Patent Number: 046860770
Section: claims

1. A nuclear reactor installation comprising a pressure vessel;  a reactor core within said vessel, said core including straight vertical channel-like fuel elements for containing fissile material, vertically movable control rods between said fuel elements and absorber rods secured to said control rods between said fuel elements;  a plurality of guide rods, each guide rod being disposed within and extending from a respective control rod to define an annular gap therebetween and having a tubular bottom half disposed in immobile relation to said fuel elements, each guide rod having a plurality of bores communicating an interior of said guide rod with said annular gap;  conveying means for conveying a coolant from said pressure vessel into said interior of each said guide rod to move said control rods;  a first annular restrictor at one end of each said control rod communicating said annular gap with the interior of said pressure vessel; and  a second annular restrictor at an opposite end of each said control rod communicating said annular gap with the interior of said pressure vessel;  said communicating bores and said restrictors being sized whereby said control rods move in one axial direction in response to an increasing quantity of coolant flow into said guide rod interiors and in an opposite axial direction in response to a decreasing quantity of coolant flow into said guide rod interiors.  a pressure vessel;  a reactor core within said vessel having at least one fuel element and a vertically movable control rod;  a guide rod disposed within said control rod to define an annular gap therewith and having a tubular bottom disposed in immobile relation to said fuel element with a plurality of bores communicating an interior of said guide rod with said annular gap;  conveying means for conveying a coolant from said pressure vessel into said interior of said guide rod to move said control rod relative to said guide rod and said fuel element;  a first annular restrictor at one end of said control rod communication said annular gap with the interior of said pressure vessel; and  a second annular restrictor at an opposite end of said control rod communicating said annular gap with the interior of said pressure vessel, said bores and said restrictors comprising means whereby said control rod moves in one axial direction in response to an increasing quantity of coolant flow into said guide rod interior and in an opposite axial direction in response to a decreasing quantity of coolant flow into said guide rod interior. 2. A nuclear reactor installation as set forth in claim 1 which further comprises a level of liquid coolant within said pressure vessel and wherein said conveying means has an intake disposed immediately below said level for conveying the coolant to said guide rods. 3. A nuclear reactor installation as set forth in claim 2 wherein said conveying means includes at least one speed-controlled pump for pumping coolant to said guide rods, a bypass line connected in parallel with said pump and a variable restrictor in said bypass line to control a flow of coolant therethrough. 4. A nuclear reactor installation as set forth in claim 1 wherein said communicating bores are distributed vertically along each said guide rod. 5. A nuclear reactor installation as set forth in claim 1 wherein each guide rod has a top half of smaller diameter than a bottom half thereof with said bores disposed in said bottom half and which further comprises a removable guide cap on a top end of each control rod to form said second restrictor with said top half for a laminar flow of coolant therethrough. 6. A nuclear reactor installation as set forth in claim 5 wherein said top half of each guide rod is of decreasing diameter in an upward direction. 7. A nuclear reactor installation as set forth in claim 5 wherein each guide rod has at least one adjustable continuous bore at a top end communicating said interior of said guide rod with the interior of said pressure vessel. 8. A nuclear reactor installation as set forth in claim 7 which further comprises at least one restrictor for controlling a supply of coolant to said continuous bore in each guide rod in response to coolant pressure whereby said restrictor opens said continuous bore in response to a shortfall of the coolant pressure. 9. A nuclear reactor installation as set forth in claim 5 which further comprises a core support plate connected to and within said pressure vessel for supporting said fuel elements and a guide lattice secured to and within said pressure vessel for guiding said top end of each guide rod. 10. A nuclear reactor installation as set forth in claim 1 wherein said communicating bores are distributed vertically along each said guide rod on an upwardly decreasing spacing. 11. A nuclear reactor installation as set forth in claim 1 wherein said communicating bores are distributed vertically along each said guide rod and which further comprises a plurality of grooves in each control rod disposed transversely thereof and with each groove in facing relation to at least one bore of a respective guide rod. 12. A nuclear reactor installation as set forth in claim 11 wherein each control rod has at least one stabilizing aperture connecting at least one of said grooves with the interior of said pressure vessel. 13. A nuclear reactor installation as set forth in claim 12 wherein each stabilizing aperture is a slot extending lengthwise of said respective control rod. 14. A nuclear reactor installation as set forth in claim 12 wherein each stabilizing aperture is a slot extending transversely of said respective control rod. 15. A nuclear reactor installation as set forth in claim 12 wherein each control rod has a stabilizing aperture connecting each of said grooves with the interior of said pressure vessel, each said aperture being of decreasing flow cross-section in an upward direction. 16. A nuclear reactor installation as set forth in claim 11 wherein said communicating bores are of decreasing flow cross-section in an upward direction. 17. A nuclear reactor installation as set forth in claim 1 wherein a top half of each guide rod has a plurality of annular grooves and each control rod has at least one annular projection facing a respective top half of a guide rod to form said second annular restrictor. 18. A nuclear reactor installation comprising 19. A nuclear reactor installation as set forth in claim 18 wherein said guide rod includes a bore extending through a top half thereof communicating said annular gap with the interior of said pressure vessel and which further comprises an adjusting cap on said guide rod for adjusting the flow cross-section of said bore in said top half. 20. A nuclear reactor installation as set forth in claim 18 wherein said restrictors are of different restrictions.