JP2003028990A - Cutting system and method for radioactive solid waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an underwater cutting system for radioactive solid waste, capable of speedily and stably cutting, reducing secondary waste amount and recovering the waste. SOLUTION: The system has a water tank 23 for dipping underwater an article to be cut, vertical moving means 7 and 9 for moving the article to be cut in vertical direction, by vertically holding underwater the longitudinal direction of the article, cutting nozzle 2 arranged underwater for casting laser light to cutting part of the underwater article, laser oscillator 5 arranged outside the water tank, transmission means 6 for transmitting laser light generated in the laser oscillator to the cutting nozzle, gas supply means 51 for discharging assist gas from the tip of the cutting nozzle, secondary product recovery means 4 and 21 for recovering in underwater the secondary product generated, when the article is cut with laser light, isolation film 22 covering the article and entire cutting nozzle underwater and is capable of opening and closing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to radioactive solid wastes such as nuclear equipment parts, especially boiling water nuclear power plants (BW).
R) and the like, the present invention relates to a system and method suitable for cutting highly radioactive solid waste such as used control rods and used fuel channel boxes in water.

[0002]

2. Description of the Related Art For example, control rods and fuel channel boxes used in BWRs are temporarily stored in water in their original form as highly radioactive solid waste after a predetermined operating period. Highly radioactive solid waste is based on, for example, stainless steel and is very difficult to cut.

An underwater cutting apparatus for highly radioactive solid waste is disclosed in, for example, Japanese Patent Publication No. 3-49080.
According to this prior art, the used fuel channel box having a rectangular cross section and the used control rod having a cross-shaped cross section can be cut by plasma in the direction along the axis line as the objects to be cut.

A spent fuel channel box having a rectangular cross section is constructed by a torch which is diagonally opposed to each other.
One corner and its diagonal are cut, and the shape of the hook is "ku".
A square-shaped cut piece is obtained. The used control rod with a cruciform cross section has a hook-shaped "ku" that is cut at the center by a torch.
A square-shaped cut piece is obtained. These cut pieces have substantially the same shape and can be stacked and stored, which improves the utilization efficiency of the storage space.

The torch is fixedly arranged, and the cutting is performed by the hot water jet cutting method while vertically moving the object side. In this method, a plasma arc is generated from the tip of the wire electrode, and the generated heat locally melts and cuts the object to be cut. The water jet is used to remove dross and fission products generated during cutting. Since the torch uses arc discharge, it is necessary to keep the distance between the tip of the torch and the object to be cut constant.

A disc-shaped member called a speed limiter is fixed to one end of the used BWR control rod in the axial direction. In order to cut off the speed limiter part by the fixed torch, the used control rod is moved in the horizontal direction and the cutting is made perpendicular to the axis. At this time, the device for moving in the horizontal direction and the device for moving up and down described above are exchanged for use.

[0007]

In the above-mentioned means using the solute electrode type water jet, the water containing a large amount of radioactive substances must be managed, so that the running cost also increases. Further, since the cutting speed is slow, the time required for volume reduction becomes long. It is an object of the present invention to provide a system and method that have a fast and stable cutting speed, a small amount of secondary waste generated by cutting, and can be collected.

[0008]

The present invention achieves the above object, and the invention of claim 1 is a radioactive solid waste cutting system for cutting radioactive solid waste in water as an object to be cut. In, a water tank for immersing the object to be cut in water, and a vertical moving means for vertically moving the object to be cut in the water while vertically holding the longitudinal direction of the object to be cut. A cutting nozzle arranged in the water for irradiating the underwater cutting portion of the object to be cut with water, a laser oscillator arranged outside the water tank, and a laser beam generated by the laser oscillator. To the cutting nozzle, a gas supply unit for ejecting an assist gas from the tip of the cutting nozzle, and a secondary product generated when the object to be cut is cut by the laser light. Having a secondary product collection means for collecting at serial water, and a closable separation membrane wherein covering the entire object to be cut and the cutting nozzle with the water, characterized by.

