Measuring device for on-line measurement of alpha radioactive activity concentration in spent fuel wastewater

Abstract

The invention relates to a measuring device for on-line measurement of alpha radioactive activity concentration in spent fuel wastewater, which comprises a supporting base, a liquid receiving tray is arranged at the top of the supporting base, a liquid inlet pump and a liquid discharge pump are hung on the outer side of one end of the liquid receiving tray at intervals, and a sealed junction box is hung on the outer side of the other end of the liquid receiving tray; the liquid inlet pump is also communicated with the constant liquid level front tank through a pipeline; a supporting frame is arranged in an inner cavity of the liquid receiving disc, a liquid storage tank is fixedly connected to the inner side of the top of the supporting frame, a first liquid level meter, a second liquid level meter and a third liquid level meter are connected to the liquid storage tank, and the bottom of the liquid storage tank is further communicated with a liquid discharging pump through a pipeline; the outer side of the top of the support frame is fixedly connected with a measuring tank; the bottom of the measuring tank is communicated with the top of the liquid storage tank; a roll film driving mechanism is arranged at the top of the measuring cell, a roll film is arranged on the roll film driving mechanism, and a detector is arranged at the top of the roll film driving mechanism. According to the invention, various problems of off-line measurement can be effectively solved, and on-line measurement of the alpha activity concentration in the high-concentration acidic liquid is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of radioactive wastewater monitoring, and in particular relates to a measuring device for online measuring the alpha radioactivity concentration in spent fuel wastewater. Background Art

[0002] During the spent fuel treatment process, a large amount of alpha radioactive waste liquid containing high-concentration acidic liquid is generated. Since the alpha activity concentration in the waste liquid can directly or indirectly reflect the operating status of the post-processing process, and in order to ensure the safety of personnel and the environment, it is necessary to monitor the alpha activity concentration of the radioactive waste liquid. Traditional measurement methods usually use offline analysis and detection, that is, after sampling the waste liquid, samples are obtained through repeated evaporation, modulation, extraction and other chemical methods, and then the samples are analyzed and measured to obtain the activity concentration. The disadvantage of this offline measurement method is that it cannot measure the waste liquid in real time. The offline measurement method is cumbersome, has poor timeliness, and a small sampling volume. At the same time, personnel are required to take samples from the process pipeline regularly, which increases the risk of personnel exposure and environmental pollution. Summary of the invention

[0003] In view of the shortcomings of the prior art, the present invention provides a measuring device for online measuring the α radioactivity concentration in spent fuel wastewater. On the basis of meeting the measurement accuracy, it has the advantages of large measuring area, strong acid resistance, reasonable operation logic, simple operation steps, etc. It can effectively solve various problems of offline measurement and realize the online measurement of α activity concentration in high-concentration acidic liquid.

[0004] In order to achieve the above object, the technical solution of the present invention is:

[0005] A measuring device for online measuring the alpha radioactivity concentration in spent fuel wastewater comprises a supporting base, a liquid receiving tray is arranged on the top of the supporting base, a liquid inlet pump and a liquid discharge pump are hung at intervals on the outer side of one end of the liquid receiving tray, and a sealed junction box is hung on the outer side of the other end; the liquid inlet pump and the liquid discharge pump are electrically connected to the sealed junction box respectively, and the liquid inlet pump is also connected to a constant liquid level pre-tank through a pipeline;

[0006] A support frame is provided in the inner cavity of the liquid receiving tray, and a liquid storage tank is fixedly connected to the inner side of the top of the support frame, and the first liquid level gauge, the second liquid level gauge and the third liquid level gauge are respectively connected to the liquid storage tank, and the bottom of the liquid storage tank is also connected to the drainage pump through a pipeline; a measuring tank is fixedly connected to the outer side of the top of the support frame, and the bottom of the measuring tank is connected to the top of the liquid storage tank;

[0007] The inner cavity of the measuring pool is provided with a water circuit baffle coiled from the center to the outside, and a water outlet is provided at the center of the innermost circle of the water circuit baffle, and the water outlet is connected to the top of the liquid storage tank; the outermost circle of the water circuit baffle is provided with a water inlet, and the water inlet is connected to the liquid inlet pump through a pipeline;

[0008] A film roll driving mechanism is provided on the top of the measuring pool, a film roll for blocking radioactive waste liquid is provided on the film roll driving mechanism, a detector is provided on the top of the film roll driving mechanism, and a gap is left between the bottom of the detector and the top of the film roll.

