From the Tennessee Valley Authority Press Release -
Wednesday will go down in history as one of the worst outbreaks of tornadoes in a single day in American History.
Units 3 and 2 at TVA's Browns Ferry Nuclear Plant achieved "cold shutdown" Thursday at 2:43 a.m. CDT and 5:45 a.m. CDT, respectively. "Cold shutdown" is achieved when the reactor coolant system temperature is cooled to 212 degrees Fahrenheit or less. Unit 1 is being cooled.
The three Browns Ferry units automatically shut down on Wednesday, April 27, at 4:36 p.m. CDT when severe weather damaged TVA's transmission system near the plant. Systems operated as designed to safely shutdown the units.
Without sufficient offsite power available to the plant, seven of eight emergency diesel generators automatically started to provide power for the equipment needed to safely cool down the reactors. The eighth diesel generator was out of service for planned maintenance; it is expected to be returned to service today.