Maintenance/repair device for reactor internal structure

A reactor device comprising:

• a reactor internal support including a shroud, an upper lattice plate including a first through-hole and positioned above the shroud, and a core support plate including a second through-hole and positioned below the shroud;
• a maintenance/repair device for the reactor internal structure installed on a bottom of a reactor pressure vessel, the maintenance/repair device comprising:
• a device body fixed on the reactor internal support;
• a welding-part repair mechanism connected to the device body, the welding-part repair mechanism configured to maintain/repair a welding part of the reactor internal structure;
• and
• a cylindrical guide pipe extending from an upper part of the upper lattice plate to an upper part of the device body on the reactor internal structure, the cylindrical guide pipe having an outer diameter less than the first and second through-holes to pass through the first through-hole of the upper lattice plate and the second through-hole of the core support plate to be disposed between the upper lattice plate and the core support plate;
• and
• wherein the device body and the welding-part repair mechanism have diameters less than the diameter of the cylindrical guide pipe to be configured to be passed downward from above through the guide pipe, to maintain/repair the welding part of the reactor internal structure.