Washington — Operators at Exelon's 890-MW Calvert Cliffs-1 units in Lusby, Maryland, shut the unit early Monday morning due to a technical issue, following a downpower to about 10% of capacity from 100% on Sunday when a main transformer cable was found to be disconnected, a US Nuclear Regulatory Commission spokesman said Monday.
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Lacey Dean, a Calvert Cliffs spokeswoman, said in an email late Sunday: "Icy conditions and 60 mph winds [from the weekend blizzard] caused a high voltage line in Calvert Cliffs' switchyard to disconnect." Dean added operators "reduced power on Unit 1 and took the generator offline to allow BGE crews to repair the line safely and effectively."
The 880-MW unit 2 continues to operate at 100% of capacity, she said.
Neil Sheehan, an NRC Region I spokesman, said in an email Monday that operators shut the unit early that day "after elevated sodium levels were identified in the condenser. Plant personnel will be checking for condenser tube leakage."
In addition, operators at Entergy's 849-MW FitzPatrick nuclear power plant in Scriba, New York, manually shut at 10:41 pm EST [0341 GMT] Saturday from 89% of capacity "due to lowering [water] intake level," the company said in an event notification report filed that day with NRC.
FitzPatrick spokeswoman Tammy Holden said in an email Monday: "The lowering intake level indication was a result of frazil ice," which she explained "is a slushy ice condition that occurs in Lake Ontario under ... meteorological conditions involving water temperature, air temperature, and wind speed and direction." She said, "Frazil ice can create a blockage at the [water] intake structure."
Sheehan on Monday said, "There was one complication during shutdown: A power transfer glitch knocked the circulating-water pumps out of service, but other systems were used for the cooldown."
Operators early Friday had reduced the unit's output to 60% of capacity from 100% early in order to conduct unrelated "planned maintenance," Holden said that day in an email.