On 29/10/13 01:02, Dave Liquorice wrote:
On Mon, 28 Oct 2013 16:50:16 +0000, The Natural Philosopher wrote:

so it is possible that something has bitched a power line - and quite a
big power line if the station was cut off.

Or breakers in a grid switching center got upset by the surges caused
by lines downstream being brought down and tripped Dungeness off.

Once tripped off and Dungeness going into emergency shutdown it takes
about a week to sort things out and bring it back online.

I wonder if the operators at Dungeness could see the varying load and
were aware of the possibilty of a trip or if the first thing they
knew was AWOOGA! AWOOGA! SHUTDOWN! SHUTDOWN! causing them to spill
their morning cup of tea?

AIUI there are automatic safety trips that would detect and
undecurrent/overvoltage/overspeed and synch loss on the generators and
essentially shut off the turbine steam before it revved beyiond safe
limits. Thats a governor of sorts.

Then one would expect te main breakers would blow isolating the station
from the grid, at which point its on battery power and the diesels would
start up,

the rectorr would have been scrammed as part of the trip proecss,
stopping te chain reaction instantly, and the only nucelar issues left
aredeacy heat in te fuel rods, cibered by curculkatin te gas through te
core. A cannot remember where AGRS use convection or pumped gas but they
are very safe designs.

http://en.wikipedia.org/wiki/Advance...cooled_reactor

ah yes, forced water and gas coooling, so they need the pumps.

At this point there will be steam to vent to prevent overpressures in
the boilers, and probably some way to divert excess heat straight to the
condensers without the turbines being involved. Thse will spin down and
stop.

Asyousay it takes time to get everything up and working again. restioing
the grid to get off diesel power would be priority and take a day or two
at most.

Then they mighttae te opportunity to do spome minteneace work or cold
refuelling (AGRS are usually refuelled at part power or cold)

then spinning up and synching..

Anyway weve got 4 reactors down in three power plants - two at dungeness
, and one each at two sites for regulatory inspections. Both will be
back up by X mas..

EDF gives no firm date yet to restart dungeness.

Presumably they will want to assess if any other damage ocurred.

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