Unanticipated drought consequences
I've had a couple of conversations with folks telling me that's not the only place capacity suffers during a drought. Nuclear plants use prodigious quantities of water for cooling purposes, and in some cases their supplies are getting near the level where the plants will be required to shut down.
Here's the first wire services story i've seen discussing this:
At Progress Energy Inc., which operates four reactors in the drought zone, officials warned in November that the drought could force it to shut down its Harris reactor near Raleigh, according to documents obtained by the AP. The water in Harris Lake stands at 218.5 feet — just 3 1/2 feet above the limit set in the plant's license.
Lake Norman near Charlotte is down to 93.7 feet — less than a foot above the minimum set in the license for Duke Energy Corp.'s McGuire nuclear plant. The lake was at 98.2 feet just a year ago.
"We don't know what's going to happen in the future. We know we haven't gotten enough rain, so we can't rule anything out," said Duke spokeswoman Rita Sipe. "But based on what we know now, we don't believe we'll have to shut down the plants."
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How much water are we talking about? A lot.
At some plants — those with tall, Three Mile Island-style cooling towers — a lot of the water travels up the tower and is lost to evaporation. At other plants, almost all of the water is returned to the lake or river, though significantly hotter because of the heat absorbed from the steam.
Progress spokeswoman Julie Hahn said the Harris reactor, for example, sucks up 33 million gallons a day, with 17 million gallons lost to evaporation via its big cooling towers. Duke's McGuire plant draws in more than 1 billion gallons a day, but most of it is pumped back to its source.
Nuclear plants are subject to restrictions on the temperature of the discharged coolant, because hot water can kill fish or plants or otherwise disrupt the environment. Those restrictions, coupled with the drought, led to the one-day shutdown Aug. 16 of a TVA reactor at Browns Ferry in Alabama.
To put that in perspective, Durham's daily water usage has averaged just over 20 million gallons per day during January, or only about 15% more than Shearon Harris loses every day to evaporation.
So far, according to all the power company spokespeople, shutting down the plants seems unlikely. Time will tell. If the plants do shut down, the main concern so far seems to be the cost of replacement power, not it's availability. Again, time will tell. I haven't heard that there's a ridiculous amount of surplus energy being generated along the eastern seaboard to replace the loss of up to 25% or 30% of capacity during the high demand summer months.
Officials were way too sanguine last year as drought conditions developed from a nuisance to a crisis in a short period of time. Rolling blackouts and brownouts will quickly teach us how minor an inconvenience "letting the yellow mellow" really is.