"Greg Copeland" wrote in message
news
On Thu, 29 Sep 2005 13:50:45 +0000, Dylan Smith wrote:

You can't really replace natural gas plants with nuclear plants. Nuclear
plants provide base load power (they can't easily be throttled) for the
continuous supply you always need.

Traditional nuclear plants are "throttled" by controlling the reaction.
As demand goes down, the reaction is slowed, which produces less heat,
creates less steam, and lowers the net energy production. In most nuclear
reactors, this is done via the "control rods". By throttling the nuclear
reaction, they also save fuel and reduce wear-n-tear on the associated
turbines.

http://en.wikipedia.org/wiki/Nuclear_control_rod
http://science.howstuffworks.com/nuclear-power3.htm


Greg



Basically true. The control rods are set for an optimum power level but the
"throttling" is accomplished by the recirculation pumps. Increase the
circulation, cooler water rises into the core. The cooler water is denser
thus providing more hydrogen atoms per square inch for the neutrons to react
with providing more heat.
The delay in powering a reactor up is thermal stresses, namely the
cylindrical fuel pellets. The ends of the pellets expand quicker than the
middle giving it an hour glass shape. If done too quickly the fuel casing
can be damaged reducing the life of the fuel bundle.

Marty