An electric auxiliary heating device for producing I-131

Abstract

The present invention discloses an electric assisted heating type device for producing I-131, including a tubular furnace, a distillation absorber, a purifier, a circulating water cooling tank, a peristaltic pump, a liquid storage bottle, a bracket and a stand. The tubular furnace is horizontally arranged on the table top of the stand, the purifier, the circulating water cooling tank, and the liquid storage bottle are arranged on the bottom plate of the stand, the peristaltic pump is arranged on one side of the stand, the bracket is fixedly arranged under the table top, a part of the distillation absorber is arranged in the tubular furnace, and the other part is arranged under the table top and placed on the bracket, the distillation absorber is connected to the peristaltic pump and the liquid storage bottle in turn through pipelines, and is also connected to the purifier and the circulating water cooling tank through pipelines. The production device of the present invention adopts a compressed air drive instead of a vacuum pump and an electric heating sleeve to heat the carrier gas throughout the whole process, so as to realize the efficient absorption of radioactive iodine-131 in the high-temperature carrier gas, and eliminate the influence of vacuum pump failure on production and the generation of pump-related radioactive waste, which is more conducive to safe production.

Description

Technical Field

[0001] The invention belongs to the technical field of radioactive isotope preparation, and in particular relates to an electric auxiliary heating type device for producing I-131. Background Art

[0002] Sodium iodide used in medical institutions 131 The radioactive raw materials of the drugs labeled with iodine-131 (I-NaI) and iodine-131 mainly come from tellurium dioxide activated by reactor irradiation, and are mainly produced by dry distillation. In addition to the unit providing the present invention, the Institute of Nuclear Physics and Chemistry of the China Academy of Engineering Physics, the Chinese Academy of Atomic Energy and the China Nuclear Power Research Institute have both been engaged in the dry distillation production of iodine-131 and established production equipment. However, the existing production technology has the problem that the iodine-131 distilled from the target material is easily deposited or retained on the inner wall of the pipeline during the carrier gas carrier transport process, especially in the exposed pipelines connected to the absorption bottle and at low temperatures, resulting in low product yields, long production time and other problems, which is not conducive to improving production efficiency. In addition, the vacuum pumps used in production need to be regularly maintained or replaced, which inevitably increases the radiation dose of the staff and the generation of radioactive waste related to the replacement of waste vacuum pumps or their maintenance. At present, there is no public report on an efficient I-131 production device that has the ability to heat and insulate the entire process of the carrier gas carrier transport process of the distilled iodine-131-containing carrier gas and uses compressed air to drive the carrier gas transport. Summary of the invention

[0003] In order to overcome the shortcomings of the prior art that iodine-131 distilled from the target material is easily deposited or retained on the inner wall of the pipeline during the carrier gas transport process, resulting in low product yield, long production time and increased radiation risk for workers, and to achieve the purpose of further improving production efficiency, the present invention provides an electric auxiliary heating type I-131 production device, which can efficiently absorb radioactive iodine-131 in the carrier gas and completely eliminate the impact of vacuum pump failure on production, the radiation dose received by workers during regular maintenance or replacement of vacuum pumps, and the generation of radioactive waste related to the replacement of used vacuum pumps or their maintenance.

[0004] The technical solution for implementing the present invention is as follows:

[0005] The invention discloses an electric-assisted heating device for producing I-131, which is characterized in that the electric-assisted heating device for producing I-131 comprises a tube furnace, a distillation absorber, a purifier, a circulating water cooling tank, a peristaltic pump liquid storage bottle, a bracket and a stand, and the connection relationship is that the tube furnace is horizontally arranged on the table top of the stand, the purifier, the circulating water cooling tank, and the liquid storage bottle are arranged on the bottom plate of the stand, the peristaltic pump is arranged on one side of the stand, the bracket is fixedly arranged under the table top, a part of the distillation absorber is arranged in the tube furnace, and the other part is arranged under the table top and placed on the bracket, the distillation absorber is connected to the peristaltic pump and the liquid storage bottle in sequence through pipelines, and is also connected to the purifier and the circulating water cooling tank through pipelines respectively;