[0009] Preferably, the detector comprises a detector housing, a flat cover plate is arranged in the detector housing, a photoelectric detector is arranged on the top of the flat cover plate, and a detector electronic unit connected to the photoelectric detector, and one end of the photoelectric detector is connected to a fiber collimation coupling body;

[0010] A detector bottom frame is provided at the bottom of the plane cover plate, a light shielding film is provided inside the detector bottom frame, a scintillator is provided at the top of the detector bottom frame, a fiber fixing frame is provided at the top of the scintillator, a plurality of scintillating optical fibers are arranged in a U-shape and equidistantly in sequence on the fiber fixing frame, and the ends of the scintillating optical fibers pass through the plane cover plate and are connected to the optical fiber collimation coupling body;

[0011] A light guide is provided on the top of the optical fiber fixing frame, a light reflecting layer is provided on the top of the light guide, and the top surface of the light reflecting layer is connected to the bottom surface of the plane cover plate;

[0012] A detector waterproof power supply connector and a detector waterproof communication connector are respectively provided on the side of the detector housing. The detector waterproof power supply connector, the detector waterproof communication connector, and the sealed junction box are all electrically connected to the detector electronic unit.

[0013] Preferably, the film roll driving mechanism includes a driving bracket, and rotating rods are respectively provided at both ends of the driving bracket, and the two ends of the film roll are respectively rolled on the rotating rods at both ends of the driving bracket; one end of the two rotating rods is connected to a rotating wheel, and the rotating wheel is exposed on one side of the driving bracket.

[0014] Preferably, the roll film is made of a 2.4 μm thick polyester fiber film.

[0015] Preferably, the support base comprises a planar base and support shafts disposed at four positions on the top of the planar base, and the liquid receiving tray is disposed on the top of the support shafts.

[0016] Preferably, a liquid drain port is provided at the center of the bottom of the liquid receiving tray, and a fourth liquid level gauge for monitoring the amount of liquid in the liquid receiving tray is also provided at the bottom of the inner cavity of the liquid receiving tray.

[0017] Preferably, a fifth liquid level gauge is installed on one side of the lower middle portion of the constant liquid level pre-tank, and the top of the constant liquid level pre-tank is also connected to an overflow pipeline.

[0018] Preferably, the shading film is made of polished titanium foil, and its reflectivity to wavelengths of 400nm to 700nm is ≥70%.

[0019] Preferably, the scintillating optical fiber is a plastic wave-shifting optical fiber;

[0020] The optical fiber fixing frame is made of acrylic material, and a plurality of optical fiber positioning holes for inserting the flashing optical fiber are opened at equal intervals at both ends thereof. The two ends of the flashing optical fiber are respectively inserted into two adjacent optical fiber positioning holes at one end of the optical fiber fixing frame, and are inserted out from two corresponding optical fiber positioning holes at the other end of the optical fiber fixing frame.

[0021] Preferably, the scintillator is a ZnS plastic scintillator, and its peak emission wavelength is 423nm;

[0022] The light reflection layer is made of aluminum-plated film, and its light reflectivity in the wavelength range of 400nm to 500nm is ≥90%.

[0023] Technical effects and advantages of the present invention:

[0024] 1. The present invention provides a measuring device for online measuring the alpha radioactivity concentration in spent fuel wastewater. The device has a combined structure of a constant liquid level pre-tank, a liquid inlet pump, a liquid discharge pump, a support frame, a liquid storage tank, a measuring tank, a roll film and a detector. The device is ingeniously designed. On the basis of meeting the measurement accuracy, the device has the advantages of large measurement area, strong acid resistance, reasonable operation logic, simple operation steps, etc. It can effectively solve various problems of offline measurement and realize the online measurement of the alpha activity concentration in high-concentration acidic liquid.

[0025] The water circuit baffle in the measuring pool adopts a spiral structure, which ensures that the liquid quickly fills the measuring pool while avoiding the occurrence of problems such as liquid overflow, unevenness, and unstable flow rate as much as possible;

[0026] Since the detector uses multiple optical fibers to cover the measuring surface, the uniformity is good. The detector also uses ultra-thin titanium foil as the light-shielding surface and light-reflecting surface. While ensuring the detection efficiency, it has strong acid resistance and high α detection efficiency.

