JP2010122076A - Decontamination method and device of heat exchanger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress a generation amount of secondary waste by preventing excessive grinding during decontamination. <P>SOLUTION: This decontamination method of a heat exchanger for decontaminating the inside of a heat transfer tube of the heat exchanger includes: steps (step S51-step S53) for allowing a jet mixed with an abrasive to reach the second port from the first port of the heat transfer tube, and to flow to the inside of the heat transfer tube through a normal inflow circuit; and a step (step S55) for allowing the jet mixed with the abrasive to reach the first port from the second port of the heat transfer tube, and to flow to the inside of the heat transfer tube through a reverse inflow circuit, with elapse of a half of a set time required until the inner surface of the first port side and the inner surface of the second port side of the heat transfer tube reach a target grinding amount simultaneously by switching the second port side of the heat transfer tube from the downstream to the upstream of the jet (step S54: Yes). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a decontamination method and a decontamination apparatus for decontaminating heat transfer tubes of a heat exchanger, for example, in a heat exchanger that performs heat exchange of primary cooling water in a nuclear power plant.

  In a nuclear power generation facility that is a nuclear power plant, a steam generator (heat exchanger) for obtaining steam for driving a turbine connected to the generator is employed. In the steam generator, for example, a plurality of heat transfer tubes that are vertically U-shaped are arranged in a cylindrical body. The nuclear power generation facility has a circulation system in which the primary cooling water heated in the reactor is passed through the heat transfer tubes of the steam generator and returned to the reactor again. An inlet of secondary cooling water is provided in the middle of the body of the steam generator, and heat exchange with the secondary cooling water is performed while the primary cooling water flows through the heat transfer pipe. The steam generated by this heat exchange is discharged from the uppermost part of the trunk through a steam-water separator and a moisture separator arranged in the trunk and sent to the turbine. Further, in the nuclear power generation facility, a desalting tower is provided to remove impurities contained in the primary cooling water circulating in the circulation system. The primary cooling water desalination system supplies the primary cooling water taken out from the circulation system to the desalting tower via the regenerative heat exchanger and the non-regenerative heat exchanger. And the primary cooling water desalted in the desalting tower is returned to the circulation system again through the regenerative heat exchanger. Also in this desalination treatment system, the primary cooling water is heat-exchanged by the regenerative heat exchanger and the non-regenerative heat exchanger.

  In the above nuclear power plant, in the heat exchanger such as the steam generator, the regenerative heat exchanger, and the non-regenerative heat exchanger, the primary cooling water passes through the heat transfer tubes that perform heat exchange. Contaminated. When such a heat exchanger is replaced due to aging, etc., the inside of the heat transfer tube is decontaminated in order to reduce radiation irradiation to workers when disassembling the used heat exchanger. There is a need.

  2. Description of the Related Art Conventionally, a decontamination method and apparatus for decontaminating equipment that an operator approaches in advance when performing an inspection in a nuclear power generation facility are known. In such a decontamination method and apparatus, a jet mixed with an abrasive (a granular material such as glass, beads, metal, or ceramic) is made to collide with the surface of an object to be decontaminated (see, for example, Patent Document 1).

  That is, for example, when the inside of the heat transfer tube of the steam generator is decontaminated, it is conceivable that a jet mixed with an abrasive is passed through the heat transfer tube from the first port to the second port. .

JP-A 61-176895

  The heat transfer tube of the steam generator is a thin tube having an inner diameter of about 20 mm and has a total length of 20 m. And when a jet is made to flow in from the 1st opening | mouth of such a heat exchanger tube, at the beginning of inflow, it is difficult for an abrasive to get to the flow velocity of the air of a jet, and the speed of an abrasive is slow. Thereafter, as the jet proceeds toward the second mouth side of the heat transfer tube, the abrasive gradually gets on the flow velocity of the jet and the speed of the abrasive increases. For this reason, on the first mouth side (upstream side) of the heat transfer tube at the beginning of the inflow of the jet, the impact force of the abrasive on the inner surface of the heat transfer tube is weak, and from there toward the second mouth side (downstream side) Accordingly, since the impact force of the abrasive gradually increases, the grinding amount on the downstream side becomes larger than that on the upstream side. As a result, if grinding is performed so that the upstream side is decontaminated to the target, the downstream side exceeds the target and overgrinds, and a large amount of radioactive secondary waste is generated (see FIG. 8A).

  This invention solves the subject mentioned above, and it aims at providing the decontamination method and apparatus of a heat exchanger which can suppress overgrinding and can suppress the generation amount of a secondary waste.

  In order to achieve the above-mentioned object, in the heat exchanger decontamination method of the present invention, in the heat exchanger decontamination method for decontaminating the inside of the heat transfer tube of the heat exchanger, the jet mixed with the abrasive is the above-mentioned A step of flowing from the first port of the heat transfer tube to the second port and flowing into the inside of the heat transfer tube; and then, the second port side of the heat transfer tube is switched from the downstream side to the upstream side of the jet flow so that the heat transfer tube When half of the set time until the inner surface of the first mouth side and the inner surface of the second mouth side at the same time reach the target grinding amount has passed, the jet flow mixed with the abrasive is passed through the second heat transfer tube. And a step of flowing from the mouth to the first mouth and flowing into the heat transfer tube.

