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Zirconium alloys with improved corrosion resistance and method for fabricating zirconium alloys with improved corrosion

a zirconium alloy and corrosion resistance technology, applied in the field of zirconium based alloys, can solve the problems of increasing alloy corrosion, increasing alloy corrosion, and increasing the thickness of the outer layer of non-protective materials, so as to improve the corrosion resistance of welds, improve the chemistry of alloys, and improve the corrosion resistance.

Inactive Publication Date: 2006-11-02
WESTINGHOUSE ELECTRIC CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0013] Accordingly, an object of the present invention is to provide zirconium alloys with improved corrosion resistance through improved alloy chemistry, improved weld corrosion resistance, and improved method of formation of alloys having reduced intermediate anneal temperatures during formation of the alloys.
[0016] It is a further object of the present invention to provide a zirconium based alloy characterized by increased weld corrosion resistance, wherein the increased weld corrosion resistance is resultant from the addition of 0.05 to 0.5 weight percent chromium.

Problems solved by technology

There have been increased demands on such nuclear core components, in the form of longer required residence times and higher coolant temperatures, both of which cause increase alloy corrosion.
Corrosion of the alloys in reactors is further complicated by the presence of an intense radiation field which may affect each step in the corrosion process.
Eventually, the process results in a relatively thick outer layer of non-protective, porous oxide.
However, the in-reactor corrosion of zirconium alloys is an extremely complicated, multi-parameter process.
No single theory has yet been able to completely define it.
However, Garzarolli does not disclose an alloy that had both niobium and tin, only one or the other.
A further issue in nuclear reactors is corrosion of welds utilized in a nuclear fuel assembly.
The weld connecting the end caps to the cladding, however, generally exhibits corrosion to an even greater extent than the cladding itself, usually by a factor of two over non-welded metal.
Rapid corrosion of the weld creates an even greater safety risk than the corrosion of non-welded material, and its protection has previously been ignored.

Method used

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  • Zirconium alloys with improved corrosion resistance and method for fabricating zirconium alloys with improved corrosion
  • Zirconium alloys with improved corrosion resistance and method for fabricating zirconium alloys with improved corrosion
  • Zirconium alloys with improved corrosion resistance and method for fabricating zirconium alloys with improved corrosion

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first embodiment

[0049] the present invention is a zirconium alloy having, by weight percent, about 0.6-1.5% Nb; 0.05-0.4% Sn, 0.01-0.1% Fe, 0.02-0.3% Cu, 0.1-0.3% V, 0-0-0.5% Cr and at least 97% Zr including impurities, hereinafter designated as Alloy X1. This embodiment, and all subsequent embodiments, should have no more than 0.50 wt. % additional other component elements, preferably no more than 0.30 wt. % additional other component elements, such as nickel, chromium, carbon, silicon, oxygen and the like, and with the remainder Zr. Chromium is an optional addition to Alloy X1. Wherein chromium is added to Alloy X1, the alloy is hereinafter designated as Alloy X1+Cr.

[0050] A preferred composition of Alloy X1 alloy has weight percent ranges for the alloy with about 1.0% Nb; 0.3% Sn, 0.05% Fe, 0.18% V, 0.12% Cu, and at least 97% Zr. A preferred composition of Alloy X1+Cr has weight percent ranges for the alloy with about 1.0% Nb; 0.3% Sn, 0.05% Fe, 0.18% V, 0.12% Cu, 0.2% Cr and at least 97% Zr.

[0...

second embodiment

[0055] the present invention is a zirconium alloy having, by weight percent, about, about 0.6-1.5% Nb; 0.01-0.1% Fe, 0.02-0.3% Cu, 0.15-0.35% Cr and at least 97% Zr, hereinafter designated as Alloy X4. A preferred composition of Alloy X4 has weight percent ranges for the alloy with about 1.0% Nb, about 0.05% Fe, about 0.25% Cr, about 0.08% Cu, and at least 97% Zr.

