A water-shielded radionuclide monitoring system and method

Abstract

This invention discloses a water-shielded radionuclide monitoring system and method, applicable to the field of marine radioactivity monitoring technology. It includes a shielding unit, a lifting unit, and a detector unit. The shielding unit is fixed to the ground (deck), and the detector unit is mounted on the lifting unit, which is used to submerge or remove the detector unit from the shielding unit. This invention utilizes water as the shielding material in a liquid, immersion-friendly manner, eliminating the need for cavities or nitrogen filling, thus reducing the background gamma radiation impact of radon and its decay products. The device is detachable for easy transport and on-site assembly on board. The detector can be easily inserted into and removed from the shielding system, enabling applications in various monitoring scenarios.

Description

Technical Field

[0001] This invention relates to the field of marine radioactivity monitoring technology, and more specifically to a water-shielded radionuclide monitoring system and method. Background Technology

[0002] In marine radioactive emergency monitoring, it is necessary to use monitoring equipment to detect the activity concentration of radionuclides on-site. The ambient radiation background has a significant impact on the sensitivity of radionuclide measurements. The radiation background on ships mainly comes from radiation from ship decoration materials, atmospheric radiation, marine radiation, cosmic rays, etc., among which radon daughter products (bismuth-214, lead-214, etc.) and potassium-40 have the most significant impact.

[0003] Analysis of the background gamma spectrum measured onboard the research vessel revealed several short-lived naturally occurring radionuclides from thorium and uranium decay series, such as lead-212 (t1 / 2 = 10.64 h), lead-214 (t1 / 2 = 26.8 min), bismuth-212 (t1 / 2 = 60.6 min), bismuth-214 (t1 / 2 = 19.7 min), actinium-228 (t1 / 2 = 6.13 h), and potassium-40 (t1 / 2 = 1.277 × 10⁹ y). Protactinium-234m (t1 / 2 = 1.17 min) decays from thorium-234 (t1 / 2 = 24.2 d), which is a direct daughter of uranium-238. The radionuclides contained in the ship's interior materials significantly affected the background radiation onboard, with varying degrees of influence depending on the location within the vessel. The gamma-ray peaks of radon progeny and the background radiation caused by the Compton effect significantly affect gamma-ray detection. The Compton effect causes an increase in the background count rate of the radon-222 progeny, lead-214, bismuth-214, and thallium-208, and the radon-220 progeny, lead-212 and bismuth-212. The bismuth-214 peak at 609.31 keV (emission probability 0.463) interferes with the 604.7 keV (emission probability 0.976) energy spectrum of cesium-134. The bismuth-214 peak at 665.45 keV (emission probability 0.0157) interferes with the 661.65 keV energy peak of the cesium-137 progeny, barium-137m.

[0004] Developing environmental radiation shielding technology for onboard gamma-ray nuclide measurement to reduce the background radiation of shipboard detection equipment is urgently needed for monitoring low-level radionuclides. Currently, emergency monitoring of radionuclides on board either does not use shielding or simply transplants lead-shielded chambers from land-based laboratories. If direct measurement is not performed with shielding, the background radiation on the ship increases, raising the detection limit of the detection method and hindering the detection of extremely low-level radionuclides. Currently, shielding chambers used for onboard radionuclide detection are often simply transplanted from land-based laboratories or by reducing the thickness of the lead shielding layer. The main problems are: bulky equipment, the need for large cavities, the requirement for continuous nitrogen filling, the combination of multiple layers of different materials, and difficulty in integrating with other monitoring methods. Therefore, a radionuclide monitoring system is urgently needed to solve the problems existing in current technologies. Summary of the Invention

[0005] In view of this, the present invention provides a water-shielded radionuclide monitoring system and method to meet the needs of on-site monitoring in special environments such as at sea, and to solve the problem of external environmental radiation shielding in on-site radionuclide measurement on ships.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A water-shielded radionuclide monitoring system includes: a shielding unit, a lifting unit, and a detector unit;

[0008] The shielding unit is fixed to the ground, and the detector unit is mounted on the lifting unit. The lifting unit is used to submerge or move the detector unit into or out of the shielding unit.

[0009] The shielding unit includes: a fixing frame, a support net, and a water cavity;

[0010] The fixing frame secures the support net to the ground. The water cavity is located inside the support net and is used to hold water. The water cavity is centered on the detector unit, and the thickness of the water on one side is 20-75cm.