  According to this heat exchanger decontamination method, the upstream side and the downstream side of the jet are switched during the decontamination process, and this timing is switched from the downstream side of the jet to the upstream side of the second port of the heat transfer tube. Then, when the half of the set time until the inner surface of the first mouth side and the inner surface of the second mouth side of the heat transfer tube reach the target grinding amount has elapsed. For this reason, since the entire grinding amount from the first port to the second port of the heat transfer tube is decontaminated to the target grinding amount, over-grinding can be prevented and the amount of secondary waste generated can be suppressed.

  In addition, by switching the upstream side of the jet with a small amount of grinding to the downstream side with a large amount of grinding on the way, the grinding amount is averaged over the entire length of the heat transfer tube. Can be averaged.

  Moreover, the decontamination time can be shortened compared to the conventional decontamination time by switching the upstream side of the jet with a small grinding amount to the downstream side with a large grinding amount in the middle.

  Further, in the heat exchanger decontamination method of the present invention, when the jet mixed with the abrasive is flowing into the heat transfer tube, the abrasive recovered from the downstream side of the jet is recovered. And then returning the recovered abrasive to the upstream side of the jet.

  According to this heat exchanger decontamination method, the amount of secondary waste generated can be further suppressed by using the abrasive material from the downstream side of the jet again for decontamination.

  In order to achieve the above-described object, in the heat exchanger decontamination apparatus of the present invention, in the heat exchanger decontamination apparatus for decontaminating the inside of the heat transfer tube of the heat exchanger, the jet mixed with the abrasive material A positive inflow circuit that leads from the first port of the heat transfer tube to the second port and flows into the heat transfer tube, and the jet mixed with the abrasive from the second port of the heat transfer tube to the first port A reverse inflow circuit that flows into the heat transfer tube, a switching unit that selectively switches to the forward inflow circuit or the reverse inflow circuit, and the second port side of the heat transfer tube is switched from downstream to upstream of the jet flow. The preset time until the inner surface on the first mouth side and the inner surface on the second mouth side of the heat transfer tube reach the target grinding amount at the same time is stored in advance, and the switching unit is selected as the positive inflow circuit. When half of the set time has elapsed, the switching unit is switched to the reverse inflow circuit. And control means that, characterized by comprising a.

  According to this heat exchanger decontamination apparatus, the decontamination method can be carried out, and over-grinding can be prevented and the amount of secondary waste generated can be suppressed. Moreover, the grinding amount is averaged over the entire length of the heat transfer tube, and the decontamination effect over the entire length of the heat transfer tube can be averaged. Moreover, the decontamination time can be shortened as compared with the conventional decontamination time.

  Further, in the heat exchanger decontamination apparatus of the present invention, the polishing material that is provided in common to the forward inflow circuit and the reverse inflow circuit is recovered from the downstream side of the jet, and the recovered A polishing material circulating means for returning the polishing material to the upstream side of the jet is provided.

  According to this heat exchanger decontamination apparatus, the amount of secondary waste generated can be further suppressed by using the abrasive material from the downstream side of the jet again for decontamination.

  According to the present invention, overgrinding can be prevented and the amount of secondary waste generated can be suppressed. Moreover, the grinding amount is averaged over the entire length of the heat transfer tube, and the decontamination effect over the entire length of the heat transfer tube can be averaged. Moreover, the decontamination time can be shortened as compared with the conventional decontamination time.

  Embodiments of a heat exchanger decontamination method and apparatus according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In addition, constituent elements in the following embodiments include those that can be easily replaced by those skilled in the art or those that are substantially the same.

  FIG. 1 is a schematic diagram of a nuclear power plant to which a heat exchanger decontamination method and apparatus according to an embodiment of the present invention is applied. In the present embodiment, the nuclear power plant 1 is a nuclear power generation facility, and the nuclear reactor 2 is a PWR (Pressurized Water Reactor).

  In the nuclear power plant 1, a nuclear reactor 2, a steam generator 3, a pressurizer 4, a primary cooling water pump 5, and a regenerative heat exchanger 11 are arranged in a containment vessel 1W. Moreover, the turbine 8, the condenser 9, and the generator 10 are arrange | positioned outside the storage container 1W. In the nuclear reactor 2, nuclear fuel 2C is arranged inside the pressure vessel. Further, the inside of the pressure vessel is filled with primary cooling water (for example, light water) C1. The primary cooling water pump 5 and the nuclear reactor 2 are connected by a primary cooling water first supply passage 6A. Further, the nuclear reactor 2 and the steam generator 3 are connected by a primary cooling water second supply passage 6B. Further, the steam generator 3 and the primary cooling water pump 5 are connected by a primary cooling water recovery passage 6C.

  With such a configuration, the primary cooling water C1 discharged from the primary cooling water pump 5 is supplied into the pressure vessel of the nuclear reactor 2 through the primary cooling water first supply passage 6A. And the primary cooling water C1 is heated with the thermal energy which generate | occur | produced by the fission reaction of the nuclear fuel 2C arrange | positioned inside a pressure vessel. The heated primary cooling water C1 is supplied to the steam generator 3 through the primary cooling water second supply passage 6B. The primary cooling water C1 passes through the heat transfer pipe 304 of the steam generator 3, and then flows out of the steam generator 3, returns to the primary cooling water pump 5 through the primary cooling water recovery passage 6C, and again returns to the primary cooling water. It is discharged into the pressure vessel of the reactor 2 from the first supply passage 6A.