[0027] The roll film of the present application adopts an ultra-thin polyester fiber film, which has good stretchability and acid resistance, and is a good material for isolating the detector from contact with acidic liquid;

[0028] By installing an acid-proof liquid level gauge on the liquid storage tank, a highly feasible linkage type radioactive liquid online measurement method is realized. This method can effectively achieve the flow balance of the measured liquid, and at the same time fully consider the occurrence of unexpected situations to ensure the normal operation of the equipment;

[0029] A liquid receiving tray is provided to collect liquids spilled due to accidents and to connect the liquid inlet pump and the liquid discharge pump. The liquid receiving tray is longer and wider than the components on it, and can fully collect the spilled liquids. It is also connected to the base and has good bearing capacity.

[0030] The liquid inlet pump and liquid discharge pump of the present application use a speed-adjustable acid-proof micro magnetic drive gear pump. The speed-adjustable function of the pump meets the requirements of the linkage type radioactive liquid online measurement method. The acid-proof micro feature is highly consistent with the use requirements of the post-processing process site;

[0031] By setting up a constant liquid level pre-tank, the problem of unstable liquid flow pressure in the process pipeline is solved. Using a constant liquid level pre-tank of appropriate size to first collect the liquid in the process pipeline and then pump the liquid into the measuring pool can effectively ensure the stable operation of the liquid inlet pump and eliminate the impact of the process pipeline on the operation of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a three-dimensional structural schematic diagram of the present invention;

[0033] Figure 2 It is a schematic diagram of the structure of a partial explosion of the structure of the present invention;

[0034] Figure 3 It is a schematic diagram of the explosion structure of the internal structure of the detector of the present invention.

[0035] Reference numerals: 1, support base; 2, detector; 3, support frame; 4, film roll; 5, measuring cell; 6, liquid storage tank; 7, first liquid level gauge; 8, second liquid level gauge; 9, third liquid level gauge; 10, liquid receiving tray; 12, liquid inlet pump; 13, liquid discharge pump; 14, sealed junction box; 15, constant liquid level front tank; 16, fifth liquid level gauge; 17, liquid discharge port; 18, film roll driving mechanism; 19, driving bracket; 20, rotating wheel;

[0036] 21. Detector housing; 22. Flat cover plate; 23. Detector bottom frame; 24. Shading film; 25. Scintillating optical fiber; 26. Optical fiber fixing frame; 27. Scintillator; 28. Light guide; 29. ​​Light reflecting layer; 210. Photoelectric detector; 211. Detector waterproof power supply connector; 212. Detector electronic unit; 213. Optical fiber alignment coupler; 214. Detector waterproof communication connector. DETAILED DESCRIPTION

[0037] The present invention is further described in detail below with reference to the embodiments given in the accompanying drawings.

[0038] See also Figure 1 to Figure 3 As shown, a measuring device for online measuring the alpha radioactivity concentration in spent fuel wastewater comprises a supporting base 1, a liquid receiving tray 10 is arranged on the top of the supporting base 1, a liquid inlet pump 12 and a liquid discharge pump 13 are hung at intervals on the outer side of one end of the liquid receiving tray 10, and a sealed junction box 14 is hung on the outer side of the other end; the liquid inlet pump 12 and the liquid discharge pump 13 are electrically connected to the sealed junction box 14 respectively, and the liquid inlet pump 12 is also connected to a constant liquid level pre-tank 15 through a pipeline;

[0039] A support frame 3 is provided in the inner cavity of the liquid receiving tray 10, and a liquid reservoir 6 is fixedly connected to the inner side of the top of the support frame 3, and the first liquid level gauge 7, the second liquid level gauge 8 and the third liquid level gauge 9 are respectively connected to the liquid reservoir 6, and the bottom of the liquid reservoir 6 is also connected to the drainage pump 13 through a pipeline; a measuring tank 5 is fixedly connected to the outer side of the top of the support frame 3, and the bottom of the measuring tank 5 is connected to the top of the liquid reservoir 6;

[0040] The inner cavity of the measuring pool 5 is provided with a water circuit baffle 51 winding from the center to the outside, and a water outlet is provided at the center of the innermost circle of the water circuit baffle 51, and the water outlet is connected to the top of the liquid storage tank 6; the outermost circle of the water circuit baffle 51 is provided with a water inlet, and the water inlet is connected to the liquid inlet pump 12 through a pipeline;

[0041] A film roll driving mechanism 18 is provided on the top of the measuring pool 5 , on which a film roll 4 for blocking radioactive waste liquid is provided. A detector 2 is provided on the top of the film roll driving mechanism 18 , and a gap is left between the bottom of the detector 2 and the top of the film roll 4 .

