JP3209920B2 - Method and apparatus for collecting fine particles using laser light - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the field of a technique for collecting ultra-fine particles floating in a room by collecting them by suction.
More specifically, technology to improve cleanliness by removing submicron particles suspended in the air in a clean room using a new method that does not use a filter, and quickly remove radioactive fine particles generated inside the reactor containment vessel etc. Belong to the field of technology.

[0002]

2. Description of the Related Art For example, in a clean room having a high cleanliness level required for a thin film formation, ion implantation, dry etching process and the like in a semiconductor manufacturing apparatus, the cleanroom is suspended in air to maintain and secure a high cleanliness level. Submicron contamination particles need to be removed. In addition, it is necessary to capture and remove submicron particles in order to prevent scattering of dust when cleaning the clean room.

In the nuclear industry, activated nuclear particles such as krypton, xenon, and iodine are generated in a nuclear reactor, and activated carbon, oxygen, and nitrogen are generated in a fusion reactor. It is necessary to prepare a countermeasure to be taken when air leaks into the containment of the furnace and becomes airborne as particles or radioactive ultra-fine aerosol particles. If various equipment used in the nuclear industry breaks down and small radioactive particles with a particle size of submicron to several microns scatter in the gas, remove the radioactive fine particles in the container storing the equipment before repairing. Must be recovered.

[0004] Particles of the order of microns can settle relatively easily over time, but submicron particles do not settle. Therefore, conventionally, after a relatively large particle settles, a completely protected worker enters while the fine particles are floating and collects by suction using a suction device equipped with an extremely fine mesh filter to collect radioactive materials. Had to be removed. In this case, since the sucked airflow is exhausted to the outside air, it was very difficult to prevent the extremely small particles adsorbed and leaked by the filter from escaping into the ambient air. Therefore, it is difficult to utilize a high-performance dust collector,
Once contaminated by the accident, it took about one to two months to remove the dust to a level where workers could use ordinary equipment.

[0005] As described above, radioactive fine particles of submicron size in the containment vessel cannot be easily recovered, and it is expected that countermeasures against failure will be delayed. Also, in the repair work for maintenance, if the fine particles scatter in the air, the workability was remarkably deteriorated due to the necessity of ensuring safety. Despite the necessity of removing submicron-sized contaminant particles suspended in the air in a clean room and removing ultra-fine aerosol particles with radioactivity from the air to collect dust. Therefore, it is not appropriate to use a dust collector, and it is not easy and expensive to remove sub-micron particles with a filter.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel means for removing submicron-sized fine particles from the air and collecting and removing them.

[0007]

In order to solve the above problems, a method for recovering fine particles according to the present invention comprises projecting a laser beam into an indoor space, arranging a transparent plate for the laser beam in an optical path of the laser beam, and arranging the laser beam. It is characterized in that sub-micron-order particles floating in the air that travel backward in the light traveling direction are captured, and a plate on which the particles are captured and fixed is removed. Further, it is preferable to select and use a laser beam having a wavelength determined for the target fine particle as the laser beam to be used.

Further, in order to solve the above-mentioned problems, the present invention provides a fine particle collecting apparatus, comprising: a laser emitting section; a mechanism for uniformly irradiating a laser beam to a target indoor space; A laser transmission plate holding mechanism for holding the laser transmission plate; a laser transmission plate supply unit for supplying the laser transmission plate one by one to the laser transmission plate holding mechanism; and a laser transmission plate collection unit for collecting the laser transmission plate after capturing the fine particles. It is characterized by. It is preferable that the laser emitting section emits a laser beam having a variable wavelength, and it is particularly preferable that the laser emitting section is a free electron laser.

The mechanism for uniformly irradiating the target indoor space with the laser beam may be a beam expander provided on the front surface of the laser emitting section, or a mechanism for rotating the laser emitting section body. You may. Further, a mechanism for uniformly irradiating the target indoor space with the laser light is a three-dimensional driving device, and the laser light emitting unit can be moved to a required position in the room. In addition, radioactive particles on the order of submicrons in the containment vessel may be targeted, and contaminant particles on the order of submicrons in the clean room may be targeted.

