Patent Number: 
Section: claims

1. A zirconium alloy for a nuclear fuel cladding comprising 1.1 wt % of niobium (Nb); at least two elements selected from the group consisting of tin (Sn), iron (Fe) and chromium (Cr); 0.05 wt % of copper (Cu); 0.12 wt % of oxygen (O); 0.01 wt % of silicon (Si) and a remaining amount of zirconium (Zr), in which, the amount of tin (Sn) being 0.2 wt %, the amount of iron (Fe) being 0.5 wt %, and the amount of chromium (Cr) being 0.1 to 0.2 wt %. 2. A method of preparing a zirconium alloy nuclear fuel cladding comprising:Step 1: manufacturing an ingot by vacuum arc remelting and then cooling the zirconium alloy comprising 1.1 wt % of niobium (Nb); at least two elements selected from the group consisting of tin (Sn), iron (Fe) and chromium (Cr); 0.05 wt % of copper (Cu); 0.12 wt % of oxygen (O); 0.01 wt % of silicon (Si) and a remaining amount of zirconium (Zr), in which, the amount of tin (Sn) being 0.2 wt %, the amount of iron (Fe) being 0.5 wt %, and the amount of chromium (Cr) being 0.1 to 0.2 wt %;Step 2: forging thus manufactured ingot in Step 1;Step 3: solution heat treating and cooling the forged ingot in Step 2;Step 4: hot processing by extruding the cooled ingot in Step 3;Step 5: initially heat treating the extruded shell in Step 4;Step 6: cold processing the heat treated and extruded shell in Step 5, the zirconium alloy nuclear fuel cladding being prepared by conducting intermediate heat treating in the middle of the cold processing; andStep 7: finally heat treating the thus prepared zirconium alloy nuclear fuel cladding to prepare a nuclear fuel cladding. 3. The method of preparing a zirconium alloy nuclear fuel cladding as set forth in claim 2, wherein the forging in Step 2 is conducted at a temperature of 1,000° C. to 1,200° C. 4. The method of preparing a zirconium alloy nuclear fuel cladding as set forth in claim 2, wherein the solution heat treating in Step 3 is conducted at a temperature of 1,000° C. to 1,200° C. for 10 to 40 minutes. 5. The method of preparing a zirconium alloy nuclear fuel cladding as set forth in claim 2, wherein the cooling in Step 3 is conducted to a temperature of 300° C. to 400° C., with a cooling rate of 300 to 400° C./s. 6. The method of preparing a zirconium alloy nuclear fuel cladding as set forth in claim 2, wherein the extrusion in Step 4 is conducted at a temperature of 600 to 640° C. 7. The method of preparing a zirconium alloy nuclear fuel cladding as set forth in claim 2, wherein the heat treating in Step 5 is conducted at a temperature of 570° C. to 610° C. for 2 to 4 hours. 8. The method of preparing a zirconium alloy nuclear fuel cladding as set forth in claim 2, wherein the intermediate heat treating in Step 6 is conducted at a temperature of 570° C. to 610° C. for 3 to 10 hours. 9. The method of preparing a zirconium alloy nuclear fuel cladding as set forth in claim 2, wherein the final heat treatment in Step 7 is conducted at a temperature of 470° C. to 580° C. for 1 to 100 hours.