Browns Ferry Nuclear Plant began loading used fuel this week into huge dry casks for long-term storage.
The plant will be the first in the nuclear industry to use the new HI-STORM flood and wind cask system designed to withstand tornadoes, high winds, lightning and other natural disasters, said Kristine Shattuck-Cooper, public relations officer for the Tennessee Valley Authority, which owns the Limestone County power plant.
The plant will be the first in the nuclear industry to use the new HI-STORM flood and wind cask system, she said. Other plants use a similar design but not the flood and wind cast system, she said.
“The cask system is designed to withstand an EF5 tornado,” Shattuck-Cooper said.
That is a must in Limestone County.
An EF5 tornado, the strongest possible, struck near the plant on April 27, 2011. When it did, all three reactors at the plant scrammed, or shut down, when external power was lost. Despite the loss of external power, control rod insertion and cooling procedures at the plant operated as designed with no physical damage or release of radiation, officials said. However, the storm caused widespread damage to transmission lines and left Browns Ferry unable to produce power for the grid, triggering significant blackouts throughout the southeastern United States.
Each 180-ton cask holds 89 used fuel bundles, she said. The casks will be placed outside the plant but inside the guarded property, she said.
“The casks have an 18-inch thick concrete outer portion and an inner cask of metal,” Shattuck-Cooper said.
For years, Browns Ferry and all other nuclear power plants in the United States have stored used nuclear fuel in spent fuel pools, according to the Nuclear Regulatory Commission. The 40-foot-deep pools are made of several feet of reinforced concrete and lined with steel.
“They stay there for an amount of time until they are cooled,” Shattuck-Cooper said. (Typically about five years, according to the NRC.) When the pools reach capacity, the older spent fuel is moved to dry cask storage.
Plans to build a national repository for used fuel storage at Yucca Mountain have been held up for years, she said. Because of that, all of the nuclear facilities had to figure out how to store used fuel rods long term and how to do so at the facility where they were produced, as required by the NRC.
“At this point, because we had to store fuel rods and there is limited space in the pools, we’ve had to look at dry storage,” Shattuck-Cooper said.
After the terrorist attacks of Sept. 11, 2001, the NRC issued orders to plant operators requiring several measures aimed at mitigating the effects of a large fire, explosion, or accident that damages a spent fuel pool. These were meant to deal with the aftermath of a terrorist attack or a plane crash. However, they would also be effective in responding to natural phenomena such as tornadoes, earthquakes or tsunami.