  The steam generator 3 includes a plurality of heat transfer tubes 304. The secondary cooling water C2 outside the heat transfer tubes 304 is heated and boiled by the primary cooling water C1 flowing through the heat transfer tubes 304, and the high temperature of the secondary cooling water C2 is reached. High pressure steam is generated. The steam generator 3 and the turbine 8 are connected by a steam supply passage 7S, and the condenser 9 and the steam generator 3 are connected by a secondary cooling water recovery passage 7R. As a result, the high-temperature and high-pressure steam of the secondary cooling water C2 generated by the steam generator 3 is supplied to the turbine 8 through the steam supply passage 7S and drives it. Then, electric power is generated by the generator 10 connected to the drive shaft of the turbine 8. The secondary cooling water C2 after driving the turbine 8 becomes liquid in the condenser 9, and is sent to the steam generator 3 again through the secondary cooling water recovery passage 7R.

  The nuclear reactor 2 is a pressurized water nuclear reactor, and the pressurizer 4 is connected to the primary cooling water second supply passage 6B. The pressurizer 4 applies pressure to the primary cooling water C1 in the primary cooling water second supply passage 6B. With such a structure, the primary cooling water C1 does not boil even when heated by the thermal energy generated by the nuclear fission reaction of the nuclear fuel 2C, and circulates in the reactor 2 and its cooling system in a liquid phase. Here, the cooling system of the nuclear reactor 2 includes a primary cooling water pump 5, a primary cooling water first supply passage 6A, a primary cooling water second supply passage 6B, a steam generator 3, and a primary cooling water recovery passage 6C. This is a system through which the cooling water C1 flows.

  Moreover, in the nuclear power plant 1, in order to remove impurities contained in the primary cooling water C1, a desalting tower 16 is provided. The desalting tower 16 includes a first desalting tower 16A and a second desalting tower 16B, and is disposed outside the storage container 1W. The first desalting tower 16A is a cooling water hot bed desalting tower, and the second desalting tower 16B is a cooling water cation desalting tower. The primary cooling water C1 taken from the inlet side (upstream side) of the primary cooling water pump 5 is supplied from the cooling system of the nuclear reactor 2 to the desalting tower 16 to be subjected to a desalting treatment, and the primary after the desalting is performed. The cooling water C1 is returned to the outlet side (downstream side) of the primary cooling water pump 5.

  The demineralization treatment system for the primary cooling water C1 includes a primary cooling water extraction passage 13A, a regenerative heat exchanger 11, a primary cooling water passage 13B, a non-regenerative heat exchanger 12, a primary cooling water passage 13C, a desalting tower 16, and a primary cooling. It is composed of a water passage 13D, a volume control tank 14, and primary cooling water return passages 13E and 13F. The primary cooling water recovery passage 6C and the regenerative heat exchanger 11 constituting the cooling system of the nuclear reactor 2 are connected by a first cooling water extraction passage 13A. The regenerative heat exchanger 11 and the non-regenerative heat exchanger 12 are connected by a primary cooling water passage 13B. The non-regenerative heat exchanger 12 and the desalting tower 16 are connected by a primary cooling water passage 13C. The desalting tower 16 and the volume control tank 14 are connected by a primary cooling water passage 13D. The volume control tank 14 and the regenerative heat exchanger 11 are connected by a primary cooling water return passage 13E. The regenerative heat exchanger 11 and the primary cooling water first supply passage 6A are connected by a primary cooling water return passage 13F. A filling pump 15 is provided in the primary cooling water return passage 13E.

  The primary cooling water C1 is taken out from the primary cooling water take-out passage 13A, that is, the inlet side (upstream side) of the primary cooling water pump 5. The primary cooling water C1 taken out from the cooling system of the reactor 2 is guided to the regenerative heat exchanger 11, and then desalted through the primary cooling water passage 13B, the non-regenerative heat exchanger 12, and the primary cooling water passage 13C. It is led to the tower 16 where it is desalted. The desalted primary cooling water C1 is temporarily stored in the volume control tank 14 through the primary cooling water passage 13D, and then regenerated heat exchanger 11 by the filling pump 15 provided in the primary cooling water return passage 13E. Sent to. The primary cooling water C1 that has passed through the regenerative heat exchanger 11 is returned to the primary cooling water first supply passage 6A, that is, the outlet side (downstream side) of the primary cooling water pump 5 through the primary cooling water return passage 13F.

  In the present embodiment, the heat exchanger to which the decontamination method and the decontamination apparatus are applied is the steam generator 3 through which the primary cooling water C1 filled in the pressure vessel of the nuclear reactor 2 passes, the regenerative heat exchange. A regenerator 11 and a non-regenerative heat exchanger 12. In the present embodiment, the steam generator 3 will be described as a main target. FIG. 2 is a schematic diagram of a steam generator (heat exchanger) according to an embodiment of the present invention.

