H-3 online monitoring system and H-3 online monitoring method

Abstract

The invention discloses an H-3 online monitoring system and an H-3 online monitoring method. The H-3 online monitoring system comprises a flow chamber, a porous plastic scintillator and a detection device, the porous plastic scintillator is arranged in the flow chamber, two side surfaces of the flow chamber are respectively provided with a water inlet and a water outlet, and the water inlet, a pore channel of the porous plastic scintillator and the water outlet are sequentially communicated to form a sampling channel for nuclear power liquid effluent to flow through; and the detection device is connected with the porous plastic scintillator and is used for detecting beta rays released by H-3. The porous plastic scintillator is matched with the flow chamber and the detection device to detect beta radioactivity released when H-3 in the nuclear power liquid effluent decays, the advanced level of liquid effluent monitoring equipment of nuclear facilities such as a nuclear power plant can be remarkably improved, quasi-real-time online monitoring of H-3 in the liquid effluent is achieved, and the detection efficiency is improved. The porous plastic scintillator can be efficiently utilized.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear power radiation monitoring, and particularly to an H-3 online monitoring system and an H-3 online monitoring method. Background Art

[0002] Nuclear facilities such as nuclear power plants will release liquid effluents into the environment. To ensure environmental safety and public health, it is necessary to conduct radioactive monitoring on the discharged liquid effluents. H-3 (tritium) is one of the main radioactive nuclides released by nuclear power plants into the environment. In the liquid effluents discharged by nuclear power plants, the typical maximum concentration of H-3 emissions is on the order of 1×10 7 Bq / L. At present, nuclear power plant operators generally conduct monitoring of H-3 in liquid effluents by using the liquid scintillation counting method after sampling. This method is time-consuming and cannot achieve online monitoring. Moreover, the liquid scintillation counting method uses a toxic scintillation fluid for monitoring, and its main components include toluene, TP (terphenyl), PBD (5-4’(biphenyl)-2-phenyl-1,3,4-oxazole), PPO (2,5-diphenyloxazole), POPOP (1,4-bis-[2’-(5’-phenyl oxazole)]-benzene), etc. After the sample to be measured is mixed with the scintillation fluid for measurement, it will be managed as hazardous waste. The scintillation fluid belongs to the HW waste category in the "National List of Hazardous Wastes (2021 Edition)", and has strong toxicity, flammability and reactivity. Therefore, the existing methods have deficiencies such as being time-consuming, only capable of manual operation, and environmentally unfriendly.

[0003] In view of the need for online monitoring of H-3 in liquid effluents of nuclear facilities such as nuclear power plants, and considering the deficiencies of the liquid scintillation counting method at the same time, it is of great practical significance to develop a method / device for H-3 online monitoring to solve the above problems. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an H-3 online monitoring system and method based on a porous plastic scintillator and an H-3 online monitoring method.

[0005] The technical solution adopted by the present invention to solve its technical problems is: to provide an H-3 online monitoring system, including a flow chamber, a porous plastic scintillator and a detection device;

[0006] The porous plastic scintillator is arranged in the flow chamber. The two sides of the flow chamber are respectively provided with a water inlet and a water outlet. The water inlet, the pore channels of the porous plastic scintillator and the water outlet are sequentially connected to form a sampling channel for the nuclear power liquid effluent to flow through;

[0007] The detection device is connected to the porous plastic scintillator and is used for detecting the β rays released by H-3.

[0008] In one embodiment, the porous plastic scintillator includes a scintillator body and a plurality of channels that are spaced apart and penetrate the opposite first and second surfaces of the scintillator body; the first surface of the scintillator body faces the side where the water inlet is located, and the second surface of the scintillator body faces the side where the water outlet is located.

[0009] In one embodiment, the porous plastic scintillator further includes a reflective layer disposed on the first surface, the second surface, and the exposed portion of the side surface of the scintillator body.

[0010] In one embodiment, the porous plastic scintillator further includes a light-shielding layer covering the reflective layer.

[0011] In one embodiment, the raw materials of the porous plastic scintillator include polystyrene, a scintillating substance, and a wavelength shifter; the scintillating substance includes at least one of 2,5-diphenyloxazole, p-terphenyl, 2-(4'-tert-butylphenyl)-5-(4'-biphenylyl)-1,3,4-oxadiazole, 2-(4-biphenylyl)-5-phenyloxadiazole, and 2-(4-biphenylyl)-5-(4-methylphenyl)-1,3,4-oxadiazole; the wavelength shifter includes at least one of 1,4-bis(5-phenyl-2-oxazolyl)benzene, 1,4-bis(2-methylstyryl)benzene, 1,4-bis(4-methylstyryl)benzene, and 9,10-diphenylanthracene.