[0006] The distillation absorber comprises a distillation tube and an absorption bottle; the distillation tube is horizontally arranged in the furnace chamber of the tube furnace, a plug is arranged at the open end of the distillation tube, a quartz boat is arranged in the distillation tube, a temperature measuring sleeve I is fixedly arranged at the bottom of the distillation tube, and a thermocouple I is arranged in the temperature measuring sleeve I; the absorption bottle is arranged just below the bottom of the distillation tube, and the top of the absorption bottle penetrates into the distillation tube and is fixedly connected to the distillation tube;

[0007] The absorption bottle comprises a vent pipe, an electric heating sleeve, an insulating sleeve, an alkali solution bottle, a water-cooled cone sleeve, a temperature measuring sleeve II, an exhaust pipe and an inlet and outlet pipe, wherein the lower end of the vent pipe is in a trumpet shape; the vent pipe, the electric heating sleeve, the insulating sleeve and the alkali solution bottle are arranged vertically in sequence from the inside to the outside, the upper end surface of the alkali solution bottle is sealed and fixedly connected to the upper outer side surface of the insulating sleeve, and a gap is arranged between the bottom of the insulating sleeve and the alkali solution bottle; the water-cooled cone sleeve is arranged in the trumpet of the vent pipe and has a small gap with the bottom of the alkali solution bottle, and the water-cooled cone sleeve The water inlet and outlet pipes at the lower end pass downward through the alkali liquid bottle and are connected to the circulating water cooling tank pipeline, and are sealed and fixedly connected to the alkali liquid bottle; the temperature measuring sleeve II vertically passes through the bottom of the alkali liquid bottle and the center of the water cooling cone sleeve in turn and extends into the straight pipe at the lower part of the ventilation pipe, a thermocouple II is arranged in the temperature measuring sleeve II, and the temperature measuring sleeve II is sealed and fixedly connected to the alkali liquid bottle; the exhaust pipe and the inlet and outlet pipes are correspondingly arranged on the upper side of the alkali liquid bottle, the exhaust pipe is connected to the purifier pipeline, and the inlet and outlet pipes are connected to the peristaltic pump through a pipeline provided with a valve I;

[0008] The purifier comprises an iodine removal bottle, a cold trap, an activated carbon column, an air pump and a gas tank which are connected in sequence by pipelines. The air pump is fixedly arranged under the table and connected to the gas tank pipeline. A pressure gauge and a valve II are fixedly arranged on the gas tank. A valve III is arranged on the air inlet pipeline of the iodine removal bottle. The iodine removal bottle is connected to the exhaust pipe pipeline.

[0009] The bracket includes a screw rod, a nut and a loading platform, wherein the loading platform is annular and symmetrically provided with two small round through holes; the screw rod is vertically fixedly installed under the table surface of the rack, the nut is installed in the middle and lower part of the screw rod and is slidably connected with the screw rod, the loading platform is passed through the screw rod through the two small round through holes and placed on the nut, the loading platform is slidably connected with the screw rod, a circular rubber pad is arranged on the loading platform, and the alkali solution bottle is placed on the rubber pad;

[0010] The gas tank is externally connected to an air compressor; the tubular furnace, circulating water cooling tank, peristaltic pump, thermocouple I and thermocouple II are externally connected to a controller.

[0011] Preferably, the valves are all solenoid valves, and are all electrically connected to an external controller.

[0012] Preferably, the longitudinal axis center lines of the ventilation pipe, the electric heating sleeve, the insulation sleeve, and the alkali solution bottle coincide with each other and intersect perpendicularly with the horizontal axis center line of the distillation tube.

[0013] Preferably, the distillation tube, ventilation tube, electric heating sleeve, insulation sleeve, alkali solution bottle, water-cooling cone sleeve, temperature measuring sleeve I, inlet and outlet pipes, exhaust pipe, and plug are all made of quartz glass; the insulation sleeve is filled with asbestos fiber or is vacuumed.

