EP0287889B1 - Bismut enthaltende, korrosionsbeständige Zirkonlegierungen - Google Patents
Bismut enthaltende, korrosionsbeständige Zirkonlegierungen Download PDFInfo
- Publication number
- EP0287889B1 EP0287889B1 EP88105454A EP88105454A EP0287889B1 EP 0287889 B1 EP0287889 B1 EP 0287889B1 EP 88105454 A EP88105454 A EP 88105454A EP 88105454 A EP88105454 A EP 88105454A EP 0287889 B1 EP0287889 B1 EP 0287889B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- corrosion
- alloys
- bismuth
- weight percent
- amount
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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Classifications
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C16/00—Alloys based on zirconium
Definitions
- the present invention relates to zirconium-based alloys suitable for use in nuclear reactor service, and more specifically for use in the cladding of fuel elements.
- Zirconium-based alloys have long been used in the cladding of fuel elements in nuclear reactors. A desirable combination is found in zirconium by virtue of its low thermal neutron cross-section and its generally acceptable level of resistance to corrosion in a boiling water reactor environment.
- Zircaloy 2 a Zr-Sn-Ni-Fe-Cr alloy, has enjoyed widespread use and continues to be used at present in nuclear reactor applications. This alloy has provided adequate performance in reactor service, but also possesses some deficiencies which have prompted further research to find materials which would provide improved performance.
- Zircaloy 4 was one alloy developed as a result of that research. This alloy essentially eliminates the Ni (0.007% max. wt. percent) from a Zircaloy 2-type alloy.
- Zircaloy 4 was developed as an improvement to Zircaloy 2 to reduce problems with hydriding, which causes Zircaloy 2 to become brittle when cooled to ambient temperatures (e.g. when the reactor is shut down) after absorbing hydrogen at higher temperatures.
- the Zircaloy alloys are among the best corrosion resistant materials when tested in water at reactor operating temperatures (approx. 290°C) in the absence of the radiation from the nuclear fission reaction.
- the corrosion rate under those conditions is very low and the corrosion product is a uniform, tightly adherent, black ZrO2 film/layer.
- the Zircaloy is irradiated and is also exposed to radiolysis products present in reactor water.
- the corrosion resistance properties of Zircaloy deteriorate under these conditions and the corrosion rate thereof is accelerated.
- the deterioration under actual reactor conditions of the corrosion resistance properties of Zircaloy is not manifested in merely an increased uniform rate of corrosion. Rather, in addition to the black ZrO2 layer formed, a localized, or nodular corrosion phenomenon has been observed especially in boiling water reactors (BWR). In addition to producing an accelerated rate of corrosion, the corrosion product of the nodular corrosion reaction is a highly undesirable white ZrO2 bloom which is less adherent and lower in density than the black ZrO2 layer.
- the increase rate of corrosion caused by the nodular corrosion reaction will be likely to shorten the service life of the tube cladding, and also this nodular corrosion will have a detrimental effect on the efficient operation of the reactor.
- the white ZrO2 being less adherent, may be prone to spalling or flaking away from the tube into the reactor water.
- the nodular corrosion product does not spall away, a decrease in heat transfer efficiency through the tube into the water is created when the nodular corrosion proliferates and the less dense white ZrO2 covers all or a large portion of a tube.
- any new alloy which would be considered as a suitable alternate or replacement for the Zircaloy alloys must not only be less susceptible than the Zircaloy alloys to nodular corrosion, but should maintain acceptable uniform corrosion rates, to ensure sufficient service life.
- the present invention relates to zirconium-based alloys which, in one preferred embodiment, comprising 0.5 to 2.5 weight percent bismuth, 0.5-1.0 weight percent of a solute composed of a member selected from the group consisting of molybdenum, niobium, tellurium and mixtures thereof, optionally 0.09 to 0.19 weight percent of oxygen and the balance being zirconium.
