Patent Number: 040010783
Section: claims

1. In a nuclear reactor system having a pressure vessel with at least one penetration therein, and a core region enclosed by the pressure vessel and in which a plurality of control rod guide holes are distributed over an area larger than the cross section of the penetration, control apparatus comprising, a plurality of flexible control rods, one for each of said guide holes for insertion therein, a plurality of originally parallel guide tubes extending from said penetration and fanning out to respective ones of said guide holes for guiding said control rods from said penetration to said guide holes, an intermediate portion of each of said guide tubes including flexible means to permit said fanning out, means for moving said control rods through said guide tubes and into and out of said guide holes, and means for withdrawing said guide tubes from said guide holes and displacing the more widely fanned out spaced ends of said guide tubes to bring said tubes into parallel alignment for withdrawal through said penetration. 2. Apparatus according to claim 1 wherein each of said control rods comprises a plurality of rigid segments joined by flexible joints. 3. A nuclear reactor system comprising a pressure vessel with at least one penetration therein, a reactor core enclosed by said pressure vessel and having a core region in which a plurality of control rod guide holes are distributed over an area larger than the cross section of said penetration, a plurality of flexible control rods, one for each of said guide holes for insertion therein, a plurality of guide tubes extending from said penetration and fanning out to respective ones of said guide holes for guiding said control rods from said penetration to said guide holes an intermediate portion of each of said guide tubes including a flexible means to permit said fanning out, means for moving said control rods through said guide tubes and into and out of said guide holes, and means for withdrawing said guide tubes from said guide holes and displacing the more widely fanned out spaced ends of said guide tubes to bring said tubes into parallel alignment for withdrawal through said penetration. 4. In a nuclear reactor system having a core region comprised of a central column of core blocks surrounded by a plurality of adjacent peripheral columns of core blocks, and wherein the core region is contained within a reactor vessel, control apparatus comprising, a plurality of control rods, one for each of said peripheral columns and adapted for insertion in holes extending longitudinally in said peripheral columns, said control rods being flexible, means for guiding said control rods between a withdrawn position axially spaced from said core region whereat said control rods are positioned sufficiently close to each other to pass through a penetration in the reactor vessel and an inserted condition whereas said control rods are inserted in the openings in said peripheral columns, positioned relatively farther from each other than in said withdrawn region, said guide means comprising a plurality of originally parallel guide tubes, one for each of said peripheral columns extending from the holes in said columns and converging in a region axially spaced from the core region and positioned directly adjacent the interior end of the reactor vessel penetration, an intermediate portion of each of said guide tubes including a flexible means to permit fanning out of said guide tube and means for withdrawing said guide tubes from said guide holes and displacing the more widely fanned out spaced ends of said guide tubes to bring said guide tubes into parallel alignment sufficiently close to each other so as to be withdrawable through the reactor vessel penetration. 5. Apparatus according to claim 4 wherein the number of said peripheral columns is six. 6. Apparatus according to claim 4 including a hole in said central column extending longitudinally thereof, a control rod for said central column, and means for guiding said central column control rod into and out of said central column hole.