JP6364261B2 - In-pipe lining method for piping for nuclear facilities - Google Patents

Description

  The present invention relates to a pipe lining method, and more particularly, to a pipe lining method used for transportation of a fluid containing a radioactive substance and salt or a fluid containing salt under a high radiation dose in a nuclear facility or the like.

  There is a need for piping that can safely carry out transport of fluids containing radioactive materials or fluids under high radiation doses for long periods of time in nuclear facilities. In particular, when an internal fluid containing salinity is transported, there is a concern about a leaking event from a pipe due to corrosion, and therefore a countermeasure for suppressing corrosion is required.

As a countermeasure against corrosion, a lining pipe in which a lining treatment such as polyethylene is applied to the inside of the steel pipe before construction is used. However, lining piping is difficult to produce long piping, and cannot be applied particularly to buried piping or existing piping. For this reason, the piglining method has attracted attention as a lining method that can be used for buried piping, existing piping, and long piping. Piglining is a method of coating a lining material on the inner surface of a pipe while moving a ball called a pig by air pressure. The lining material used in the pig lining method is a material that is hardened at room temperature (room temperature hardening) and has a long pot life (pot life) with emphasis on workability. A lining material satisfying such requirements has a low glass transition temperature, and generally has a glass transition temperature after room temperature curing of less than 60 ° C. In addition, a room temperature curing pigling material requires a long curing reaction in order to obtain a desired strength. Conventionally, Patent Document 1 discloses a resin coating layer as a lining method for curing a resin coating layer in a short time. It is described that after the formation, a heating fluid is allowed to flow in the existing piping to heat the resin coating layer to accelerate the curing reaction.

JP 2000-061397

  In transportation facilities in nuclear facilities, several tens to several hundreds of piping for transfer are stretched and connected to a plurality of contaminated water retention areas. The total length of these pipes is about 10 to 20 km. In many cases, the transfer pipes of such nuclear facilities transfer water or seawater containing radioactive materials. The maximum temperature of this water or seawater is about 66 ° C. On the other hand, a room temperature curing pigling material has a characteristic that the linear expansion coefficient once changes from positive (expansion) to negative (shrinkage) and then becomes positive (expansion) near the glass transition temperature. As described above, the glass transition temperature after curing of the room temperature curing pigmenting material is 60 ° C. or lower, and a higher temperature fluid flows in the transfer piping of the nuclear facility. In this case, the phenomenon that the lining material contracts while the piping expands due to thermal expansion occurs, and the piping and the lining material peel off. Therefore, the glass transition temperature cannot be used in an environment higher than the glass transition temperature, and it is necessary to increase the glass transition temperature in order to use it as a lining material for transfer piping of nuclear facilities.

  Some of the transfer pipes for nuclear facilities are also installed outdoors. It is envisioned that the outdoor piping is heated by direct sunlight during the curing reaction of the pig lining material. If the lining material formed in the pipe has fluidity, there is no problem even if it is heated, but it is heated in a state where the fluidity is lost due to the progress of the curing reaction and the curing reaction is insufficient. If it does, peeling of piping and a lining material will arise by expansion of piping and shrinkage | contraction of a lining material. For this reason, it is also important to shorten the curing time of the lining material.

  It can be expected that the curing time can be shortened by flowing a heating fluid through the pipe as in Patent Document 1 to heat the resin coating layer. However, there are many sites where heated fluid cannot flow in transportation facilities in nuclear facilities, and a pigling method suitable for nuclear facilities is desired.

  The present invention provides an in-pipe lining method for piping for nuclear facilities using a room temperature curing type pig lining material, which can shorten the curing time and can form a lining layer having a high glass transition temperature after curing. Objective.

  The in-pipe lining method of the present invention is a method of forming a lining layer on the inner surface of a pipe for a nuclear facility, and a coating film process for forming a lining layer on the inner surface of the pipe using a room temperature curing type lining material and a pig, And a curing step of curing the lining layer by flowing a fluid containing a radioactive substance into the pipe.

  According to the present invention, in an in-pipe lining method for nuclear facilities piping using a room temperature curing type pig lining material, it is possible to provide a method capable of forming a lining layer capable of shortening the curing time and having a high glass transition temperature after curing. it can.

