A nuclear safety class radiation hardened seismometer

Abstract

The present application provides a nuclear safety level anti-radiation seismic accelerometer, wherein the nuclear safety level anti-radiation seismic accelerometer comprises a bottom plate (1), a metal base (2), six pick-up sensors (3) and a metal shell. The six pick-up sensors (3) are arranged to measure acceleration values in three axial directions of horizontal direction and vertical direction. Two pick-up sensors (3) are oppositely arranged on the coaxial line in each measuring direction, and the two pick-up sensors (3) are backup for each other. Since the orientations are different, the nuclear radiation intensity received by each pick-up sensor (3) will be different. When one pick-up sensor (3) is damaged due to nuclear radiation, the backup pick-up sensor (3) can still work normally and output the seismic acceleration value, thereby enhancing the anti-radiation capability of the seismic accelerometer in the radiation environment, and enabling the seismic accelerometer to work in the nuclear reactor for a long time.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of earthquake monitoring, and particularly relates to a nuclear safety level anti-radiation seismic accelerometer. BACKGROUND

[0002] Earthquake disasters can cause destructive damage to nuclear power plants, resulting in damage to plant buildings and equipment, and in extreme cases, may cause nuclear material leakage, causing irreparable damage to the surrounding environment. At the present stage, nuclear power plants are equipped with earthquake monitoring systems. Since the key components such as seismic accelerometers of the system cannot meet the requirements of nuclear safety level, they can only be arranged outside the nuclear reactor of the nuclear power plant, which cannot truly play the function of earthquake early warning and safety protection of the nuclear power plant.

[0003] The operating environment of nuclear safety level equipment is very harsh, with a long-term operating temperature of up to 70℃, an operating humidity generally maintained at 95%, and most of the environment being a nuclear radiation area. The cumulative total dose of radiation within the specified service life of the nuclear safety level equipment is as high as 25Mrad. For example, Chinese patent CN201220547058.4 discloses a nuclear power plant earthquake monitoring system, which includes seven three-axis acceleration sensors and four passive peak accelerometers, and is directly arranged at the reactor without any protection. Under the destruction of nuclear radiation, electronic products will cause phenomena such as increase of static current, signal zero offset, and other phenomena due to ionizing radiation effect, resulting in serious distortion of the output signal. At the same time, the high temperature and high humidity environment will cause rapid corrosion and damage of the equipment material body, accelerating the failure of the equipment. These environmental conditions limit the existing seismic accelerometers from working in the nuclear reactor for a long time. SUMMARY

[0004] Therefore, the present application provides a nuclear safety level anti-radiation seismic accelerometer to solve the problem that the existing seismic accelerometers cannot work in the nuclear reactor for a long time.

[0005] The technical scheme of the present application is as follows: The present application provides a nuclear safety level anti-radiation seismic accelerometer, wherein the nuclear safety level anti-radiation seismic accelerometer comprises:

[0006] a bottom plate, a metal base, six seismic pickups, and a metal shell;

[0007] The bottom plate is a rectangular plate, the height of the upper surface in the middle is greater than the height of the upper surface at both ends, and the upper surface in the middle and the upper surface at both ends form steps, respectively;

[0008] The metal base is a square, the lower surface in the middle is inwardly recessed to form a hollow part, the hollow part and the lower surface at both ends form two support parts, and the two support parts are arranged on the upper surface in the middle of the bottom plate;

[0009] 6 said pick-ups are arranged at the center of the 6 faces of the metal base respectively, and the central axis of each pick-up coincides with the central axis of the face;

[0010] The metal shell is adapted to the shape of the bottom plate and the metal base, and is used for covering the bottom plate, the metal base and the 6 pick-ups.

[0011] On the basis of the above technical scheme, preferably, the pick-up comprises:

[0012] The pendulum body shell, the two supporting springs, the inertial mass block, the coil skeleton, the multi-turn coil and the signal amplification circuit;

[0013] The inertial mass block is located inside the pendulum body shell and is in a cylindrical shape, the upper surface of the inertial mass block is connected to the lower surface of the top of the pendulum body shell through one of the supporting springs, and the lower surface of the inertial mass block is connected to the upper surface of the bottom of the pendulum body shell through the other supporting spring;

[0014] The coil skeleton is located inside the pendulum body shell and is fixedly connected to the pendulum body shell, is in a hollow cylindrical shape, is sleeved outside the inertial mass block, and is coaxial with the inertial mass block;

[0015] The multi-turn coil is arranged outside the coil skeleton and is coaxial with the coil skeleton;

[0016] The signal amplification circuit is electrically connected to the two ends of the multi-turn coil at the input end and outputs a voltage signal at the output end.

[0017] On the basis of the above technical scheme, preferably, the spring of the pick-up is made of stainless steel.