Conventionally, in laser manipulation research of particles, there has been a study on a macroscopic region in which particles of several microns to several tens of microns are captured in the air or water and remotely controlled. It has been clarified theoretically and experimentally that particles having a size of several tens of microns are repelled by a light force in a laser beam irradiation direction in a laser beam. On the other hand, there has been research on a microscopic region in which atoms and molecules are trapped in a vacuum and laser-cooled.

Regarding particles in the intermediate region having a size of submicron to nanometer order, Isao Shimizu et al. Used smoke of incense and polystyrene particles at the academic meeting of the Air Purification Association on June 14, 1995. As a result of the experiment, it has been disclosed that, contrary to the case of particles of several microns or more, the submicron particles in the laser beam fly against the laser beam irradiation direction and are attracted to the light source side. According to this, it was found that the larger the laser output, the faster the smoke particles move to the light source side, and at a laser output of 1 W, move at a speed of about 5 mm / s. Although the mechanism of this phenomenon has not yet been elucidated, the fact that not all of the 0.5 μm monodisperse polystyrene particles reverse in the direction of laser light irradiation indicates that the laser wavelength and the particle size are different. It was found that the relationship and the difference in composition influenced.

According to the present invention, as described above, the submicron particles in the laser beam fly against the laser beam irradiation direction,
This is based on the fact that it is attracted to the light source. According to the method of collecting fine particles of the present invention, submicron-order fine particles in the indoor space travel backward in the laser light path in the laser light traveling direction and are captured and fixed by the transparent plate. If the transparent plate is removed, submicron-order particles in the indoor space can be removed. In addition, the phenomenon that submicron particles reverse in the direction of laser light irradiation appears remarkably at a specific wavelength determined for the target particle, so that the laser light wavelength can be selected. preferable.

Further, according to the fine particle recovery apparatus of the present invention,
In order to uniformly irradiate the target indoor space with the laser light emitted from the laser emitting unit, submicron-order particles distributed in the room move toward the laser emitting unit and gather. Therefore, the collected fine particles are captured by the laser transmitting plate provided on the front surface of the laser light emitting section, and by replacing the dirty plate, the fine particles in the room can be removed to the outside. It is preferable that the wavelength of the laser beam can be changed according to the type of the fine particles in order to increase the collecting speed of the fine particles and improve the efficiency of the recovery. Here, it is preferable to generate a laser beam with a free electron laser generator because not only the laser output can be increased, but also the wavelength can be freely selected.

According to the mechanism for irradiating a laser beam with a beam expander provided on the front surface of the laser emitting section, there is no movable section for irradiation, so that one or an appropriate number of laser generators are provided in the space. Only needs to be left standing, the equipment is simple and the operation is easy. In addition, if a mechanism for rotating the laser light emitting unit body is used, it is possible to irradiate the room with a powerful laser beam that is not diluted by the beam expander, and the collection speed is improved. Furthermore, when the mechanism for irradiating the laser beam is a three-dimensional driving device and the laser light emitting unit is moved to a required position in the room, an appropriate trajectory is set even when the shape of the target room is complicated. Can be set and deal with.

When the target is radioactive particles of the order of submicron in the containment vessel, if the radioactive fine particles scatter in the gas due to a failure or the like, the conventional mechanical dust collector can hardly collect them. However, it is possible to remarkably improve the collection efficiency of radioactive fine particles of submicron size or less, and it is possible to reduce the exposure of workers during repair. In addition, the clean room level of the clean room can be efficiently secured and maintained by using the target of submicron-order contaminant particles in the clean room.