  Hereinafter, embodiments of the pipe lining method of the present invention will be described. The in-pipe lining method of the present embodiment is applied to a transfer pipe of a transport facility in a nuclear facility. As the lining layer formed in the pipe, the glass transition temperature needs to be higher than 66 ° C. which is the maximum use temperature of the transfer pipe. Therefore, in the in-pipe lining method of the present embodiment, a lining layer is formed on the inner surface of the pipe by using a room temperature curing type lining material and a sliding member (pig) for extending and painting the lining material on the inner face of the pipe. The glass transition temperature of the lining layer is set to 75 ° C. or higher, preferably 80 ° C. or higher by performing a coating process and a curing process in which a fluid containing a radioactive substance is flowed into the pipe to cure the lining layer. It is characterized by. Here, as a coating film process, it is only necessary to apply a room temperature curing type lining material in the tube, and a known pig lining method can be applied. Even if the curing reaction proceeds at room temperature (15 to 25 ° C.) after the coating step, the glass transition temperature of the lining layer is less than 60 ° C., and it cannot be applied to the transfer piping of nuclear facilities. Therefore, in the present embodiment, after the coating process, a curing process is performed in which a fluid containing a radioactive substance is allowed to flow in the pipe to cure the lining layer. In general, when a radioactive material is irradiated with a resin material, a hydrogen radical or a hydrocarbon radical is generated, and a crosslinking reaction occurs due to a bond between the radicals. Moreover, it is known that an epoxy resin generally increases a bending elastic modulus by irradiation, and the hardness increases by irradiation. In the present embodiment, it is possible to promote the curing reaction of the lining layer by flowing a fluid containing a radioactive substance in the piping using the feature that the transfer piping of the nuclear facility is a radiation environment. As a result, the glass transition temperature of the lining layer can be increased, and the glass transition temperature of the lining layer can be 75 ° C. or higher. As a result, it is possible to transport a high-temperature fluid necessary for use in nuclear facilities. Moreover, it becomes possible to shorten hardening time rather than normal room temperature hardening by accelerating hardening reaction by irradiation. In addition, in order to prevent heating by direct sunlight in the outdoor piping, it is preferable to carry out the curing step in a state where the outdoor piping is cured so as to block the direct sunlight. Moreover, you may provide the drying process which dries a coating film between a coating-film process and a hardening process.

  As the room temperature curable lining material, it can be applied as long as it is liquid at room temperature, has room temperature curability, has a long working life of several hours or more, and satisfies the viscosity capable of pigling. Known lining materials can be applied. In particular, a solventless two-component curable epoxy resin can be preferably used.

  In addition to the glass transition temperature, corrosion resistance in a radiation environment is also required as a lining layer for transfer piping in nuclear facilities. In many cases, the transfer pipe transfers water or seawater containing radioactive substances. Therefore, the influence of water on the lining material inside the pipe must be taken into consideration. In general, it has been found that the influence of moisture in a radiation environment is severely deteriorated as studied in a LOCA (Loss of Coolant Accident) simulation test of an insulator used in a nuclear cable. In particular, when moisture is present in the atmosphere, the peroxide (ROOH) generated by oxidation dissociates under the influence of protons in water to generate a carbonyl group (> C = O) and water, and hydrogen in the molecular chain. It is known that a catalytic reaction for liberating proceeds. The generated carbonyl group (> C = O) is considered to promote oxidative degradation because it easily breaks the molecular chain to become a radical and hydrogen is easily extracted adjacent to the carbonyl group. In particular, in the case of a lining material having a glass transition temperature of 50 ° C. or lower, oxidative degradation is promoted.

  Furthermore, it is known that ozone is generated in a radiation environment. Ozone acts strongly on high density polyethylene with double bonds in the molecular chain. For example, when ozone attacks the double bond portion, an ozonide is formed, which is unstable, so that the O—O bond is cleaved to form an aldehyde, ketone, ester, lactone, peroxide or the like. It is known that the decomposition of the molecular structure by ozone forms minute cracks (ozone cracks). In particular, when a pipe pressure of 1 MPa is applied, the pipe is always stretched, which increases the ozone permeability and causes ozone cracks to grow due to stress concentration, leading to pipe corrosion. In particular, in the case of a lining material having a glass transition temperature of 50 ° C. or lower, decomposition is accelerated.

  In order to improve the corrosion resistance under radiation environment, bisphenol A type epoxy resin is used as the main component, and amine curing agents such as aromatic amines, aliphatic amines and alicyclic amines are used as curing agents. The two-part curable epoxy resin is preferable. Moreover, it is preferable to add carbon black, silica, and a silane coupling agent to the two-component curable epoxy resin. The addition of carbon black increases the resistance of the resin to ozone. Further, by adding silica, it is possible to suppress the deterioration of the resin when the solid substance of the radioactive substance collides with the surface. Furthermore, the addition of the silane coupling agent increases the adhesion to the steel pipe surface, and can maintain the adhesion performance while suppressing deterioration even in a radiation environment.

  Moreover, you may add the catalyst for photocationic polymerization, an imidazole series hardening accelerator, and antioxidant as another additive.

