California officials deploy radiation detectors as Sandy Fire nears nuclear site

California officials scrambled on May 18 when the Sandy Fire, a 2,183‑acre blaze that began south of Simi Valley, pushed toward the site of the 1979 nuclear reactor accident at the San Onofre Nuclear Generating Station. Fire crews from the Los Angeles County Fire Department and the U.S. Forest Service moved in to contain the flames, while state emergency managers opened a real‑time radiation monitoring network around the former plant. Emails released by Inside Climate News show that the state’s Office of Emergency Services coordinated with the U.S. Nuclear Regulatory Commission and the Department of Energy to deploy mobile dosimeters and air‑sampling stations within hours of the fire’s approach.

The incident matters because San Onofre is one of the largest nuclear sites in the United States and a former reactor suffered a catastrophic core melt in 1979, releasing significant amounts of radioactive material into the surrounding environment. Though the plant was shut down in 2013, residual contamination remains in the soil and groundwater. With California’s record‑dry conditions and the increasing frequency of wildfires driven by climate change, the risk of fire‑related airborne release of radionuclides has surged. Local residents and environmental groups have long warned that a wildfire could mobilise buried radioactive particles and spread them across the Los Angeles basin.

According to the leaked emails, the state deployed 18 mobile radiation detectors and 12 air‑sampling units along a 15‑mile perimeter around the plant. Data were transmitted in real time to a central command center in Irvine, where officials monitored radiation levels and fire behaviour. The fire was contained within 48 hours, but the monitoring network remained active for seven days after containment to track any delayed release of contaminants. Emergency managers held a press briefing that afternoon, assuring residents that radiation readings stayed below the federal threshold of 0.01 millisieverts per hour. A spokesperson for the California Department of Public Health noted that the public should continue to avoid the area until a full environmental assessment is completed.

The incident has prompted calls for a review of emergency protocols at former nuclear sites nationwide. The California legislature is considering a bill that would mandate a dedicated rapid‑response radiation monitoring team for all decommissioned reactors. Meanwhile, the U.S. Department of Energy has announced a joint study with the National Oceanic and Atmospheric Administration to model the dispersal of radionuclides during wildfires. The outcome of that study could shape fire‑fighting strategies in the future, ensuring that the risk of radioactive contamination is minimized as California’s fire season continues.