[0016]

DETAILED DESCRIPTION OF THE INVENTION At the academic meeting of the Air Purification Association on June 14, 1995, Isao Shimizu and his colleagues opposed the laser beam irradiation direction in contrast to the case where the submicron particles in the laser beam were several microns or more. Disclosed the fact that it flies and is attracted to the light source side. According to Shimizu's findings, there is a relationship between the laser wavelength and the size and composition of the particles, but in general, the fine particles move to the light source side faster as the laser output is larger, and in the case of smoke particles the laser output is 1 W It moves at a speed of about 5 mm / s.

The present invention is based on the newly discovered phenomenon that the submicron particles in the laser beam fly against the laser beam irradiation direction and are attracted to the light source side. The method and apparatus for collecting fine particles of the present invention
A powerful laser beam is projected into the target indoor space, and sub-micron-order particles that travel in the optical path of the laser beam in the reverse direction of the laser beam are captured by a transparent plate with the laser beam, and the particles are captured. It is characterized in that the fixed transparent plate is removed. Hereinafter, the method and apparatus of the present invention will be described in detail based on examples.

[0018]

Embodiment 1 FIG. 1 is a conceptual diagram showing a first embodiment of a particle collecting apparatus according to the present invention. As shown in FIG. 1, a particle collecting apparatus according to the present invention includes a laser emitting section 2 for guiding a laser beam generated by a high-power laser light source 1 through an optical fiber and emitting the laser beam to a target portion, and A beam expander 3 for appropriately irradiating the target space with uniform width, a glass plate supply unit 5 for supplying a transparent glass plate 4 that transmits laser light, and a supplied glass plate held in a laser beam path. A glass plate holding mechanism 6 and a glass plate collecting section 7 for collecting the fine particles after removing them from the optical path after they are deposited.

The laser light source 1 is a free electron laser generator, and generates high-power laser light using synchrotron radiation generated by an undulator inserted in the orbit of the electron storage ring. The free electron laser generator can change the wavelength of the laser light in a wide range by adjusting the energy of the electron mass circling the electron storage ring. The laser light emitting section 2 is a section that emits laser light into the target room, and arranges the laser light guided from the laser light source 1 and emitted from the end of the optical fiber into parallel light having a predetermined intensity.

The beam expander 3 is provided in the optical path of the laser light emitted from the laser light emitting section 2 so that the laser beam in the form of a parallel beam is secondarily widened so that the laser light reaches every corner of the room. In this case, it is possible to use an optical system or a spherical lens in which cylindrical lenses are combined so as to be orthogonal to each other in the light axis. For example, in the case of using a cylindrical lens, the laser beam having a point-like cross section is widened in the direction perpendicular to the lens axis by the first lens, and is changed into a linear cross section.
Can transform a laser beam having a linear cross section into a laser beam having a substantially rectangular cross section. In a spherical lens, a laser beam having a point-like cross section can be broadened to a laser beam having a circular section at a stroke.

The transparent plate 4 has a function of transmitting the laser beam irradiated from the back side, and having the function of trapping and escaping fine particles colliding at a constant speed and discharging the particles out of the system. Boards can be used. For this reason,
The apparatus comprises a glass plate supply unit 5 for supplying the transparent glass plate 4, a glass plate holding mechanism 6 for holding the glass plate 4 in the laser beam path, and a glass plate collection unit 7 for removing the fine particles from the optical path and collecting them.

The glass plate supply unit 5 includes a push rod unit for extruding new glass plates 4 one by one and supplying them into the optical path, and a stack unit for depositing a plurality of glass plates 4. When the plate 4 is supplied to the glass plate holding mechanism 6 and retreated, the glass plate 4 is sent out using a force of a spring or the like, and then the glass plates 4 are replenished one by one. The glass plate holding mechanism 6 includes a support that holds the glass plate 4 at a predetermined position in the laser beam path for a predetermined time. The glass sheet collecting section 7 is configured to supply a new glass sheet 4 supplied by a push rod of the glass sheet supply section 5 after an appropriate time has elapsed.
A box for receiving the glass plate 4 on which fine particles are extruded and preventing the once-deposited fine particles from diffusing. When a suitable number of contaminated glass plates are accumulated, these are removed from the system.

