Method, use and device concerning cladding tubes for nuclear fuel and a fuel assembly for a nuclear pressure water reactor

Abstract

A method of producing a cladding tube for nuclear fuel for a nuclear pressure water reactor includes forming a tube which at least principally consists of a cylindrical tube component of a zirconium-based alloy, where the alloying element, except for zirconium, which has the highest content in the alloy is niobium, wherein the niobium content in weight percent is between about 0.5 and about 2.4 and wherein no alloying element, except for zirconium and niobium, in the alloy, has a content which exceeds about 0.2 weight percent. The cladding tube is then annealed such that the tube component is partly but not completely recrystallized. The degree of recrystallization in the tube component is higher than about 40% and lower than about 95%. A fuel assembly for a nuclear pressure water reactor also has a plurality of such cladding tubes.

1 . A method of producing a cladding tube for nuclear fuel for a nuclear pressure water reactor, which method comprises the following steps:
 formation of a tube which at least principally consists of a cylindrical tube component of a Zr-based alloy, where the alloying element, except for Zr, which has the highest content in the alloy is Nb, wherein the Nb content in weight percent is between about 0.8 and about 1.2 and wherein no alloying element, except for Zr and Nb, in said alloy, has a content which exceeds about 0.2 weight percent, and carrying out a final anneal of the cladding tube at a temperature and during a time such that said tube component is partly recrystallized but not completely recrystallized, and wherein said final anneal is carried out such that the degree of recrystallization in said tube component is higher than about 40% and lower than about 95%.   
   
   
       2 . A method according to  claim 1 , wherein between said formation step and said final annealing step, said method includes the steps of rolling and heat treating said cladding tube. 
   
   
       3 . A method according to  claim 1 , wherein the final anneal is carried out at a temperature which is lower than 550° C. 
   
   
       4 . A method according to  claim 1 , wherein the final anneal is carried out at a temperature which is between about 400° C. and about 540° C. 
   
   
       5 . A method according to  claim 4 , wherein the final anneal is carried out at a temperature which is between about 450° C. and about 500° C. 
   
   
       6 . A method according to  claim 1 , wherein the final anneal is carried out such that the degree of recrystallization in said tube component is higher than about 60% and lower than about 90%. 
   
   
       7 . A method according to  claim 1 , wherein the final anneal is carried out during about 1 h to about 6 h. 
   
   
       8 . A method according to  claim 1 , wherein before said final anneal, the method comprises the following steps:
 forming a bar of said Zr-based alloy;   heating the bar to between about 900° C. and about 1300° C. and then quenching the bar;   extruding a billet from the bar after heating to between about 500° C. and about 900° C.; and   cold rolling the billet into a tube in at least two steps, with heat treatments between them at between about 550° C. and about 650° C.   
   
   
       9 . A method according to  claim 1 , wherein said alloy contains between about 800 ppm and about 1700 ppm O. 
   
   
       10 . A method according  claim 1 , wherein said alloy contains between about 50 ppm and about 600 ppm Fe. 
   
   
       11 . A method according  claim 1 , wherein said alloy in addition to Zr contains about 0.8 weight percent to about 1.2 weight percent Nb, about 50 ppm to about 600 ppm Fe, about 800 ppm to about 1700 ppm O, less than about 250 ppm C, less than about 150 ppm Si, less than about 1000 ppm S and in addition to that only impurities of a content which does not exceed that which is normally accepted in Zr or Zr alloys for applications in nuclear reactors. 
   
   
       12 . A cladding tube for nuclear fuel for a nuclear pressure water reactor, comprising a generally cylindrical tube component of a Zr-based alloy, wherein the alloying element, except for Zr, having the highest content in the alloy is Nb, wherein the Nb content in weight percent is between about 0.8 and about 1.2 and wherein no alloying element, except for Zr and Nb, in said alloy, has a content which exceeds about 0.2 weight percent, wherein said tube component has been finally annealed such that it has a structure that is partly recrystallized but not completely recrystallized and wherein the degree of recrystallization in said tube component is higher than about 40% and lower than about 95%. 
   
   
       13 . A cladding tube according to  claim 12 , wherein the degree of recrystallization in said tube component is higher than about 60% and lower than about 90%. 
   
   
       14 . A cladding tube according to  claim 12 , wherein said alloy contains between about 800 ppm and about 1700 ppm O. 
   
   
       15 . A cladding tube according to  claim 12 , wherein said alloy contains between about 50 ppm and about 600 ppm Fe. 
   
   
       16 . A cladding tube according to  claim 12 , wherein said alloy in addition to Zr contains about 0.8 weight percent to about 1.2 weight percent Nb, about 50 ppm to about 600 ppm Fe, about 800 ppm to about 1700 ppm O, less than about 250 ppm C, less than about 150 ppm Si, less than about 1000 ppm S and in addition to that only impurities of a content which does not exceed that which is normally accepted in Zr or Zr alloys for applications in nuclear reactors. 
   
   
       17 . A fuel assembly for a nuclear pressure water reactor, comprising:
 a plurality of cladding tubes, each having a generally cylindrical tube component of a Zr-based alloy, wherein the alloying element, except for Zr, having the highest content in the alloy is Nb, wherein the Nb content in weight percent is between about 0.8 and about 1.2 and wherein no alloying element, except for Zr and Nb, in said alloy, has a content which exceeds about 0.2 weight percent, wherein said tube component has been finally annealed such that it has a structure that is partly recrystallized but not completely recrystallized and wherein the degree of recrystallization in said tube component is higher than about 40% and lower than about 95%, and wherein each of said cladding tubes is filled with nuclear fuel suitable for such cladding tubes for a nuclear pressure water reactor;   wherein the fuel assembly also comprises:   a top plate,   a bottom plate,   a plurality of guide tubes for control rods, which guide tubes extend between the top plate and the bottom plate, and   a plurality of spacers arranged for maintaining said cladding tubes in position in the fuel assembly and at suitable distances from each other.   
   
   
       18 . A fuel assembly according to  claim 17 , wherein the degree of recrystallization in said tube component is higher than about 60% and lower than about 90%. 
   
   
       19 . A fuel assembly according to  claim 17 , wherein said alloy contains between about 800 ppm and about 1700 ppm O. 
   
   
       20 . A fuel assembly according to  claim 17 , wherein said alloy contains between about 50 ppm and about 600 ppm Fe. 
   
   
       21 . A fuel assembly according to  claim 17 , wherein said alloy in addition to Zr contains about 0.8 weight percent to about 1.2 weight percent Nb, about 50 ppm to about 600 ppm Fe, about 800 ppm to about 1700 ppm O, less than about 250 ppm C, less than about 150 ppm Si, less than about 1000 ppm S and in addition to that only impurities of a content which does not exceed that which is normally accepted in Zr or Zr alloys for applications in nuclear reactors.