A climate risk to nuclear power

Climate Central has a look at the problem posed to nuclear power plants by rising temperatures - A climate risk to nuclear power.

Compared to coal and natural gas, nuclear power plants offer a significant advantage when it comes to greenhouse gas emissions – they don't emit any. However, in an ironic twist, it seems that climate change is increasingly causing problems for operators of nuclear plants.

Like coal-fired power plants, nuclear facilities use large amounts of water for cooling purposes. After water has cycled through the plant, it is discharged back into a nearby waterway, usually a lake or a river, at a higher temperature. US state regulations prohibit nuclear plants from operating once water temperatures go above a certain threshold, in part because it could compromise the safe operation of the facility, and also because discharging very warm water can kill fish and other marine life.

According to the New York Times' Matthew L. Wald, the Braidwood Generating Station, located about 60 miles southwest of Chicago, was recently granted a waiver to continue operating despite the fact that the unusually hot and dry summer had heated the water it was taking in to a toasty 102 degrees Fahrenheit – 2 degrees above the legal operating limit for the plant.

Like much of the country, Illinois has had an extremely hot summer. In fact, Illinois had its warmest January-to-June period on record.

According to Wald's story, operators of the Braidwood plant have been hit by the combination of extremely hot days and very warm nights. Nationally, thousands of daily high temperature records and warm overnight low temperature records have been set this summer.

The Times quoted Craig Nesbit, a spokesman for Exelon, Braidwood's operator:

"Asked whether he viewed Braidwood’s difficulties as a byproduct of global warming, Mr Nesbit said: “I’m not a climatologist. But clearly the calculations when the plant was first operated in 1986 are not what is sufficient today, not all the time.”

Climate Central's Alyson Kenward reported on the threat that climate change poses to electricity generation in 2011, when she detailed problems that a 2010 heat wave caused for operators of the Browns Ferry nuclear plant in Alabama.

"With river water so warm, the nuclear plant couldn’t draw in as much water as usual to cool the facility's three reactors, or else the water it pumped back into the river could be hot enough to harm the local ecosystem, says Golden. But for every day that the Browns Ferry plant ran at 50 per cent of its maximum output, the TVA had to spend $1 million more than usual to purchase power from somewhere else, he says.

What happened in northern Alabama last summer, at the largest of TVA's nuclear power plants, did not present a human safety concern. Operators knew there was never a risk of an explosion or nuclear meltdown, nor was there a threat of leaking radioactive material. But the prolonged spell of hot weather put the TVA at risk of violating environmental permits, with hefty fines as one consequence and potential harm to the Tennessee River ecosystem as another.

It’s not the first time high temperatures have affected the performance of the Browns Ferry plant, and extreme heat is a growing concern for power plant operators across the Southeast."

With global warming already increasing the odds of extreme heat events, the challenges faced at Braidwood and Browns Ferry are likely to become more common in the coming years. It's an open question as to whether the nuclear industry is prepared for this. As the Union of Concerned Scientists' David Lochbaum told the Times, “Nuclear plants like Goldilocks weather – not too hot, not too cold, but just right." Such weather is getting harder and harder to come by.