Which non-ferrous alloy family is widely used in nuclear reactors for cladding due to low neutron absorption?

• A. Zirconium-based alloys (Zircalloys).
• B. Copper-based alloys.
• C. Aluminum alloys.
• D. Magnesium alloys.

Answer: (A)

Selecting fuel cladding hinges on keeping neutron absorption very low while the material remains strong and resistant to corrosion under reactor coolant conditions. Zirconium-based alloys excel here: they have among the lowest neutron absorption cross-sections of common structural metals, so they don’t waste precious neutrons that should be causing fission. At the same time, they form a protective oxide layer in hot water, resist corrosion, and retain mechanical strength and dimensional stability under irradiation and high temperatures. This combination—minimal neutron capture, good corrosion resistance in reactor coolant, and solid irradiation stability—makes zirconium-based alloys the preferred cladding material in most commercial light-water reactors.

Copper-based alloys would capture more neutrons and corrosion behavior under reactor conditions is less favorable; aluminum alloys, while lightweight, have higher neutron absorption and can be less robust under irradiation; magnesium alloys are highly reactive and not suitable for long-term corrosion resistance in coolant environments.