Zircaloy, also incorrectly called zircalloy, is a group of high-zirconium alloys. One of the main uses of zircaloys is in nuclear technology, as zirconium has very low absorption cross-section of thermal neutrons and therefore it is frequently used as cladding of fuel rods in nuclear reactors. Zircaloy-2 and Zircaloy-4 contain about 1.5% of tin. Other alloying elements can be niobium, chromium, iron and nickel.

* Zircaloy-1 consists of zirconium with 2.5% tin. However its corrosion rate was increasing over time, and to counter this effect other elements had to be added.
* Zircaloy-2 (Zry-2) consist of 98.25 weight % zirconium with 1.45% tin, 0.10% chromium, 0.135% iron, 0.055% nickel and 0.01% hafnium. [http://iriaxp.iri.tudelft.nl/~leege/SCALE44/stdcmp.pdf Standard Comp. Library (Sect. M8) ] ] Other sources specify Zircaloy-2 as zirconium with 1.20-1.70% tin, 0.07-0.20% iron, 0.05-0.15% chromium, and 0.03-0.08% nickel, with tin content at lower and the iron/chromium/nickel content at the higher end of the specification. [ [http://www.wahchang.com/WahChang/pages/outlook/pdf/2001/q2/2Q2001_outlook.pdf] Dead link|date=March 2008]

* Zircaloy-4 (Zry-4) consists of 98.23 weight % zirconium with 1.45% tin, 0.21% iron, 0.1% chromium, and 0.01% hafnium.

The corrosion properties of Zircaloy-4 can be improved by adding small amount of nickel, resulting in nickel-doped Zircaloy-4, with significantly better resistance to nodular corrosion without worsening the uniform corrosion resistance and hydrogen absorption rate. [http://legal.european-patent-office.org/dg3/pdf/t000318eu1.pdf]

Reactor-grade zirconium alloys must be made of purified zirconium free of hafnium contamination, as hafnium has very high neutron absorption cross-section, 600 times higher than zirconium. Commercial zirconium naturally contains 1-5% of hafnium which has to be removed. This removal process is difficult (zirconium and hafnium are two of the most difficult elements to separate). Two main process are in use: liquid-liquid extraction, exploiting the difference of solubility of metal thiocyanates in methyl isobutyl ketone, used mainly in United States, and extractive distillation, used primarily in Europe. The resulting reactor-grade zirconium is about 10 times as expensive as the hafnium-contaminated commercial grade. The separated hafnium is used for control rods.

Zircaloy has a high affinity to hydrogen; absorption of hydrogen leads to hydrogen embrittlement and may lead to local or total fuel element failure and release of hot particles.

Zircaloy readily reacts with oxygen, forming a passivation layer. It is more corrosion-resistant and has better neutron transparency than austenitic steel. However the corrosion resistance may degrade significantly when some impurities (eg. more than 300 ppm of carbon or more than 40 ppm of nitrogen) are present. Corrosion resistance of zircalloys is enhanced by intentional development of thicker passivation layer of black lustrous zirconium oxide. Titanium nitride coating is sometimes used as well.

Other zirconium alloys are Zr705 with 5% of niobium, or reactor-grade Zr-5Nb with similar composition but hafnium-free, or 3Zi (97% Zirconium, 1% Aluminum, 1% Tin, and 1% Molybdenum, or zr97al1sn1mo1).

One of the many differences between Western and Soviet nuclear technology was the zirconium alloy composition. Reactors built with assistance of Western corporations used the zirconium-tin alloys, while reactors built with Soviet, Eastern Europe, or Chinese help used the zirconium-niobium ones.

In the past few years there has been significant development of (Zr- 1% Niobium) alloys which are claimed to have very low corrosion rates - these include E110 (Russian), Zirlo (Westinghouse), and M5 (Framatome-ANP).

Some zirconium alloys are biocompatible, and are used for implants.


Wikimedia Foundation. 2010.

Нужно решить контрольную?

Look at other dictionaries:

  • Zircaloy — (de l anglais Zirconium et « alloy » = alliage) est un nom générique et de marque donné à un groupe d alliages de zirconium (Solutions solides). « Crayon » constitué d un tube de zircaloy destiné à recevoir un empilement de… …   Wikipédia en Français

  • zircaloy — [zʉr′kə loi΄] n. 〚< Zircaloy Super Alpha, a trademark /span> ZIRC(ONIUM) + AL(L)OY〛 any of various alloys containing about 98% zirconium, 1.5% tin, etc., that are resistant to corrosion and high temperatures and are used to contain fuel in… …   Universalium

  • Zircaloy — [zʉr′kə loi΄] n. [< Zircaloy Super Alpha, a trademark < ZIRC(ONIUM) + AL(L)OY] any of various alloys containing about 98% zirconium, 1.5% tin, etc., that are resistant to corrosion and high temperatures and are used to contain fuel in… …   English World dictionary

  • Zircaloy — См. Циркалой Термины атомной энергетики. Концерн Росэнергоатом, 2010 …   Термины атомной энергетики

  • Zircaloy — ● Zircaloy nom masculin (nom déposé) Nom de divers alliages de zirconium et d autres métaux utilisés pour gainer le combustible des réacteurs nucléaires …   Encyclopédie Universelle

  • Zircaloy — Zirkalloy, auch Zirkaloy, Zircalloy oder Zircaloy, ist eine Metall Legierung, die zu mehr als 90% aus Zirconium besteht. Sie enthält außerdem geringe Mengen von Zinn, Eisen, Nickel und Chrom. Wegen seines geringen Einfangquerschnitts für… …   Deutsch Wikipedia

  • zircaloy — noun Any of a set of specialist alloys of zirconium Syn: zircalloy, zircoloid, Zry, zry …   Wiktionary

  • zircaloy — zir·ca·loy …   English syllables

  • zircaloy — …   Useful english dictionary

  • Nuclear meltdown — Three of the reactors at Fukushima I overheated, causing core meltdowns. This was compounded by hydrogen gas explosions and the venting of contaminated steam which released large amounts of radioactive material into the air.[1] …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”