Multi-layered nuclear fuel cladding and method for manufacturing multi-layered nuclear fuel cladding

Abstract

Multi-layered nuclear fuel cladding, according to the present invention, comprises: an inner tube of zirconium alloy, of which both ends are open for providing an accommodation space into which a sintered nuclear fuel pellet is inserted; and an outer tube, disposed coaxially with the inner tube, having a greater diameter than the inner tube so as to surround the outer surface of the inner tube, wherein the outer tube and the inner tube are fixed to closely contact each other, and may be formed from metals different from each other.

1 . A multi-layered nuclear fuel cladding comprising:
 an inner tube of zirconium alloy, of which both ends are open for providing an accommodation space into which a sintered body of nuclear fuel is inserted; and   an outer tube, disposed coaxially with the inner tube, having a greater diameter than the inner tube so as to surround an outer surface of the inner tube,   wherein the outer tube and the inner tube are fixed to closely contact each other, and are formed from metals different from each other.   
     
     
         2 . The multi-layered nuclear fuel cladding of  claim 1 , wherein the metal configured to form the outer tube has a thermal expansion coefficient of 1 ppm/K to 40 ppm/K. 
     
     
         3 . The multi-layered nuclear fuel cladding of  claim 1 , wherein the metal configured to form the outer tube has a thermal neutron absorption cross-sectional area of 0.0045 barn to 440 barn. 
     
     
         4 . The multi-layered nuclear fuel cladding of  claim 1 , wherein the outer tube has greater ductility than the inner tube. 
     
     
         5 . The multi-layered nuclear fuel cladding of  claim 1 , wherein the outer tube comprises a protective layer provided on an outer surface of the outer tube. 
     
     
         6 . The multi-layered nuclear fuel cladding of  claim 5 , wherein the protective layer is a metal oxide or a metal nitride of the metal configured to form the outer tube. 
     
     
         7 . A method for manufacturing a multi-layered nuclear fuel cladding comprising:
 forming a preliminary cladding by inserting a preliminary inner tube of zirconium alloy provided with an accommodation space into which a sintered body of nuclear fuel is inserted, into a preliminary outer tube having a greater diameter than the preliminary inner tube and filling the preliminary inner tube with a filler;   closing both ends which are open in the preliminary cladding, with shielding members; and   applying a pressure from an outside toward an inside of the preliminary cladding to reduce a diameter of the preliminary cladding,   wherein the preliminary outer tube and the preliminary inner tube are formed from metals different from each other.   
     
     
         8 . The method for manufacturing a multi-layered nuclear fuel cladding of  claim 7 , wherein a metal configured to form the preliminary outer tube has a thermal neutron absorption cross-sectional area of 0.0045 barn to 440 barn. 
     
     
         9 . The method for manufacturing a multi-layered nuclear fuel cladding of  claim 7 , wherein the metal configured to form the preliminary outer tube has a thermal expansion coefficient of 1 ppm/K to 40 ppm/K. 
     
     
         10 . The method for manufacturing a multi-layered nuclear fuel cladding of  claim 7 , wherein the preliminary outer tube has greater ductility than the preliminary inner tube. 
     
     
         11 . The method for manufacturing a multi-layered nuclear fuel cladding of  claim 7 , further comprising dissolving the filler inside the preliminary inner tube, after the applying of the pressure. 
     
     
         12 . The method for manufacturing a multi-layered nuclear fuel cladding of  claim 11 , further comprising forming a protective layer on an outer surface of an outer tube manufactured by closely contacting and fixing the preliminary outer tube and the preliminary inner tube, after the dissolving of the filler. 
     
     
         13 . The method for manufacturing a multi-layered nuclear fuel cladding of  claim 12 , wherein the protective layer is formed by oxidation or nitrification of a metal configured to form the outer tube by plasma surface treatment. 
     
     
         14 . The method for manufacturing a multi-layered nuclear fuel cladding of  claim 7 , wherein in the applying of the pressure, the pressure applied to the inside of the preliminary cladding gradually increases, by moving the preliminary cladding between a plurality of pairs of rolls which are arranged to gradually decrease distances between rolls of each of the pairs,
 each of the plurality of pairs of rolls are respectively comprised in each of a plurality of roll units which are arranged to be spaced apart from each other in a lengthwise direction of the preliminary cladding.   
     
     
         15 . The method for manufacturing a multi-layered nuclear fuel cladding of  claim 7 , wherein in the applying of the pressure, the preliminary outer tube is mutually closely contacted and fixed, to the preliminary inner tube, by being more contracted than the preliminary inner tube.