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Fateful day at San Onofre: All spent fuel emptied from cooling pools, clearing way for plant dismantling

Historical photo of Unit 1 fuel loading. Courtesy Southern California Edison.

The nuclear odyssey that began in 1968 — when Lyndon B. Johnson was president, Apollo 8 orbited the moon and nuclear power was championed as a pillar of progress — has taken a fateful turn.

The final fuel rods cooling in San Onofre Nuclear Generating Station’s spent fuel pools have been loaded into a stainless steel canister that’s slated to slide into a dry storage vault on Friday, Aug. 7. That’s more than 50 years after the plant’s original reactor first opened for business and closely coincides with the 75th anniversary of the Hiroshima bombing, which marked the dawn of the “nuclear age.”

“Transfer of all of the spent fuel into dry cask storage represents a major milestone in the ongoing decommissioning of San Onofre,” said Victor Dricks, a spokesman for the Nuclear Regulatory Commission, by email.

“The NRC will continue to have a frequent presence on site through our decommissioning oversight and inspection program and we will maintain close contact with Southern California Edison to ensure the spent fuel is stored safely and securely on site.”

While Edison is focused on safely storing this last canister and fully completing fuel transfer operations, said Vince Bilovsky, Edison’s deputy decommissioning officer, “Next week, we do begin a new chapter at SONGS as we become mostly a deconstruction site.”

The Holtec Hi-Storm Umax dry storage system for spent fuel at San Onofre Nuclear Generating Station. (Courtesy Southern California Edison)

This clears the way for the arduous, decade-long, $4.4 billion demolition of the retired San Onofre plant and its iconic twin domes to begin in earnest. It also marks the end of the fraught fuel-transfer process, which was marred by human error and a “near-miss” that halted work for nearly a year and evoked fear and mistrust among critics already predisposed to doubt Edison — as well as demands from lawmakers that the NRC station a full-time inspector at San Onofre until all fuel was in dry storage.

The NRC said full-time inspectors are for operating reactors, not for shuttered plants, but conducted more  inspections to keep an eye on the work. The NRC’s most recent inspection report, dated Aug. 4, found no violations, but noted one “crane human performance issue” and corrosion on vacuum bags filled with detritus from previous cleanings of the spent fuel pools.

There have been three reactors at San Onofre. Unit 1, the original, ceased operations in 1992, and its fuel has been in dry storage for years. Units 2 and 3 came online in the early 1980s and powered down in 2012, after premature wear was found on tubes in the new steam generators that were supposed to give the plant decades more life.

After pitched battles on if, when and how to restart the reactors, Edison decided to shutter them permanently in 2013.

Inspection revelations



The NRC noted an incident involving a crane late on May 5 in the Unit 3 fuel building. While lowering a transfer cask with an empty canister into the pool for loading, the crane operator “over-traveled in the downward direction” with the crane’s hook, causing its wire ropes to become “somewhat slack.”

The crane operator raised the load block to regain tension and unhooked the transfer cask. A plate around the crane’s load block had bent, and a wire rope had moved outside its normal position. It was repaired, inspected and tested before returning to service, and the NRC concluded that Edison’s corrective actions were appropriate.

Google Earth image of the Holtec dry storage system San Onofre Nuclear Generating Station. (Image courtesy of Google Earth)

The second item noted by the NRC was corrosion on waste containers stored in the pools. Back in 1991, Edison did a cleanup of the pools themselves, “vacuuming up small fuel detritus and various foreign materials.” Fine stainless-steel mesh bags were used as vacuum filters, and those were placed inside waste containers with pencil-sized holes so water could completely cover the detritus inside.

On May 28, while preparing to remove fuel from the Unit 2 pool, “corrosion products were observed on the exterior surface and trailing out of the drain holes” of a waste container, the NRC said. Chemical analysis concluded that the corrosion was chromium, iron and nickel, the major components of the vacuum filter bags, due to the pools’ normal high-acidic environment and other factors. Once the waste canisters were completely dried, “the corrosion process would be arrested and preclude any further degradation,” the NRC concluded.

What’s next?

More than 300 tons of asbestos-containing material have been safely shipped off-site, and the focus of work now turns to the containment domes themselves, Edison spokesman John Dobken said.

Larger access openings will be cut, vertical and horizontal tension cables will be removed, and cranes will move inside.

Much has changed since Unit 1 was torn down. While Edison stored the enormous Unit 1 reactor pressure vessel on site for years before recently shipping it off to Utah, new technology will allow Unit 2 and 3’s reactor vessels to be cut up into pieces. Some will go into dry storage on site; others will eventually join Unit 1’s vessel in Utah.

Experts say that dry storage is safer than fuel pools. San Onofre’s “concrete monolith,” made by private

Southern California Edison’s timetable for San Onofre’s teardown.

contractor Holtec International, can withstand twice the ground-shake in an earthquake as the plant itself. It’s also “passive,” requiring no water or electricity to cool the fuel.

But a “nuclear waste dump” shouldn’t be 108 feet from the ocean, in an earthquake zone and within 50 miles of 8 million people, according to elected officials, critics and even Edison. But until the federal government fulfills its contractual obligation to permanently store commercial nuclear waste — or temporary storage sites are licensed — there’s no place else for it to go.

“During this time, the organization will continue to manage fuel storage to maintain safety, while also providing oversight of our decommissioning contractor throughout the dismantlement of the plant,” said Edison’s Bilovsky.

Source: Orange County Register

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