According to the first aspect of the present invention, there is provided a system in which, when an object to be cut is cut in water, the cutting speed is fast and stable, and the amount of secondary waste generated by the cutting is small and can be collected. You can

Further, the invention of claim 2 is the radioactive solid waste cutting system according to claim 1, further comprising horizontal moving means for moving the cutting nozzle in a horizontal direction to cut the object in a horizontal direction. It further has. According to the invention of claim 2, in addition to the effects and advantages of the invention of claim 1, the lower end side of the object to be cut can be horizontally cut in water.

Further, the invention of claim 3 is the radioactive solid waste cutting system according to claim 1 or 2, wherein the cutting nozzle is provided in the cutting nozzle when the ejection of the assist gas is stopped. It has a shut-off means for preventing the intrusion of water. According to the invention of claim 3, in addition to the effects and advantages of the invention of claim 1 or 2, the life of the cutting torch can be extended by blocking the intrusion of water into the inside of the nozzle.

The invention according to claim 4 is the radioactive solid waste cutting system according to claim 1, 2 or 3, further comprising a detector for detecting the success or failure of the cutting.
Is characterized by. According to the invention of claim 4, claim 1, 2
Alternatively, the function and effect of the invention of 3 can be obtained, and it becomes possible to recognize that the disconnection was not performed for some reason, and the disconnection can be temporarily suspended and restarted from that site. improves.

The invention of claim 5 is the radioactive solid waste cutting system according to any one of claims 1 to 4, wherein the secondary product recovery means is the cutting nozzle when viewed from the object to be cut. It is arranged at a position opposite to the cutting nozzle on the opposite side. According to the invention of claim 5, the action and effect of the invention of any one of claims 1 to 4 can be obtained, and in addition, 2 caused by laser cutting can be obtained.
Laser cutting can be performed while collecting the next product.

The invention of claim 6 is characterized in that, in the radioactive solid waste cutting system according to claim 5, the secondary product recovery means is also disposed above the isolation membrane. And According to the invention of claim 6, in addition to the effects and advantages of the invention of claim 5, laser cutting can be performed while collecting the secondary products generated during laser cutting.

According to a seventh aspect of the present invention, in the radioactive solid waste cutting system according to any of the first to sixth aspects, the cutting nozzle is fixed, and the object to be cut is moved by the vertical moving means. However, it is characterized in that the object to be cut can be cut. According to the invention of claim 7, the action and effect of the invention of any one of claims 1 to 6 can be obtained, and since the cutting can always be performed at the same place, the recovery of the secondary product becomes easy.

Further, the invention of claim 8 is the radioactive solid waste cutting system according to any one of claims 1 to 7, wherein there are two cutting nozzles arranged in the water,
It has a means for distributing the laser light generated by the laser oscillator to the two cutting nozzles, and is configured to be able to simultaneously cut two points of the object to be cut while moving the object to be cut in the vertical direction. It is characterized by being.

According to the invention of claim 8, the operation and effect of the invention of any one of claims 1 to 7 can be obtained, and, for example, a channel box or the like can be cut efficiently and quickly.

Further, the invention of claim 9 is a method for cutting radioactive solid waste in water, wherein the radioactive solid waste is cut as an object to be cut in the water. The cutting nozzle is disposed in the water in order to irradiate a laser beam to the underwater cutting portion of the object to be cut, and the assist gas is ejected from the tip of the cutting nozzle, and the cutting nozzle is disposed outside the water tank. Laser beam is generated by the laser oscillator, the laser beam generated by the laser oscillator is transmitted to the cutting nozzle to irradiate the cutting portion with the laser beam, and the object to be cut is underwater while irradiating the laser beam. Is moved in the vertical direction and the secondary product generated when the object to be cut is cut by the laser light is collected in the water.

According to the invention of claim 9, there is provided a method for cutting an object to be cut in water, the cutting speed is fast and stable, the amount of secondary waste generated by the cutting is small, and the secondary waste can be collected. You can

The invention of claim 10 is the method for cutting radioactive solid waste according to claim 9, wherein the assist gas is air, nitrogen, argon, or a mixture containing any of these. There is a feature. According to the invention of claim 10, in addition to the effects and advantages of the invention of claim 9, the laser absorptance of the laser irradiation portion can be stabilized and laser cutting can be stabilized.