When using the fine particle collecting apparatus of the first embodiment of the present invention, the fine particle collecting apparatus is installed in a room in which submicron-sized fine particles are to be removed, and the laser light source 1 is adjusted to determine the type of the fine particles to be targeted. When a laser beam is generated by selecting a wavelength determined in advance by the center size, the laser beam radiated from the laser generator 2 as parallel light once becomes a laser beam 8 appropriately widened by the beam expander 3 to form a glass. The light passes through the plate 4 and is projected into the room. Then, the fine particles 9 suspended in the air in the room flow backward in the laser light irradiation direction, gather in the direction of the laser generation unit 2, collide with the glass plate 4 and adhere to the surface. Sticked fine particles 10
Since the transparency of the glass plate 4 with respect to the laser beam decreases when the density of the glass plate 4 increases, the glass plate supply unit 5 is operated to replace the glass plate 4 with a new glass plate 4 when the glass plate 4 is properly deposited. When an appropriate number of contaminated glass plates are accumulated in the glass plate collection unit 7, the glass plate collection unit 7 is taken out of the room and the contents are removed.

In this manner, the submicron particles are rejected to the outside of the system, and the concentration of the submicron particles in the room is reduced. Therefore, the contaminant particles in the room can be collected in combination with a particle collection method of another size. Can be. Therefore, it is possible to cope with the purpose of removing submicron-size particles in a reactor containment vessel or a clean room, for which there has been no suitable removal method conventionally. As the energy intensity of the laser beam in the laser beam 9 increases, the collection speed of the particles increases, and the particle collection efficiency increases. Since the fine particles are supplied from the surroundings by free diffusion to the area where the fine particles have been recovered and the fine particles concentration in the air is averaged, the laser beam does not need to spread throughout the room, but the Is preferred because the efficiency of assembling the fine particles is increased.

Although a free electron laser device is used as a laser light source in the above embodiment, a high-output tunable laser applicable to the present invention can be obtained by using a dye laser. Although a glass plate is used as a transparent plate that is transparent to laser light and can fix fine particles, a transparent plastic plate or a plastic sheet may be used depending on the wavelength and energy level of the laser light. When a sheet-like material is used, it is stored in a cassette as a continuous band, and the contaminated part is wound up while feeding out the clean part, so that it is easy to handle and prevents the collected fine particles from diffusing again. It has the advantage of being easier.

[0026]

[Embodiment 2] FIG. 2 is a conceptual diagram showing a second embodiment of the particle collecting apparatus of the present invention. In the second embodiment of the present invention, as compared with the first embodiment, the optical axis of the laser light is rotated instead of expanding the laser light with a beam expander in order to uniformly irradiate the target space. However, it is different. The other configuration is the same, and the description is omitted. Note that FIG. 2 shows an embodiment in which the particulate collection device of the second embodiment is applied to a reactor containment vessel for convenience of explanation, and the illustration of components other than the laser light emitting unit is omitted.

Reactor containment vessel 21 for containing reactor 20
In the above, it is preferable to provide a particulate recovery device in advance as a countermeasure when radioactive particulates leak from the reactor and peripheral equipment. In particular, when it is necessary for an operator to enter the containment vessel 21 for repair work, it is necessary to collect radioactive fine particles in the vessel before starting work and completely prevent the worker from being exposed to radiation. .
However, particles of the order of micron are settled relatively easily with the passage of time, but particles of the submicron are not settled and cannot be sufficiently collected by a mechanical suction device.

The particle collecting apparatus according to the present embodiment is developed to exhibit the performance in such a case. The laser generating section 24 is mounted on a rotating device 23 mounted on a mounting table 22. Have been. Laser light is supplied to the laser generation unit 24 from a large-capacity laser light source (not shown) via an optical fiber. The rotating device 23 has a function of swinging the optical axis of the laser beam 25 emitted from the laser generating unit 24 so as to draw an appropriate trajectory so as to be evenly distributed in the reactor containment vessel 21. It is driven two-dimensionally by the device.