[0012] In one embodiment, the detection device includes a photomultiplier tube attached to at least one side surface of the porous plastic scintillator, a preamplifier connected to the photomultiplier tube, a coincidence counter connected to the preamplifier, and a multi-channel analyzer connected to the coincidence counter.

[0013] In one embodiment, the flow chamber includes a housing and a shielding structure layer disposed inside the housing; the shielding structure layer surrounds the outside of the porous plastic scintillator and the photomultiplier tube.

[0014] The shielding structure layer includes a tin shielding layer, a copper shielding layer, and a lead shielding layer that are sequentially covered from the inside to the outside.

[0015] In one embodiment, the flow chamber further includes a lining covering the inner surface of the shielding structure layer.

[0016] In one embodiment, the H-3 on-line monitoring system further includes a data processing and control device for calculating the activity concentration of H-3 based on the radioactive signals detected by the detection device.

[0017] The present invention also provides an H-3 on-line monitoring method using the above H-3 on-line monitoring system. The H-3 on-line monitoring method includes the following steps:

[0018] The nuclear power liquid effluent enters the flow chamber through the water inlet on the flow chamber and discharges from the water outlet on the flow chamber after passing through the porous plastic scintillator;

[0019] When the nuclear power liquid effluent contains H-3, the β particles released by the decay of H-3 excite the scintillating substance of the porous plastic scintillator to produce fluorescence, which is collected and processed by the detection device.

[0020] The beneficial effects of the present invention: The detector uses a porous plastic scintillator, in combination with a flow chamber and a detection device, to detect the β radioactivity released during the decay of H-3 in nuclear power liquid effluents, which can significantly improve the advanced level of liquid effluent monitoring equipment in nuclear power plants and other nuclear facilities, realize quasi-real-time online monitoring of H-3 in liquid effluents, and has high efficiency; at the same time, the porous plastic scintillator can be used efficiently, avoiding the use of toxic liquid scintillators and the generation of hazardous waste in the conventional liquid scintillation counting method. Description of the Drawings

[0021] The present invention will be further described below in conjunction with the drawings and embodiments. In the drawings:

[0022] Figure 1 is a schematic connection structure diagram of the H-3 online monitoring system according to an embodiment of the present invention;

[0023] Figure 2 is a schematic internal structure diagram of the flow chamber in the H-3 online monitoring system according to an embodiment of the present invention;

[0024] Figure 3 is a schematic structure diagram of the porous plastic scintillator in the H-3 online monitoring system according to an embodiment of the present invention. Detailed Embodiments

[0025] For a clearer understanding of the technical features, objectives, and effects of the present invention, the specific embodiments of the present invention will now be described in detail with reference to the drawings.

[0026] As Figures 1 to 3 shown, the H-3 online monitoring system according to an embodiment of the present invention includes a flow chamber 1, a porous plastic scintillator 2, and a detection device.

[0027] The flow chamber 1 has an internal chamber for accommodating the porous plastic scintillator 2 and for the nuclear power liquid effluent to flow through, and combines with the porous plastic scintillator 2 and the detection device to realize the monitoring of H-3 in the nuclear power liquid effluent.

[0028] Among them, a water inlet 11 and a water outlet 12 are respectively provided on two sides of the flow chamber 1. The water inlet 11 and the water outlet 12 respectively penetrate through the side wall of the flow chamber 1 and are communicated with the internal chamber of the flow chamber 1. The water inlet 11 and the water outlet 12 can preferably be arranged on two opposite sides of the flow chamber 1, and the water inlet 11 is preferably located at the lower end of the corresponding side, and the water outlet 12 is preferably located at the upper end of the corresponding side, so that the nuclear power liquid effluent flows in from the bottom and out from the top.

[0029] The porous plastic scintillator 2 is arranged in the flow chamber 1. The porous plastic scintillator 2 has a plurality of pores 20. The water inlet 11, the pores 20 of the porous plastic scintillator 2 and the water outlet 12 are sequentially communicated to form a sampling channel for the nuclear power liquid effluent to flow through. The detection device is connected to the porous plastic scintillator 2 and is used for detecting the β rays released by H-3. When the nuclear power liquid effluent contains H-3, when the nuclear power liquid effluent passes through the sampling channel, the β particles released by the decay of H-3 excite the scintillating substance of the porous plastic scintillator 2 to generate fluorescence, which is collected and processed by the detection device.

