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Waste Canister Incident At San Onofre Nuclear Plant Prompts Further Training

The site of spent nuclear fuel storage at the San Onofre nuclear power plant is shown in this photo, January 2018.
Southern California Edison
The site of spent nuclear fuel storage at the San Onofre nuclear power plant is shown in this photo, January 2018.

An incident last week involving a canister containing spent nuclear fuel at the San Onofre Nuclear Generating Station prompted the utility operating the station to direct additional training measures from the contractor in charge of transferring the fuel, it was reported Monday.

Southern California Edison officials said that "performance errors" by workers from contractor Holtec International resulted in a canister containing nuclear waste getting caught on an inner ring of what is called a Cavity Enclosure Container on one of the pads at a newly constructed storage site, The San Diego Union-Tribune reported.

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Since February, operators of the plant have been transferring canisters from what is called "wet storage" to a newly constructed facility on the site of the plant, which is in the process of being decommissioned. Those transfers have now been put on hold, Edison officials said.

"At no point during this incident was there a risk to employee or public safety, and immediate lessons learned have already been integrated into our process," Edison officials said in a statement.

The canister loaded by a crew from Holtec on Aug. 3 got wedged but a Southern California Edison oversight team discovered the canister was not sitting properly, Edison officials said. The canister was then re-positioned correctly and placed at the bottom of the enclosure.

Edison experienced a similar issue in March during the transfer of spent fuel at the plant, which holds 3.55 million pounds of spent fuel.

Work was delayed 10 days after workers discovered a piece of shim — a pin 4 inches by a half-inch — came loose while a canister was being loaded.

Holtec and an independent engineering firm assured Edison that the canister's integrity was sound, officials said.

Some 50 canisters of spent fuel sit in what is called a "dry storage" installation at the plant. A second dry storage installation, recently constructed and approved by the California Coastal Commission, is in the process of transferring 73 canisters from what is called "wet storage."

Spent fuel is thermally hot and to cool it, nuclear operators place the fuel in a metal rack and submerge it in a deep wet storage pool.