JPH04316000A - Method for dismantling nuclear reactor using laser beam - Google Patents

Abstract

PURPOSE:To dismantle a biological shield wall concrete structure around a nuclear reactor, which structure is difficult for workers to directly decompose, by cutting the structure using laser beams. CONSTITUTION:A laser transmitter 4 and a remote control unit 5 are installed outside a nuclear reactor containment vessel 1. Laser beams from the laser transmitter 4 are introduced into the containment vessel 1 by a horizontal light guide tube 6 installed in such a way as extending inside and outside of the containment vessel 1. A light guide tube 8 is connected to the horizontal light guide tube 6 via a bent mirror 7 and a working head 9 is provided at the end of the light guide tube 8.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] This invention relates to the demolition work of nuclear reactor facilities, and in particular to a method for dismantling nuclear reactor facilities by cutting concrete with a laser beam in places where workers cannot work for long periods of time. .

0002

[Prior Art] Methods for demolishing concrete facilities include concrete cutter method, core boring method,
Abrasive water jet construction methods are commonly used.

0003

[Problem to be Solved by the Invention] When dismantling a nuclear reactor facility, there are areas where the radiation dose rate is high, such as reactor bio-insulation walls or thermal insulation walls (in the case of BWR reactors), and workers are directly exposed to them. There are places where it is difficult to work for long periods of time. There is a problem in that demolition work of concrete facilities in such places using the above-mentioned conventional method takes a very long time. In particular, the bio-shielding concrete walls of nuclear reactors are extremely thick and have a large amount of reinforcing steel, and in some cases, structures are made of thick steel plates and concrete. Considering this point, it is extremely difficult to dismantle the facility using conventional construction methods in a special environment where the radiation dose rate is high.

[0004] By the way, Japanese Patent Application Laid-Open No. 2-151382 (B2
3K26/00) discloses a method for performing laser welding of nuclear reactor facilities by remote control. This uses an optical fiber to connect a laser oscillator installed outside the reactor to a welding head inside the reactor, and performs laser welding inside the reactor while controlling the welding head remotely. In this very localized laser welding process, the welding process can be controlled from outside the reactor using optical fibers, but cutting and demolishing the vast concrete structures surrounding the reactor requires an extremely large amount of energy. A high-density laser is required, and the configuration of the laser welding machine using optical fibers as described above cannot cope with this at all.

[0005] This invention was made in view of the above-mentioned conventional problems, and its purpose is to provide a realistic and practical method for cutting and dismantling huge concrete structures of nuclear reactor facilities using a laser beam. Our goal is to provide the following.

[0006]

[Means for Solving the Problems] Accordingly, in the present invention, a laser oscillator and a remote control device are installed outside a reactor cavity or a reactor containment vessel, are connected to the laser oscillator, and are replaced depending on the required length. The horizontal light guide tube made possible is guided above the reactor cavity, and on the reactor cavity, other light guide tubes are connected to the horizontal light guide tube via a bent mirror in an appropriate refraction pattern. A processing head with a built-in long-focus focusing optical system was attached to the tip, and the laser beam focused by this processing head was used to irradiate and cut the biological shielding wall concrete of the nuclear reactor.

[0007]

[Operation] Since the laser beam is guided into the reactor cavity using a light guide, a high-energy laser beam can be used without any problem. By connecting another light guide tube to the horizontal light guide tube via a bent mirror above and within the reactor cavity, the path through which the laser beam is guided can be made into an optimal refraction pattern as necessary. By remotely controlling the connection of these light guide tubes and the position of the processing head, we can use a high-energy laser beam to target any location within the reactor cavity to create concrete that has a large amount of reinforcing steel or is integrated with thick steel plates. Structures can be efficiently cut and dismantled.

[0008] In particular, the larger the amount of reinforcing bars and steel materials contained in concrete, the easier it is to cut with a laser beam.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the method of the present invention for dismantling a nuclear reactor biological shielding wall using a laser beam. 1 is a reactor containment vessel, and 2 is ancillary facilities attached to the outside of the containment vessel 1. A laser oscillator 4 and a remote control device 5 are installed in this auxiliary facility 2. Inside the containment vessel 1 is a biological shielding wall 3 made of a thick concrete structure that is subject to dismantling.

