JP4549269B2 - Pipe recycling method - Google Patents

Description

The present invention relates to a method for recycling pipes whose inner surface is contaminated with or possibly contaminated with radioactive substances, and is capable of easily measuring the state of contamination and decontamination.

  In a nuclear power plant such as a nuclear power plant, equipment such as a heat exchanger is replaced periodically or as necessary. In this case, the removed old equipment is finally discarded or recycled, but before that, it is necessary to measure the radioactive contamination state and to decontaminate the site where the contamination concentration is high.

  A large number of heat transfer tubes (fine tubes) are housed in the heat exchanger. When the heat exchanger is discarded or recycled, the contamination state is also measured on the inner surface of each heat transfer tube, and the contamination concentration is high. In some cases, it is necessary to perform decontamination treatment. However, since the heat transfer tubes of heat exchangers generally have a small inner diameter, it is often difficult to insert a sensor or a decontamination device for measuring radioactivity.

  Conventionally, techniques described in Patent Documents 1 and 2 below have been proposed as techniques for facilitating the measurement or decontamination of the inner surface of a pipe having a small inner diameter. This was made so that radioactivity measurement and decontamination could be easily performed by cutting the tube into two pieces with a cutter and exposing the inner surface.

Japanese Utility Model Publication No. 2-6977 (Fig. 3) Japanese Patent Laying-Open No. 2005-7483 (FIG. 1)

  According to the methods described in Patent Documents 1 and 2, a machine for vertically dividing a pipe having a circular cross section is required.

  The present invention solves the above-mentioned problems in the prior art, exposes the inner surface of the tube without requiring a machine for vertically dividing the tube having a circular cross section, and measures the contamination state of the inner surface of the tube. An object of the present invention is to provide a method capable of decontamination processing and further recycling.

In the method for measuring the contamination state of a pipe disclosed in the following embodiment , at least the inner surface of the pipe is contaminated with a radioactive substance, or a pipe that may be contaminated is pressed from the outer surface to be crushed, and the crushing is performed. The folded portion on both sides along the axis of the pipe is cut off, and the contamination state due to the radioactive substance is measured on at least the surface corresponding to the inner surface of the plate member of each of the upper and lower pieces.

The tube decontamination method disclosed in the following embodiment is a method in which at least an inner surface is pressed or crushed from the outer surface of a tube that is contaminated or possibly contaminated with a radioactive substance, and the crushed The folded portions on both sides along the axis of the pipe are cut off, and at least the surface corresponding to the inner surface of the remaining plate members of the upper and lower pieces is subjected to the decontamination treatment of the radioactive substance.

The tube contamination state measurement and decontamination method disclosed in the following embodiment is a method in which at least an inner surface is compressed with a radioactive material, or a tube that may be contaminated is pressed from the outer surface and crushed. The folded portion on both sides along the axis of the crushed tube is cut off, and at least the surface corresponding to the inner surface of the plate member of each of the upper and lower pieces is measured for contamination by radioactive material, and there is contamination. A radioactive material is decontaminated with respect to a thing or a degree of contamination exceeding a predetermined value.

  According to the pipe recycling method of the present invention, at least the inner surface is contaminated with radioactive material, and the tube which is possibly contaminated is pressurized and crushed from the outer surface, and the shaft of the crushed tube is Cut off the folded portions on both sides along the line, discard the folded folded portions as radioactive waste, and perform decontamination treatment of the radiation material on at least the surface corresponding to the inner surface of the plate members of the upper and lower pieces that remain. After being performed, the plate-like member is recycled.

  According to the pipe recycling method of the present invention, at least the inner surface is contaminated with radioactive material, and the tube which is possibly contaminated is pressurized and crushed from the outer surface, and the shaft of the crushed tube is Cut off the folded portions on both sides along the line, discard the folded folded portions as radioactive waste, and measure the contamination state due to radioactive material on at least the surface corresponding to the inner surface of the plate member of each of the upper and lower pieces After decontamination of radioactive materials for those that are not contaminated or whose degree of contamination is less than the prescribed tolerance, those that are contaminated or whose degree of contamination exceeds the prescribed tolerance It is designed to be recycled.

  According to this invention, at least the inner surface is contaminated with radioactive material, and a tube that is possibly contaminated is pressed from the outer surface to be crushed, and the crushed tube on both sides along the axis is crushed. Since the folded portion is cut off, it can be processed using an existing press or shearing machine, and a machine for vertically dividing a pipe having a circular cross section can be eliminated.

  Embodiments of the present invention will be described below. Here, the case where it processes about the heat exchanger tube accommodated in the heat exchanger which comprises the feed water heater of a nuclear power plant is demonstrated. FIG. 1 shows an example of a processing procedure according to the present invention. Each process up to decontamination is performed in the radiation control area in the nuclear power plant. Each process will be described in order.

