From earthquakes to jellyfish: See 8 emergency alerts at Diablo Canyon nuclear power plant
From chemical leaks to a wandering hiker, Diablo Canyon nuclear power plant has reported a variety of incidents that rise to the level of an emergency alert over the past decade and a half.
The U.S. Nuclear Regulatory Commission has four emergency alert levels for nuclear power plants: an unusual event, an alert, a site area emergency and a general emergency.
Diablo Canyon has experienced eight events that fit the four emergency levels since 2009, the year the commission changed its definitions for each category, according to PG&E’s vice president of nuclear generation business and technical service Maureen Zawalick.
The majority were at the lowest level.
PG&E has only declared two alerts — the second emergency level — at the power plant over those years.
The first was on June 23, 2010, when when a mechanical malfunction released Cardox, a fire suppressant, into the Unit 1 main lube oil reservoir room.
The second was on July 28, 2017, when a nitrogen leak caused low oxygen levels inside the Unit 2 containment building — requiring the use of breathing apparatus in the area, according to commission reports.
Neither event harmed power plant personnel or endangered public safety, according to commission reports.
The remainder of the reported incidents were classified as unusual events and were the result of earthquakes, weather events, chemical leaks and a trespasser hiking on the property, according to commission reports.
Even before 2009, the power plant did not have a severe enough event to warrant a site area emergency or general emergency, according to PG&E.
Meanwhile, the plant occasionally has other incidents that don’t rise to the level of an emergency alert but do spark a response.
For example, power plant security spotted a trespasser on a road on PG&E property on July 31, according to San Luis Obispo County Sheriff’s Office spokesperson Tony Cipolla.
Stephen Wesley Walls, 30, said he accidentally entered the property through Montaña de Oro State Park.
Deputies discovered that Walls had three out-of-county warrants for his arrest on burglary charges and failure to appear, then arrested him, Cipolla said.
Here’s a look at reported incidents at the power plant.
Incidents reported at Diablo Canyon nuclear power plant
PG&E has reported six unusual events at Diablo Canyon nuclear power plant since 2009.
An unusual event is an incident that has the potential to threaten the safety of the power plant’s operations, according to the U.S. Nuclear Regulatory Commission.
On June 2, 2009, PG&E reported a false fire alarm at the power plant as an unusual event.
A year later, on June 9, 2010, a sodium hydroxide spill in the Unit 1 Turbine Building buttress area caused PG&E to declare an unusual event.
On Dec. 25, 2010, high wind speeds of over 80 mph prompted the plant to declare an unusual event.
At 4:25 p.m., the plant recorded peak wind speeds of 80 mph and sustained speeds at almost 54 mph, commission records said. By 11:33 p.m., the storm had passed without damaging the plant, and winds reduced to 2 mph.
The March 11, 2011 earthquake in Japan that killed nearly 20,000 people and caused a meltdown of three reactors at the Fukushima Daiichi nuclear plant spurred a tsunami warning on the California coast — causing PG&E to temporarily evacuate the power plant intake structure on and declare another unusual event.
On Oct. 12, 2012, PG&E declared an unusual event when an earthquake near King City shook the power plant. Inspections of the plant found no damage, a commission report said.
And on Jan. 14, 2016, a hiker strayed too far on the Point Buchon Trail in Montaña de Oro State Park and walked onto PG&E property in the hills surrounding the power plant. The hiker had failed to register with PG&E ahead of time as required, leading the plant to note the incident.
Additionally, numerous historically reported unusual events no longer fit the new definition, Zalawick said.
“As the industry goes through certain operating experience and enhancing some of our methodologies and tools, especially in the risk assessments, risk management processes, the emergency classification levels have revisions, and the methodologies improve,” she said.
That includes the 2003 San Simeon Earthquake, which was detected at the power plant. The plant continued to operate at full capacity during the earthquake, though, and no equipment was damaged.
A previously reported jellyfish incident also no longer fits the emergency classification criteria.
On Oct. 21, 2008, a “rapid influx of jellyfish” crammed into the pipes of the water intake structure, temporarily shutting down the power plant, the commission report said.
This story was originally published August 14, 2024 at 11:18 AM.