[0030] In one embodiment, the porous plastic scintillator 2 is a polyhedron structure, and its pores 20 penetrate through two surfaces of the porous plastic scintillator 2. The pores 20 are preferably straight pores.

[0031] In the flow chamber 1, the inlet end of the pore 20 is opposite to and communicated with the side where the water inlet 11 is located (an inner surface of the flow chamber 1), and the outlet end of the pore 20 is opposite to and communicated with the side where the water outlet 12 is located (an inner surface of the flow chamber 1). The nuclear power liquid effluent enters the flow chamber 1 from the water inlet 11, then enters the pore 20 from the inlet end of the pore 20, and then enters the water outlet 12 through the outlet end of the pore 20 and is discharged from the water outlet 12 out of the flow chamber 1. Since the pores 20 are arranged at intervals, there are gaps between the two surfaces of the porous plastic scintillator 2 penetrated by the pores 20 and the inner surface of the flow chamber on the side where the water inlet 11 is located and the inner surface of the flow chamber on the side where the water outlet 12 is located. The existence of the gaps helps the liquid entering the flow chamber 1 through the water inlet 11 to fill the entire gap, ensuring that it can be diverted into all the pores 20 and then discharged from the pores 20 and the water outlet 12.

[0032] At least one of the water inlet 11 and the water outlet 12 of the flow chamber 1 is further provided with a driving pump 13 for providing power to drive the liquid to enter and exit the flow chamber 1. In Figure 1 the illustrated embodiment, the driving pump 13 is arranged at the water outlet 12. Preferably, the driving pump 13 is a peristaltic pump.

[0033] Further, an inlet valve 14 is also provided at the water inlet 11 for controlling the on-off of the water inlet 11. An outlet valve 15 is also provided at the water outlet 12 for controlling the on-off of the water outlet 12. The inlet valve 14 and the outlet valve 15 are preferably solenoid valves, which are convenient for remote control. A mass flowmeter 16 is also provided at the water outlet 12 for monitoring the liquid flow rate through the flow chamber 1 and the porous plastic scintillator 2.

[0034] In one embodiment, the flow chamber 1 may include a housing 10 and a shielding structure layer disposed inside the housing 10; the shielding structure layer surrounds the outside of the porous plastic scintillator 2, and the internal chamber of the flow chamber 1 is inside the shielding structure layer. The housing 10 can be made of stainless steel and is a closed housing structure. The shielding structure layer as a whole is also in a housing structure, which is attached to the inner surface of the housing 10 and also serves as the outer surrounding structure of the porous plastic scintillator 2. The water inlet 11 and the water outlet 12 respectively penetrate through the housing 10 and the shielding structure layer to communicate with the internal chamber inside the shielding structure layer.

[0035] The shielding structure layer further includes a tin shielding layer 101, a copper shielding layer 102 and a lead shielding layer 103 sequentially covered from the inside to the outside to fully shield low-energy X-rays and reduce the background of the porous plastic scintillator 2 for β detection.

[0036] To avoid the problem of metal corrosion caused by the contact between the nuclear power liquid effluent and the inner surface of the shielding structure layer, the flow chamber 1 may further include a lining 104 covered on the inner surface of the shielding structure layer. The lining 104 is preferably made of polytetrafluoroethylene material.

[0037] The porous plastic scintillator 2 is accommodated in the flow chamber 1, and specifically may include a scintillator main body 21 and a plurality of pores 20 that are spaced apart and penetrate through the scintillator main body 21. In one embodiment, the scintillator main body 21 includes opposite first and second surfaces and a plurality of side surfaces connected between the first and second surfaces. The pores 20 penetrate through the opposite first and second surfaces of the scintillator main body 21. The first surface of the scintillator main body 21 faces the side where the water inlet 11 is located (an inner surface of the flow chamber 1), and the second surface of the scintillator main body 21 faces the side where the water outlet 12 is located (an inner surface of the flow chamber 1).