[0021]

DETAILED DESCRIPTION OF THE INVENTION A radioactive solid waste cutting system and method according to an embodiment of the present invention will be described below with reference to the drawings. Regarding the first embodiment,
This will be described with reference to FIGS. FIG. 1 shows a perspective outline of an embodiment of the present invention. The used control rod 1, which is a highly radioactive solid waste, is held by the restraint jig 3 while standing almost vertically. The parts to be cut according to the present invention are the lower blade 32 and the tie rod 31 forming the axis of the control rod 1 shown in FIG. 3, but both are made of stainless steel such as SUS304 and SUS316L. Cutting torch 2 and cutting torch 2
The secondary product recovery device 4 installed opposite to is fixed so as not to move, and is the carrier device 9 to which the control rod 1 is fixed.
Has a structure for cutting by moving up and down along the rail 10.

The laser light emitted from the laser oscillator 5 is transmitted to the cutting torch 2 by the laser light transmission device 6, is condensed inside the cutting torch 2, and is then cut from the tip of the cutting torch 2. Cutting is performed by irradiating the surface of the control rod 1, which is an object.

At the lower end side of the used control rod 1, a cutting torch 12 which is a horizontal cutting means is installed as shown in FIG. Unlike the cutting torch 2, the cutting torch 12 is equipped with a mechanism that moves in the horizontal direction, is arranged so as to be parallel to the used control rod 1, and separates a portion called a speed limiter near the lower end of the control rod. Used. The cutting torch 2 shown in FIG. 1 and the cutting torch 12 shown in FIG. 2 may be provided as dedicated ones, or may be moved and used as the same one.

As shown in FIGS. 2 and 3, when cutting the speed limiter, the position of the control rod 1 is determined by using the rotating mechanism 15 so as to be perpendicular to the cutting torch 12. When the control rod 1 is rotated using the rotating mechanism 15, the cutting torch 12 and the secondary product recovery device 14 are lowered to a position where they do not interfere with each other. After determining the position of the control rod 1, the cutting torch 12 and the secondary product recovery device 14 are moved to predetermined positions. After that, the cutting torch 12 is moved horizontally to irradiate a laser beam to perform cutting.

After cutting one lower blade 32, the cutting torch 12 and the secondary product collecting device 14 are lowered to a position where they do not interfere with each other, and then the control rod 1 is rotated by 90 ° using the rotating mechanism 15 to cut. The torch 12 and the lower blade 32 are arranged vertically. By repeating the above operation four times, all four lower blades 32 are cut, and the speed limiter can be separated from the control rod 1.

The control rod 1 from which the speed limiter is separated is held by the restraint jig 13, and the separated speed limiter is held by the lower restraint jig 16. For example, the cut speed limiter can be moved to a speed limiter collection box (not shown) for storage if the lower restraint jig 16 is provided with a moving mechanism.

The movement of the cutting torch 12 and the movement of the carrying device 9 are performed as a sequence control by the control device 8 which is a control means. As shown in FIG. 4, the control rod 1 cutting device arranged in the pool 23 is surrounded by a flexible isolation membrane 22 which is an isolation means. The isolation film 22 isolates the peripheral region from other regions in the pool 23, and partitions the water so that the influence of cutting does not affect other regions. The isolation membrane 22 can be brought into an open state by suspending the upper edge and moving it downward in a bellows shape. Further, the isolation film 22 may be a hard partition wall and may be opened and closed by a door.

The cutting torch 2 is the cutting torch 2 shown in FIG.
By the copying devices 34 provided on both sides of, the distance from the object to be cut can be kept constant. As the copying method, contact-type copying using a roller or non-contact-type copying such as a distance sensor may be used. Further, without using the copying apparatus 34, it is possible to scan the cutting torch before cutting to perform teaching in advance and then cut. If the distance between the nozzle at the tip of the cutting torch 2 and the object to be cut is in the range of 0.5 to 5 mm, the cutting can be performed.

As shown in FIG. 6, a shutter 52 is provided inside the cutting torch 2 so that water does not enter inside when the cutting is not performed. The shutter 52 has a structure that operates in parallel with the cutting proceeding direction so that it does not interfere with the object to be cut during cutting. The shutter 52 may be made of any material, such as quartz glass, as long as it does not deteriorate in water and in a radiation environment. When opening the shutter 52, the assist gas for cutting is always supplied from the gas supply port 51, and it is considered that the supply of assist gas is stopped after closing the shutter 52 at the end of cutting.

