When the new steam generators in Unit 2 at USA member Prairie Island were declared in-service on Dec. 16, 2013, it was the culmination of a project that was nearly seven years in the making. It began in 2006 with a contract with AREVA to manufacture the generators in Chalon St. Marcel, France. With that contract, the $280 million project was underway.

There was a lot of local excitement as the replacement steam generators arrived via barge up the Mississippi River after a trans-Atlantic voyage. From the river, the parts were placed in a specially constructed building where work began to prepare the equipment for installation.

Aside from the physical preparations, a Prairie Island team also met with NRC Region III officials to discuss the project’s oversight, scheduling and technical specifications. This information helped prepare NRC inspectors for a planned inspection of the generators.

The replacement steam generators have big shoes to fill. The old steam generators were among the oldest remaining in service in the world, demonstrating the outstanding operation and maintenance of them over their lifecycle, thanks to high standards in controlling chemistry, operations and maintenance.

Crowds gathered as the old steam generator components made their slow egress from containment, with the final section of the 22 old steam generator being removed from containment on Oct. 16. The new components started moving in shortly thereafter, with the components in place for welding by Oct. 30.

The welding task was massive, with two companies (PCI Energy Services and Chicago Bridge and Iron Company) working around the clock — both inside containment and in the remote welding truck stationed outside.

After the welds were done, radiography was successfully completed and the core was reloaded to commence final hydrostatic testing.

The core load was a success, and the plant moved from a “construction” mindset in containment to one that reminded all workers of the significant responsibility around nuclear safety and protecting public health and safety.

Bringing Unit 2 on-line hit some bumps as brutally cold weather moved into the area. The fan coil units froze, damaging a number of tubes. While making repairs, questions arose about the acceptability of the related gaskets installed on both units. Quick, collaborative decisions were made that Unit 1 posed no immediate safety concerns and would be kept on line. The team decided to replace the parts on Unit 2 to remove any questions and replaced the parts through the holiday weekend.

On Jan. 3, Unit 2 started its measured ascent to 100 percent power, which was achieved on Jan. 13.

Pictured above: An RSG Lower Part is lifted into the containment hatch during Prairie Island’s recent outage.