[0038] In one embodiment, the raw materials of the porous plastic scintillator 2 include polystyrene, a scintillating substance, and a wavelength shifter. Among them, the scintillating substance includes at least one of 2,5-diphenyloxazole (PPO), p-terphenyl (p-TP), 2-(4'-tert-butylphenyl)-5-(4'-biphenyl)-1,3,4-oxadiazole (b-PBD), 2-(4-biphenyl)-5-phenyloxadiazole (PBD), 2-(4-biphenyl)-5-(4-methylphenyl)-1,3,4-oxadiazole (mPBD); the wavelength shifter includes at least one of 1,4-bis(5-phenyl-2-oxazolyl)benzene (POPOP), 1,4-bis(2-methylstyryl)benzene (Bis-MSB), 1,4-bis(4-methylstyryl)benzene (Me-MSB), 9,10-diphenylanthracene (DPA).

[0039] The porous plastic scintillator 2 is preferably obtained by printing using a fused deposition modeling technique, meeting the structural requirements of having multiple faces and channels.

[0040] Taking polystyrene as the scintillator matrix, considering the poor fluidity of pure polystyrene and the problems such as breakage prone to occur during the 3D printing process, the raw materials of the porous plastic scintillator 2 further include a plasticizer. By adding the plasticizer into the scintillator matrix, the melt viscosity of polystyrene is reduced, and the interlayer bonding force of polystyrene during 3D printing is improved. The plasticizer includes at least one of biphenyl, dioctyl phthalate (DOP), and ethylbenzene.

[0041] Preferably, to reduce the dissipation of fluorescent photons, a reflective layer is provided on the outer surface of the scintillator body 21, and the reflective layer is covered on the first surface, the second surface, and the side surfaces of the scintillator body 21. Further, a light-shielding layer 22 is also covered on the reflective layer. The light-shielding layer 22 may include, but is not limited to, a black glue layer or an ink layer. The scintillator body 21, the reflective layer, and the light-shielding layer 22 are provided with PMT (photomultiplier tube) interfaces.

[0042] In one embodiment, the detection device specifically includes a photomultiplier tube 31, a preamplifier 32, a coincidence counter 33, and a multi-channel analyzer 34 connected in sequence. There is at least one photomultiplier tube 31, preferably at least two. The photomultiplier tube 31 is attached to the porous plastic scintillator 2, specifically on the side surface of the scintillator body 21. When there are two photomultiplier tubes 31, they are preferably attached to two opposite side surfaces of the scintillator body 21. Further preferably, photomultiplier tubes 31 are attached to all side surfaces of the scintillator body 21.

[0043] In Figure 2 and Figure 3In the illustrated embodiment, the porous plastic scintillator 2 is generally a square body (cube or cuboid) with six surfaces. The pores 20 of the porous plastic scintillator 2 penetrate through two of the surfaces, and the remaining four surfaces serve as side surfaces, with a photomultiplier tube 31 attached to each side surface.

[0044] The photomultiplier tube 31 is directly attached to the exposed side surface of the scintillator body 21 (without a reflective layer and a light-shielding layer 22). The shielding structure layer and the inner lining 104 in the flow chamber 1 respectively have holes reserved for the photomultiplier tube 31 to be embedded.

[0045] To optimize the weight of the shielding structure layer and reduce the overall volume of the flow chamber 1, the photomultiplier tube 31 preferably has a surface array PMT with a cubic structure.

[0046] The photomultiplier tube 31 is used to acquire optical signals, and each photomultiplier tube 31 is connected to a preamplifier 32. Among them, the β particles released by the H-3 decay excite the scintillating material of the porous plastic scintillator 2 to generate fluorescence. The fluorescence enters the photomultiplier tubes 31 around the flow chamber 1 through light conduction. After the generated optical signals are amplified by the photomultiplier tubes 31, they then enter their respective preamplifiers 32 for amplification and then enter the coincidence counter 33. Coincidence counting is performed through the coincidence counter 33 to obtain the coincidence energy spectrum of the detection signals of the 4 photomultiplier tubes 31, and then it enters the multi-channel spectrometer 34. The purpose of using multiple (such as four) photomultiplier tubes 31 is to significantly reduce the random noise of the PMT through various coincidences, effectively reduce the background, and improve the detection sensitivity.

[0047] In one embodiment, the H-3 online monitoring system further includes a data processing and control device 30. The data processing and control device 30 is connected to the multi-channel spectrometer 34 and is used to calculate and obtain the activity concentration of H-3 based on the radioactive signals detected by the detection device.

[0048] The data processing and control device 30 is also connected to the inlet valve 14, the outlet valve 15, the drive pump 13, and the mass flow meter 16 to achieve remote monitoring.