When the cutting is performed, the cutting is performed by irradiating the laser beam while ejecting the assist gas from the tip of the nozzle. The gas used is preferably air, but a gas containing nitrogen or oxygen can also be cut. The gas supply pressure is
It is possible to cut at a pressure of 0.1 to 20 MPa. The higher the pressure, the thicker the object to be cut becomes, and the stainless steel having a maximum thickness of 25 mm at 20 MPa can be cut. Secondary products such as dross generated during cutting are recovered by secondary product recovery devices 4 and 14 in which cutting torches 2 and 12 are provided on the opposite side of the control rod.

As shown in FIG. 7, the secondary product recovery device 4,
14 is, for example, a secondary product recovery port 41, a filter 4
3, suction device 44, collection box 42 and discharge port 45
Composed of. The gas containing dross, fumes (metal vapor), etc. generated at the time of cutting is sucked inside together with water by the suction device 44 through the recovery port 41. Of the sucked secondary products, dross is collected in the recovery box 4 by its own weight.
Recovered to 2. Further, the gas containing fume absorbs the fume when passing through the filter 43 to make it into a clean state, and then is discharged from the discharge port 45 together with water.

The secondary product recovery device preferably has the above-mentioned structure, but it is possible to recover the secondary product to some extent from the recovery port 41 by the assist gas used at the time of cutting without performing suction by the suction device 44. Further, it is possible to collect both dross and fumes only by the filter 43 without the recovery box 42.

The secondary product recovery port 41 is provided with a cutting success / failure sensor 46, and is provided with a mechanism for transmitting a signal for stopping cutting to the controller when the cutting is not performed for some reason. ing.

Using the apparatus having the above construction, the tie rod 32 located at the center of the control rod 1 is cut after cutting the speed limiter. Control rod with the speed limiter cut
If the rotating mechanism 15 or the restraint jig 13 shown in FIG. 2 is provided with a moving function, the movement of the vehicle to the carrying device 9 can be automatically performed under the control of the controller 8. A crane or the like may be used.

The control rod 1 with the speed limiter cut is shown in FIG.
It is placed on the carrying device 9 shown in FIG. As shown in FIG. 5, the restraining jig 3 has fixing tabs 35.
Are provided on both sides, and the control rod 1 is fixed by two restraining jigs 3. After the control rod 1 is fixed by the restraining jig 3, the cutting torch 2 is placed on the top of the control rod 1 by the carrying device 9.
Move so that is placed.

After the position is determined, the assist gas is supplied from the gas supply port 51 shown in FIG. 6 and the shutter 52 is opened. Then, the laser light emitted from the laser oscillator 5 is transmitted to the cutting torch 2 by the laser light transmission device 6.
The transmitted laser light is condensed by the lens inside the cutting torch 2 shown in FIG. 6 and then irradiated on the surface of the control rod 1 to start cutting. For cutting, carry device 9 and rail 10
By moving upwards along.

The cutting speed is determined by the laser irradiation output of the laser oscillator 5. For example, when a YAG laser oscillator is used, since an optical fiber can be used for the laser light transmission device 6, laser light can be easily transmitted. When the output of the YAG laser oscillator is 4 kW at the maximum, it is possible to cut stainless steel with a thickness of 16 mm at a maximum speed of 0.4 m / min. Since the tie rod 31 of the control rod 1 currently used has a maximum thickness of 14 mm, the cutting speed, that is, the moving speed of the carrying device 9 is a maximum of 0.4 m / min.
The control rod 1 can be cut with the setting of.

Conventionally, in the plasma cutting disclosed in Japanese Patent Publication No. 3-49080 and the abrasive water jet disclosed in Japanese Patent Laid-Open No. 8-285996, the maximum cutting speed is 0.1 m / min.
Therefore, it is possible to cut at a maximum speed of about 4 times by using the present invention.

Further, since all the secondary product organisms generated during cutting can be recovered by the secondary product recovery devices 4 and 21, it is possible to prevent leakage of radioactive substances above the water surface. it can. Since the laser is locally heated, the temperature rise of water during cutting is extremely small and continuous cutting can be performed. Further, since the cutting width is narrower than that of the plasma cutting or the abrasive water jet described above, the amount of secondary products generated can be suppressed to be low.