[0014] The invention discloses an electric auxiliary heating type I-131 production device, which uses the negative pressure generated by the rapid injection of compressed air in the vacuum pump to drive the airborne radioactive iodine-131 to be transported from the distillation tube to the absorption bottle, and implements the method of high-temperature gas insulation on the airborne iodine-131 transport pipeline, thereby realizing the efficient absorption of the airborne radioactive iodine-131 distilled from the furnace tube. The brief working principle is: the compressed air is discharged from the vacuum pump to generate a large negative pressure in the pump cavity, and is successively transmitted to the distillation tube through the activated carbon column, the cold trap, the iodine removal bottle, the exhaust pipe, the alkali solution bottle, and the ventilation pipe, so as to drive the radioactive I-131 generated in the distillation tube to be absorbed by the iodine-131 absorption bottle. The carrier gas flows in a directional manner. The I-131 carrier gas flows through the vent pipe heated by the electric heating sleeve until it is continuously heated and kept warm (over 200°C) before it contacts the absorption liquid (generally a dilute sodium hydroxide solution) in the alkali liquid bottle, thereby reducing the deposition or retention of I-131 on the inner wall of the transport pipeline; the high-temperature carrier gas entering the alkali liquid bottle is quickly cooled by the water-cooled cone sleeve placed in the bell mouth of the vent pipe, and the radioactive I-131 gas carried by the air is absorbed by the absorption liquid filled in the alkali liquid bottle. The tail gas treated by the absorption liquid is extracted from the exhaust pipe, and is purified by the iodine removal bottle, cold trap, and activated carbon column in turn, and finally discharged from the vacuum pump, realizing Na 131 I solution is efficiently produced.

[0015] The electric auxiliary heating type I-131 production device of the present invention adopts a vertical structural layout, eliminating the disadvantages of the traditional technology of long connecting pipelines, multiple turns in the pipelines and the inability to achieve full-process insulation of the carrier gas transportation. It completely eliminates the unfavorable factors such as the need for regular maintenance or replacement of the vacuum pumps used in the prior art, the inevitable increase in the radiation dose of the staff, and the generation and disposal of radioactive waste related to the replacement of waste vacuum pumps or their maintenance, thereby greatly improving the production efficiency and having good operational stability and safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The present invention is a schematic diagram of the structure of an electric auxiliary heating device for producing I-131.

[0017] In the figure, 1. distillation tube; 2. tubular furnace; 3. ventilation pipe; 4. electric heating jacket; 5. insulation sleeve; 6. alkali solution bottle; 7. water-cooling cone sleeve; 8. temperature measuring sleeve II; 9. thermocouple II; 10. exhaust pipe; 11. inlet and outlet pipes; 12. temperature measuring sleeve I; 13. thermocouple I; 14. stopper; 15. vacuum pump; 16 circulating water cooling tank; 17. gas tank; 18. peristaltic pump; 19. pressure gauge; 20. liquid storage bottle; 21. valve I; 22. valve II; 23. valve III; 24. iodine removal bottle; 25. cold trap; 26. activated carbon column; 27. quartz boat; 28. table; 29 bottom plate; 30. stage; 31. screw; 32. nut; 33. rubber pad. DETAILED DESCRIPTION

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without any creative labor.

[0019] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific implementation methods and drawings.