[0049] The H-3 online monitoring method implemented by the H-3 online monitoring system according to an embodiment of the present invention may include the following steps:

[0050] The nuclear power liquid effluent enters the flow chamber 1 through the water inlet 11 on the flow chamber 1, passes through the porous plastic scintillator 2, and then is discharged from the water outlet 12 on the flow chamber 1.

[0051] When the nuclear power liquid effluent contains H-3, the β particles released by the H-3 decay excite the scintillating material of the porous plastic scintillator 2 to generate fluorescence, which is collected and processed by the detection device.

[0052] The data processing and control device 30 calculates the activity concentration of H-3 based on the radioactive signals collected, processed, and sent by the detection device; the processed monitoring data can be further transmitted to the lower computer or other monitoring systems in real time.

[0053] Specifically, in one round of monitoring, the mass flowmeter 16 is set by the data processing and control device 30, and the inlet valve 14 and the outlet valve 15 are opened. The nuclear power liquid effluent enters the flow chamber 1 from the water inlet 11, enters the pore channels 20 of the porous plastic scintillator 2, and then is output from the water outlet 12. The inlet valve 14 and the outlet valve 15 are closed in sequence. The photomultiplier tube 31 is boosted in voltage to obtain data signals and start counting. The coincidence counting rate is obtained within the set time. The concentration of H-3 is automatically calculated by the multi-channel spectrometer 34 and the data processing and control device 30. The nuclear power liquid effluent sample continues to flow, and the next round of monitoring is restarted at the set interval time.

[0054] The present invention is applicable to continuous or intermittent measurement of liquid flow.

[0055] Taking the effective volume of the internal chamber of the flow chamber 1 as 125 mL as an example: A 2-mm gap is reserved between the side where the water inlet 11 of the flow chamber 1 is located and the side where the water outlet 12 is located and the inlet end and the outlet end of the pore channels 20 on the porous plastic scintillator 2 respectively. According to the above design, the free volume of the liquid in the flow chamber 1 with the porous plastic scintillator 2 in the present invention is about 34.5 mL.

[0056] Example 1: Intermittent measurement method for calculating the concentration of H-3

[0057] Within the set measurement time t (s), the net coincidence counting rate obtained is n e (cps), and the detection efficiency of the system for H-3 is ε (dimensionless). Then, the measurement of the H-3 concentration is calculated by the following formula (I):

[0058]

[0059] In formula (I), A is the activity concentration of H-3 in the sample to be measured, with the unit of Bq / L; V is the volume of the sample to be measured, and the preferred design value can be 0.0345 L (34.5 mL).

[0060] n e is calculated by the following formula (II):

[0061] n e = n n - n b (II)

[0062] In formula (II), n n is the total counting rate within the sample measurement period t, with the unit of cps; n bis the background counting rate of tritium-free water, which is the same as the sample measurement time t (s), and the unit is cps.

[0063] The detection limit for H-3 using the present invention is calculated by the following formula (III):

[0064]

[0065] In formula (III), MDC is the detection limit of the present invention, and the unit is Bq / L.

[0066] Example 2: Continuous measurement of H-3 concentration calculation method

[0067] The net coincidence counting rate at time t is n e (t) (cps), and the detection efficiency of the system for H-3 is ε (dimensionless). Then, the change of the activity concentration of H-3 in the liquid effluent to be measured with time can be calculated by the following formula (IV):

[0068]

[0069] In formula (IV), A(t) is the activity concentration of H-3 in the sample to be measured at time t, and the unit is Bq / L; V is the volume of the sample to be measured, and the preferred design value can be 0.0345 L (34.5 ml).

[0070] n e (t) is calculated by the following formula (V):

[0071] n e (t) = n n (t) - n b (V)

[0072] In formula (V), n e (t) is the total counting rate of the sample measurement at time t, and the unit is cps; n b is the background counting rate of tritium-free water for the background measurement time tb, cps.

[0073] Assuming that one monitoring data is obtained per minute, the detection limit for the quasi-real-time online monitoring of H-3 using the present invention is calculated by the following formula (VI):

[0074]

[0075] In formula (VI), MDC(t) is the detection limit for the quasi-real-time online monitoring of H-3 under the condition of measuring per minute, and the unit is Bq / L.