  By using the photocationic polymerization catalyst, the curing reaction of the lining material is accelerated by receiving the energy of radiation. As the photocationic polymerization catalyst, an oxetane compound, a diazonium salt, a diaryliodonium salt, a triarylsulfonium salt, or a silylbenzyl ether is preferably used in terms of acceleration of curing by radiation.

  Imidazole has the effect of scavenging radicals generated in a radiation environment. Therefore, radiation resistance improves by adding an imidazole series hardening accelerator. Examples of imidazole curing accelerators include 2-ethyl-4-methylimidazole, 2-phenylimidazole, 1- (2-cyanoethyl) -2-ethyl-4-methylimidazole, 2,4-diamino-6- [2- Methylimidazolyl] ethyltriazine and 2-phenylimidazoline are preferably used in terms of radiation resistance.

  By adding an antioxidant, deterioration of the lining material can be suppressed even when a fluid containing a high-temperature radioactive substance flows. As the antioxidant, a phenol-based antioxidant and an amine-based antioxidant are preferable because both heat resistance and radiation resistance can be achieved.

  The inventors of the present invention conducted various durability tests under various irradiation conditions for various pigling materials, and obtained the following knowledge.

  By using the lining layer formed by using the in-pipe lining method of the present embodiment, corrosion of buried piping, existing piping, and long piping can be suppressed.

  It was possible to accelerate the curing of the lining layer by flowing a fluid containing a radioactive substance in the pipe after the coating process, and to make the glass transition temperature 75 ° C. or higher. The glass transition temperature of the lining layer after the curing process by radiation may be 75 ° C. or higher when applied to a transfer pipe of a nuclear facility. The operating temperature of the transfer pipe is 66 ° C. at the maximum, and even if the temperature rises and the pipe is extended, the lining material is similarly extended, so that no cracks or cracks are generated and the soundness is maintained. In addition, the thermal expansion coefficient of the lining layer after carrying out the curing step by radiation does not exhibit a shrinkage behavior that changes from plus to minus in the vicinity of the glass transition temperature at the same time as the glass transition temperature rises to 75 ° C. or higher. I understood.

  In addition, since it can be cured by radioactive materials in the internal fluid and radiation from the installation environment, it does not cure unless it is left standing for a long period of time in conventional room temperature curing, but it cures in a short time without using hot water or high temperature steam. Can be made.

  Pipes for transfer of nuclear facilities transfer high-dose radioactive water, seawater, and high-temperature fluid. Even under such severe conditions, defects such as cracks and pinholes in the lining material do not occur. Further, in constructing the equipment, the influence of time and space restrictions can be minimized with respect to piping construction, and a certain level of safety can be ensured as equipment for handling radioactive substances.

Moreover, in the transportation equipment in a nuclear facility, several tens to several hundreds of piping for the transfer are stretched and connected to a plurality of contaminated water retention areas. The total length of these pipes is about 10 to 20 km. It is not easy to check for cracks and minute cracks at such a long distance, and a huge amount of time is required. Once the piping is found to be defective, the entire piping must be replaced, which requires a lot of time and effort. However, according to the in-pipe lining method of the present embodiment, lining can be easily performed on a long existing pipe. In addition, the system must be stopped for the replacement of the pipe, which causes a great hindrance to the entire system. However, according to the in-pipe lining method of the present embodiment, the repair work by the lining is completed in a short time without replacing the existing pipe. Further, according to the in-pipe lining method of the present embodiment, it is possible to obtain a long-life transfer pipe while suppressing deterioration of the lining material even in a high radiation environment, and the reliability and safety are high in nuclear-related facilities. Transportation facilities can be provided, and the stability of the entire system can be improved.
Example 1
This embodiment is a pipe lining method in which, for example, when there is a corroded part in a piping for transfer used in a nuclear facility, the inner surface of the pipe including the corroded part is repaired, and a liquid lining material is used. As a push-in tool for applying to the inner surface of the pipe while pushing forward in the pipe, a spherical pig and an air compressor for applying a push force to the pig are implemented.

  First, as a lining material, a bisphenol A type epoxy resin is mixed as a main agent and a modified polyamine as a curing agent in a ratio of 2: 1. The ratio of the main agent and the curing agent is adjusted by the relationship between the pot life and the curing time. In this embodiment, the pipe length of 1000 m or more can be applied, and the ratio of the main agent and the curing agent is adjusted so that the curing reaction time is shortened. A liquid lining material prepared by adding carbon black, silica, and a silane coupling agent to a mixture of bisphenol A type epoxy resin and modified polyamine in a ratio of 2: 1 is prepared. It was 50 degreeC when the glass transition temperature of the normal temperature hardened | cured material of this material was calculated | required with the vertical thermal dilatometer. Further, it was found that at a temperature higher than 50 ° C., the linear expansion coefficient decreased and became negative, and shrinkage occurred. Furthermore, in order to investigate the degree of curing, the hardness of the room temperature cured product was measured using a Barcol hardness tester. The surface hardness was 61-66.