[Step 1: Cut out part of straight pipe of heat transfer tube]
The heat transfer tube 10 is obtained by cutting a straight tube portion of a heat transfer tube accommodated in a heat exchanger constituting a feed water heater, and has a length of 10 to 20 m, an outer diameter of 10 to 20 mm, and a wall thickness. It consists of a copper alloy tube, stainless steel tube, etc. of about 1.2 mm. The heat transfer tube 10 may be contaminated with radioactivity. In particular, in the case of a BWR (boiling water reactor) type plant, water with radioactivity from the condenser flows in the heat transfer tubes of the feed water heater, and the radioactivity from the steam turbine flows outside the heat transfer tubes. Since tangled steam flows, the inner and outer surfaces of the heat transfer tube 10 are expected to be highly contaminated.

[Step 2: Cutting to a predetermined length]
The heat transfer tube 10 is cut into an appropriate length (for example, a length of several tens of cm to 1 m) that can be easily processed in a later step, and the cut heat transfer tubes 10-1, 10-2,. -N is obtained. Hereinafter, the process of the heat exchanger tube 10-1 is demonstrated. The other heat transfer tubes 10-2, 10-3, ..., 10-n are similarly processed.

[Process 3: Crushing]
The heat transfer tube 10-1 cut to a predetermined length is pressed and crushed from its outer surface using a press machine such as a press brake. An arrangement when the heat transfer tube 10-1 is crushed by a press brake is shown in FIG. A press brake is a press machine for pressing a long object. In the press brake 12, a table 16 is installed below the frame 14, and a ram 18 is installed above the frame 14 so as to be movable in the vertical direction. A lower mold 20 is mounted on the table 16, and an upper mold 22 is mounted on the lower end of the ram 18. The opposed processing surfaces 20a, 22a of the lower mold 20 and the upper mold 22 are both flat (horizontal). In addition, the processed surfaces 20a and 22a have such a size that the entire work piece (heat transfer tube 10-1) can be arranged in the region without protruding. The entire heat transfer tube 10-1 is placed on the processing surface 20 a of the lower die 20, the ram 18 is lowered, and the heat transfer tube 10-1 is pressurized from the outside by the lower die 20 and the upper die 22, whereby the heat transfer tube 10. Crush -1.

  The operation | movement which crushes the heat exchanger tube 10-1 using the press brake 12 of FIG. 2 is shown in FIG. (I) is the state before crushing. The entire heat transfer tube 10-1 is placed on the lower mold 20. When the upper die 22 is lowered by the ram 18 in this state, the entire heat transfer tube 10-1 is sandwiched between the lower die 20 and the upper die 22 and crushed into a flat plate shape as shown in (ii).

[Step 4: Cut off one folded portion]
In FIG. 1, one folded portion 10a along the axis of the crushed heat transfer tube 10-1 is cut using a shearing machine (shearing) and cut off. The cut-back folded portion 10a is discarded as a radioactive waste by a predetermined method.

  FIG. 4 shows an arrangement when the folded portion 10a is cut off with a shearing machine. In the shearing machine 24, a table 28 is installed at the lower part of the frame 26, and a ram 30 is installed at the upper part of the frame 26 so as to be movable in the vertical direction. A fixed blade 32 is mounted on the table 28, and a movable blade 34 is mounted on the lower end of the ram 30. The length (lateral length) of the fixed teeth 32 and the movable blade 34 is set to be longer than the length of the work (heat transfer tube 10-1). A work presser 36 is separately installed on the frame 26 so as to be movable in the vertical direction. One of the heat transfer tubes 10-1 is placed on the fixed blade 32 by placing the heat transfer tube 10-1 within its longitudinal range, pressing the heat transfer tube 10-1 with the work holder 36 and lowering the ram 30. The folded portion 10a can be cut and cut off.

  FIG. 5 shows an operation of cutting and cutting off one folded portion 10a of the heat transfer tube 10-1 using the shearing machine 24 of FIG. (I) is the state before cutting off. On the fixed blade 32, the heat transfer tube 10-1 is placed in a state where one folded portion 10a thereof protrudes from the edge 32a of the fixed blade 32 with a predetermined width d. Then, the work retainer 36 is lowered, and the heat transfer tube 10-1 is pressed onto the fixed blade 32 by the lower end portion 36a of the work retainer 36 so that the heat transfer tube 10-1 does not move. When the movable blade 34 is lowered by the ram 30 in this state, the folded portion 10a of the heat transfer tube 10-1 is cut by the cooperative action of the movable blade 34 and the fixed blade 32 as shown in (ii). .

[Step 5: Cutting off the other folded portion]
In FIG. 1, the member 10b left by cutting off one folded portion 10a of the heat transfer tube 10-1 is reversed, and the other folded portion 10c is used in the same manner as FIG. 5 using the shearing machine of FIG. Cut and cut off. The cut-back folded portion 10c is discarded as a radioactive waste by a predetermined method.

[Step 6: Separating the remaining members]
The portion 10d left after the above steps is separated into two flat members 10e and 10f.