[0020] Example 1

[0021] Figure 1 This is a schematic diagram of the structure of an electric auxiliary heating type I-131 production device of the present invention. Figure 1In the present invention, the device for producing I-131 by electric auxiliary heating includes a tube furnace 2, a distillation absorber, a purifier, a circulating water cooling tank 16, a peristaltic pump 18, a liquid storage bottle 20, a bracket and a stand. The tube furnace 2 is horizontally arranged on the table 28 of the stand, the purifier, the circulating water cooling tank 16, and the liquid storage bottle 20 are arranged on the bottom plate 29 of the stand, the peristaltic pump 18 is arranged on one side of the stand, the bracket is fixedly arranged under the table 28, a part of the distillation absorber is arranged in the tube furnace 2, and the other part is arranged under the table 28 and placed on the bracket, the distillation absorber is connected to the peristaltic pump 18 and the liquid storage bottle 20 in sequence through pipelines, and is also connected to the purifier and the circulating water cooling tank 16 by pipelines. The distillation absorber comprises a distillation tube 1 and an absorption bottle; the distillation tube 1 is horizontally arranged in the furnace chamber of the tubular furnace 2, a plug 14 is arranged at the open end of the distillation tube 1, a quartz boat 27 is arranged in the distillation tube 1, a temperature measuring sleeve Ⅰ12 is fixedly arranged at the bottom of the distillation tube 1, and a thermocouple Ⅰ13 is arranged in the temperature measuring sleeve Ⅰ12; the absorption bottle is arranged just below the bottom of the distillation tube 1, and the top of the absorption bottle penetrates into the distillation tube 1 and is fixedly connected to the distillation tube 1. The absorption bottle comprises a vent pipe 3, an electric heating sleeve 4, an insulating sleeve 5, an alkali liquid bottle 6, a water-cooled cone sleeve 7, a temperature measuring sleeve II 8, an exhaust pipe 10 and an inlet and outlet pipe 11, wherein the lower end of the vent pipe 3 is in a trumpet shape; the vent pipe 3, the electric heating sleeve 4, the insulating sleeve 5, and the alkali liquid bottle 6 are arranged vertically in sequence from the inside to the outside, the upper end surface of the alkali liquid bottle 6 is sealed and fixedly connected to the upper outer side surface of the insulating sleeve 5, and a gap is provided between the bottom of the insulating sleeve 5 and the alkali liquid bottle 6; the water-cooled cone sleeve 7 is arranged in the trumpet of the vent pipe 3 and has a small gap with the bottom of the alkali liquid bottle 6, and the lower end of the water-cooled cone sleeve 7 is provided with a small gap. The water inlet and outlet pipes at the ends pass downward through the alkali liquid bottle 6 and are connected to the circulating water cooling tank 16 pipeline, and are sealed and fixedly connected to the alkali liquid bottle 6; the temperature measuring sleeve II 8 vertically passes through the bottom of the alkali liquid bottle 6 and the center of the water-cooling cone sleeve 7 in turn, and extends into the straight pipe at the lower part of the ventilation pipe 3. A thermocouple II 9 is arranged in the temperature measuring sleeve II 8, and the temperature measuring sleeve II 8 is sealed and fixedly connected to the alkali liquid bottle 6; the exhaust pipe 10 and the inlet and outlet pipes 11 are correspondingly arranged on the upper side of the alkali liquid bottle 6, the exhaust pipe 10 is connected to the purifier pipeline, and the inlet and outlet pipes 11 are connected to the peristaltic pump 18 through a pipeline provided with a valve I 21. The purifier comprises an iodine removal bottle 24, a cold trap 25, an activated carbon column 26, an air pump 15 and a gas tank 17 which are connected in sequence by pipelines. The air pump 15 is fixedly arranged under a table 28 and connected to the gas tank 17 by pipeline. A pressure gauge 19 and a valve II 22 are fixedly arranged on the gas tank 17. A valve III 23 is arranged on the air inlet pipeline of the iodine removal bottle 24. The iodine removal bottle 24 is connected to the exhaust pipe 10 by pipeline.The bracket includes a screw 31, a nut 32 and a stage 30, wherein the stage 30 is annular and symmetrically provided with two small round through holes; the screw 31 is vertically fixedly installed under the table 28 of the stage, the nut 32 is installed in the middle and lower part of the screw 31 and is slidably connected with the screw 31, the stage 30 is passed through the screw 31 through the two small round through holes and placed on the nut 32, the stage 30 is slidably connected with the screw 31, a circular rubber pad 33 is arranged on the stage 30, and the alkali liquid bottle 6 is placed on the rubber pad 33; the gas tank 17 is externally connected to the air compressor; the tubular furnace 2, the circulating water cooling tank 16, the peristaltic pump 18, the thermocouple I 13 and the thermocouple II 9 are externally connected to the controller. The valves are all solenoid valves, and are all electrically connected to the external controller. The longitudinal axis of the ventilation pipe 3, electric heating sleeve 4, insulation sleeve 5, and alkali liquid bottle 6 coincides and vertically intersects with the horizontal axis of the distillation pipe 1. The distillation pipe 1, ventilation pipe 3, electric heating sleeve 4, insulation sleeve 5, alkali liquid bottle 6, water cooling cone sleeve 7, temperature measuring sleeve Ⅰ12, inlet and outlet pipes 11, exhaust pipe 10, and plug 14 are all made of quartz glass; the insulation sleeve 5 is filled with asbestos fiber. See. Figure 1 shown.