Although not shown, as in the first embodiment, a transparent plate is supplied, supported,
A mechanism for recovery is installed. The mechanism related to the transparent plate may be rotated together with the laser generator 24, or may be fixed to the mounting table 22. When fixed to the mounting table 22, the mechanism does not move, so that there is an advantage that the difficulty in the device configuration is reduced and the load on the rotating device 23 is reduced.

In the particle collecting apparatus of the present embodiment, the laser beam is irradiated to the space in the container with a high energy intensity without widening, so that the submicron-sized particles are efficiently collected and the collecting speed is high. Further, in such a particle collecting apparatus, a large-sized laser light source device is installed outside the reactor containment vessel 21 so that a relatively simple and small laser generator 24 and the like are stored and operated in the vessel. As a result, the particle recovery device can be stored without greatly increasing the capacity of the containment vessel.

Since various devices are housed in the reactor containment vessel 21, it is impossible to scan the entire internal space with the rotation device 23 by placing the laser generator in one place. An appropriate number of other laser generators 26 are installed at appropriate positions of the reactor containment device 21 so as to cover the entire area.

By applying the particle recovery apparatus of this embodiment to the recovery of submicron-sized radioactive particles in a containment vessel, it is possible to quickly remove dangerous particles even if radioactive particles are released due to a failure. , You can take quick measures. Also, in the repair work for maintenance, the radioactive fine particles scattered in the air are recovered, and the safe work can be performed at an early stage.

In the above embodiment, the laser generator 24 itself is rotated in two axes by the rotation device 23 in order to rotate the optical axis of the laser light. The laser beam may be scanned by two rotating mirrors. The advantage of using a rotating mirror is that the rotating part is smaller.

[0034]

Third Embodiment FIG. 3 is a conceptual diagram showing a third embodiment of the fine particle collecting apparatus according to the present invention. The present embodiment is different from the first embodiment in that a laser light emitting unit is gripped and moved by a robot manipulator in order to uniformly irradiate a target space.
The other configuration is not different from that of the above-described embodiment, and the description is omitted. Note that, in FIG. 3, for convenience of explanation, as in the description of the second embodiment, an embodiment in which the particulate recovery device is applied to a reactor containment vessel is shown, and the display other than the vicinity of the laser emission unit is omitted.

The particle collecting apparatus according to the present embodiment is a reactor 20
The robot 30 is installed in the reactor containment vessel 21 storing the laser, and the laser generator 3 is attached to the hand of the manipulator 31.
2 is gripped. Laser light is supplied to the laser generator 32 from a large-capacity laser light source (not shown) via an optical fiber, and the laser light 33 is emitted from the laser generator 32. The robot 30 moves the laser generator 32 along a predetermined trajectory 34 so that the emitted laser light 33 can be distributed evenly in the reactor containment vessel 21. Although not shown, as in the first embodiment, a mechanism for supplying, supporting, and recovering the transparent plate is provided on the front surface of the laser generator 32, and moves together with the laser generator 32. It has become.

The apparatus for collecting fine particles of the present embodiment irradiates a laser beam to the space inside the container with a high energy intensity as in the second embodiment, so that the collection speed of submicron-size fine particles is high. In addition, since the large-sized laser light source device is installed outside the reactor containment vessel 21, it is not necessary to greatly increase the capacity of the reactor containment vessel, which requires equipment cost as the capacity increases. According to this embodiment, since the movement trajectory of the laser beam can be set using the existing robot, the entire space inside the reactor containment vessel 21 having a complicated shape with a small number of radix is scanned. be able to.

