Damage to tubes in steam generators at the St. Lucie Unit 2 nuclear plant was less than expected, Florida Power & Light said after conducting its most recent inspection.
Michael Waldron, an FPL spokesman, said 69 tubes in the two units were removed from service or "plugged" as a precaution, but an inspection last month showed no safety or integrity issues. The two generators together hold 18,000 tubes, which have the dual purpose of creating steam and helping to cool the reactor.
"As we've said all along, steam generators usually see wear early in their life and that wear attenuates with time," Waldron said. "There is no need to replace the steam generators at the St. Lucie plant any time in the near future."
FPL would not say Friday how many tubes now have wear marks or the total number of wear indications. A full report is due to the U.S. Nuclear Regulatory Commission within six months.
While the rate of the unusual tube wear fell below FPL's predictions, critics noted that St. Lucie 2 remains the worst plant in the country when it comes to the number of wear indications.
Arnie Gundersen, a nuclear engineer, said despite FPL's portrayal of the tube wear issue, the move to plug tubes shows a problem persists.
"The bottom line is, it was the worst in the nation before the outage, and it's even worse now," Gundersen said. "These numbers are astronomical. The steam generators just can't get to the end of their useful life."
Last month, federal regulators said the tube wear posed no safety issues at the plant. They would not comment on whether the wear might cause the steam generators to be replaced early.
FPL took St. Lucie 2 offline in March for a regularly scheduled refueling outage. During the outage, the utility conducted an inspection of the steam generator tubes, which have shown wear many times higher than any other active reactor in the country.
FPL replaced St. Lucie 2's two steam generators in 2007 for $140 million, intending them to last until the plant's license expires in 2043. During each refueling outage in 2009, 2011 and 2012, a growing number of steam generator tubes showed signs of wear.
By the last inspection in November 2012, the number grew to 3,745 tubes with 11,518 dents and wear indications from wear against anti-vibration bars. Almost all the other active nuclear plants with replaced steam generators have worn tubes numbering in the hundreds or less.
The only plant with replacement steam generators that have a similar number of tube wear indications was at the San Onofre facility in California. Two reactors there were permanently closed last year after a tube in the steam generator in one unit leaked and it became economically unfeasible to return them to service.
FPL dismisses Gundersen's concerns as coming from an anti-nuclear activist. FPL says the inspection results show less of a wear problem than the utility had predicted. FPL also says San Onofre's tube wear problem included tube-to-tube wear - which led to the leak - that St. Lucie has not had.
"St. Lucie is not unique and tube wear is common and well understood in the nuclear industry," Waldron said. "This inspection confirms that our sophisticated analysis is highly conservative and combined with operating experience, there is significant predictability."
The Southern Alliance for Clean Energy, an environmental group that regularly argues cases before the state Public Service Commission, had asked federal regulators to block St. Lucie 2's return to service until after a full report of the latest inspection was made public.
The Southern Alliance's request was denied, but the Nuclear Regulatory Commission still is reviewing the group's request for a public hearing on the issue.
Ivan Penn can be reached at firstname.lastname@example.org or (727) 892-2332.