Unit 1 at Florida’s St. Lucie nuclear plant is back online after condenser pressure levels prompted safety systems to shut it down last week.According to a Nuclear Regulatory Commission event report, the reactor tripped at 5:28 a.m., Wednesday, following elevated condenser backpressure caused by a circulating water pump malfunction. A second pump in the system was undergoing maintenance.All safety systems operated as designed, and the pump problems were not within the water loop that cools the reactor. Local media quoted Florida Power & Light as saying the reactor restarted Thursday night following repairs. It was operating at 41 percent power as of Friday, according to the NRC.FP&L operates two, 839-megawatt Combustion Engineering pressurized water reactors at the plant near Ft. Pierce, Fla.