[0022] The working process of the present invention is as follows: turn on the external controller, start the peristaltic pump 18 in sequence to quantitatively add absorption liquid into the alkali solution bottle 6 through the inlet and outlet pipes 11, start the circulating water cooling tank 16 to inject cold water into the water-cooled cone sleeve 7, start the air compressor to inject compressed air into the gas tank 17 and connect the vacuum pump 15, start the tubular furnace 2 to heat the distillation tube 1, start the electric heating sleeve 4 to heat and keep the ventilation pipe 3 warm, and connect the thermocouple I 13 and the thermocouple II 9 to monitor the carrier gas at the end of the ventilation pipe 3 in the alkali solution bottle 6 and the temperature inside the distillation tube 1, respectively. The compressed air is discharged from the vacuum pump 15 to generate a large negative pressure in the pump cavity, and is successively transferred to the distillation tube 1 through the activated carbon column 26, the cold trap 25, the iodine removal bottle 24, the exhaust pipe 10, the alkali solution bottle 6, and the ventilation pipe 3. The distillation tube 1 is heated to about 750°C and the radioactive I-131 (the carrier gas is air) distilled from the irradiated TeO2 target material in the quartz boat 27 is driven by the negative pressure and flows in a directional manner from the distillation tube 1 through the ventilation pipe 3, the alkali solution bottle 6, the exhaust pipe 10, the iodine removal bottle 24, the cold trap 25, the activated carbon column 26, and is discharged from the vacuum pump 15. The carrier gas containing the radioactive I-131 flows through the ventilation pipe 3 heated by the electric heating sleeve 4 to the absorption gas in the alkali solution bottle 6. The liquid (generally a dilute sodium hydroxide solution) is continuously heated and kept warm (over 200°C) before contacting it, thereby reducing the deposition or retention of I-131 on the inner wall of the transport pipeline; the high-temperature carrier gas entering the alkali liquid bottle 6 is quickly cooled by the water-cooled cone sleeve 7 placed in the bell mouth of the ventilation pipe 3, and the airborne radioactive I-131 gas is absorbed by the absorption liquid filled in the alkali liquid bottle 6. The tail gas treated with the absorption liquid is extracted from the exhaust pipe 10, and is purified in turn by the iodine removal bottle 24, the cold trap 25, and the activated carbon column 26, and finally discharged from the vacuum pump 17; the controller instructs the peristaltic pump 18 to reverse, so that the absorption liquid in the alkali liquid bottle 6 can be transferred to the liquid storage bottle 20, thereby realizing the efficient production of I-131.

[0023] Example 2

[0024] The structure of this embodiment is the same as that of the embodiment 1, except that the interior of the heat insulating sleeve 5 in this embodiment is vacuum.