  As shown in FIG. 2, the steam generator 3 has a hollow cylindrical shape that extends in the up-down direction and is hermetically sealed, and has a trunk portion 301 whose lower half is slightly smaller in diameter than the upper half. is doing. In the lower half of the body portion 301, a tube group outer tube 302 having a cylindrical shape is provided that is disposed at a predetermined distance from the inner wall surface of the body portion 301. The lower end portion of the tube group outer tube 302 extends to the tube plate 303 disposed below in the lower half of the body portion 301. Inside the tube group outer tube 302, a heat transfer tube group 304A comprising a plurality of heat transfer tubes 304 having an inverted U shape is provided. Each of the heat transfer tubes 304 is arranged with the U-shaped arc portion facing upward, an end portion facing downward is supported by the tube plate 303, and an intermediate portion is supported by a plurality of tube support plates 305. . A large number of through holes (not shown) are formed in the tube support plate 305, and the heat transfer tubes 304 are passed through the through holes in a non-contact state.

  A water chamber 306 is provided at the lower end of the body 301. The water chamber 306 is divided into an entrance chamber 306A and an exit chamber 306B by a partition wall 307. A first port 304a of each heat transfer tube 304 is communicated with the entrance chamber 306A, and a second port 304b of each heat transfer tube 304 is communicated with the exit chamber 306B. In addition, an inlet nozzle 306AA that communicates with the outside of the trunk portion 301 is formed in the entrance chamber 306A, and an outlet nozzle 306BB that communicates with the exterior of the trunk portion 301 is formed in the exit chamber 306B. The inlet nozzle 306AA is connected to the primary cooling water second supply passage 6B through which the primary cooling water C1 is sent from the reactor 2, while the outlet nozzle 306BB receives the primary cooling water C1 after heat exchange. A primary cooling water recovery passage 6C to be sent to the nuclear reactor 2 is connected.

  In the upper half of the body 301, there are an air / water separator 308 that separates the feed water into steam and hot water, and a moisture separator 309 that removes the moisture from the separated steam and makes it close to dry steam. Is provided. Between the steam separator 308 and the heat transfer tube group 304A, a water supply pipe 310 for supplying the secondary cooling water C2 from the outside into the body 301 is inserted. Further, a steam discharge port 311 is formed at the upper end of the body 301. Further, in the lower half portion of the body portion 301, the secondary cooling water C2 supplied into the body portion 301 from the water supply pipe 310 is caused to flow down between the body portion 301 and the tube group outer tube 302 so as to be a tube sheet. A water supply passage 312 is provided that is folded back at 303 and is raised along the heat transfer tube group 304A. A steam supply passage 7S for sending steam to the turbine 8 is connected to the steam discharge port 311, and secondary cooling water C <b> 2 in which the steam used in the turbine 8 is cooled by the condenser 9 is connected to the water supply pipe 310. Is connected to the secondary cooling water recovery passage 7R.

  In such a steam generator 3, the primary cooling water C1 heated in the nuclear reactor 2 is sent to the entrance chamber 306A, circulates through the numerous heat transfer tubes 304, and reaches the exit chamber 306B. On the other hand, the secondary cooling water C2 cooled by the condenser 9 is sent to the water supply pipe 310 and rises along the heat transfer pipe group 304A through the water supply path 312 in the trunk portion 301. At this time, heat exchange is performed between the high-pressure and high-temperature primary cooling water C1 and the secondary cooling water C2 in the body portion 301. Then, the cooled primary cooling water C1 is returned to the reactor 2 from the exit chamber 306B. On the other hand, the secondary cooling water C2 that has exchanged heat with the high-pressure and high-temperature primary cooling water C1 rises in the body 301 and is separated into steam and hot water by the steam / water separator 308. The separated steam is sent to the turbine 8 after the moisture is removed by the moisture separator 309.

  In the steam generator 3, the heat transfer tube group 304 </ b> A composed of a plurality of heat transfer tubes 304 is formed in a hemispherical shape with an inverted U-shaped arc portion of the heat transfer tube 304 at its upper end. Specifically, in the center portion of the heat transfer tube group 304A, a heat transfer tube 304 having the smallest curvature is arranged, and the heat transfer tubes 304 having a larger curvature in the arc portion are sequentially arranged toward the outside of the hemisphere. And the upper end part of 304 A of heat exchanger tube groups is formed in a hemispherical shape by reducing the outer side heat exchanger tube 304 in order, overlapping this arranged thing.

  As described above, in the steam generator 3, the primary cooling water C <b> 1 passes through the heat transfer tube 304 that performs heat exchange, so that the inner surface of the heat transfer tube 304 is contaminated by radiation. When such a steam generator 3 is replaced due to aging or the like, the inside of the heat transfer tube 304 is removed in order to prevent radiation to workers when disassembling the used steam generator 3. It is necessary to dye.

  Hereinafter, the decontamination apparatus according to the present embodiment will be described. FIG. 3 is a schematic perspective view of a heat exchanger decontamination apparatus according to an embodiment of the present invention, and FIGS. 4 and 5 are schematic views of a heat exchanger decontamination apparatus according to an embodiment of the present invention. is there. The decontamination apparatus 100 includes a normal inflow circuit 101, a reverse inflow circuit 102, an abrasive circulation unit 103, a circuit connection unit 104, and a control unit 105.