After the cutting is completed, the shutter 52 of the cutting torch 2 shown in FIG. 6 is closed and the supply of the assist gas is stopped.
The control rod 1 cut in two around the axis is a restraint jig 3
Held by. For example, if the restraint jig 3 is provided with a moving means, the control rod 1 cut in two is put in the pool 23.
It can be transported to and housed in a control rod collection box (not shown) provided inside. Control rod 1 cut in two
By accommodating and accumulating them, the volume reduction efficiency can be improved. Since all the controls can be performed by the control system 8, it is possible to reduce the number of people who actually work, for example.

The second embodiment will be described with reference to FIGS. FIG. 8 shows a schematic side view of an underwater cutting device for a fuel channel box. Channel box 61
Is a square pipe, and is made of Zircaloy 4 having a thickness of about 3 mm. In the present embodiment, the channel box 61 is held by the restraining jig 65, which is vertically inserted by the driving device 66 and the cutting torch 62 is inserted into the inner surface from the upper portion of the channel box 61. The cutting torch 62 in the present embodiment has a laser oscillator 69 controlled by a control system 68, as shown in FIGS.

Two nozzles 67 for irradiating laser light are provided facing each other, and the laser light is supplied to each nozzle 67 by a reflection mirror 63. Since the transmittance of the laser light can be changed by using quartz as the material of the reflection mirror 63 and coating the surface, the laser light 72 emitted from the laser oscillator 5 should be emitted at two diagonal points at a time. You can

The cutting torch 62 can be extended in life by including a shutter, as described in the first embodiment. Further, even if such a structure is not adopted, it is possible to simultaneously cut two diagonal corners by providing two cutting torches 62 diagonally.

As for the cutting method, similar to the method described in the first embodiment, the cutting is performed by irradiating the laser beam while supplying the assist gas and moving the carrier device 9 along the rail 10. . Regarding the cutting speed, since the channel box 61 has a thin plate thickness of about 3 mm, for example, when a YAG laser oscillator with a maximum output of 4 kW is used,
It is possible to cut at a maximum cutting speed of 7 m / min, that is, the moving speed of the carrier device 9.

Channel box 61 cut in two
Are held by the restraint jig 65. For example, by providing the restraint jig 65 with a moving function, the cut channel box 61 is moved to a channel box collection box (not shown) and stored in a stack, so that the volume reduction efficiency can be improved. . Further, since all the controls are controlled by the control system 68 as in the first embodiment, the number of workers can be reduced also in the present embodiment.

[0046]

As described above, according to the present invention, when cutting radioactive solid waste such as used control rods and channel boxes, the cutting speed is fast and stable, and it is generated by cutting. It is possible to realize a system and method in which the amount of secondary waste is small and can be recovered.

[Brief description of drawings]

FIG. 1 is a schematic overall perspective view showing a first embodiment of a radioactive solid waste cutting system according to the present invention, showing a state in which a tie rod of a boiling water reactor control rod is cut in a vertical direction. FIG.

FIG. 2 is a schematic elevational view for explaining an operation when the speed limiter of the boiling water reactor control rod is horizontally cut by the system of FIG.

FIG. 3 is a schematic plan view of the system in the state of FIG.

FIG. 4 is a schematic elevational view of the system in the state of FIG.

5 is a schematic plan view of the system in the state of FIG. 1. FIG.

FIG. 6 is a schematic vertical cross-sectional view of the cutting torch of the system of FIG.

FIG. 7 is a schematic vertical sectional view of a secondary product recovery device of the system of FIG.

FIG. 8 is a schematic overall elevational view showing a second embodiment of the radioactive solid waste cutting system according to the present invention.

FIG. 9 is a view taken along the line IX-IX in FIG.

