27 October 2014
Construction has been completed of a "beyond design" dome at Dominion's North Anna nuclear power plant in Virginia. The dome - which will house emergency equipment and supplies - is the first of its kind in the USA.
The new domed storage facility at North Anna (Image: ABC Domes)
The steel-reinforced concrete dome - with a diameter of 36.5 metres and a height of 11.5 metres - covers an area of 965 square metres. It features two hardened equipment doors. The building was designed by Engineering System Solutions (ES2) and constructed by American Business Continuity Domes (ABC Domes) and Dome Technology.
In response to the March 2011 accident at Japan's Fukushima Daiichi plant, the US Nuclear Regulatory Commission issued an order with specific requirements for mitigation strategies for beyond-design basis external events. The "diverse and flexible coping capability" (or FLEX) strategy was an industry initiative announced in February 2012 to implement the NRC's Fukushima task force recommendations. The initiative includes the purchase of additional on-site portable equipment at every nuclear facility in the USA. The new equipment is to be stored at diverse locations and protected to ensure that it can be used if other systems that comprise a facility's multi-layered safety strategy are compromised.
Dominion's director of nuclear engineering Eric Hendrixson explained, "The concept of the FLEX program is assume everything is broken and have flexible equipment that you can tie into the various points in the plant."
He added, "There is enough equipment for each of the reactors and then we have installed a third set in case some of this equipment didn't work, so that if you need something you can make a repair and it's all inside this dome. Anything from water to food, to anything and everything you can imagine - flashlight batteries - it's all in here." Hendrixson noted, "All the staff that is here 24/7 has the ability to run all of this equipment."
"The dome shape means it is a blunt object, so that if there's heavy winds or storms or tornado, it has the tendency to flow off the round sides of the dome, as opposed to a flat surface," Hendrixson said. The dome is claimed to be capable of withstanding winds of up to 360 mph (580 km/h), "event driven missiles" and earthquakes.
A Dominion spokesman told World Nuclear News, "North Anna unit 2 is the first facility in the US to complete all required FLEX modifications, storage building, procedures and training."
Similar facilities are nearing completion at Dominion's other operating nuclear power plants. The dome at the Millstone plant in Connecticut is due to be completed by the end of this month, while that at the Surry plant in Virginia should be finished in December.
ABC Domes said it was working on seven more such domes for two other US nuclear utilities.
Researched and written by World Nuclear News