[0018] On the basis of the above technical scheme, preferably, the IP level of the metal shell is IP67.

[0019] On the basis of the above technical scheme, preferably, the signal circuit conversion box is further included;

[0020] The pick-up is electrically connected to the signal circuit conversion box.

[0021] Further preferably, the pick-up is connected to the signal circuit conversion box through a nuclear-grade cable.

[0022] On the basis of the above technical scheme, preferably, the signal circuit conversion box uses a double-layer tungsten-nickel alloy as the shell, and the shell is lined with high-melting-point polytetrafluoroethylene wax.

[0023] The nuclear safety level anti-radiation seismic accelerometer of the application has the following beneficial effects compared with the prior art:

[0024] (1) By setting 6 pickers to measure the acceleration value of three axial directions in horizontal and vertical directions, 2 pickers are oppositely arranged on the coaxial line in each measuring direction, and the two pickers are backup for each other. Due to the different placement directions, the nuclear radiation intensity received by each pick-up will be different. When one of the pickers is damaged due to nuclear radiation, the backup pick-up can still work normally and output the seismic acceleration value, thereby enhancing the anti-radiation capability of the seismic accelerometer in the radiation environment, so that the seismic accelerometer can work in the nuclear reactor for a long time.

[0025] (2) The pick-up is realized by using the structure principle of combination of capacitive isolation and electromagnetic coil. It can respond to very low seismic frequency, and due to the existence of DC isolation of the capacitor, the pick-up does not respond to 0Hz signal and does not output static current noise signal, that is, the static current noise and zero drift problems caused by radiation effect are isolated in principle.

[0026] (3) The IP level of the metal shell is IP67, which further enhances the performance of the pick-up in high temperature and high humidity environment and nuclear radiation shielding. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0028] Figure 1 It is a perspective view of the nuclear safety level anti-radiation seismic accelerometer of the present application.

[0029] Figure 2 It is a structure principle diagram of the pick-up of the present application. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be described in detail below. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0031] As shown in the figure, the nuclear safety level anti-radiation seismic accelerometer of the present application comprises: Figure 1

[0032] The bottom plate 1, the metal base 2, the 6 pickers 3 and the metal shell. ​

[0033] The bottom plate 1 is a rectangular plate, the height of the middle part of the upper surface is greater than the height of the two ends of the upper surface, and the middle part of the upper surface and the two ends of the upper surface form steps, respectively;

[0034] The metal base 2 is a square, the middle part of the lower surface is inwardly recessed to form a hollow part, the hollow part and the two ends of the lower surface form two support parts, and the two support parts are arranged on the middle part of the upper surface of the bottom plate 1;

[0035] 6 The vibration pick-up 3 is arranged at the center of each of the six faces of the metal base 2, and the central axis of each vibration pick-up 3 coincides with the central axis of the face;

[0036] The metal shell is adapted to the shape of the bottom plate 1 and the metal base 2, and is used to cover the bottom plate 1, the metal base 2 and the six vibration pick-ups 3.

[0037] Since the nuclear radiation of the nuclear power plant has directionality (all from the reactor fuel to the surrounding radiation, and the radiation intensity is the largest towards the fuel rod direction), the nuclear safety level anti-radiation seismic accelerometer of the embodiment adopts six vibration pick-ups 3 to measure the acceleration values in three axial directions of horizontal and vertical directions, and two vibration pick-ups 3 are arranged in opposite directions on the same axis in each measurement direction, and the two vibration pick-ups 3 are backup for each other. Since the orientations are different, the nuclear radiation intensity received by each vibration pick-up 3 will be different. When one of the vibration pick-ups 3 is damaged due to nuclear radiation, the backup vibration pick-up 3 can still work normally and output the seismic acceleration value, thereby enhancing the anti-radiation capability of the seismic accelerometer in the radiation environment, so that the seismic accelerometer can work in the nuclear reactor for a long time.

[0038] As shown in the formula (1), the vibration pick-up 3 includes: Figure 2

[0039] The pendulum body shell 4, two support springs 5, an inertial mass 6, a coil frame 7, a multi-turn coil 8 and a signal amplification circuit 9;

[0040] The inertial mass 6 is located inside the pendulum body shell 4 and is cylindrical, the upper surface is connected to the lower surface of the top of the pendulum body shell 4 through one of the support springs 5, and the lower surface is connected to the upper surface of the bottom of the pendulum body shell 4 through the other support spring 5;

[0041] The coil frame 7 is fixedly connected to the pendulum body shell 4 and is hollow cylindrical, is located inside the pendulum body shell 4, is located outside the inertial mass 6, and is coaxial with the inertial mass 6;

[0042] The multi-turn coil 8 is located outside the coil frame 7 and is coaxial with the coil frame 7;

[0043] The signal amplification circuit 9 is electrically connected to the two ends of the multi-turn coil 8 through the input end, and outputs a voltage signal through the output end.​

