Excellent posts with the updated information. No power from the grid and 1 of 4 back-up generators has failed.
Presumably they were running 4 generators because they needed 4 generators, and not just for the hell of it. Now they have 3.
Wonder what broke that seems like it was not major, and whether it will seem more important later on.
No other power reactors shut automatically, or scrammed, said Diane Screnci, another NRC spokeswoman. Fourteen other nuclear plants declared a Notification of Unusual Event, but remained in operation, she said. These are:
--Carolina Power & Light's Shearon Harris-1, North Hill, North Carolina
--Constellation's Calvert Cliffs-1 and -2, Lusby, Maryland
--Dominion Power's Surry-1 and -2, Surry, Virginia
--Entergy's Palisades, Covert, Michigan
--Exelon's Oyster Creek-1, Forked River, New Jersey
--Exelon's Limerick-1, Limerick, Pennsylvania
--Exelon's Peach Bottom-1 and -2, Delta, Pennsylvania
--Exelon's Three Mile Island-1, Middletown, Pennsylvania
--Exelon's Oyster Creek-1, Forked River, New Jersey
--Exelon's Limerick-1, Limerick, Pennyslvania
--PPL's Susquehanna-1 and -2 Salem Township, Pennsylvania
--PSEG's Salem-1 and -2, and Hope Creek-1 and -2, Hancocks Bridge, New Jersey
--Indiana Michigan Power's Donald C. Cook-1 and 2, Bridgman, Michigan
I would assume that they have redundancy built into the system, where when the power goes out all the generators start up even thou they don’t need all four. That way if one does fail, their is no delay until the next one comes online. Also they must account for the fact that at some point they must take one off line at a time to change the oil, filters, etc.
They are not running 4 generators because they need 4 generators. They’re running 4 generators because the procedure says to run 4 generators. They only need one per reactor, and I’d bet they have a way of cross connecting them to only really need 1 for both. Even if off site power is restored, the procedure probably still calls for them to run. Once off site power is restored, they won’t need them at all.
Each unit has two redundant safety trains, i.e. duplicate of everything they need to either shut the plant down safely and/or maintain core temperature. Each safety train has one generator, which by design, is all they need to maintain that unit. Running both trains at the outset of an emergency is likely standard EOP. Loss of one genset does not mean they have inadequate generating capacity. Additionally, they most likey can cross-tie emergency electrical busses across both units, resulting in the availability of 3 gensets, where only two are needed by design for both units. Essentially, they are still up one genset, instead of down one as you imply. 22 years in Nuclear Generation.
Media Silent On Fate Of North Anna Nuclear Plant At Epicenter Of 5.9 Mineral Virginia Earthquake