Niobium-containing zirconium alloy for nuclear fuel claddings

Details Niobium-containing zirconium alloy for nuclear fuel claddings Niobium-containing zirconium alloy for nuclear fuel claddings

2000-03-08

2001-07-17

Wyszomierski, George (Department: 1742)

Alloys or metallic compositions

Zirconium or hafnium base

C420S423000

Reexamination Certificate

active

06261516

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to the compositions of niobium-containing zirconium (Zr) alloy with superior corrosion resistance. In particular, the present invention relates to the Zr alloys for nuclear fuel claddings.
DESCRIPTION OF THE PRIOR ART
Zr alloys have been widely used as fuel rod cladding and structural elements of nuclear reactor core owing to its low neutron absorption cross section, excellent corrosion resistance and good mechanical strength. Niobium (Nb) is well-known to improve the mechanical strength and the creep characteristics in addition to improve the corrosion resistance and to decrease the hydrogen uptake. Therefore, the recently-developed Zr alloys for nuclear fuel cladding are characterized as comprising Nb. However, the heat treatment condition needs to be optimized because the excess amount of Nb in Zr alloys will affect the corrosion resistance and the hydrogen uptake depending on the processing condition of the alloy.
As the prior art of Nb-containing zirconium alloy for nuclear fuel cladding, U.S. Pat. No.5,254,308 discloses a Zr alloy in which the amount of Sn was reduced and Nb and Fe was contained to maintain the strength of the alloy. The alloy comprises Sn in a range of 0.45 to 0.75 wt. % (typically 0.6 wt. %), Fe in a range of 0.4 to 0.53 wt. % (typically 0.45 wt. %), Cr in a range of 0.2 to 0.3 wt. % (typically 0.25 wt. %), Nb in a range of 0.3 to 0.5 wt. % (typically 0.45 wt. %), Ni in a range of 0.012 to 0.03 wt. % (typically 0.02%), Si in a range of 50 to 200 ppm (typically 100 ppm) and 0 in a range of 1000-2000 ppm (typically 1600 ppm). Also the ratio of Fe/Cr was 1.5 and the amount of Nb was determined according to the amount of Fe, which affects to the hydrogen uptake. The good corrosion resistance and strength of the alloy was obtained by controlling the amount of Ni, Si, C and O.
U.S. Pat. No. 5,334,345 discloses the alloys, which comprise Sn in a range of 1.0 to 2.0 wt. %, Fe in a range of 0.07 to 0.70 wt. %, Cr in a range of 0.05 to 0.15 wt. %, Ni in a range of 0.16 to 0.40 wt. %, Nb in a range of 0.015 to 0.30 wt. % (typically 0.015 to 0.20 wt. %), Si in a range of 0.002 to 0.05 wt. % (typically 0.015 to 0.05 wt. %) and 0 in a range of 900 to 1600 ppm, for improving the corrosion resistance and the hydrogen-uptake resistance.
U.S. Pat. No. 5,336,690, wherein the amount of Sn, N and Nb was mainly controlled, discloses the alloys which comprise Sn in a range of 0 to 1.5 wt. % (typically 0.6 wt. %), Fe in a range of 0 to 0.24 wt. % (typically 0.12 wt. %), Cr in a range of 0 to 0.15 wt. % (typically 0.10 wt. %), N in a range of 0 to 2300 ppm, Si in a range of 0 to 100 ppm (typically 100 ppm), 0 in a range of 0 to 1600 ppm (typically 1200 ppm) and Nb in a range of 0 to 0.5 wt. % (typically 0.45 wt. %).
The Zr alloy disclosed in U.S. Pat. No. 5,211,774 was developed to improve the properties in ductility, creep strength and corrosion resistance under neutron irradiation environment, comprises Sn in a range of 0.8 to 1.2 wt. %, Fe in a range of 0.2 to 0.5 wt. % (typically 0.35 wt. %), Cr in a range of 0.1 to 0.4 wt. % (typically 0.25 wt. %), Nb in a range of 0 to 0.6 wt. %, Si in a range of 50 to 200 ppm (typically 50 ppm) and O in a range of 90 to 1800 ppm (typically 1600 ppm). It is the objective to reduce the hydrogen uptake and the variation of the corrosion resistance with variations in the processing condition of the alloy, by controlling the amount of Si.
EP No. 195,155 disclosed the Zr alloys which comprise Sn in a range of 0.1 to 0.3 wt. %, Fe in a range of 0.05 to 0.2 wt. %, Nb in a range of 0.05 to 0.4 wt. %, Cr, Ni or Cr and Ni in a range of 0.03 to 0.1 wt. %, and a duplex-type fuel cladding. In this alloy, the amount of Fe+Cr+Ni cannot exceed up to 0.25 wt. % and O was contained in a range of 300 to 1200 ppm.
