Fluid leak forces rail transport to return to San Onofre nuclear plant

Two dismantled pressure vessels that had left the San Onofre Nuclear Power Plant by rail had to be returned to the now-closed power plant after it was discovered that fluid had leaked from one of the huge pieces of equipment during the journey.

Investigations by the power plant operator Southern California Edison found that “no detectable radioactivity” was found above normal background levels and that there was “no threat to public health and safety or the environment.” But an official from the utility admitted to the Union-Tribune that “this should not be happening.”

An inspection by the U.S. Nuclear Regulatory Commission found two violations, but the federal regulator's report described the “safety relevance” of the violations as “low.”

The NRC's inspection report did not mention the imposition of any fines.

But Edwin Lyman, director of nuclear safety at the Union of Concerned Scientists, suspects that the NRC report “does not reflect the severity of the error (by Edison and his contractor).”

“They had one job to do, which was to transport the pressure vessel in a sealed container with no freestanding liquid,” Lyman said. “And they botched both jobs.”

Ron Pontes, Southern California Edison's general manager of radiation protection and waste, said SCE takes “its responsibility” to properly package and transport waste seriously.

“This package did not meet our expectations and we are conducting a careful assessment to learn from the incident and prevent such an incident from happening again with similar shipments in the future,” Pontes said.

What happened?

The San Onofore Nuclear Power Plant, or SONGS for short, is in the midst of a massive $4.7 billion decommissioning and dismantling project that is scheduled to be completed by the end of 2028.

During the demolition, around 500,000 kilograms of material are expected to be transported away, most of it by rail. Since demolition work began around four years ago, more than 1,000 rail transports have left the site, originating from a branch built at SONGS.

At the end of June, two large pressure vessels were loaded onto special railroad cars and taken to a disposal site in Clive, Utah.

When a nuclear power plant is operating, pressurizers control the reactor cooling systems, which use demineralized pure water to remove heat from the reactor core and generate steam to drive turbine generators.

The pressurizers on SONGS Units 2 and 3 are large—each 37 feet tall, weighing about 100 tons, and with a capacity of 16,500 gallons of fluid.

After their removal, the pressurizers were designated as Class A waste, which is the lowest level of radioactive waste according to the NRC classification.

At a stop in a rail yard in San Bernardino, a worker noticed a water leak on the roof of the flat car carrying Unit 2's pressure vessel. 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 had happened.

Although all pressurizers were supposed to be completely drained, it was soon discovered that there were 190 gallons of water at the bottom of Unit 2's pressurizer.

“The workers mistakenly believed” that all the water had been drained from the pressurizer before it was loaded onto the railroad car, Pontes said.

What now?

An ongoing investigation is intended to clarify what went wrong. Until then, the return transport of the pressure vessels of both units to Utah will not be rescheduled.

The NRC found two violations: First, it was not ensured that the pressure vessel was “properly closed and sealed to prevent the release of radioactive material,” and second, the vessel was not properly packaged for transport.

Pontes said the NRC's findings will be reviewed by SCE, the general contractor for the dismantling (SONGS Decommissioning Solutions), and workers at the plant. “We remain committed to our oversight role in ensuring safety and compliance with all regulatory requirements for material packaging,” he said.

Lyman, however, doubted that the NRC's measures amounted to a “slap on the wrist.”

“When they process these breaches through their system and it spits out 'low safety significance,' I don't think it reflects the severity of the two breaches that combined to lead to the release of that fluid,” Lyman said. “It probably could have been worse.”

Other incidents

SONGS opened in 1968 but has not produced electricity since 2012 after it was forced to close due to a leak in a steam generator line.

In August 2018, a 50-ton container of radioactive spent fuel was being moved into a dry storage facility at the north end of SONGS. While being lowered into a cave, the container accidentally became stuck nearly 20 feet above the ground.

Eventually the container was safely lowered, but the NRC later fined Edison $116,000 and reprimanded the company for failing to “establish a rigorous process to ensure appropriate practices, training and oversight policies.”

In April 2022, demolition work was briefly halted after a worker fell from a height of about 1.5 meters while attempting to install a ventilation hose into the opening in the floor vault, sustaining a shoulder injury.

When the dismantling project is complete, SONGS is expected to have only two dry storage facilities remaining; a containment building with personnel to monitor waste; a seawall 28 feet high at average low tide on San Onofre Beach; a walkway connecting two beaches north and south of the facility, and a switchboard with power lines.

The substation without transformers of the switchyard will remain where it is because it houses electrical infrastructure that is a key link for the region's power grid.

Originally published: August 21, 2024 at 2:47 pm