- the corrosion resistant alloys comprise 0.5 to 2.5 weight percent of bismuth, 0.3-1.0 weight percent of a solute composed of tellurium, and the balance zirconium.
- the amount of bismuth is in the range of 0.7-2.0% by weight of the alloy.
- the corrosion-resistant alloys comprise 0.5 to 2.5 weight percent of a mixture of tin and bismuth, 0.5-1.0 weight percent of a solute composed of a member selected from the group consisting of molybdenum, niobium, tellurium and mixtures thereof, and the balance being zirconium.
- the alloys comprise 0.5-2.5 weight percent of a mixture of tin and bismuth, a solute composed of tellurium and the balance zirconium.
- the amount of the tin-bismuth mixture is in the range of 2.0-2.2 percent by weight.
- the alloy will further comprises 0.09 to 0.16 weight percent of oxygen.
- the alloy comprises 0.7-2.0 weight percent bismuth, a solute composed of niobium and molybdenum, the amount of niobium being substantially 0.5% by weight, the amount of molybdenum bring substantially 0.5% by weight, and the balance zirconium.
- the alloy comprises 0.7-2.0 weight percent bismuth, a solute composed of niobium and molybdenum, the amount of niobium being substantially 0.3 weight percent, the amount of molybdenum being substantially 0.3 weight percent, and the balance zirconium.
- the alloy comprises 0.7-2.0 weight percent bismuth, a solute composed of niobium and tellurium, the amount of niobium being substantially 0.3 weight percent, the amount of tellurium being substantially 0.3 weight percent, and the balance zirconium.
- the alloy comprises 0.7-2.0 weight percent bismuth, a solute composed of molybdenum, tellurium and niobium, the amount of each being substantially 0.2 weight percent, and the balance zirconium.
- the alloy comprises 2.0-2.2 weight percent of a mixture of tin and bismuth, a solute composed of niobium and molybdenum, the amount of niobium being substantially 0.3 weight percent, the amount of molybdenum being substantially 0.3 weight percent, and the balance zirconium.
- the alloy comprises 2.0-2.2 weight percent of a mixture of tin and bismuth, a solute composed of niobium and tellurium, the amount of niobium being substantially 0.3 weight percent, the amount of tellurium being substantially 0.3 weight percent, and the balance zirconium.
- the alloy comprises 2.0-2.2 weight percent of a mixture of tin and bismuth, a solute composed of molybdenum, tellurium and niobium, the amount of each being substantially 0.3 weight percent, and the balance zirconium.
- These alloys provide increased resistance to nodular corrosion in high pressure and temperature steam testing, and will maintain acceptable uniform corrosion rates in water and steam tests.
- the alloys of the present invention will provide sufficient resistance to uniform corrosion to be considered for nuclear reactor service.
- the alloys of the present invention have demonstrated improved resistance to nodular corrosion.
- the thermal neutron cross-section of the element is preferably relatively low to permit products of the fission reaction to easily pass through the fuel rods thereby allowing the boiling water reactor operate efficiently.
- the cost of the material should be taken into account, and must not be prohibitively high.
- the ease or difficulty with which an alloy containing the element or elements and zirconium can be produced must also be considered. It is further desired that the element or elements will enhance the corrosion resistance properties of the zirconium under actual or simulated boiling water reactor conditions.
- the thermal neutron cross-section of an element is generally a known property of the element if it has ever come under consideration for use in a nuclear reactor.
- the costs of the materials can be ascertained from historic price data, with extrapolation if required.
- the alloying process of the alloys of the present invention is similar to conventional methods for alloying zirconium and thus ease of alloying is fairly predictable.
- the alloying is accomplished preferably by arc melting a zirconium billet having a suitable amount of the alloying metals encased in a hollow portion of the billet. This molten metal is then cast as an alloy billet, which will then be subject to finishing processes to produce final shapes.
