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US FLEX nuclear emergency response programme now well advanced

28 October 2014

As part of the US nuclear industry’s ongoing response to the events at Fukushima in 2011, additional portable equipment is being added to all US nuclear sites based on the diverse and flexible coping strategy (FLEX) announced in February 2012 by the US Nuclear Regulatory Commission (NRC) to provide mitigation strategies for beyond-design basis external events.

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The new equipment will be stored at many separate locations and protected to ensure that it can be used if other systems that comprise a facility's multi-layered safety strategy are compromised. Its main purpose will be to cool nuclear reactors and used fuel storage pools, and to maintain the integrity of reactor containment structures in the event of a catastrophic failure.

The implementation of this strategy required new facilities and equipment at all US nuclear power plants, as well as the creation of two new regional response centres (RRCs) to provide a second source of portable equipment for nuclear sites. 

Both RRCs, situated outside Phoenix, Arizona, and Memphis, Tennessee, have been operational since June. Equipment stored at the centres includes portable backup generators, radiation protection equipment, portable high and low pressure pumps, diesel transfer pumps, fuel tanks, light towers, water treatment pumps, electrical distribution cabinets, cables, and hoses.

They also contain tanks that hold boron, which is pumped into a reactor to absorb neutrons and safely shut down a reactor that is at a critical stage.

Each centre houses five full sets of equipment, with four ready to be moved to any US nuclear power plant at all times, and the equipment will undergo regular testing for operability. Given that there are several different US reactor types in operation, the equipment is designed to work with all of them, and it can be delivered to any nuclear site within 24 hours via ground and air.

The startup cost for each facility is about $40 million, with annual operating costs of about $4 million. The costs will be shared by companies operating the 100 reactors that generate one-fifth of the US’s electricity.

In addition to the RRCs, nuclear plant operators have been tasked by the NRC with providing on-site backup to provide an uninterrupted supply of electricity and cooling water to protect critical plant safety systems at all times. Utilities across the country have been building robust facilities to protect and house emergency equipment such as generators, battery packs, pumps and vehicles that can move this equipment to wherever it is needed at short notice.

As an example, Duke Energy’s McGuire Nuclear Station in North Carolina currently has three FLEX buildings under construction, each designed to withstand hurricanes, tornadoes, earthquakes and winds up to 240 mph. The foundation of the buildings is nearly two feet in the ground to ensure their stability. All Duke Energy-owned and operated nuclear stations will have new FLEX buildings in the future.

Dominion Generation has commissioned reinforced concrete dome structures for FLEX storage at its nuclear sites. The first two were completed in October at the North Anna and Surry Nuclear Stations in Virginia, and another at Millstone NPP in Connecticut is scheduled to open in December.

Dominion's director of nuclear engineering Eric Hendrixson said: "The concept of the FLEX program is to assume everything is broken and have flexible equipment that you can tie into various points in the plant.

"There is enough equipment for each of the reactors and then we have installed a third set in case some of the equipment doesn't work, so that if you need something you can make a repair and it's all inside the dome. Anything from water to food or flashlight batteries - it's all in here."

Canada is also building emergency response centres, with Ontario Power Generation recently announcing the commissioning of its first regional support centre.

French energy utility EDF, one of the largest nuclear plant operators in the world, has also implemented a similar programme. It has four nuclear rapid action force bases (French acronym FARN) in place across the country, all with extensive specialised equipment.

Its UK subsidiary, EDF Energy, is building four centres to cover its UK nuclear stations, with the first at Sizewell becoming fully operational earlier this year.


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