is proportional to the attenuation coefficient, is also about one-quarter smaller than that of lead and bismuth. Therefore, by using aluminum as the material of the fixing member 106A, it is possible to suppress a decrease in the measurement sensitivity of the current value.

[0019] Furthermore, if the expansion rate of fixing member 106A becomes larger than the expansion rate of the gap between emitter case 103 and collector 104, it is preferable that fixing member 106A has a certain degree of flexibility, and it is desirable to use a material for fixing member 106A that has a smaller Young's modulus than emitter case 103 and collector 104. In this case, even if the expansion rate of fixing member 106A becomes larger than the expansion rate of the gap between emitter case 103 and collector 104, the possibility of damage to emitter case 103 or collector 104 can be reduced.

[0020] Furthermore, the fixing member 106A does not need to be solid as long as its strength is maintained; it may be hollow. In this case, the device is lighter and the fixing member 106A suppresses interactions with neutrons and gamma rays, thereby improving sensitivity. That is, the fixing member 106A may have a rod-like shape, such as that shown in FIGS. 3A and 3B, but may also have a circular cross-sectional shape. The cross-sectional shape of the fixing member 106A perpendicular to the longitudinal direction may be a rectangle such as a square or parallelogram, a trapezoid, a circle, a triangle, a pentagon, or a polygon, an ellipse, or an arc. The cross-sectional shape of the fixing member 106A is not particularly limited as long as it can be interposed between the emitter case 103 and the collector 104. However, from the perspective of stability when interposed, an arc-shaped cross-section is particularly advantageous, as it provides area contact rather than line contact when the emitter case 103 and the collector 104 are in contact.

[0021] Furthermore, in the first embodiment, an example in which three rod-shaped fixing members 106A are inserted is shown, but the number of fixing members 106A is not limited to other shapes, and may be two, four, five, six, seven, eight, etc. Furthermore, rod-shaped fixing members 106A with different cross-sectional shapes may be used in combination. Furthermore, although the length of fixing member 106A is shown as being longer than emitter case 103, it may be the same length as emitter case 103 or two-thirds the length of emitter case 103. Furthermore, although aluminum has been shown as an example of the material for fixing member 106A, polyimide is also a candidate material for fixing member 106A instead of aluminum. The fixing member 106A may have a neutron total cross section equal to or smaller than that of the emitter 102, an attenuation coefficient equal to or smaller than that of the emitter 102, or a neutron total cross section and attenuation coefficient equal to or smaller than that of the emitter 102.

[0022] Furthermore, while the example in which the fixing members 106A are inserted in the longitudinal direction of the self-powered radiation detector has been described, the fixing members 106A may also be arranged in the lateral direction. Even without arranging the fixing members 106A in the lateral direction, the friction between the fixing members 106A and the emitter case 103 or the collector 104 can suppress vibration in the lateral direction of the SPGD (self-powered radiation detector). However, inserting the fixing members 106A in the lateral direction also suppresses vibration in the lateral direction more effectively. Arranging the fixing members 106A along the lateral direction means arranging them in an arc shape around the circumferential direction of the emitter case 103 between the fixing members 106A arranged in the longitudinal direction. In the SPGD 101, vibration refers to vibrations that occur not only during natural disasters such as earthquakes but also in various other situations, such as vibrations caused by the driving of a motor in a reactor internal structure. Furthermore, the SPGD 101, including the fixing members 106A, exhibits vibration suppression effects against both lateral and vertical vibrations.

[0023] As described above, in the SPGD 101, the emitter case 103 is fixed by the fixing member 106A, thereby reducing the possibility of damage due to vibration. In particular, self-powered gamma-ray detectors require weak signal detection, and even slight vibrations can affect signal detection. However, application of the present invention can suppress vibrations that affect signal detection. Furthermore, the present invention is applicable to any type of reactor, such as a boiling water reactor or a pressurized water reactor. In particular, for fast reactors with high-temperature cores, the present invention can suppress vibrations caused by a large gap between the emitter case 103 and the collector 104 in high-temperature environments. Furthermore, because the material of the fixing member has a neutron total cross section and / or attenuation coefficient that is smaller than that of the emitter, the fixing member is less likely to interact with neutrons and gamma rays than the emitter, thereby suppressing a decrease in current measurement sensitivity.

