JPS6332159B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a nuclear reactor repair system, and more particularly to a nuclear reactor repair system that can freely repair any location within a nuclear reactor using a laser beam transmission/concentration device.

Nuclear power plants undergo periodic inspections during their service life, and if any abnormalities are discovered in the reactor vessel or its internal structures during these inspections, welding, cutting, etc. will be carried out on the abnormal areas. Repairs will be carried out.

Particularly in fast-breeder nuclear reactors that use sodium as a coolant, the reactor vessel and reactor internals are usually constructed of austenitic stainless steel, so it is used as a general structural material. For example, compared to austenitic carbon steel, it is difficult to conduct heat, has a large coefficient of thermal expansion, and is subject to large thermal deformation due to heat input during welding.

In addition, when attempting to repair and weld abnormalities on the inner surface of the reactor vessel or structural materials after the start of reactor operation,
The difficulty is further increased by the addition of various constraints as described below.

(a) Since the product has already been completed and has started to be used, it is difficult to improve the shape and dimensions, etc. that have changed due to repair welding by machining, etc. after repair welding to within the standard tolerance, and deformation may occur. It is necessary to adopt a repair welding method with less damage.

(b) Due to the special nature of liquid metal cooled fast breeder reactors, the so-called under-the-plug refueling method is usually adopted, so the reactor vessel lid cannot be easily removed, so repair work must be carried out on the reactor vessel lid. It is requested that this be done without removing the

(c) The radiation density inside the reactor vessel is high, and entry and access for workers is severely restricted, so repair work must be carried out by remote control.

(d) For welding parts that require high dimensional accuracy,
It is necessary to apply a high energy density welding method that causes less deformation of the parts after repair welding.

(e) Because the density of radiation inside the reactor vessel is high, it is necessary to provide appropriate radiation shielding for repair equipment used inside the reactor.

The present invention has been made in consideration of the above-mentioned problems, and is a nuclear reactor capable of repair welding and fusing abnormal points existing at any position within the reactor pressure vessel using a high-energy-density laser beam. The aim is to provide repair equipment.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

Figure 1 shows the reactor repair system of the present invention installed in a sodium-cooled fast breeder reactor.
Further, FIG. 2 shows a longitudinal sectional view taken along the line AA in FIG. 1.

In these figures, the upper end opening of the pressure vessel 2 housing the reactor core 1 is inserted into a large-rotation plug 3a, a medium-rotation plug 3b drilled in the large-rotation plug, and a through hole bored in the medium-rotation plug. It is sealed with a triple plug consisting of a small rotating plug 3c.

Note that 4 indicates a nozzle through which sodium coolant flows into the reactor vessel, and 5 indicates a core upper mechanism.

A drive unit 6a of a laser repair welding/cutting device 6 is mounted and fixed on the large-rotary plug 3a, and an extension pipe portion 7 extending downward is inserted into the reactor vessel 2 inserted into a through hole provided in the large-rotary plug 3a. It stands out.

A laser transmission/focusing device 8 is attached to the lower end of the extension tube section 7.

Incidentally, reference numeral 8a indicates an openable and closable shutter provided at the laser beam outlet in order to protect the inside of this laser transmission/concentration device 8 from the radiation source in the furnace.

The upper end of the drive unit 6a of the laser repair welding/cutting device 6 is connected to a laser oscillation device 10 via laser beam transmission devices 9a, 9b, and 9c.

This laser oscillation device 10 is controlled by a control device 11.
The operation is controlled by

Further, a drive section 12a of a laser repair welding/cutting device 12 provided separately from the laser repair welding/cutting device 6 is mounted and fixed on the medium rotation plug 3b, and an extension pipe portion 13 extending downward is fixedly mounted on the middle rotation plug 3b. It is inserted into a through hole drilled in the rotary plug 3b and protrudes into the reactor vessel 2.

A laser transmission/concentration device 14 configured similarly to the laser transmission/concentration device 8 is attached to the lower end of this extension tube portion 13.

The laser transmission/focusing devices 8 and 14 are connected to the extension pipe section 7,
It is configured such that it can be positioned at an arbitrary height by expanding and contracting 13, and can guide the laser beam in an arbitrary direction by rotating the rotary plugs 3a, 3b, 3c and extension tube parts 7, 13.

Repair work inside the reactor vessel is performed as described below using the nuclear reactor repair apparatus of the present invention configured as described above. That is, as described above, the laser repair welding/cutting devices 6 and 12 are installed on the large-rotation plug 3a and the medium-rotation plug 3b, and the laser repair welding/cutting device 6 is equipped with a laser beam transmission device 9.
The laser transmitter 10 is optically connected via a, 9b, and 9c.

Next, drive the rotation drive device 15 to rotate the large rotation plug 3a and/or the medium rotation plug 3b,
The combination of these rotations moves the laser repair welding and cutting devices 6 and 12 to the desired position.

In this case, depending on the extent of the repair inside the reactor vessel, if the fuel loaded in the reactor core 1 is taken out of the reactor vessel 2 and the coolant sodium is drained, repair work can be carried out on the reactor. The laser beam can reach not only the vessel nozzle 4 but also almost any position within the reactor vessel 2.