Claims

1. An electric auxiliary heating type device for producing I-131, characterized by: The electric auxiliary heating type I-131 production device comprises a tube furnace (2), a distillation absorber, a purifier, a circulating water cooling tank (16), a peristaltic pump (18), a liquid storage bottle (20), a bracket and a stand, wherein the connection relationship is that the tube furnace (2) is horizontally arranged on the table top (28) of the stand, the purifier, the circulating water cooling tank (16), and the liquid storage bottle (20) are arranged on the bottom plate (29) of the stand, the peristaltic pump (18) is arranged on one side of the stand, the bracket is fixedly arranged under the table top (28), a part of the distillation absorber is arranged in the tube furnace (2), and the other part is arranged under the table top (28) and placed on the bracket, and the distillation absorber is peristaltic pumped in sequence through a pipeline. The distillation absorber comprises a distillation tube (1) and an absorption bottle; the distillation tube (1) is horizontally arranged in the furnace chamber of the tube furnace (2); a plug (14) is arranged at the open end of the distillation tube (1); a quartz boat (27) is arranged in the distillation tube (1); a temperature measuring sleeve I (12) is fixedly arranged at the bottom of the distillation tube (1); a thermocouple I (13) is arranged in the temperature measuring sleeve I (12); the absorption bottle is arranged just below the bottom of the distillation tube (1); the top of the absorption bottle penetrates into the distillation tube (1) and is fixedly connected to the distillation tube (1); The absorption bottle comprises a vent pipe (3), an electric heating sleeve (4), an insulating sleeve (5), an alkali liquid bottle (6), a water-cooling cone sleeve (7), a temperature measuring sleeve II (8), an exhaust pipe (10) and an inlet and outlet pipe (11), wherein the lower end of the vent pipe (3) is in the shape of a bell mouth; the vent pipe (3), the electric heating sleeve (4), the insulating sleeve (5) and the alkali liquid bottle (6) are arranged vertically in sequence from the inside to the outside, the upper end surface of the alkali liquid bottle (6) is sealed and fixedly connected to the upper outer side surface of the insulating sleeve (5), and a gap is provided between the bottom of the insulating sleeve (5) and the alkali liquid bottle (6); the water-cooling cone sleeve (7) is arranged in the bell mouth of the vent pipe (3) and has a small gap with the bottom of the alkali liquid bottle (6); the water-cooling cone sleeve (7) is arranged in the bell mouth of the vent pipe (3) and has a small gap with the bottom of the alkali liquid bottle (6); the water-cooling cone sleeve (8 ... 7) The water inlet and outlet pipes at the lower end pass downward through the alkali liquid bottle (6) and are connected to the circulating water cooling tank (16) pipeline, and are sealed and fixedly connected to the alkali liquid bottle (6); the temperature measuring sleeve II (8) vertically passes through the bottom of the alkali liquid bottle (6) and the center of the water cooling cone sleeve (7) in turn and extends into the straight pipe at the lower part of the ventilation pipe (3), a thermocouple II (9) is arranged in the temperature measuring sleeve II (8), and the temperature measuring sleeve II (8) is sealed and fixedly connected to the alkali liquid bottle (6); the exhaust pipe (10) and the inlet and outlet pipes (11) are correspondingly arranged on the upper side of the alkali liquid bottle (6), the exhaust pipe (10) is connected to the purifier pipeline, and the inlet and outlet pipes (11) are connected to the peristaltic pump (18) through a pipeline provided with a valve I (21); The purifier comprises an iodine removal bottle (24), a cold trap (25), an activated carbon column (26), an air pump (15) and a gas tank (17) which are connected in sequence by pipelines. The air pump (15) is fixedly arranged under a table (28) and connected to the gas tank (17) by pipeline. A pressure gauge (19) and a valve II (22) are fixedly arranged on the gas tank (17). A valve III (23) is arranged on the air inlet pipeline of the iodine removal bottle (24). The iodine removal bottle (24) is connected to the exhaust pipe (10) by pipeline. The bracket comprises a screw rod (31), a nut (32) and a loading platform (30), wherein the loading platform (30) is annular and symmetrically provided with two small round through holes; the screw rod (31) is vertically fixedly installed under the table surface (28) of the rack, the nut (32) is installed at the middle and lower part of the screw rod (31) and is slidably connected with the screw rod (31), the loading platform (30) is passed through the screw rod (31) through the two small round through holes and is placed on the nut (32), the loading platform (30) is slidably connected with the screw rod (31), a ring-shaped rubber pad (33) is arranged on the loading platform (30), and the alkali solution bottle (6) is placed on the rubber pad (33); The gas tank (17) is externally connected to an air compressor; the tubular furnace (2), circulating water cooling tank (16), peristaltic pump (18), thermocouple I (13) and thermocouple II (9) are externally connected to a controller.

2. The electric auxiliary heating type I-131 production device according to claim 1 is characterized in that: The valves are all solenoid valves, and are all electrically connected to an external controller.

3. The electric auxiliary heating type I-131 production device according to claim 1 is characterized in that: The longitudinal axis center lines of the ventilation pipe (3), the electric heating sleeve (4), the heat-insulating sleeve (5) and the alkali solution bottle (6) coincide with each other and vertically intersect with the horizontal axis center line of the distillation tube (1).

4. The electric auxiliary heating type I-131 production device according to claim 1 is characterized in that: The distillation tube (1), ventilation tube (3), electric heating sleeve (4), heat-insulating sleeve (5), alkali solution bottle (6), water-cooling cone sleeve (7), temperature measuring sleeve I (12), inlet and outlet pipes (11), exhaust pipe (10), and stopper (14) are all made of quartz glass; the heat-insulating sleeve (5) is filled with asbestos fiber or is evacuated.

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