[0042] In this embodiment, the water sample flows along the measuring tank 5 loop and finally freely falls into the liquid storage tank 6 below the measuring tank 5. When the liquid level in the liquid storage tank 6 is only at the position of the first liquid level gauge 7, the system starts the drainage pump 13 to prevent the water sample from overflowing the liquid storage tank 6. When the liquid level in the liquid storage tank 6 is at the position of the second liquid level gauge 8 or between the second liquid level gauge 8 and the first liquid level gauge 7, the inlet pump 12 and the drainage pump 13 are started at the same time to maintain simultaneous liquid inflow and outflow. When the liquid level in the liquid storage tank 6 is at the position of the third liquid level gauge 9 or between the third liquid level gauge 9 and the second liquid level gauge 8, only the inlet pump 12 is started to prevent the liquid levels in the measuring tank 5 and the liquid storage tank 6 from being too low.

[0043] In this embodiment, the first liquid level gauge 7, the second liquid level gauge 8 and the third liquid level gauge 9 are all acid-proof liquid level gauges.

[0044] In this embodiment, the inlet pump 12 and the discharge pump 13 are the same acid-proof micro magnetic drive gear pumps, and both pumps can be automatically started and stopped according to the working logic of the device or can be started and stopped autonomously by manually entering the manual mode.

[0045] In this embodiment, the film roll driving mechanism 18 includes a driving bracket 19, and the two ends of the driving bracket 19 are respectively provided with rotating rods, and the two ends of the film roll 4 are respectively rolled on the rotating rods at the two ends of the driving bracket 19; one end of the two rotating rods is connected to a rotating wheel 20, and the rotating wheel 20 is exposed on one side of the driving bracket 19.

[0046] In this embodiment, the roll film 4 is made of a 2.4 μm thick polyester fiber film.

[0047] In specific implementation, a polyester fiber film is used to prevent radioactive waste liquid from contaminating the detector surface. When the polyester fiber film is used for a long time or is contaminated, the film rolling mechanism can be manually adjusted by the rotating wheel 20 to drive the film to move, so as to restore the background measurement value of the detector.

[0048] In this embodiment, the support base 1 includes a planar base and support shafts disposed at four positions on the top of the planar base. The liquid receiving tray 10 is disposed on the top of the support shafts to stably support the entire measuring device.

[0049] In this embodiment, a liquid discharge port 17 is provided at the center of the bottom of the liquid receiving tray 10 , and a fourth liquid level gauge for monitoring the amount of liquid in the liquid receiving tray 10 is also provided at the bottom of the inner cavity of the liquid receiving tray 10 .

[0050] In specific implementation, the liquid receiving tray 10 is made of stainless steel. The liquid receiving tray 10 is used to collect liquids that overflow due to accidents and to connect the liquid inlet pump 12, the liquid discharge pump 13 and the sealed junction box 14. When there is liquid in the liquid receiving tray 10, the liquid can flow out to the waste liquid collection process pipeline through the liquid discharge port 17 in the center of the liquid receiving tray 10. The fourth liquid level gauge serves as a safety for the measurement device. If the liquid level in the liquid receiving tray 10 is at or exceeds the fourth liquid level gauge position, the system alarms and stops the liquid inlet pump 12 and the liquid discharge pump 13.

[0051] In this embodiment, a fifth liquid level gauge 16 is installed on one side of the lower middle portion of the constant liquid level pre-tank (15), and the top of the constant liquid level pre-tank (15) is also connected to an overflow pipeline.

[0052] During specific implementation, the process liquid inlet pipeline continuously feeds liquid into the constant liquid level pre-tank 15. To avoid empty pumping, the liquid inlet pump 12 is started only when the liquid level reaches the position of the liquid level gauge 16 or exceeds the position of the liquid level gauge 16 (Note: the logic priority of starting the liquid inlet pump 12 here is higher than the logic priority of starting the liquid inlet pump 12 controlled by the liquid level gauge contained in the liquid storage tank 6).

