Nuclear plant finds flaw during refueling outage

Nov 11 - McClatchy-Tribune Regional News - Dave DeWitte The Gazette, Cedar Rapids, Iowa

NextEra Energy has begun steps to repair a 6-inch weld joint flaw found during a refueling outage at the Duane Arnold Energy Center this month.

The discovery was described in a 21-page letter to the Nuclear Regulatory Commission on Nov. 6. It describes an 'indication identified in the N2A Recirculation Inlet Safe End to Safe End Extension Dissimilar Metal Weld.' A preliminary assessment attributes the problem to 'stress corrosion cracking,' according to the report. Following the discovery, three similar welds were examined using ultrasound technology, but no indications were found requiring repairs.

Six inches in length, the weld flaw is believed to penetrate more than 70 percent of the metal on the recirculation nozzle.

It was a weld that connected two different kinds of metal.

Plant spokeswoman Renee Nelson said the flaw was discovered during routine testing.

'It's not uncommon when you have welds in dissimilar metals that are exposed to stressors such as water temperature and things like that,' Nelson said.

NextEra has contingency plans for this type of situation and expects to complete the repair in parallel with other planned refueling outage maintenance activities, she said.

NextEra Energy Director of Nuclear Communications Michael Waldron said the flaw will be repaired by applying an additional layer of weld material to the area of concern. After the repairs, the weld will be pressure tested before the nozzle is placed back in service.

The company does not comment on the amount of time it expects a plant refueling outage to require, Waldron said.

Duane Arnold Energy Center near Palo is Iowa's only nuclear power plant. NextEra, the majority owner.

NextEra's letter details a repair plan that it says is based on restoring the integrity of the weld joint while limiting radiation exposure to repair personnel to the maximum extent practical.

The discovery comes just as NextEra is in the final stages of an application for a 20-year extension of the plant's operating license, which expires in 2014.

NextEra officials were not immediately available for comment on the finding.

-- Comments: (319) 398-8317; david.dewitte@sourcemedia.net