Nuclear power plants are struggling to stay cool

The Rhne River is one of the most industrialized waterways in the world. As it winds through the south of France towards the Mediterranean Sea, its chilly water is drawn into boilers and sucked through pipes as a coolant. A battalion of nuclear reactor is its biggest customer. About 25% of France's atomic energy has been generated by the river and its tributaries.

That hasn't been the case recently. The Rhne's water has gotten too hot because of the heat wave and low water levels. It's not possible to cool a reactor without expelling water that's so hot it can cause death. A few weeks ago, lectricité de France began shutting down some of the reactor units along the Rhne and the Garonne. In the last two years, there have been similar shutdowns due to the weather. France's nuclear power output has been reduced by nearly 50 percent due to this summer's cuts and other problems.

Of all the low-carbon energy sources that will likely be necessary to fight climate change, nuclear power is usually thought of as the least perturbable. It's the reinforcement that's called in when the weather doesn't cooperate with other zero-carbon energy sources, like wind and solar. But the nuclear industry faces its own climate risks.

Problems with water are more often associated with hydroelectric dams, which have struggled to maintain output in drying places. Nuclear engineering today is more about managing larger-scale aquatic concerns than it is about splitting atoms. Nuclear technicians refer to their craft as a very complicated way of boiling water. The reactor needs more to stay cool. Many facilities are located by the sea and along the Rhne.

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Power plants that run on coal and gas are affected by hotter rivers. Nuclear plants are unique because of their size and the role they play in keeping energy grids online. Climate challenges are not the only ones they face. Increased flooding risks can be found on the coast due to sea level rise and more frequent storms. More frequent algal blooms and exploding jellyfish populations are some of the more unusual challenges that scientists point to.

Nuclear plants are built to last a long time, with lifespans that last a half century or more. Many were constructed in the 70s and 80s before regulators thought to factor in climate-related threats. She says she didn't see anything about climate change. The plans assumed that the current weather patterns would hold up into the future.

Some of the current concerns about climate change are related to safety. The US Nuclear Regulatory Commission began drafting new rules to make existing plants more resistant to climate threats after the disaster in Japan. Dozens of facilities were identified that could be at risk of flooding. The Republican leadership decided that the costs were too high for the nuclear industry to adopt for such low-probability events. Jeff Baran, who was appointed by the Democrats, wrote a dissent about the decision.

The nuclear industry and environmental groups don't agree on whether existing regulations capture the latest science when it comes to sea level rise. "Nuclear plants have a lot of margin on their safety," says Doug True, chief nuclear officer of the Nuclear Energy Institute, a US-based industry group.