  As shown by the solid line arrow in FIG. 4, the positive inflow circuit 101 causes the jet mixed with the abrasive material from the first port 304 a of the heat transfer tube 304 to the second port 304 b to flow into the heat transfer tube 304. Is. The positive inflow circuit 101 includes a compressor 106, a supply passage 107, an abrasive supply unit 108, a switching unit 109, a first supply recovery passage 110, a second supply recovery passage 111, a recovery passage 112, and a recovery separation portion 113. ing.

  The compressor 106 compresses air into a high pressure state. The air compressed by the compressor 106 is sent out as a jet through a supply passage 107 connected to the compressor 106. In the middle of the supply passage 107, an abrasive supply unit 108 is interposed. The abrasive supply unit 108 is configured as a hopper, for example, and supplies a predetermined amount of abrasive to the supply passage 107 and mixes it with the jet. As the abrasive, granular materials such as ceramics and metals (stainless steel, iron, etc.) are used, and the particle size is about 0.1 to 0.3 mm in diameter. The supply passage 107 is connected to the first supply / recovery passage 110 through the switching unit 109. The switching unit 109 will be described later. The first supply / recovery passage 110 is connected to the first port 304 a of the heat transfer tube 304. The second supply / recovery passage 111 is connected to the second port 304 b of the heat transfer tube 304. The second supply / recovery passage 111 is connected to the recovery passage 112 via the switching unit 109. The collection passage 112 is connected to the collection separation unit 113. A jet flowing through the heat transfer tube 304 passes through the recovery passage 112. The recovery / separation unit 113 recovers the abrasive mixed in the jet passing through the recovery passage 112 and the secondary waste ground by the abrasive and separates them. The separated secondary waste is stored in the collection / separation unit 113, and the separated abrasive is returned to the abrasive supply unit 108. Further, the jet after the abrasive and secondary waste are recovered is exhausted from the recovery / separation unit 113 through a blower (not shown).

  That is, the positive inflow circuit 101 converts the jet of air compressed by the compressor 106 into the supply passage 107 → the switching portion 109 → the first supply / recovery passage 110 → the heat transfer pipe 304 → the second supply / recovery passage 111 → the switching portion 109 →. By sending the recovery passage 112 in the order of the recovery / separation unit 113, the jet mixed with the abrasive in the abrasive supply unit 108 reaches the second port 304 b from the first port 304 a of the heat transfer tube 304 to the heat transfer tube 304. Let it flow inside.

  As shown by the one-dot chain line arrow in FIG. 4, the reverse inflow circuit 102 flows the jet mixed with the abrasive from the second port 304 b of the heat transfer tube 304 to the first port 304 a and flows into the heat transfer tube 304. It is something to be made. Similarly to the normal inflow circuit 101, the reverse inflow circuit 102 includes a compressor 106, a supply passage 107, an abrasive supply unit 108, a switching unit 109, a first supply recovery passage 110, a second supply recovery passage 111, a recovery passage 112, And a recovery / separation unit 113.

  Here, the switching unit 109 connects the supply passage 107 to the first supply / recovery passage 110 and connects the recovery passage 112 to the second supply / recovery passage 111, while connecting the supply passage 107 to the second supply / recovery passage 111. At the same time, the recovery passage 112 is selectively switched to connect to the first supply recovery passage 110. A circuit in which the supply passage 107 is connected to the first supply / recovery passage 110 and the recovery passage 112 is connected to the second supply / recovery passage 111 by the switching unit 109 is the positive inflow circuit 101. On the other hand, the reverse inflow circuit 102 is a circuit in which the supply passage 107 is connected to the second supply / recovery passage 111 and the recovery passage 112 is connected to the first supply / recovery passage 110 by the switching unit 109.

  That is, the reverse inflow circuit 102 converts the jet of air compressed by the compressor 106 into the supply passage 107 → the switching portion 109 → the second supply / recovery passage 111 → the heat transfer pipe 304 → the first supply / recovery passage 110 → the switching portion 109 →. By sending the recovery passage 112 in the order of the recovery separation unit 113, the jet mixed with the abrasive in the abrasive supply unit 108 reaches the first port 304 a from the second port 304 b of the heat transfer tube 304 and reaches the first port 304 a of the heat transfer tube 304. Let it flow inside.

  The abrasive material circulation means 103 includes the above-described abrasive material supply unit 108 and recovery / separation unit 113. As described above, the abrasive supply unit 108 supplies a predetermined amount of abrasive to the supply passage 107 and mixes it with the jet. The recovery / separation unit 113 recovers and separates the abrasive and the secondary waste mixed in the jet passing through the recovery passage 112 and stores the secondary waste while supplying the abrasive to the abrasive. Return to section. That is, the abrasive material circulation means 103 is provided in common to the forward inflow circuit 101 and the reverse inflow circuit 102, collects the abrasive material that has flowed out from the downstream side of the jet flow, and uses the recovered abrasive material to the upstream side of the jet flow. In this case, the abrasive is circulated and used.

  Note that the abrasive circulation means 103 may not be provided. In this case, as shown in FIG. 5, instead of the recovery separation unit 113, a recovery unit 120 that recovers and stores the abrasive and secondary waste mixed in the jet passing through the recovery passage 112 is provided in the recovery passage 112. Provide.

