Feb 25 - McClatchy-Tribune Business News Formerly Knight Ridder/Tribune Business News - Dave DeWitte The Gazette, Cedar Rapids, Iowa

Discovery of hairline cracks in welds on two recirculation nozzles on the nuclear reactor at Duane Arnold Energy Center will complicate a refueling outage at Iowa's only nuclear power plant.

The discovery of a "linear indication" about 7 inches long and 30 percent through one reactor nozzle wall was reported to the Nuclear Regulatory Commission on Monday. A second flaw about 10 inches long and 82 percent through another reactor nozzle wall was reported to the agency Thursday.

The cracks were on nozzles where a pipe connects to the reactor, said Jan Strasma, public affairs officer for the commission's regional office in Chicago.

Located on the outside of the reactor, the nozzles are part of the primary recirculating water system that takes radioactive water from one part of the reactor and pumps it to another part of the reactor to improve its efficiency.

Strasma said the flaws were found as the result of ultrasonic testing that is part of the inspection process carried out during the plant refueling outage. The nozzles were not leaking.

Similar testing methods led to the discovery of cracks in the same kind of nozzles in 1999 at the plant, Strasma said. Such cracks have been detected at other plants of similar design.

The commission will monitor repairs and will not permit the plant to resume operations until they are completed satisfactorily.

Strasma said the repairs will involve a "weld overlay," a welding technique to fill in the cracks with metal.

The plant is operated by FPL Energy, which acquired a majority stake last year from Alliant Energy.

Duane Arnold spokeswoman Renee Nelson called the issue "an engineering problem, not a safety problem."

"At no time did it affect plant operations," she said.

Nelson said FPL went into the refueling outage with a contingency plan in case such flaws were found. She declined to say whether the execution of that plan would prolong the plant shutdown.

Although the nuclear commission's Strasma referred to the flaws as "cracks," Nelson said FPL regards them as "weld flaws." She said FPL used ultrasonic inspection to examine the nozzles during the previous refueling outage and found no indication of flaws. She said the company used more advanced ultrasonic inspection this time and credits it with the ability to discover the flaws.

The plant was shut down early this month for thousands of maintenance activities and the replacement of one-third of its fueling rods.

Duane Arnold Energy Center has a rated output capacity of 598 megawatts, enough to power 600,000 homes, and employs 500.