Patent Number: 
Section: claims

1. A preventive maintenance/repair device for use in maintaining and repairing a cylindrical structure of a cylindrical shape among reactor internal structures installed in a reactor pressure vessel, the preventive maintenance/repair device comprising:a device body;a holding mechanism connected to the device body, the holding mechanism being configured to hold the device body on an outer circumferential surface of the cylindrical structure;a traveling and driving part disposed on the device body, the traveling and driving part being configured to be circumferentially movable along the outer circumferential surface of the cylindrical structure; anda maintenance/repair mechanism disposed on the holding mechanism, the maintenance/repair mechanism being configured to maintain and repair the cylindrical structure,wherein the cylindrical structure is a jet pump,the device body is provided with an access device configured to bring the device body to the cylindrical structure and to detachably hold the device body,the access device includes:an access-device holding part engageable with the device body and holding the device body;an operation pole extending to an operation floor; anda rotating and driving part interposed between the access-device holding part and the operation pole, the rotating and driving part being configured to rotate the access-device holding part with respect to the operation pole around an axis disposed substantially perpendicular to a longitudinal axis of the cylindrical structure, andthe access device is configured to hold the device body in substantially a same direction as a longitudinal axis of the operation pole or a direction substantially perpendicular to the longitudinal axis of the operation pole. 2. The preventive maintenance/repair device according to claim 1, whereinthe holding mechanism includes: a pair of arms each having a shape along the outer circumferential surface of the cylindrical structure; guide rollers respectively disposed on distal ends of the pair of arms; arm cylinders configured to respectively drive the pair of arms; and links connected between the arms and the arm cylinders, the links being configured to transmit drives of the arm cylinders to the arms. 3. The preventive maintenance/repair device according to claim 2, whereineach of the arms of the holding mechanism is separable into a proximal arm body and a distal arm end, andin order to hold the device body on an outer circumferential surface of another cylindrical structure of a different outer diameter, the arm end is configured to be replaced with another arm end of a different length with respect to the arm body. 4. The preventive maintenance/repair device according to claim 2, whereineach of the arms of the holding mechanism is separable into a proximal arm body and a distal arm end, andin order to hold the device body on an outer circumferential surface of another cylindrical structure of a different outer diameter, the arm body is configured to be replaced with another arm body of a different length with respect to the device body. 5. The preventive maintenance/repair device according to claim 1, whereina distance sensor is disposed on an outer surface of the device body on a side opposed to a surrounding structure. 6. The preventive maintenance/repair device according to claim 1, whereinthe maintenance/repair mechanism includes an equipment configured to maintain and repair the cylindrical structure, and an equipment cylinder configured to drive the equipment in a direction parallel to the longitudinal axis of the cylindrical structure. 7. The preventive maintenance/repair device according to claim 1, wherein the rotating and driving part comprises a frame rotatably connected to the access-device holding part and a rotational cylinder, the rotational cylinder having a shaft configured to expand and contract such that the access-device holding part rotates with respect to the operation pole around the axis disposed substantially perpendicular to the longitudinal axis of the cylindrical structure. 8. A preventive maintenance/repair method using a preventive maintenance/repair device for use in maintaining and repairing a cylindrical structure of a cylindrical shape among reactor internal structures installed in a reactor pressure vessel, the preventive maintenance/repair device comprising:a device body;a holding mechanism connected to the device body, the holding mechanism being configured to hold the device body on an outer circumferential surface of the cylindrical structure;a traveling and driving part disposed on the device body, the traveling and driving part being configured to be circumferentially movable along the outer circumferential surface of the cylindrical structure; anda maintenance/repair mechanism disposed on the holding mechanism, the maintenance/repair mechanism being configured to maintain and repair the cylindrical structure;wherein the device body is provided with an access device configured to bring the device body closer to the cylindrical structure so as to attach the device body to the outer circumferential surface of the cylindrical structure and to detach therefrom the device body,an operation pole is connected to the access device, andthe access device includes a rotating and driving part,the preventive maintenance/repair method comprising the steps of:mounting the access device and the operation pole on the device body;sending the device body into the reactor pressure vessel in a hanging manner through the operation pole and bringing the device body closer to the cylindrical structure using the rotating and driving part, the rotating and driving part being configured to rotate the access device with respect to the operation pole around an axis disposed substantially perpendicular to a longitudinal axis of the cylindrical structure;holding the device body on the outer circumferential surface of the cylindrical structure by the holding mechanism;removing the access device from the device body, after the device body has been held on the cylindrical structure by the holding mechanism; andperforming a maintenance/repair operation to the cylindrical structure by the maintenance/repair mechanism. 9. The preventive maintenance/repair method according to claim 8, wherein the rotating and driving part comprises a frame rotatably connected to an access-device holding part of the access device and a rotational cylinder, and bringing the device body closer to the cylindrical structure using the rotating and driving part comprises expanding and contracting a shaft of the rotational cylinder such that the access device rotates with respect to the operation pole around the axis disposed substantially perpendicular to the longitudinal axis of the cylindrical structure. 10. An access device for a preventive maintenance/repair device for use in maintaining and repairing a jet pump of a cylindrical shape among reactor internal structures installed in a reactor pressure vessel, the access device being configured to bring the preventive maintenance/repair device to the jet pump and to detachably hold the preventive maintenance/repair device,the access device comprising:an access-device holding part engageable with the preventive maintenance/repair device and holding said preventive maintenance/repair device;an operation pole extending to an operation floor; anda rotating and driving part interposed between the access-device holding part and the operation pole, the rotating and driving part being configured to rotate the access-device holding part with respect to the operation pole around an axis disposed substantially perpendicular to a longitudinal axis of the cylindrical structure, andwherein the access device is configured to hold the preventive maintenance/repair device in substantially a same direction as a longitudinal axis of the operation pole or a direction substantially perpendicular to the longitudinal axis of the operation pole. 11. The access device according to claim 10, wherein the rotating and driving part comprises a frame rotatably connected to the access-device holding part and a rotational cylinder, the rotational cylinder having a shaft configured to expand and contract such that the access-device holding part rotates with respect to the operation pole around the axis disposed substantially perpendicular to the longitudinal axis of the cylindrical structure.