Edison looking into best dry storage for Onofre’s nuclear waste

Second of two parts on the storage of used radioactive fuel at the San Onofre Nuclear Generating Station.

A community group thrust the issue of storing nuclear fuel at the San Onofre Nuclear Generating Station into the spotlight in December when members complained about the slow timetable for removing radioactive waste at the closing plant.

Let Laguna Vote worried that San Onofre, located steps from the ocean and near the 5 Freeway, is susceptible to earthquakes, tsunamis and terrorist strikes.

The Laguna Beach City Council followed up by adopting a resolution that urges the U.S. Department of Energy to fast-track a plan to move spent nuclear fuel to a more remote location.

Southern California Edison closed the facility in June 2013 after a faulty steam generator leaked radioactive coolant. Edison stored the used nuclear waste on-site by placing bundled, spent fuel rods in two pools of water, where they will cool in 23 feet of water for five to seven years.

After the rods cool, the plan is to move them into concrete canisters, a procedure called dry cask storage, and house them on the site.

For about a year, Edison officials have been meeting to consider the best means for safely storing spent fuel rods. Dry cask storage was discussed at an October meeting of nuclear experts and the public. Officials responded to questions from representatives of activist group San Onofre Safety, who wanted to know why thicker canisters like those used in Europe weren’t being used here.

Tom Palmisano, San Onofre’s vice president and chief nuclear officer, said Edison considered a German company’s design for storage of remaining used nuclear fuel at the shuttered plant. Certain models of Siempelkamp cast-iron canisters are thicker than what industry counterparts provide as a barrier against leaking radioactive fuel.

The problem with the German design is that the product is not licensed for transport or storage in the United States, and the weight of each cask would require substantial upgrades to the spent-fuel cranes and handling equipment, Palmisano said.

After public meetings, Edison selected New Jersey-based Holtec International and is awaiting the Nuclear Regulatory Commission’s approval to place the remainder of its spent nuclear fuel in 80 stainless steel canisters set partially into the ground.

Holtec’s canisters, which weigh 45 tons, will be set vertically and topped with a 12-ton steel and concrete lid, which will be exposed to air, Palmisano said.

The company said the canisters are made of the most corrosion-resistant grade of stainless steel.

“We took a good look at systems, and Holtec was a newer design, post 9/11,” Palmisano said. And the partial burial of the canisters offers “safety and security advantages,” he added.

Even with portions of the canisters below ground, the San Onofre Safety group is concerned that the canisters could be susceptible to corrosion and cracking, given the plant’s marine adjacency.

The Electric Power Research Institute, an independent, nonprofit agency that researches the electricity industry, agrees.

“The most likely degradation mechanism at marine sites is chloride-induced, stress-corrosion cracking, created when sea salt deposits form on the canister surface,” according to a 2013 institute report. “The shell and associated welds are judged to be of greater susceptibility than the canister lids, since the lids are three to 18 times thicker than the shell.”

If a crack were to develop on a half-inch thick canister, it would take more than 80 years for it to cut through the steel, Brian Schimmoller, communications manager with the Electric Power Research Institute, wrote in an email. The timeline pertains to a canister exposed to a temperature 35 degrees Celsius higher than the ambient temperature.

The Holtec canisters planned for San Onofre will be five-eights of an inch thick.

“Nothing is corrosion-proof, but there are ways to mitigate it,” Thomas Eiden, a nuclear engineer at the Advanced Test Reactor at the Idaho National Laboratory, wrote in an email. “One such way is by using a coating over the susceptible area.”

He added that observers have to watch for problems and “monitor the health of your material if you find [them].”

A concrete overpack would provide an extra layer of protection if a leak were to occur, Eiden added.

The stainless steel canisters will be set in a concrete sleeve, then lowered into the ground.

“If there was a failure in the liner, and if the cask was storing a failed fuel assembly, a minute amount of radioactive gas could leak, akin to a soda can that is partially open and you can hear the carbon dioxide hissing as it escapes the can,” Eiden said. “This gas would quickly be diluted in the atmosphere into an inconsequential concentration.”

Holtec is developing inspection methods for the underground system, company President and CEO Kris Singh wrote in an email.

“One option will be to perform an examination through the air vents located in the lid of the [canister],” Singh said. “Another is to potentially raise the canister into a transfer cask for inspection.”

No Holtec dry storage canister has ever leaked, Singh said.

Holtec has underground storage canisters at Humboldt Bay in Northern California and at the Callaway Nuclear Plant in Fulton, Mo.

Edison has also contacted the Electric Power Research Institute about researching canister-inspection techniques and is considering purchasing two empty canisters for practice, Palmisano said.

The state Coastal Commission must approve permits before excavation begins, he added.

Canisters could go into the ground as early as 2017.

Meanwhile, Laguna Beach resident Marni Magda is reaching out to high-ranking officials in hopes of spurring legislation to remove fuel from the shuttered plant.

Magda, who has spent four years researching the nuclear industry, said she and fellow Laguna resident Audrey Prosser met with staff members of Sen. Barbara Boxer (D-Calif.) on Feb. 6 in San Diego.

Magda and Prosser urged the senator to advocate for a temporary space at a remote military base — where a no-fly zone would be in effect and the fuel would be guarded by trained personnel — to store the state’s radioactive waste.

“Our own well-trained military will protect the fuel from sabotage and human error, saving the taxpayers millions of dollars a year,” Magda said in a letter to the Coastline Pilot. “The taxpayer funded the industry to build the nuclear reactors that made electricity for only 40 years. The industry made enormous profit but is exempt from costs of protecting nuclear waste.”

Palmisano said the company is trying to regain public trust after the leak by holding public-engagement meetings every few months and offering tours of San Onofre to educate people about decommissioning.