- Bismuth also an a-stabilizer in zirconium, has received little attention from the nuclear materials community. It has been discovered in the present invention that when bismuth, or a combination of bismuth and tin are used in a zirconium-based alloy, two advantages are realized. First, bismuth has an exceptionally low thermal neutron cross-section, lower even than zirconium and tin, and much lower than most other elements commonly alloyed with zirconium.
- zirconium-bismuth and zirconium-tin-bismuth alloys produces alloys possessing acceptable uniform corrosion rates as well as improved resistance to nodular corrosion. More specifically, the addition of an element or mixture of elements, termed collectively herein as a solute portion of the alloy, selected from the group consisting of niobium, tellurium and molybdenum, making up 0.5-1.0% by weight, or if tellurium alone is used, making up 0.3-1% by weight of an alloy also containing 0.5% to 2.5% by weight of bismuth, or in the alternative containing 0.5 to 2.5% by weight of a tin-bismuth mixture, the balance being zirconium, produces alloys which show substantial improvement in nodular corrosion resistance compared to that of Zircaloy 2.
- an element or mixture of elements termed collectively herein as a solute portion of the alloy, selected from the group consisting of niobium, tellurium and molybdenum, making up 0.5-1.0% by weight,
- alloys having compositions in these ranges also possess the other desired features previously mentioned; i.e. , low thermal neutron cross-section, and acceptable cost and ease of alloying. These alloys will also contain the conventional impurities found in sponge zirconium and zirconium alloys.
- the alloys of the present invention will also optionally contain from 0.09 to 0.16 weight percent of oxygen.
- Most commercial grade sponge zirconium which would be used in making alloys such as the ones in the present invention will contain small amounts of oxygen, roughly on the order of 800-1300 parts per million. In some instances, it will be desirable to increase the concentration of oxygen in the alloy. Adding oxygen is one way to increase room temperature yield strength. Thus, the alloys of the present invention may be produced with or without the addition of oxygen, as this will have little or no effect on the corrosion resistance of the alloys.
- the alloying elements which make up the solute portion are most effective in these alloys at a total solute concentration of 0.6-0.7 weight percent of the alloy. Solute concentrations ranging from as low as 0.3 weight percent (when tellurium alone is used) to as high as 1.0 weight percent have been tested and have been shown to exhibit superior resistance to nodular corrosion, compared to the performance of Zircaloy 2.
- Table 1 lists several alloys which employ bismuth alone as an ⁇ -stabilizing element and one alloy which employs a tin-bismuth mixture as stabilizing elements, with various solute combinations in accordance with the present invention, along with three entries at the bottom of the table which are Zircaloy 2 alloys in three (3) different heat treatment states. These alloys were tested in water containing 8 ppm oxygen, at 288°C and 10.33 MPa (1500 psig), conditions similar to a reactor operating temperature and pressure (minus a radiation source), to evaluate the resistance of these alloys to uniform corrosion.
- Table 2 reports the results of tests conducted to determine the susceptibility to nodular corrosion of alloys containing zirconium, bismuth, and a solute according to the present invention. Tests were conducted on samples of the alloys in the as-cast form with no special heat treatment as well as on samples which were annealed at 750°C for 48 hours. This heat treatment, as previously mentioned, is one which essentially strips the Zircaloy 2 alloy of its resistance to nodular corrosion in the laboratory steam tests. Additional tests were conducted on samples in which cast buttons were cold rolled to a 2.54 mm (0.1 inch) thickness and subsequently heat treated at either 750°C for 48 hours or at 920°C for three hours.
- Table 3 reports the results of tests performed to determine the susceptibility to nodular corrosion of alloys containing zirconium, a mixture of bismuth and tin, and a solute according to the present invention. These tests were conducted on samples of the alloys in plate form 2.54 mm (0.1 inch thickness). The alloys were tested in both a cold-worked state, that is, no heat treatment being performed subsequent to the plate-rolling procedure, and an annealed state wherein the samples were annealed at 750°C for 48 hours after being rolled into plate.
