Production and Properties
Commercial non-nuclear grade zirconium typically contains 1–5% of hafnium, whose neutron absorption cross-section is 600x that of zirconium. Hafnium must therefore be almost entirely removed (reduced to < 0.02% of the alloy) for reactor applications.
Zirconium and zinc are found in magnesium alloys used in plane, car and spacecraft construction. Zirconium is used to lower the metal grain size, increasing the metal’s hardness.
Nuclear-grade zirconium alloys contain more than 95% Zr, and therefore most of their properties are similar to those of pure zirconium. The absorption cross section for thermal neutrons is 0.18 barn for zirconium, which is much lower than that for such common metals as iron (2.4 barn) and nickel (4.5 barn). The composition and the main applications of common reactor-grade alloys are summarized below. These alloys contain less than 0.3% of iron and chromium and 0.1–0.14% oxygen.
| Alloy | Sn, % | Nb, % | Vendor (country) |
Component | Reactor type |
|---|---|---|---|---|---|
| Zircaloy 2 | 1.2–1.7 | – | All vendors | Cladding, structural components | BWR, CANDU |
| Zircaloy 4 | 1.2–1.7 | – | All vendors | Cladding, structural components | BWR, PWR, CANDU |
| ZIRLO | 0.7–1 | 1 | Westinghouse | Cladding | PWR |
| Zr Sponge | – | – | Japan and Russia | Cladding | BWR |
| ZrSn | 0.25 | – | Westinghouse | Cladding | BWR |
| Zr2.5Nb | – | 2.4–2.8 | – | Pressure tube | CANDU |
| E100 | – | 0.9–1.1 | Russia | Cladding | RBMK |
| E125 | – | 2.5 | Russia | Pressure tube | RBMK |
| E635 | 0.8–1.3 | 0.8–1 | Russia | Structural components | RBMK |
| M5 | – | 0.8–1.2 | Areva | Cladding, structural components | PWR |
*ZIRLO stands for zirconium low oxidation.
Read more about this topic: Zirconium Alloy
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