Near-Miss Accident at San Onofre

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Text of story as of 09-25-18:

‘Serious Near Miss’ Accident at San Onofre Sparks NRC Investigation

Expert warns of the potential for a catastrophic event after San Onofre workers nearly dropped a canister of nuclear waste last month.

A near-miss accident at the San Onofre Nuclear Generating Station could have been catastrophic. NBC 7’s Mari Payton has more with NBC 7 Investigates. (Published Monday, Sept. 24, 2018)

A “serious near miss” accident at the San Onofre Nuclear power plant could have been catastrophic.

On August 3, a steel canister filled with hot nuclear waste was being lowered twenty feet into underground storage at San Onofre when the canister was accidentally hung up on a quarter-inch piece of metal. The canister was stuck for forty-five minutes while workers tried to figure out what happened.

Workers were able to keep the canister from falling but the incident has now led to the Nuclear Regulatory Commission (NRC) investigating. Recently, NRC Inspectors wrapped up a four-day, inspection, triggered by the incident.

A spokesperson for Southern California Edison admits the incident was a “serious near-miss”.

“SCE has been fully cooperating with the [NRC] team, providing access to people, records, root cause evaluations, and corrective actions related to the canister handling incident on Aug. 3,” said Liese Mosher with Southern California Edison. “We will continue to do so as the NRC team returns to their offices to analyze the data and complete their work.”

Mosher added that nuclear waste canister loading process will not be resumed “until the NRC has completed its actions, and both [Southern California Edison] and the NRC are satisfied that all corrective actions have been addressed.”

Since then, nuclear safety experts and critics have raised concerns over what might have happened if the 49-ton steel canister, which held the radioactive materials, had come free and crashed to the cement floor on the San Onofre site.

The August canister was the 29th to be moved as the plant continues its decommissioning process.

San Onofre workers are in the process of moving the dangerous radioactive waste out of short-term storage in a deep water pool to a “dry storage” underground and a short distance away on the San Onofre site. When the waste is being moved, the canisters are wrapped in a larger 70-ton protective container or “cask”. The canisters come out of the protective container when lowered into the underground storage.

It was at this step in the process when the canister nearly fell in August.

Holtec International is the maker of the system and containers that hold the nuclear waste canisters. The New Jersey-based company sell various systems to clients across the United States including the Hi-Storm Umax model used at San Onofre.

NBC 7 Investigates reached out to Holtec International but they did not respond to our questions. Instead, they directed us to Southern California Edison for a response.

An expert on nuclear waste, Dr. Tom English agrees with the decision to stop loading until all questions are answered. English spent time as an advisor to the State of California and Carter Administration regarding the disposal of nuclear waste.

“The computer simulations that have been performed for San Onofre were for a drop of the canister that is protected by the massive transfer cask. No San Onofre computer simulations have been done on an 18-foot dropping of an unprotected nuclear waste canister,” English told NBC 7 Investigates.

English’s experience paid off when he found within the NRC’s massive records archive, a “canister drop” simulation performed in 2007. The NRC computer simulation predicted the potential catastrophic results that could come from a nuclear waste canister smashing onto the ground from two-stories high.

“What they did was they dropped a canister essentially onto concrete,” English said. “There are some differences in terms of the thickness of the canister and the weights and so forth but the general idea is very similar. And the results were disturbing. The probability of the canisters failing was about 28 percent. That’s an alarmingly high number.”

English says the public needs to know what the real numbers are for an accident like this and that rather than conducting another computer simulation like the one in 2007, Southern California Edison and the NRC should perform a physical test that is specific to the conditions at the San Onofre plant.

English admits this would likely lead to a further delay of loading the remaining 44 canisters into a longer-term underground storage. And leaving the cooling waste in short-term storage, as they are in now, creates a higher risk for a potential disaster caused by a fire, tsunami or even a terrorist attack.

Southern California Edison, the NRC, and others stakeholders generally agree that getting the radioactive materials out of the short-term storage or “cooling pools” is a priority.

When asked about the possibility of performing an updated physical test or computer simulation of what could happen if a nuclear waste canister is dropped, Mosher with Southern California Edison said, “Thank you for sharing the information from Dr. English. At this time, the NRC is conducting an inspection at San Onofre regarding the August 3 incident, and we are not commenting on the subject.”

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