[0053] In this embodiment, see Figure 3 As shown, the detector 2 includes a detector housing 21, a flat cover plate 22 is provided in the detector housing 21, a photodetector 210 is provided on the top of the flat cover plate 2, and a detector electronic unit 212 connected to the photodetector 210, and one end of the photodetector 210 is connected to a fiber collimation coupling body 213;

[0054] A detector bottom frame 23 is provided at the bottom of the plane cover plate 22, a light shielding film 24 is provided inside the detector bottom frame 23, a scintillator 27 is provided at the top of the detector bottom frame 23, a fiber fixing frame 26 is provided at the top of the scintillator 27, a plurality of scintillating optical fibers 25 are arranged in a U-shape and equidistantly in sequence on the fiber fixing frame 26, and the ends of the scintillating optical fibers 25 pass through the plane cover plate 22 and are connected to the optical fiber collimation coupling body 213;

[0055] A light guide 28 is disposed on the top of the optical fiber fixing frame 26, and a light reflecting layer 29 is disposed on the top of the light guide 28. The top surface of the light reflecting layer 29 is connected to the bottom surface of the flat cover plate 22.

[0056] The detector housing 21 is provided with a detector waterproof power supply connector 211 and a detector waterproof communication connector 214 on the side thereof. The detector waterproof power supply connector 211 and the detector waterproof communication connector 14 , as well as the sealed junction box 14 , are all electrically connected to the detector electronic unit 212 .

[0057] In this embodiment, the shading film 24 is made of polished titanium foil, the thickness of the titanium foil is 5 μm, and metallic titanium has excellent resistance to oxidizing acids, especially to nitric acid which is often present in the field of nuclear detection. When the acidic gas / liquid contacts the shading film 24, the shading film 24 can block the acidic gas / liquid for a long time without being corroded and penetrated. It also has good reflective ability, with a reflectivity of ≥70% for wavelengths of 400nm to 700nm, and can reflect the scintillation light emitted by the plastic scintillator 27, thereby further improving the efficiency of the detector.

[0058] In this embodiment, the scintillating optical fiber 25 is a plastic wave-shifting optical fiber, which has the characteristics of having a high absorption rate for light incident from the side of the optical fiber and the scintillation light emitted by the plastic scintillator 27, and can also change the wavelength of the outgoing light, making the outgoing light more suitable for detection by the photodetector 210.

[0059] In this embodiment, the optical fiber fixing frame 26 is made of acrylic material, and a plurality of optical fiber positioning holes for inserting the scintillation optical fiber 25 are opened at equal intervals at both ends thereof. The two ends of the scintillation optical fiber 25 are respectively inserted from two adjacent optical fiber positioning holes at one end of the optical fiber fixing frame 26, and exit from two corresponding optical fiber positioning holes at the other end of the optical fiber fixing frame 26; the ends of all the scintillation optical fibers 25 are gathered into a bundle at the exit, and after being bent with a suitable bending radius, enter the optical fiber collimation coupling body 213, contact the photodetector 210 and transmit light into the photodetector 210.

[0060] In this embodiment, the scintillator 27 is a ZnS plastic scintillator, and the peak emission wavelength thereof is 423 nm.

[0061] In this embodiment, the light reflection layer 29 is made of an aluminum-plated film, and its light reflectivity in the wavelength range of 400nm to 500nm is ≥90%.