- test conditions used in Tables 2 and 3 were those which induce, in the laboratory, the formation of the nodular corrosion product on Zircaloy alloys (with a 750°C/48 hour anneal) like that found on Zircaloy alloys after being used in reactor service.
- weight gains seen in the annealed Zircaloy are on the order of several thousand milligrams per square decimeter.
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Powder Metallurgy (AREA)
- Preventing Corrosion Or Incrustation Of Metals (AREA)
Claims (17)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US4150887A | 1987-04-23 | 1987-04-23 | |
US41508 | 1987-04-23 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0287889A1 EP0287889A1 (de) | 1988-10-26 |
EP0287889B1 true EP0287889B1 (de) | 1991-04-10 |
Family
ID=21916887
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP88105454A Expired - Lifetime EP0287889B1 (de) | 1987-04-23 | 1988-04-06 | Bismut enthaltende, korrosionsbeständige Zirkonlegierungen |
Country Status (6)
Country | Link |
---|---|
EP (1) | EP0287889B1 (de) |
JP (1) | JPH0660364B2 (de) |
DE (1) | DE3862338D1 (de) |
ES (1) | ES2021406B3 (de) |
FI (1) | FI86994C (de) |
TW (1) | TW223124B (de) |
Families Citing this family (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH02173235A (ja) * | 1988-12-27 | 1990-07-04 | Toshiba Corp | 耐食性ジルコニウム合金 |
US5026516A (en) * | 1989-05-25 | 1991-06-25 | General Electric Company | Corrosion resistant cladding for nuclear fuel rods |
US5190721A (en) * | 1991-12-23 | 1993-03-02 | General Electric Company | Zirconium-bismuth-niobium alloy for nuclear fuel cladding barrier |
US5790623A (en) * | 1997-03-25 | 1998-08-04 | Siemens Power Corporation | Composite cladding for nuclear fuel rods |
US5772798A (en) * | 1997-03-25 | 1998-06-30 | Siemens Power Corporation | High strength zirconium alloys containing bismuth |
US5768332A (en) * | 1997-03-27 | 1998-06-16 | Siemens Power Corporation | Nuclear fuel rod for pressurized water reactor |
DE69910899T2 (de) * | 1998-06-12 | 2004-07-08 | Framatome Anp, Inc. | Hochfeste Zirkonlegierungen enthaltend Wismut, Zinn und Niob |
US6511556B1 (en) * | 1998-06-12 | 2003-01-28 | Siemens Power Corporation | High strength zirconium alloys containing bismuth and niobium |
Family Cites Families (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2872310A (en) * | 1952-12-09 | 1959-02-03 | Harley A Wilhelm | Zirconium alloy |
JPS6350453A (ja) * | 1986-08-20 | 1988-03-03 | Hitachi Ltd | ジルコニウム基合金部材の製造法 |
-
1988
- 1988-03-22 TW TW077101875A patent/TW223124B/zh active
- 1988-04-06 EP EP88105454A patent/EP0287889B1/de not_active Expired - Lifetime
- 1988-04-06 ES ES88105454T patent/ES2021406B3/es not_active Expired - Lifetime
- 1988-04-06 DE DE8888105454T patent/DE3862338D1/de not_active Expired - Fee Related
- 1988-04-22 FI FI881897A patent/FI86994C/fi not_active IP Right Cessation
- 1988-04-22 JP JP63098491A patent/JPH0660364B2/ja not_active Expired - Lifetime
Also Published As
Publication number | Publication date |
---|---|
JPH0660364B2 (ja) | 1994-08-10 |
FI881897A (fi) | 1988-10-24 |
DE3862338D1 (de) | 1991-05-16 |
ES2021406B3 (es) | 1991-11-01 |
EP0287889A1 (de) | 1988-10-26 |
JPS63290234A (ja) | 1988-11-28 |
FI86994C (fi) | 1992-11-10 |
TW223124B (de) | 1994-05-01 |
FI86994B (fi) | 1992-07-31 |
FI881897A0 (fi) | 1988-04-22 |
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