WASHINGTON (March 16, 2015) — There were only 10 “near miss” incidents at U.S. nuclear reactors last year, but more than 60 percent of the near miss safety violations occurred at three plants owned by Entergy Corp., according to the Union of Concerned Scientists’ (UCS) annual review of Nuclear Regulatory Commission (NRC) performance and nuclear plant safety.
A near miss incident is an event or condition that could increase the chance of reactor core damage by a factor of 10 or more, prompting the NRC to send an inspection team to investigate. The number of near miss incidents has declined since UCS initiated its annual review in 2010. In 2010, there were 19; in 2014 there were 11. All told, from 2010 through 2015 there were 91 near misses.
“Overall, this is a positive trend,” said report author David Lochbaum, director of the Nuclear Safety Project at UCS. “Five years ago, there were nearly twice as many near misses. That said, the nuclear industry is only as good as its worst plant owner. The NRC needs to find out why Entergy plants are experiencing so many potentially serious problems.”
Last year’s near misses occurred at eight nuclear facilities: Calvert Cliffs in Maryland, Duane Arnold in Iowa, Fort Calhoun in Nebraska, Indian Point in New York, North Anna in Virginia, Pilgrim in Massachusetts, River Bend in Louisiana, and Virgil C. Summer in South Carolina. Entergy owns Indian Point, Pilgrim and River Bend, which also experienced a near miss in 2014.
Four of the 10 near misses were due to inadequate equipment repairs.
- At Duane Arnold, the NRC required owner NextEra Energy to replace the original coating on the inside of the reactor’s torus, a key part of the primary containment structure, as a condition for getting a 20-year extension of its operating license. The new coating degraded and broke down, generating debris that clogged emergency pumps.
- During a planned refueling outage at Fort Calhoun, workers rebuilt emergency backup system valves that control the rate of “makeup” water that cools the reactor core if the primary system fails. The replacement parts were less vulnerable to radiation, but they were susceptible to failing at high temperatures. When workers restarted the reactor, rising temperatures deformed some valve parts, impairing their ability to open and close
- When Winter Storm Juno knocked out high-voltage transmission lines to Pilgrim in January 2015, control room operators could not open a safety relief valve to lower pressure inside the reactor vessel. Pilgrim experienced a similar problem when the reactor shut down in February 2013, but workers failed to identify the cause or fix it. Entergy plans to close the 44-year-old plant, one of the least-safe in the nation, by June 2019.
- After an unplanned shutdown occurred at Entergy’s River Bend plant, workers narrowed down the cause of the power failure to either one of two parts. They replaced the wrong part, however, and three weeks later, the faulty part failed again, shutting down the plant.
“Many U.S. reactors are entering their fourth decade, and as they age, safety equipment will wear out and need to be repaired or replaced,” said Lochbaum, who worked in the nuclear industry for 17 years before joining UCS. “Given the very real possibility that one of these screw-ups could lead to a serious accident, plant owners have to make sure their workers make repairs correctly. If they don’t do it right the first time, aging reactors will experience even more problems.”