  As shown in FIG. 3, the circuit connecting means 104 is installed in each of the entrance chamber 306 </ b> A and the exit chamber 306 </ b> B of the steam generator 3. , 102 are connected to the first supply / recovery passage 110 and the second supply / recovery passage 111. The circuit connection means 104 has a connection nozzle 114.

  The connection nozzle 114 forms a connection part that connects the first supply / recovery passage 110 and the second supply / recovery passage 111 to the mouth of the heat transfer tube 304. The connection nozzle 114 may be configured to connect the first supply / recovery passage 110 and the second supply / recovery passage 111 one-to-one to a single heat transfer tube 304, but the first supply / recovery passage may be connected to a plurality of heat transfer tubes 304. 110 and the second supply / recovery passage 111 are preferably connected in a one-to-one manner in order to improve the decontamination work efficiency. The connection nozzle 114 is provided on a support member (not shown) disposed in the entrance chamber 306A and the exit chamber 306B, and is connected to or disconnected from the opening of the heat transfer tube 304 by an actuator (not shown), for example. .

  The control means 105 is constituted by a microcomputer or the like. The control means 105 is provided with a storage unit 105a and a timer unit 105b. The storage unit 105a includes a RAM, a ROM, and the like, and stores programs and data. The time measuring unit 105b measures time. The control unit 105 comprehensively controls the compressor 106, the switching unit 109, and the circuit connection unit 104 described above according to programs and data stored in advance in the storage unit 105a and time data from the time measuring unit 105b.

  The programs and data stored in the storage unit 105 a are for driving the compressor 106, the switching unit 109, and the circuit connection unit 104. In particular, in the storage unit 105 a, the second port 304 b of the heat transfer tube 304 is switched from the downstream side to the upstream side of the jet flow by switching between the forward inflow circuit 101 and the reverse inflow circuit 102 by the switching unit 109. Data of a set time until the inner surface on the first port 304a side and the inner surface on the second port 304b side simultaneously reach the target grinding amount is stored in advance. This set time is obtained from the result of an experiment conducted in advance, and the length of the heat transfer tube 304, the inner diameter of the heat transfer tube 304, the curvature of the arc portion of the heat transfer tube 304, the flow velocity of the jet, and the type of abrasive, It depends on the particle size. The set time is input to the control means 105 by an external input means (not shown) such as a keyboard or a mouse.

  The decontamination method, which is the operation of the decontamination apparatus 100 described above, will be described with reference to the flowcharts of FIGS.

  In the present embodiment, when the heat exchanger is replaced due to aging, etc., work to decontaminate the inside of the heat transfer tube in order to prevent radiation irradiation to workers when dismantling the used heat exchanger A decontamination apparatus and a decontamination method are applied.

  When performing the decontamination work, as shown in the flowchart of the decontamination work in FIG. 6, first, the green house 118 (see FIG. 3) is installed so as to cover the water chamber 306 side of the used steam generator 3 (see FIG. 3). Step S1). Thereby, the periphery of the water chamber 306 is isolated to prevent radiation from being scattered.

  Next, the decontamination apparatus 100 outside the steam generator 3 is prepared (step S2). That is, the decontamination apparatus 100 described above is installed outside the green house 118. Specifically, the supply passage 107 is connected to the compressor 106, the abrasive supply unit 108 is connected to the supply passage 107, and the supply passage 107 is connected to the switching unit 109. In addition, the recovery passage 112 is connected to the recovery separation unit 113 and the recovery passage 112 is connected to the switching unit 109. Further, the first supply recovery passage 110 and the second supply recovery passage 111 are connected to the switching unit 109.

  Next, the manhole in the water chamber 306 of the steam generator 3 is opened, and the inlet nozzle 306AA in the entrance chamber 306A and the exit nozzle 306BB in the exit chamber 306B are opened (step S3).

  Next, the decontamination apparatus 100 inside the steam generator 3 is prepared (step S4). That is, the circuit connecting means 104 is installed in the entrance room 306A and the exit room 306B. At this time, the worker wears radiation protective clothing to prevent exposure to radiation.

  Next, decontamination is performed (step S5). In this step S5, the decontamination apparatus 100 of this Embodiment is operated and the decontamination method is applied.

  Finally, with the completion of decontamination, the decontamination apparatus 100 is removed (step S6). After step S6, since the inside of the heat transfer tube 304 is decontaminated, the steam generator 3 can be disassembled.

  In the operation (decontamination method) of the decontamination apparatus 100 in step S5, as shown in the flowchart of the operation (decontamination method) of the decontamination apparatus according to the embodiment of the present invention in FIG. The circuit connecting means 104 connects the first supply / recovery passage 110 to the first port 304a of the desired heat transfer tube 304 and the second supply / recovery passage 111 to the second port 304b of the desired heat transfer tube 304 (step). S51). At the same time, the control means 105 switches the switching unit 109 so as to form the positive inflow circuit 101 (step S52). Next, the control means 105 operates the compressor 106 (step S53). Thereby, in the positive inflow circuit 101, the jet mixed with the abrasive reaches the second port 304b from the first port 304a of the heat transfer tube 304 and flows into the heat transfer tube 304, and the inside of the heat transfer tube 304 is Decontaminated.

