Zirlo

ZIRLO is a zirconium-based alloy used primarily for nuclear fuel rod cladding in light-water reactors. Developed by Westinghouse Electric Company, it was introduced as an improved alternative to traditional Zircaloy alloys, offering lower neutron absorption and enhanced performance in high-temperature water environments.

The alloy contains zirconium with small additions of niobium, iron, and chromium, and it has relatively low tin content. The niobium component and the reduced tin help improve corrosion resistance, strength, and resistance to hydrogen uptake during irradiation, contributing to better dimensional stability and safety margins in reactor operations.

Applications and use: ZIRLO is employed mainly as fuel cladding for fuel rods in pressurized water reactors and is used inWestinghouse fuel assemblies. Its design aims to maintain ductility and fracture resistance under irradiation while reducing corrosion and hydrogen-related issues over the fuel lifetime.

Context and variants: ZIRLO is part of a family of zirconium alloys that compete with other cladding materials such as Zircaloy variants and M5. Its adoption reflects industry goals to extend fuel cycles, improve reliability, and optimize performance under the conditions of high-temperature water chemistry and neutron flux.

Safety and performance notes: The behavior of ZIRLO depends on reactor operating conditions, including coolant chemistry, temperature, and irradiation history. Ongoing research and quality control in manufacturing ensure cladding performance meets stringent nuclear-grade standards.