A wildfire broke out on the Camp Pendleton Marine Base north of San Diego last Wednesday. The smoke could be seen by staff at the San Onofre Nuclear Generating Station and a handful of non-essential plant workers were sent home as a precaution.
Firefighters from Camp Pendleton, in California, work to douse a wildfire.
Members of the plant’s fire department responded to the event and sprayed water on vegetation at the plant’s South Yard to retard the fire’s progress. San Onofre also dispatched some of its personnel to Camp Pendleton to assist base personnel with firefighting efforts on the ground, while helicopters from the Marine base dropped buckets of water on the fire.
The blaze, which was sparked by an accident on Interstate 5, was brought under control in a few hours and never got closer than a half-mile from the owner-controlled area of the plant.
The San Onofre nuclear plant is shut down and preparing to decommission, and remained stable throughout the event. An NRC inspector onsite verified plant conditions and monitored the licensee’s response to the fire from the plant’s control room, relaying information to the NRC’s Region IV office in Arlington, Texas. Because the fire never reached the site or disrupted offsite power to the plant, no emergency declaration was necessary.
But the fire – and the start of the fire season in the West – does highlight NRC regulations related to natural disasters. As a part of their emergency preparedness plans, nuclear power plants are required by the NRC to be able to respond to a variety of natural disasters – hurricanes, tornadoes, tsunamis, earthquakes and fires — which can disrupt offsite power needed for vital plant equipment, interfere with access to the site and cause damage to equipment and threaten the safety of personnel.
NRC requires that all nuclear plants have personnel who have been specially trained and are qualified to respond to fires. Some plants, like Diablo Canyon, maintain on-site fire departments. Others, like San Onofre, have arrangements with off-site fire departments or organizations like Camp Pendleton to supplement their initial response. NRC inspects these response plans to ensure their adequacy and effectiveness.
On Wednesday, we saw those plans put into action. It might not be the last time this year. The need for vigilance will continue in the months ahead for plants located in areas where a prolonged drought is raising concerns about the upcoming summer wildfire season.
U.S. NRC Blog 
Each unit at SONGS had two emergency diesel generators when the plant was operating. After it shut down, they retained one functional diesel per unit. The two remaining diesels are tested monthly and under load periodically. Unit 2 diesel was last tested under load on March 3. The Unit 3 diesel was last tested under load on April 23.
Victor Dricks
Victor, were they tested under the loads they need to carry? In fact, working in many high level military plants, even the specs required test under load, and under actual load they carried, rarely did that happen.
Were they tested under the loads they need to carry?
Diesel generators are tested at all nuclear plants once each month. The San Onofre site maintains one emergency diesel generator in each unit to supply AC power to safety-related systems in the event of a loss of off-site power. The fire at San Onofre last week did not result in a loss of off-site power. The emergency diesels were not tested the day of the fire. But had a loss of off-site power occurred, they would have been available to perform their safety function.
Victor Dricks
Never mentioned in the above is how often the backup generators are tested under load and were they all tested that day and if no why not? This is important because having plan is a great until something causes the plan to fail because something UNPLANNED occurs.
Wildfires and Floods pose the greatest challenge to NPP since there is little to prevent them for occurring since they can happen because of Nature, Man or both!
The NRC Chairman would be wise to pick a NPP at random and have them simulate a surprise Beyond Basis Event along with a 2 week loss of “wide spread” external power due to Nature, similar to what happened at Fukushima, in order to test the NRC emurgency plans.