In this way, when the laser repair welding/cutting devices 6, 12 are stopped at the predetermined positions, the drive unit 6
a, 12a to give vertical movement and rotational movement to the extension tube parts 7, 13, and move these extension tube parts 7, 13 to a position where the laser beam reaches a predetermined position.
to be fixed.

Next, the angles of the reflecting mirrors 8b and 14b disposed in the laser transmission and condensing devices 8 and 14 are remotely controlled by the driving devices 6a and 12a so that the laser beam reaches a predetermined position. A laser beam is transmitted from the laser transmitter 10.

The emitted laser light is transmitted to a laser transmission device 9c,
9b, 9a, the driving part 6a, and the extension tube part 7, the laser beam is guided to the reflecting mirror 8b, and the laser beam reflected by the reflecting mirror 8b passes through the shutter 8a, and is provided at the tip of the laser repair welding/cutting device 12. After passing through the shutter 14a of the laser transmission/focusing device 14, the light reaches a reflecting mirror 14b, is reflected by the reflecting mirror 14b, passes through the shutter 14c, and reaches the repaired area.

Note that the energy of the laser beam irradiated onto the repaired location is controlled by the control device 11 to the optimum intensity for welding or cutting the repaired location.

As a result, repair welding or cutting of areas requiring repair can be performed easily and reliably with stable quality.

When repairing a nuclear reactor using the nuclear reactor repair apparatus of the present invention as described above, the following various effects can be obtained.

(a) In the case of a liquid metal cooled fast breeder reactor, repair welding and cutting inside the reactor vessel can be easily and reliably performed remotely with stable quality while maintaining its characteristic so-called under-the-plug concept.

Furthermore, since laser light is used, even if the length of the nuclear reactor vessel in the axial direction becomes significantly long, it can be handled relatively easily.

(b) As the upper surface of the reactor vessel lid is extremely densely packed, the laser beam can reach any location within the reactor vessel while minimizing the occupied area, significantly expanding the repairable area. be done.

(c) Since high energy density welding method is adopted,
Thermal deformation of the area to be repaired is extremely small, and changes in the metal structure of the area to be repaired can be limited to very localized areas, allowing for excellent repair welding and cutting.

In addition, the finished condition is very good, so welding and
Since various non-destructive tests can be performed as is without surface curing (grinding, etc.) after cutting, the construction period and man-hours can be shortened.

(d) Multiple laser repair welding/cutting devices are installed, and the laser beam emitted from one device is received by another device or transferred to a third or subsequent device. By combining welding and cutting equipment to form a single laser optical system, it is possible to repair any desired location within the reactor vessel, including repairing the underside of the reactor vessel lid (work must be done completely upwards). It can make work possible.

Figure 3 shows a laser repair welding/cutting device 16 for repairing the underside of the reactor vessel lid.
This shows an example of the combination of a and 16b, and the laser repair welding/cutting device 16 located on the right side of the figure
b is provided with a laser transmission/focusing device 18a formed to protrude laterally from the extension tube 17b, and an opening 19 is formed in the upper surface of this protrusion.

In this way, the laser repair welding/cutting device 16a,
16b, the laser beam reflected by the reflecting mirror 20a of the laser repair welding/cutting device 16a is reflected by the reflecting mirror 20b of the laser transmitting/concentrating device 18a, and from the opening 19,
Laser light can reach the lower surface of the reactor vessel lid.

By combining these effects, the present invention allows repair of a nuclear reactor to be carried out easily and reliably.

In addition, in the above explanation, a liquid metal cooled fast breeder reactor equipped with a triple rotating plug was explained as an example.
The invention is not limited thereto, but can be broadly applied both in the case of dual rotating plug reactors and in other types of reactors.

Furthermore, in the above example, a case was shown in which the laser transmission/focusing device 14 on the side of the laser repair welding/cutting device 12 was used as a reflecting mirror, but the laser transmitting device 10
The output of
The condensing device 8 side may be used as a reflecting mirror.

[Brief explanation of the drawing]

Figure 1 shows a laser repair welding process according to an embodiment of the present invention.
FIG. 2 is a longitudinal cross-sectional view of a nuclear reactor in which a cutting device is installed, FIG. 2 is a cross-sectional view taken along the line AA in FIG. 1, and FIG. FIG. 1... Core, 2... Pressure vessel, 3a... Large rotation plug, 3b... Medium rotation plug, 3c... Small rotation plug,
5... Core upper mechanism, 6... Laser repair welding/cutting device, 7... Extension tube, 8... Laser transmission/focusing device, 8
a...Shutter, 9a-9c...Laser transmission device, 1
0...Laser transmitting device, 11...Control device, 12...Laser repair welding/cutting device, 13...Extension pipe, 14...
Laser transmission/focusing device.

Claims (1)

[Claims] 1. A first extension tube hanging down from a large rotation plug that is rotatably provided to cover the upper part of the reactor vessel, a first laser condenser provided at the bottom of this first extension tube, and a large rotation plug that is installed at the bottom of the first extension tube. A second extension tube hanging down from the rotary plug rotatably provided on the plug, and a second laser condenser provided at the bottom of the second extension tube so as to be able to transmit light to the first laser condenser. A nuclear reactor repair system comprising: an optical device; and a laser oscillation device optically connected to at least one of the first laser focusing device and the second laser focusing device.