Alaric B Snell wrote:

Howard R Garner wrote:

All nuclear plants have a secondary source of power and also have
emergency generation capabilities. Never a concern about radioactive
releases. Just a safty shutdown lake a steam plant would do.

Howard
20 years of Navy nuclear experience


Below a certain point, apparently, a nuclear plant is producing less
power than its own cooling system is consuming - so they need external
power to run the cooling system during startup and shutdown.

I remember a case in the former USSR where the Navy hadn't paid their
power bills for a year or so because they didn't have any money, so
the power company cut their line. The navy sent armed men to storm the
power station and turn the power back on - because they had a nuclear
sub under repair in dock with the reactor idling, and without power it
was in danger of becoming a glowing lump at the bottom of the harbour,
plus a good amount of dust in the air above, etc.

I've heard various contradictory accounts of What Went Wrong at
Chernobyl, but one of them related to the reactor being used for
experiments in powering down with minimal power input (eg, if you run
it hard then shut down quickly there might be enough 'inertia' in the
cooling system to last it or something) when something went wrong with
the incoming power line from the other reactors in the complex and
they were left with an overheated reactor and no power.

Also, power grids are complex beasts. It's not like a gas manifold -
you can't just plug in more generators. Not only are there AC phase
synch issues, but all sorts of other wierd stuff to do with inductance
and power factors and phase shifts when you have a hundred mile long
cable and whatnot. Apparently early attempts at power grids failed
until they managed to build analog computers that could solve all the
equations in real time in order to keep the network 'balanced' -
otherwise the voltage would rise in some areas and drop in others due
to interference patterns between the outputs from each generator or
something.

ABS

I remember an EE lecture in college about how they tried to assemble a
nation wide grid,
but that it was impossible to keep the whole thing in phase. IIRC, a low
frequency ripple
would start and slowly build amplitude until circuit breakers along the
line would pop.

Fred