PPL Corp. on Friday said it was preparing to shut down Unit 1 of its two-reactor Susquehanna Nuclear Plant in northeastern Pennsylvania for additional turbine inspection and to confirm data provided by new instrumentation that could finalize a plan to resolve turbine blade cracking that has afflicted both reactors at the plant.

During a Unit 2 refueling and generation uprate outage in April 2011, PPL found, in a planned inspection, cracks in “certain of its low pressure turbine blades,” the company said. As a precaution, PPL Susquehanna also took Unit 1 out of service in mid-May 2011 to inspect its turbine blades. That inspection revealed cracks in blades similar to those found in Unit 2.

After replacing affected blades and completing other maintenance work, Unit 1 returned to service June 7. Plant operators also shut down Unit 2 to inspect the turbine for cracks on May 30, and that unit returned to service on June 15 after no issues were found during the inspection. According to the company, the after-tax earnings impact, including reduced energy-sales margins and repair expense for both units, was $63 million.

On Friday, PPL Susquehanna said that if cracks are found on Unit 1’s turbine blades, it would determine whether a similar inspection of the Unit 2 turbine was needed. One short-term action PPL Susquehanna has taken was to lower the operating power level of both units at least until inspection of the Unit 1 turbine is complete. This action reduces the potential for cracking to occur or worsen and maintains the plant’s operating safety margin.

The company plans to implement turbine modifications that are designed to resolve the turbine blade cracking issue during future scheduled refueling and maintenance outages starting in the spring of 2013.

Possible repair expenses could be in the range of $15 million to $45 million, the company said on Friday

"Maintaining our margins of safety is the top priority," said Timothy S. Rausch, PPL Susquehanna senior vice president and chief nuclear officer. "Consistent with best practices in the nuclear power industry, we’ve been very systematic and deliberate in our approach to this issue, from conducting periodic inspections to replacing turbine blades when appropriate and installing diagnostic equipment to monitor for conditions that may lead to cracking.

"As a result of these efforts and our ongoing, detailed engineering analysis, we are in the final stages of verifying the causes of the cracking and implementing both short-term and long-term measures to resolve the cracking issues," Rausch said.

Sources: POWERnews, PPL Susquehanna

—Sonal Patel, Senior Writer (@POWERmagazine)