[0010] In order to guide the laser beam from the laser oscillator 4 into the containment vessel 1, a horizontal light guide tube 6 is installed to penetrate the wall of the containment vessel 1. The light guide tube 6 is different from an optical fiber,
Laser beams with extremely high energy density can be guided without causing problems such as heat generation. Horizontal light guide 6
can be replaced with one of the required length depending on the construction site.

Inside the containment vessel 1, a horizontal light guide pipe 6
A bent mirror 7 for refracting the laser beam at right angles is attached to the tip of the mirror, and a light guide tube 8 for guiding the refracted laser beam is connected to the horizontal light guide 6. In this example, the light guide tube 8 is vertically mounted downward. A processing head 9 is provided at the tip of this downward light guide tube 8 . The light guide tube 8 and the processing head 9 are fixed to a suitable wall portion in the storage container 1 using a suitable fixing device 10 as shown in the figure.

The processing head 9 has a built-in optical system that refracts the laser beam from the light guide tube 8 at right angles, and a long-focus optical system that focuses the laser beam toward the concrete wall to be cut. ing. The laser beam 11 thus focused is irradiated toward a predetermined location on the shielding wall 3 .

Although not shown, the horizontal light guide tube 6 is equipped with an air supply tube for sending high-pressure gas, and a predetermined gas is supplied into the pressure vessel 1 from a compressor installed outside the containment vessel 1. Alternatively, air is forced to be sent, and the gas is ejected from a jet nozzle attached to the processing head 9 toward the cutting location, and concrete, etc., which is melted by the laser beam, is quickly removed from the cutting groove. There is.

It should be noted that not only the horizontal light guide tube 6 but also the downward light guide tube 8 can be exchanged or expanded or contracted to a length as required, and an appropriate robot is used as the fixing device 10.
This can be freely controlled from the remote control device 5.

[0015]

Effects of the Invention In this invention, a laser beam from a laser oscillator installed outside the reactor cavity or reactor containment vessel is guided into the reactor cavity by a horizontal light guide tube installed outside the reactor cavity. The light guide tube is connected to another light guide tube via a bent mirror in an appropriate refraction pattern, and a processing head is installed at the tip of the light guide tube to melt the biological shielding concrete wall of the reactor with a focused laser beam. Since the material is cut using a laser beam with very high energy density, it is possible to efficiently dismantle the reactor bioshielding wall. The horizontal light guide tube and the light guide tube connected thereto can be replaced or expanded/contracted to an appropriate length depending on the construction site, and can be cut at any point by remote control. In particular, concrete structures with a large amount of iron are easier to cut with a laser beam, and the cutting speed is significantly faster than with conventional construction methods. In addition, since the configuration of the device is simple, it has excellent remote operability and fewer failures. Furthermore, because there are fewer secondary products such as dust generated during cutting, the amount of radioactive waste can be reduced compared to conventional construction methods.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the construction method of the present invention for dismantling a nuclear reactor using a laser beam.

[Explanation of symbols]

1 Reactor containment vessel 2. Ancillary facilities 3 Reactor shielding wall 4 Laser beam oscillator 5 Remote control device 6 Horizontal light guide tube 7 Vent mirror 8 Vertical light guide tube 9 Processing head 11 Laser beam 12 Reactor cavity

Claims (1)

[Claims] Claim 1: A laser oscillator and a remote control device are installed outside the reactor, and a horizontal light guide tube connected to the laser oscillator and replaceable depending on the required length is guided into the reactor containment vessel. In the reactor containment vessel, other light guide tubes are connected to the horizontal light guide tube via a bent mirror in an appropriate refraction pattern, and a long focal length focusing optical system is built into the tips of these light guide tubes. A method for dismantling a nuclear reactor using a laser beam, the method comprising: attaching a head; and irradiating a laser beam focused by the processing head to the concrete wall of the nuclear reactor to cut it.