[0011] Preferably, the water cavity is provided with: a water inlet, a water outlet, a vent and overflow hole, a water-absorbing cotton mesh, a perforated partition, and an interface;

[0012] The ventilation and overflow holes and interfaces are located on the upper surface of the water cavity; the water inlet is located at the top of the side wall of the water cavity, and the water outlet is located at the bottom of the side wall of the water cavity; the absorbent cotton mesh is located at the top of the water cavity; the perforated partition is located at the bottom of the water cavity, and multiple perforated partitions are placed crosswise.

[0013] Preferably, the interface includes: a sealing ring, a flexible waterproof sleeve, and a cylindrical partition;

[0014] The upper opening of the cylindrical partition is fixed to the opening of the water cavity by bolts; the upper opening of the flexible waterproof sleeve is fixedly connected to the upper opening of the cylindrical partition; the sealing ring presses against the upper opening of the flexible waterproof sleeve, and the sealing ring and the upper opening of the flexible waterproof sleeve are fixed to the edge of the upper opening of the cylindrical partition by clamps.

[0015] Preferably, the height of the cylindrical baffle is 1 / 3 to 1 / 2 of the height of the water cavity.

[0016] Preferably, the lifting unit includes: a bracket and a lifting platform;

[0017] The bracket is fixedly connected to the support net, and the lifting platform is fixed on the bracket. Both the upper surface and the base of the lifting platform are provided with openings, and the detector unit is installed on the lifting platform through the openings on the upper surface.

[0018] Preferably, the detector unit includes: a detector, a filter, and a sample;

[0019] The lower half of the detector passes through the opening of the lifting platform, and the upper half is mounted on the lifting platform; the sample is mounted on the bottom of the detector; the filter is mounted on the side wall of the lower half of the detector.

[0020] Preferably, the detector is one of the following: sodium iodide detector, lanthanum bromide detector, zinc cadmium telluride detector, electrically cooled high-purity germanium detector, or liquid nitrogen cooled high-purity germanium detector.

[0021] Preferably, the filter is a cylinder, and the upper surface of the filter is provided with a water inlet and a water outlet, and the filter element is provided inside the filter.

[0022] This invention also discloses a method for monitoring radionuclides based on water shielding, comprising the following steps:

[0023] S1. Install the shielding unit on the ground and inject deionized water or tap water into the water cavity;

[0024] S2. Install the lifting unit and the detector unit, and operate the lifting unit to immerse the detector unit into the shielding unit;

[0025] S3. Perform gamma spectrum measurement through the detector unit, and control the lifting unit to move the detector unit out of the shielding unit;

[0026] S4. Install and fix the object to be measured on the detector unit, and operate the lifting unit to immerse the detector unit into the shielding unit for gamma spectrum measurement.

[0027] S5. Use the lifting unit to move the detector unit out of the shielding unit, replace the object to be measured, and perform gamma spectrum measurement again.

[0028] S6. After the measurement is completed, disassemble the lifting unit and the detector unit, and drain the water from the water chamber.

[0029] As can be seen from the above technical solution, compared with the prior art, the present invention discloses a water-shielded radionuclide monitoring system and method, which has the following beneficial effects:

[0030] (1) The liquid fluid with water as the shielding material can be immersed in the method, which does not require a cavity, nitrogen filling, or carrying a nitrogen cylinder, thus reducing the background gamma radiation of radon and its progeny.

[0031] (2) The water filling and emptying of the shielding system is convenient, and the device is detachable for easy movement and transportation; it can flexibly switch application scenarios and can carry out on-site sample testing, mobile monitoring, and environmental background monitoring.

[0032] (3) It can use uncooled detectors (sodium iodide detector, lanthanum bromide detector, zinc zinc cadmium detector, etc.) or electrically cooled high-purity germanium detectors for a long time, and can be used in conjunction with liquid nitrogen cooled high-purity germanium gamma spectrometers.

[0033] (4) The detector can be easily inserted into and removed from the shielding system to realize a variety of monitoring applications. When the detector is inserted into the shield, it can be used for nuclide detection and mobile monitoring of radionuclide enrichment filter elements. The shield can effectively shield the environmental cosmic rays, the background gamma radiation at sea and on the ship itself, and the radiation of radon progeny. When the detector is removed from the shield, it can be flexibly used to monitor the activity concentration of radionuclides in the air, especially for monitoring the activity concentration of radon progeny (bismuth-214; lead-214; lead-212, etc.) in the air at sea. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0035] Figure 1 This is an exploded view of the radionuclide monitoring system of the present invention;

[0036] Figure 2 This is a schematic diagram of the water cavity structure of the present invention;

[0037] Figure 3 This is an exploded view of the interface of the present invention;

[0038] Figure 4 This is a schematic diagram of the filter structure of the present invention;

