Nuclear Plants Face More Heat Risk Than They’re Prepared to Handle

(Bloomberg) -- Climate change—particularly intense heat—is advancing so rapidly that it poses physical as well as credit risks to America’s aging nuclear fleet, a new report from Moody’s Investors Service finds.

“Our plants are fairly hardened to severe weather,” said David Kamran, a projects and infrastructure analyst at Moody’s and the lead author of the report. “But climate change is moving quickly.” 

America’s nuclear power plants produce roughly 20% of the country’s electricity and represent more than half of all of its carbon-free power generation. After the earthquake and tsunami that caused a meltdown at Japan’s Fukushima-Daiichi nuclear power plant in 2011, the U.S. Nuclear Regulatory Commission asked domestic plants to conduct their own assessments of risks from climate change and other natural hazards. A 2019 Bloomberg review of correspondence between the commission and owners of 60 plants concerning those assessments found that 54 of their facilities weren’t designed to handle the flood risk they now face.

The new report is the result of an analysis conducted by Four Twenty Seven Inc., a climate risk data company Moody’s acquired last year. The group evaluated the potential effects of heat stress, water stress, hurricanes, flooding, and rising sea levels on 57 U.S. nuclear power plants over the next 20 years. It found that while a handful of plants—including Cooper Nuclear Station in Nemaha, Neb. and  Prairie Island in Goodhue, Minn.—face severe risk from floods, far more either will face or already face “red flag” conditions from heat.

Nuclear plants are cooled by water, and in times of intense heat and drought, water resources can become either too warm or too scarce, forcing shutdowns. This has already happened, and not just in the South: in 2012, Dominion Energy Inc.’s Millstone nuclear plant in Waterford, Conn. The report predicts that nuclear plants in the Rocky Mountain states, the Colorado River region, and California face the highest levels of water stress risk going forward.

Kamran said in an interview that this report wasn’t about estimating the risk of a meltdown. Currently, he said, most U.S. plants are sufficiently resilient not to face a catastrophe, even in the event of exceptionally severe weather.

Instead the report was meant to highlight the extent of the environmental pressures plants will have to adapt to withstand if they want to operate consistently in the coming decades. Resisting those stresses is potentially expensive— even more expensive than the plants have currently estimated, he said: “In certain cases they will need to make investments to further reinforce their plants and they need to have money in their cap-ex funds to do that.”

©2020 Bloomberg L.P.