  Next, a liquid lining material and a pig are put into the pipe from one end of the pipe, and an air supply hose from the air compressor is connected to the insertion port. After that, by applying pressurized air with an air compressor to pressurize the space between the insertion port and the pig to push away the lining material in front of the pig, a coating layer of the lining material is applied to the inner peripheral surface of the pipe. Form.

  Next, from the opposite side, a liquid lining material and a pig are put into the pipe, and an air supply hose from an air compressor is connected to the insertion port. After that, by applying pressurized air with an air compressor to pressurize the space between the insertion port and the pig to push away the lining material in front of the pig, a coating layer of the lining material is applied to the inner peripheral surface of the pipe. Two layers are formed. By applying two layers, the entrained bubbles are crushed and the coated surface becomes strong, and the intrusion of fluid can be prevented.

  Dry in this state for at least 24 hours.

  If the pig is removed to the other end side of the pipe by the above procedure, a coating layer (lining layer) made of a lining material is formed on the inner peripheral surface of the pipe over the entire length.

  Next, a fluid containing a radioactive substance is circulated inside the pipe. The curing of the lining layer is promoted by receiving the energy of the radiation. It was 75 degreeC when the glass transition temperature of the hardened | cured material after hardening by a radiation was calculated | required with the vertical thermal dilatometer. Furthermore, in order to examine the degree of curing, the surface hardness was measured using a Barcol hardness tester. It was found that the hardness of the surface was 80 or more, and the effect of the radiation curing treatment was obtained. Further, it was confirmed that the shrinkage near the glass transition temperature hardly occurred.

  From this example, it was confirmed that the Tg and strength of the lining layer can be improved by flowing a fluid containing a radioactive substance in the pipe after forming the lining layer by the pig lining method using a room temperature curing type lining material. did.

  According to the present invention, it is possible to safely transport a fluid containing a radioactive substance or a fluid under a high radiation dose for a long period of time. Specifically, even in high radiation environments brought about by transporting radioactive materials, ozone environments generated by radiation, high-temperature environments brought about by transferring high-temperature fluids, and salty environments contained in transport fluids Since the lining material constituting the pipe is hardly deteriorated and does not cause defects such as cracks and microcracks, the pipe can be used for a long time without corroding and opening a hole. Further, the soundness of the piping is maintained without being damaged by gravel or stone in the fluid. Furthermore, it can be applied to existing pipes, buried pipes, and long pipes with a length of 1000 m or more, and the number of man-hours is small, and the safety of workers can be ensured in a short time. Since piping does not corrode, it can contribute to the improvement of the reliability and safety of the whole system concerning the transfer of radioactive materials in a nuclear power plant. In addition, even if the pipe metal is stretched due to an increase in temperature, the lining material is stretched in the same manner, so that cracks and cracks do not occur, and soundness is maintained.

  The present invention consists of a pipe lined with resin using a pig lining method as a transfer pipe used in nuclear facilities, and it is high even under a high radiation dose by using a specific lining method and material. It is possible to maintain the durability and to provide a long-life piping, which can contribute to the improvement of the reliability and safety of the entire system related to the transfer of radioactive material in the nuclear power plant.

Claims (3)

An in-pipe lining method for forming a lining layer on the inner surface of piping for a nuclear facility,
A coating process for forming a lining layer on the inner surface of the pipe using a room temperature curable lining material and a pig,
A curing step of curing the lining layer by flowing a fluid containing a radioactive substance in the pipe;
Equipped with a,
The glass transition temperature after normal temperature curing of the lining material is less than 60 ° C, and the glass transition temperature of the lining layer after the curing step is 75 ° C or higher,
The lining material is a two-component curable epoxy resin containing a bisphenol A type epoxy resin, an amine curing agent, carbon black, silica, and a silane coupling agent,
The in-pipe lining method, wherein the amine-based curing agent is any one of an aromatic amine, an aliphatic amine, and an alicyclic amine . In the pipe lining method according to claim 1,
The coating step is
Injecting the lining material from one end of the pipe, moving the pig from one end of the pipe toward the other end, and applying the lining material to the inner surface of the pipe;
Injecting a lining material from the other end of the pipe, moving the pig from the other end of the pipe toward one end, and applying the lining material to the inner surface of the pipe An in-pipe lining method comprising: In the pipe lining method according to claim 1,
An in-tube lining method comprising a drying step of drying the lining material applied in the coating step between the coating step and the curing step.