[0024] The second to eighth embodiments will be described below with reference to the drawings. Note that the materials and sizes of the components, calculations related to expansion and contraction, etc., already described in the first embodiment are the same as those in the first embodiment, and therefore will not be described again. [Second embodiment] The second embodiment will be described with reference to FIGS. 4A and 4B. As shown in FIGS. 4A and 4B, the configuration when the fixing member 106B is inserted in a spiral shape is illustrated. In FIGS. 4A and 4B, a wire-shaped fixing member 106B is used, and the wire fixing member 106B is wound in a spiral shape around the emitter case 103. By using the spiral fixing member 106B in this manner, it is possible to prevent misalignment of the fixing member 106B in the longitudinal direction, lateral direction, and diagonal direction.

[0025] Therefore, there is no risk of the fixing member being displaced in an oblique direction, which can occur with rod-shaped fixing member 106A as shown in Figures 3A and 3B. Furthermore, with this configuration of fixing member 106B, there is no need to fix a new fixing member, and the number of required components can be reduced. The angle of inclination of fixing member 106B is not particularly limited, and the cross-sectional shape may be circular, annular, rectangular, or the like. Furthermore, the arrangement intervals are preferably symmetrical from the center, for example, but do not need to be equal as long as they are symmetrical.

[0026] [Third embodiment] A third embodiment will now be described with reference to FIGS. 5A and 5B. As shown in FIGS. 5A and 5B, the fixing members 106C may be arranged by winding a wire loop around the emitter case 103. The fixing members 106C may be wound around the emitter case 103 at equal intervals in the longitudinal direction. While FIG. 5A shows a configuration in which multiple fixing members 106C are wound around the emitter case 103 in the longitudinal direction, the fixing members 106C may be wound only around both bottom portions (both ends of the emitter case in the longitudinal direction in FIG. 5A) of the emitter case 103, which are thick and strong. In this case, fewer fixing members 106C are required to achieve the vibration suppression effect compared to FIGS. 3A and 4A. The arrangement and spacing of the fixing members 106C can be freely set as long as there are two or more fixing members 106C, such as at the center and the left and right ends. Furthermore, although the cross-sectional shape of the fixing member 106C is shown as being circular, the cross-sectional shape may be sectorial, elliptical, or annular.

[0027] [Fourth embodiment] Next, a fourth embodiment will be described with reference to FIGS. 6A, 6B, and 6C. At high temperatures inside a furnace, the size of the fixing member may become large in order to precisely fill the gap between the emitter case 103 and the collector 104. In this case, it is necessary to reduce the outer diameter of the emitter case 103 or increase the inner diameter of the collector 104. If the inner diameter of the emitter case 103 is reduced, the capacity of the emitter 102, which is the sensitive part, also decreases, leading to a decrease in the amount of gamma rays measured. Furthermore, due to constraints on the installation environment of the SPGD 101, there is an upper limit to the inner diameter of the collector 104.

[0028] 6A to 6C, in the fourth embodiment, slits 6 are formed in the side surface of the emitter case 103, and fixing members 106D are inserted into the slits 6, thereby making it possible to fix the emitter case 103 while ensuring the capacity of the emitter 102. The fixing members 106D used here are formed in a rectangular parallelepiped or cubic shape, and the surface facing the inner surface of the collector 104 is formed as a curved surface with the same curvature as the inner surface of the collector 104. The fixing members 106D are arranged at six locations in total, three at each 120-degree interval in the circumferential direction on one end and the other end of the emitter case 103.

[0029] The fixing members 106D are arranged at positions opposing each other at one end and the other end of the emitter case 103. The number of fixing members 106D arranged in the circumferential direction of the emitter case 103 is three or more at each of the one end and the other end, and may be four, five, six, seven, eight, nine or more. Furthermore, the fixing members 106D are arranged at positions opposing each other at one end and the other end of the emitter case 103 in the circumferential direction, but they may also be arranged at positions not opposing each other.

[0030] 6D, as a first application example of the fourth embodiment, instead of or in addition to the slit 6 on the side surface of the emitter 102, a slit 16 may be formed on the inner surface of the collector 104, and a fixing member 106D may be inserted into the slit 16, thereby fixing the emitter case 103 while ensuring the capacity of the emitter 102. The side surface on which the slit 6 of the emitter case 103 or the slit 16 of the collector 104 is formed may be located in any position in the longitudinal direction and / or lateral direction of the SPGD (self-powered photodetector) 101 (either the left or right end surface of the paper in FIG. 6D).