EP No. 468,093 or U.S. Pat. No. 5,080,861 discloses a Zr alloy comprising Nb in a range of 0 to 0.6 wt. %, Sb in a range of O to 0.2 wt. %, Te in a range of 0 to 0.2 wt. %, Sn in a range of 0.5 to 1.0 wt. %, Fe in a range of 0.18 to 0.24 wt. %, Cr in a range of 0.07 to 0.13 wt. %, 0 in a range of 900 to 2000 ppm, Ni in a range of 0 to 70 ppm and C in a range of 0 to 200 ppm, for improving the corrosion resistance in high burn-up. In this alloy, the size of precipitate was limited 1200 to 1800 Å, and the alloy may include up to 0.2 wt. % of Bi (Bismuth) instead of Te (Tellurium) or Sb (Antimony).
The Zr alloy with similar composition to that of the above patent was suggested in EP No. 345,531. This alloy comprised Nb in a range of 0 to 0.6 wt. %, Mo in a range of 0 to 0.1 wt. %, Sn in a range of 1.2 to 1.7 wt. %, Fe in a range of 0.07 to 0.24 wt. %, Cr in a range of 0.05 to 0.13 wt. %, Ni in a range of 0 to 0.08 wt. % and O in a range of 900 to 1800 ppm.
The Zr alloy of EP No. 532,830 has the improved corrosion resistance, the stability under irradiation, the mechanical strength and the creep resistance. It comprises Nb in a range of 0 to 0.6 wt. %; Sn in a range of 0.8 to 1.2 wt. %; Fe in a range of 0.2 to 0.5 wt. % (typically 0.35 wt. %); Cr in a range of 0.1 to 0.4 wt. % (typically 0.25 wt. %); Si in a range of 50 to 200 ppm (typically 100 ppm); and O in a range of 900 to 1800 ppm (typically 1600 ppm).
The Zr alloy of FR No. 2,624,136, wherein Nb and V are contained, comprises Fe in a range of 0.1 to 0.35 wt. %, V in a range of 0.1 to 0.4 wt. %, O in a range of 0.05 to 0.3 wt. %, Sn in a range of 0 to 0.25 wt. % and Nb in a range of 0 to 0.25 wt. % and the ratio of V/Fe is more than 0.5. Also this patent discloses the optimum manufacturing process of the alloy.
JP No. 62,180,027 discloses the Zr alloy, which comprises Nb in a range of 1.7 to 2.5 wt. %, Sn in a range of 0.5 to 2.2 wt. %, Fe in a range of 0.04 to 1.0 wt. % for improving the mechanical strength and the nodular corrosion resistance. In this alloy, the content of Fe and Mo was limited to be from 0.2 to 1.0 wt. %.
JP No. 2,213,437 discloses a Nb-containing alloy besides Zr—Sn—Fe—V alloy to improve the nodular corrosion resistance. The alloy comprises Zr alloy in a range of 0.25 to 1.5 wt. %, Nb in a range of 0.15 to 1.0 wt. % and Fe, and Zr alloy in a range of 0.25 to 1.5 wt. %, Nb in a range of 0.5 to 1.0 wt. %, Sn in a range of 0.05 to 0.15 wt. % and Ni.
JP No. 62,207,835 discloses Zr—Nb—Sn based alloy, which comprises Zr alloy in a range of 0.2 to 2.0 wt. %, Nb in a range of 0.5 to 3.0 wt. %, Sn in a range of 900 to 2500 ppm and O.
JP No. 62,297,449 discloses the alloy composition which comprises Nb in a range of 1 to 2.5 wt. %, Sn in a range of 0.5 to 2.0 wt. %, Mo in a range of 0.1 to 1.0 wt. % and Mo+Nb in a range of 1.5 to 2.5 wt. % for the improvement of corrosion resistance, ductility and strength and a process by the solution treatment in a &agr;+&bgr; or &bgr; region.
The Zr alloy with similar composition to that of the above patent except containing Fe was suggested in JP No. 62,180,027. The alloy comprises Nb in a range of 1.7 to 2.5 wt. %, Sn in a range of 0.5 to 2.2 wt. %, Fe in a range of 0.04 to 1.0 wt. % and Mo in a range of 0.2 to 1.0 wt. %, wherein the total amount of Fe and Mo is in a range of 0.2 to 1.0 wt. %.
U.S. Pat. Nos. 4,863,685, 4,986,975, 5,024,809 and 5,026,516 disclose the Zr alloys which comprise Sn in a range of 0.5 to 2.0 wt. %, and other solute elements in a range of about 0.5 to 1.0 wt. %. The said alloys contain O in a range of 0.09 to 0.16 wt. %. More particularly, the alloy disclosed in U.S. Pat. No. 4,863,685 comprises other solute element, for example, Mo, Te and their mixture, or Nb—Te, Nb—Mo in addition to Sn. The alloy composition disclosed in U.S. Pat. No. 4,986,975 comprises solute elements such as Cu, Ni, Fe, etc. in a range from 0.24 to 0.40 wt. %, and Cu should be contained more than 0.05 wt. % in the alloy.
U.S. Pat. Nos. 5,024,809 and 5,026,516 disclose the alloys, comprising Mo, Nb, Te etc. as solute elements. And the amount was limited in a range of 0.5 to 1.0 wt. % which was the same as that of U.S. Pat. No. 4,863,685. Bi or Bi+Sn was added in a r

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