  Next, the second port 304b of the heat transfer tube 304 is switched from the downstream side to the upstream side of the jet flow by the switching of the forward inflow circuit 101 and the reverse inflow circuit 102 by the switching unit 109, whereby the first port 304a side of the heat transfer tube 304 is switched. When the half of the set time until the inner surface of the second and the inner surface on the second port 304b side simultaneously reaches the target grinding amount has elapsed (step S54: Yes), the control means 105 switches the switching unit 109 to the reverse inflow circuit 102. (Step S55). As a result, in the reverse inflow circuit 102, the jet mixed with the abrasive reaches the first port 304a from the second port 304b of the heat transfer tube 304 and flows into the heat transfer tube 304, and continues to the inside of the heat transfer tube 304. Is decontaminated.

  Finally, when the remaining half of the set time has elapsed (step S56: Yes), the control means 105 stops the compressor 106 (step S57). Thereby, decontamination is completed.

  In steps S51 to S57, the circuit connection means 104 passes the first supply recovery passage 110 and the second supply recovery passage 111 to the next heat transfer tube 304 until the decontamination of all the heat transfer tubes 304 of the steam generator 3 is completed. Repeat while connecting to

  As described above, in the decontamination method according to the present embodiment, the step of causing the jet mixed with the abrasive to flow from the first port 304a of the heat transfer tube 304 to the second port 304b and to flow into the heat transfer tube 304; Next, the second port 304b side of the heat transfer tube 304 is switched from the downstream side to the upstream side of the jet flow, so that the inner surface of the heat transfer tube 304 on the first port 304a side and the inner surface on the second port 304b side are simultaneously targeted grinding amounts. And a step of causing the jet mixed with the abrasive material to flow from the second port 304b of the heat transfer tube 304 to the first port 304a and to flow into the heat transfer tube 304 when half of the set time has elapsed. .

  That is, as shown in FIG. 8A, conventionally, in the entire grinding process, the jet mixed with the abrasive material reaches the second port 304b from the first port 304a of the heat transfer tube 304, and the inside of the heat transfer tube 304. Since the decontamination is performed until the upstream side of the injection (the first port 304a side of the heat transfer tube 304) reaches the target grinding amount, the downstream side of the injection (the second port 304b side of the heat transfer tube 304) ) Was overgrinded and a large amount of secondary waste was generated.

  On the other hand, as shown in FIG. 8B, in the decontamination method of the present embodiment, in the entire grinding process, a jet mixed with an abrasive material in the middle is sent from the second port 304b of the heat transfer tube 304 to the first. The second port 304b side of the heat transfer tube 304 is switched from the downstream side to the upstream side of the jet flow so that the first port of the heat transfer tube 304 is switched. It is assumed that half of the set time until the inner surface on the 304a side and the inner surface on the second port 304b side simultaneously reach the target grinding amount has elapsed. For this reason, since the entire grinding amount from the first port 304a to the second port 304b of the heat transfer tube 304 is decontaminated to the target grinding amount, overgrinding is prevented and the amount of secondary waste generated is reduced. It becomes possible to suppress.

  In addition, since the upstream side of the jet with a small grinding amount is switched to the downstream side with a large grinding amount on the way, the grinding amount is averaged over the entire length of the heat transfer tube 304. Therefore, decontamination over the entire length of the heat transfer tube 304 is achieved. The effect can be averaged. In particular, the heat transfer tube 304 of the steam generator 3 has an arcuate portion formed in an inverted U shape, and there is a concern about overgrinding due to the large impact force of the abrasive at the bend of the arc portion. According to the grinding method of the present embodiment, it is possible to average the search amount in the arc portion and average the decontamination effect.

  Moreover, the decontamination time can be shortened compared to the conventional decontamination time by switching the upstream side of the jet with a small grinding amount to the downstream side with a large grinding amount in the middle.

  Further, in the decontamination method of the present embodiment, when the jet mixed with the abrasive is caused to flow into the heat transfer pipe 304, the step of recovering the abrasive that has come out from the downstream side of the jet, Returning the recovered abrasive to the upstream side of the jet.

  According to this decontamination method, it is possible to further reduce the amount of secondary waste generated by using the abrasive material that has come out from the downstream side of the jet for decontamination again.

  Further, in the decontamination apparatus 100 according to the present embodiment described above, the jet flow mixed with the abrasive material reaches the second port 304b from the first port 304a of the heat transfer tube 304 and flows into the heat transfer tube 304. The inflow circuit 101, the reverse inflow circuit 102 that causes the jet mixed with the abrasive material from the second port 304b of the heat transfer tube 304 to the first port 304a to flow into the heat transfer tube 304, and the forward inflow circuit 101 or the reverse flow The switching unit 109 that selectively switches to the inlet circuit 102, and the inner surface and the second port on the first port 304a side of the heat transfer tube 304 by switching the second port 304b side of the heat transfer tube 304 from downstream to upstream. When the set time until the inner surface on the side of 304b reaches the target grinding amount at the same time is stored in advance and half of the set time has elapsed since the switching unit 109 was selected as the normal inflow circuit 101, the reverse inflow circuit And a control unit 105 for switching the switching portion 109 to 02.

  According to this decontamination apparatus 100, the said decontamination method can be implemented, and it becomes possible to prevent overgrinding and to suppress the generation amount of secondary waste. Moreover, the grinding amount is averaged over the entire length of the heat transfer tube 304, and the decontamination effect over the entire length of the heat transfer tube 304 can be averaged. In addition, the decontamination time can be shortened as compared with the conventional decontamination time.

