Patent ID: 6503346
Filing Date: 2003-01-07
Classification: C21D,C22F,G21C,Y02E

Abstract:
A process for producing a cladding tube for a fuel rod of a boiling water reactor, the method which comprises:heating a starting body to a given temperature, the starting body being made from alloying constituents of a zircaloy, a fraction of the alloying constituents being dissolved at the given temperature, the fraction of the alloying constituents being insoluble at an operating temperature of a boiling water reactor; subsequently cooling a first region of the starting body at a first cooling-down rate and cooling a second region of the starting body at a second cooling-down rate, the first cooling-down rate being slower than the second cooling-down rate; subsequently extruding the starting body for forming a tube blank having an inner surface region and an outer surface region, the outer surface region originating from material of the second region of the starting body having a first logarithmic mean value of a particle size of a precipitated fraction of the alloying constituents, the inner surface region originating from material of the first region of the starting body having a second logarithmic mean value of a particle size of a precipitated fraction of the alloying constituents, the first logarithmic mean value being below 0.1 &mgr;m, the second logarithmic mean value being greater than the first logarithmic mean value; producing a cladding tube from the tube blank by using a mechanical/thermal treatment; exposing the inner surface region and the outer surface region to substantially identical temperatures during the mechanical/thermal treatment and applying, after the extruding step, only temperatures of below 810Â° C.; providing, with the mechanical/thermal treatment, the cladding tube with a given ductility, the given ductility resulting in a ductile yield of at least 20% at a temperature of 300Â° C.