By John Stang
Holtec International has sought to allay concerns about a broken bolt in one of the canisters being used to move and store spent fuel at the San Onofre Nuclear Generating Station (SONGS) in California.
“All of the safety criteria in the SONGS (interim dry storage facility) are fulfilled even if one postulates that every bolt (all 88 bolts in the canister) were somehow to vanish from the canister,” the company said in a white paper issued after a March used fuel transfer stoppage at the plant.
Following SONGS’ premature closure in 2013, used fuel from its two last operational reactors has remained in wet storage for cooling. In 2014, plant majority owner Southern California Edison selected Holtec, a New Jersey-based energy technology company, to expand the facility’s on-site fuel storage pad to accommodate the additional material.
Roughly one-third of SONGS’ spent reactor fuel is already held in 51 canisters in an on-site independent spent fuel storage installation. That radioactive waste is from the plant’s reactor Unit 1, which shut down in 1992. Another 73 canisters of fuel, from Units 2 and 3, are now being placed into underground storage via Holtec’s HI-STORM UMAX system.
Relocation of this material is expected to be complete in mid-2019. Five canisters of spent nuclear fuel have been moved to date, one after the work stoppage was lifted, according to Southern California Edison spokeswoman Maureen Brown.
Of the 73 Holtec International-built canisters, 30 are of an older design and 43 are of a newer design. Before used-fuel assemblies were put in a fifth canister, workers found a broken pin in the container. That halted work from March 5 to March 15 as SCE and Holtec reviewed the situation, honing in on a change in the canister construction process. The utility is continuing waste transfers using the 30 older model canisters.
The interior of Holtec’s spent fuel canister has 37 long rectangular chambers that each hold up to 37 spent fuel assemblies. “Basket shims” are placed around the interior of a canister’s walls to keep the long rectangular chambers in place and enable circulation of helium used to cool the fuel assemblies. The broken pin was one of 88 in each canister to hold the shims in place.
A March 30 Holtec memo concluded the bolt could have been damaged if it became loose during the “peening” process, when a laser beam strikes the canister as it spins to improve its strength. Another possibility is that workers might have improperly lowered the shim into the cask, the memo said. The memo described the likelihood of these scenarios as “isolated instances.”
The March 30 memo concluded that cask would still safely contain the radioactive fuel even if all of the bolts were damaaged.
The remaining 39 newer canisters at the plant have been recalled.
The broken bolt came from a manufacturing process “that is not common to all canisters,” Holtec said in a March 23 statement. The other canisters did not go through that separate process.
Holtec’s white paper said the newer style of canister featured a redesigned shim to aid in the manufacturing of the casks and to improve the cooling of the fuel. “This was nothing out of ordinary: minor changes to the equipment design are routinely made under the NRC-sanctioned (regulations). … The ’old’ design, like the new design, is not known to have anything wrong with it,” the company said.
Ray Lutz, who leads the El Cajon, Calif., watchdog group Citizens’ Oversight, said he was not convinced by Holtec’s conclusions that no danger existed. “It concerns me that this defect surfaced so quickly. We’re still interested in finding out why. … Why wasn’t it caught before they were using it,” he told RadWaste Monitor.
The Orange County Register reported that Holtec alerted the Nuclear Regulatory Commission and several reactor sites that have received the new canisters, including plants in Illinois, Mississippi, Georgia, Vermont Yankee, Washington state, Tennessee, and Missouri.
The Vermont Yankee power plant, closed since 2014, uses a different design of canister than is employed at SONGS, said Joe Lynch, senior government affairs manager at facility owner Entergy. Vermont Yankee halted its own spent fuel transfer on March 10 to examine all of Holtec canisters at the site. Entergy has not determined when it will resume the work, Lynch said.
The spent fuel from San Onofre will ultimately be transported to another location, but when and where is not yet known.
An expert panel met March 27 to begin preparing recommendations for potential locations for off-site storage of spent fuel, along with a plan for moving the radioactive waste, SCE spokeswoman Brown said. A date for the panel’s next meeting has not been released.
Establishing the panel was one component of the 2017 settlement agreement to resolve a lawsuit filed by Citizens’ Oversight against the state permit that authorizes SCE to place all the used fuel on an expanded storage pad near the Pacific Ocean. The agreement requires the utility to take “commercially reasonable” steps to relocate the 3.55 million pounds of waste off-site, but in the meantime it can proceed with its original plan.
Southern California Edison had its six-person expert panel in place by March 8. The members are: Kristopher W. Cummings, a used fuel specialist at Curtiss-Wright Corp.; Thomas Isaacs, former director of the U.S. Department of Energy’s Office of Policy; Allison Macfarlane, former chairman of the U.S. Nuclear Regulatory Commission; Gary Lanthrum, former director of the National Transportation Program for DOE’s planned Yucca Mountain repository; Richard C. Moore, a consultant with a focus on transportation of radiological materials; and Dr. Josephine Piccone, a former U.S. representative to the International Atomic Energy Agency Radiation Safety Standards Committee.
Southern California Edison has 30 calendar days to solicit the group’s input on strategic and transportation plans for the spent fuel. That is due to happen by April 7, according to SCE’s latest update on the settlement agreement.
Citizens’ Oversight recommended Macfarlane, Isaacs, and Moore to the panel, Lutz said. “We’re pretty happy with it,” he said.
Charles Langley, executive director of the San Diego County-based Public Watchdogs, which is continuing a separate legal battle to stop radioactive waste storage at SONGS, was skeptical of the panel’s effectiveness. “It doesn’t create a new situation. It doesn’t enforce anything.”
There has been talk of moving the spent fuel to the Palo Verde nuclear plant in Arizona, for which SCE is a minority owner, but the update indicates that remains a nonstarter. The settlement agreement gave SCE 90 days to make a formal request for Palo Verde to take the waste, which it did in October. But site majority owner Arizona Public Service has stated directly it has no interest in accepting the material, and other owners took the same position during an October meeting of Palo Verde’s Administrative Committee.