[0062] When the present invention is used, the pump and the liquid level meter are powered through the detector waterproof power supply connector 211 and the detector waterproof communication connector 214, and the detector 2 is supplied with 12V power and RS485 communication is performed. After the detector 2 is powered on, the α dose rate in the measuring pool 5 below it can be detected in real time, and the liquid inlet pipeline continuously inputs the amount concentration of the substance 7mo into the constant liquid level front tank 15. l / L uranium nitrate liquid. If the liquid level of the constant liquid level pre-tank 15 is too high, the liquid can be discharged through the overflow pipe of the constant liquid level pre-tank 15. When the liquid level reaches the position of the liquid level gauge 16 or exceeds the position of the liquid level gauge 16, the liquid inlet pump 12 is started to make the liquid flow into the measuring cell 5. The running speed of the liquid inlet pump 12 is adjustable (the speed 0r / min-6000r / min corresponds to the power supply voltage 0V-24V, and the corresponding relationship between the two is linear). In order to avoid liquid overflow caused by excessive liquid inlet, the liquid inlet pump 12 of this embodiment is powered by 5V, corresponding to a speed of 1,250r / min. A 2.4μm polyester fiber membrane that does not contact the detector surface is arranged between the measuring cell 5 and the detector 3. After the membrane has been used for a specific period of time or is contaminated, it is manually moved by the film rolling mechanism 18 to restore the detection The background measurement value of the detector 2, at this time, the liquid flows in a spiral along the water circuit of the measuring pool 5, and finally covers the entire measuring pool 5 and continues to flow into the liquid storage tank 6, ensuring that the liquid level of the measuring pool 5 is high (the degree of α-ray attenuation is highly related to the distance) and there is no overflow. When the liquid in the liquid storage tank 6 gradually accumulates and reaches the position of the liquid level gauge 7, in order to ensure that the liquid does not overflow the liquid storage tank 6, the liquid discharge pump 13 is started. The liquid discharge pump 13 adopts an acid-proof micro-magnetic drive gear pump consistent with the liquid inlet pump 12, and adopts 24V power supply, corresponding to a speed of 6000r / min. When the liquid level is pumped down to the position of the liquid level gauge 8 or between the liquid level gauge 8 and the liquid level gauge 7, the power supply of the liquid discharge pump 13 becomes 5V power supply, corresponding to a speed of 1250r / min, that is, the same as the speed of the liquid inlet pump 12, to achieve liquid inlet and outlet balance. For some reasons (such as the equipment has not been used for a long time, started and stopped midway, or after the pump is operated in manual mode), when the liquid level in the liquid storage tank 6 is at the position of the liquid level gauge 9 or between the positions of the liquid level gauge 9 and the liquid level gauge 8, only the liquid inlet pump 12 is started. The liquid inlet pump 12 is powered by 5V and has a corresponding speed of 1,250r / min to ensure that the liquid flow quickly enters the linkage working state and restores the normal measurement work of the equipment. In addition, when the liquid overflows due to unexpected circumstances, there is also a liquid receiving tray 10 to collect the overflowed liquid and quickly discharge the liquid through the liquid outlet 17.

[0063] The above is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several modifications and improvements without departing from the inventive concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A measuring device for online measuring the α radioactivity concentration in spent fuel wastewater, characterized by: The invention comprises a support base (1), wherein a liquid receiving pan (10) is provided on the top of the support base (1), a liquid inlet pump (12) and a liquid discharge pump (13) are hung at intervals on the outside of one end of the liquid receiving pan (10), and a sealed junction box (14) is hung on the outside of the other end; the liquid inlet pump (12) and the liquid discharge pump (13) are respectively electrically connected to the sealed junction box (14), and the liquid inlet pump (12) is also connected to a constant liquid level pre-tank (15) through a pipeline; A support frame (3) is provided in the inner cavity of the liquid receiving tray (10); a liquid storage tank (6) is fixedly connected to the inner side of the top of the support frame (3); a first liquid level gauge (7), a second liquid level gauge (8) and a third liquid level gauge (9) are respectively connected to the liquid storage tank (6); the bottom of the liquid storage tank (6) is also connected to a liquid discharge pump (13) through a pipeline; a measuring tank (5) is fixedly connected to the outer side of the top of the support frame (3); the bottom of the measuring tank (5) is connected to the top of the liquid storage tank (6); A water circuit baffle (51) is arranged in the inner cavity of the measuring pool (5) and is coiled from the center to the outside. A water outlet is arranged at the center of the innermost circle of the water circuit baffle (51), and the water outlet is connected to the top of the liquid storage pool (6); a water inlet is arranged at the outermost circle of the water circuit baffle (51), and the water inlet is connected to the liquid inlet pump (12) through a pipeline; A film roll drive mechanism (18) is provided on the top of the measuring pool (5), a film roll (4) for blocking radioactive waste liquid is provided on the film roll drive mechanism (18), a detector (2) is provided on the top of the film roll drive mechanism (18), and a gap is left between the bottom of the detector (2) and the top of the film roll (4).