[Explanation of symbols]

1 ... Used control rod, 2 ... Cutting torch, 3 ... Restraint jig,
4 ... Secondary product recovery device, 5 ... Laser oscillator, 6 ... Laser light transmission device, 7 ... Driving device, 8 ... Control system, 9 ... Carrying device, 10 ... Rail, 12 ... Cutting torch, 13 ... Restraining jig , 14 ... Secondary product recovery device, 15 ... Rotation mechanism, 16
... Lower restraint jig, 21 ... Secondary product recovery device, 22 ... Separation film, 23 ... Pool (water), 31 ... Tie rod, 32 ... Lower blade, 33 ... Copying device, 34 ... Copying device, 35 ...
Fixing claw, 41 ... Collection port, 42 ... Collection box, 43
... Filter, 44 ... Suction device, 45 ... Discharge port, 46 ...
Cutting success / failure sensor, 51 ... Gas supply port, 52 ... Shutter, 53 ... Lens, 54 ... Laser light, 61 ... Channel box, 62 ... Cutting torch, 63 ... Reflection mirror, 64
... secondary product recovery device, 65 ... restraining jig, 66 ... drive device, 67 ... nozzle, 68 ... control system, 69 ... laser oscillator, 70 ... secondary product recovery device, 71 ... copying device, 72
… Laser light.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kenji Kurihara             8th Shinsugita Town, Isogo Ward, Yokohama City, Kanagawa Prefecture             Ceremony company Toshiba Yokohama office

Claims (10)

[Claims] 1. A radioactive solid waste cutting system for cutting radioactive solid waste in water as a cut object, comprising: a water tank for immersing the cut object in water; and the cut object in the water. Vertical moving means for vertically moving the object to be cut while holding the longitudinal direction of the object to be cut vertically, and arranged in the water to irradiate the underwater cutting part of the object to be cut with a laser beam. A cutting nozzle, a laser oscillator arranged outside the water tank, a transmitting means for transmitting a laser beam generated by the laser oscillator to the cutting nozzle, and a jetting assist gas from the tip of the cutting nozzle. Gas supply means, secondary product recovery means for recovering secondary products generated when the object is cut by the laser light in the water, the object to be cut in the water, Radioactive solid waste cutting system, wherein the open isolation film covering the entire cross-sectional nozzle, having, a. 2. The radioactive solid waste cutting system according to claim 1, further comprising horizontal moving means for moving the cutting nozzle in the horizontal direction to cut the object in the horizontal direction. Radioactive solid waste cutting system. 3. The radioactive solid waste cutting system according to claim 1, wherein the cutting nozzle prevents water from entering the cutting nozzle when the ejection of the assist gas is stopped. A radioactive solid waste cutting system, characterized in that it has a blocking means. 4. The radioactive solid waste cutting system according to claim 1, 2 or 3, further comprising a detector for detecting the success or failure of the cutting. 5. The radioactive solid waste cutting system according to claim 1, wherein the secondary product recovery means is the cutting nozzle opposite to the cutting nozzle when viewed from the object to be cut. The radioactive solid waste cutting system is characterized in that the radioactive solid waste cutting system is arranged at a position opposite to. 6. The radioactive solid waste cutting system according to claim 5, wherein the secondary product recovery means is also arranged above the isolation membrane. system. 7. The radioactive solid waste cutting system according to claim 1, wherein the cutting nozzle is fixed, and the vertical moving means moves the cutting object to cut the cutting object. A radioactive solid waste cutting system, characterized in that it is configured to be capable of. 8. The radioactive solid waste cutting system according to claim 1, wherein there are two cutting nozzles arranged in the water, and the laser light generated by the laser oscillator is supplied to the two cutting nozzles. A radioactive solid waste cutting system, characterized in that it has means for distributing to a cutting nozzle, and is configured to be able to simultaneously cut two points of the object to be cut while moving the object to be cut in the vertical direction. . 9. A radioactive solid waste cutting method for cutting radioactive solid waste in water as an object to be cut, wherein the object to be cut is vertically held in the water, and the object to be cut is held vertically. A cutting nozzle is arranged in the water in order to irradiate a laser beam to the underwater cutting part of the object, and an assist gas is ejected from the tip of the cutting nozzle, and a laser beam is generated by a laser oscillator arranged outside the water tank. Generated, the laser beam generated by the laser oscillator is transmitted to the cutting nozzle to irradiate the cutting portion with laser light, and the object to be cut is moved vertically in the water while irradiating the laser light, A method for cutting radioactive solid waste, comprising: collecting in the water a secondary product generated when the object to be cut is cut by the laser light. 10. The radioactive solid waste cutting method according to claim 9, wherein the assist gas is any one of air, nitrogen, and argon, or a mixture containing any of these. Waste cutting method.