Data From Spent Fuel Storage Area Monitors Available Online

ROSEMEAD, Calif., March 10, 2020 — Data is available online from radiation monitors Southern California Edison installed at the San Onofre nuclear plant’s dry fuel storage facility. Three monitors, and a fourth providing a baseline reading, collect the data. That information is fed directly to three off-site agencies: the California Department of Public Health’s Radiologic Health Branch, California State Parks and the city of San Juan Capistrano. The department posts a monthly report on the monitor readings to its website for the public to access.

“We’re committed to sharing information during decommissioning. That’s why we’ve worked with our community and agency partners to install this system to enable public agencies to monitor radiation dose readings. Going above and beyond Nuclear Regulatory Commission requirements to share this data with local agencies is consistent with our goals of keeping the public informed,” said Ron Pontes, SCE manager of Environmental Decommissioning Strategy.

The only other U.S. nuclear plant to employ such a system is Prairie Island in Minnesota.

The newly installed monitors detect levels of gamma radiation emitted by the spent nuclear fuel, as well as the general background radiation that is present all the time. The monitors measure this dose in microrem per hour (a microrem is a thousandth of a millirem). The National Council on Radiation Protection and Measurements has determined the average annual radiation dose per person in the U.S. (from all sources) is 620 millirem or 620,000 microrem. That number includes naturally occurring dose from the sun, air travel and food, as well as manmade sources such as medical and dental X-rays.

While SCE continues to move spent fuel from wet to dry storage, readings may be elevated briefly as canisters of spent nuclear fuel pass by the monitors. For instance, on Feb. 28, the day a canister was moved to the storage pad, the maximum reading was 0.337 millirem per hour. The day before, and the day after, the maximum reading was approximately 10 times lower. For the public, the dose at the site boundary is primarily from the natural background radiation that exists all around us.

“What people will see in the reports is the very, very low radiation dose levels on our spent fuel storage pad and they can feel comfortable the fuel is well-shielded and well-protected,” Pontes said.

Spent Fuel Storage at San Onofre

SCE first transferred spent fuel assemblies from wet (pool) storage to the dry cask storage units in the TN-NUHOMS system in 2003. Fifty canisters of spent fuel are stored in the NUHOMS system. Fuel was first loaded into Holtec HI-STORM UMAX dry storage system in January 2018. Loading of the UMAX system is ongoing with expected completion this summer. The Holtec system will house 73 canisters of spent fuel. SCE has safely stored spent fuel at San Onofre in wet and dry storage for more than 50 years.

Learn more about spent fuel storage at San Onofre by visiting the SONGS Community website.

About Southern California Edison

An Edison International (NYSE:EIX) company, Southern California Edison is one of the nation’s largest electric utilities, serving a population of approximately 15 million via 5 million customer accounts in a 50,000-square-mile service area within Central, Coastal and Southern California. 

Media Contact: John Dobken, (626) 302-2255