[0031] 6E, as a second application example of the fourth embodiment, a more preferable configuration is one in which slits 26, 36 are formed in corners of the collector 104 and the emitter case 103 (edges of the bottom surface) and the fixing member 106D1 is inserted into the slits. The fixing member 106D1 used here has a first protrusion 106d11 on one end side that is inserted into the slit 26 and a second protrusion 106d12 on the other end side that is inserted into the slit 36. The fixing members 106D1 are preferably arranged at three or more equally spaced locations in the circumferential direction on each of the one and other ends of the emitter case 103. When the fixing members 106D1 are used in this manner, it is possible to suppress lateral and vertical vibrations and ensure the capacity of the emitter 102.

[0032] Furthermore, as a third application example of the fourth embodiment, as shown in FIG. 6F , a fixing member 106D2 may be provided with a recess 46 serving as a slit only on the emitter case 103 side, and a protrusion 106d13 fitted into the recess 46. In FIG. 6F , the fixing member 106D2 has one end face that contacts the bottom surface of the collector 104, and a side perpendicular to the one end face that contacts the inner surface of the collector 104. The other end face of the fixing member 106D2 contacts the top surface of the collector 104, and a side perpendicular to the other end face that contacts the inner surface of the collector 104. It is preferable that the fixing members 106D2 be arranged at three or more locations in the circumferential direction at both ends of the emitter case 103. This fixing member 106D2 can suppress both lateral and longitudinal vibrations and ensure the capacity of the emitter 102. As a fourth application example of the fourth embodiment, the slits formed in the emitter case 103 may be arranged at two orthogonal positions on the emitter case 103, and fixing members 106D may be arranged in the two orthogonal slits. In this case, the one slit and the other slit may be arranged at different angles so as not to have the same cross section, or may be arranged at the same cross section. This fourth application example also makes it possible to suppress lateral and vertical vibrations and ensure the capacity of the emitter 102.

[0033] [Fifth embodiment] Next, a fifth embodiment will be described with reference to FIGS. 7A and 7B. The SPGD 101 must be able to withstand vibrations at high reactor temperatures, but it also needs to withstand vibrations when the reactor temperature drops during the startup and shutdown processes of a nuclear power plant. If only fixing members made of materials with the same linear expansion coefficient are used, the temperature range in which the gap between the emitter case 103 and the collector 104 can be filled is limited. Therefore, as shown in FIGS. 7A and 7B , a first fixing member 107 made of a first material and a second fixing member 108 made of a second material, each with a different linear expansion coefficient, are provided. In this way, by using the first fixing member 107 and the second fixing member 108 with different linear expansion coefficients, the gap can be filled to prevent vibrations in a variety of temperature ranges.

[0034] For example, if the second fixing member 108 made of the second material has a larger linear expansion coefficient than the first fixing member 107 made of the first material, the second fixing member 108 made of the second material will expand more easily. Therefore, the first fixing member 107 made of the first material can be used for fixing in a low temperature range, and the second fixing member 108 made of the second material can be used for fixing in a high temperature range. The first fixing member 107 and second fixing member 108 used here are shown as rods with circular cross sections, but the shapes and number are not particularly limited, as with those described in Figures 3A and 3B.

[0035] [Sixth embodiment] Next, a sixth embodiment will be described with reference to Fig. 8. In Fig. 8, only the emitter case 103 and the fixing member 106E are shown, but the collector 104 and the conducting wires 105 are omitted. As shown in FIG. 8, the fixing member 106E is T-shaped in a plan view. The fixing member 106E includes a periphery 106E1 arranged in the circumferential direction of the emitter case 103, an orthogonal side 106E2 arranged continuously from the periphery 106E1 in a direction perpendicular to the periphery 106E1, and a protrusion 106E3 formed protruding from the rear surface of the periphery 106E1 and / or the orthogonal side 106E2. A recess 56 serving as a slit is formed in the side surface of the emitter case 103, and the protrusion 106E3 of the fixing member 106E is fitted into this recess 56 to position the fixing member 106E. The fixing members 106E are arranged at 120-degree intervals at one end and the other end of the emitter case 103 in FIG. 8 so as not to face each other. Of course, the fixing members 106E may be arranged so that the fixing members 106E face each other at one end and the other end of the emitter case 103. Furthermore, fixing members 106E may be arranged so that four are arranged on each of one end (right side) and the other end (left side) of emitter case 103, for a total of eight, and half of the eight (four members) may have a different linear expansion coefficient from the other four members.

