"Our greatest responsibility is to be good ancestors."

-Jonas Salk

Monday, August 20, 2007

Nasty feedback loop

Nuclear power plants require water cooling, and avoid climate change. Climate change reduces the volume and increases the ambient temperature of cooling water flows. Nuclear capacity may be taken offline, implying an expensive restart at best.

This is probably not a first order problem with nuclear power specifically, but it is illustrative of how when you start pushing systems out of their accustomed range you start seeing informal assumptions violated by the real world.

Large cooling systems need to account for uncertain water supplies and increasing water temperatures.


Heiko said...

It's not much of a feedback loop, thermal power plants can be built to operate with outside temperatures of 500C, though the efficiency will go down some, unless you can come up with materials that'll withstand a few thousand C.

Usually, thermal power plants using river water for cooling are shut down to protect aquatic river life. I actually find it quite hard to believe it would be for plant operational reasons.

Heiko said...

Just had the thought you might misunderstand the 500C figure. Of course, no plants are built today capable of withstanding anything close to that, most steam cycles don't run much higher than that, because of material limitations (both temperature and steam pessure).

Michael Tobis said...

I don't really see your point here.

If the reason the plant was shut down has more to do with the capacity of the river than the capacity of the plant, it is nevertheless the case that the plant was shut down because the cooling capacity of the river has been exceeded.

John Fleck said...

This is the tip of a very big iceberg:


Heiko said...

Sorry about being so clumsy making my points.

In France the reason nuclear plants were shut down was that high river water temperatures would have been bad for fish and other aquatic life, and given an emergency environmental permit they could (and did in some cases to avoid blackouts) be run regardless.

But, clearly you are right, if there's no water in the river, or far too little water, river cooling just plain won't work even if we were willing to literally boil the fish in the river. I think I didn't properly think through what you said.

It's possible to make do without cooling water, but that's a relatively big investment (I think something like 10-20% of the capital cost of a nuclear / coal fired power plant) and it's not worth the expense for a few hots days per year. The way to get around cooling water is to use forced air heat exchangers.