[0056] The preferred Alloy X4 was fabricated into tubing and its corrosion rate was compared with the corrosion rate of Standard ZIRLO. Alloy X4 and ZIRLO were each tested for long term corrosion resistance in 680° F. water. Alloy X4, ZIRLO 1 and ZIRLO 2 tubing were placed in a long term 680° F. water autoclave test for a period of about 250 days, wherein Alloy X4 was the preferred embodiment of Alloy X4, ZIRLO 1 comprised, by weight percentage, 0.89 Nb, 0.94 Sn, 0.09 Fe, remainder Zr, and ZIRLO 2 comprised 0.97 Nb, 0.97 Sn, 0.11 Fe, remainder Zr. The tubing was measured for weight gain rates, wherein the weight gain is att...

third embodiment

[0057] the present invention is a zirconium alloy having, by weight percent, about 0.2-1.50% Nb; 0.05-0.4% Sn, 0.25-0.45% Fe, 0.15-0.35% Cr, 0.01-0.1% Ni, and at least 97% Zr, hereinafter designated as Alloy X5. This composition should have no more than 0.5 wt. % additional other component elements, preferably no more than 0.3 wt. % additional other component elements, such as carbon, silicon, oxygen and the like, and with the remainder Zr.

[0058] A preferred composition of Alloy X5 has weight percent values for the alloy with about 0.7% Nb; about 0.3% Sn. about 0.35% Fe, about 0.25% Cr, about 0.05% Ni, and at least 97% Zr. Hereinafter, this alloy will be referred to as the first embodiment of Alloy X5.

[0059] The preferred embodiment of Alloy X5 was fabricated into tubing and its corrosion rate was compared to that of a series of alloys likewise fabricated into tubing. As shown in Table 4, Alloy A, a low Nb-high Sn predecessor of Alloy X5 (U.S. Pat. No. 5,254,308 having chemical com...

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Abstract

Articles, such as tubing or strips, which have excellent corrosion resistance to water or steam at elevated temperatures, are produced from alloys having 0.2 to 1.5 weight percent niobium, 0.01 to 0.45 weight percent iron, at least one additional alloy element selected from 0.02 to 0.8 weight percent tin, 0.05 to 0.5 weight percent chromium, 0.02 to 0.3 weight percent copper, 0.1 to 0.3 weight percent vanadium, 0.01 to 0.1 weight percent nickel, the balance at least 97 weight percent zirconium, including impurities, wherein the alloy may be fabricated from a process of forging the zirconium alloy into a material, beta quenching the material, forming the material by extruding or hot rolling the material, cold working the material with one or a multiplicity of cold working steps, wherein the cold working step includes cold reducing the material and annealing the material at an intermediate anneal temperature of 960°-1105° F., and final working and annealing of the material. The articles formed also show improved weld corrosion resistance with the addition of chromium.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] The instant application claims priority from Provisional Application No. 60 / 555,600 filed Mar. 23, 2004, and Provisional Application Nos. 60 / 564,416, 60 / 564,417 and 60 / 564,469, each filed Apr. 22, 2004, the disclosures of all of which are incorporated herein by reference.FIELD OF THE INVENTION [0002] The present invention generally relates to a zirconium based alloy usable for the formation of strips and tubing for use in nuclear fuel reactor assemblies and a method for making same. Specifically, the invention relates to zirconium based alloys that exhibit improved corrosion resistance in water based reactors under elevated temperatures, and a method of forming the alloys that increases corrosion resistance by decreasing intermediate anneal temperatures. The invention further relates to zirconium based alloys that include the addition of the alloying element chromium to improve weld corrosion resistance. BACKGROUND OF THE INVENTION [000...

Claims

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Application Information

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IPC IPC(8): C22F1/18C22C16/00
CPCC22C16/00Y02E30/40G21C3/07Y02E30/30
Inventor COLBURN, DAVIDCOMSTOCK, ROBERTCOOK, TERRENCEDAHLBACK, MATSFOSTER, JOHN P.GARDE, ANANDJOURDAIN, PASCALKESTERSON, RONALDMCCLARREN, MICHAELNUHFER, LYNNPARTEZANA, JONNAYUEH, KENNETHBOSHERS, JAMES A.FILE, PENNEY
Owner WESTINGHOUSE ELECTRIC CORP
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