[0037]

As described above, the fine particle collecting apparatus of the present invention is capable of detecting submicron-size fine particles which have been hardly trapped by a filter without spontaneous sedimentation and suffered from the processing. Since they can be collected and removed by the action, it is necessary to avoid, for example, radioactive particles leaking in the containment vessel or contaminant particles in the clean room from being diffused by circulating air or leaking out of the filter and contaminating the outside air. It can be applied to what must be done.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a method for collecting fine particles of the present invention.

FIG. 2 is a conceptual diagram showing one embodiment of the fine particle recovery device of the present invention.

FIG. 3 is a conceptual diagram showing another embodiment of the fine particle collecting apparatus of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 laser light source 2 laser emission unit 3 beam expander 4 transparent glass plate 5 glass plate supply unit 6 glass plate holding mechanism 7 glass plate collection unit 8 laser beam 9 suspended particles 10 fixed particles 20 nuclear reactor 21 reactor containment vessel 22 mounted Table 23 Rotating device 24 Laser generator 25 Laser light 26 Laser generator 30 Robot 31 Manipulator 32 Laser generator 33 Laser light 34 Trajectory

Continuing from the front page (72) Inventor Hiroaki Shibasaki 118 Notsuka, Noda-shi, Chiba Prefecture Inside the Noda Plant of Kawasaki Heavy Industries, Ltd. (72) Inventor Isao Shimizu 5114, Nakazato, Urari-cho, Naka-gun, Naka-gun, Ibaraki 5 (72) Inventor ▲ Issue ▼ Tomoaki Sword 2-4 Shirakata Shirane, Tokai-mura, Naka-gun, Ibaraki Prefecture Within the Japan Atomic Energy Research Institute (72) Inventor Kazuyuki Takase 2-4-2 Shirakata-Shirane, Tokai-mura, Naka-gun, Ibaraki Prefecture Within the Japan Atomic Energy Research Institute (56) References JP-A-1-34439 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B01D 49/00 B01J 19/12

Claims (10)

(57) [Claims] 1. A submicron-order fine particle floating in the air that projects a laser beam into an indoor space, arranges a transparent plate for the laser beam in an optical path of the laser beam, and reverses in the traveling direction of the laser beam. A method for collecting fine particles, comprising removing the plate on which fine particles are captured and fixed. 2. The method for collecting fine particles according to claim 1, wherein a laser light having a wavelength determined for the target fine particles is selected and used as the laser light. 3. A laser light emitting unit, a mechanism for uniformly irradiating a laser beam to a target indoor space, a laser transmitting plate holding mechanism for holding a laser transmitting plate in front of the laser emitting unit, and a laser transmitting plate holding mechanism. A fine particle collection device comprising: a laser transmission plate supply unit that supplies laser transmission plates one by one; and a laser transmission plate collection unit that collects the laser transmission plate after capturing the fine particles. 4. The particle collecting apparatus according to claim 3, wherein said laser light emitting section generates a laser beam with a variable wavelength. 5. The particle collecting apparatus according to claim 4, wherein said variable wavelength laser light is a free electron laser. 6. The particle collecting apparatus according to claim 3, wherein the mechanism for uniformly irradiating the target room space with the laser light is a beam expander provided on a front surface of a laser light emitting unit. A fine particle recovery apparatus characterized by the above-mentioned. 7. The particle collecting apparatus according to claim 3, wherein the mechanism for uniformly irradiating the target room space with the laser light is a mechanism for rotating the laser light emitting unit main body. Characteristic particle collection device. 8. The particle collecting apparatus according to claim 3, wherein the mechanism for uniformly irradiating the target room space with the laser beam is a three-dimensional driving device, and the laser light emitting unit is provided in the room. A fine particle collection device that is moved to a required position. 9. The particle collecting apparatus according to claim 3, wherein the target chamber is a reactor containment vessel, and the particles are submicron-order particles. Synchrotron radiation generator. 10. The apparatus for collecting fine particles according to claim 3, wherein the target room is a clean room, and the fine particles are submicron-order particles. apparatus.