Tube for a nuclear fuel assembly, and method for making same

Abstract

A zirconium alloy tube for forming the whole or the outer portion of a nuclear fuel pencil housing or a nuclear fuel assembly guide tube. The zirconium alloy contains 0.8-1.8 wt. % of niobium, 0.2-0.6 wt. % of tin and 0.02-0.4 wt. % of iron, and has a carbon content of 30-180 ppm, a silicon content of 10-120 ppm and an oxygen content of 600-1800 ppm. The tube may be used when recrystallized or stress relieved.

We claim: 
     
       1. A tube of zirconium-base alloy for constituting all or the outside portion of cladding for a nuclear fuel rod or of a guide tube for a nuclear fuel assembly, made of a zirconium-base alloy containing, by weight, 0.8% to 1.8% niobium, 0.2% to 0.6% tin, and 0.02% to 0.4% iron, plus inevitable impurities, and having a carbon content controlled to lie in the range 30 ppm to 180 ppm, a silicon content in the range 10 ppm to 120 ppm, and an oxygen content in the range 600 ppm to 1800 ppm. 
     
     
       2. A tube according to  claim 1 , wherein the alloy is in recrystallized state. 
     
     
       3. A tube according to  claim 1 , wherein the alloy is in relaxed state. 
     
     
       4. A tube according to  claim 1 , wherein the alloy has set contents: 0.9% to 1.1% niobium, 0.25% to 0.35% tin, and 0.2% to 0.3% iron. 
     
     
       5. A method of manufacturing a tube according to  claim 1  of zirconium-base alloy for constituting all or an outside portion of cladding for a nuclear fuel rod or of a guide tube for a nuclear fuel assembly, made of a zirconium-base alloy consisting essentially of, by weight, 0.8% to 1.8% niobium, 0.2% to 0.6% tin, and 0.02% to 0.4% iron, plus inevitable impurities, and having a carbon content controlled to lie in the range 30 ppm to 180 ppm, a silicon content in the range 10 ppm to 120 ppm, and an oxygen content in the range 600 ppm to 1800, including the following steps of:
 making a bar of an alloy containing 0.8% to 1.8% niobium, 0.2% to 0.6% tin, and 0.02% to 0.4% iron; 
 after heating in the bar to a temperature in the range 1000° C. to 1200° C., quenching the bar in water; 
 drawing the bar into a blank after heating to a temperature in the range 600° C. to 800° C.; 
 annealing the drawn blank at a temperature in the range 590° C. to 650° C.; and 
 cold rolling the annealed blank in at least four passes into a tube, with intermediate heat treatments at temperatures in the range 560° C. to 620° C. 
 
     
     
       6. A method according to  claim 5 , wherein the rolling passes are performed on tubes having increasing recrystallization ratios. 
     
     
       7. A method according to  claim 5 , further including a recrystallizing final heat treatment step at a temperature in the range 560° C. to 620° C. 
     
     
       8. A method according to  claim 5 , further including a strain relieving final heat treatment step at a temperature in the range from about 470° C. to 500° C. 
     
     
       9. A tube for constituting all or an outside portion of cladding for a nuclear fuel rod or of a guide tube for a nuclear fuel assembly, made of zirconium-base alloy consisting essentially of:
 0.8% wt. to 1.8% wt. niobium,   0.2% wt. to 0.6% wt. tin,   0.02% wt. to 0.4% wt. iron, plus inevitable impurities,   a carbon content controlled to lie in the range 30 ppm to 180-ppm,   a silicon content in the range 10 ppm to 120 ppm, and   an oxygen content in the range 600 ppm to 1800 ppm, with the balance zirconium.   
     
     
       10. A tube according to claim 9, wherein the alloy is in recrystallized state. 
     
     
       11. A tube according to claim 9, wherein the alloy is in relaxed state. 
     
     
       12. A tube according to claim 9, wherein the alloy has set contents: 0.9 wt. % to 1.1 wt. % niobium, 0.25 wt. % to 0.35 wt. % tin, and 0.2 wt. % to 0.3 wt. % iron.