North Anna (USA)

Map of North Anna

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2 * 900 MW PWR units; constructed by Westinghouse; grid connection in 1978 and 1980.

Facilities in North Anna

plantreactor typconstruction startoperation startshut down
North Anna-1PWR19711978
North Anna-2PWR19701980

"Two nuclear power reactors at the North Anna plant automatically shut down on 23 August after the grid failed following a 5.8 magnitude earthquake. People reported feeling tremors over a very wide area of the US eastern seaboard after the earthquake struck six kilometres below Mineral, Virginia, at 1.51pm. The units are owned by Dominion Virginia Power, whose spokesman Richard Zuercher told local reporters that four diesel generators started as expected to maintain cooling. However, one of the generators had to be replaced in order to repair a generator coolant leak. Dominion later announced that off-site power had been restored at North Anna, eliminating the need to rely on its back-up diesel generators. The plant was unaffected by several aftershocks that were felt in the region, the company said. Dominion's two-unit Surry nuclear power plant, also in the region, was not affected and continues to operate."


Virginia Power said planning and tighter controls on work scheduling helped North Anna-2 set a station record earlier this month for shortest refueling.
North Anna-2´s outage lasted almost 29 days, ending May 3. The previous station refueling outage record was 30 days, set by North Anna-1 in spring 1996.
Outage exposure was 157 person-rem, higher than the goal of 116 person-rem. There was higher than normal radioactivity in the primary water system, but the utility does not yet know why.
Virginia Power met or exceeded other outage goals. Final figures are not yet in, but the utility expects to come in below the $12,9-million outage budget. The radwaste goal was 1,5 cargo vans and Virginia Power filled only one. The vans, about 2,44m wide by 3,05m high and 9,14m long, are containers that can be shipped by land or sea.


Trip due to a generator problem.Unit will be down at least a week.


Virginia Power´s North Anna was the only nuclear plant among the top 20 least-cost producers of electricity in the U.S. between 1990 and 1994, the Utility Data Institute (UEI) reports. The other 19 were coal-fired plants.
With a five-year average production cost of $12,99 per net megawatt-hour (MWh), North Anna ranked 14th on the list.


The unit is the last of four Virgina Power units to replace cracking, thermally treated alloy 600 Westinghouse SG with more corrosion resistant alloy 690 equipment. Cost for replacing the 3 SG are 126 million US$. SG replacement has been scheduled for 1996 but crack growth was faster than expected.


FW regulating valve unexpectedly oscillated, causing severe secondary-side pipe vibration. - vibrations broke supports, but no system piping was damaged.


Scram following a safety injection due to high steam line flow and low steam line differential pressure, caused by the closure of one MSIV. Failed MSIV rupture disc caused the valve closure. SI injected 3400 liters from the boron injection tank.


SG tube plug failed : first-of-kind-failure in which a portion of a plug severed off . Shut up the tube and damaged at least one adjacent tube> leak rate approx. 265 lit/min leak resulted in a release fo 40 µSv /h at the site boundary; The 265 liters /min. leak rate was about one-tenth of the leak rate that occured when a tube ruptured in the same bundle in July 1987. The plug failure and subsequent tube puncture raises safety concerns because of a new failure mechsanism at a time when a growing number of plugs are in use at aging PWRs (about 370 of 3300 tubes in this SG have been plugged). On average 8,5% of the 3300 tubes in North Annas SGs are plugged. It is planned to replace all 3 in the mid-1990s.


Instrument air system: contamination from water and oil.


Instrument air system: contamination from water and oil


Diesel generator output breaker charging spring motor was loose and failed to recharge. The redundant diesel was out of service . Both diesel generators inoperable. for 38 hours.


Containment isolation valves for pump both coolers an heat exchanger failed leak and was isolated making RHR inoperable - caused by failed solenoid valve.