Patent Number: 
Section: claims

1. A working apparatus for doing works below an annular shroud support plate arranged substantially horizontally between an inner surface of a nuclear reactor pressure vessel and an outer surface of a shroud, the apparatus comprising:a working equipment for doing works;a folding/unfolding mechanism that can be folded when moving the working equipment and unfolded when doing work;a conveyance mechanism for conveying the working equipment and the folding/unfolding mechanism to the site of the work;a pressing mechanism for pressing the working equipment upward against a lower surface of the annular shroud support plate;a traveling mechanism including wheels for traveling under and along the annular shroud support plate and positioning the apparatus; andball casters so as to be held in contact with the lower surface of the annular shroud support plate when the pressing mechanism presses the working equipment against the lower surface of the annular shroud support plate,wherein the folding/unfolding mechanism is so constructed that the working equipment can be positioned by pressing the wheels to the inner surface of the nuclear reactor pressure vessel and the outer surface of the shroud when the folding/unfolding mechanism is unfolded. 2. The working apparatus according to claim 1, wherein the conveyance mechanism includes a ballast tank for submerging and lifting up the working equipment in water. 3. The working apparatus according to claim 1, wherein the working equipment is at least one selected from a group consisting of an inspection sensor, a visual inspection camera, an ultrasonic flaw detecting sensor and an eddy current flaw detecting sensor. 4. The working apparatus according to claim 1, wherein the working equipment is at least one selected from a group consisting of a brush for polishing works, a grinding jig, a washing water nozzle, a water jet peening head, a laser peening head, a welding head for repair welding and a grinding jig for grinding welded sections. 5. The working apparatus according to claim 1, wherein the conveyance mechanism includes thrusters that can move the working equipment at least vertically and horizontally and turn it around a vertical axis. 6. The working apparatus according to claim 1, wherein the traveling mechanism includes at least three wheels and a folding/unfolding mechanism for unfolding and pressing the wheels. 7. The working apparatus according to claim 1, wherein each of the wheels has a shape of a truncated cone and is fitted in position with a large diameter side thereof facing downward and adapted to exert force for moving the apparatus upward as it is driven to rotate while being pressed against a wall surface. 8. The working apparatus according to claim 1, wherein it includes mechanism constituting members and strength holding members formed by using a polymeric resin material. 9. A working apparatus for doing works on an annular shroud support plate arranged substantially horizontally between an inner surface of a nuclear reactor pressure vessel and an outer surface of a shroud in water, the apparatus comprising:a main body casing including a ballast tank;a working equipment arranged at an upper part of the main body casing so as to be able to project outward by way of a drive mechanism and adapted to do various works on the annular shroud support plate;a float arranged at an upper part of the main body casing so as to be able to project outward by way of a drive mechanism;wheels arranged at outside of the working equipment and the float and adapted to abut the annular shroud support plate so as to turn the working equipment and the float; andball casters arranged above the wheels so as to be held in contact with a lower surface of the annular shroud support plate. 10. The working apparatus according to claim 9, wherein the working equipment is at least one selected from an inspection sensor, a visual inspection camera, an ultrasonic flaw detecting sensor and an eddy current flaw detecting sensor. 11. The working apparatus according to claim 9, wherein the working equipment is at least one selected from a group consisting of a brush for polishing works, a grinding jig, a washing water nozzle, a water jet peening head, a laser peening head, a welding head for repair welding and a grinding jig for grinding welded sections. 12. The working apparatus according to claim 9, wherein the conveyance mechanism includes thrusters that can move the working equipment at least vertically and horizontally and turn it around a vertical axis. 13. The working apparatus according to claim 9, wherein the traveling mechanism includes at least three wheels and a folding/unfolding mechanism for unfolding and pressing the wheels. 14. The working apparatus according to claim 9, wherein each of the wheels has a shape of a truncated cone and is fitted in position with a large diameter side thereof facing downward and adapted to exert force for moving the apparatus upward as it is driven to rotate while being pressed against a wall surface. 15. The working apparatus according to claim 9, wherein it includes mechanism constituting members and strength holding members formed by using a polymeric resin material. 16. The working apparatus according to claim 1, wherein the traveling mechanism is so constructed as to move the apparatus horizontally along the outer surface of the annular shroud while holding the ball casters in contact with the lower surface of the annular shroud support plate.