[0039] Figure 5 This is a flowchart of the radionuclide monitoring method of the present invention;

[0040] In the diagram: 1-fixed frame, 2-support net, 3-water cavity, 4-bracket, 5-lifting platform, 6-detector, 7-filter, 8-sample, 31-inlet, 32-outlet, 33-absorbent cotton net, 34-interface, 35-perforated partition, 36-ventilation overflow hole, 341-sealing ring, 342-flexible waterproof sleeve, 343-cylindrical partition, 71-inlet hole, 72-outlet hole, 73-filter element. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] This invention discloses a water-shielded radionuclide monitoring system, such as... Figure 1 As shown, it includes: a shielding unit, a lifting unit, and a detector unit;

[0043] The shielding unit is fixed on the ground, and the detector unit is mounted on the lifting unit. The lifting unit is used to submerge or move the detector unit into or out of the shielding unit.

[0044] The shielding unit includes: a mounting frame 1, a support mesh 2, and a water cavity 3;

[0045] The fixing frame 1 fixes the support net 2 to the ground. The water cavity 3 is set inside the support net 2. The water cavity 3 is used to hold water. The water cavity 3 is centered on the detector unit, and the thickness of the water on one side is 20-75cm.

[0046] The thickness of the water shield is a key factor determining the shielding effect. The thickness of the water body is determined using the semi-weakening thickness calculation method, similar to that used for gamma point source shielding.

[0047] K=2 n

[0048] R = n × △1 / 2

[0049] In the formula, K is the attenuation factor, n is the number of half-attenuation thicknesses, Δ1 / 2 is the half-attenuation thickness, and Δ1 / 2 is 10.3 cm for γ-rays with an energy of 1.0 MeV;

[0050] Based on calculations using 1.0 MeV radiation, the half-thickness of water is 10.3 cm. When the attenuation factor K is 10, the water shield thickness is 34.2 cm; when the attenuation factor K is 20, the water shield thickness is 44.5 cm; and when K is 100, the water shield thickness is 66.5 cm.

[0051] Furthermore, the detector unit is equipped with a double-layer waterproof membrane or waterproof bag to prevent water leakage when immersed in water; the water cavity 3 can be cylindrical or square, and its material is high-density polyethylene or polypropylene. During measurement, deionized water or tap water is injected into the water cavity. When the water cavity 3 is a cuboid, its length, width and height are 60-150cm, with the most suitable being 80-120cm. When the water cavity 3 is a cylinder, its diameter is 20-150cm and its height is 20-120cm.

[0052] Furthermore, such as Figure 2 As shown, the water cavity 3 is provided with: water inlet 31, water outlet 32, air overflow hole 35, water-absorbing cotton net 33, perforated partition 36, and interface 34.

[0053] Ventilation and overflow holes 35 and interfaces 34 are located on the upper surface of the water cavity 3; inlet 31 is located at the top of the side wall of the water cavity 3, and outlet 32 ​​is located at the bottom of the side wall of the water cavity 3; absorbent cotton mesh 33 is located at the top inside the water cavity 3; perforated baffles 36 are located at the bottom inside the water cavity 3, and multiple perforated baffles 36 are placed crosswise. Valves are provided at the inlet 31 and outlet 32; the detector unit is immersed in water through interface 34; the absorbent cotton mesh 33 and perforated baffles 36 are part of the liquid anti-sloshing design in the shielding unit used on the ship; the absorbent cotton mesh 33 is composed of absorbent cotton and stainless steel mesh; after the detector unit is immersed in the water cavity 3, the overflowing water is discharged through the ventilation and overflow holes 35.

[0054] Furthermore, such as Figure 3 As shown, interface 34 includes: a sealing ring 341, a flexible waterproof sleeve 342, and a cylindrical partition 343;

[0055] The upper opening of the cylindrical partition 343 is fixed to the opening of the water cavity 3 by bolts; the upper opening of the flexible waterproof sleeve 342 is fixedly connected to the upper opening of the cylindrical partition 343; the sealing ring 341 presses against the upper opening of the flexible waterproof sleeve 342, and the upper openings of the sealing ring 341 and the flexible waterproof sleeve 342 are fixed to the edge of the upper opening of the cylindrical partition 343 by clamps. The flexible waterproof sleeve 342 fits tightly against the detector unit in the water, preventing water from the water cavity 3 from entering the detector unit.

[0056] Furthermore, the height of the cylindrical baffle 343 is 1 / 3 to 1 / 2 of the height of the water cavity 3. The cylindrical baffle 343 is designed to prevent swaying and is used to stabilize the water body.