[0036] [Seventh embodiment] The seventh embodiment will be described further with reference to Fig. 9. In Fig. 9, the emitter case 103 and the fixing member 106E are shown, but the collector 104 and the conducting wires 105 are omitted. As shown in FIG. 9, the fixing member 106F has a facing edge 106E4 that is continuous with the periphery 106E1 of the fixing member 106E and contacts the bottom or top surface of the emitter case 103. This facing edge 106E4 has a thickness that extends from the bottom or top surface of the emitter case 103 to the bottom or top surface of the collector 104. Therefore, the fixing member 106F can also suppress horizontal and vertical vibrations. As with the fixing member 106E described above, the fixing members 106F can be arranged at both ends of the emitter case 103 in opposing positions or in non-opposing positions. Furthermore, the material of the fixing member 106F can also be such that half of the fixing members have different linear expansion coefficients.

[0037] [First Modification] Note that the SPGD may be configured by appropriately combining the configurations already described, for example, as shown in Figures 10A and 10B, fixing member 106D described in Figure 6A and fixing member 106C described in Figure 5A may be used together. In such a case, it is more preferable to use fixing member 106C with a linear expansion coefficient different from that of fixing member 106D.

[0038] [Second Modification] Furthermore, as shown in FIGS. 11A and 11B, fixing member 118 having the same configuration as fixing member 106D described in FIG. 6A but a different linear expansion coefficient may be used in combination. In this way, by using fixing member 106D and fixing member 118 with a different linear expansion coefficient, it is possible to fill gaps to prevent vibration in response to a plurality of temperature ranges while ensuring the capacity of emitter 102, and to fix emitter case 103. Note that it is preferable to use fixing members 106D and fixing members 118 in an even number of four or more. It is also possible to combine any of the first to eighth embodiments not described with reference to the drawings. The slits described above may be groove-shaped or hole-shaped and refer to recesses formed in the emitter case 103 or the collector 104, and there are no limitations on their size or shape.

[0039] Next, a method for disposing the emitter case 103 in the collector 104 of the SPGD 101 with the fixing member 106 interposed therebetween will be described based on the configuration of the first embodiment as an example. Note that, while the fixing member 106A shown in the first embodiment will be described as an example here, the same method can be used with fixing members of other embodiments. Also, although the collector 104 is shown in the drawings as a one-piece cylindrical case, it is actually formed by covering a cylindrical member that is open at one or both of its longitudinal ends.

[0040] In the SPGD 101, when the SPGD is manufactured at a temperature at which the components do not expand or contract (for example, at room temperature), the gap between the emitter case 103 and the collector 104 may be narrow. Therefore, the gap between the fixing member 106A and the gap between the collector 104 and the fixing member 106A at room temperature are narrow, and it may be difficult to insert the fixing member 106A between the emitter case 103 and the collector 104.

[0041] In such a case, it becomes easier to insert fixing member 106A by heating only collector 104 to expand the inner diameter of collector 104 and widen the gap between emitter case 103 and collector 104. It also becomes easier to insert fixing member 106A by cooling emitter case 103 to narrow the outer diameter of emitter case 103 and widen the gap between emitter case 103 and collector 104.

[0042] When the collector 104 is heated and the fixing member 106 is inserted into the gap, this can be done by so-called shrink fitting. For example, the collector 104 is heated and expanded using a heating means such as an electric furnace or an induction heating device. Then, the emitter case 103 is placed inside the collector 104, and the fixing member 106 is placed between the emitter case 103 and the collector 104. When the collector 104 returns to room temperature, it returns to its original size from the state in which it was expanded by heating. Therefore, the fixing member 106A can be installed between the emitter case 103 and the collector 104 without leaving a gap.

