Underwater remote inspection device and method for underwater remote inspection

An underwater remote inspection method for a reactor vessel, comprising:

• a first step of moving an underwater remote inspection device to a position facing an inspection area of an inspection object underwater, the underwater remote inspection device has an etching device and a magnifying camera device mounted to a supporting member, wherein the etching device has a chamber mounted to the supporting member, electrode members provided to the chamber, and a sealing device provided to a distal end portion of the chamber, facing the surface of the inspection object, and wherein the sealing device has an annular first sealing member attached to the distal end portion of the chamber, an annular second sealing member surrounding the first sealing member, attached to the distal end portion of the chamber, and a pipe line communicated to a sealing region formed between the first and the second sealing members, connected to a suction apparatus for reducing a pressure in the region;
• a second step of bringing a distal end portion of each of the first and second sealing members into contact with a surface of the inspection object;
• a third step of reducing pressure of the sealing region formed between the first and the second sealing members;
• a fourth step of supplying an agent for etching to an etchant filling region formed in the chamber;
• a fifth step of etching the inspection area surrounded by the sealing device by applying power to the electrode members while the agent is present in the etchant filling region;
• a sixth step of discharging the agent for etching from the etchant filling region by supplying pure water to the etchant filling region;
• a seventh step of releasing a pressing force of the first and second sealing members by increasing pressure in the sealing region formed between the first and second sealing members after the agent for etching is discharged from the etchant filling region;
• an eighth step of moving the magnifying camera device to a position facing the inspection area by moving the underwater remote inspection device after the seventh step;
• a ninth step of taking an image of the inspection area by the magnifying camera device;
• a tenth step of determining whether it is possible to distinguish a crack from grain boundaries of metal structure of the inspection area by using the image of the inspection area obtained by the magnifying camera device;
• an eleventh step of storing the image of the inspection area in a memory device when the crack is distinguished from the grain boundaries of the metal structure;
• and
• a twelfth step of determining whether the inspection area is sufficiently etched by using the image of the inspection area when the crack cannot be distinguished from the grain boundaries;
• wherein when it is determined that the inspection area is not sufficiently etched, the steps from the first step to the twelfth step are repeated.