[0057] Furthermore, the lifting unit includes: bracket 4 and lifting platform 5;

[0058] The bracket 4 is fixedly connected to the support net 2, and the lifting platform 5 is fixed on the bracket 4. Both the upper surface and the base of the lifting platform 5 are provided with openings, and the detector unit is installed on the lifting platform 5 through the openings on the upper surface. The lifting platform 5 is an electric lifting platform, and the diameter of the openings is 12-15cm.

[0059] Furthermore, the detector unit includes: detector 6, filter 7, and sample 8;

[0060] The lower half of detector 6 passes through the opening of lifting platform 5, and the upper half is installed on lifting platform 5; sample 8 is installed at the bottom of detector 6, and sample 8 is enriched with radioactive nuclides; filter 7 is installed on the side wall of the lower half of detector 6.

[0061] Furthermore, detector 6 is one of the following: sodium iodide detector, lanthanum bromide detector, zinc cadmium telluride detector, electrically cooled high-purity germanium detector, or liquid nitrogen cooled high-purity germanium detector.

[0062] Furthermore, such as Figure 4 As shown, the filter 7 is a cylinder, with an inlet hole 71 and an outlet hole 72 on the upper surface of the filter 7, and a filter element 73 inside the filter 7.

[0063] and Figure 1 Corresponding to the aforementioned system, this invention also discloses a method for monitoring radionuclides based on water shielding, such as... Figure 5 As shown, it includes the following steps:

[0064] S1. Install the shielding unit on the ground and inject deionized water or tap water into the water cavity;

[0065] S2. Install the lifting unit and the detector unit, and operate the lifting unit to immerse the detector unit into the shielding unit;

[0066] S3. Perform gamma spectrum measurement through the detector unit, and control the lifting unit to move the detector unit out of the shielding unit;

[0067] S4. Install and fix the object to be measured on the detector unit, and operate the lifting unit to immerse the detector unit into the shielding unit for gamma spectrum measurement.

[0068] S5. Use the lifting unit to move the detector unit out of the shielding unit, replace the object to be measured, and perform gamma spectrum measurement again.

[0069] S6. After the measurement is completed, disassemble the lifting unit and the detector unit, and drain the water from the water chamber.

[0070] Specifically, the radionuclide monitoring method disclosed in this embodiment can be used for on-site marine radionuclide sample detection on board, marine radionuclide mobile monitoring, and environmental background monitoring;

[0071] When conducting on-site marine radionuclide sample testing on board, the object to be tested is the sample. The sample is installed on the detector unit and fixed before testing.

[0072] When conducting marine radionuclide mobile monitoring, the object to be tested is a filter element. The filter is installed on the detector unit and fixed. After a period of monitoring and sampling, the filter element in the filter is replaced and monitoring is carried out again.

[0073] Environmental background monitoring can be achieved by moving the detector unit outside the shielding unit.

[0074] In one specific embodiment, the activity concentrations of cesium-137 and cesium-134 in seawater are accurately monitored using the nuclide monitoring system disclosed in this invention, and the cesium-137 / cesium-134 index is obtained as a basis for judging marine radioactive pollution and analyzing diffusion pathways.

[0075] A water-shielded simulation experiment was conducted using the radionuclide monitoring system disclosed in this invention, employing a Canberra high-purity germanium gamma spectrometer (GCW6203) with a detection efficiency of 65%. Nitrogen gas was used to purge air from the lead-shielded chamber, and the background count of the target energy peak was measured after 3 days. The top cover was left open, and the top was covered with paper to prevent dust from entering the shielded chamber. After air freely entered and reached equilibrium, the background count was measured. A simulated water shield (22cm high / 22cm outer diameter / 10cm inner diameter / 6cm wall thickness) was placed inside, the top cover was left open, and the background count was measured again. The results of the three averages are shown in Table 1.

[0076] Table 1

[0077]

[0078] It can be seen that the monitoring system disclosed in this invention has the following shielding effects on radon progeny (calculated using Bi-214 as an example): the count rate at the 609.3 keV energy peak can be reduced by 66.2%, the background count rate at 604.7 keV for Cs-134 can be reduced by 26.2%, and the measured background count rate at 661.7 keV for Cs-137 can be reduced by 25.2%.

