Download the 2013 Sequoyah calendar from this story online or from TVA's website at http://www.tva.gov/power/nuclear/pdf/2013_SQN_Calendar.pdf
Source: Tennessee Valley Authority
TVA is bringing the nuclear disaster warning sirens for Sequoyah Nuclear Plant into the 21st century.
The federal utility is replacing 108 sirens on wooden poles that would only work when the electric power was on. The rotating state-of-the art replacement sirens -- plus four more new ones -- have battery back-up power and are on stronger steel poles.
"The old sirens have been in place for 30 years now," said Tennessee Valley Authority spokesman Ray Golden. "And if we do have a storm that comes through and takes out power, the new sirens would still be able to operate in the unlikely event that we had some kind of significant emergency at the plant and had to notify the public.
The replacements are part of a $7 million program to update the sirens surrounding all three of TVA's nuclear plants -- Sequoyah, Browns Ferry in North Alabama and Watts Bar near Dayton, Tenn.
Golden and Tom Adkins, manager of TVA's emergency preparedness systems, said four new sirens are being added to the warning system -- which covers a 10-mile radius -- because of spreading development and small shifts in the region's historical wind patterns.
Adkins said TVA made a new modeling study using the newer wind information, so some sirens will be relocated as well as replaced, he said.
"Our plan is to have the system laid out so that if any single siren goes out, that area is still covered by the sirens on either side of it," Adkins said.
In Hamilton County, the sirens are dedicated only to nuclear emergencies. If needed, they are sounded by state emergency officials and coordinated with an emergency alert system message from the state, not TVA, Golden said.
That message would tell the public what happened at Sequoyah and what the public would need to do to stay safe -- either stay indoors with the windows shut and home ventilation systems shut off or evacuate, Golden said.
Golden said the siren replacements were scheduled before the earthquake and tsunami that led to meltdowns at the Fukushima nuclear plant in Japan and before the devastating tornadoes of 2011 in the Southeast.
But both of those natural disasters pointed up the value of the planned change when they left large areas without power, he said.
The record-setting spring tornadoes tore down more than 300 giant power transmission towers leading from Browns Ferry Nuclear Plant, forcing the plant into an unplanned shutdown in which it was cooled with diesel power for a week. In the meantime, the sirens couldn't be operated had they been needed.
Completing the replacements around Sequoyah will take about three months, Golden said, and changing each siren and pole takes about four hours.
As a siren is replaced, it also is tested -- separately from the once-a-month test for the emergency broadcasting system.
In the next two weeks, TVA also will be mailing its 2013 Sequoyah calendar to the 80,000 residents who live within a 10-mile radius of the Soddy-Daisy nuclear plant.
The calendar includes important information about the plant, evacuation routes and other emergency information.
Residents not within that 10-mile zone can still review the calendar and print it out from TVA's website.