[0044] In order to further enhance the anti-radiation ability of the seismic accelerometer, the pick-up 3 of the nuclear safety level anti-radiation seismic accelerometer of the embodiment adopts the structural principle of the combination of capacitive isolation and electromagnetic coil to realize, and the principle structure is shown in Figure 2 As shown, the main structure of the pick-up 3 is composed of an inertial mass 6, a multi-turn coil 8, a coil skeleton 7 and a support spring 5, the inertial mass 6 is connected with the pendulum body shell 4 of the pick-up 3 through the upper and lower support springs 5, the coil skeleton 7 and the multi-turn coil 8 are fixed together with the pendulum body shell 4 and connected with the metal base 2 of the acceleration sensor as a whole; the inertial mass 6 is made of permanent magnet steel, and has a cylindrical structure, the coil skeleton 7 has a cylindrical structure and is coaxial with the inertial mass 6, and a cylindrical capacitive structure is formed between the two, wherein R g is the equivalent resistance of the multi-turn coil, and C is the equivalent isolation capacitor. When the metal base 2 of the acceleration sensor vibrates up and down under the action of ground vibration, it will drive the pendulum body shell 4 and the coil skeleton 7 to move synchronously, while the inertial mass 6 will remain in a relatively static position, forming relative motion. At this time, the multi-turn coil 8 on the coil skeleton 7 will cut the magnetic line to produce electromagnetic effect, output induced current, and the change of current has the same phase relationship with ground motion. After shaping and amplification by the signal amplification circuit 9, the output voltage signal U0 is in one-to-one correspondence with the ground vibration acceleration. Since there is a capacitive isolation in the loop of the induced current, when the ground motion is static or the frequency is extremely low, the current signal generated is isolated. Therefore, the nuclear safety level anti-radiation seismic accelerometer of the embodiment eliminates the external ultra-low frequency disturbance in structure, and there is no mechanical zero offset problem.

[0045] According to Figure 2 and related parameters, the acceleration dynamic equation of the combined structure can be given, and the specific calculation process is as follows:

[0046] According to Figure 2 , and ignoring air damping, the motion equation can be obtained:

[0047]

[0048] In the formula, m is the mass of the seismic accelerometer pendulum body, b is the mechanical damping coefficient, k is the spring stiffness coefficient, x is the moving coil displacement of the seismic accelerometer under external excitation, y is the actual displacement of the external monitoring point, F b is the ampere force received by the coil (y is the actual running distance of the outside, and x is the forced response displacement of the mass body inside the pick-up).

[0049] F b = BLi (2)

[0050] In the formula, i is the moving coil current, according to... Figure 1 The following circuit parameter relationships can be derived:

[0051]

[0052] In the formula, R c R is the capacitance impedance. i This is the internal resistance of the coil.

[0053] Ignoring air damping and mechanical damping, by combining equations (1)-(3) and performing a Laplace transform, we can solve the equations to obtain:

[0054]

[0055]

[0056]

[0057] In the formula, R = R c +R i As can be seen from equation (6), the seismic accelerometer is a typical coil pendulum accelerometer. Equation (6) is its second-order conduction equation. Within its operating frequency range, the acceleration measured by the accelerometer is proportional to the output voltage signal.

[0058] As can be seen from the dynamic equation, the seismic pickup 3 of this structure can respond to very low seismic frequencies. Also, due to the DC isolation of the capacitor, the seismic pickup 3 does not respond to 0Hz signals and does not output static current noise signals. In principle, it isolates the static current noise and zero-point drift problem caused by radiation effect.

[0059] The spring of the vibration pickup 3 is made of stainless steel.

[0060] The spring of the vibration pickup 3 is made of stainless steel, and the surface of the magnet is chrome-plated to enhance the corrosion resistance of the material.

[0061] The metal casing has an IP rating of IP67.

[0062] Six vibration sensors 3 are embedded and fixed within a metal base 2, and together with it are sealed within a metal casing. Figure 1 (The metal casing is not shown in the image). The IP rating of the metal casing is IP67, which further enhances the performance of the shock absorber 3 in high temperature and high humidity environments as well as nuclear radiation shielding.

[0063] This also includes a signal circuit conversion box;

[0064] The vibration pickup 3 is electrically connected to the signal circuit conversion box.

[0065] The pick-up 3 is connected with the signal circuit conversion box through a nuclear grade cable.

[0066] The acceleration signals collected by the six pick-ups 3 of the seismic accelerometer are transmitted to the signal circuit conversion box through a nuclear grade cable, so as to facilitate signal conversion.

[0067] The signal circuit conversion box uses double-layer tungsten-nickel alloy as the shell, and the shell is lined with high-melting-point polytetrafluoroethylene wax.