[0079] Furthermore, the cesium-137 / cesium-134 ratio was monitored using the radionuclide monitoring system disclosed in this invention. The background count rate on the deck of a marine vessel was approximately 1 / 40th that of a land-based laboratory. By combining the shielding system with a gamma spectrometer, a low detection limit for radionuclide detection was obtained. At this low detection limit, the activity concentrations of cesium-137 and cesium-134 in seawater were accurately monitored, yielding the cesium-137 / cesium-134 ratio, which serves as a basis for assessing marine radioactive contamination. The range of the cesium-137 / cesium-134 ratio in the sea area can also reflect the diffusion pathways of marine radioactive pollutants. The detection results before and after shielding on the marine vessel are shown in Table 2.

[0080] Table 2

[0081]

[0082]

[0083] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0084] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A water-shielded radionuclide monitoring system, characterized in that, include: Shielding unit, lifting unit, detector unit; The shielding unit is fixed to the ground, and the detector unit is mounted on the lifting unit. The lifting unit is used to submerge or move the detector unit into or out of the shielding unit. The shielding unit includes: a fixing frame (1), a support net (2), and a water cavity (3); The fixing frame (1) fixes the support net (2) on the ground. The water cavity (3) is set inside the support net (2). The water cavity (3) is used to hold water. The water cavity (3) is centered on the detector unit. The thickness of the water on one side is 20-75cm. The water cavity (3) is provided with: an inlet (31), an outlet (32), a venting and overflow hole (35), a water-absorbing cotton net (33), a perforated partition (36), and an interface (34); The ventilation overflow hole (35) and interface (34) are provided on the upper surface of the water cavity (3); the water inlet (31) is provided on the top of the side wall of the water cavity (3), and the water outlet (32) is provided on the bottom of the side wall of the water cavity (3); the absorbent cotton net (33) is provided on the top of the inside of the water cavity (3); the perforated partition (36) is provided on the bottom of the inside of the water cavity (3), and multiple perforated partitions (36) are placed crosswise; The interface (34) includes: a sealing ring (341), a flexible waterproof sleeve (342), and a cylindrical partition (343); The upper opening of the cylindrical partition (343) is fixed to the opening of the water cavity (3) by bolts; the upper opening of the flexible waterproof sleeve (342) is fixedly connected to the upper opening of the cylindrical partition (343); the sealing ring (341) presses against the upper opening of the flexible waterproof sleeve (342), and the upper openings of the sealing ring (341) and the flexible waterproof sleeve (342) are fixed to the edge of the upper opening of the cylindrical partition (343) by clamps.

2. The water-shielded radionuclide monitoring system according to claim 1, characterized in that, The height of the cylindrical partition (343) is 1 / 3 to 1 / 2 of the height of the water cavity (3).

3. The water-shielded radionuclide monitoring system according to claim 1, characterized in that, The lifting unit includes: a bracket (4) and a lifting platform (5); The bracket (4) is fixedly connected to the support net (2), and the lifting platform (5) is fixed on the bracket (4). The upper surface and the base of the lifting platform (5) are provided with openings, and the detector unit is installed on the lifting platform (5) through the openings on the upper surface.

4. A water-shielded radionuclide monitoring system according to claim 3, characterized in that, The detector unit includes: a detector (6), a filter (7), and a sample (8); The lower half of the detector (6) passes through the opening of the lifting platform (5), and the upper half is mounted on the lifting platform (5); the sample (8) is mounted on the bottom of the detector (6); the filter (7) is mounted on the side wall of the lower half of the detector (6).

5. A water-shielded radionuclide monitoring system according to claim 4, characterized in that, The detector (6) is one of the following: sodium iodide detector, lanthanum bromide detector, zinc cadmium telluride detector, electrically cooled high-purity germanium detector, and liquid nitrogen cooled high-purity germanium detector.

6. A water-shielded radionuclide monitoring system according to claim 4, characterized in that, The filter (7) is a cylinder, and the upper surface of the filter (7) is provided with a water inlet hole (71) and a water outlet hole (72). The filter (7) is provided with a filter element (73) inside.

7. A method for monitoring radionuclides based on water shielding, using the water-shielded radionuclide monitoring system according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Install the shielding unit on the ground and inject deionized water or tap water into the water cavity; S2. Install the lifting unit and the detector unit, and operate the lifting unit to immerse the detector unit into the shielding unit; S3. Perform gamma spectrum measurement through the detector unit, and control the lifting unit to move the detector unit out of the shielding unit; S4. Install and fix the object to be measured on the detector unit, and operate the lifting unit to immerse the detector unit into the shielding unit for gamma spectrum measurement. S5. Use the lifting unit to move the detector unit out of the shielding unit, replace the object to be measured, and perform gamma spectrum measurement again. S6. After the measurement is completed, disassemble the lifting unit and the detector unit, and drain the water from the water chamber.

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