San Onofre Nuclear Plant, Erosion Concerns Over Nuclear Waste Storage

Part of the Southern California coast has collapsed and been swallowed by the sea. High surf and flooding caused by a distant ocean hurricane washed over the seawall. In response, attention has grown toward the spent fuel at the shuttered San Onofre Nuclear Generating Station. In reporting by Slashdot’s EditorDavid, concerns of oceanographers as covered by the Los Angeles Times are introduced.

The plant is located on the coast near San Clemente. The reactors have already shut down, but high-level waste remains on site. While demolition of the twin domes is ahead, no destination for the fuel has been decided. If coastal erosion continues, it could undermine the premises of the storage facility.

Coastal Collapse Advancing on the Southern

California Coast

This collapse was caused by Hurricane Marie, which occurred far out in the Pacific. Swells reached the coast and scoured boardwalks and slopes. In some sections, the foundations of walkways were exposed and access was restricted. The high waves were not transient, but repeatedly struck the seawall.

Kim McCoy, an oceanographer and former wave dynamics researcher, felt a sense of crisis at the sight. She has long opposed storing nuclear waste on the coast. What she had in mind was waste set in concrete. The storage containers are 100 feet from the walkway that protects the seawall.

She referred to rising sea levels, storm waves, and the El Niño phenomenon that increases wave height. If part of the walkway is washed away, the protective function of the seawall would decline. She warned of that situation as follows.

“Rising sea levels, storm waves, El Niño which increases wave height … these could wash away a section of the walkway that protects the San Onofre seawall”

This statement does not assert a catastrophe in the near future. Rather, it urges preparation for long-term topographic change. In coastal engineering, single storms and cumulative erosion are evaluated separately. The recent waves are significant in that they made the progress of the latter visible.

San Onofre Plant’s Waste Storage System

The San Onofre plant has already finished generating power. Its distinctive two reactor domes will begin demolition early next year. Meanwhile, about 3.6 million pounds of high-level waste remain on the site. By dry storage, it is sealed in steel containers placed on concrete pads.

The containers stand in rows on low ground close to the shoreline. Because they are exposed to sea breezes, corrosion control of the steel is essential. External degradation from salt and the establishment of inspection methods are challenges. It is a storage system premised on monitoring and repair.

The containers are said to have a design life of 100 years. By 2103, some of the containers will approach that life. At that time, repackaging into new containers will be necessary. The repackaging work itself will require exposure management and transfer of technical expertise.

Sea-Level Rise and Long-Term Risks:

Sorting the Issues

James Day, a geologist at the University of California, San Diego, emphasized a long-term perspective. He pointed out that the hazardous period of the waste extends over hundreds to thousands of generations. While noting that the current situation is under control, he argued for thinking on a geological time scale. His position is that short-term safety and long-term suitability of the site should be distinguished.

He said the ground at San Onofre lies on relatively young bedrock. He expressed the view that it is a seismically active region and unsuitable as a place to leave waste. Similar concerns were raised at a meeting of the Scripps Institution of Oceanography. There was also an opinion that slope failure heightens vulnerability to tsunamis.

Many experts consider the possibility of erosion damage in the near future to be extremely low. However, low probability is not synonymous with no countermeasures. Seawalls, tsunamis, earthquakes, and corrosion must be evaluated together. Decision-making under uncertainty is required.

Safety Basis and Measures Presented by

the Operator

Southern California Edison, the owner, asserts safety. Manuel Camargo, in charge of decommissioning, said that even the maximum credible tsunami would not overtop the seawall. He also addressed a maximum credible earthquake of around magnitude 7.0. He explained that such shaking would remain at about half the design strength of the storage system.

The company is reinforcing the walkway below the seawall. The evaluation was based on state data from the California Ocean Protection Council. As a result, it concluded that the seawall will not be submerged before 2050. It plans to monitor the integrity of the containers on the concrete pads.

The company has indicated to the California Coastal Commission the conditions for relocation. If predictive models of sea-level rise and erosion show problems, it will move the waste to higher ground within the site. This is a vertical retreat within the site, not removal offsite. Defining the benchmark water levels and erosion amounts will be the focus going forward.

Structural Challenge of Continued Storage

Without a Permanent Repository

Under the original plan, the waste was to be shipped to a deep geological repository. The project at Yucca Mountain in Nevada was to serve as that destination. However, the project did not advance due to political conflict and stalled licensing. As a result, interim coastal storage has become permanent.

The absence of a permanent repository is not a problem unique to San Onofre. Across the United States, no destination for spent fuel has been set. Local communities bear the storage burden after the benefits of generation. The difficulty of consensus-building further complicates the technical challenges.

The burden of maintaining long-lived infrastructure is also common in the field of information technology. For example, as the migration work shown in End of Chrome Manifest V2, the Demise of Ad Blockers Like uBlock Origin illustrates, renewal planning beyond the design life is essential. For nuclear facilities, that period is orders of magnitude longer. Institutional design including preservation of records and transfer of expertise is needed.

Editorial Opinion

Regarding short-term impacts. In the next 3 to 6 months, we expect inspections of the seawall and walkway to be strengthened. Predictive models may be revalidated and reinforcement work schedules reviewed. Consultations between local governments and the operator are expected to increase in frequency. We assess that the yardstick for relocation decisions will become the center of debate.

Regarding the long-term perspective. In the 1- to 3-year range, we expect demolition of the reactor domes to proceed, making clearer a picture in which only the waste remains. We assess that corrosion monitoring of containers and establishment of repackaging procedures will become technical challenges. If repository policy does not move, we expect arguments for relocation to higher ground within the site to strengthen. We assess that sorting out cost burdens and responsibility sharing will be unavoidable.

We pose questions from the editorial team. At what water level and amount of erosion should relocation begin. Who will verify those criteria. Which organization will inherit records spanning hundreds of generations. We assess that the current continuation of interim storage without answers to these questions is a challenge for both technology and institutions.

References

• “As Part of California’s Coast Begins to Crumble, Is the Clock Ticking on Moving Radioactive Waste?”, by EditorDavid — Slashdot, 2026-09-16T22:04:00.000Z (ARR)
• Source URL: https://hardware.slashdot.org/story/26/09/14/0536219/as-part-of-californias-coast-begins-to-crumble-is-the-clock-ticking-on-moving-radioactive-waste?utm_source=rss1.0mainlinkanon&utm_medium=feed