[0076] If t b >>t, for example, the background measurement time is 10 h (36000 s), and the online measurement time is 1 min (60 s), then MDC(t) can be simplified to the following formula (VII):

[0077]

[0078] In summary, in the present invention, the working principle of the solid scintillation material (porous plastic scintillator) is similar to that of the liquid scintillator. Utilizing the scintillation effect of the solid scintillation material, when the β-rays released during the decay of H-3 react with the fluorescent substance in its solid scintillator, the scintillator absorbs the ray energy and becomes excited. When it transitions to the ground state, it emits fluorescent photons, which are received by the PMT and converted into photoelectrons. After being multiplied by the PMT, they are collected by the anode of the PMT and output in the form of pulses. Through signal processing, the activity concentration of H-3 in the sample is analyzed. The solid scintillation material (porous plastic scintillator) solves the problems of the liquid scintillator, such as strong toxicity, flammability, and environmental unfriendliness.

[0079] The above are only the embodiments of the present invention, and thus do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall similarly be included within the patent protection scope of the present invention.

Claims

1. An H-3 online monitoring system, characterized in that: It includes a flow chamber, a porous plastic scintillator, and a detection device; The porous plastic scintillator is arranged in the flow chamber, and a water inlet and a water outlet are respectively arranged on two sides of the flow chamber, and the water inlet, the pores of the porous plastic scintillator and the water outlet are sequentially connected to form a sampling channel for the flow of nuclear power liquid effluent; The detection device is connected to the porous plastic scintillator and is used for detecting the beta rays released by H-3.

2. The H-3 online monitoring system according to claim 1, characterized in that: The porous plastic scintillator includes a scintillator body, a plurality of holes which are spaced apart and penetrate the first surface and the second surface opposite to each other of the scintillator body; the first surface of the scintillator body is opposite to the side where the water inlet is located, and the second surface of the scintillator body is opposite to the side where the water outlet is located.

3. The H-3 online monitoring system according to claim 2 is characterized in that: The porous plastic scintillator further includes a reflective layer disposed on the first surface, the second surface and the exposed side surface of the scintillator body.

4. The H-3 online monitoring system according to claim 3, characterized in that: The porous plastic scintillator further includes a light shielding layer covered on the reflective layer.

5. The H-3 online monitoring system according to claim 1, characterized in that: The raw materials of the porous plastic scintillator include polystyrene, scintillating material and wave shifting agent; The scintillating material includes at least one of 2,5-diphenyloxazole, p-terphenyl, 2-(4'-tert-butylphenyl)-5-(4'-biphenylyl)-1,3,4-oxadiazole, 2-(4-biphenylyl)-5-phenyloxadiazole, and 2-(4-biphenylyl)-5-(4-tolyl)-1,3,4-oxadiazole; The wave shifter includes at least one of 1,4-bis(5-phenyl-2-oxazolyl)benzene, 1,4-bis(2-methylphenylvinyl)benzene, 1,4-di(4-methylphenylvinyl)benzene and 9,10-diphenylanthracene.

6. The H-3 online monitoring system according to any one of claims 1 to 5, characterized in that: The detection device comprises a photomultiplier tube attached to at least one side of the porous plastic scintillator, a preamplifier connected to the photomultiplier tube, a coincidence counter connected to the preamplifier, and a multi-channel spectrometer connected to the coincidence counter.

7. The H-3 online monitoring system according to claim 6, characterized in that: The flow chamber comprises a shell and a shielding structure layer arranged in the shell; the shielding structure layer surrounds the outer sides of the porous plastic scintillator and the photomultiplier tube; The shielding structure layer comprises a tin shielding layer, a copper shielding layer and a lead shielding layer which are sequentially covered from the inside to the outside.

8. The H-3 online monitoring system according to claim 7, characterized in that: The flow chamber further includes an inner liner covering the inner surface of the shielding structure layer.

9. The H-3 online monitoring system according to any one of claims 1 to 5, characterized in that: The H-3 online monitoring system also includes a data processing and control device for calculating the activity concentration of H-3 based on the radioactive signal detected by the detection device.

10. An H-3 online monitoring method, characterized in that: Using the H-3 online monitoring system according to any one of claims 1 to 9, the H-3 online monitoring method comprises the following steps: The nuclear power liquid effluent enters the flow chamber through the water inlet on the flow chamber, passes through the porous plastic scintillator and is discharged from the water outlet on the flow chamber; When the nuclear power liquid effluent contains H-3, the β particles released by the decay of H-3 excite the scintillation material of the porous plastic scintillator to produce fluorescence, which is collected and processed by the detection device.

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