Highly pressurized, superheated water that corroded a nickel-alloy tube from the inside was probably what caused a radioactive leak at the Indian Point 2 power plant last month, according to the Nuclear Regulatory Commission (NRC).
NRC spokesman Neil Sheehan emphasized that an official finding is weeks away and "there are other pieces of that puzzle that we still have to look at."
However, based on a videotape from a remote-controlled camera sent into the tube, "it's probable that this was stress corrosion cracking," Sheehan said Thursday.
An minute amount of radioactive steam escaped into the atmosphere Feb. 15, when radioactive water from one of the reactor's 13,000 tubes contaminated the clean water that is turned to steam to drive turbines.
No one was injured at the plant 35 miles north of New York City that is owned and operated by Con Edison. It was the worst accident in its 26-year history.
If it is concluded that corrosion was the cause, it could raise questions about the industry's inspection practices.
An inspection at the plant in 1997 showed no sign of a crack in the tube that leaked, according to Con Ed.
Con Ed had gotten NRC permission to postpone a scheduled 1999 inspection because the plant was out of service for parts of the intervening two years.
NRC investigators told Con Ed that if the crack could appear, deepen and break open between inspections, the inspection schedule might have to be tightened.
Con Ed Vice President Stephen Quinn said a decision on more frequent inspections should be made on "sound, technical knowledge" and should await the completion of the investigation.