[Step 7: Radioactivity measurement]
About each of flat member 10e, 10f, the radioactivity measurement of the both surfaces is performed by a well-known method.

[Step 8: Decontamination]
As a result of radioactivity measurement, if the contamination concentration is higher than the allowable value, decontamination is performed. The decontamination process can be performed by a known method such as grinding a contaminated surface with a brush or a grinder. After the decontamination process, the radioactivity measurement is performed again, and the decontamination process is repeated until it is confirmed that the radiation concentration is below the allowable value.

[Process 9: Recycling]
The plate-like members 10e and 10f whose radiation concentration is confirmed to be lower than the allowable value are taken out of the radiation control area and sent to the route for recycling.

  According to the above process, an existing press machine or shearing machine can be used, and a machine for vertically dividing a pipe having a circular cross section can be eliminated. In addition, since the plate-like members 10e and 10f are recycled, the amount discarded as radioactive waste can be reduced compared with the case where the entire heat transfer tube is discarded, and the disposal cost can be reduced and resource saving can be achieved. Can be achieved.

  Demonstration experiments were performed for step 1 to step 6 in FIG. The process of this demonstration experiment is shown in FIG. Here, as the pipe 10-1, as shown in FIG. 6 (i), a stainless steel pipe having an outer diameter of about 16 mm, a wall thickness of 1 mm, and a length of several tens of centimeters was used.

  A hydraulic press brake PHS-80-255 type manufactured by Komatsu was used as a press, and the tube 10-1 was pressed and crushed into a flat plate shape as shown in FIG. 6 (ii). At this time, the width of the crushed tube 10-1 was about 25 mm.

  Next, using a shearing SHS 6 × 255 type made by Komatsu as a shearing machine, as shown in FIG. 6 (iii), the folded portions 10a and 10c on both sides of the crushed tube 10-1 are cut into widths of about 2 mm, respectively. And cut off.

  As a result, as shown in FIG. 6 (iv), flat members 10e and 10f having a width of about 21 mm were obtained.

Other embodiments of the invention

  In the above embodiment, the decontamination process is not performed before crushing the tube. However, the outer peripheral surface of the tube may be decontaminated in advance by a method such as grinding with a brush or a grinder, and then crushed. If it does in this way, it can prevent that the radioactive substance adhering to the outer peripheral surface of a pipe | tube adheres to a press machine and a shearing machine in a subsequent crushing and cutting process. In addition, if possible, the decontamination process can be performed on the inner peripheral surface of the tube in advance before crushing the tube.

  In the above embodiment, the crushed tube is cut only in the vicinity of the folded portions on both sides in the width direction. However, if the width of the crushed tube is wide, the crushed tube is crushed as necessary. It is also possible to cut the intermediate portion in the width direction of the pipe together.

  In the above embodiment, the case where the heat transfer tube of the feed water heater is treated has been described. However, at least the inner surface is contaminated with a radioactive substance or may be contaminated with a heat exchanger other than the feed water heater. The present invention can also be applied to heat tubes and tubes other than heat transfer tubes.

It is process drawing which shows an example of the process sequence by this invention. It is a front view of a press brake which shows arrangement | positioning when crushing a heat exchanger tube with a press brake in the process 3 of FIG. It is a side view which shows the operation | movement which crushes a heat exchanger tube using the press brake of FIG. In the process 4 of FIG. 1, it is a front view of a shearing machine which shows arrangement | positioning when one folding part of a heat exchanger tube is cut off with a shearing machine. It is a side view which shows the operation | movement which cuts off one folding | turning part of a heat exchanger tube using the shearing machine of FIG. FIG. 2 is an end view of a pipe showing a process of a verification experiment performed for processes 1 to 6 in FIG. 1.

Explanation of symbols

  10 (10-1, 10-2,..., 10-n) ... pipe (heat transfer pipe), 10a, 10c ... folded portion, 10e, 10f ... plate-like member, 12 ... press machine (press brake), 24 ... shearing machine.

Claims (2)

  Pressing and crushing at least the inner surface of a tube that is contaminated or possibly contaminated with radioactive material from its outer surface, cutting off the folded portions on both sides along the axis of the crushed tube, The cut-back folded part is discarded as radioactive waste, and after decontamination treatment of the radiation material is performed on at least the surface corresponding to the inner surface of each of the upper and lower pieces of the plate member, the plate member is recycled. How to recycle pipes   Pressing and crushing at least the inner surface of a tube that is contaminated or possibly contaminated with radioactive material from its outer surface, cutting off the folded portions on both sides along the axis of the crushed tube, The cut-back folded part is discarded as radioactive waste, and at least the surface corresponding to the inner surface of each of the upper and lower pieces of the plate-like member is measured for the state of contamination by radioactive substances. A method of recycling pipes that recycles those that are less than or equal to a predetermined tolerance, and that reconstitutes after decontamination of radioactive material for those that are contaminated or whose contamination exceeds a predetermined tolerance.

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