[0043] Furthermore, when the emitter case 103 is cooled and the fixing member 106A is inserted into the gap, this can be done by so-called cold fitting. For example, the emitter case 103 is cooled and shrunk using a cooling means such as dry ice. Then, the emitter case 103 is placed inside the collector 104, and the fixing member 106A is placed between the emitter case 103 and the collector 104. When the emitter case 103 returns to room temperature, it returns to its original size from the state in which it was shrunk by cooling. Therefore, the fixing member 106A can be installed without leaving a gap between the emitter case 103 and the collector 104.

[0044] Note that fixing member 106A may be cooled and contracted before being placed between emitter case 103 and collector 104. Fixing member 106A returns to its original size from the contracted state when returned to room temperature, allowing fixing member 106A to be installed between emitter case 103 and collector 104 without any gaps.

[0045] As explained above, by interposing the fixing member shown in each embodiment, application example, and modified example between the emitter case 103 and the collector 104, it is possible to fix the emitter case 103 at high temperatures inside a furnace and improve vibration resistance. Note that with regard to the self-powered radiation detector according to the present invention, the embodiment and modified examples described above and shown in the drawings are merely examples embodied in carrying out the present invention, and the technical scope of the present invention should not be interpreted in a limited manner by these. [Explanation of symbols]

[0046] 101...SPGD (self-powered radiation detector), 102...Emitter, 103...Emitter case, 104...Collector, 105...Conducting wire, 106A, 106B, 106C, 106D, 106D1, 106D2, 106E, 106F, 118...Fixing members, 107...first material fixing member (first fixing member), 108...Second material fixing member (second fixing member), 201...Control rod 300...Radiation measurement system 301...nuclear reactor, 302...Reactor power control panel 303...Central signal processing unit 304...Recirculation pump 305...Preamplifier, 306...Control rod operation panel 307…Reactor protection system panel 308...Calculator 309...Reactor control panel.

Claims

1. A self-powered radiation detector including an emitter, an emitter case made of an insulating material and containing the emitter, and a collector containing the emitter case, A self-powered radiation detector characterized by comprising a fixing member between the emitter case and the collector, the fixing member being formed from a material whose neutron total cross section and / or attenuation coefficient is equal to or less than that of the emitter.

2. 2. The self-powered radiation detector according to claim 1, wherein the fixing member is formed of a material having a linear expansion coefficient equal to or greater than that of the emitter case and the collector.

3. 3. The self-powered radiation detector according to claim 2, wherein the fixing member is a wire material, and the wire material is wound spirally around the emitter case.

4. 3. A self-powered radiation detector according to claim 2, wherein the fixing member is a wire material, and the wire material is wound around the emitter case in a loop shape.

5. 3. A self-powered radiation detector according to claim 2, wherein a slit is provided on the surface of the emitter case, and the fixing member is fitted into the slit.

6. 3. The self-powered radiation detector according to claim 2, further comprising two or more fixing members having different linear expansion coefficients.

7. 3. A self-powered radiation detector according to claim 2, wherein the fixing member is made of at least one of aluminum and polyimide.

8. 3. The self-powered radiation detector according to claim 2, wherein a slit is provided on the surface of the emitter case, the fixing member includes a periphery formed in a circumferential direction of the emitter case and an orthogonal side continuing from the periphery in a direction orthogonal to the periphery, A self-powered radiation detector having a protrusion on the periphery and / or the orthogonal side that fits into the slit.

9. 6. The self-powered radiation detector according to claim 5, wherein the slits are provided at two orthogonal positions on the emitter case, and fixing members are fitted into the two orthogonal slits.

10. A radiation measurement system for monitoring the state of fuel used in a nuclear power plant, comprising: a self-powered radiation detector for detecting radiation; The self-powered radiation detector includes an emitter, an emitter case formed of an insulating material that encapsulates the emitter, and a collector; A radiation measurement system comprising: a fixing member between the emitter case and the collector, the fixing member being formed from a material whose neutron total cross section and / or attenuation coefficient is equal to or less than that of the emitter.

11. 3. The method for manufacturing a self-powered radiation detector according to claim 2, wherein only the collector is heated, and the fixing member is inserted in a state where a gap is opened between the collector and the emitter case.

12. 3. The method for manufacturing a self-powered radiation detector according to claim 2, wherein only the emitter case is cooled, and the fixing member is inserted in a state where a gap is opened between the collector and the emitter case.

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