[0068] Since the signal circuit conversion box can be installed and fixed in other installation spaces with sufficient space, the shell thereof can be moderately thickened, so the signal circuit conversion box uses 20mm-thick double-layer tungsten-nickel alloy as the shell, which greatly attenuates the surrounding nuclear radiation intensity, and the double-layer shell is filled with high-melting-point polytetrafluoroethylene wax, which can strongly absorb the slow neutron radiation in the nuclear reactor, so that the whole can resist a total radiation dose of 25Mrad in the nuclear reactor after the shielding measures, and effectively shield the slow neutron radiation in the reactor.

[0069] The nuclear safety level anti-radiation seismic accelerometer in the embodiment adopts six pick-ups 3 to measure the acceleration values in the horizontal direction and the vertical direction of three axial directions, two pick-ups 3 are oppositely arranged on the coaxial line in each measurement direction, and the two pick-ups 3 are backups of each other. Since the orientations are different, the nuclear radiation intensities received by the pick-ups 3 will be different. When one of the pick-ups 3 is damaged due to nuclear radiation, the backup pick-up 3 can still work normally and output the seismic acceleration value, thereby enhancing the anti-radiation capability of the seismic accelerometer in the radiation environment, so that the seismic accelerometer can work in the nuclear reactor for a long time.

[0070] The above only describes the preferred embodiments of the present application and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A nuclear safety class radiation-hardened seismometer accelerometer, characterized by: The nuclear safety level anti-radiation seismic accelerometer comprises: a bottom plate (1), a metal base (2), six seismic pick-ups (3) and a metal shell; the bottom plate (1) is a rectangular plate, the height of the middle part of the upper surface is greater than the height of the two ends of the upper surface, and the middle part of the upper surface and the two ends of the upper surface form steps, respectively; the metal base (2) is a square, the middle part of the lower surface is inwardly recessed to form a hollow part, the hollow part and the two ends of the lower surface form two support parts, and the two support parts are arranged on the middle part of the upper surface of the bottom plate (1); six seismic pick-ups (3) are arranged at the centers of the six faces of the metal base (2), respectively, and the central axis of each seismic pick-up (3) coincides with the central axis of the face of the metal base (2) where the seismic pick-up (3) is arranged; the metal shell is adapted to the shapes of the bottom plate (1) and the metal base (2), and is used for covering the bottom plate (1), the metal base (2) and the six seismic pick-ups (3); the seismic pick-up (3) comprises: a pendulum body shell (4), two support springs (5), an inertial mass (6), a coil framework (7), a multi-turn coil (8) and a signal amplification circuit (9); the inertial mass (6) is located inside the pendulum body shell (4) and is in a cylindrical shape, the upper surface of the inertial mass (6) is connected to the top lower surface of the pendulum body shell (4) through one of the two support springs (5), and the lower surface of the inertial mass (6) is connected to the bottom upper surface of the pendulum body shell (4) through the other support spring (5); the coil framework (7) is fixedly connected to the pendulum body shell (4) and is in a hollow cylindrical shape, is arranged outside the inertial mass (6) and is coaxial with the inertial mass (6); the multi-turn coil (8) is arranged outside the coil framework (7) and is coaxial with the coil framework (7); the signal amplification circuit (9) is electrically connected to the two ends of the multi-turn coil (8) through the input end and outputs a voltage signal through the output end; ignoring air damping and mechanical damping, after a pull-type transformation, the equation is solved, and the following equation is obtained: U b (s) = BLsx (4) where R = R c +R i As can be seen from equation (6), the seismic accelerometer is a typical coil pendulum accelerometer, equation (6) is its second-order transfer equation, and in its working frequency range, the monitored acceleration quantity is proportional to the output voltage signal. the seismic pick-up (3) can respond to very low seismic frequencies, and due to the existence of the capacitor, the seismic pick-up (3) does not respond to 0Hz signals and does not output static current noise signals, and the static current noise and zero drift generated due to the radiation effect are isolated.

2. The nuclear safety class radiation-hardened seismometer accelerometer of claim 1, wherein: The spring of the seismic pick-up (3) is made of stainless steel.

3. The nuclear safety class radiation-hardened seismometer accelerometer of claim 1, wherein: The IP level of the metal shell is IP67.

4. The nuclear safety class radiation-hardened seismometer accelerometer of claim 1, wherein: a signal circuit conversion box is further included; the seismic pick-up (3) is electrically connected to the signal circuit conversion box.

5. The nuclear safety class radiation-hardened seismometer accelerometer of claim 4, wherein: the seismic pick-up (3) is connected to the signal circuit conversion box through a nuclear level cable.

6. The nuclear safety class radiation-hardened seismometer accelerometer of claim 4, wherein: the signal circuit conversion box uses a double-layer tungsten-nickel alloy as the shell, and the shell is lined with high-melting-point polytetrafluoroethylene wax.

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