  Moreover, the decontamination apparatus 100 of this Embodiment is equipped with the abrasive | polishing material circulation means which collect | recovers the abrasives which came out from the downstream of a jet, and returns this collect | recovered abrasive to the upstream of a jet.

  According to such a configuration, it is possible to further suppress the amount of secondary waste generated by using the abrasive that has come out from the downstream side of the jet for decontamination again.

  In addition, the decontamination apparatus 100 according to the present embodiment includes a circuit connection unit 104 in which a plurality of heat transfer tubes 304 are arranged and the circuits 101 and 102 are connected to the mouths of the selected heat transfer tubes 304.

  In the steam generator 3, more than about 3000 heat transfer tubes 304 are arranged, and each port is doubled and the work is performed inside the water chamber 306. It is not easy to connect the circuits 101 and 102 to each other. According to this configuration, it becomes easy to connect the circuits 101 and 102 to the mouth of the heat transfer tube 304.

  As described above, the heat exchanger decontamination method and the decontamination apparatus according to the present invention are suitable for preventing over-grinding and suppressing the generation amount of secondary waste.

It is the schematic of the nuclear power plant to which the decontamination method and apparatus of the heat exchanger concerning embodiment of this invention are applied. It is the schematic of the steam generator (heat exchanger) concerning embodiment of invention. It is a schematic perspective view of the decontamination apparatus of the heat exchanger concerning embodiment of this invention. It is the schematic of the decontamination apparatus of the heat exchanger concerning embodiment of this invention. It is the schematic of the decontamination apparatus of the heat exchanger concerning embodiment of this invention. It is a flowchart of decontamination work. It is a flowchart of operation | movement (decontamination method) of the decontamination apparatus concerning embodiment of this invention. It is a figure which shows the relationship of the grinding amount-grinding time which compares the past and this invention.

Explanation of symbols

1 Nuclear power plant (nuclear power generation equipment)
3 Steam generator (heat exchanger)
DESCRIPTION OF SYMBOLS 11 Regenerative heat exchanger 12 Non-regenerative heat exchanger 100 Decontamination apparatus 101 Forward inflow circuit 102 Reverse inflow circuit 103 Abrasive material circulation means 104 Circuit connection means 105 Control means 105a Storage part 105b Timekeeping part 106 Compressor 107 Supply path 108 Abrasive Supply portion 109 Switching portion 110 First supply / recovery passage 111 Second supply / recovery passage 112 Recovery passage 113 Recovery / separation portion 114 Connection nozzle 118 Greenhouse 120 Recovery portion 301 Body portion 302 Tube group outer tube 303 Tube plate 304 Heat transfer tube 304a First 304b Second port 304A Heat transfer tube group 305 Tube support plate 306 Water chamber 306A Inlet chamber 306AA Inlet nozzle 306B Outlet chamber 306BB Outlet nozzle 307 Bulkhead 308 Air / water separator 309 Moisture separator 310 Water supply pipe 311 Steam outlet 312 Water supply Road C1 Primary cooling Water C2 secondary cooling water

Claims (4)

In the heat exchanger decontamination method for decontaminating the inside of the heat exchanger tube of the heat exchanger,
A step of flowing a jet mixed with abrasive material from the first port of the heat transfer tube to the second port and flowing into the heat transfer tube;
Next, the second mouth side of the heat transfer tube is switched from the downstream side to the upstream side of the jet flow until the inner surface on the first mouth side and the inner surface on the second mouth side of the heat transfer tube become the target grinding amount at the same time. When half of the set time has elapsed, the step of causing the jet mixed with the abrasive material to flow from the second port of the heat transfer tube to the first port and flow into the heat transfer tube;
A heat exchanger decontamination method comprising: When the jet mixed with abrasive is flowing into the heat transfer tube,
Recovering the abrasive from the downstream side of the jet;
Next, returning the recovered abrasive to the upstream side of the jet,
The heat exchanger decontamination method according to claim 1, comprising: In a heat exchanger decontamination device that decontaminates the inside of a heat exchanger tube,
A positive inflow circuit for flowing a jet mixed with abrasive material from the first port of the heat transfer tube to the second port and into the heat transfer tube;
A reverse inflow circuit for flowing the jet mixed with abrasive material from the second port of the heat transfer tube to the first port and flowing into the heat transfer tube;
A switching unit that selectively switches to the forward inflow circuit or the reverse inflow circuit;
By setting the second port side of the heat transfer tube from the downstream side to the upstream side of the jet, the set time until the inner surface of the first port side and the inner surface of the second port side of the heat transfer tube simultaneously reach the target grinding amount is increased. Control means for storing in advance and switching the switching unit to the reverse inflow circuit when half of the set time has elapsed since the switching unit was selected as the forward inflow circuit;
A heat exchanger decontamination apparatus comprising:   A polishing material circulating means that is provided in common to the forward inflow circuit and the reverse inflow circuit, collects the abrasive that has come out from the downstream side of the jet, and returns the recovered abrasive to the upstream side of the jet The heat exchanger decontamination apparatus according to claim 3, comprising:

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