Re: Time period for power plants to cool down after shut-down


"mytheo" <mtheofilidi@xxxxxxxxx> wrote in message news:167e8afc-2bd1-4fab-b11c-b49f06851206@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Hello,

can anybody help me with a reference to find out the time needed for
various types of power plants (coal, lignite, CCGT, gas turbine, etc)
to cool down after they are shut down? The shut down costs would also
be of interest. Thanks a lot for helping!

Experience with nuclear plants is that they can be forced cooled at rates of about 50 to 80 degrees per hour. This cooldown is limited by the thermal stresses that a higher cooldown rate would impose on some of the key components. With a normal operating temperature of about 550 degrees, this means 'cold iron' can be reached in 10 hours or less.

Some of the equipment outside the primary, such as the turbine casing can only be cooled by slow ambient heat loss. So for them it may take a bit longer. But turbine maintenance can generally begin after 24 to 36 hours.

As to the shutdown costs, well there is no extra cost of just shutting down. No additional pumps of any consequence are used. So the 'costs' are basically the lost opportunity costs of lost generation time minus fuel costs.

For a nuc, fuel costs are a small portion of the total daily costs, so there is little savings there and the total 'shutdown costs' are just the lost revenue. Of course any maintenance activity will be added on to that.

For some other types of plants, such as gas-turbine, the fuel costs are a significant part of the total daily costs and these are of course avoided when the plant is shutdown. So the 'shutdown costs' would be the lost revenue minus this significant fuel-cost-savings (again, plus any maintenance activity).

Hope this helps,

daestrom

.

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