SAN DIEGO — A pair of dismantled pressurizers that departed the San Onofre Nuclear Generating Station by rail had to be returned to the now-shuttered power plant after it was discovered that one of the giant pieces of equipment had leaked fluid during the trip.

Surveys conducted by the plant’s operator, Southern California Edison, said “no detectable radioactivity” above otherwise normal background levels were detected and there was “no threat to public health and safety, or the environment.” But an official with the utility admitted to the Union-Tribune, “that should not happen.”

An inspection from the U.S. Nuclear Regulatory Commission found two violations but the federal regulator’s report described the “safety significance” of the infractions as “low.”

The NRC’s inspection report made no mention of issuing any fines.

But Edwin Lyman, director of nuclear safety at the Union of Concerned Scientists, suspects the NRC’s report does not reflect “the severity of (Edison and its contractor’s) screw-up.”

“They had one job to do, which was to transport this pressurizer without any freestanding liquid in a container that couldn’t leak,” Lyman said. “And they missed on both counts.”

Ron Pontes, Southern California Edison’s general manager for environmental radiation protection and waste, said SCE takes “seriously our responsibility” to properly package and transport waste.

“This package did not meet our expectations, and we are performing a careful evaluation to learn from the event and prevent a reoccurrence with similar shipments in the future,” Pontes said.

What happened?

The San Onofore Nuclear Generating Station, known as SONGS for short, is in the midst of a massive $4.7 billion decommissioning and dismantlement project that is scheduled to wrap up by the end of 2028.

During the course of the demolition, about 1.1 billion pounds of material is expected to be removed, with most of it going by rail. More than 1,000 rail shipments originating from a spur built at SONGS have left the site since dismantlement efforts began some four years ago.

In late June, two large pressurizers were loaded onto special rail cars, on their way to a disposal site in Clive, Utah.

When a nuclear power plant is in operation, pressurizers control reactor coolant systems that use demineralized pure water that remove heat from the reactor core and allow steam to power turbine generators.

The SONGS Unit 2 and Unit 3 pressurizers are big — 37 feet tall and weighing about 100 tons each, with capacity to regulate 16,500 gallons of liquid.

After they were taken out, the pressurizers were labeled as Class A waste, which is the lowest level of radioactive waste as classified by the NRC.

At a stop at a railyard in San Bernardino, a worker noticed a water leakage on the top of the flatbed railcar hauling the Unit 2 pressurizer. SCE officials said the water did not drip onto the ground.

No leaks were found in the Unit 3 pressurizer but both were sent back to SONGS to find out what happened.

Although each pressurizer was supposed to be completely drained, it was soon discovered that 190 gallons of water was found at the bottom of the Unit 2 pressurizer.

“Workers incorrectly believed” all the water had been drained out of the pressurizer before it was loaded onto the rail car, Pontes said.

What now?

An ongoing investigation is trying to determine what went wrong. Until then, the pressurizers from both units will not be rescheduled for shipment back to Utah.

The NRC noted two violations — one for failing to ensure the pressurizer was “properly closed and sealed to prevent release of radioactive content” and the second for not properly packaging it for shipment.

Pontes said the NRC findings are being reviewed by SCE, the dismantlement’s general contractor (called SONGS Decommissioning Solutions) and workers at the facility. “We remain committed, in our oversight role, to ensuring safety and adherence to all regulatory material packaging requirements,” he said.

But Lyman questioned whether the NRC’s actions amounted to a “slap on the wrist.”

“When they process these violations through their system and it spits out ‘low-safety significance,’ I don’t feel it conveys the gravity of the two violations, when compounded, led to a release of this liquid,” Lyman said. “It could have been worse, presumably.”

Other incidents

First opened in 1968, SONGS has not produced electricity since 2012 after a leak in a steam generator tube led to its closing.

In August 2018, a 50-ton canister filled with radioactive spent fuel was being transferred to a dry storage facility on the north end of SONGS. While being lowered into a cavity, the canister was accidentally left suspended almost 20 feet from the floor.

Eventually, the canister was safely lowered but the NRC later fined Edison $116,000 and chided the company for failing “to establish a rigorous process to ensure adequate procedures, training and oversight guidance.”

In April 2022, demolition work was briefly halted after a worker fell about five feet while trying to install a ventilation hose into the floor vault opening, injuring his shoulder.

Once the dismantlement project wraps up, all that is expected to remain at SONGS will be two dry storage facilities; a security building with personnel to look over the waste; a seawall 28 feet high, as measured at average low tide at San Onofre Beach; a walkway connecting two beaches north and south of the plant, and a switchyard with power lines.

The switchyard’s substation without transformers stays put because it houses electricity infrastructure that provides a key interconnection for the power grid in the region.

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