2. The device for online measuring the α radioactivity concentration in spent fuel wastewater according to claim 1, characterized in that: The detector (2) comprises a detector housing (21), a flat cover plate (22) is arranged in the detector housing (21), a photoelectric detector (210) and a detector electronic unit (212) connected to the photoelectric detector (210) are arranged on the top of the flat cover plate (2), and one end of the photoelectric detector (210) is connected to an optical fiber collimation coupling body (213); A detector bottom frame (23) is provided at the bottom of the plane cover plate (22), a light shielding film (24) is provided inside the detector bottom frame (23), a scintillator (27) is provided at the top of the detector bottom frame (23), an optical fiber fixing frame (26) is provided at the top of the scintillator (27), a plurality of scintillating optical fibers (25) are arranged in a U-shape and equidistantly in sequence on the optical fiber fixing frame (26), and the ends of the scintillating optical fibers (25) pass through the plane cover plate (22) and are connected to the optical fiber collimation coupling body (213); A light guide (28) is provided on the top of the optical fiber fixing frame (26), a light reflection layer (29) is provided on the top of the light guide (28), and the top surface of the light reflection layer (29) is connected to the bottom surface of the plane cover plate (22); A detector waterproof power supply connector (211) and a detector waterproof communication connector (214) are respectively provided on the side of the detector housing (21); the detector waterproof power supply connector (211), the detector waterproof communication connector (14), and the sealed junction box (14) are all electrically connected to the detector electronic unit (212).

3. The device for online measuring the α radioactivity concentration in spent fuel wastewater according to claim 1, characterized in that: The film roll driving mechanism (18) comprises a driving bracket (19), and rotating rods are respectively provided at both ends of the driving bracket (19), and the two ends of the film roll (4) are respectively rolled on the rotating rods at both ends of the driving bracket (19); one end of each of the two rotating rods is connected to a rotating wheel (20), and the rotating wheel (20) is exposed on one side of the driving bracket (19).

4. The device for online measuring the α radioactivity concentration in spent fuel wastewater according to claim 3, characterized in that: The roll film (4) is made of a 2.4 μm thick polyester fiber film.

5. The device for online measuring the α radioactivity concentration in spent fuel wastewater according to claim 1, characterized in that: The support base (1) comprises a plane base and support shafts arranged at four positions on the top of the plane base, and the liquid receiving tray (10) is arranged on the top of the support shafts.

6. The device for online measuring the α radioactivity concentration in spent fuel wastewater according to claim 5, characterized in that: A liquid discharge port (17) is provided at the center of the bottom of the liquid receiving tray (10), and a fourth liquid level meter for monitoring the amount of liquid in the liquid receiving tray (10) is also provided at the bottom of the inner cavity of the liquid receiving tray (10).

7. The device for online measuring the α radioactivity concentration in spent fuel wastewater according to claim 1, characterized in that: A fifth liquid level gauge (16) is installed on one side of the lower middle portion of the constant liquid level pre-tank (15), and the top of the constant liquid level pre-tank (15) is also connected to an overflow pipeline.

8. The device for online measuring the α radioactivity concentration in spent fuel wastewater according to claim 2, characterized in that: The light-shielding film (24) is made of polished titanium foil, and its reflectivity to wavelengths of 400nm to 700nm is ≥70%.

9. The device for online measuring the α radioactivity concentration in spent fuel wastewater according to claim 8, characterized in that: The scintillating optical fiber (25) is a plastic wave-shifting optical fiber; The optical fiber fixing frame (26) is made of acrylic material, and has a plurality of optical fiber positioning holes for inserting the scintillation optical fiber (25) at equal intervals at both ends thereof. The two ends of the scintillation optical fiber (25) are inserted into two adjacent optical fiber positioning holes at one end of the optical fiber fixing frame (26) and exit from two corresponding optical fiber positioning holes at the other end of the optical fiber fixing frame (26).

10. The device for online measuring the α radioactivity concentration in spent fuel wastewater according to claim 8, characterized in that: The scintillator (27) is a ZnS plastic scintillator, and its luminescence wavelength peak is 423nm; The light reflection layer (29) is made of an aluminum-plated film, and its light reflectivity in the wavelength range of 400nm to 500nm is ≥90%.

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