To mitigate the risk of stress corrosion cracking in the reactors at Wolf Creek Generating Station and Ameren Missouri Callaway Energy Center, AZZ|WSI contracted Merrick to design a crane that could deploy water jet peening (WJP) tools to help relieve stress, particularly in nuclear reactor nozzle welds.

Mitsubishi Heavy Industries has used cranes on reactors in Japan that connect to reactors’ infrastructure, but AZZ|WSI did not want its crane to connect to reactor infrastructure at all and requested a first-of-its-kind approach. Merrick designed the specialty crane to lower, position and support two WJP tools—each the size and mass of a small car—into the reactor vessel during an outage. Once erected, the crane sits above the reactor vessel and provides a stable platform.

The crane system consists of two alignment beams, two fixed walkways, two gantry assemblies and two crane truss assemblies. The crane design was required to have substantial mass and adequate center of gravity to mitigate the potential for overturning or sliding. The main girders required removable extensions to fit inside 30-ft shipping containers while still being capable of spanning across the 32-ft reactor pool.

The crane had to be used repeatedly and deployed at multiple reactor sites. Designers aimed for mobility, modularity and selfdeployment. The team incorporated design features such as hinged and folding systems, integral drives and modular interconnecting structures.

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